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In this study, a new magnetic solid phase extraction based on magnetic composite modified with biochar obtained from pumpkin peel was developed for the enrichment and extraction of Naproxen in lake water, tablet and urine samples. The effects of main parameters such as pH, extraction time, amount of adsorbent and sample volume, which affect magnetic solid phase extraction, were investigated. Under optimal conditions, intraday and interday precision values for naproxen were below 5.9, with accuracy (relative error) better than 7.0 %. The detection limit and preliminary concentration factor were 12 ng/mL and 10, respectively. The method proposed here can be used for routine analysis of naproxen in lake water, urine and tablets., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Portable near-infrared (NIR) spectrophotometers have emerged as valuable tools for identifying substandard and falsified pharmaceuticals (SFPs). Integration of these devices with chemometric and machine learning models enhances their ability to provide quantitative chemical insights. However, different NIR spectrophotometer models vary in resolution, sensitivity, and responses to environmental factors such as temperature and humidity, necessitating instrument-specific libraries that hinder the wider adoption of NIR technology. This study addresses these challenges and seeks to establish a robust approach to promote the use of NIR technology in post-market pharmaceutical analysis. We developed support vector machine and partial least squares regression models based on binary mixtures of lab-made ciprofloxacin and microcrystalline cellulose, then applied the models to ciprofloxacin dosage forms that were assayed with high performance liquid chromatography (HPLC). A receiver operating characteristic (ROC) analysis was performed to set spectrophotometer independent NIR metrics to evaluate ciprofloxacin dosage forms as "meets standard," "needs HPLC assay," or "fails standard." Over 200 ciprofloxacin tablets representing 50 different brands were evaluated using spectra acquired from three types of NIR spectrophotometer with 85% of the prediction agreeing with HPLC testing. This study shows that non-brand-specific predictive models can be applied across multiple spectrophotometers for rapid screening of the conformity of pharmaceutical active ingredients to regulatory standard., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Published by Elsevier B.V.)

Technical advances in the field of quality analysis allow an increasingly deeper look into the impurity profile of drugs. The ability to detect unexpected impurities in addition to known impurities ensures the supply of high-quality drugs and can prevent recalls due to the detection of harmful unexpected impurities, as has happened recently with the N-nitrosamine and azido impurities in losartan (LOS) drug products. In the present study, the LC-MS/HRMS approach described by Backer et al. was applied to an even more complex system, being the investigation of 35 LOS drug products and combination preparations purchased in 2018 and 2022 in German pharmacies. The film-coated tablets were analysed by means of four LC-MS/HRMS method variants. For the separation a Zorbax RR StableBond C18 column (3.0 ×100 mm, particle size of 3.5 µm, pore size of 80 Å), a gradient elution and for mass spectrometric detection a qTOF mass spectrometer with electrospray ionization in positive and negative mode was used. An information-dependent acquisition method was applied for the acquisition of high-resolution mass spectrometry data. The combination of an untargeted and a targeted screening approach revealed the finding of eight impurities in total. Beside the five LOS related compounds, LOS impurity F, J, K, L, M, and related compound D from amlodipine besilate, LOS azide and an unknown derivative thereof were detected. Identification and structure elucidation, respectively, were successfully performed using in silico fragmentation. Differences in the impurity profiles of drug products from 2018 and 2022 could be observed. This study shows that broad screening approaches like this are applicable to the analysis of drug products and can be an important enhancement of the quality assurance of medicinal products., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests. Laura Backer reports financial support was provided by Frankfurt Foundation Quality of Medicines. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper, (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

From the seed of Aesculus hippocastanum L., a complex mixture of triterpene saponin glycosides known as aescin was isolated, purified and characterized to be an active pharmaceutical ingredient for preparing of drug products. A reversed phase high performance liquid chromatographic method with UV detection was developed for the determination of total triterpene glycosides in enteric coated tablets containing aescin in a pattern-oriented manner. The mobile phase consisted of a mixture of acetonitrile and 0.1 % phosphoric acid solution (40: 60). UV detection was performed at 220 nm. The chromatographic column was Gemini C18 column, 5 µm 250 mm × 4.6 mm, which was maintained at 25 ◦C, connected with a precolumn (C18, 4.0 × 3.0 mm, 5 µm). The linear range was from 53.4 to 160.1 μg·mL -1 . The RSD of intra-and inter-day precision variations were less than 1 % and the mean recovery was (100.66 ± 0.49) % (RSD = 0.64 %). The method showed its suitability, simplicity, rapidity and precision. Accordingly, it was proven adequate for quality control of this herbal drug product either for registration with the regulartory authority or routine analysis., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier B.V.)

New degradation impurities at m/z 327.15 and m/z 311.16 using gradient UHPLC method with UV detection and highly selective QDa mass detection were observed during the ruxolitinib hydrobromide (RUX.HBr) : excipient binary mixture degradation study. High mass resolution LC-MS and nuclear magnetic resonance (NMR) techniques were employed to identify and fully characterize the degradation compounds. The degradation impurities were unambiguously identified as (R)-4-amino-6-(1-(2-cyano-1-cyclopentylethyl)-1H-pyrazol-4-yl)pyrimidine-5-carboxylic acid and (R)-3-(4-(6-amino-5-formylpyrimidin-4-yl)-1H-pyrazol-1-yl)-3-cyclopentylpropanenitrile and mechanism of their formation was proposed. It has been confirmed that the degradation products are formed in mixtures of RUX.HBr with some excipients in the presence of oxygen. Based on the forced degradation study, the chemically stable of pharmaceutical formulations were prepared to eliminate the formation of these impurities., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Cobalt content (as vitamin B 12 and inorganic cobalt) in two nutritional supplements, namely Spirulina platensis and Saccharomyces cerevisiae known as a "superfood", has been determined using inductively coupled plasma optical emission spectrometry (ICP-OES). Several sample pre-treatment protocols have been applied and compared. Microwave-assisted acid digestion efficiently decomposed all cobalt-containing compounds, thus allowed obtaining total cobalt content in supplements examined. Vitamin B 12 was extracted from the samples with acetate buffer and potassium cyanide solution exposed to mild microwave radiation for 30 min, and cyanocobalamin was separated from the extract by on-column solid phase extraction using C-18 modified silica bed. About 100% of cobalt species was extracted using the triple microwave-assisted extraction procedure. Total cobalt content was 20-fold greater in Spirulina tablets than the declared cobalamin content (as Co). The ICP-OES method precision was about 3% and detection limit was 1.9 and 2.7 ng Co mL -1 for inorganic cobalt or cyanocobalamin, respectively., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The objective was to present a hybrid approach to predict the strength-pressure relationship (SPR) of tablets using common compression parameters and a single measurement of tablet tensile strength. Experimental SPR were derived for six pharmaceutical powders with brittle and ductile properties and compared to predicted SPR based on a three-stage approach. The prediction was based on the Kawakita b -1 parameter and the in-die Heckel yield stress, an estimate of maximal tensile strength, and a parameter proportionality factor α. Three values of α were used to investigate the influence of the parameter on the SPR. The experimental SPR could satisfactorily be described by the three stage model, however for sodium bicarbonate the tensile strength plateau could not be observed experimentally. The shape of the predicted SPR was to a minor extent influenced by the Kawakita b -1 but the width of the linear region was highly influenced by α. An increased α increased the width of the linear region and thus also the maximal predicted tablet tensile strength. Furthermore, the correspondence between experimental and predicted SPR was influenced by the α value and satisfactory predictions were in general obtained for α = 4.1 indicating the predictive potential of the hybrid approach., (Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.)

A calibration model for in-line API quantification based on near infrared (NIR) spectra collection during tableting in the tablet press feed frame was developed and validated. First, the measurement set-up was optimised and the effect of filling degree of the feed frame on the NIR spectra was investigated. Secondly, a predictive API quantification model was developed and validated by calculating the accuracy profile based on the analysis results of validation experiments. Furthermore, based on the data of the accuracy profile, the measurement uncertainty was determined. Finally, the robustness of the API quantification model was evaluated. An NIR probe (SentroPAT FO) was implemented into the feed frame of a rotary tablet press (Modul™ P) to monitor physical mixtures of a model API (sodium saccharine) and excipients with two different API target concentrations: 5 and 20% (w/w). Cutting notches into the paddle wheel fingers did avoid disturbances of the NIR signal caused by the rotating paddle wheel fingers and hence allowed better and more complete feed frame monitoring. The effect of the design of the notched paddle wheel fingers was also investigated and elucidated that straight paddle wheel fingers did cause less variation in NIR signal compared to curved paddle wheel fingers. The filling degree of the feed frame was reflected in the raw NIR spectra. Several different calibration models for the prediction of the API content were developed, based on the use of single spectra or averaged spectra, and using partial least squares (PLS) regression or ratio models. These predictive models were then evaluated and validated by processing physical mixtures with different API concentrations not used in the calibration models (validation set). The β-expectation tolerance intervals were calculated for each model and for each of the validated API concentration levels (β was set at 95%). PLS models showed the best predictive performance. For each examined saccharine concentration range (i.e., between 4.5 and 6.5% and between 15 and 25%), at least 95% of future measurements will not deviate more than 15% from the true value., (Copyright © 2018 Elsevier B.V. All rights reserved.)

A system using energy-dispersive X-ray diffraction (EDXRD) has been developed and tested using multivariate calibration for the quantitative analysis of tablet-form mixtures of common pharmaceutical ingredients. A principal advantage of EDXRD over the more traditional and common angular dispersive X-ray diffraction technique (ADXRD) is the potential of EDXRD to analyse tablets within their packaging, due to the higher energy X-rays used. In the experiment, a series of caffeine, paracetamol and microcrystalline cellulose mixtures were prepared and pressed into tablets. EDXRD profiles were recorded on each sample and a principal component analysis (PCA) was carried out in both unpackaged and packaged scenarios. In both cases the first two principal components explained >98% of the between-sample variance. The PCA projected the sample profiles into two dimensional principal component space in close accordance to their ternary mixture design, demonstrating the discriminating potential of the EDXRD system. A partial least squares regression (PLSR) model was built with the samples and was validated using leave-one-out cross-validation. Low prediction errors of between 2% and 4% for both unpackaged and packaged tablets were obtained for all three chemical compounds. The prediction capability through packaging demonstrates a truly non-destructive method for quantifying tablet composition and demonstrates good potential for EDXRD to be applied in the field of counterfeit medicine screening and pharmaceutical quality control., (Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.)

A green, simple, accurate and highly sensitive sequential injection lab-at-valve procedure has been developed for the simultaneous determination of ascorbic acid (Asc) and rutin using 18-molybdo-2-phosphate Wells-Dawson heteropoly anion (18-MPA). The method is based on the dependence of the reaction rate between 18-MPA and reducing agents on the solution pH. Only Asc is capable of interacting with 18-MPA at pH 4.7, while at pH 7.4 the reaction with both Asc and rutin proceeds simultaneously. In order to improve the precision and sensitivity of the analysis, to minimize reagent consumption and to remove the Schlieren effect, the manifold for the sequential injection analysis was supplemented with external reaction chamber, and the reaction mixture was segmented. By the reduction of 18-MPA with reducing agents one- and two-electron heteropoly blues are formed. The fraction of one-electron heteropoly blue increases at low concentrations of the reducer. Measurement of the absorbance at a wavelength corresponding to the isobestic point allows strictly linear calibration graphs to be obtained. The calibration curves were linear in the concentration ranges of 0.3-24mgL -1 and 0.2-14mgL -1 with detection limits of 0.13mgL -1 and 0.09mgL -1 for rutin and Asc, respectively. The determination of rutin was possible in the presence of up to a 20-fold molar excess of Asc. The method was applied to the determination of Asc and rutin in ascorutin tablets with acceptable accuracy and precision (1-2%)., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The application of various techniques (FT-IR, PXRD, ssNMR) in the analysis of solid dosage forms with low concentration of an API (17-β-estradiol hemihydrate, EBHH) was tested. PXRD analysis of Estrofem Mite tablets (EMT) confirmed the presence of the main crystalline excipient, α-lactose monohydrate. In the PXRD pattern of EMT the strong background from polycrystalline excipients, i.e. hydroxypropylmethylcellulose and corn starch was observed. FT-IR spectra were characterized by the broad peaks in the 3000-3600cm -1 region of the OH stretching modes coming from multiple hydrogen bonds that are present in the structures of the excipients (α-lactose monohydrate, corn starch) and API. The only technique which unambiguously confirmed the presence of an API in the EMT was solid state NMR. Despite the tabletting process each of the EMT component retained its characteristic features like relaxation time and T 1ρ I . Due to the possibility of the manipulation in the experimental registration parameters like recycle delay (RD), evolution time (τ) and contact time (CT) it was possible to perform multiple experiments on the same sample of EMT. The most valuable were the inversion recovery CP experiments in which, by setting the proper values of τ, it was possible to selectively observe the signals of the chosen component of the drug formulation. In this study the great potential of solid state NMR in the analysis of solid dosage forms, as the unique technique that combines the possibility of selective observation of the chosen signals with the non destructive character that enables further analysis of the same sample, was confirmed., (Copyright © 2017 Elsevier B.V. All rights reserved.)

A simple, fast, sensitive and effective pass/fail field-friendly method has been developed for detecting sildenafil in suspect Viagra and unapproved tablets using handheld Raman spectrometers and silver colloids. The method involves dissolving a portion of a tablet in water followed by filtration and addition of silver colloids, resulting in a solution that can be measured directly through a glass vial. Over one hundred counterfeit Viagra and unapproved tablets were examined on three different devices during the method development phase of the study. While the pass/fail approach was found to be 92.6% effective on average, the efficacy increased to 97.4% on average when coupled with the software's "Discover Mode" feature that allows the user to compare a suspect spectrum to that of a stored sildenafil spectrum. The lowest concentration of sildenafil in a water/colloid solution that yielded a "Pass" was found to be 7.6μg/mL or 7.6 parts per million (ppm). For the analysis of suspect tablets, this value was found to be as low as 10μg/mL and as high as 625μg/mL. This variability was likely related to the tablet formulation, e.g., concentration of sildenafil, presence and concentration of water-soluble and/or water-insoluble ingredients. However, since most counterfeit Viagra and unapproved tablets contain >50mg sildenafil per tablet, such low concentrations will not be encountered often. Limited in-lab and in-field validation studies were conducted in which analysts/field agents followed the procedure outlined in this study for small sample sets. These individuals were provided with written instructions, a ∼20min demonstration regarding how to perform the procedure and use the instrument, and a kit with field-friendly supplies (purified bottled water from a local grocery store, disposable plastic pipettes, eye-dropper with a silver colloid solution, etc.). The method proved to be 98.3% and 91.7% effective for the in-lab and in-field validation studies, respectively, which demonstrated the ruggedness, simplicity and practicality of the method., (Published by Elsevier B.V.)

The aim of this study was to characterize the formation of emulsions by droplet size analysis and turbidimetry during reconstitution from a solid dosage form, namely from dry emulsion systems, which carry an oil phase for poorly soluble active ingredients. For the dry emulsion systems tablets were prepared either from oil-in-water systems using a freeze-drying process or through direct compression containing the same oil and excipients. The ratios of oil to emulgents and oil to xanthan gum were equal in both methods. In the preparation methods applied, mannitol, erythritol and lactose were used as excipients and mannitol was found to be the most effective excipient based on droplet size reconstitution, turbidimetry and physical properties. Quality control involved testing the physical properties of tablets and characterizing the reconstituted emulsions., (Copyright © 2016 Elsevier B.V. All rights reserved.)

A molecularly imprinted polymer (MIP) fiber on stainless steel wire using ciprofloxacin template with a mild template removal condition was synthetized and evaluated for fiber solid phase microextraction (SPME) of fluoroquinolones (FQs) from biological fluids and pharmaceutical samples, followed by high performance liquid chromatography analysis with UV detection (HPLC-UV). The developed MIP fiber exhibited high selectivity for the analytes in complex matrices. The coating of the fibers were inspected using fourier transform infrared spectrophotometry, thermogaravimetric analysis, energy dispersive X-ray (EDX) spectroscopy as well as by scanning electron microscopy (SEM). The fiber shows high thermal stability (up to 300°C), good reproducibility and long lifetime. The composite coating did not swell in organic solvents nor did it strip off from the substrate. It was also highly stable and extremely adherent to the surface of the stainless steel fiber. The fabricated fiber exclusively exhibited excellent extraction efficiency and selectivity for some FQs. The effective parameters influencing the microextraction efficiency such as pH, extraction time, desorption condition, and stirring rate were investigated. Under optimized conditions, the limits of detection of the four FQs ranged from 0.023-0.033 μg L(-1) (S/N=5) and the calibration graphs were linear in the concentration range from 0.1-40 μg L(-1), the inter-day and intraday relative standard deviations (RSD) for various FQs at three different concentration level (n=5) using a single fiber were 1.1-4.4% and the fiber to fiber RSD% (n=5) was 4.3-6.7% at 5 μg L(-1) of each anlyetes. The method was successfully applied for quantification of FQs in real samples including serum, plasma and tablet formulation with the recoveries between 97 to 102%., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Domperidone and Itopride are pro-kinetic agents, regulating the gastric motility and are commonly prescribed as anti emetic drugs. In the present study a simple, rapid and sensitive RP-HPLC/UV method was developed for simultaneous determination of Domperidone and Itopride in pharmaceutical samples and human plasma, using Tenofavir as internal standard. Experimental conditions were optimized and method was validated according to the standard guidelines. Combination of water (pH 3.0) and acetonitrile (65:35 v/v) was used as mobile phase, pumped at the flow rate of 1.5 ml/min. Detector wavelength was set at 210 nm and column oven temperature was 40oC. Unlike conventional liquid-liquid extraction, simple precipitation technique was applied for drug extraction from human plasma using acetonitrile for deprotienation. The method showed adequate separation of both the analytes and best resolution was achieved using Hypersil BDS C8 column (150 mm × 4.6 mm, 5 μm). The method was quite linear in the range of 20-600 ng/ml. Recovery of the method was 92.31% and 89.82% for Domperidone and Itopride, respectively. Retention time of both the analytes and internal standard was below 15 min. The lower limit of detection (LLOD) and lower limit of quantification (LLOQ) for Domperidone were 5 and 10 ng/ml while for Itopride was 12 and 15 ng/ml, respectively. The developed method was successfully applied for in-vivo analysis of fast dispersible tablets of Domperidone in healthy human volunteer. The proposed method was a part of formulation development study and was efficiently applied for determination of the two drugs in various pharmaceutical products and human plasma., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Counterfeit drugs are a major threat to public health. Current efforts focus on serialization of the secondary packaging which do not allow to trace the individual unit. As a proof of concept, we intended to mark each tablet for its unambiguous recognition. Spiking monodisperse PEGs into tablet coating solutions at concentrations as low as 3 ppm was instrumental to "write" a code into each tablet film which was readily read upon isolation and LC-MS/MS analysis. Different qualities and amounts of monodisperse polyethylene glycols can be used for coding solid drug products. The approach is limited to cases in which PEGs are not present for formulation purposes as excipients, as coding against this background was unfeasible., (Copyright © 2015 Elsevier B.V. All rights reserved.)

This study describes how the strain on formulation components affects dissolution and how near infrared spectroscopy can be used to predict dissolution. Strain (exposure to shear stress) applied during powder mixing affects the interaction between formulation components. Particles experience shear strain when they move relative to each other in a process affecting the properties of the final product. This stress affects the dissolution of oral solid dosages forms. However, dissolution testing destroys the entire tablet, making it impossible to further evaluate tablet properties when an out of specification result is obtained. Thus, a nondestructive technique such as near infrared spectroscopy is desirable to predict dissolution. The aim of this study was to predict dissolution on tablets with different levels of strain (shear) using near infrared spectroscopy in combination with multivariate data analysis. Shear was induced using a modified Couette cell on the powder mixture and tablets from these mixtures were produced using a tablet press emulator. Tablets produced with different strain levels were measured using near infrared spectroscopy. Spectra were obtained in diffuse reflectance mode and pretreated with baseline correction to maintain the physical and chemical information of the tablets. Dissolution profiles were obtained using USP Apparatus 2 as a reference method. Principal component analysis was used to study the sources of variation in the spectra obtained. Partial least squares 2 was used to predict dissolution on tablets with different levels of strain.

Two chromatgraphic methods were developed for determination of Paracetamol (PCM) and Pamabrom (PAM) in presence of P-aminophenol (PAP) and Theophylline (THEO) as potential impurities of both drugs respectively. First method is HPTLC which depends on separation and quantitation of the studied drugs on aluminum plates pre-coated with silica gel 60 F₂₅₄ as a stationary phase using chloroform:methanol:ethyl acetate:glacial acetic acid (8:0.8:0.6:0.2, v/v/v/v) as mobile phase followed by densitometric measurement of the bands at 254 nm. Second method is RP-HPLC which comprises separation of the studied drugs on a Phenomenex C8 column by gradient elution using mobile phase consisting of sodium dihydrogen phosphate buffer (0.05 M): methanol:acetonitrile (85:10:5, v/v/v) at a flow rate of 1 mL/min for first 7.5 min and (70:20:10, v/v/v) at a flow rate of 1.5 mL/min for the next 5 min. The proposed methods were successfully applied for determination of the potential impurities of PCM and PAM after resolving them from the pure drugs. The developed methods have been validated and proved to meet the requirements delineated by ICH guidelines with respect to linearity, accuracy, precision, specificity and robustness. The validated methods were successfully applied for determination of the studied drugs in their pharmaceutical formulation. The results were statistically compared to those obtained by the reported RP-HPLC method where no significant difference was found; indicating the ability of proposed methods to be used for routine quality control analysis of these drugs., (Copyright © 2015 Elsevier B.V. All rights reserved.)

In the last decade, counterfeit pharmaceutical products have become a widespread issue for public health. Raman spectroscopy which is easy, non-destructive and information-rich is particularly suitable as screening method for fast characterization of chemicals and pharmaceuticals. Combined with chemometric techniques, it provides a powerful tool for the analysis and determination of counterfeit medicines. Here, for the first time, a systematic study of the benefits and limitations of Raman spectroscopy for the analysis of pharmaceutical samples on a large set of model tablets, varying with respect to chemical and physical properties, was performed. To discriminate between the different mixtures, a combination of dispersive Raman spectroscopy performing in backscattering mode and principal component analysis was used. The discrimination between samples with different coatings, a varying amount of active pharmaceutical ingredients and a diversity of excipients were possible. However, it was not possible to distinguish between variations of the press power, mixing quality and granulation. As a showcase, the change in Raman signals of commercial acetylsalicylic acid effervescent tablets due to five different storage conditions was monitored. It was possible to detect early small chemical changes caused by inappropriate storage conditions. These results demonstrate that Raman spectroscopy combined with multivariate data analysis provides a powerful methodology for the fast and easy characterization of genuine and counterfeit medicines., (Copyright © 2015 Elsevier B.V. All rights reserved.)

During drug product development, the nature and distribution of the active substance have to be controlled to ensure the correct activity and the safety of the final medication. Matrix assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI), due to its structural and spatial specificities, provides an excellent way to analyze these two critical parameters in the same acquisition. The aim of this work is to demonstrate that MALDI-MSI, coupled with four well known multivariate statistical analysis algorithms (PCA, ICA, MCR-ALS and NMF), is a powerful technique to extract spatial and spectral information about chemical compounds from known or unknown solid drug product formulations. To test this methodology, an in-house manufactured tablet and a commercialized Coversyl(®) tablet were studied. The statistical analysis was decomposed into three steps: preprocessing, estimation of the number of statistical components (manually or using singular value decomposition), and multivariate statistical analysis. The results obtained showed that while principal component analysis (PCA) was efficient in searching for sources of variation in the matrix, it was not the best technique to estimate an unmixing model of a tablet. Independent component analysis (ICA) was able to extract appropriate contributions of chemical information in homogeneous and heterogeneous datasets. Non-negative matrix factorization (NMF) and multivariate curve resolution-alternating least squares (MCR-ALS) were less accurate in obtaining the right contribution in a homogeneous sample but they were better at distinguishing the semi-quantitative information in a heterogeneous MALDI dataset., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Misoprostol is a synthetic prostaglandin E1 analogue which is mainly used for prevention and treatment of gastric ulcers, but also for abortion due to its labour inducing effect. Misoprostol exists as a mixture of diastereoisomers (1:1) and has several related impurities owing to its instability at higher temperatures and moisture. A simple and robust reversed phase liquid chromatographic (RPLC) method is described for the separation of the related substances and a normal phase (NP) LC method for the separation of misoprostol diastereoisomers. The RPLC method was performed using an Ascentis Express C18 (150 mm × 4.6 mm, 5 μm) column kept at 35 °C. The mobile phase was a gradient mixture of mobile phase A (ACN-H2O-MeOH, 28:69:3 v/v/v) and mobile phase B (ACN-H2O-MeOH, 47:50:3 v/v/v) eluted at a flow rate of 1.5 mL/min. UV detection was performed at 200 nm. The NPLC method was undertaken by using an XBridge bare silica (150 mm × 2.1 mm, 3.5 μm) column at 35 °C. The mobile phase contained 1-propanol-heptane-TFA (4:96:0.1%, v/v/v), pumped at a flow rate of 0.5 mL/min. UV detection was performed at 205 nm. This LC method can properly separate the two diastereoisomers (Rs > 2) within an analysis time of less than 20 min. Both methods were validated according to the ICH guidelines. Furthermore, these new LC methods have been successfully applied for purity control and diastereoisomers ratio determination of misoprostol bulk drug, tablets and dispersion., (Copyright © 2015 Elsevier B.V. All rights reserved.)

A stability indicating-micellar electrokinetic chromatography method was developed and validated for the determination of gliclazide (GCZ) and its specified impurities, gliclazide impurities B (GZB) and F (GZF) in bulk and tablets. The analytes were well separated (Rs>2.1) in 5 min using 10mM phosphate buffer (pH 7.0) containing 15 mM sodium dodecyl sulfate on a fused-silica capillary with an effective length of 40 cm and an inner diameter of 50 μm, injection at 50 mbar for 5s, temperature of 25°C, applied voltage of 20 kV and photodiode array detection at 225 nm. The method showed good linearity (r(2)>0.99, in the ranges of 128-192, 20-60 and 10-50 μg/mL for GCZ, GZB and GZF, respectively) and precision (%RSD for intra- and inter-day precision of less than 2.00%, n=3) for all compounds. Accuracy represented as %recovery was between 99.1 and 100.1% with %RSDs of less than 0.59% (n=3). Limits of detection and quantitation were less than 40 and 120 μg/mL, respectively. The method was robust with %RSDs of migration time and peak areas of less than 1.36% (n=9), when buffer and separating voltage were altered around the optimal values. Stress tests showed that GCZ was stable in alkaline hydrolysis both at room and elevated temperature. However, GCZ degraded under acid and neutral hydrolysis and oxidation condition. Elevated temperature and exposure to sunlight accelerated GCZ degradation and formation of GZB and an unknown degradation product. Stability profiles and degradation kinetics of GCZ could be established using the MEKC method. In addition, the method could be used for assay of GCZ in raw material and commercial tablets and results revealed that contents of GCZ in all samples were within the pharmacopeia limit. No degradation products, especially GZB and GZF, were observed in the investigated samples., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Since near infrared spectroscopy (NIRS) was introduced to the pharmaceutical industry, efforts have been spent to leverage the power of chemometrics to extract out the best possible signal to correlate with the analyte of the interest. In contrast, only a few studies addressed the potential impact of instrument parameters, such as resolution and co-adds (i.e., the number of averaged replicate spectra), on the method performance of error statistics. In this study, a holistic approach was used to evaluate the effect of the instrument parameters of a FT-NIR spectrometer on the performance of a content uniformity method with respect to a list of figures of merit. The figures of merit included error statistics, signal-to-noise ratio (S/N), sensitivity, analytical sensitivity, effective resolution, selectivity, limit of detection (LOD), and noise. A Bruker MPA FT-NIR spectrometer was used for the investigation of an experimental design in terms of resolution (4 cm(-1) and 32 cm(-1)) and co-adds (256 and 16) plus a center point at 8 cm(-1) and 32 co-adds. Given the balance among underlying chemistry, instrument parameters, chemometrics, and measurement time, 8 cm(-1) and 32 co-adds in combination with appropriate 2nd derivative preprocessing was found to fit best for the intended purpose as a content uniformity method. The considerations for optimizing both instrument parameters and chemometrics were proposed and discussed in order to maximize the method performance for its intended purpose for future NIRS method development in R&D., (Copyright © 2014 Elsevier B.V. All rights reserved.)

The detection and quantification of alternate polymorphs of active pharmaceutical ingredients (APIs), particularly at low concentrations is a key issue for the manufacture and analysis of solid-state formulations. Each polymorph can possess unique physical and chemical properties which in turn can directly affect factors such as solubility and bioavailability. Near infra-red (NIR) and Raman spectroscopies can be used for the rapid characterisation and quantification of polymorphs in solid samples. In this study we have generated a model tablet system with two excipients and a 10% API concentration, where the API is a mixture of the FII and FIII polymorphs of piracetam. Using transmission Raman spectroscopy (TRS) and NIR spectroscopy it was possible to detect FII polymorph contamination in these model tablets with limits of detection (LODs) of 0.6 and 0.7%, respectively, with respect to the total tablet weight (or ∼6-7% of the API content). The TRS method is the superior method because of the speed of analysis (∼6s per sample), better sampling statistics, and because the sharper, more resolved bands in the Raman spectra allowed for easier interpretation of the spectral data. In addition the TRS used here provides facile access to the low frequency wavenumber region for analysis of solid-state lattice modes., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Risk analysis is a valuable addition to validation of an analytical chemistry process, enabling not only detecting technical risks, but also risks related to human failures. Failure Mode and Effect Analysis (FMEA) can be applied, using a categorical risk scoring of the occurrence, detection and severity of failure modes, and calculating the Risk Priority Number (RPN) to select failure modes for correction. We propose a probabilistic modification of FMEA, replacing the categorical scoring of occurrence and detection by their estimated relative frequency and maintaining the categorical scoring of severity. In an example, the results of traditional FMEA of a Near Infrared (NIR) analytical procedure used for the screening of suspected counterfeited tablets are re-interpretated by this probabilistic modification of FMEA. Using this probabilistic modification of FMEA, the frequency of occurrence of undetected failure mode(s) can be estimated quantitatively, for each individual failure mode, for a set of failure modes, and the full analytical procedure., (Copyright © 2012 Elsevier B.V. All rights reserved.)

A novel, simple and rapid capillary zone electrophoresis method with UV detection has been developed for the simultaneous determination of pyrimethamine and sulfadoxine in tablet formulations. The compounds are separated in 6 min in a fused silica capillary, 30 cm long (20 cm to detector)× 50 μm using a 100 mM phosphate buffer pH 7.2 as background electrolyte, a 330 V cm(-1) electric field and a detection wavelength of 214 nm. Analysis of different tablet formulations has shown a good agreement with the liquid chromatography method described in the United States Pharmacopoeia. Main advantages of the CZE method are the rapid set-up of instrumentation and capillary equilibration, short analysis time and low running cost., (Copyright © 2011 Elsevier B.V. All rights reserved.)

A simple and rapid reversed phase liquid chromatographic method for separation and determination of the related substances of telmisartan (TLM) was developed and validated. The chromatographic separation was achieved on Lichrospher RP-18 column (250 × 4.6 mm, 5 μm), using 20 mM ammonium acetate containing 0.1% (v/v) triethylamine (pH adjusted to 3.0 with trifluoroacetic acid) and acetonitrile as mobile phase at 25°C. The detection was performed at 254 nm. The method was validated and found to be robust, precise, specific and linear between 0.37 and 500 μg/mL. The limits of detection and quantification of telmisartan were 0.11 and 0.37 μg/mL, respectively. The method was successfully applied to quantify related substances and assay of TLM in bulk drugs and commercial tablets. The related substances relate to a novel synthetic route and different from those A-H impurities reported by European Pharmacopeia., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Simultaneous determination of aniracetam and its related impurities (2-pyrrolidinone, p-anisic acid, 4-p-anisamidobutyric acid and (p-anisoyl)-4-methyl-2-pyrrolidinone) was accomplished in the bulk drug and in a tablet formulation using a high performance liquid chromatographic method with UV detection. Separation was achieved on a Hypersil BDS-CN column (150 mm × 4.0 mm, 5 μm) using a gradient elution program with solvent A composed of phosphate buffer (pH 4.0; 0.010 M) and solvent B of acetonitrile-phosphate buffer (pH 4.0; 0.010 M) (90:10, v/v). The flow rate of the mobile phase was 1.0 mL min(-1) and the total elution time, including the column re-equilibration, was approximately 20 min. The UV detection wavelength was varied appropriately among 210, 250 and 280 nm. Injection volume was 20 μL and experiments were conducted at ambient temperature. The developed method was validated in terms of system suitability, selectivity, linearity, range, precision, accuracy, limits of detection and quantification for the impurities, short term and long term stability of the analytes in the prepared solutions and robustness, following the ICH guidelines. Therefore, the proposed method was suitable for the simultaneous determination of aniracetam and its studied related impurities., (Copyright © 2011 Elsevier B.V. All rights reserved.)

This paper presents the development and validation of an improved method for the simultaneous analysis of lamivudine (LVD), stavudine (STV) and nevirapine (NVP) using high-performance thin-layer chromatography (HPTLC) with densitometric detection. Separation was performed on silica gel 60F(254) plates. The mobile phase is comprised of ethylacetate, methanol, toluene and concentrated ammonia (38.7:19.4:38.7:3.2, v:v:v:v). Detection wavelength was 254 nm. The R(f) values were 0.24±0.03, 0.38±0.04 and 0.69±0.04 (n=8) for LVD, STV and NVP, respectively. An F-test indicated that calibration graphs were adequately linear at the evaluated concentration ranges. The pooled %RSD for repeatability of the percentage amount recovered for LVD, STV and NVP were found to be 0.62, 0.54, and 0.79, and the pooled %RSD for time-different intermediate precision were 1.66, 1.27 and 1.21. The percentage recoveries for the trueness were 99.2%±1.5 for LVD, 98.6%±1.5 for STV and 99.3%±1.7 for NVP (n=3). Most factors evaluated in the robustness test were found to have an insignificant effect on the selected responses at 95% confidence level. This method was successfully used to analyze fixed-dose tablets samples of LVD, STV and NVP., (Copyright © 2010 Elsevier B.V. All rights reserved.)

A near infrared (NIR) method was developed for determination of tablet potency of active pharmaceutical ingredient (API) in a complex coated tablet matrix. The calibration set contained samples from laboratory and production scale batches. The reference values were obtained by high performance liquid chromatography (HPLC) and partial least squares (PLS) regression was used to establish a model. The model was challenged by calculating tablet potency of two external test sets. Root mean square errors of prediction were respectively equal to 2.0% and 2.7%. To use this model with a second spectrometer from the production field, a calibration transfer method called piecewise direct standardisation (PDS) was used. After the transfer, the root mean square error of prediction of the first test set was 2.4% compared to 4.0% without transferring the spectra. A statistical technique using bootstrap of PLS residuals was used to estimate confidence intervals of tablet potency calculations. This method requires an optimised PLS model, selection of the bootstrap number and determination of the risk. In the case of a chemical analysis, the tablet potency value will be included within the confidence interval calculated by the bootstrap method. An easy to use graphical interface was developed to easily determine if the predictions, surrounded by minimum and maximum values, are within the specifications defined by the regulatory organisation., (Copyright © 2010 Elsevier B.V. All rights reserved.)

A multivariate model was constructed by correlating Raman spectral data with coated amount of the API diprophylline using Partial Least Squares. In agreement with ICH guideline Q2 the method was validated in order to achieve the requirement of demonstrating that Raman spectroscopy is suitable as rapid PAT tool for inline quantitative monitoring of active coating. The present work presents an appropriate approach to transfer the requirements of the guidelines to the Raman method used for inline measurements and demonstrates that the requirements of the validation characteristics were achieved., (Copyright (c) 2010 Elsevier B.V. All rights reserved.)

The growth of pharmaceutical counterfeiting is a major public health problem. This growth is resulting in a proportional increase in the number of samples that medicines control laboratories have to test. Thus the need for simple and affordable preliminary screening methods to be used by inspectors to decide in the field whether to collect a sample for further laboratory analysis or not. This paper intends to evaluate the possibility to employ for preliminary examinations of suspicious samples an optical spectrophotometer (colorimeter) used in the graphic industry, capable of measuring the reflectance visible spectrum of solid materials. The colorimeter was tested on original and counterfeited Viagra, Cialis and Levitra by measuring the colour of tablets' surface and of a specific spot of the packages. Various batches of the original drugs were employed both to investigate precision and robustness of the technique and to build spectral libraries. These libraries were used to compare suspicious samples to the corresponding original by means of a wavelength distance pattern recognition method. The method was eventually tested on suspicious samples sized by police authorities in order to evaluate its effectiveness. The device resulted precise and robust toward ambient conditions changes, although some limits emerged: the libraries of original samples need a frequent update and a lower precision is to be expected for tablets which surface is extremely convex.

The FT-Raman quantification of atorvastatin calcium in tablets was performed using the partial least squares (PLS), principal component regression (PCR) and counter-propagation artificial neural networks (CP-ANN) methods. To compare the predictive abilities of the elaborated models, the relative standard errors of prediction (RSEP) were calculated. The application of PLS, PCR and 6x6 CP-ANN provided models of comparable quality. RSEP error values in the range of 1.9-2.8% for calibration and validation data sets were obtained for the three procedures applied. Four commercial products containing 10, 20 or 40 mg of atorvastatin calcium per tablet were successfully quantified. Concentrations found from the Raman data analysis correlate strongly with the declared values, with a recovery of 98.5-101.3%, and with the results of reference analysis, with the recovery of 98.9-102.1%, for the different models. The proposed procedure can be a fast, precise and convenient method of atorvastatin calcium quantification in commercial tablets.

A rapid and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method has been developed and validated for simultaneous quantification of Tenofovir (TEN) and Emtricitabine (EMT) in human plasma using Chromolith Speed Rod RP18. The mass transition ion-pair has been followed as m/z 288.10-->176.10 for TEN, m/z 248.20-->130.20 for EMT and m/z 230.10-->112.10 for Lamivudine (LAM). The method involves solid phase extraction from plasma, simple isocratic chromatographic conditions and mass spectrometric detection using an API 5000 instrument that enables detection at nanogram levels. Lamivudine was used as the internal standard. The proposed method has been validated with a linear range of 10-600 ng/ml for TEN and 25-2,500 ng/ml for EMT. The intrarun and interrun precision values are within 12.0% for TEN and 15.6% for EMT at their respective LOQ levels. The overall recoveries for TEN and EMT were 84.3% and 68.5%, respectively. Total elution time was as low as 2 min.

The FT-Raman quantification of diclofenac sodium in tablets and capsules was performed with the help of the partial least squares (PLS), principal component regression (PCR) and counter-propagation artificial neural networks (CP-ANN) methods. For the analysed tablets, calibration models were built using unnormalised spectra and spectra normalised by the intensity of a selected band of an internal standard. Different pre-processing methods were applied for the capsules. To compare the predictive ability of the models, the relative standard errors of prediction (RSEP) were calculated. The 5 x 5 CP-ANN and PLS methods gave models of comparable quality, which were usually more efficient than the PCR ones. The RSEP error values for the tablets were in the range of 2.4-3.8% for the calibration and 2.6-3.5% for the validation data sets and for the three procedures applied. For capsules, the RSEP errors were in the range of 0.8-1.9% and 1.4-1.7% for the calibration and validation samples, respectively. Five commercial products containing 25, 50 or 75 mg of diclofenac sodium per tablet/capsule were quantified. Concentrations found from the Raman data analysis agree with the results of the reference analysis and correlate strongly with the declared values with the recovery of 99.5-101.3%, 99.7-102.0% and 99.9-101.2% for the PLS, PCR and CP-ANN methods, respectively. The proposed procedure can be a fast and convenient alternative to the standard pharmacopoeial methods of diclofenac sodium quantification in solid dosage forms.

A method for the specific determination of an antibacterial quaternary ammonium compound Dequalinium chloride (DQC) was described in this paper. At pH 0.5, the resonance light scattering (RLS) intensity of sodium dodecyl benzene sulfonate (SDBS) remarkably was enhanced by adding DQC. A RLS peak at 392.0 nm was found, and the enhanced intensity of RLS at this wavelength was proportional to the concentration of DQC in the range of 0.096-2.88 microg/mL. The detection limit was 2.98 ng/mL and the correlation coefficient was r=0.9988 (n=9). The method was applied to the analysis of DQC in lozenges and human serum. The results indicated that the method was sensitive, simple, practical and useful in the clinical assay.

This paper describes the development and validation of a HPLC-UV method (210 nm) for the simultaneous quantitation of artemether and lumefantrine in fixed dose combination tablets. The method showed to be linear (r(2)>0.99), precise (R.S.D.<2.0%), accurate (recovery of 101.07% for artemether and 101.58% for lumefantrine), specific and robust. Four batches of artemether-lumefantrine tablets were assayed by the validated method. The artemether contents in the tablets varied from 98.61% to 103.35%, while lumefantrine contents were 97.92-100.48%.

A rapid, simple and sensitive LC-MS/MS method was developed for simultaneous determination of amoxicillin and ambroxol in human plasma using clenbuterol as internal standard (IS). The plasma samples were subjected to a simple protein precipitation with methanol. Separation was achieved on a Lichrospher C(18) column (150 mm x 4.6mm ID, dp 5 microm) using methanol (containing 0.2% of formic acid) and water (containing 0.2% of formic acid) as a mobile phase by gradient elution at a flow rate of 1.0 mL/min. Detection was performed using electrospray ionization in positive ion multiple reaction monitoring (MRM) mode by monitoring the ion transitions from m/z 365.9-->348.9 (amoxicillin), m/z 378.9-->263.6 (ambroxol) and m/z 277.0-->203.0 (IS). Calibration curves were linear in the concentration range of 5-20,000 ng/mL for amoxicillin, and 1-200 ng/mL for ambroxol, with the intra- and inter-run precisions of <9% and the accuracies of 100+/-7%. The method has been validated and applied to pharmacokinetic studies of compound amoxicillin and ambroxol hydrochloride tablets in healthy Chinese volunteers.

Near-infrared chemical imaging (NIR-CI) is the fusion of near-infrared spectroscopy and image analysis. It can be used to visualize the spatial distribution of the chemical compounds in a sample (providing a chemical image). Each sample measurement generates a hyperspectral data cube containing thousands of spectra. An important part of a NIR-CI analysis is the data processing of the hyperspectral data cube. The aim of this study was to compare the ability of different commonly used calibration methods to generate accurate chemical images. Three common calibration approaches were compared: (1) using single wavenumber, (2) using classical least squares regression (CLS) and (3) using partial least squares regression (PLS1). Each method was evaluated using two different preprocessing methods. A calibration data set of tablets with five constituents was used for analysis. Chemical images of the active pharmaceutical ingredient (API) and the two major excipients cellulose and lactose in the formulation were made. The accuracy of the generated chemical images was evaluated by the concentration prediction ability. The most accurate predictions for all three compounds were generated by PLS1. The drawback of PLS1 is that it requires a calibration data set and CLS, which does not require a calibration data set, therefore proved to be an excellent alternative. CLS also generated accurate predictions and only requires the pure compound spectrum of each constituent in the sample. All three calibration approaches were found applicable for hyperspectral image analysis but their relevance of use depends on the purpose of analysis and type of data set. As expected, the single wavenumber method was primarily found useful for compounds with a distinct spectral band that was not overlapped by bands of other constituents. This paper also provides guidance for hyperspectral image (or NIR-CI) analysis describing each of the typical steps involved.

The BFR (Basis Function Regression) is an interesting alternative to common techniques (such as PCR or PLS) in chemometrics. It is based on projecting the spectral information onto some number of equally spaced spline bases, than obtaining integrals of resulted curves. Existing references show that in certain cases it can reduce almost twice the RMSEP values. As this technique is not so popular in chemometrics nor applied in pharmaceutical analysis, it is desirable to present its theoretical considerations and implementation (with example MATLAB/Octave code). As an illustrative example we present the chemometric model for content recognition of a tablet (12 possible compounds in binary or ternary combinations) from the UV spectrum of its methanolic extract. The BFR technique gave lowest prediction error and the estimators obtained have more meritorical meaning than in case of PCR, PLS and other techniques used for comparison. In our opinion this technique should be considered in any chemometric approach as it often shows better performance.

An alternative method for the determination of fexofenadine (FEX) and pseudoephedrine (PSE) in their combined tablet formulation has been developed, employing the partial least squares (PLS) analysis of spectral data of the analytes in their pharmaceutical association. A full-factorially designed set of 16 synthetic samples was employed for calibration purposes. The calibration models were constructed with wavelengths selection, in the ultraviolet region, according to their predictive ability. These were validated internally by the leave-one-out procedure and externally, employing appropriate sets of validation samples. The described method was linear for both analytes, over the range 160.6-301.2 mg L(-1) for FEX (R(2)=0.9993) and between 325.6 and 610.5 mg L(-1) for PSE (R(2)=0.9992). It was accurate, exhibiting 99.8% and 99.9% drug recoveries for FEX and PSE, respectively (N=9), while in the intermediate precision experiment relative standard deviations were 1.4% for FEX and 1.2% for PSE. The contents of both analytes were assayed in commercial tablets employing this method and the results were compared with those furnished by HPLC, being in good statistical agreement. The method represents an improvement over the first derivative of spectral ratio (DSR) technique and allows high sample throughput with minimum reagent consumption and waste generation. The obtained results confirm that the method is highly suitable for its intended purpose.

The objective of this study was to control the purity of 16 commercial formulations of ciprofloxacin tablets purchased in different countries or via the Internet using 19F and 1H nuclear magnetic resonance (NMR). Twelve out of the sixteen commercial formulations of ciprofloxacin measured by 19F NMR contain the active ingredient within 100+/-5% of stated concentration. Three formulations have a lower ciprofloxacin content between 90 and 95% and one shows a higher concentration superior to 105%. The impurity profile was characterised using 19F and 1H NMR, and is characteristic of the manufacturer. Four to twelve fluorinated impurities among them fluoride ion and two already known compounds were detected and quantified in the sixteen formulations analysed by 19F NMR. Two other non-fluorinated impurities were observed in the seven formulations analysed with 1H NMR. The total content of impurities as well as their individual levels are in agreement with those reported previously in the few studies devoted to ciprofloxacin purity. However, all the formulations do not comply with the limits for impurities given in the ciprofloxacin monograph of the European Pharmacopeia. Finally, a "signature" of the formulations was obtained with Diffusion-Ordered SpectroscopY (DOSY) 1H NMR which allowed the characterisation of some excipients present in the formulations studied.

The electrochemical behavior of piroxicam on a multi-walled carbon nanotubes electrode for the first time was investigated. A highly sensitive and fast responding sensor for determination of piroxicam was simply and conveniently fabricated. The constructed electrode exhibits efficiently catalytic activity for the electrooxidation of piroxicam at a reduced over potential with high sensitivity, stability, and long lifetime in the wide concentration rang of piroxicam. The oxidation process was found to be dependent on the pH of the supporting electrolyte. The behavior is further exploited as a sensitive detection method for piroxicam determination by differential pulse voltammetry. Under the optimized conditions the calibration plots are linear in the concentration range of 0.15-5 microg ml(-1). Application of the method for the determination of the drug in the dosage form (Feledene capsules and tablets and also piroxicam gel), without any interference, from the excipients, resulted in acceptable deviation from the stated concentrations. Recoveries were obtained in the range 96.35-104.16%. The detection limit of 0.1 microg ml(-1) was obtained for piroxicam determination.

Three coated wire electrodes (CWEs) for the antispasmodic drugs; dicyclomine (Dc), mebeverine (Mv) and drotaverine (Dv) hydrochlorides were developed. Each electrode based on ion-associate of a heteropoly anion with the drug cation incorporated in membrane sensor modified with graphite and deposited on silver internal solid contact. The influence of addition of graphite to the membranes and the type of the internal solid contact on the potentiometric responses of the electrodes was investigated. The characteristics of the new electrodes were compared to the characteristics of previously reported traditional liquid inner contact electrodes of the same drugs. The lower detection limits of the proposed electrodes were somewhat better than those observed with the corresponding liquid contact ISEs and reached (1.2-2.0)x10(-7)M. The potentiometric selectivity of the CWEs revealed a significant improvement and much faster response times compared to the liquid contact ISEs. The practical utility of each electrode has been demonstrated by using it successfully in potentiometric determination of its respective drug in pharmaceutical preparations both in batch and flow injection conditions. Each electrode was also used as an indicator electrode in the potentiometric titration of the drug against standard silicotungstic acid and in potentiometric determination of the drug concentration in urine samples.

The kinetic H-point standard addition method (HPSAM) was applied to the simultaneous determination of levodopa and carbidopa. The method was based on the difference in the rate of oxidation of these compounds with Cu(II)-neocuproine system and formation of Cu(I)-neocuproine complex at pH 5.5. The absorbance of the Cu(I)-neocuproine complex was monitored at 453 nm. Experimental conditions such as pH, reagent concentrations, ionic strength and temperature were optimized. Simultaneous determination of levodopa and carbidopa was performed in the range of 0.8-4 and 0.2-1.5 microg ml(-1), respectively. The proposed method was applied to the simultaneous determination of levodopa and carbidopa in pharmaceutical samples, and satisfactory results were obtained.

19F nuclear magnetic resonance was used as a suitable analytical tool for the identification and selective determination of haloperidol in human serum and pharmaceutical preparations. The method is based on the integration of appropriate signals of haloperidol and trifluoroacetic acid as an internal standard. The proposed method is a rapid and facile, while without any sample pretreatment, manipulation of large samples and lengthy instrument time. The regression equation for haloperidol in human serum showed a good linearity in the range of 60-600 microg ml(-1) with a detection limit of 1.4 microg ml(-1). The mean recovery results on human serum samples ranged from about 96-103%, with relative standard deviations <8%. The method was also applied successfully to the determination of haloperidol in real pharmaceutical samples, and compared with the results obtained by a reference method. The drug's degradation was studied by the proposed method in hydrochloric acid media and main products were identified.

Raman spectra of a set of coated pharmaceutical tablets were analyzed for the purpose of calibrating the spectra to tablet coating thickness. Acetaminophen tablets were coated with a hydroxypropylmethylcellulose/polyethylene glycol film coating whose thickness was varied from 0 to 6% weight gain. Coatings were also prepared with two concentrations of TiO2 at several film thicknesses. The resulting spectral data set was analyzed using several different multivariate calibration procedures. The procedures examined in this study included spectral correction followed by target factor analysis, spectral correction with baseline subtraction followed by principal component regression, and first derivative computation followed by principal component regression. The results demonstrate that target factor analysis is a viable method for calibration of Raman spectra to tablet coating thickness. Calibration based on derivative spectra resulted in linear correlation that was equal to that of the results of target factor analysis for coatings without TiO2. However, target factor analysis was found to be superior to other methods when TiO2 was present in the tablet coatings. The effect of sample fluorescence on each of these chemometric methods was also examined. It was found that when photobleaching of fluorescent impurities due to exposure to the Raman excitation source was controlled, the tablet coating thickness could be calibrated to the intensity of the fluorescence signal. The results also demonstrate that for the samples examined here, calibration by target factor analysis is insensitive to variation in fluorescent intensity when the tablet coating emission spectrum is included in the matrix of target vectors.

Universal quantitative models using NIR reflectance spectroscopy were developed for the analysis of API contents (active pharmaceutical ingredient) in roxithromycin and erythromycin ethylsuccinate tablets from different manufacturers in China. The two quantitative models were built from 78 batches of roxithromycin samples from 18 different manufacturers with the API content range from 19.5% to 73.9%, and 66 batches erythromycin ethylsuccinate tablets from 36 manufacturers with the API content range from 28.1% to 70.9%. Three different spectrometers were used for model construction in order to have robust and universal models. The root mean square errors of cross validation (RMSECV) and the root mean square errors of prediction (RMSEP) of the model for roxithromycin tablets were 1.84% and 1.45%, respectively. The values of RMSECV and RMSEP of the model for erythromycin ethylsuccinate tablets were 2.31% and 2.16%, respectively. Based on the ICH guidelines and characteristics of NIR spectroscopy, the quantitative models were then evaluated in terms of specificity, linearity, accuracy, precision, robustness and model transferability. Our study has shown that it is feasible to build a universal quantitative model for quick analysis of pharmaceutical products from different manufacturers. Therefore, the NIR method could be used as an effective method for quick, non-destructive inspection of medicines in the distribution channels or open market.

The photostability of lercanidipine, a dihydropyridine calcium-channel blocker used in the treatment of the hypertension, was studied. Drug substance and its solutions and formulations were exposed to UV-A radiations (solar simulator) and the photodegradation process was monitored by UV spectrophotometry, HPLC and HPLC-mass spectrometry. The effect of the solvent (ethanol and ethanol/PBS 1:1 v/v) on the photodegradation pathway and kinetic was evaluated. Lercanidipine and its photodegradation products were separated by a selective reversed-phase HPLC method and the main photoproducts were characterized by HPLC-MS/MS analysis, using an electrospray ionization source (ESI) and an ion trap analyzer. Photochemical reactions, involved in the photodegradation of lercanidipine, include aromatisation of the dihydropyridine moiety, formation of nitrosoderivatives and N-dealkylation in the side chain. The developed stability-indicating HPLC method was then applied to the quality control of commercially available lercanidipine formulations (tablets).

A rapid cyclodextrin modified micellar electrokinetic chromatography (CD-MEKC) method was proposed for the determination of resibufogenin and cinobufagin in the Chinese herbal extracts from toad venom and its medicinal preparation (Liushen tablet). The two components have the close structural similarity and similar hydrophobicity, which result in poor resolution in normal MEKC. The addition of neutral beta-CD to the MEKC system was found to improve the separation of the studied compounds. The effects of several CD-MEKC parameters on the resolutions were evaluated systematically. Based on the investigation, a background electrolyte solution consisting of 10 mM borate buffer adjusted to pH 8.5, 40 mM sodium dodecyl sulfate (SDS), 12 mM beta-CD and 10% (v/v) of methanol was found to be optimal conditions for the fast separation. The contents of resibufogenin and cinobufagin were successfully determined within 5 min, with satisfactory repeatability and recovery.