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First-line tuberculostatic agents, Rifampicin (RIF), Isoniazid (ISH), Ethambutol (ETB), and Pyrazinamide (PZA) are generally administered as a fixed-dose combination (FDC) for improving patient adherence. The major quality challenge of these FDC products is their variable bioavailability, where RIF and its solid state are key factors. In this work, the analysis of the impact of the polymorphism in the performance of RIF in RIF-ISH and PZA-RIF-ISH combined products was carried out by an overall approach that included the development and validation of two methodologies combining near-infrared (NIR) spectroscopy and partial least squares (PLS) to the further evaluation of commercial products. For NIR-PLS methods, training and validation sets were prepared with mixtures of Form I/Form II of RIF, and the appropriate amount of ISH (for double associations) or ISH-PZA (for triple associations). The corresponding matrix of the excipients was added to the mixture of APIs to simulate the environment of each FDC product. Four PLS factors, reduced spectral range, and the combination of standard normal variate and Savitzky-Golay 1 st derivative (SNV-D') were selected as optimum data pre-treatment for both methods, yielding satisfactory recoveries during the analysis of validation sets (98.5±2.0%, and 98.7±1.8% for double- and triple-FDC products, respectively). The NIR-PLS model for RIF-ISH successfully estimated the polymorphic purity of Form II in double-FDC capsules (1.02 ± 0.02w/w). On the other hand, the NIR-PLS model for RIF-ISH-PZA detected a low purity of Form II in triple FDC tablets (0.800 ± 0.021w/w), these results were confirmed by X-ray powder diffraction. Nevertheless, the triple-FDC tablets showed good performance in the dissolution test (Q=99-102%), implying a Form II purity about of 80% is not low enough to affect the safety and efficacy of the product., Competing Interests: Declaration of Interests 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 © 2023 American Pharmacists Association. Published by Elsevier Inc. All rights reserved.)

Comprehensive knowledge of the critical properties of the active pharmaceutical ingredients is a requirement within the modern concept of quality. Praziquantel hemihydrate (HH) and monohydrate (MH) are new solid forms of this antihelmintic agent, which have better solubility properties than the commercial anhydrous solid form (polymorph A). The thermal stability of the hydrates was evaluated, aiming to understand any possible transformation (amorphization, change to a less soluble form). Therefore, HH and MH were prepared along with the related anhydrous solid forms A and B, and characterized employing solid-state nuclear magnetic resonance, powder X-ray diffraction, mid and near infrared spectroscopy, thermal methods and the intrinsic dissolution rate. The transformations of HH and MH under thermal stress conditions were monitored through a variable temperature infrared spectroscopy approach, assisted by multivariate curve resolution with alternating least squares (MCR-ALS), finding that HH undergoes a two-step transformation (HH→B→A) to form A, whereas MH dehydrates directly into form A. This was further confirmed by conventional calorimetric methods (differential scanning calorimetry and thermogravimetry) and powder X-ray diffractometry. The impact of changes in the stressed solid forms and their dissolution rates was also assessed. Significant differences in dissolution performance were found regarding the solid forms produced as a consequence of thermally-induced dehydration., Competing Interests: The authors declare no conflict of interest., (© 2022 The Authors.)

Meloxicam (MLX) is a non-steroidal anti-inflammatory drug, extensively used for inflammatory diseases and pain treatments, which exhibits five known solids forms. Form IV of MLX, a zwitterionic monohydrate (MH), is an emblematic hydrate case with promissory dissolution properties in a poorly soluble drug. However, the lack of information about MH stability regarding the dehydration process and phase transition impedes the development of further stability studies. A multi-spectroscopic/chemometric approach was implemented coupling middle- (MIR), near-infrared (NIR) and Raman spectroscopies to monitor the heat-mediated dehydration process of MH. The application of multivariate curve resolution-alternating least squares (MCR-ALS) to multi-source spectra by data fusion allow a complete view of the phenomena, improving the selectivity and precision to establish the transition temperatures and to identify involved species. It was revealed a two-step mechanism, where MH changes to Form V at 90 °C obtaining its complete dehydration at 130 °C, Form V remains unchanged during the temperature range 130-190 °C and then the polymorphic conversion to Form I starts, which reaches 100 % at 230 °C before melting MLX (248 °C). The findings of this work allow set targets in the process control of products using MH. Additionally, MCR-ALS detected an event not evidenced by conventional thermal analysis, the transformation of Form V to Form I., Competing Interests: Declaration of Competing Interest The authors declare that they have no conflict of interest., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Pyrazinamide (PZA), Rifampicin (RIF), Isoniazid (ISH) and Ethambutol (ETB) form the core for the treatment of Tuberculosis, today a devastating disease in low-income populations around the world. These drugs are usually administrated by fixed-dose combination (FDC) products, to favour the patient compliance and prevent bacterial resistance. PZA exists in four enantiotropically-related polymorphs (Forms α, δ, β and γ), but only Form α is considered suitable for pharmaceutical products due to its stability and bioavailability properties. The classical approaches to address solid-state (microscopy, X-ray diffraction and calorimetry) shows limitations for quantification of polymorphs in the presence of excipients and other active components, as in the case of FDC tablets. In this work, an overall strategy was developed using near infrared spectroscopy (NIR) coupled to partial least squares regression (PLS) to quantify Form α of PZA in drug substance (raw material) and PZA/RIF/ISH-FDC tablets. For this purpose, two PLS models were constructed, one for drug substance preparing training (n = 30) and validation (n = 18) samples with a ternary composition (Form α/Form δ/Form γ), and other for FDC drug products, also including the appropriate amount of RIF, ISH and the matrix of excipients in order to simulate the environment of PZA/RIF/ISH association. The NIR-PLS models were optimized using a novel smart approach based on radial optimization (full range, 3 L V and MSC-D' and SNV-D' as pre-treatment, for raw material and FDC tablets, respectively). During the validation step, both methods showed no bias or systematic errors and yielded satisfactory recoveries (102.5 ± 3.1 % for drug substance and 98.7 ± 1.5 % for FDC tablets). When commercial drug substance was tested, NIR-PLS was able to predict the content of Form α (0.98 ± 0.01 w/w). The model for FDC tablets allowed estimating polymorphic purity in intact (0.984 ± 0.003 w/w), sectioned (0.986 ± 0.002 w/w), and powered (0.985 ± 0.004 w/w) tablets, showing the methodology could be applied to a different stage of the process (i.e premixed-powders or granulates). The suitability of the method was also verified when Form α was satisfactorily analysed in FDC fortified with Form δ and Form γ to reach 0.78, 0.88 and 0.98 w/w, Form α. This strategy results in an excellent alternative to ensure the polymorphic purity of PZA throughout the overall pharmaceutical manufacturing process., Competing Interests: Declaration of Competing Interest The authors report no declarations of interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Praziquantel (PZQ) is a highly effective low-cost anthelmintic agent used as the first-choice treatment against schistosomiasis. The low solubility of the active is a major drawback for pharmaceutical formulation. A valid approach of the pharmaceutical industry for the improvement of the pharmacotechnical features of the active principles (such as solubility, processability, stability, among others), is the preparation of new solid forms, such as salts, polymorph, and pseudo-polymorph. Herein we report the preparation and characterization of a new solid form PZQ. The PZQ monohydrate (PZQ-MH) was prepared by a solventless procedure from the commercial racemate and the product was characterized at the solid-state employing optical digital microscopy, thermal methods (melting point, differential scanning calorimetry and thermogravimetric analysis), as well as and mid-infrared and near infrared spectroscopies. The chemical structure and content of water were full assessed by 1 H nuclear magnetic resonance (NMR) in solution. The amount of water in PZQ-was also determined by different approaches, including thermogravimetric analysis and the loss on drying test. Solid-state 13 C NMR (ssNMR) and X-ray powder diffraction (XRPD) completed the structural characterization of the new monohydrate. PZQ-MH showed a crystalline behavior during XRPD experiments and showed relevant differences in spectroscopic, calorimetric, ssNMR and XRPD signals when it was compared with the known crystal (Form A) and amorphous forms of PZQ. The determination of the intrinsic dissolution rate (IDR) of PZQ-MH was carried out as a functional characterization, observing that the new form had slightly higher IDR than Form A., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Today, pharmaceutical products are submitted to a large number of analytical tests, planned to either ensure or construct their quality. The official methods of analysis used to perform these determinations are very different in nature, but almost all demand the intensive use of reagents and manpower as major drawbacks. Thus, analytical development is continuously evolving to find fast and smart approaches. First-order chemometric models are well-known in the pharmaceutical industry, and are extensively used in many fields. Such is the impact of chemometric models that regulatory agencies include them in guidelines and compendia. However, the mention or practical application of higher-order models in the pharmaceutical industry is rather scarce. Herein, we try to bring a brief introduction to chemometric models and useful literature references, focusing on higher-order chemometric models (HOCM) applied to reduce manpower, reagent consumption, and time of analysis, without sacrificing accuracy or precision, while gaining selectivity and sensitivity. The advantages and drawbacks of HOCM are also discussed, and the comparison to first-order chemometric models is also analyzed. Along the work, HOCM are evidenced as a powerful tool for the pharmaceutical industry; moreover, its implementation is shown during several steps of production, such as identification, purity test and assay, and other applications as homogeneity of API distribution, Process Analytical Technology (PAT), Quality by Design (QbD) or natural product fingerprinting. Among these topics, qualitative and quantitative applications were covered. Experimental approaches of chemometrics coupled to several analytical techniques such as UV-vis, fluorescence and vibrational spectroscopies (NIR, MIR and Raman), and other techniques as hyphenated-chromatography and electrochemical techniques applied to production and analysis are discussed throughout this work., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The development of a chemometric method for monitoring the pharmaceutical dissolution, under green analytical chemistry principles, was reported. Meloxicam (MEL) and pridinol (PRI) were employed as a combination model. Multivariate curve resolution with alternating least squares (MCR-ALS) was proposed to resolve UV spectra of the analytes during pharmaceutical dissolution. Empowering UV-vis spectrophotometry, which is considered an economical, ecological and fast technique, but poor in terms of selectivity. The developed method was validated in accordance to ICH guidelines, fulfilling acceptance criteria for linearity (r > 0.99 in the ranges 3.5-19.6 mg L -1 and 0.81-5.41 mg L -1 for MEL and PRI, respectively), accuracy (96.3% and 100.6% recoveries for MEL and PRI respectively), and precision (RSD < 10%) were evaluated using an independent validation set. Using a commercial sample, the method's accuracy was evaluated against HPLC analysis. Dissolution profiles were obtained using both methods. A point-to-point comparison with Moore and Flanner's factors (f 1 and f 2 ) were calculated. Specificity was evaluated by spectral correlation (R 2 >0.950). Additionally, the developed method works on-line and forgoes organic solvents and dilutions, lending itself to automation., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The assessment of polymorphism is a problematical issue for regulatory agencies, because variations among crystalline forms of active pharmaceutical ingredient (API) can lead to changes in the efficacy and safety of formulated product. Such conversions are very hard to be detected, thus, the development of techniques for the identification, characterization and quantification of polymorphs results essential in all stages of the manufacturing process. The presence of excipients in formulated products may change the crystal stability of an API, by catalyzing a polymorphic transformation or stabilizing the less stable form. As paradox, all suitable analytical techniques (spectroscopies, thermal analysis, NMR and DRX, and others) for polymorphic analysis are affected by excipients. A deep understanding of the polymorphism-excipient relationship is in full accordance with Quality by Design (QbD) paradigm, the systematic approach focused in quality building into a product based in the full understanding of the products and process. In this work, a novel approach based on thermal stress, MIR monitoring, multivariate curve resolution with alternating least squares (MCR-ALS) and kinetic analysis was developed and applied to monitor polymorphism behavior of model API in formulated products. Commercial tablets, physical mixtures and commercial API, were processed and analyzed under the proposed approach. Commercial tablets of MFA revealed a fast conversion to Form II, contrasting to the behavior of the pure API. Physical mixtures showed similar behavior to commercial tablets, thus reduction in transformation times was related to MFA-excipients physical interaction, even at surface level. Calorimetric studies support the conclusion obtained. The developed approach could be extended to others APIs and other stress sources (humidity, solvents, mechanical forces and its combinations), being a valuable tool for QbD environment., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Nimodipine (NIM) is a calcium channel-blocking agent, which in the solid state exhibits two crystalline modifications, Mode I and Mode II. The first one is a racemic mixture, while the second is a conglomerate. Because the drug has poor aqueous solubility and Mode I is twice as soluble as Mode II, the former is widely preferred for the development of pharmaceutical forms. In order to study the effect of thermal stimuli on the behavior of NIM, an analytical method was developed coupling ATR-FTIR spectroscopy to Multivariate Curve Resolution with Alternating Least Squares (MCR-ALS). The method allowed to monitor the transformations of each polymorph, their respective mixtures and commercial samples, during the thermal treatment. It was observed that Mode II experienced changes during the experiments and the chemometric technique provided the abundance profile and the pure spectra of the different species involved. In this way, it was established that Mode II has two transitions, at 116.8 °C and 131.9 °C, which reflect that Mode II is first transformed into Mode I, which then melts. The liquid phase solidifies to give an amorphous (AM) vitreous solid, which does not revert to the crystalline state. The analysis of a commercial sample of NIM exhibited the similar transformations than Mode II; however, a pronounced decrease was noted in the first transition temperature (95 °C), whereas the second remained essentially unchanged (131.6 °C). This could be a result of the presence of mixtures of Mode I and Mode II (0.32:0.68) in the bulk solid, as confirmed by the analysis of a physical mixture of crystals of Modes I and II. Therefore, it was concluded that the developed ATR-FTIR/MCR-ALS method is suitable for the detailed analysis of the crystalline forms of NIM in bulk drug and enables de study of their possible thermally promoted interconversions., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Mefenamic Acid (MFA) is a widely-used non-steroidal anti-inflammatory drug. MFA presents four possible crystal forms; Form I and Form II being the only two pure crystals that have been isolated and fully characterized. Both Form I and Form II were prepared following the literature and completely characterized by middle (MIR) and near (NIR) infrared spectroscopy, digital optical microscopy, differential scanning calorimetry, melting point and dissolution properties. In order to develop quantitative models to assess Form I in formulated products, two sets of samples, training (n=10) and validation (n=8) sets, were prepared by mixing both polymorphs and the matrix of excipient (simulating commercial tablets). The particle size of the samples was homogenized by sieving and samples were mechanically mixed. A batch of commercial tablets was gently disaggregated, sieved and mechanically mixed for further analysis. For each sample, full MIR and NIR spectra were acquired and used as input of partial least squares (PLS) algorithm separately. Method optimization and internal validation were performed by leave one out procedure. Full spectra and 5 PLS-factors were used for MIR; while, 5 PLS-factors and mean center spectra of full spectra were the optimal conditions for NIR. Accuracy and precision were assessed by evaluation of the actual vs. predicted curve of validation set; and by calculating validation set recoveries and deviations (104.3±8.2% and 100.4±1.0% for MIR and NIR respectively). Only NIR-PLS yielded acceptable results and low deviations during commercial samples evaluation (102.8±0.1%). The same behavior was observed when spiked tablets were analyzed (103.5±0.5%). Additionally, for the calibration set ten dissolution profiles (average of 6 curves each), were obtained under optimized test conditions (900 ml of buffer phosphate pH 9 with surfactant, apparatus II USP, 100rpm, detection at 342nm). A multiple linear regression (MLR) was carried out using dissolution profiles and Form I content. The developed MLR model could correlate dissolution profiles and polymorphic richness. This approach, coupled to previously developed NIR-PLS, may act as a valid tool to estimate dissolution profiles from solid forms., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Current regulations command to properly characterize pharmaceutically relevant solid systems. Chemometrics comprise a range of valuable tools, suitable to process large amounts of data and extract valuable information hidden in their structure. This review aims to detail the results of the fruitful association between analytical techniques and chemometrics methods, focusing on those which help to gain insight into the characteristics of drug polymorphism as an important aspect of the solid state of bulk drugs and drug products. Hence, the combination of Raman, terahertz, mid- and near- infrared spectroscopies, as well as instrumental signals resulting from X-ray powder diffraction, 13 C solid state nuclear magnetic resonance spectroscopy and thermal methods with quali-and quantitative chemometrics methodologies are examined. The main issues reviewed, concerning pharmaceutical drug polymorphism, include the use of chemometrics-based approaches to perform polymorph classification and assignment of polymorphic identity, as well as the determination of given polymorphs in simple mixtures and complex systems. Aspects such as the solvation/desolvation of solids, phase transformation, crystallinity and the recrystallization from the amorphous state are also discussed. A brief perspective of the field for the next future is provided, based on the developments of the last decade and the current state of the art of analytical instrumentation and chemometrics methodologies., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The understanding of materials and processes is a requirement when it comes to build quality into pharmaceutical products. This can be achieved through the development of rapid, efficient and versatile analytical methods able to perform qualification or quantification tasks along the manufacturing and control process. Process monitoring, capable of providing reliable real-time insights into the processes performance during the manufacturing of solid dosage forms, are the key to improve such understanding. In response to these demands, in recent times multivariate chemometrics algorithms have been increasingly associated to different analytical techniques, mainly vibrational spectroscopies [Raman, mid-infrared (MIR), near-infrared (NIR)], but also ultraviolet-visible (UV-vis) spectroscopy, X-ray powder diffraction and other methodologies. The resulting associations have been applied to the characterization and evaluation of different aspects of pharmaceutical materials at the solid state. This review examines the different scenarios where these methodological marriages have been successful. The list of analytical problems and regulatory demands solved by chemometrics analysis of solid-state multivariate data covers the whole manufacturing and control processes of both, active pharmaceutical ingredients in bulk and in their drug products. Hence, these combinations have found use in monitoring the crystallization processes of drugs and supramolecular drug associations (co-crystals, co-amorphous and salts), to access the correct crystal morphology, particle size, solubility and dissolution properties. In addition, they have been applied to identify and quantitate specific compounds, mainly active pharmaceutical ingredients in complex solid state mixtures. This included drug stability against different stimuli, solid-state transformations, or detection of adulterated or fraudulent medicines. The use of chemometrics-assisted analytical methods as part of the modern concept of process analytical technology, where every process step of every product batch from raw materials to final product must take place in a controlled manner is discussed. Finally, but no less important, the application of chemometrics methods to chemical imaging, aiming to extract spatial and compositional information is also revised., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Albendazole (ALB) is a broad-spectrum anthelmintic, which exhibits two solid-state forms (Forms I and II). The Form I is the metastable crystal at room temperature, while Form II is the stable one. Because the drug has poor aqueous solubility and Form II is less soluble than Form I, it is desirable to have a method to assess the solid-state form of the drug employed for manufacturing purposes. Therefore, a Partial Least Squares (PLS) model was developed for the determination of Form I of ALB in its mixtures with Form II. For model development, both solid-state forms of ALB were prepared and characterized by microscopic (optical and with normal and polarized light), thermal (DSC) and spectroscopic (ATR-FTIR, Raman) techniques. Mixtures of solids in different ratios were prepared by weighing and mechanical mixing of the components. Their Raman spectra were acquired, and subjected to peak smoothing, normalization, standard normal variate correction and de-trending, before performing the PLS calculations. The optimal spectral region (1396-1280cm(-1)) and number of latent variables (LV=3) were obtained employing a moving window of variable size strategy. The method was internally validated by means of the leave one out procedure, providing satisfactory statistics (r(2)=0.9729 and RMSD=5.6%) and figures of merit (LOD=9.4% and MDDC=1.4). Furthermore, the method's performance was also evaluated by analysis of two validation sets. Validation set I was used for assessment of linearity and range and Validation set II, to demonstrate accuracy and precision (Recovery=101.4% and RSD=2.8%). Additionally, a third set of spiked commercial samples was evaluated, exhibiting excellent recoveries (94.2±6.4%). The results suggest that the combination of Raman spectroscopy with multivariate analysis could be applied to the assessment of the main crystal form and its quantitation in samples of ALB bulk drug, in the routine quality control laboratory., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Structural polymorphism of active pharmaceutical ingredients (API) is a relevant concern for the modern pharmaceutical industry, since different polymorphic forms may display dissimilar properties, critically affecting the performance of the corresponding drug products. Mebendazole (MEB) is a widely used broad spectrum anthelmintic drug of the benzimidazole class, which exhibits structural polymorphism (Forms A-C). Form C, which displays the best pharmaceutical profile, is the recommended one for clinical use. The polymorphs of MEB were prepared and characterized by spectroscopic, calorimetric and microscopic means. The polymorphs were employed to develop a suitable chemometrics-assisted sample display model based on the first two principal components of their ATR-FTIR spectra in the 4000-600 cm(-1) region. The model was internally and externally validated employing the leave-one-out procedure and an external validation set, respectively. Its suitability for revealing the polymorphic identity of MEB in tablets was successfully assessed analyzing commercial tablets under different physical forms (whole, powdered, dried, sieved and aged). It was concluded that the ATR-FTIR/PCA (principal component analysis) association is a fast, efficient and non-destructive technique for assigning the solid-state forms of MEB in its drug products, with minimum sample pre-treatment., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Today virgin and extra-virgin olive oil (VOO and EVOO) are food with a large number of analytical tests planned to ensure its quality and genuineness. Almost all official methods demand high use of reagents and manpower. Because of that, analytical development in this area is continuously evolving. Therefore, this review focuses on analytical methods for EVOO/VOO which use fast and smart approaches based on chemometric techniques in order to reduce time of analysis, reagent consumption, high cost equipment and manpower. Experimental approaches of chemometrics coupled with fast analytical techniques such as UV-Vis spectroscopy, fluorescence, vibrational spectroscopies (NIR, MIR and Raman fluorescence), NMR spectroscopy, and other more complex techniques like chromatography, calorimetry and electrochemical techniques applied to EVOO/VOO production and analysis have been discussed throughout this work. The advantages and drawbacks of this association have also been highlighted. Chemometrics has been evidenced as a powerful tool for the oil industry. In fact, it has been shown how chemometrics can be implemented all along the different steps of EVOO/VOO production: raw material input control, monitoring during process and quality control of final product., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Mixing aqueous solutions of sodium diclofenac (DIC-Na) and ranitidine hydrochloride (RAN·HCl) afforded an off-white solid (DIC-RAN) that was investigated from the microscopic, thermal, diffractometric, spectroscopic, and functional (chemometrics-assisted dissolution) points of view. The solid has a 2:1 (DIC:RAN) molar ratio according to (1)H nuclear magnetic resonance spectroscopy. It is thermally stable, displaying a broad endothermic signal centered at 105°C in the thermogram, and its characteristic reflections in the powder X-ray diffractogram remained unchanged after a 3-month aging period. Scanning electron microscopy micrographs uncovered its morphology, whereas the spectral data suggested an interaction between the carboxylic acid of DIC and the alkyldimethylamino moiety of RAN. The dissolution of DIC-RAN was monitored at different pH values by an ultraviolet/chemometrics procedure, being complete within 5 min at pH 6.8. This compares favorably with the dissolution of a DIC-Na sample of the same particle size., (Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.)

Exposure of cimetidine (CIM) to dry heat (160-180°C) afforded, upon cooling, a glassy solid containing new and hitherto unknown products. The kinetics of this process was studied by a second order chemometrics-assisted multi-spectroscopic approach. Proton and carbon-13 nuclear magnetic resonance (NMR), as well as ultraviolet and infrared spectroscopic data were jointly used, whereas multivariate curve resolution with alternating least squares (MCR-ALS) was employed as the chemometrics method to extract process information. It was established that drug degradation follows a first order kinetics. One of the products was structurally characterized by mono- and bi-dimensional NMR experiments. It was found to be the N3-enamino tautomer (TAU) of CIM, resulting from the thermal isomerization of the double bond of the cyanoguanidine moiety of the drug, from the imine form to its N3-enamine state. The thus generated tautomer demonstrated to be stable for months in the glassy solid and in methanolic solutions. A theoretical study of CIM and TAU revealed that the latter is less stable; however, the energy barrier for tautomer interconversion is high enough, precluding the process to proceed rapidly at room temperature., (Copyright © 2015 Elsevier B.V. All rights reserved.)

The identity of the polymorphic form of an active pharmaceutical ingredient is an important parameter that may affect the performance of the drug formulation. This calls for special techniques, able to classify crystal forms or assign the polymorphic identity to a given solid in a mixture. In order to develop a method to determine which of the relevant polymorphs of Cimetidine (CIM) is present in commercial tablet samples, authentic forms A, B, D and M1 of the drug were prepared, structurally characterized and employed as standards. Thus, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) was coupled to Principal Component Analysis (PCA) and used for the classification of physical mixtures of CIM and excipients, as well as laboratory-made and commercial tablets, according to their polymorphic composition. It was demonstrated that two principal components (PCs) suffice to classify the samples of the four forms of CIM into distinct groups, and that method performance is optimum when the second and third PCs are used for the classification process. The application of the method to commercial tablets of CIM also gave good results, confirming they were prepared employing the correct polymorph (form A)., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Current standards and regulations demand the pharmaceutical industry not only to produce highly pure drug substances, but to achieve a thorough understanding of the impurities accompanying their manufactured drug substances and products. These challenges have become important goals of process chemistry and have steadily stimulated the search of impurities after accelerated or forced degradation procedures. As a result, impurity profiling is one of the most attractive, active and relevant fields of modern pharmaceutical analysis. This activity includes the identification, structural elucidation and quantitative determination of impurities and degradation products in bulk drugs and their pharmaceutical formulations. Nuclear magnetic resonance (NMR) spectroscopy has evolved into an irreplaceable approach for pharmaceutical quality assessment, currently playing a critical role in unequivocal structure identification as well as structural confirmation (qualitative detection), enabling the understanding of the underlying mechanisms of the formation of process and/or degradation impurities. NMR is able to provide qualitative information without the need of standards of the unknown compounds and multiple components can be quantified in a complex sample without previous separation. When coupled to separative techniques, the resulting hyphenated methodologies enhance the analytical power of this spectroscopy to previously unknown levels. As a result, and by enabling the implementation of rational decisions regarding the identity and level of impurities, NMR contributes to the goal of making better and safer medicines. Herein are discussed the applications of NMR spectroscopy and its hyphenated derivate techniques to the study of a wide range pharmaceutical impurities. Details on the advantages and disadvantages of the methodology and well as specific challenges with regards to the different analytical problems are also presented., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Crystal polymorphism of active ingredients is relevant to the pharmaceutical industry, since polymorphic changes taking place during manufacture or storage of pharmaceutical formulations can affect critical properties of the products. Cimetidine (CIM) has several relevant solid state forms, including four polymorphs (A, B, C and D), an amorphous form (AM) and a monohydrate (M1). Dehydration of M1 has been reported to yield mixtures of polymorphs A, B and C or just a single form. Standards of the solid forms of CIM were prepared and unequivocally characterized by FTIR spectroscopy, digital microscopy, differential scanning calorimetry and solid state (13)C NMR spectroscopy. Multivariate curve resolution with alternating least squares (MCR-ALS) was coupled to variable temperature attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) to dynamically characterize the behavior of form M1 of CIM over a temperature range from ambient to 160°C, without sample pretreatment. MCR-ALS analysis of ATR-FTIR spectra obtained from the tested solid under variable temperature conditions unveiled the pure spectra of the species involved in the polymorphic transitions. This allowed the simultaneous observation of thermochemical and thermophysical events associated to the changes involved in the solid forms, enabling their unequivocal identification and improving the understanding of their thermal behavior. It was demonstrated that under the experimental conditions, dehydration of M1 initially results in the formation of polymorph B; after melting and upon cooling, the latter yields an amorphous solid (AM). It was concluded that the ATR-FTIR/MCR association is a promising and useful technique for monitoring solid-state phase transformations., (Copyright © 2014 Elsevier B.V. All rights reserved.)

A simple, precise, economic and minimally operator-dependent method was developed under green analytical chemistry principles, for the simultaneous construction of the dissolution curves of a pharmaceutical association in short time and without employing organic solvents, allowing important savings of labor and resources. The carvedilol (CAR) and hydrochlorothiazide (HCT) combined formulation was employed as a model. The method (OD/UV-MCR) involves on-line sample dilution (OD) and UV detection of the analytes, coupled to multivariate curve resolution with alternating least squares (MCR-ALS). OD/UV-MCR proved to be robust and was successfully validated in accordance to ICH guidelines, fulfilling acceptance criteria for specificity (r(2) of spectral correlation>0.950), linearity [r>0.999 (N=25) in the ranges 1.00-31.1mg l(-1) and 0.51-15.2mg l(-1) for CAR and HCT, respectively] and precision (RSD<2%). Accuracy was assessed by point-to-point comparison between the dissolution profiles furnished by the proposed method with those provided by HPLC analysis, evidencing the usefulness of this monitoring system. In addition, OD/UV-MCR was successfully employed for the comparative analysis of three lots of commercial formulations of the CAR-HCT pharmaceutical association, belonging to a couple of different brands, employing Moore and Flanner's f2 similarity indicator., (Copyright © 2013 Elsevier B.V. All rights reserved.)

The association of an on-line circulation system with a chemometrics-assisted UV detection strategy is described as a useful system to continuously monitor the dissolution of a pharmaceutical preparation containing two active ingredients, and as a tool for the simultaneous determination of the dissolution curves and dissolution profiles of the latter. Multivariate curve resolution with alternating least squares (MCR-ALS) was used as the chemometric tool to quantitate the analytes, while the hydrochlorothiazide-bisoprolol fumarate (HCT-BIS) association was employed as a model for method development. The experiments were carried out with a dissolution tester configured as apparatus II (paddles), under USP 32 official conditions. The suitability of the calibration procedure for quantitating the dissolved drugs was assessed according to ICH guidelines, with regards to linearity in the working range, specificity, accuracy and precision. Figures of merit, including limits of detection and quantitation were also determined, as well as the method's robustness with regards to detection wavelength range. The system was able to consistently provide very reproducible dissolution curves of commercial tablets, which were statistically similar to those furnished by a manual sampling technique, followed by HPLC analysis. To demonstrate the usefulness of the proposed system, the dissolution profiles of different lots of HCT-BIS tablets were acquired and three of them were conveniently compared at a 31 data point level, employing the f(1) and f(2) ("difference" and "similarity") indexes. Use of multiple data points for comparison ensured reliability of the results., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Liquid chromatographic-diode array detection data recorded for aqueous mixtures of 11 pesticides show the combined presence of strongly coeluting peaks, distortions in the time dimension between experimental runs, and the presence of potential interferents not modeled by the calibration phase in certain test samples. Due to the complexity of these phenomena, data were processed by a second-order multivariate algorithm based on multivariate curve resolution and alternating least-squares, which allows one to successfully model both the spectral and retention time behavior for all sample constituents. This led to the accurate quantitation of all analytes in a set of validation samples: aldicarb sulfoxide, oxamyl, aldicarb sulfone, methomyl, 3-hydroxy-carbofuran, aldicarb, propoxur, carbofuran, carbaryl, 1-naphthol and methiocarb. Limits of detection in the range 0.1-2 μg mL(-1) were obtained. Additionally, the second-order advantage for several analytes was achieved in samples containing several uncalibrated interferences. The limits of detection for all analytes were decreased by solid phase pre-concentration to values compatible to those officially recommended, i.e., in the order of 5 ng mL(-1)., (Copyright © 2010 Elsevier B.V. All rights reserved.)

Four-way data were obtained by recording the kinetic evolution of excitation-emission fluorescence matrices for samples containing the analytes carbaryl and 1-naphthol, two widely employed pesticides, in the concentration ranges 0-363 μg L(-1) and 0-512 μg L(-1), respectively. The reaction followed was the alkaline hydrolysis of carbaryl to produce 1-naphthol, a fact which introduced strong linear dependencies and multi-linearity losses in the analyzed system. Data processing was performed with unfolded partial least-squares combined with residual trilinearization (U-PLS/RTL) and also with a suitably initialized and restricted parallel factor model (PARAFAC), combined with calibration based on multi-linear regression. U-PLS/RTL is shown to be significantly simpler in its implementation and to provide similar figures of merit. The applied chemometric strategy is able to successfully determine the analytes in water samples containing uncalibrated interferences, such as other commonly employed agrochemicals and also a naturally occurring background signal., (Copyright © 2010 Elsevier B.V. All rights reserved.)

A simple chemometric approach to differentiate among the three crystalline polymorphs of the model drug Furosemide (FUR) in a pharmaceutical dosage form is presented. The proposed method is based on the principal component analysis with confidence regions (PCA-CR) comparison of the dissolution profiles of the test pharmaceutical formulation, and formulations containing the different polymorphs, employed as the corresponding references. For the elaboration of the references, FUR polymorphs I, II and III were prepared, characterized and compounded with the excipients found in the test commercial formulation. The dissolutions were carried out in a discriminating HCl-KCl dissolution medium (pH 2.2), and the corresponding profiles were constructed from the absorbances (274 nm) of the dissolution samples. PCA-CR was able to differentiate among the three crystalline polymorphs of FUR and to confirm the presence of polymorph I in the test sample, with 99% statistical confidence. The PCA-CR results were compared with those obtained by a bootstrap-mediated implementation of Moore and Flanner's difference factor (f(2)). The same conclusion was reached employing an f(2)-based comparison, despite its inability to differentiate between polymorphs II and III. Therefore, PCA-CR may be considered a complementary and useful tool for probing the polymorphic form present in a pharmaceutical formulation.

A convenient new method for the simultaneous determination of losartan potassium and hydrochlorothiazide, with minimum sample pretreatment, is described. The procedure, based on the multivariate analysis of spectral data in the 220-274 nm region by the partial least squares algorithm, is linear in the concentration range 1.06-5.70 mg L(-1) for hydrochlorothiazide and 4.0-22.2 mg L(-1) for losartan. It is simple, rapid and robust, allowing accurate and precise results, with drug recovery rates of 99.3 and 100.4% and relative standard deviations of 1.7 and 1.0% obtained for hydrochlorothiazide and losartan, respectively. The method was applied to the simultaneous determination of both analytes in tablets, and it provided good results which were in statistical agreement with those provided by independent HPLC analyses of the samples. The method has also been successfully applied for the construction of drug dissolution profiles of a commercial pharmaceutical preparation containing both analytes.

A new approach for testing batch "similarity" through comparison of drug dissolution profiles, based on principal component analysis with the establishment of a confidence region (PCA-CR), is presented. The dissolution curves corresponding to three brands each of Furosemide and Acetaminophen tablets, taken as model drugs, were prepared by dissolution measurements at multiple pre-specified time points. Reference and test data were simultaneously subjected to PCA and pairwise comparisons between the dissolution characteristics of lots of the same and different brands were carried out. The comparisons involved plotting the weighed scores of the first two principal components of reference and test lots, while decision about "similarity" was made by checking for inclusion of more than 80% of the tablets of the test lot in the 95% confidence ellipse of the reference samples. Two published datasets were also analyzed in the same fashion and all the results were compared with information provided by the difference (f1) and similarity (f2) factor tests. Unlike the f2 criterion, the proposed method reflects variability within the individual dissolution curves, being also highly sensitive to profile (shape and size) variations. Comparison between the area enclosed by the confidence ellipses of the weighed scores plot and the region obtained from the bootstrap-calculated acceptable values of the corresponding f2 tests suggested that PCA-CR represents, in general, a more discriminating standard.

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.

Two new analytical methods have been developed as convenient and useful alternatives for simultaneous determination of hydrochlorothiazide (HCT) and propranolol hydrochloride (PRO) in pharmaceutical formulations. The methods are based on the first derivative of ratio spectra (DRS) and on partial least squares (PLS) analysis of the ultraviolet absorption spectra of the samples in the 250-350-nm region. The methods were calibrated between 8.7 and 16.0 mg L(-1) for HCT and between 14.0 and 51.5 mg L(-1) for PRO. An asymmetric full-factorial design and wavelength selection (277-294 nm for HCT and 297-319 for PRO) were used for the PLS method and signal intensities at 276 and 322 nm were used in the DRS method for HCT and PRO, respectively. Performance characteristics of the analytical methods were evaluated by use of validation samples and both methods showed to be accurate and precise, furnishing near quantitative analyte recoveries (100.4 and 99.3% for HCT and PRO by use of PLS) and relative standard deviations below 2%. For PLS the lower limits of quantification were 0.37 and 0.66 mg L(-1) for HCT and PRO, respectively, whereas for DRS they were 1.15 and 3.05 mg L(-1) for HCT and PRO, respectively. The methods were used for quantification of HCT and PRO in synthetic mixtures and in two commercial tablet preparations containing different proportions of the analytes. The results of the drug content assay and the tablet dissolution test were in statistical agreement (p < 0.05) with those furnished by the official procedures of the USP 29. Preparation of dissolution profiles of the combined tablet formulations was also performed with the aid of the proposed methods. The methods are easy to apply, use relatively simple equipment, require minimum sample pre-treatment, enable high sample throughput, and generate less solvent waste than other procedures.

A new, repeatable, and rapid method has been developed for resolution of binary mixtures of acetaminophen and diclofenac with minimum sample pretreatment and without separation of the analytes. The method, based on the PLS1 processing of absorbance data in the UV region, was successfully used for quantification of the drug content of three tablet preparations. The results obtained were in good agreement with HPLC recovery data. The method also enabled determination of drug-dissolution profiles of these commercial tablets, by simultaneous determination of both analytes during the dissolution test.

This study focuses on the spectrofluorimetric behavior of the pesticide carbendazim in the presence of selected organized assemblies and also on their potential analytical applications. The relatively weak fluorescence emission band of carbendazim is significantly enhanced by micellar media formed by sodium dodecyl sulfate, hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, and decyltrimethylammonium bromide. The influence of the surfactant structures, concentrations, and working experimental conditions on the fluorescence spectra of carbendazim was thoroughly evaluated and discussed. Although the interaction of carbendazim with different cyclodextrins is rather weak, it was corroborated that the fluorescence intensity of this compound in the presence of (2-hydroxy)propyl beta-cyclodextrin is increased by a factor of two. Among the studied organized media, the cationic surfactant hexadecyltrimethylammonium bromide produced the largest signals for the compound of interest. Consequently, the optimal working conditions for the spectrofluorimetric determination of carbendazim in the presence of the latter detergent were analyzed, concluding that previous literature reports should be reconsidered.