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A facile and sensible spectrofluorimetric approach for the measurement of two antipsychotic medications, aripiperazole (ARP) and clozapine (CLZ), was devised and validated. The approach involves reacting the examined medicines with o-phthalaldehyde in the presence of β-mercaptoethanol in a borate buffer of pH 9.0 and pH 10 for ARP and CLZ, respectively, to produce a robustly fluorescent compound that is detected at 450 nm following excitation at 340 nm. The experimental variables influencing the performance and product stability were thoroughly investigated and optimized. Under optimal conditions, the intensity of the fluorescence was linear during a concentration range of 0.1–0.5 μg/mL, with a limit of detection (0.0391 and 0.0400 μg/mL) and limit of quantitation (0.1035 and 0.1332 μg/mL), respectively, for ARP and CLZ. The suggested approach was successful in analyzing commercialized tablets. A statistical investigation of the results produced by the suggested and standard methods showed no remarkable variation in the precision and accuracy of the two approaches. A chemical mechanism using o-phthalaldehyde was proposed. [ABSTRACT FROM AUTHOR]

Quantitation of chromophore-free analytes is always a challenge. To this purpose, derivatization of the analyte constitutes a common strategy, leading to a product with a strong signal. In the current study, a novel xanthone analogue was utilized for the first time for the derivatization of pregabalin, a model analyte with a primary amine moiety that lacks a chromophore. The fact that only the xanthene-based derivative, formed after the derivatization reaction fluoresces, enables avoiding its chromatographic separation from the reagent and thus reducing the analysis time of a series of samples in 1–2 min via a plate reader. The reaction conditions were optimized via a central composite design (CCD), with fluorescence signal as the measure of the yield. The following factors that affect the derivatization reaction were chosen: (a) temperature, (b) reaction time, and (c) triethylamine solution volume used to drive the reaction to completion. After the identification of the optimal conditions, the method was validated according to ICH guidelines, using a fluorescence plate reader for signal measurement (λex = 540, λem = 615 nm). Finally, the newly developed high-throughput method was applied to the determination of drug content in pregabalin bulk. [ABSTRACT FROM AUTHOR]

Oxidative stress, which is characterized by an imbalance between antioxidants and free radicals, plays a pivotal role in the pathogenesis of coronary heart disease, a common and serious cardiovascular condition, and contributes significantly to its development and progression. Serum free thiols are crucial components of the body's antioxidant defense system. The accurate determination of serum free thiol levels provides a reference basis for understanding the body's status and monitoring the risk factors associated with the occurrence and progression of coronary heart disease. In this study, a high performance liquid chromatographic (HPLC) method based on the derivatization reaction of 2,2'-dithiodipyridine was developed to simultaneously obtain the concentrations of total free thiols (Total-SH), low-molecular-mass free thiols (LMM-SH), and protein-free thiols (P-SH) in human serum. An Agilent Eclipse XDB-C18 column (150 mm×4.6 mm, 5 μm) was used for the analysis, and gradient elution was performed at a flow rate of 1 mL/min. A 0.1% formic acid aqueous solution was used as mobile phase A, and a 0.1% formic acid acetonitrile solution was used as mobile phase B. The gradient elution program was as follows: 0-0.1 min, 12%B-30%B; 0.1-2 min, 30%B; 2-2.1 min, 30%B-100%B; 2.1-6 min, 100%B; 6-6.1 min, 100%B-12%B; 6.1-7 min, 12%B. Well-separated peaks appeared after a run time of 5 min. The peak of 2-thiopyridone represented the Total-SH content of the samples, and the peak of the pyridyldithio derivative represented the LMM-SH content. The difference between these two peaks indicated the P-SH content. The derivatization reaction conditions were optimized, and the method was validated. The method demonstrated good linearity, with a correlation coefficient ≥0.9994, over the concentration range of 31.25-1000 μmol/L. The limits of detection for Total-SH and LMM-SH were 2.61 and 0.50 μmol/L, and the limits of quantification for Total-SH and LMM-SH were 8.71 and 1.67 μmol/L, respectively. The recoveries of Total-SH and LMM-SH were in the range of 91.1%-106.0%. The intra- and inter-day precisions ranged from 0.4% to 9.1%. The developed method was used to analyze serum samples from 714 volunteers. The Total-SH concentrations ranged from 376.60 to 781.12 μmol/L, with an average concentration of 555.62 μmol/L. The LMM-SH concentrations varied from 36.37 to 231.65 μmol/L,with an average of 82.34 μmol/L. The P-SH concentrations ranged from 288.36 to 687.74 μmol/L, with an average of 473.27 μmol/L. Spearman's correlation test showed that serum thiol levels were correlated with the severity of coronary artery disease and common clinical biochemical indicators. The proposed study provides a simple and reliable HPLC method for detecting serum free thiols and exploring their relationship with coronary heart disease, offering a new reference for the study of markers related to the risk of coronary heart disease.

A method combining liquid chromatography with a dual-probe ultraspray electrospray ionization (ESI) source and time-of-flight high-resolution mass spectrometry (LC-ESI-TOF/MS) was developed for the simultaneous determination of four steroidal sex hormones, estrone (E1), 17β-estradiol (E2), 17α-ethinyl estradiol (EE2), and estriol (E3), as well as five of their hydroxylated metabolites, 2-hydroxyestrone (2-OHE1), 4-hydroxyestrone (4-OHE1), 16α-hydroxyestrone (16-OHE1), 2-hydroxyestradiol (2-OHE2), and 4-hydroxyestradiol (4-OHE2), in water samples in a short chromatographic run of 10 min. Derivatization of the analytes was optimized using dansyl chloride as the derivatizing agent. Under optimal positive ionization conditions, the following signals, which had not been previously reported, were observed (with theoretical values of m/z 377.1373 for 2- and 4-OHE1 and 378.1452 for 2- and 4-OHE2), corresponding to doubly derivatized catechol estrogens in the form of [M+2H]2+. These mass spectrometric signals were more abundant than those reported previously for the [M+H]+ forms of these hydroxylated metabolites. Solid-phase extraction (SPE) with an octadecyl-endcapped sorbent was used to pretreat tap water and effluent from a wastewater treatment plant (WWTP) in Santiago, Chile. The method achieved the simple, fast, and sensitive measurement of nine estrogens with quantitative recoveries (higher than 85.4%). Detection and quantification limits were between 1 and 17 ng L-1 and between 3 and 58 ng L-1, respectively, for all compounds in water. The estrogens E1 and E2 were found in WWTP effluent at concentrations of 7 ± 1 and 41 ± 1 ng L-1, respectively, and EE2 was detected at a concentration below the limit of quantitation. This study shows that the proposed method is suitable for the accurate, rapid, and selective determination of all these analytes at trace levels.ᅟ [ABSTRACT FROM AUTHOR]

A new sensitive method for the determination of lipoic acid (LA) in selected food items based on its reaction with Mukaiyama reagent (2-chloro-1-methylpyridinium iodide, CMPI) was developed. It was stated that CMPI reacts with reduced form of lipoic acid (dihydrolipoic acid, DHLA) and the stable product is produced. The spectrum of the labeled form of DHLA exhibits new band at 312 nm. Based on its spectral characteristics new spectrophotometric and UV–high-performance liquid chromatography (HPLC) methods of LA determination were elaborated. Both methods allowed determination of the analyte in the concentration range of 5 × 10−6–1 × 10−4 mol L−1with limit of detection 0.39 × 10−6and 0.77 × 10−6 mol L−1for spectrophotometric and HPLC method, respectively. The practical usability of newly developed methods was checked by determination of lipoic acid contents in its pharmaceutical preparateRevitanerw. The proposed method was precise and accurate. The relative error of determination did not exceed ±0.067%. As chromatographic method allowed the determination of analyte in the presence of complex matrix, it was applied for assay of free fraction ofα-lipoic acid in selected food items. A procedure of LA isolation from biological matrix was developed. The extraction with dichloromethane allowed quantitative recovery at 102.94 ± 4.20%. The green barley appeared to be the richest source of LA. [ABSTRACT FROM PUBLISHER]

A facile method was developed for determination of trace volatile acetone by coupling a derivatization reaction to surface-enhanced Raman scattering (SERS). With iodide modified Ag nanoparticles (Ag IMNPs) as the SERS substrate, acetone without obvious Raman signal could be converted to SERS-sensitive species via a chemical derivatization reaction with 2,4-dinitrophenylhydrazine (2,4-DNPH). In addition, acetone can be effectively separated from liquid phase with a purge-sampling device and then any serious interference from sample matrices can be significantly reduced. The optimal conditions for the derivatization reaction and the SERS analysis were investigated in detail, and the selectivity and reproducibility of this method were also evaluated. Under the optimal conditions, the limit of detection (LOD) for acetone was 5 mg L −1 or 0.09 mM (3σ). The relative standard deviation (RSD) for 80 mg L −1 acetone (n=9) was 1.7%. This method was successfully used for the determination of acetone in artificial urine and human urine samples with spiked recoveries ranging from 92% to 110%. The present method is convenient, sensitive, selective, reliable and suitable for analysis of trace acetone, and it could have a promising clinical application in early diabetes diagnosis. [ABSTRACT FROM AUTHOR]

[Display omitted] • Reactive SERS determination of homocysteine could be down to 5 × 10−10 mol/L. • The proposed assay can distinguish homocysteine from cysteine. • This OPA-triggering SERS method could be used to selectively and sensitively determine homocysteine in bovine serum as the mimic real sample. High plasma homocysteine (Hcy) levels may indicate cardiovascular disease. However, sensitive and selective determination of Hcy remains a major challenge. Herein, we present a sensing strategy for Hcy by surface enhanced Raman scattering (SERS) method along with a specific reaction of o-phthalaldehyde (OPA) and Hcy. The obtained adduct 2-(1-carboxyl-3-thiopropyl)-1-isoindolinone (Hcy-OPA) can be directly detected by SERS using gold nanoparticles (Au NPs) as the substrate. The developed SERS method displays superior sensitivity (low detection limit of 2.50 × 10−12 mol L−1) with a broad linear range (5.00 × 10−10 −5.00 × 10−6 mol L−1). As a proof of real application, it can be used to detect Hcy in bovine serum samples with a concentration as low as 5.00 × 10−9 mol L−1, which is free from the interference of the other amino acids and glutathione. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel method combining derivatization reaction and SERS is used to determine methanol in transformer oil. • Ag nanoparticles are deposited on ZnO nanoflowers as an efficient SERS substrate. • Methanol without obvious Raman signal can be converted to SERS-sensitive compounds by derivatization reaction. • The proposed method exhibits high sensitivity and selectivity for detecting trace methanol. Methanol dissolved in transformer oil is used as an aging marker for the degradation of oil-paper insulation systems. Rapid and precise methanol testing is critical for determining the aging status of oil-paper insulation systems. In this study, a new method was proposed for the combination of a derivative reaction and SERS to detect dissolved methanol in transformer oil. Methanol reacted with 4-amino-5-hydrazino-3-mercapto-1,2,4-triazole (AHMT) after it was oxidized in acidic potassium permanganate, this converted methanol with no visible SERS signal into SERS-sensitive compounds. Then, a three-dimensional (3D) structure of flower-like ZnO modified with Ag nanoparticles (Ag NPs) was constructed as a SERS substrate to collect spectra. At the characteristic peak of 825 cm−1, there was a good linear relationship between the concentration and peak area over the range of 1–10000 μg/L, and the limit of detection (LOD) was as low as 0.87 μg/L. The method is simple, fast, sensitive, and has outstanding anti-interference properties; it is suitable for detecting trace methanol and has broad application prospects in the field of aging diagnosis of oil-paper insulation systems in transformer. [ABSTRACT FROM AUTHOR]

The goal of this work is to evaluate the formation of side α-dicarbonyl compounds in high content sugar samples. These compounds may be originated from fructose and glucose, during different derivatization reactions. The formation of D-glucosone, 3-deoxyglucosone, glyoxal, and methylglyoxal, using three derivatization agents (5,6-diamino-2,4-hydroxypyrimidine, 2,4,5-triamine-6-hydroxypyrimidine, and o -phenylenediamine), and ultra-high pressure liquid chromatography in combination with MS detection, has been assessed in the presence of different levels of monosaccharides. 2,4,5-triamine-6-hydroxy-pyrimidine appears to be the most suitable for the analysis of α-dicarbonyl compounds, in this kind of food samples, and was selected as optimum reagent for the quantification of these compounds. The validation of the method was performed through the establishment of external standard calibration curves and analytical figures of merit, and it showed good linearity over a wide concentration range ( r 2 > 0.99), and limits of detection and quantification lower than 42 μg L −1 and 142 μg L −1 , respectively. The validated method has been successfully applied to the determination of the target compounds in honey samples. The intraday and interday assay variability in the analysis of real samples was below 2.3 and 5.7%, respectively, for all analytes. [ABSTRACT FROM AUTHOR]

This paper proposes a new method for quantitative analysis of acrylamide in cereal-based foods and potato chips. The method uses reaction with trifluoroacetic anhydride, and analyses the resulting derivative by use of gas chromatography with electron-capture detection (GC-ECD). The effects of derivatization conditions, including temperature, reaction time, and catalyst, on the acylation reaction were evaluated. Chromatographic analysis was performed on an SE-54 capillary column. Under the optimum conditions, good retention and peak response were achieved for the acrylamide derivative. The analytical method was fully validated by assessment of LODs and LOQs (1 ng g and 25 ng g, with relative standard deviations (RSD) 2.1 and 3.6, respectively), linearity ( R = 0.9935 over the range 0.03-10 μg g), and extraction recovery (>96 %, with RSD below 2.0, for acrylamide spiked at 1, 20, 50, and 100 ng g; 99.8 % for acrylamide content >1000 ng g). The method requires no clean-up of the acrylamide derivative before injection. The method has been successfully used to determine acrylamide levels in different commercial cereal-based foods, French fries, and potato chips. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: The doramectin (DOR), which belongs to the avermectins group (AVM), has a high antiparasitic activity and so it has been widely used in food-producing animals. The DOR shows low fluorescence quantum efficiency and as a consequence, chemical derivatization reactions are necessary to produce derivatives with improved luminescent properties before its determination by fluorimetry. As the presence of this compound in food represents a risk to human health, an easy, clean and low cost derivatization reaction, which is alternative to those usually employed and that enables its spectrofluorimetric determination in milk samples, was developed. Ethanolic solutions of DOR, containing sodium hydroxide at a final concentration of 0.25molL−1, after 60min of heating at 50°C, produced fluorescent signals 1000 times higher than the original ethanolic solution. Using these optimized conditions, a linear response range that extended from 50.00 to 1000μgL−1, with a value of (R 2) equal to 0.9970, was obtained. Average recovery of DOR was 92.5±1.5% (n =3) in bovine milk fortified samples submitted to a liquid–liquid extraction at low temperature and pre concentration process, indicating the usefulness and effectiveness of the proposed method. The proposed spectrofluorimetric method is an alternative to high-performance liquid chromatography (HPLC) based methods, allowing rapid and simple detection of doramectin in milk samples. [Copyright &y& Elsevier]

An indirect chiral HPLC method based on the derivatization reaction with o-phthaldialdehyde and N-acetyl-L-cysteine and fluorimetric detection is applied to determine the enantiomeric purity of amino acids in pharmaceutical preparations. Three samples, vanim™ 14, tebetane, and tulgrasum were analized and their enantiomeric contents were determined. Sample preparation did not require cleanup. The validity of the method was established. The D-AA content is not always specified in the labels of these pharmaceutical preparations. [ABSTRACT FROM AUTHOR]

Abstract: The usefulness of the potassium tert-butoxide/dimethyl sulphoxide/ethyl iodide reaction with carbamate and phenylurea herbicides, and its application to phenoxy acids as a way to prevent hazards and toxicity of the sodium hydride/dimethyl sulphoxide/methyl iodide reaction was studied. Using factorial design optimization of this reaction was carried out. A solid-phase extraction method using dimethyl sulphoxide as eluent on-line with this reaction was developed to determine these herbicides in water samples by gas chromatography–mass spectrometry. Relative standard deviation values were lower than 10% for most of the herbicides in multicomponent trace determinations. Detection limits were in the 0.110–0.652ngL−1 concentration range. The validity of the method was confirmed by recovery studies from natural water samples. [Copyright &y& Elsevier]

The indirect chiral method, based on the o-phthaldialdehyde reaction using the chiral N-acetyl-L-cysteine reagent, has been optimized to determine D-amino acids in milk and oyster samples. Both the derivatization reaction and the HPLC separation have been improved, and simple sample treatments were proposed. The milk sample preparation involved centrifugation and filtration through polytetrafluoroethylene filters for determination of free D-AA. Two methods, nonenzymatic and enzymatic, were applied to determination of free and total D-AA, respectively, in oyster samples. The D-AA contents were in the range of 0.14 to 4.32 mg/L for milk samples and 0.80 to 15.9 mg/g for oyster samples, with relative standard deviations lower than 10% (n = 4), except for D-Tyr. In general, mean recoveries were greater than 90% with relative standard deviations lower than 9% (n = 4) at concentration levels from 0.055 to 0.426 mg/L for milk samples and 0.348 to 1.10 mg/ g for oyster samples. [ABSTRACT FROM AUTHOR]

Prolyl hydroxylase domain 2 (PHD2) is a key enzyme regulating the expression of hypoxia inducible factor (HIF). Its inhibitors can improve the expression of HIF and downstream genes, which can treat hypoxia-related diseases. Therefore, the establishment of a reliable PHD2 inhibitors screening method is of great significance for the drug development of hypoxia-related diseases. In this work, an accurate, rapid, and simple screening method for PHD2 inhibitors was introduced by capillary zone electrophoresis (CZE). In order to improve the detection sensitivity, the derivative reaction of α-ketoglutaric acid (α-OG) and 1,2-diaminobenzene (OPD) was used to enhance the UV absorption of α-OG (the substrate in the enzymatic reaction). The CZE method selected 20 mM Na 2 B 4 O 7 buffer (pH 9.0) as the separation buffer, +25 kV as the separation voltage, 25°C as the cartridge temperature, and 210 nm as the detection wavelength. Under this condition, the analysis of a single sample can be realized within 9 min. Compared with the existing reported methods, the present work can directly screen the PHD2 inhibitory activity of traditional Chinese medicine (TCM) extracts, which is of significance for the target-purification of bioactive individual compounds from TCMs. Under the optimal conditions, the PHD2 inhibitor screening platform was successfully established, and it was found that 70% methanol/water extracts of Astragali Radix and Codonopsis pilosula had good PHD2 inhibitory activity. Furthermore, the present work provides a novel approach for screening the PHD2 inhibitory activity of TCM extracts and the discovery of anti-hypoxia bioactive compounds., (© 2022 Wiley-VCH GmbH.)

Herein, a facile and fast surface-enhanced Raman scattering (SERS) method with ratiometric strategy was developed for detection of 4-methylimidazole (4-MI). Via a chemical derivatization reaction with 3-amino-5-mercapto-1,2,4-triazole (AMTA) diazonium salts, 4-MI could be converted to SERS-sensitive species. The SERS intensity ratio between the peaks at 1243 cm−1 and 1110 cm−1 (I 1243 /I 1110) was used for the quantification of 4-MI. In addition, the method sensitivity was further improved by the aggregation of beta-cyclodextrin-modified Ag nanoparticles (beta-CD-AgNPs). Under the optimal conditions, the limit of detection (LOD) and the limit of quantification (LOQ) for 4-MI were 1.7 nM (S/N = 3) and 5.7 nM (S/N = 10), respectively. The relative standard deviation (RSD) for 0.5 μM 4-MI was 8.2% (n = 20). This method was successfully used for the determination of 4-MI in cola samples with recoveries ranging from 92% to 106%. The present method is convenient, sensitive, selective, reliable and may have a promising application in determination of the compounds with an imidazole ring containing active hydrogen atoms. [Display omitted] • Trace 4-methylimidazole (4-MI) was determined by combining the AMTA-based derivatization reaction and SERS. • The method sensitivity was further improved by the aggregation of beta-cyclodextrin-modified Ag nanoparticles (beta-CD-AgNPs). • The SERS intensity ratio between the specific peaks was used for the quantification. • This method exhibits high sensitivity and selectivity for the determination of 4-MI in cola samples. [ABSTRACT FROM AUTHOR]

• An efficient method for the determination of benzenemethanethiol in sesame-flavoure baijiu was established. • The method of derivatization reaction made the quantification more accurate. • Benzenemethanethiol had an important contribution to the aroma of sesame-flavor baijiu. Chinese sesame-flavour baijiu (CSB) is one of aroma types discovered after the founding of China. Sulfur-containing compounds have low content in CSB but play an important role. This study developed a quantitative method by derivatization reaction combined LC-MS/MS for the determination of benzenemethanethiol (BM), which has a roasted aroma in CSB. Under the optimized conditions, the LOD and LOQ of BM were 11.73 ng L−1 and 39.09 ng L−1, respectively. The recovery yield of the derivatization product ranged from 82.12% to 93.99%. The content of BM in 4 CSBs were 150.22–860.40 ng L−1. To confirm the contribution of BM to the overall aroma of CSB, aroma recombination experiments and omission experiments were carried out. Compared with that of the simulated baijiu sample without BM, the roasted aroma of the simulated baijiu sample containing BM was enhanced. Omission experiments showed that BM made important contributions to the overall aroma of CSB. [ABSTRACT FROM AUTHOR]

• The esterification reaction of α-lipoic acid with 4-methoxybenzyl alcohol was studied. • The analytical usefulness of obtained ester was evaluated. • The GC–MS procedure was applied for determination of α-lipoic acid amount in real samples. The presented work is aimed to synthesize a new UV active derivative of α-lipoic acid (ALA) by its esterification with 4-methoxybenzyl alcohol (4-MBA, anise alcohol). The formation of ester was confirmed by 1HNMR, FTIR and UV spectroscopy. The analytical usefulness of the obtained compound for quantification of ALA in food items was examined using HPLC-UV and GC–MS systems. It was found that it is possible to assay ALA in the ester form in the concentration ranges: 5·10−6–1·10−4 mol L−1 by HPLC-UV and 1∙10−7–5∙10−5 mol L−1 by GC–MS techniques. The GC–MS procedure was applied for the determination of ALA in the food samples. [ABSTRACT FROM AUTHOR]