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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.

[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]

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.)