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Wine samples collected during the winemaking process have been analyzed employing a previously optimized UHPLC-FD method, determining their biogenic amines and amino acids profile. The results obtained have been submitted to a statistical analysis from which it was extracted that the most influential analyte was tyrosine. Thanks to its fluorescence, a method for its determination by excitation-emission matrices has been proposed. The accuracy of the method has been checked by means of Elliptical Joint Confidence Region test. The winemaking process has been monitored with this method, obtaining a faster and cheaper way to follow the process., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

A method for the determination of several tricyclic antidepressants (imipramine, desipramine, amitriptyline, nortriptyline, clomipramine, norclomipramine, doxepine and nordoxepine) in breast milk has been developed. This assay consists of a common extraction process in an organic phase, which is evaporated until dried and finally reconstituted in the appropriate buffer for injection in a capillary electrophoresis system. The capillary electrophoresis method used is an "acetonitrile stacking" method previously reported for determining these drugs in serum samples. The method developed was applied to the analysis of these compounds in human breast milk at different concentration levels (50, 100 and 200 ppb of the TCAs hydrochlorides). An interference study of some ansiolitic drugs such as lorazepam and alprazolam was made.

A robustness study for a sensitive-stacking capillary electrophoresis method based on "acetonitrile-stacking" was carried out. Ten variables (pH, acetonitrile and triethanolamine in the buffer, injection time, injection pressure, acetonitrile and NaCl in the sample, capillary and tray temperature and separation voltage), whose levels were varied by 10% around the nominal level, were examined by a Plackett-Burman design (two-level design). The effects on corrected peak area and resolution (responses) were calculated and interpreted using three statistical approaches: dummy variables, distribution effects (Dong's algorithm) and calibration curve. Dong's method was found to be the most suitable to evaluate the robustness, since it considers qualitative (resolution) and quantitative (corrected peak area) responses and does not need a minimum number of dummy variables in the experimental design. From these studies, we can deduce that the first four variables were significant at 10% around the nominal level, and therefore a new design was made with those four variables at 5% nominal level. Then, only two variables proved to be significant for the resolution between some peaks, so the system suitability test limits were defined for these resolutions.

The work presented here explores the possibilities of the electrokinetic injection (EK) to achieve sensitive methods for the determination of tricyclic antidepressants in biological samples (serum). The addition of ACN to the sample, with high content in salts, causes stacking at the tip of the capillary, in a similar way as for hydrodynamic injection. An experimental design with the response surface methodology has been used to find the optimum composition of the matrix of the sample (sodium chloride and ACN percentages) and the conditions for the EK (water-plug length, time, and voltage of injection) in few experiments. The composition of the separation buffer was the same as utilized in a previous paper. The use of a bubble capillary to reach lower detection limits implies a loss of the resolution and requires a new optimization. Finally, a comparison between electrokinetic and hydrodynamic injections is made.

A spectrofluorimetric method has been developed for the quantitative determination of mefenamic, flufenamic, and meclofenamic acids in urine samples. The method is based on second-order data multivariate calibration (unfolded partial least squares (unfolded-PLS), multi-way PLS (N-PLS), parallel factor analysis (PARAFAC), self-weighted alternating trilinear decomposition (SWATLD), and bilinear least squares (BLLS)). The analytes were extracted from the urine samples in chloroform prior to the determination. The chloroform extraction was optimized for each analyte, studying the agitation time and the extraction pH, and the optimum values were 10 minutes and pH 3.5, respectively. The concentration ranges in chloroform solution of each of the analytes, used to construct the calibration matrix, were selected in the ranges from 0.15 to 0.8 microg mL-1 for flufenamic and meclofenamic acids and from 0.25 to 3.0 microg mL-1 for mefenamic acid. The combination of chloroform extraction and second-order calibration methods, using the excitation-emission matrices (EEMs) of the three analytes as analytical signals, allowed their simultaneous determination in human urine samples, in the range of approximately 80 mg L-1 to 250 mg L-1, with satisfactory results for all the assayed methods. Improved results over unfolded-PLS and N-PLS were found with PARAFAC, SWATLD, and BLLS, methods that exploit the second-order advantage.

Stacking methods are very important in overcoming the poor detection limits in capillary electrophoresis (CE). In this paper, the separation and determination of several tricyclic antidepressants by a stacking method is described. The inclusion of acetonitrile (ACN) in the sample causes stacking (transient pseudoisotachophoresis) especially in presence of sodium chloride. An experimental design (central composite design) together with the response surface methodology has been used to find the optimum composition of the separation buffer and the optimal stacking conditions in few experiments. The response functions used are the product of the total resolution by the number of peaks, for the optimization of the separation buffer, and the product of the total resolution by the mean of the peak heights, for the optimization of the stacking conditions. About 28% of the capillary volume is loaded with sample. The calibration curves are linear over the working range (50-300 ng/mL). With a bubble capillary, the limits of detection (LODs) are in the order of 5 ng/mL. For the analysis of serum samples, enrichment with sodium chloride and the protein precipitation with ACN are enough to avoid interferences and to get stacking. Recoveries between 91.6 and 104% and RSD between 0.6 and 12% are obtained in the analysis of samples of lyophilized human serum and non-lyophilized human serum, spiked with the drugs.

A semiautomatic extraction-fluorimetric method for the determination of tricyclic antidepressant drugs (TCAs) based in the formation of ion pairs with 9,10-dimethoxyanthracene-2-sulphonate (DMAS) has been developed. The aqueous solutions of the TCAs (imipramine, desipramine, amitriptyline, nortriptyline, clomipramine or doxepine) are injected into a carrier composed by DMAS in an acid medium and the ion pair formed is extracted into dichloromethane where the fluorescence is measured. An experimental design (Central Composite Design) together with the Response Surface Methodology has been used to find the optimal instrumental FIA and chemical variables. We have considered as the response function the product of the peak height by the sampling frequency. The calibration curves were linear over the working range (0.25-3.00mgL(-1)). The limits of detection were lower than 0.30mgL(-1). The method has been satisfactorily applied to the determination of imipramine, amitriptyline, clomipramine and doxepin in pharmaceutical preparations.

A selective and reliable extraction procedure was developed and validated to determine multiclass pesticide residues in lyophilized agricultural plants by low-pressure gas chromatography coupled with tandem mass spectrometry. The method is based on a rapid and simple extraction of the lyophilized sample with dichloromethane. The results were compared with those obtained by using fresh and naturally dried samples. Slightly better recoveries and precision values were obtained for the lyophilized samples. The application of the proposed methodology was tested by analyzing French bean plants from an agricultural area of Almería (Spain). The availability of this methodology, which is capable of detecting a high number of analytes in a single analysis, has priority in analyses for a large number of pesticides used on individual commodities.

Liquid chromatography with electrochemical detection has been used to determine various nitropesticides, DNOC, fenitrothion, and parathion (methyl and ethyl), and some of their main metabolites, 4-nitrophenol for parathion (methyl and ethyl) and 3-methyl-4-nitrophenol for fenitrothion, by using indirect detection. Analysis of them in river water samples has been performed without a preconcentration step. The recovery efficiencies of the tested compounds yielded values between 96 and 112% at the fortification level of 0.5 ppb in a river water sample, and their relative standard deviations were between 1 and 15%. The detection limits of these compounds ranged between 0.05 and 0.14 ppb.