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A multiresidue method based on QuEChERS extraction followed liquid chromatography coupled with tandem mass spectrometry was developed and validated for the determination of 42 pesticides in marijuana. Less than 6 min is required for detection of all species. By using original QuEChERS, the sample preparation is also fast and simple. In the range from 1.0 to 50 μg kg -1 , the coefficients of determination (r 2 ) were greater than 0.980, and relative standard deviations for replicate injections were lower than 4.6%. The limit of detection (LOD) and limit of quantification (LOQ) were lower than 0.32 μg kg -1 and 1.07 μg kg -1 , respectively. Precision and accuracy were verified through recovery of spiked samples at three distinct levels of concentration (1.0, 5.0, and 50.0 μg kg -1 ) in five replicates. Recovery values ranged from 82 to 119% with RSD lower than 6%. The method was applied to the detection of pesticide residues in six marijuana samples seized by the Police of Rio de Janeiro, Brazil, where imidacloprid, metazachlor, buprofezin, and metalaxyl were found in four of them., (Copyright © 2019 Elsevier B.V. All rights reserved.)

A capillary electrophoresis with diode array and tandem mass spectrometry detection (CE-UV-MS/MS) method has been developed for the targeted assessment of cardiovascular biomarkers candidates, trimethylamine-N-Oxide (TMAO) and l-carnitine, and creatinine in human urine samples. The dual detection was applied due to the high concentration of creatinine (monitored by UV detection at 200 nm) in relation to TMAO and l-carnitine (quantified by selected reaction monitoring (SRM) mass spectrometry), in human urine. All instrumental parameters, sheath liquid (SHL) and background electrolyte (BGE) compositions were optimized with a pool of urine provided by adult healthy volunteers and evaluated by signal-to-noise ratio (SNR) and peak shape of TMAO. The compositions for the optimized BGE was formic acid at concentration of 0.10 mol L -1 , and for SHL was 70:30 MeOH:H 2 O containing 0.05% (v/v) formic acid, delivered at a flow rate of 5 μL min -1 . Limits of detection for TMAO, l-carnitine and creatinine were 0.76, 0.54 and 303 μmol L -1 , respectively. Limits of quantification were 2.5, 1.8 and 1000 μmol L -1 , respectively. Linearity was evaluated by ANOVA and presented R 2 from 0.993 to 0.997. Precision and accuracy were evaluated at three concentration levels. Coefficients of variation (CV) from 1 to 21% were obtained for the intra-day precision evaluation and from 2 to 16% for the inter-day precision evaluation. The recovery ranged from 75 to 116%. Quantitation of TMAO and l-carnitine in infarcted patients urine in comparison to healthy individuals indicated a 2.2 fold increase of TMAO and a 7.0 fold increase of l-carnitine. These results showed the potential applicability of the proposed method for the evaluation of TMAO and l-carnitine in urine within a panel of candidate metabolites in targeted metabolomics studies of cardiovascular diseases among other conditions., (Copyright © 2018 Elsevier B.V. All rights reserved.)

A capillary electrophoresis-tandem mass spectrometry (CE-MS/MS) method for the simultaneous assessment of nine biogenic amines (spermine, spermidine, putrescine, cadaverine, histamine, phenylethylamine, tryptamine, tyramine, and urocanic acid) in commercial samples of beer and wine is introduced. The samples were submitted to a simple clean-up step with poly(vinylpolypyrrolidone) followed by filtration. Electrophoretic separation in a polyvinyl alcohol (PVA)-coated capillary using 0.5 mol L(-1) acetic acid (pH 2.5) as background electrolyte and detection by electrospray-tandem mass spectrometry was employed. The range of the correlation coefficients of the calibration curves of the analyzed compounds was 0.996-0.999, and the limits of detection and limits of quantification were in the range of 1-2 μg L(-1) and 3-8 μg L(-1), respectively. The recovery values for samples spiked at three concentration levels (0.2, 0.5, and 1.0 mg L(-1)) ranged from 87 to 113% with standard deviation not greater than 5.8%. The use of a PVA-coated silica capillary allows suppressing the electroosmotic flow and, consequently, increasing of the separation efficiency. The method was successfully used to determine biogenic amines in commercial samples of beer and wine., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C(4)D) was used for fast, simultaneous determination of dipyrone (DIP), caffeine (CAF), and acetylsalicylic acid (ASA). In the same run and in less than 1min, the degradation products from DIP and ASA were also detected. In addition, the usage of the CE-C(4)D system allowed, for the first time, the detection of methylamine as a degradation product of DIP. Capillary electrophoresis with electrospray mass spectrometry experiments were carried out in order to confirm the formation of methylamine. The limits of detection by CE-C(4)D were 5, 5, and 6μmolL(-1) for CAF, DIP, and ASA, respectively. The proposed method was applied to the analysis of these compounds in pharmaceutical formulations with similar results to those achieved by HPLC (p<0.05)., (Copyright © 2013 Elsevier B.V. All rights reserved.)

A new prototype of contactless conductivity detector, smaller and easier to operate than the former version, is described. For a fused-silica capillary with 142-microm wall thickness and voltages up to 25 kV, it can be placed at the low- or high-voltage end of the column. This feature allowed implementation of an apparatus with sample introduction at the grounded end of the column. The input signal is an important parameter for determining the signal-to-noise ratio (S/N) of the detection system. An optimization procedure of its amplitude and frequency is proposed. Although the SIN must be determined by introduction of actual samples, the operating conditions can be optimized merely by changing the signal parameters and by using a mathematical procedure. Thus, an easy and fast optimization routine can be carried out. Mathematical and instrumental backgrounds are discussed, and experimental support of the technique's effectiveness is presented.