Determination of monoamine neurotransmitters in zebrafish (Danio rerio) by gas chromatography coupled to mass spectrometry with a two-step derivatization.

A sensitive analytical method for the determination of monoamine neurotransmitters (MNTs) in zebrafish larvae was developed using gas chromatography coupled to mass spectrometry. Six MNTs were selected as target compounds for neurotoxicity testing. MNTs underwent a two-step derivatization with hexamethyldisilazane (HDMS) for O-silylation followed by N-methyl-bis-heptafluorobutyramide (MBHFBA) for N-perfluoroacylation. Derivatization conditions were optimized by an experimental design approach. Method validation showed linear calibration curves (r 2 > 0.9976) in the range of 1-100 ng for all the compounds. The recovery rates were between 92 and 119%. The method was repeatable and reproducible with relative standard deviations (RSD) in the range of 2.5-9.3% for intra-day and 4.8-12% for inter-day variation. The limits of detection and the limits of quantitation were 0.4-0.8 and 1.2-2.7 ng/mL, respectively. The method was successfully applied to detect and quantify trace levels of MNTs in 5-day-old zebrafish larvae that were exposed to low concentrations of neurotoxic chemicals such as pesticides and methylmercury. Although visual malformations were not detected, the MNT levels varied significantly during early zebrafish development. These results show that exposure to neurotoxic chemicals can alter neurotransmitter levels and thereby may influence early brain development. Graphical abstract ᅟ.

Impurities of Resorcinol Bis(diphenyl phosphate) in Plastics and Dust Collected on Electric/Electronic Material.

Resorcinol bis(diphenylphosphate) (RDP) is an organophosphorus flame retardant widely used in electric and electronic equipment. It has been detected in house dust of several European countries according to recent literature. Similar to other flame retardants, RDP formulations and products treated with RDP, such as plastics, can contain RDP impurities, byproducts and breakdown products. In this study, we use screening methods based on wide scope solvent extraction and high resolution time-of-flight mass spectrometry for the identification of RDP related compounds in products and in dust. We analyzed both plastics from electrical/electronic equipment that contained RDP and indoor dust collected on and around surfaces of this equipment. A variety of compounds, namely TPHP, hydroxylated TPHP and RDP (meta-HO-TPHP and meta-HO-RDP), dihydroxylated TPHP, RDP with the loss of a phenyl group (RDP-[Phe]) and RDP oligomers were detected in plastics containing high levels of RDP. Regarding dust samples collected on electronics, TPHP meta-HO-TPHP, meta-HO-RDP, RDP-[Phe] and RDP oligomers were detected. High concentrations of meta-HO-TPHP (20-14 227 ng/g), TPHP (222-50 728 ng/g) and RDP (23-29 118 ng/g) were found in many of the dust samples, so that these compounds seem to easily migrate into the environment. These RDP impurities, byproducts and breakdown products are for the first time reported in indoor dust. Meta-HO-TPHP could be relevant for future biomonitoring studies concerning flame retardants.

[Association between occupational stress and nicotine dependence in in health workers]. / Asociación entre estrés laboral y dependencia nicotínica en trabajadores de la salud.

Background: Stress is the result of the imbalance between the demands and pressures that the individual faces. Stress tests the individual's ability to cope with her activity, and this is a health problem for the worker. Objective: To explore the association between occupational stress and nicotine dependence in healthcare workers from the Family Medicine Unit No. 92 of the IMSS. Material and methods: Cross-sectional study that included 180 active smoking workers, occupational stress was evaluated with the Psychosomatic Problems for Occupational Stress questionnaire adapted by IMSS and nicotine dependence with the Fagerström questionnaire. Student's t tests and Fisher's Exact test were used. The statistical analysis was performed with the Stata 15 program. Results: The prevalence of occupational stress was 72.2% (42.8% mild, 20.6% moderate and 8.9% severe). Women presented greater work stress compared to men (76.1% vs. 56.0%; p = 0.008). Nicotine dependence was 49.4% mild, 35.6% moderate and 15.0% severe, the average of the Fagerström test was higher in women compared to men (3.75 vs. 2.83; p = 0.025), in addition an association was found between the work stress and nicotine dependence (p = 0.011). Conclusions: 72% of the workers presented work stress, in the same way the association between work stress and nicotine dependence was found. Identifying the main causes of work stress, together with the support of smoking cessation programs, would help in the well-being of health personnel in FMUs.

Introducción: el estrés es el resultado del desequilibrio entre las exigencias y presiones a las que se enfrenta el individuo. El estrés pone a prueba la capacidad del individuo para afrontar su actividad y esto supone un problema de salud para el trabajador. Objetivo: explorar la asociación entre el estrés laboral y la dependencia a la nicotina en una población de trabajadores de la salud de la Unidad de Medicina Familiar No. 92 del IMSS. Material y métodos: estudio transversal que incluyó a 180 trabajadores fumadores activos, el estrés laboral fue evaluado con el cuestionario de Problemas Psicosomáticos para Estrés Ocupacional adaptado por el IMSS y la dependencia a la nicotina con el cuestionario de Fagerström. Se utilizaron pruebas de t de Student y prueba exacta de Fisher, el análisis estadístico fue realizado con el programa Stata 15. Resultados: la prevalencia de estrés laboral fue de 72.2% (leve, 42.8%; moderada, 20.6%, y severa, 8.9%). Las mujeres presentaron mayor estrés laboral en comparación con los hombres (76.1% frente a 56.0%; p = 0.008). La dependencia a la nicotina fue leve, 49.4%; moderada, 35.6%, y severa, 15.0%. El promedio de la prueba de Fagerström fue mayor en mujeres en comparación con hombres (3.75 frente a 2.83; p = 0.025), además se encontró una asociación entre el estrés laboral y la dependencia a la nicotina (p = 0.011). Conclusiones: el 72% de los trabajadores presentaron estrés laboral, de igual modo se encontró la asociación entre el estrés laboral y la dependencia a la nicotina. Identificar las principales causas de estrés laboral junto con el apoyo de programas para dejar de fumar, ayudarían en el bienestar del personal de salud en las UMF.

Analysis of polycyclic aromatic hydrocarbons in aqueous samples by large volume injection gas chromatography-mass spectrometry using the through oven transfer adsorption desorption interface.

A new procedure for the determination of 17 polycyclic aromatic hydrocarbons (PAHs) in aqueous samples by large volume injection-gas chromatography-mass spectrometry (LVI-GC-MS) using the Through Oven Transfer Adsorption Desorption (TOTAD) interface with nitrogen for solvent elimination is developed and validated. Up to 75mL of aqueous samples were injected to be sure that good solvent elimination were achieved, although 500µL were sufficient to achieve the required sensitivity.The performance of the developed method can be considered good: the relative standard deviation (RSD), (n=3) was lower than 13.8% for all the target analytes, the concentration of each PAH being 0.25µgL(-1), the limit of detection and limit of quantitation ranged from 21.5 to 211.0 ng L(-1) and from 71.7 to 703.3ngL(-1) respectively, and the correlation coefficients (R(2)) were all higher than 0.9764 in the 1-16µgL(-1) range.

Use of nitrogen to remove solvent from through oven transfer adsorption desorption interface during analysis of polycyclic aromatic hydrocarbons by large volume injection in gas chromatography.

The through oven transfer adsorption desorption (TOTAD) interface allows large volume injection (LVI) in gas chromatography and the on-line coupling of liquid chromatography and gas chromatography (LC-GC), enabling the LC step to be carried out in normal as well as in reversed phase. However, large amounts of helium, which is both expensive and scarce, are necessary for solvent elimination. We describe how slight modification of the interface and the operating mode allows nitrogen to be used during the solvent elimination steps. In order to evaluate the performance of the new system, volumes ranging from 20 to 100µL of methanolic solutions of four polycyclic aromatic hydrocarbons (PAHs) were sampled. No significant differences were found in the repeatability and sensitivity of the analyses of standard PAH solutions when using nitrogen or helium. The performance using the proposed modification was similar and equally satisfactory when using nitrogen or helium for solvent elimination in the TOTAD interface. In conclusion, the use of nitrogen will make analyses less expensive.

Large volume injection in gas chromatography using the through oven transfer adsorption desorption interface operating under vacuum.

The present work describes a modification of the Through Oven Transfer Adsorption Desorption (TOTAD) interface, consisting of coupling a vacuum system to reduce the consumption of the helium needed to totally remove the eluent for large volume injection (LVI) in gas chromatography (GC). Two different retention materials in the liner of the TOTAD interface were evaluated: Tenax TA, which was seen to be unsuitable for working under vacuum conditions, and polydimethylsiloxane (PDMS), which provided satisfactory repeatability as well as a good sensitivity. No variability was observed in the retention times in either case. Solutions containing organophosphorous pesticides in two different solvents, a polar (methanol/water) and a non-polar (hexane) solvent, were used to evaluate the modification. The vacuum system coupled to the TOTAD interface allowed up to 90% helium to be saved without affecting the performance.

Analysis of wax esters in edible oils by automated on-line coupling liquid chromatography-gas chromatography using the through oven transfer adsorption desorption (TOTAD) interface.

An automated method for the direct analysis of wax esters in edible oils is presented. The proposed method uses the TOTAD (through oven transfer adsorption desorption) interface for the on-line coupling of normal phase liquid chromatography and gas chromatography. In this fully automated system, the oil with C32 wax ester as internal standard and diluted with heptane is injected directly with no sample pre-treatment step other than filtration. The proposed method allows analysis of different wax esters, and is simpler and faster than the European Union Official Method, which is tedious and time-consuming. The obtained results closely match the certified values obtained from the median of the analytical results of the inter-labs certification study. Relative standard deviations of the concentrations are less than 5%. The method is appropriate for routine analysis as it is totally automated.