Analytical study on ethephon residue determination in water by ion-pairing liquid chromatography/tandem mass spectrometry

A detailed analytical study on ethephon residue determination in water, making use of ion-pairing liquid chromatography coupled to electrospray tandem mass spectrometry (LC/MS/MS), has been carried out. Ethephon is a plant growth regulator, highly polar, which is typically present in aqueous solution in anionic form due to its acid character. Both its extraction and pre-concentration from water samples and its chromatographic retention are difficult. Several approaches for sample pretreatment have been tested including direct injection into the chromatographic system, on-line solid phase extraction (SPE) and off-line SPE, with the best results being obtained after off-line SPE, using Oasis MAX cartridges (mixed-mode strong anion-exchange). After testing several ion-pairing reagents, tetrabuthylammonium acetate (TBA) was selected. This was added to the samples before LC/MS/MS analysis to facilitate ethephon chromatographic retention. The acquisition of several specific MS/MS transitions together with the evaluation of their relative intensity ratios allowed the reliable confirmation of the analyte in samples. The optimised approach was tested in low-salinity water spiked at 0.1 µg L−1 level with satisfactory recovery, and a limit of detection of 0.02 µg L−1. To this purpose, the water sample was partially de-ionised in an initial stage, in order to remove major ions that would have interfered in analyses. The application of this methodology to more saline/complex water samples, as surface or wastewater, was problematic and a thorough optimisation of the de-ionisation conditions would be required

Liquid chromatography coupled to tandem mass spectrometry for the residue determination of ethylenethiourea (ETU) and propylenethiourea (PTU) in water

Ethylenethiourea (ETU) and propylenethiourea (PTU) are the main degradation products of dithiocarbamates fungicides, which are widely used in agriculture from several years ago. Their determination in water at low concentrations (e.g. sub-ppb levels) is highly problematic due to their polar character and low molecular size. In the present study, two analytical methodologies have been developed and compared for the selective and sensitive determination of ETU and PTU in various types of waters. Both approaches are based on liquid chromatography coupled to tandem mass spectrometry (LC–MS/MS) with electrospray ionization, using triple quadrupole analyzer. Whereas the first methodology used an on-line solid-phase extraction (SPE) step in order to reach the adequate sensitivity, the second one avoided sample treatment and was based on direct injection into an ultra high performance liquid chromatography (UHPLC–MS/MS) system, making use of a new-generation instrument in order to reach sub-ppb analyte levels in water. Strong matrix effects (typically leading to signal enhancement) were observed for most of the evaluated waters, especially when applying the on-line SPE method, surely due to the higher amount of sample injected into the system. The use of the own analyte (ETU-d4) as isotope-labelled internal standard (ILIS) allowed to compensate these effects and to achieve an accurate ETU quantification at low concentrations. Moreover, three simultaneous transitions, operating in selected reaction monitoring mode, were acquired for both ETU and ETU-d4. This fact together with the evaluation of their relative intensity ratios assured the reliable identification of the analyte in the water samples. The two optimized methodologies were validated by analysis of six different samples (two drinking water, two groundwater and two surface water), spiked at two levels (0.1 and 1.0 μg/L), and analyzed each in quintuplicate. Satisfactory accuracy and precision, with recoveries ranging from 73 to 104% and RSDs lower than 20%, were obtained for ETU. Limits of detection for ETU were found to be 0.058 μg/L and 0.027 μg/L with direct injection and with the on-line methodology, respectively. No satisfactory recoveries were obtained, in general, for PTU despite using its own deuterium-labelled molecule for matrix effects correction. Notable differences in the chemical behaviour between PTU and PTU-d6 were observed, which lead to significant variation in their chromatographic retention time and ionization efficiency. Thus, no satisfactory correction of matrix effects could be reached illustrating that the use of deuterated ILIS can be problematic in some particular cases. Despite the poor correction, a semi-quantitative analysis would be feasible for PTU at sub-ppb levels in water. To the best of our knowledge, this is the first article reporting the use of LC–MS/MS for the trace level determination of these problematic analytes in water

Determination of eight nitrosamines in water at the ng L−1 levels by liquid chromatography coupled to atmospheric pressure chemical ionization tandem mass spectrometry

In this work, we have developed a sensitive method for detection and quantification of eight N-nitrosamines, N-nitrosodimethylamine (NDMA), N-nitrosomorpholine (NMor), N-nitrosomethylethylamine (NMEA), N-nitrosopirrolidine (NPyr), N-nitrosodiethylamine (NDEA), N-nitrosopiperidine (NPip), N-nitroso-n-dipropylamine (NDPA) and N-nitrosodi-n-butylamine (NDBA) in drinking water. The method is based on liquid chromatography coupled to tandem mass spectrometry, using atmospheric pressure chemical ionization (APCI) in positive mode with a triple quadrupole analyzer (QqQ). The simultaneous acquisition of two MS/MS transitions in selected reaction monitoring mode (SRM) for each compound, together with the evaluation of their relative intensity, allowed the simultaneous quantification and reliable identification in water at ppt levels. Empirical formula of the product ions selected was confirmed by UHPLC-(Q)TOF MS accurate mass measurements from reference standards. Prior to LC–MS/MS QqQ analysis, a preconcentration step by off-line SPE using coconut charcoal EPA 521 cartridges (by passing 500 mL of water sample) was necessary to improve the sensitivity and to meet regulation requirements. For accurate quantification, two isotope labelled nitrosamines (NDMA-d6 and NDPA-d14) were added as surrogate internal standards to the samples. The optimized method was validated at two concentration levels (10 and 100 ng L−1) in drinking water samples, obtaining satisfactory recoveries (between 90 and 120%) and precision (RSD < 20%). Limits of detection were found to be in the range of 1–8 ng L−1. The described methodology has been applied to different types of water samples: chlorinated from drinking water and wastewater treatment plants (DWTP and WWTP, respectively), wastewaters subjected to ozonation and tap waters.This work has been developed under financial support of the Ministry of Education and Science, Spain (CTM2006-06417

Determination of 17b-estradiol and 17a-ethinylestradiol in water at sub-ppt levels by liquid chromatography coupled to tandem mass spectrometry

Steroid estrogens are a group of endocrine disrupting compounds (EDCs) excreted in human urine mainly as glucuronide or sulfate conjugates, which might be converted back into the free estrogens in water. The natural estrogen 17b-estradiol (E2) and the synthetic one 17a-ethinylestradiol (EE2) are of particular concern due to their strong estrogenic activity. The main environmental source of estrogen exposure is treated wastewaters, with the associated risk of releasing these pollutants to surface waters and even reaching finished drinking waters. In this work, we have developed and validated (at 0.1 and 1 ng L 1 levels) a robust and sensitive method based on Ultra-High Performance Liquid Chromatography (UHPLC) coupled to MS/MS for the reliable identi fication and quantification of E2 and EE2 in surface waters. Several sulfate conjugates have been also included into the methodology. A re-concentration step based on off-line solid-phase extraction with Oasis HLB cartridges has been optimized prior to the UHPLC-(ESI)MS/MS determination with a last-generation triple quadrupole analyzer. Two isotopelabelled analytes (E2-d4 and EE2-d4) have been used as surrogate standards to ensure an accurate quantification, achieving very low limits of detection for E2 (0.06 ng L 1 ) and EE2 (0.02 ng L 1 ). Several surface waters and influents and effluents from wastewater treatment plants have been analyzed to test the method applicability

Liquid chromatography coupled to tandem mass spectrometry for the residue determination of ethylenethiourea (ETU) and propylenethiourea (PTU) in water

Ethylenethiourea (ETU) and propylenethiourea (PTU) are the main degradation products of dithiocarbamates fungicides, which are widely used in agriculture from several years ago. Their determination in water at low concentrations (e.g. sub-ppb levels) is highly problematic due to their polar character and low molecular size. In the present study, two analytical methodologies have been developed and compared for the selective and sensitive determination of ETU and PTU in various types of waters. Both approaches are based on liquid chromatography coupled to tandem mass spectrometry (LC–MS/MS) with electrospray ionization, using triple quadrupole analyzer. Whereas the first methodology used an on-line solid-phase extraction (SPE) step in order to reach the adequate sensitivity, the second one avoided sample treatment and was based on direct injection into an ultra high performance liquid chromatography (UHPLC–MS/MS) system, making use of a new-generation instrument in order to reach sub-ppb analyte levels in water. Strong matrix effects (typically leading to signal enhancement) were observed for most of the evaluated waters, especially when applying the on-line SPE method, surely due to the higher amount of sample injected into the system. The use of the own analyte (ETU-d4) as isotope-labelled internal standard (ILIS) allowed to compensate these effects and to achieve an accurate ETU quantification at low concentrations. Moreover, three simultaneous transitions, operating in selected reaction monitoring mode, were acquired for both ETU and ETU-d4. This fact together with the evaluation of their relative intensity ratios assured the reliable identification of the analyte in the water samples. The two optimized methodologies were validated by analysis of six different samples (two drinking water, two groundwater and two surface water), spiked at two levels (0.1 and 1.0 μg/L), and analyzed each in quintuplicate. Satisfactory accuracy and precision, with recoveries ranging from 73 to 104% and RSDs lower than 20%, were obtained for ETU. Limits of detection for ETU were found to be 0.058 μg/L and 0.027 μg/L with direct injection and with the on-line methodology, respectively. No satisfactory recoveries were obtained, in general, for PTU despite using its own deuterium-labelled molecule for matrix effects correction. Notable differences in the chemical behaviour between PTU and PTU-d6 were observed, which lead to significant variation in their chromatographic retention time and ionization efficiency. Thus, no satisfactory correction of matrix effects could be reached illustrating that the use of deuterated ILIS can be problematic in some particular cases. Despite the poor correction, a semi-quantitative analysis would be feasible for PTU at sub-ppb levels in water. To the best of our knowledge, this is the first article reporting the use of LC–MS/MS for the trace level determination of these problematic analytes in water

Strategies to Characterize Polar Organic Contamination in Wastewater: Exploring the Capability of High Resolution Mass Spectrometry

Wastewater effluents contain a multitude of organic contaminants and transformation products, which cannot be captured by target analysis alone. High accuracy, high resolution mass spectrometric data were explored with novel untargeted data processing approaches (enviMass, nontarget, and RMassBank) to complement an extensive target analysis in initial “all in one” measurements. On average 1.2% of the detected peaks from 10 Swiss wastewater treatment plant samples were assigned to target compounds, with 376 reference standards available. Corrosion inhibitors, artificial sweeteners, and pharmaceuticals exhibited the highest concentrations. After blank and noise subtraction, 70% of the peaks remained and were grouped into components; 20% of these components had adduct and/or isotope information available. An intensity-based prioritization revealed that only 4 targets were among the top 30 most intense peaks (negative mode), while 15 of these peaks contained sulfur. Of the 26 nontarget peaks, 7 were tentatively identified via suspect screening for sulfur-containing surfactants and one peak was identified and confirmed as 1,3-benzothiazole-2-sulfonate, an oxidation product of a vulcanization accelerator. High accuracy, high resolution data combined with tailor-made nontarget processing methods (all available online) provided vital information for the identification of a wider range of heteroatom-containing compounds in the environment

Development of sensitive and rapid analytical methodology for food analysis of 18 mycotoxins included in a total diet study

A rapid and sensitive method for the determination of 18 mycotoxins in 24 different food matrices has been developed and validated. With the exception of beverages and oil samples, a simple extraction with acetonitrile:water 80:20 (0.1% formic acid) was applied. Fruit juice, wine and beer samples were simply diluted with water containing 0.1% formic acid. Oil samples were partitioned with acetonitrile/hexane in order to remove fats. Analyses were made by ultra-high performance liquid chromatography (UHPLC) coupled to tandem mass spectrometry with triple quadrupole. Validation was carried out in all selected matrices using blank samples spiked at two analyte concentrations. Extraction recoveries between 70 and 120% and relative standard deviations lower than 20% were obtained for the wide majority of analyte–matrix combinations. Matrix-matched calibration was used for a correct quantification in order to compensate for matrix effects. Limits of quantification were lower than maximum permitted levels for every regulated mycotoxin–matrix combination. The acquisition of three SRM transitions per compound allowed the unequivocal confirmation of positive samples, supported by the accomplishment of ion intensity ratios and retention time when compared with reference standards. The developed methodology was applied to the analysis of 240 samples within a total diet study performed at Comunidad Valenciana (Spain). The most frequently found mycotoxins were deoxynivalenol, fumonisin B1, ochratoxin A and zearalenone at low g kg−1 levels, mainly in bread, breakfast cereals and beer

Effects of pre-operative isolation on postoperative pulmonary complications after elective surgery: an international prospective cohort study an international prospective cohort study

We aimed to determine the impact of pre-operative isolation on postoperative pulmonary complications after elective surgery during the global SARS-CoV-2 pandemic. We performed an international prospective cohort study including patients undergoing elective surgery in October 2020. Isolation was defined as the period before surgery during which patients did not leave their house or receive visitors from outside their household. The primary outcome was postoperative pulmonary complications, adjusted in multivariable models for measured confounders. Pre-defined sub-group analyses were performed for the primary outcome. A total of 96,454 patients from 114 countries were included and overall, 26,948 (27.9%) patients isolated before surgery. Postoperative pulmonary complications were recorded in 1947 (2.0%) patients of which 227 (11.7%) were associated with SARS-CoV-2 infection. Patients who isolated pre-operatively were older, had more respiratory comorbidities and were more commonly from areas of high SARS-CoV-2 incidence and high-income countries. Although the overall rates of postoperative pulmonary complications were similar in those that isolated and those that did not (2.1% vs 2.0%, respectively), isolation was associated with higher rates of postoperative pulmonary complications after adjustment (adjusted OR 1.20, 95%CI 1.05–1.36, p = 0.005). Sensitivity analyses revealed no further differences when patients were categorised by: pre-operative testing; use of COVID-19-free pathways; or community SARS-CoV-2 prevalence. The rate of postoperative pulmonary complications increased with periods of isolation longer than 3 days, with an OR (95%CI) at 4–7 days or ≥ 8 days of 1.25 (1.04–1.48), p = 0.015 and 1.31 (1.11–1.55), p = 0.001, respectively. Isolation before elective surgery might be associated with a small but clinically important increased risk of postoperative pulmonary complications. Longer periods of isolation showed no reduction in the risk of postoperative pulmonary complications. These findings have significant implications for global provision of elective surgical care. We aimed to determine the impact of pre-operative isolation on postoperative pulmonary complications after elective surgery during the global SARS-CoV-2 pandemic. We performed an international prospective cohort study including patients undergoing elective surgery in October 2020. Isolation was defined as the period before surgery during which patients did not leave their house or receive visitors from outside their household. The primary outcome was postoperative pulmonary complications, adjusted in multivariable models for measured confounders. Pre-defined sub-group analyses were performed for the primary outcome. A total of 96,454 patients from 114 countries were included and overall, 26,948 (27.9%) patients isolated before surgery. Postoperative pulmonary complications were recorded in 1947 (2.0%) patients of which 227 (11.7%) were associated with SARS-CoV-2 infection. Patients who isolated pre-operatively were older, had more respiratory comorbidities and were more commonly from areas of high SARS-CoV-2 incidence and high-income countries. Although the overall rates of postoperative pulmonary complications were similar in those that isolated and those that did not (2.1% vs 2.0%, respectively), isolation was associated with higher rates of postoperative pulmonary complications after adjustment (adjusted OR 1.20, 95%CI 1.05–1.36, p = 0.005). Sensitivity analyses revealed no further differences when patients were categorised by: pre-operative testing; use of COVID-19-free pathways; or community SARS-CoV-2 prevalence. The rate of postoperative pulmonary complications increased with periods of isolation longer than 3 days, with an OR (95%CI) at 4–7 days or ≥ 8 days of 1.25 (1.04–1.48), p = 0.015 and 1.31 (1.11–1.55), p = 0.001, respectively. Isolation before elective surgery might be associated with a small but clinically important increased risk of postoperative pulmonary complications. Longer periods of isolation showed no reduction in the risk of postoperative pulmonary complications. These findings have significant implications for global provision of elective surgical care

Global variation in postoperative mortality and complications after cancer surgery: a multicentre, prospective cohort study in 82 countries

© 2021 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY-NC-ND 4.0 licenseBackground: 80% of individuals with cancer will require a surgical procedure, yet little comparative data exist on early outcomes in low-income and middle-income countries (LMICs). We compared postoperative outcomes in breast, colorectal, and gastric cancer surgery in hospitals worldwide, focusing on the effect of disease stage and complications on postoperative mortality. Methods: This was a multicentre, international prospective cohort study of consecutive adult patients undergoing surgery for primary breast, colorectal, or gastric cancer requiring a skin incision done under general or neuraxial anaesthesia. The primary outcome was death or major complication within 30 days of surgery. Multilevel logistic regression determined relationships within three-level nested models of patients within hospitals and countries. Hospital-level infrastructure effects were explored with three-way mediation analyses. This study was registered with ClinicalTrials.gov, NCT03471494. Findings: Between April 1, 2018, and Jan 31, 2019, we enrolled 15 958 patients from 428 hospitals in 82 countries (high income 9106 patients, 31 countries; upper-middle income 2721 patients, 23 countries; or lower-middle income 4131 patients, 28 countries). Patients in LMICs presented with more advanced disease compared with patients in high-income countries. 30-day mortality was higher for gastric cancer in low-income or lower-middle-income countries (adjusted odds ratio 3·72, 95% CI 1·70–8·16) and for colorectal cancer in low-income or lower-middle-income countries (4·59, 2·39–8·80) and upper-middle-income countries (2·06, 1·11–3·83). No difference in 30-day mortality was seen in breast cancer. The proportion of patients who died after a major complication was greatest in low-income or lower-middle-income countries (6·15, 3·26–11·59) and upper-middle-income countries (3·89, 2·08–7·29). Postoperative death after complications was partly explained by patient factors (60%) and partly by hospital or country (40%). The absence of consistently available postoperative care facilities was associated with seven to 10 more deaths per 100 major complications in LMICs. Cancer stage alone explained little of the early variation in mortality or postoperative complications. Interpretation: Higher levels of mortality after cancer surgery in LMICs was not fully explained by later presentation of disease. The capacity to rescue patients from surgical complications is a tangible opportunity for meaningful intervention. Early death after cancer surgery might be reduced by policies focusing on strengthening perioperative care systems to detect and intervene in common complications. Funding: National Institute for Health Research Global Health Research Unit