Validation and estimation of uncertainty of an LC-MS/MS method for the simultaneous determination of 34 mycotoxins in cocoa beans.

The aim of this manuscript was to validate and apply an analytical methodology for the simultaneous determination of 34 mycotoxins in cocoa. The extraction method used in the tests was a liquid-liquid partition by NaCl addition with a freezing step followed by quantification using LC-MS/MS. The results were discussed based on national and international directives for food contaminants. The recoveries and precision were adequate, except for the mycotoxins ionized with the ammonium adduct (NH4+), E-cristinine and ß-ZOL. This result directly influenced the measurement uncertainty of these mycotoxins, because the precision and the correction factor of the recovery were the factors with the greatest impact on the uncertainty of the method. The evaluation of the matrix effect showed considerable signal suppression for 53 % of the evaluated mycotoxins. Nevertheless, the mycotoxins exhibited relatively low quantification limits, with values between 1 and 75 µg kg-1. The validated methodology was applied to 15 cocoa samples collected in warehouses in Brazil. Positive results were found for all the evaluated samples, in which nine toxins were detected out of the 34 investigated.

Simultaneous quantification of ethylene glycol and diethylene glycol in beer by gas chromatography coupled to mass spectrometry.

An analytical method for the simultaneous determination of ethylene glycol and diethylene glycol in beer was developed and validated according to current legislation. This method includes the application of sample dilution with ethanol followed by quantification using gas chromatography coupled to mass spectrometry. All figures of merit were within the limits established by regulation. The recoveries of the analytes, expressed as mean recovery, were between 91.9% and 108.9%. Precision, in terms of repeatability and intermediate precision, was established (relative standard deviations were lower than or equal to 10%). The limits of detection (10.0 and 5.0 mg.L-1 for ethylene glycol and diethylene glycol, respectively) and quantification (15.0 mg.L-1 for ethylene glycol and diethylene glycol) obtained were appropriate. Finally, the present method was applied for determination of ethylene glycol and diethylene glycol in 701 beer samples (from 67 different brands and 128 different labels), proving to be reliable.

Methodology development based on "dilute and shoot" and QuEChERS for determination of multiple mycotoxins in cocoa by LC-MS/MS.

This work proposes an extraction method based on the "dilute and shoot" approach and QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) for the simultaneous determination of 42 mycotoxins (34 quantified and 8 qualitatively studied) in dried cocoa bean samples. The purpose of the developed methodology was the reduction of co-extractives from the matrix and an efficient extraction without a cleanup step, and subsequent analysis by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). In order to obtain the best extraction conditions, gravimetric tests were performed and parameters that influenced the extraction efficiency were evaluated, such as the proportion of extraction phases, amount of salt, acidification, and extraction time. The performance of the developed method was evaluated to ensure its reliability. Considering the recovery range of 70-120% as an accuracy parameter, four of the mycotoxins under study (acetyl T-2, tenuazonic acid, wortmannin, and zearalenone) showed undesirable values at one of the levels evaluated. The repeatability of the method was assessed for 34 mycotoxins by the relative standard deviation (RSD%) of the responses, and all presented satisfactory values. The quantification limits ranged from 1.0 to 33.0 µg kg-1. Modification of the extraction methods made it possible to simultaneously analyze multiple mycotoxins, eliminating the need for the cleanup step, which led to analyte losses. The proposed methodology has a low cost, which makes it advantageous in routine analysis. It also has the potential for scope extension to cocoa-based foods, which are naturally exposed to a greater variety of mycotoxins. Graphical abstract.

A multi-residue method for the determination of pesticides in high water content matrices by gas chromatography-single quadrupole mass spectrometry with electron ionisation (EI-GC/MS).

An EI-GC/MS method for the determination of pesticide residues in vegetable matrices with high water content was validated using papaya samples. The validation of a multi-residue pesticide method was in agreement with national and international regulations enabling the Ministry of the Agriculture, Livestock and Food Supply of Brazil to cover a large number of matrices and pesticide residues in its monitoring and control programmes. The extraction used 60 mL of ethyl acetate and 30 g of sample previously processed. After extraction, clean-up of all the extracts was carried out by percolation through GBC cartridges. The samples were then injected in an EI-GC/MS system. Calibration curves were prepared in quadruplet by fortifying blank extracts with a standard solution containing all the pesticides studied at 0.000, 0.005, 0.010, 0.020, 0.030, 0.050, 0.080 and 0.100 mg kg(-1). For the recovery study, blank samples were fortified at 0.010, 0.020, 0.030, 0.050 and 0.080 mg kg(-1) and then submitted to the extraction procedure. The complete procedure was repeated over four different days by two analysts. The regression parameters of calibration curves were calculated for each validation day. Linearity, selectivity, specificity, robustness, limits of detection and quantification were also assessed. The uncertainty was estimated for each analyte at each spike level studied. The method had recoveries between 91% and 105% and precision results ≤ 20%. Limits of quantification were below or equal to the maximum residue limits (MRLs) regulated by Brazilian legislation. The MRLs of the selected pesticides are not regulated by CODEX Alimentarius. The results are also in agreement with SANCO/10684/2009.

A multi-residue method for the determination of 90 pesticides in matrices with a high water content by LC-MS/MS without clean-up.

A method using QuEChERS extraction and LC-MS/MS in electrospray positive ionisation mode was developed and validated for the analysis of 90 pesticides in a high water content matrix (tomato) in a single chromatographic run. To assess the intra-laboratory reproducibility of the method, validation was conducted on four different days by two different analysts. The validation data was treated using a spreadsheet developed in-house, which sets the most appropriate model for linear fit by determining whether the residuals of the calibration curves are homocedastic or heterocedastic. A statistical test for the significance of regression was also carried out. Calibration was always matrix-matched and the curves were obtained over the range 0.0075-0.10 or 0.020-0.125 mg kg(-1). Identification of analytes was based on retention times and MRM ratios. Recoveries were assessed at four different levels for each analyte and were between 73 and 106%, with relative standard deviations under reproducibility conditions of <20%. The measurement uncertainties of the method for each pesticide analysed were below 50%. Previous validation of the same method, applied to papaya samples and satisfactory results obtained in various proficiency tests with different high water content matrices, demonstrated the applicability of the method to these classes of commodities, without clean-up. The validated method will be applied routinely in the pesticide residues monitoring programme that constitutes the National Residue and Contaminant Control Plan of Brazil.