Modified QuEChERS Extraction Research Articles

Development of a method for the simultaneous determination of multi-class pesticides in earthworms by liquid chromatography coupled to tandem electrospray mass spectrometry.

Agricultural intensification, and in particular the use of pesticides, leads over the years to a loss of biodiversity and a decline of ecosystem services in cultivated zones and agricultural landscapes. Among the animal communities involved in the functioning of agro-ecosystems, earthworms are ubiquitous and recognized as indicators of land uses and cultural practices. However, little data is available on the levels of pesticides in such organisms in natura, which would allow estimating their actual exposure and the potentially resulting impacts. Thus, the objective of this study was to develop a sensitive analytical methodology to detect and quantify 27 currently used pesticides in earthworms (Allolobophora chlorotica). A modified QuEChERS extraction was implemented on individual earthworms. This step was followed by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). The whole analytical method was validated on spiked earthworm blank samples, with regard to linearity (from 1 to 100 method limit of quantification, r2 > 0.95), intra-day precision (relative standard deviation (RSD) < 15%), inter-day precision (RSD < 20%), recoveries (mainly in the range 70-110%), and limits of detection and of quantification (inferior to 5ng/g for most of the pesticides). The developed method was successfully applied to determine the concentrations of pesticides in nine individuals collected in natura. Up to five of the selected pesticides have been detected in one individual. Graphical abstract.

Food safety traits of mussels and clams: distribution of PCBs, PBDEs, OCPs, PAHs and PFASs in sample from different areas using HRMS-Orbitrap® and modified QuEChERS extraction followed by GC-MS/MS

ABSTRACTReviewing the presence of contaminant residues is important both for food safety and for monitoring of environmental pollution. Here, the occurrence of 6 polychlorinated biphenyls (PCBs), 15 organochlorine pesticides (OCPs), 7 polybrominated diphenyl ethers (PBDEs), 4 polycyclic aromatic hydrocarbons (PAHs) and 17 perfluoroalkyl substances (PFASs) was evaluated in mussels and clams. A liquid chromatography-high resolution mass spectrometry (HPLC-HRMS) and an innovative QuEChERS extraction followed by gas chromatography-tandem mass spectrometry (GC-MS/MS) methods were developed, validated and applied. We demonstrate good linearity, repeatability and accuracy of these methods, confirming that they are suitable for the analyses of mollusc samples. The prevalence of PCBs, OCPs and PAHs was higher in mussels than in clams. For PFASs, contamination was higher in clams than in mussels. The samples were all compliant with the regulations, and, for the compounds without legislative limits, a risk assessment confirmed that the values were lower than the tolerable intakes.

High-throughput determination of valproate in human samples by modified QuEChERS extraction and GC-MS/MS

A new high-throughput method was developed for analysis of valproate in human plasma samples by QuEChERS extraction and gas chromatography-tandem mass spectrometry (GC-MS/MS). Plasma samples (0.2 ml) spiked with valproate and secobarbital-d5 (internal standard) were diluted with 1.3 ml of distilled water. Acetonitrile (1 ml) was added followed by 0.4 g MgSO4 and 0.1 g NaOAC. After a centrifugation step (2000 g for 10 min), 1 ml of the supernatant was transferred to a dispersive-solid phase extraction (dSPE) tube containing 150 mg MgSO4 and 50 mg C18. This mixture was vortexed and centrifuged at 3000 g for 5 min, and then the upper layer was evaporated to dryness under a stream of nitrogen. The residue was dissolved in 40 μl ethyl acetate, and a 1-μl aliquot was injected into the GC-MS/MS. The GC separation of the compounds was achieved on a fused-silica capillary column Rxi-5Sil MS (30 m × 0.25 mm i.d.; 0.25-µm film thickness) and detected by MS/MS operating in electron ionization ion source mode. The regression equations showed excellent linearity (r > 0.9997) from 50 to 5000 ng/ml for plasma, with limit of detection of 10 ng/ml. The extraction efficiency of valproate for plasma ranged between 71.2%-103.5%. The coefficient of variation was <18.5%. The method was successfully applied to actual analyses of an autopsy case. This method can be useful for simple and reliable measurements of valproate in clinical and toxicological analyses; it can be integrated in screening and simultaneous determination methods for multiple drugs and poisons in the further studies.

Rapid multiresidue determination of pesticides in livestock muscle and liver tissue via modified QuEChERS sample preparation and LC-MS/MS

ABSTRACTMany multiresidue methods for the determination of pesticides in vegetables and fruits have been reported to date. However, few such methods have been employed to investigate pesticide residues in animal tissue. In this study, an LC-MS/MS multiresidue method coupled with modified QuEChERS extraction was developed and validated for the investigation of eight pesticide residues: prallethrin (PR), resmethrin (RMT), imidacloprid (IMC), diflubenzuron (DFB), cyromazine (CYR), etofenprox (EFP), dinotefuran (DNT) and phthalthrin (PTLT). This method involves initial extraction in a water/acetone system, the addition of salts and a subsequent extraction/partitioning step and, finally, a clean-up step utilising dispersive solid-phase extraction (SPE). The mean recoveries of seven of the pesticides (the exception being CYR) ranged between 74.7% and 113.5%, and the CVs of the livestock tissue – bovine, swine, and chicken muscle and liver tissue spiked at 10 ng g–1 (50 ng g–1 for RMT and DNT) and 100 ng g–1 – were < 13.8%. The recoveries of CYR in all muscle and liver spiked samples ranged from 56.9% to 78.3%, while those of RMT in swine liver were > 120%. Therefore, this method was considered as being unsuitable for the investigation of these samples. The limits of quantitation (LOQs) of seven of the investigated pesticides (the exception being swine liver) in the tissue samples ranged from 0.9 to 15.2 ng g–1. We therefore concluded that this LC-MS/MS multiresidue method is a valid and suitable for the investigation of seven pesticides in animal tissue, but it is unsuitable for the analysis of CYR in all animal tissues and RMT in swine liver tissue.

GC-MS Method for the Analysis of Thirteen Opioids, Cocaine and Cocaethylene in Whole Blood Based on a Modified Quechers Extraction

GC-MS Method for the Analysis of Thirteen Opioids, Cocaine and Cocaethylene in Whole Blood Based on a Modified Quechers Extraction

Development of a multi-residue analysis of diclofenac and some transformation products in bivalves using QuEChERS extraction and liquid chromatography-tandem mass spectrometry. Application to samples from mesocosm studies

Pharmaceuticals are ubiquitously present in the aquatic environment, mainly due to insufficient removal in wastewater treatment plants. Although these compounds are often found at trace levels in waters, long-term exposure can have negative impacts on biotic communities due to their inherent biological activity. The non-steroidal anti-inflammatory drug diclofenac (DCF) is one of the most frequently detected human pharmaceuticals in water and has recently been included in the “watch” list of the European Union. However little data are available on the detection of this substance and its transformation products in aquatic organisms. In this context, an analytical methodology has been developed to quantify traces of DCF along with its biotic and abiotic transformation products in a wild species of bivalve, the zebra mussel Dreissena polymorpha. A modified QuEChERS extraction was implemented on a small quantity of soft bivalve tissue (100mg). This was followed by liquid chromatography coupled to tandem-mass spectrometry (LC-MS/MS) with electrospray ionization in positive mode (ESI+). Whole analytical method was validated on spiked real samples, with regard to linearity (from 1 to 50 or 100ng/g depending on the target compounds, R2>0.99), intra-day precision (relative standard deviation (RSD)<18%), inter-day precision (RSD <25%), (recoveries 78–117%), and limits of detection and of quantification (both inferior or equal to 1ng/g). The optimized method was successfully applied to organisms collected from mesocosm experiments. Bioconcentration factors comprised between 4 and 13 were observed for DCF in the zebra mussels. To the best of our knowledge, the product 2-indolone was for the first time detected in bivalves, with levels up to 6ng/g.

Postmortem redistribution of methamphetamine and amphetamine in blood specimens from various blood vessels and in the specimens from pericardial fluid, bile, stomach contents and various solid tissues collected from a human cadaver

We recently encountered an autopsy case in which methamphetamine (MA) was involved. The postmortem interval was estimated to be as long as 6–7 days. We collected the blood specimens from 9 locations of the heart and blood vessels, and specimens from pericardial fluid, bile, stomach contents and 9 solid tissues (in total 21 specimens), which were subjected to analysis of MA and the metabolite amphetamine by liquid chromatography–tandem mass spectrometry after a modified QuEChERS extraction. The highest concentration of MA was found for the stomach contents, suggesting the oral ingestion of MA. Among the blood specimens, their MA concentrations varied from 268 to 911 ng/mL. The concentration of MA in the left heart blood was higher than that in the right heart blood. In spite of this, the MA concentration in the pulmonary vein was much lower than that in the left heart blood. The comparison of MA concentrations in venous blood vessels showed that MA concentration was highest in the vena cava, followed by the iliac vein, and was lowest in the femoral vein, suggesting that MA concentration is decreased by diffusion across the thin walls of venous blood vessels during the postmortem interval. The partial loss of a xenobiotic by diffusion via the thin wall of the femoral vein should be taken into consideration especially when the postmortem interval is relatively long.

Development and validation of an UHPLC-MS/MS method for the determination of mycotoxins in grass silages

An ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) multi-mycotoxin analytical method was developed to simultaneously identify and quantify 20 mycotoxins in grass silages, inclusive of mycotoxins that are currently regulated in European Union feeds. Extraction of mycotoxins from dried grass silages was performed using of a modified QuEChERS extraction employing an acidified aqueous extraction (0.1 N HCl) with no further clean-up. Following chromatographic separation, analytes were detected using a fast polarity-switching MS/MS method that allowed both positive and negative ions to be analysed from a single injection, thus the reducing time and cost of analysis. The limits of detection and quantification ranged between 3 µg kg–1 DM (aflatoxin B1, beauvericin and enniatin A and A1) and 200 µg kg–1 DM (deoxynivalenol), and between 10 µg kg–1 DM (aflatoxin B1, beauvericin and enniatin A1) and 500 µg kg–1 DM (deoxynivalenol), respectively. Inter-assay accuracy and precision ranged between 90% and 107% and between 3.9% and 15.0% CV, respectively. The accuracy of the method was assessed through the application to a range of incurred samples in an inter-laboratory study.

Determination of pesticide multi-residues in green tea using a modified QuEChERS extraction and liquid chromatography tandem mass spectrometry technique

A modified QuEChERS method was developed and validated for determination of pesticide multi-residues in green tea by liquid chromatography tandem mass spectrometry. Lead acetate was first time used together with primary secondary amine and graphite carbon black to eliminate tannin, caffeine, and other pigments in tea and thus reduced the matrix effects. The method was compared to the original QuEChERS method as well as A.O.A.C. QuEChERS method. For accurate quantification, the matrix matched calibration technique was used. The method showed good performance in the concentration range from 0.01 to 1 mg kg–1. All pesticides could be quantified at and lower than 0.01 mg kg–1. Recoveries were from 70 to 120% and repeatabilities were &lt;15% RSD depending on the compounds.

Occurrence of pesticide residues and transformation products in different types of dietary supplements

The purpose of this study was to evaluate the presence of pesticide residues and transformation products in dietary supplement products. Thirty-two samples were analysed to determine 177 pesticides by gas chromatography–tandem mass spectrometry (GC-MS/MS) and 333 pesticides by liquid chromatography–high-resolution mass spectrometry (LC-HRMS). Pesticides were extracted from different kinds of dietary supplements by the use of a modified QuEChERS extraction method. Six samples contained pesticide residues at concentration up to 92.7 µg kg−1, but only butralin exceeded the maximum residue limits set for raw material. In addition to target compounds, LC-HRMS enables the simultaneous detection of non-target pesticides. In this case, transformation products of pesticides were detected in the analysed samples using HRMS analyser (Exactive-Orbitrap). These compounds were not included in the original method, and they were monitored as post-target compounds, knowing their molecular formula and exact mass. Mass accuracy was always < 2 ppm, corresponding to a maximum mass error. The positive findings endorse the idea that a deeper and continuous investigation of pesticide residues and transformation products in dietary supplement products is necessary in order to guaranty consumer’s safety.

Development of LC-MS/MS methodology for the detection/determination and confirmation of chloramphenicol, chloramphenicol 3-O-β-d-glucuronide, florfenicol, florfenicol amine and thiamphenicol residues in bovine, equine and porcine liver.

A method for the detection and confirmation of organic solvent extractable residues of the neutral, acidic, and basic analytes of the amphenicol class veterinary drugs and selected metabolites was developed and validated. Using a modified QuEChERS extraction with SPE cleanup and LC-MS/MS analysis, limits of detection and confirmation for the different analytes in bovine, equine, and porcine liver ranged from 0.1ng/g for chloramphenicol to 1ng/g for florfenicol amine. Tissue homogenization with an ammonium formate/EDTA solution and subsequent analyte partitioning against 7:3 acetonitrile:isopropanol solution and mixed-mode strong-cation exchange solid-phase extraction cartridge cleanup allowed for the extraction of all compounds from tissues with mean recoveries ranging from 50% (chloramphenicol 3-O-β-d-glucuronide) to 90% (thiamphenicol). Matrix effects ranged from greater than 85% suppression for florfenicol amine to 70% matrix enhancement for chloramphenicol 3-O-β-d-glucuronide. Quantitation and confirmation were accomplished using commercially available penta-deuterated chloramphenicol as internal standard and multiple reaction monitoring (MRM) of two or three transitions per target analyte. Method accuracy was greater than 15% for all compounds except the glucuronide metabolite. Intra-lab method repeatability estimates ranged from 73% RSD for chloramphenicol 3-O-β-d-glucuronide to 14% RSD for chloramphenicol. Only chloramphenicol 3-O-β-d-glucuronide and florfenicol amine at the low end of their calibration ranges (0.25 and 1ng/g, respectively) did not meet AOAC recommended HorRatr guidelines for intra-lab repeatabilities. Preliminary tests show that the method's extraction protocol can be used to recover analytes of the β-agonists, corticosteroids, fluoroquinolones, sulfonamides, and tetracycline drug classes from the same matrices. Requirements for use in national chemical monitoring programs as a detection/confirmatory (florfenicol amine and chloramphenicol 3-O-β-d-glucuronide) and determinative/confirmatory (chloramphenicol, florfenicol, thiamphenicol) analytical methodology are met.

High-Throughput Analytical Strategy Based on Modified QuEChERS Extraction and Dispersive Solid-Phase Extraction Clean-up Followed by Liquid Chromatography-Triple-Quadrupole Tandem Mass Spectrometry for Quantification of Multiclass Mycotoxins in Cereals

A simple, reliable, efficient, selective and sensitive QuEChERS-based (quick, easy, cheap, effective, rugged and safe) sample preparation strategy, involving an initial partitioning step using acidified acetonitrile (ACN), MgSO4, NaCl and citrate buffer salts, combined with dispersive solid-phase extraction (d-SPE) clean-up, is proposed for the simultaneous multiclass mycotoxins quantification, including aflatoxins, ochratoxins, fumonisins, trichothecenes and zearalenone, in cereals. The final clear extracts were concentrated under vacuum to near dryness and taken-up with the initial mobile phase (MeOH:H2O;70:30, v/v) previous to reversed-phase liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) analysis. Careful optimization of the LC-ESI-MS/MS parameters was achieved in order to attain a fast separation and increased sensitivity. The detection was carried out on a triple-quadrupole tandem mass spectrometry (MS/MS) by electrospray ionization in positive ion mode (ESI+) with multiple reaction monitoring (MRM). Tandem MS conditions were optimised in order to increase selectivity, selecting the best transitions (parent ion to quantifier and qualifier ions) for quantification and identification. The performance of the method was assessed and compared to European Commission (EC) Regulations, by studying the selectivity, specificity, limits of detection (LOD) and quantification (LOQ), linear dynamic range (LDR), matrix effect, accuracy, precision, and uncertainty. Good linearity (r 2 > 0.9713) was achieved for all mycotoxins investigated, and LODs (S/N = 3) and LOQs (S/N = 10) were below the tolerance levels of mycotoxins set by EC. Recoveries of the extraction process, obtained with different spiked concentrations, ranged from 72.9 to 120.6 %, with relative standard deviations (RSD) lower than 23.0 %. Only in 6 % of all combinations did the RSD values exceed 15 %. Matrix effects were observed by comparing the slope of matrix-matched standard calibration with that of the solvent. The developed method was applied to evaluate the co-occurrence of multiclass mycotoxins in cereals collected at the importation points and consumer habitations at Madeira Island. Samples collected at importation points (15 wheat samples, 4 maize samples and 2 rice samples) showed the presence of DON in three wheat samples, and FB1 and HT-2 in one wheat sample. Three maize samples were detected with FB1 (two samples) and AFG2 (one sample) whereas one rice sample was detected with ZEN. The results revealed the absence of target mycotoxins on the rice samples collected at consumer habitations. None of the studied cereal samples exceeded the maximum permissible limits or indicative levels set by the EC which means that the particular Madeira Island subtropical climate conditions do not represent a major risk for cereal contamination, taking into account the investigated mycotoxins.

Determination of Chlorinated Phenoxy Acid Herbicides in Tobacco by Modified QuEChERS Extraction and High-Performance Liquid Chromatography/Tandem Mass Spectrometry

A new method for determination of phenoxy acid herbicide residues in tobacco based on the use of liquid extraction/partition and dispersive SPE followed by HPLC/electrospray ionization-MS/MS is reported. Formic acid (2%, v/v) in acetonitrile as the extraction solvent and inclusion of citrate buffer helped partitioning of all analytes into the acetonitrile phase. Quantitative analysis was done in the multiple-reaction monitoring mode using two combinations of selected precursor ion and product ion transition for each compound. The recoveries obtained for each pesticide ranged between 85 and 110% at two spike concentration levels. Good linear relationships were observed, with the correlation coefficient (r2) >0.998 for all analytes. The method is simple, efficient, and sensitive, and each of its performance characteristics meets the requirements for determination of phenoxy acid herbicide residues in tobacco.

A multi-residue method for the determination of 124 pesticides in rice by modified QuEChERS extraction and gas chromatography–tandem mass spectrometry

A modified QuEChERS method for simultaneous determination of 124 pesticide residues in rice was established and validated. The rice samples were initially extracted with acetonitrile (MeCN), and the targeted pesticides were purified following the dispersive solid phase extraction (d-SPE) cleanup method and detected by gas chromatography–tandem mass spectrometry (GC–MS/MS). The efficiency of citrate-buffered and unbuffered method in liquid extraction procedure was compared; the amount of primary secondary amine (PSA) was optimised. In the method validation, correlation coefficients (r2) were higher than 0.990 with the linear ranging from 10 to 200μgkg−1. At the fortification levels of 20–200μgkg−1, average recoveries ranged from 70% to 122.7% with the RSD <20%.

Addition to Determination of Parent and Substituted Polcyclic Aromatic Hydrocarbons in High-Fat Salmon Using a Modified QuEChERs Extraction, Dispersive SPE and GC–MS

Addition to Determination of Parent and Substituted Polcyclic Aromatic Hydrocarbons in High-Fat Salmon Using a Modified QuEChERs Extraction, Dispersive SPE and GC–MS

Residues of pirimiphos-methyl in cereals and processed fractions following post harvest spray application

The aim of this work was to comparatively assess the persistence of pirimiphos methyl residues in cereals and in their milling fractions after spray application in post harvest. An analytical method, based on a slightly modified QuEChERS extraction followed by liquid chromatography tandem mass spectrometry (LC-MS/MS) determination was validated: mean recovery was in the range 73 % to 92 % depending on the spiking level, and precision as RSD ranged from 11 % to 16 %. The analysis of treated samples revealed that pirimiphos-methyl residues were highly persistent and that no differences could be observed between wheat, durum wheat and oat. As far as the impact of the milling process on residues is concerned, pirimiphos methyl contamination was significantly reduced during both cleaning and processing, and most of the contamination was related to outer kernel fractions.