Alternative calibration techniques for counteracting the matrix effects in GC-MS-SPE pesticide residue analysis - a statistical approach

Simultaneous determination of sixteen phthalic acid esters (PAEs) in soil and evaluation of matrix effect using a QuEChERS/GC/MS-internal standard method

Phthalic acid esters (PAEs) are emerging pollutants that need to be analyzed precisely. Chromatography-based determination of PAE content in soils are frequently affected by matrix effect, which may limit the quantification of different kinds of PAEs from different types of soil. Here we optimized a QuEChERS protocol combined with gas chromatography-mass spectrometry (GC-MS) for simultaneous determination of 16 PAEs in different soils. PAEs in different type of soils (fluvo-aquic soil, red soil, and black soil) were extracted with acetonitrile followed by GC-MS detection based on quantitative ion internal standard method. All 16 PAEs showed excellent linear relationships with mass peak areas (R2 > 0.99). The limits of detection (LOD) and limits of quantitation (LOQ) of all the samples were in the range of 0.91-66.97 µg/kg and 2.7-200.9 µg/kg, respectively. The accurate test at 0.5, 0.1, and 1.0 mg/kg spiking level recorded recovery rate between 80.11% and 100.99% with relative standard deviations (RSDs) ranging from 0.37 to 8.50% in tested matrices. No significant matrix effect was observed for most tested PAEs. This is a simple method with high sensitivity and strong stability, which is suitable and reproducible for quantifying large number of PAEs in different types of soil.

Determination of remdesivir in human plasma using (deep eutectic solvent-ionic liquid) ferrofluid microextraction combined with liquid chromatography

A microextraction technique based on ferrofluids was developed for the preconcentration and quantification of Remdesivir in human plasma samples. This method utilized a new type of magnetic colloids created by combining silica-coated magnetic particles with modified ionic liquid and natural hydrophobic deep eutectic solvent as the carrier liquid. The efficiency of the sorption and desorption steps was optimized using a chemometrics approach. Under the optimized conditions, the calibration curve exhibited linearity in the concentration range of 0.5 to 500.0 μg L-1, with a limit of detection and quantification of 0.2 and 0.5 μg L-1, respectively. The method precision was evaluated by assessing intra- and interday precision at three different analyte concentrations, yielding values of 8.9% and 16.8%, respectively. Moreover, the method accuracy fell within the range of 90.9% to 107.5%. This proposed method offers a green and environmentally friendly sample preparation technique for conducting pharmacodynamic, pharmacokinetic, and therapeutic drug monitoring studies of Remdesivir in biological fluids. Importantly, this technique eliminates the need for external energy sources or the use of dispersive solvents, providing a more efficient and sustainable approach.

A green method for the determination of illicit drugs in wastewater and surface waters-based on a semi-automated liquid-liquid microextraction device

Liquid-phase microextraction (LPME) is a simple, low-cost, and eco-friendly technique that enables the detection of trace concentrations of organic contaminants in water samples. In this work, a novel customized microextraction device was developed for the LPME extraction and preconcentration of nine illicit drugs in surface water and influent and effluent wastewater samples, followed by analysis by GC-MS without derivatization. The customized device was semi-automated by coupling it with a peristaltic pump to perform the collection of the upper layer of the organic phase. The extraction parameters affecting the LPME efficiency were optimized. The optimized conditions were: 100 µL of a toluene/DCM/EtAc mixture as extractor solvent; 30min of extraction time under vortex agitation (500rpm) and a solution pH of 11.6. The limits of detection and quantification ranged from 10.5ng L-1 (ethylone) to 22.0ng L-1 (methylone), and from 34.9ng L-1 to 73.3ng L-1 for these same compounds, respectively. The enrichment factors ranged from 39.7 (MDMA) to 117 (cocaethylene) and the relative recoveries ranged from 80.4% (N-ethylpentylone) to 120% (cocaine and cocaine-d3). The method was applied to real surface water, effluent, and influent wastewater samples collected in Salvador City, Bahia, Brazil. Cocaine was the main drug detected and quantified in wastewater samples, and its concentration ranged from 312ng L-1 to 1,847ng L-1. Finally, the AGREE metrics were applied to verify the greenness of the proposed method, and an overall score of 0.56 was achieved, which was considered environmentally friendly.

Essential oil in Phlomis tuberosa

Phlomis tuberosa L. (Lamiaceae) is a flowering perennial plant, native to Eurasia, and sparsely distributed in Bulgaria. The species has been proved to accumulate flavonoids, iridoids, phenolic glycosides, as well as essential oil. To now, there is no information on the chemical content of Bulgarian essential oil from the plant. The aim was to study the chemical composition of essential oils, obtained from the species. Four different samples were studied – essential oils produced from leaves and herbs, collected in the fields, and from leaves and flowering parts, harvested from the mountainous location. It was found that β-copaene was the major in the essential oil from both the leaves and of the flowering parts collected from Popitza. In addition, the other major constituent in leaf essential oil from Kladnitza was tau-muurolol. The essential oil, produced from the species, harvested from the higher altitude had phytol as the main component. The sesquiterpenoid content in leaf essential oil suggests that this plant substance is appropriate for medicinal use, due to the pharmacological properties of these compounds.

Adjustment of Matrix Effects in Analysis of 36 Secondary Metabolites of Microbial and Plant Origin in Indoor Floor Dust Using Liquid Chromatography-Tandem Mass Spectrometry

Exposure to microbial agents in water-damaged buildings is a major public health concern. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) has become a primary tool for testing environmental samples for microbial secondary metabolites (SMs); however, matrix effects can lead to inaccurate results in exposure assessment. Applying a universal internal standard (ISTD) and a matrix-matched calibration can adjust for matrix effects, as shown by our previous study. However, there are only few isotope-labeled internal standards for SMs available on the market. In this study, we determined the best-performing ISTDs among ten candidates (nine 13C-labeled isotopes and one unlabeled analogue) for each of 36 SMs. We analyzed school floor dust spiked with the 36 SMs to identify the best-performing ISTDs (initial experiment) and examined reproducibility with the selected ISTDs and the same spiked dust (validation 1). We also tested applicability for the selected ISTDs using spiked dust collected from different schools (validation 2). The three experiments showed that 26, 17, and 19 SMs had recoveries within the range 100 ± 40%. 13C-ochratoxin A and 13C-citrinin were most frequently selected as the best ISTDs for the 36 SMs, followed by deepoxy-deoxynivalenol, 13C-sterigmatocystin, and 13C-deoxynivalenol. Our study shows that using the identified, best-performing analogous ISTDs for those metabolites may improve testing accuracy for indoor dust and help better estimate exposure effects on potential health.

The role of effect-based methods to address water quality monitoring in South Africa: a developing country's struggle

Water is an important resource, and it is a worldwide struggle to provide water of good quality to the whole population. Despite good governing laws and guidelines set in place to help protect the water resources and ensure it is of good quality for various consumers, the water quality in South Africa is worsening due to lack of management. The deteriorating infrastructure is becoming progressively worse, due to corruption and insufficient funds. The ever-increasing number of toxicants, as well as the identification of emerging chemicals of concern, are also challenges South Africa is facing. Chemical analysis cannot determine the total biological effect of a mixture of chemical compounds, but this shortcoming can be addressed by adding effect-based methods (EBMs) to water quality monitoring programmes. In this paper, the current status of water quality monitoring in South Africa is discussed, as well as the capacity of the country to add EBMs to its water quality monitoring programmes to protect and improve human and animal life. Created in Biorender.com.

Pesticide residues in fruits and vegetables in Indonesia: findings of five-year proficiency testing

The first proficiency testing of pesticides in fruits and vegetables in Indonesia is reported. This report covers the findings of five-year proficiency testings. Every year, from 2016 to 2020, 18-25 laboratories join the proficiency testings and analyze 5-11 pesticides in tomato, orange, lettuce, brown rice, strawberry respectively. The number of laboratories participating in the proficiency testings tends to increase, although only 38 % of the laboratories are able to report all pesticides. More than 72 % of participants use QuEChERS or its modifications for sample preparation, all participants use gas chromatography or liquid chromatography for separation, at least 20 % of participants still rely on detectors other than mass spectrophotometer for detection, and 20 %-60 % of participants use matrix-matched calibration for quantification. The performance of laboratories is evaluated as z-score with an average of 90.8 % achieves satisfactory results while 3.3 % and 5.9 % achieve questionable and unsatisfactory results correspondingly. Overall, the performance of laboratory participants during proficiency testings is good. However, improvement is still needed, especially for the number of target pesticides for multi-residue pesticide analysis. Moreover, unsatisfactory z-scores are likely to be resulted from laboratories which use conventional solvent extraction, use detectors other than mass spectrometers, and are not accredited.

Fabrication of Nano/Micro-Structured Electrospun Detection Card for the Detection of Pesticide Residues

A novel nano/micro-structured pesticide detection card was developed by combining electrospinning and hydrophilic modification, and its feasibility for detecting different pesticides was investigated. Here, the plain and hydrophilic-modified poly(ε-caprolactone) (PCL) fiber mats were used for the absorption of indolyl acetate and acetylcholinesterase (AChE), respectively. By pre-treating the fiber mat with ethanol, its surface wettability was improved, thus, promoting the hydrolysis of the PCL fiber mat. Furthermore, the absorption efficiency of AChE was improved by almost two times due to the increased hydrophilicity of the modified fiber mat. Noteworthily, this self-made detection card showed a 5-fold, 2-fold, and 1.5-fold reduction of the minimum detectable concentration for carbofuran, malathion, and trichlorfon, respectively, compared to the national standard values. Additionally, it also exhibited good stability when stored at 4 °C and room temperature. The food detection test showed that this nano/micro-based detection card had better detectability than the commercial detection card. Therefore, this study offers new insights into the design of pesticide detection cards, which also broadens the application of electrospinning technique.

Sandwich injection and analyte protectants as a way to decrease the drift due to matrix effect between bracketing calibration in GC-MS/MS: A case study

In pesticide residues analysis, the drift is the difference between the concentration of two bracketing calibrations in the same batch. According to the SANTE/12682/2019 guideline a criterion of ±30% must be met or positive samples should be reanalyzed. This study aimed to investigate, for the first time, the efficiency of using analyte protectants (Aps) and the sandwich injection approach (SIA) to eliminate the drift between bracketing matrix matched-calibrations taking strawberry as an example. The strawberry samples were prepared according to the citrate-buffered QuEChERS (quick, easy, cheap, effective, rugged, and safe) procedure, followed by solvent exchange from acetonitrile to n-hexane:actone (9:1). Two batches were injected with the same sequence on GC-MS/MS, the only difference was that the first batch was without Aps and the second was with Aps. The sequence of the batch was as follows: blank solvent injection, 5 strawberry matched-calibrations at 0.05 μg/ml, separated by 20 blank strawberry injections after each strawberry matched-calibration injection. The drift was measured by considering the results of the first calibration as 100% and comparing the rest 4 injections with it. After 20 injections, out of the studied 219 pesticides, more than half of the pesticides fell out of criteria when analyte protectants were not used, and by the end of the samples batch 95% of the analytes were out of criteria. Only 8% of the studied analytes were out of criteria for the Aps batch after 20 injections. In the end of the 80 samples batch, 17% were out of criteria. Furthermore, at the end of the protected matrix-matched calibration batch, 90% of the pesticides had an RSD less than 15% in comparison with only 5% of the analytes for the non-protected batch. Moreover, the non-protected batch had an obvious negative drift in comparison with the protected batch. For example, the number of pesticides that had a lower result in the second matrix matched-calibration for the non-protected batch was more than twice the number in the protected batch (194 compared to 91 out of 219 pesticides for both experiments).

Simultaneous determination, dissipation and decontamination of fungicides applied on cabbage using LC-MS/MS

A method for simultaneous determination of carbendazim and tebuconazole residues in cabbage was developed and validated in LC-MS/MS. Samples were extracted and purified following the modified QuEChERS procedure, which enabled the elution of carbendazim and tebuconazole at 0.96 and 5.31 min, respectively. LOD and LOQ were 0.0005 and 0.0015 mg kg^-1, respectively. Mean recovery was in the range of 78.94 to 104.89% for carbendazim and 76.07 to 98.62% for tebuconazole. The field samples recorded residues of 0.274 and 0.481 mg kg^-1; and 0.194 and 0.392 mg kg^-1 at single and double dose for carbendazim and tebuconazole, respectively. Half-life values were 2.17 and 2.99 for carbendazim and 2.74 and 2.81 for tebuconazole at single and double dose, respectively. Decontamination with saltwater wash followed by cooking and lemon water wash found superior in the removal of residues more than 90%.

Development of a sensitive and stable GC-MS/MS method for simultaneous determination of four N-nitrosamine genotoxic impurities in sartan substances

Recently, N-nitrosamines have been unexpectedly found in generic sartan products. Herein, we developed a sensitive and stable GC-MS/MS method with multiple reactions monitoring mode for the simultaneous determination of four N-nitrosamines in sartan substances, namely, N-nitrosodimethylamine, N-nitrosodiethylamine, N-nitrosodibutylamine, and N-nitrosodiisopropylamine. The conditions of gas chromatography and mass spectrometry were optimized. The method was validated according to the International Council for Harmonization guidelines in terms of sensitivity, linearity, accuracy, precision, specificity, and stability. The limits of detection of N-nitrosamines in sartan substances ranged from 0.002 to 0.150 ppm, and the corresponding limits of quantification were in the range of 0.008-0.500 ppm, which met the sensitivity requirements for the limits set by the Food and Drug Administration of the United States. The internal standard curve of four N-nitrosamines showed good linearity of regression coefficients over 0.99. The recoveries of N-nitrosamines in selected sartan drugs ranged from 87.68 to 123.76%. The intraday and interday relative standard deviation values were less than 9.15%. Therefore, this proposed method exhibited good sensitivity and precision, high accuracy, and fast analysis speed, which provide a reliable method for quality control of N-nitrosamines in sartan products.

Polychlorinated Biphenyl Profile in Polyhydroxy-alkanoates Synthetized from Urban Organic Wastes

The microbial synthesis of polyhydroxyalkanoates (PHA) from organic wastes is a valuable process to valorize available renewable resources, such as food wastes and biological sludge. Bioplastics find many applications in various sectors, from medical field to food industry. However, persistent organic pollutants could be transferred from wastes to the final product. The present paper demonstrates that the use of municipal wastes in PHA production is safe for the environment and human health and provides a polychlorinated biphenyl (PCB) profile in both commercial and waste-based PHA samples. PCB analysis in several PHA samples showed very low concentrations of the target analytes. Commercial PHA samples showed a similar PCB level with respect to PHA samples from municipal waste/sludge and higher than PHA samples from fruit waste. For all analyzed PCBs, detected concentrations were consistently lower than the ones reported in regulatory framework or guidelines.

Dissipation behavior and dietary risk assessment of lambda-cyhalothrin, thiamethoxam and its metabolite clothianidin in apple after open field application

The dissipation dynamics and residue amounts of lambda-cyhalothrin, thiamethoxam and clothianidin in apple were investigated by using rapid resolution liquid chromatography triple quadrupole mass spectrometer (RRLC-MS/MS) and gas chromatography mass spectrometry (GC-MS). The developed method performed satisfactory recoveries of 88%-105% and the limit of quantitation (LOQ) was 0.01 mg kg^-1. The suspension concentrate (SC) formulation of lambda-cyhalothrin and thiamethoxam was applied on apple field in accordance with good agricultural practice (GAP). The half-lives of two pesticides ranged from 7.01 d to 17.3 d and the terminal residues were <0.01-0.21 mg kg^-1. Based on the Chinese dietary pattern, the dietary risk of lambda-cyhalothrin and total thiamethoxam were predicted by comparing intake amounts with the toxicological data, namely acceptable daily intake (ADI) and acute reference dose (ARfD). The chronic and acute risk quotients were 0.1080-0.4463 and 0.0008-0.2005, respectively, which showed negligible risk for general consumers. The pre-harvest interval (PHI) of 21 d was suggested for the formulation in compliance with maximum residue limit (MRL) and dietary risk assessment, meanwhile, the MRL of 0.1 mg kg^-1 was recommended for thiamethoxam in apple. These results were vital for guiding reasonable usage of two insecticides and for approval of formulation use.

Use of an improved high-throughput absolute abundance quantification method to characterize soil bacterial community and dynamics

High-throughput sequencing has dramatically expanded our understanding of bacterial communities based on the information of the species types and their relative abundances. Recently, researchers have also become aware of a deficiency in not considering the absolute abundance in this technique. Combining two or more different methods has typically been used to achieve absolute quantification of microbial communities. However, making a combination of different methods not only is time-consuming but also involves potential uncertainty due to variations in the experimental conditions. To simplify the experimental procedure and improve the high-throughput absolute abundance quantification (HAAQ) of a soil bacterial community, we propose an HAAQ method that uses an internal standard strain (ISS) HAAQ-GFP to simultaneously obtain both the relative and absolute abundances in the soil bacterial community. The results showed that a soil bacterial community and its dynamics can be better characterized by the HAAQ method when the optimal concentrations of ISS HAAQ-GFP (10⁵ to 10⁷cellsg^-1) were used, and a 16S rRNA gene copy number adjustment was applied. Based on the HAAQ method, we first found that soil bacterial absolute abundances at the genus level fitted well to the partial log-normal distribution function, and most genera concentrations were in the range of 10^3.5 to 10^6.5cellsg^-1 in the test soils. Our case studies also indicated that more comprehensive descriptions of soil bacterial communities and their dynamics can be achieved by both the relative and absolute abundances than by the relative abundance alone. The improved HAAQ method can be potentially applied to other microbial ecological studies and to stimulating the development of quantitative bacterial ecology studies.

Compensation for matrix effects in GC analysis of pesticides by using cucumber extract

Matrix effects (MEs) can adversely affect quantification in pesticide residue analysis using GC. Analyte protectants (APs) can effectively interact with and mask active sites in the GC system, and are added individually or in combination to sample extracts and calibration solutions to minimize errors related to MEs. Unfortunately, APs cannot sufficiently compensate for MEs in all cases. Plant extracts, containing a broad range of natural compounds with AP properties, can also be used for this purpose. In this study, the applicability of cucumber extract as a natural AP mixture was investigated both alone and in combination with traditional APs. Extracts of two selected difficult matrices (onion and garlic) were prepared according to the citrate-buffered QuEChERS (quick, easy, cheap, effective, rugged, and safe) procedure. ME values of 40 representative GC-amenable pesticides were compared when calibrating against standards in pure solvent and in cucumber extract, with and without the addition of APs. Using a GC system with a contaminated inlet liner, the use of a cucumber-based calibration solution decreased MEs remarkably. The combination of APs with cucumber raw extract further decreased MEs, resulting in more than 85% of the tested pesticides showing ≤ 10% ME in onion and ≤ 20% ME in garlic. These results demonstrate that the preparation of calibration standards based on cucumber extracts (with or without the addition of APs) is a very useful and practical approach to compensate for MEs in pesticide residue analysis using QuEChERS and GC-MS/MS. The use of various internal standards is furthermore critically discussed.

Reduction of interferences in the analysis of Children's Dimetapp using ultraviolet spectroscopy data and target factor analysis

A calibration matrix has been developed and successfully applied to quantify actives in Children's Dimetapp®, a cough mixture whose active components suffer from heavy spectral interference. High-performance liquid chromatography/photodiode array instrument was used to identify the actives and any other UV-detectable excipients that might contribute to interferences. The instrument was also used to obtain reference data on the actives, instead of relying on the manufacturer's claims. Principal component analysis was used during the developmental stages of the calibration matrix to highlight any mismatch between the calibration and sample spectra, making certain that "apples" were not compared with "oranges". The prediction model was finally calculated using target factor analysis and partial least squares regression. In addition to the actives in Children's Dimetapp® (brompheniramine maleate, phenylephrine hydrogen chloride, and dextromethorphan hydrogen bromide), sodium benzoate was identified as the major and FD&C Blue #1, FD&C Red #40, and methyl anthranilate as minor spectral interferences. Model predictions were compared before and after the interferences were included into the calibration matrix. Before including interferences, the following results were obtained: brompheniramine maleate=481.3mgL^-1±134% RE; phenylephrine hydrogen chloride=1041mgL^-1±107% RE; dextromethorphan hydrogen bromide=1571mgL^-1±107% RE, where % RE=percent relative error based on the reference HPLC data. After including interferences, the results were as follows: brompheniramine maleate=196.3mgL^-1±4.4% RE; phenylephrine hydrogen chloride=501.3mgL^-1±0.10% RE; dextromethorphan hydrogen bromide=998.7mgL^-1±1.6% RE as detailed in Table 6.

Application of gas chromatography/tandem mass spectrometry to determine a wide range of petrogenic alkylated polycyclic aromatic hydrocarbons in biotic samples

RATIONALE

Due to the inherent toxicity of these compounds, analysis of petrogenic alkylated polycyclic aromatic hydrocarbons (PAHs) and heteroaromatic compounds in environmental samples is crucial. However, most existing methods are not sensitive enough when the analyte concentrations are low. Gas chromatography/tandem mass spectrometry (GC/MS/MS) is well suited to tackle this challenge, but methods are yet to be fully developed.

METHODS

A gas chromatograph coupled with a triple quadrupole mass spectrometer operated in multiple reaction monitoring (MRM) mode was applied for the analysis. MRM transitions and analytical conditions were optimized for the cluster analysis of 24 different compound classes of alkylated PAHs and heteroaromatics present in crude oils. Further, the method was verified and applied to analyze the body burden of these compounds in crude oil-exposed haddock eggs.

RESULTS

A comprehensive and sensitive method for the determination of C1-C4 alkylated naphthalenes, benzothiophenes, fluorenes, phenanthrenes, dibenzothiophenes, chrysenes, pyrenes and fluoranthenes was developed. The method showed good precision (RSD <15%), and the obtained concentrations were similar to those obtained by traditional GC/MS analysis.

CONCLUSIONS

We demonstrate the successful application of this method towards crude oil-exposed fish eggs, where we are able to precisely measure total PAH body burden below 0.5 μg/g. The demonstrated method facilitates further miniaturization in sample preparation. Copyright © 2016 John Wiley & Sons, Ltd.

Automated multi-plug filtration cleanup for liquid chromatographic-tandem mass spectrometric pesticide multi-residue analysis in representative crop commodities

An automated multi-plug filtration cleanup (m-PFC) method on modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) extracts was developed. The automatic device was aimed to reduce labor-consuming manual operation workload in the cleanup steps. It could control the volume and the speed of pulling and pushing cycles accurately. In this work, m-PFC was based on multi-walled carbon nanotubes (MWCNTs) mixed with other sorbents and anhydrous magnesium sulfate (MgSO4) in a packed tip for analysis of pesticide multi-residues in crop commodities followed by liquid chromatography with tandem mass spectrometric (LC-MS/MS) detection. It was validated by analyzing 25 pesticides in six representative matrices spiked at two concentration levels of 10 and 100μg/kg. Salts, sorbents, m-PFC procedure, automated pulling and pushing volume, automated pulling speed, and pushing speed for each matrix were optimized. After optimization, two general automated m-PFC methods were introduced to relatively simple (apple, citrus fruit, peanut) and relatively complex (spinach, leek, green tea) matrices. Spike recoveries were within 83 and 108% and 1-14% RSD for most analytes in the tested matrices. Matrix-matched calibrations were performed with the coefficients of determination >0.997 between concentration levels of 10 and 1000μg/kg. The developed method was successfully applied to the determination of pesticide residues in market samples.

Dilution standard addition calibration: A practical calibration strategy for multiresidue organic compounds determination

Among calibration approaches for organic compounds determination in complex matrices, external calibration, based in solutions of the analytes in solvent or in blank matrix extracts, is the most applied approach. Although matrix matched calibration (MMC) can compensates the matrix effects, it does not compensate low recovery results. In this way, standard addition (SA) and procedural standard calibration (PSC) are usual alternatives, despite they generate more sample and/or matrix blanks consumption need, extra sample preparations and higher time and costs. Thus, the goal of this work was to establish a fast and efficient calibration approach, the diluted standard addition calibration (DSAC), based on successive dilutions of a spiked blank sample. In order to evaluate the proposed approach, solvent calibration (SC), MMC, PSC and DSAC were applied to evaluate recovery results of grape blank samples spiked with 66 pesticides. Samples were extracted with the acetate QuEChERS method and the compounds determined by ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS). Results indicated that low recovery results for some pesticides were compensated by both PSC and DSAC approaches. Considering recoveries from 70 to 120% with RSD <20% as adequate, DSAC presented 83%, 98% and 100% of compounds meeting this criteria for the spiking levels 10, 50 and 100μgkg(-1), respectively. PSC presented same results (83%, 98% and 100%), better than those obtained by MMC (79%, 95% and 97%) and by SC (62%, 70% and 79%). The DSAC strategy showed to be suitable for calibration of multiresidue determination methods, producing adequate results in terms of trueness and is easier and faster to perform than other approaches.

Determination of Six Pyrazole Fungicides in Grape Wine by Solid-Phase Extraction and Gas Chromatography-Tandem Mass Spectrometry

A gas chromatography-tandem mass spectrometry (GC-MS/MS) method was developed for the first simultaneous identification and quantification of six pyrazole fungicides (furametpyr, rabenzazole, fluxapyroxad, penflufen, bixafen, and isopyrazam) in grape wine samples. The grape wine samples were first diluted with water, then purified by solid-phase extraction, and finally examined by GC-MS/MS in multiple reaction monitoring (MRM) mode. Matrix-matched calibration curves were used to correct the matrix effects. The limits of quantification (LOQs), calculated as 10 times the standard deviation, were 0.2-0.8 μg kg(-1) for the six pyrazole fungicides. The average recoveries were in the range of 74.3-94.5%, with relative standard deviations (RSDs) below 5.8%, measured at three concentration levels. The proposed method is suitable for the simultaneous determination of six pyrazole fungicides in grape wine samples.

Determination of benzoylurea insecticides in environmental water and honey samples using ionic-liquid-mingled air-assisted liquid–liquid microextraction based on solidification of floating organic droplets

This method combined the advantages of air-assisted liquid–liquid microextraction and solidified floating organic droplet microextraction with a mixture extractant.