Matrix Enhancement Effects Research Articles

Development and validation of LC-MS/MS method for trace analysis of acrylamide, acrylic acid and N, N-methylene bis acrylamide in sandy loam soil

Acrylamide and N, N-methylene bis acrylamide are most commonly used monomer and crosslinker compounds employed in synthesis of super absorbent hydrogels. When applied as soil conditioners, there are apprehensions that these hydrogels degrade over time and thus may release the toxic monomers in the soil. A method was thus developed using Liquid Chromatography tandem mass spectrometry (LC-MS/MS) for the trace level quantification of acrylamide (AD), acrylic acid (AA) and N,N-methylene-bis-acrylamide (MBA) in sandy loam soil amended by two test hydrogels the Pusa Hydrogel and SPG 1118 hydrogel prepared using AD and MBA. The MRM (multiple reaction monitoring) transitions were optimized for both the compounds. Soil samples were extracted using dispersive solid-phase extraction (dSPE) with a modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) technique, employing acetonitrile. All analytes were quantified at trace levels within a five-minute run using UHPLC equipped with a C-18 column.Single laboratory validation of the developed method in soil matrix was conducted based on specificity, linearity, sensitivity, accuracy, precision, matrix effect and measurement of uncertainty. LC-MS/MS exhibited a linear response in the concentration range of 0.001 to 1 µg mL−1, with correlation coefficient >+0.99. Acceptable recovery (within 70–120 %) with repeatability (%RSD ≤20 %) was obtained at 0.01 to 1 µg g–1 fortification levels. LOQ (Limit of quantification) of the method for AD, AA and MBA in soil matrix were 0.05, 1 and 0.01 µg g–1, respectively. Both intra-laboratory repeatability and intermediate precision at LOQ suggested well acceptable precise (HorRat≈ 0.3) method for quantification. Matrix enhancement effect was observed in the order: AA>AD>MBA. The Expanded Uncertainty (EU) in soil matrix at LOQ was 21.64 %, 28 % and 19 % for AD, AA and MBA respectively. Groundnut and wheat grown with application of the hydrogels showed no detectable residues of monomers in soil samples (total n = 60) near the root zone at the time of crop harvesting.

Determination of 35 prohibited pesticide residues in Saussurea costus by modified QuEChERS method based on multi-walled carbon nanotubes coupled with gas chromatography-tandem mass spectrometry

Saussurea costus, a perennial herb belonging to the Asteraceae family, is a vital ingredient in traditional Chinese medicine. Increased demands for the herb have led to its widespread cultivation in China, but the corresponding increase in pesticide use has raised concerns about pesticide residues. Such residues would affect the safety and global market potential of Saussurea costus. Thus, a simple method is crucial to detect pesticide residues. The QuEChERS technique, in combination with gas chromatography-tandem mass spectrometry (GC-MS/MS), is commonly used for residue detection. However, traditional adsorbents may be unable to purify complex herbal mixtures well, affecting accuracy and instrument performance. Choosing suitable purification materials for Saussurea costus samples with complex matrices is of significant importance. This study focused on the detection of 35 prohibited pesticides in Saussurea costus. A rapid detection method was established by combining the QuEChERS technique with GC-MS/MS and utilizing a combination of multiwalled carbon nanotubes (MWCNTs), octadecylsilane-bonded silica gel (C18), and anhydrous magnesium sulfate (MgSO4) as the purification adsorbent. The samples were extracted with acetonitrile, purified by an improved QuEChERS process, subjected to GC-MS/MS analysis in multiple reaction monitoring (MRM) mode, and quantified using the internal standard method. The purification effects of four materials (C18, MWCNTs, N-propyl ethylenediamine (PSA), and graphitized carbon black (GCB)) and their optimal dosages were investigated by considering the matrix characteristics of the samples. An orthogonal experimental design was employed to optimize the ratio of adsorbent combinations, and the optimal adsorbent combination was determined to be 450 mg of MgSO4, 400 mg of C18, and 50 mg of MWCNTs. Matrix effect (ME) evaluation of the S. costus matrix showed that 31 target compounds strongly exhibited matrix-enhancement effects. Thus, matrix-matched calibration was employed in this study. Methodological investigation revealed that the standard curves for the 35 pesticides exhibited good linearity, with correlation coefficients (r2) greater than 0.9970. The average recoveries at three spiked levels ranged from 69.6% to 126.9%, and the relative standard deviations (RSDs) for parallel groups were all less than 10%. The limits of detection (LODs) and quantification (LOQs) ranged from 0.2 to 5.4 μg/kg and from 0.6 to 18.1 μg/kg, respectively. The developed method was used to screen and detect 35 pesticide residues in 20 batches of S. costus samples, and the target compounds were detected in six batches. The proposed method is simple, sensitive, and accurate. Thus, it is suitable for the rapid screening and detection of the 35 pesticide residues in S. costus and provides technical support for the cultivation, production, and quality control of the herb.

Determination of 197 pesticide residues in edible vegetable oil by gas chromatography-time-of-flight mass spectrometry

建立了气相色谱-飞行时间质谱(GC-TOF-MS)同时测定食用植物油中197种农药残留的方法。样品经乙腈超声提取,冷冻除脂,C18和PSA吸附剂共同净化;目标物经HP-5MS UI毛细管柱(30 m×0.25 mm×0.25 μm)分离,电子轰击源电离,全扫描模式采集质谱信息;MassHunter软件对数据进行定性与定量分析,设置精确质量数偏差为±5×10-5,保留时间偏差为±0.1 min。实验考察了基质效应情况和方法学性能。结果表明,大多数农药表现出基质增强效应,需采用基质标准工作溶液进行定量。在优化的条件下,174种农药定量限可以达到0.01 mg/kg,占全部被测农药的88%,另外23种农药的定量限为0.025~0.1 mg/kg。除联苯的线性范围为2~100 μg/L外,其余农药的线性范围均为定量限~200 μg/L,相关系数(R2)均大于0.99。在3个添加水平(0.1、0.25和0.5 mg/kg)下,有156种农药的回收率为70%~120%,占全部被测农药的79%,有185种农药的相对标准偏差<10%,占全部被测农药的94%。应用该方法对23份市售植物油样品进行了检测,结果在12个样品中检出13种农药。该方法操作简便,一次进样即可实现近200种农药的同时检测,且检测结果的准确度和灵敏度良好,适用于食用植物油中197种农药残留的快速检测。

Determination of chloramphenicol in meat samples using liquid chromatography-tandem mass spectrometry.

Chloramphenicol (CAP), a bacteriostatic antibiotic, is used for the treatment of bacterial infections in human and animals. Continual exposure of CAP residues into animal tissues may lead to antibiotic resistance. For the protection of humans and animals from this problem, a fast and highly sensitive analytical method based on ultra‐high‐performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) was developed and validated in this study for the quantitative determination of CAP in poultry meat and beef samples. Quick, easy, cheap, effective, rugged, and safe (QuEChERS) method was used for the extraction of CAP residues. The developed method was validated in terms of linearity, accuracy, precision, and specificity. Poultry meat and beef samples were extracted with 20 ml water–acetonitrile (1:1, v/v) and cleaned up by MgSO4, primary secondary amine, and C18 powder. The method was found to be linear in a wide concentration range, with correlation coefficient of higher than 0.999. The repeatability and reproducibility of this method were satisfactory. The achieved limit of detection and limit of quantification were 0.16 and 0.50 ng/g, respectively. Recoveries were estimated at 5 and 10 ng/g spiking levels in the range of 99%–111% with the coefficient of variation 0.48%–12.48% for spiked samples, and the matrix enhancement effects were mild in the range of 80%–85%. In this study, the levels of CAP residue in tested real samples were found below the detection limit. The method proved to be suitable for CAP determination in all kinds of samples tested and also efficient for the application of routine analysis.

Determination of 118 pesticide residues in dried wolfberry by gas chromatography-triple quadrupole mass spectrometry in dynamic multiple reaction monitoring mode

枸杞中丰富的营养物质深受广大消费者喜爱,但也极易受到病虫侵害,农药残留问题引起了人们的广泛关注。基质干扰是微量分析的一个难点,高灵敏度和高选择性的色谱-串联质谱技术是复杂基质中微量分析强有力的工具,动态扫描监测模式的优越性逐渐取代传统的多反应监测扫描模式,简便、快速、省时的QuEChERS前处理方法已被广泛应用于食品的农药残留检测中。采用改良QuEChERS法结合动态多反应监测模式(dMRM),建立了同时检测枸杞干果中118种农药残留的气相色谱-三重四极杆质谱分析方法。实验比较了不同加水量、提取溶剂、提取过程中温度提取条件,以及无水硫酸镁吸水剂、乙二胺-N-丙基硅烷化硅胶PSA、十八烷基硅烷键合硅胶C18净化填料添加量时农药的回收率,确定出最优前处理方法。结果表明,5 g样品经10 mL超纯水复水,用10 mL乙腈浸提,于-18 ℃冷冻10 min后,用缓冲体系盐包提取后,经800 mg无水硫酸镁、150 mg PSA、150 mg C18混合填料净化,基质匹配外标法定量。118种农药在一定范围内线性关系良好,相关系数R2≥0.9923,检出限和定量限分别为0.006~28.344 μg/kg和0.021~94.480 μg/kg, 4个添加水平的回收率为64.97%~126.21%, RSDs均小于19%(n=6)。基质效应考察结果表明,82%的农药呈现为基质增强效应,其他为基质抑制效应;9%的农药表现为强基质效应,其他为中等或弱基质效应;采用基质匹配标准曲线校正,可有效降低基质效应的影响。应用建立的方法测定10批枸杞样品,全部样品有农药检出,共检出农药22种。该方法操作简便快速,准确可靠,适用于枸杞干果中农药多残留的日常检测和快速筛查。

Fe3O4 nanoparticles as matrix solid-phase dispersion extraction adsorbents for the analysis of thirty pesticides in vegetables by ultrahigh-performance liquid chromatography-tandem mass spectrometry

Herein we report the first example of Fe3O4 nanoparticles (FNPs) being used as single-matrix solid-phase dispersion (MSPD) adsorbents for the extraction of 30 representative pesticides from vegetables. This study was aimed at analyzing the extracted samples using ultrahigh-performance liquid chromatography–tandem mass spectrometry (UHPLC-MS/MS). Various condition parameters, such as the eluent, volume of the eluent, and amount of FNPs were optimized to achieve good sensitivity and precision for the elution and extraction of the analytes. The developed method was validated using matrices consisting of eight vegetables (lettuce, cucumber, carrot, tomato, pepper, shallot, Chinese flowering cabbage, and cabbage) spiked with 30 pesticides at concentrations of 0.01, 0.1, and 1.0 mg/kg. The recoveries of the 30 pesticides (organophosphorus, triazole, carbamate, nicotine, amide, and other different structures of pesticides) were in the range 71.0–110.8% (n = 5) (except those of prothioconazole and dinotefuran), with relative standard deviations lower than 13.5% in all the matrices under optimal conditions. The matrix effects were observed by comparing the slope of the matrix-matched standard calibration curve with that of the solvent. However, the matrix effects of the eight vegetables did not show evident regularities. For pepper, tomato, and shallot, a sizable number of pesticides (24, 21, and 21, respectively) showed suppressive matrix effects. On the other hand, for cucumber, Chinese flowering cabbage, and cabbage, a good number of pesticides (19, 18, and 15, respectively) showed negligible matrix effects. Furthermore, for carrot matrices, 21 pesticides showed a matrix enhancement effect. Excellent linearity was achieved at pesticide concentrations of 0.01–1.0 mg/L, and the limits of quantification (LOQ) for the developed method reached 0.01 mg/kg (except that for dinotefuran, which was 0.1 mg/kg), based on the spiked test. The developed method was successfully employed in the analysis of real samples in Nanning, China, and three pesticide residues (halosulfuron methyl, tebuconazole, and azoxystrobin) were commonly detected in vegetable samples. In the present study, a reliable method-validation performance and excellent cleanup effects were observed by using the modified MSPD method consisting of the FNPs in the cleanup step.

Determination of sulfur in Soils and Stream Sediments by Wavelength Dispersive X-ray Fluorescence Spectrometry

A simple, rapid and nondestructive wavelength dispersive X-ray fluorescence spectrometry (WD-XRF) was developed for the determination of sulfur in soils and stream sediments. WD-XRF was used to study the spectral line shifts and matrix effects of different inorganic species such as sulfide, elemental sulfur, thiosulfate, sulfite and sulfate. Analysis of the spectral lines in the S Kα wavelength range confirmed that Mo Lα (2θ = 111.799 °) lines interfered with S Kα (2θ=110.683°) lines. Twenty-seven soils and stream sediments reference samples were used to calibrate and evaluate the analytical method and the detection limit for sulfur was 5.43 mg/kg. The relative error (%RE) of the reference samples was −8.3–6.4%, showing good accuracy. However, the single form of sulfur (sulfide, sulfite and sulfate) had a significant matrix enhancement effect in the sodium carbonate matrix, especially for sulfides, and its relative error was 11.9 ~ 26.9%. The results of WD-XRF, inductively coupled plasma emission spectroscopy (ICP-OES) and elemental infrared analyzer were compared. The fitness for purpose of the results was also evaluated by the quality criteria test proposed by the International Geological Correlation Programme (IGCP), from which it can be deduced that the method was adequate considering geochemical mapping application.

Determination of polycyclic aromatic hydrocarbons (PAHs) in cosmetic products by gas chromatography-tandem mass spectrometry

A gas chromatography coupled with tandem mass spectrometry (GC-MS/MS) method is developed to determine 18 representative polycyclic aromatic hydrocarbons (PAHs) in cosmetics, including Benzo[a]pyrene (BaP) and others. The method offers high sensitivity and selectivity under selected reaction monitoring (SRM) mode to satisfy the requirements of both quantitation and qualitation. The extraction solvent system used in this study is acetone/hexane 1:1 (v/v) and other purification procedure is unnecessary. The linearities of 18 PAHs are validated in different concentration in the range of 0.25–20 ng/mL individually with coefficient correlation (r) higher than 0.996. The recoveries for spiking 3 different concentrations are from 87.40% to 120.44% for 18 PAHs and the coefficient of variation (CV) are below 12.32%. Limit of quantification (LOQ) of 18 PAHs is in the range of 0.05–0.2 mg/kg. A matrix enhancement effect is observed and can be compensated with deuterated internal standard. The method has been successfully applied to 73 samples, over 40 of them are lipsticks. The results show none of the samples detect Benzo[a]pyrene (BaP) and Dibenzo[a,h]anthracene (DBA), both are classified as the most carcinogenic. 8 PAHs are detected and the average value between 0.08 and 0.27 mg/kg. This study offers a sensitive and simple method to analyze 18 representative PAHs successfully and can be applied to cosmetic products and raw materials.

Determination of enhancement effects at the compton to coherent scattering intensities x-rays using fe-cu and fe-zn binary compounds with wdxrf

Matrix enhancement effects have been examined with scattered X-rays by using WDXRF system for Fe-Cu and Fe-Zn binary compounds. Fe as analyte and elements which some of them the K absorption edge just below the characteristic K X-ray energies of the analit (Fe) as matrix have been chosen. Pure and binary with Fe ratio ranging from 10% to 90% samples were prepared with these elements. These samples have been analyzed in WDXRF system. At the end of measurement, the coherent and Compton scattering X-rays data of Rh Kα Xrays from these samples have been obtained. Matrix enhancement effects have been examined by calculating coherent / Compton scattered X-rays intensity ratio.

Quick, easy, cheap, effective, rugged, and safe sample preparation approach for pesticide residue analysis using traditional detectors in chromatography: A review.

In pesticide residue analysis, relatively low-sensitivity traditional detectors, such as UV, diode array, electron-capture, flame photometric, and nitrogen-phosphorus detectors, have been used following classical sample preparation (liquid-liquid extraction and open glass column cleanup); however, the extraction method is laborious, time-consuming, and requires large volumes of toxic organic solvents. A quick, easy, cheap, effective, rugged, and safe method was introduced in 2003 and coupled with selective and sensitive mass detectors to overcome the aforementioned drawbacks. Compared to traditional detectors, mass spectrometers are still far more expensive and not available in most modestly equipped laboratories, owing to maintenance and cost-related issues. Even available, traditional detectors are still being used for analysis of residues in agricultural commodities. It is widely known that the quick, easy, cheap, effective, rugged, and safe method is incompatible with conventional detectors owing to matrix complexity and low sensitivity. Therefore, modifications using column/cartridge-based solid-phase extraction instead of dispersive solid-phase extraction for cleanup have been applied in most cases to compensate and enable the adaptation of the extraction method to conventional detectors. In gas chromatography, the matrix enhancement effect of some analytes has been observed, which lowers the limit of detection and, therefore, enables gas chromatography to be compatible with the quick, easy, cheap, effective, rugged, and safe extraction method. For liquid chromatography with a UV detector, a combination of column/cartridge-based solid-phase extraction and dispersive solid-phase extraction was found to reduce the matrix interference and increase the sensitivity. A suitable double-layer column/cartridge-based solid-phase extraction might be the perfect solution, instead of a time-consuming combination of column/cartridge-based solid-phase extraction and dispersive solid-phase extraction. Therefore, replacing dispersive solid-phase extraction with column/cartridge-based solid-phase extraction in the cleanup step can make the quick, easy, cheap, effective, rugged, and safe extraction method compatible with traditional detectors for more sensitive, effective, and green analysis.

Analysis of ustiloxins in rice using polymer cation exchange cleanup followed by liquid chromatography–tandem mass spectrometry

Ustiloxins are cyclopeptide mycotoxins produced by the pathogenic fungus Ustilaginoidea virens of rice false smut. Quantification of ustiloxins is essential to assess the food safety of rice infected by rice false smut disease. This paper describes a sensitive method for the simultaneous quantification of ustiloxins A, B, C, D and F in rice grains using liquid chromatography–tandem mass spectrometry (LC–MS/MS). Since notable matrix enhancement effects (21%–78%) occurred for all of the target analytes (except for ustiloxin A), several solid phase extraction materials were tested for their ability to retain ustiloxins from aqueous solutions prior to the LC–MS/MS analysis, including C18 sorbents, polymer anion exchange sorbents resin (PAX), and polymer cation exchange resin (PCX). The PCX resin was adopted due to its higher extraction capability and selectivity for all targets compared to others, and in this case, almost no matrix effects (−5% to 8%) were observed for all of the ustiloxins monitored. The developed method reached limits of quantification of 0.2–2ngg−1, and linearity was statistically verified over two orders of magnitude with regression coefficients (R2)>0.991. The mean recoveries were from 85% to 109%, and the inter-day precisions (n=11) were less than 16%, with intra-day precisions (n=6) within 12%. Analysis of samples showed that ustiloxin A was the dominant species, with the content ranging from 5.5 to 273.8ngg−1, followed by ustiloxin B (≤88.7ngg−1), while concentrations of ustiloxins C, D and F were slightly lower (≤43.2ngg−1). To our knowledge, this is the first report on the determination and analysis of five ustiloxins simultaneously in a single analysis.

新型固相抽出カラムによるGC-MSにおけるマトリックス除去効果とマトリックス効果の抑制

新型固相抽出カラムによるGC-MSにおけるマトリックス除去効果とマトリックス効果の抑制

Consequences of the matrix effect on recovery of dinotefuran and its metabolites in green tea during tandem mass spectrometry analysis

Determining the residues of dinotefuran and its metabolites (MNG, UF, and DN) is highly problematic because of their polar characteristics. Additionally, tea contains many compounds that can interfere with residue analysis. Thus, the aim of the present study was to refine the extraction method that assures good recoveries for dinotefuran and its metabolites and removes most of the matrix components in green tea using liquid chromatography–tandem mass spectrometry (LC/MS/MS). We attempted to increase the extraction efficiency of the QuEChERS method by selecting the appropriate solvents among ethyl acetate, acetone, isopropanol, 25% methanol in acetonitrile, and methanol. We found that methanol was the best extraction solvent for dinotefuran and its polar metabolites in dry green tea samples; however, due to a limitation of an appropriate partitioning salt, acetonitrile was used as the extraction solvent. Matrix enhancement and suppression effects were observed for all analytes, which made the recovery rates variable. DN recovery was <70% when compared with matrix-matched calibration, whereas it was within the acceptable range (70–120%) when compared with solvent calibration. The opposite was observed for MNG and dinotefuran due to a matrix suppression effect. UF recovery was consistent in both matrix-matched and solvent calibrations despite having little suppressive effect. The method was successfully applied and dinotefuran and its metabolite residues were found in field-incurred green tea samples. The current findings suggest that using methanol as an appropriate QuEChERS solvent for problematic polar pesticides and investigating a suitable partitioning salt would considerably strengthen the practical impact of such data.

A matrix sensitive gas chromatography method for the analysis of pymetrozine in red pepper: Application to dissipation pattern and PHRL

A gas chromatography (GC) method for the analysis of pymetrozine was developed after utilizing matrix enhancement effect of pymetrozine to nitrogen phosphorus detector (NPD). Samples were extracted with acetonitrile and purified through primary secondary amine (PSA) and C18 dispersive sorbent. Matrix-matched calibration curve prepared after spiking standard pymetrozine across the studied range of concentrations (0.003–1.0mg/L) into blank red pepper extract was excellent with a determination coefficients (R2)=1. Recovery studies were carried out at three concentration levels (0.04, 0.4, and 2.0mg/kg, n=3) and the rates were ranged between 77.2% and 109.1%, with relative standard deviations ranged from 1.3% to 16.4%. The developed method was applied to field samples to characterize the dissipation pattern, half life, and pre-harvest residue limits (PHRL). The dissipation rates of the analyte were ascribed to first-order kinetics with half-life of 2.7 and 2.5days for recommended and double the recommended doses. From the PHRL curve, we could predict that if the residue level of pymetrozine is below the 1.23mg/kg at 10days or 0.71mg/kg at 7days before harvest, then the residues will be below the maximum residue limits (MRL=0.2mg/kg) established by the Korea Food and Drug Administration (KFDA).

Vitamin D and 25-hydroxyvitamin D determination in meats by LC–IT-MS

This paper reports a method for the rapid, sensitive and simultaneous analysis of vitamin D (Vit D) and 25-hydroxyvitamin D (25OH-Vit D) in meats. Samples were saponified and underwent solid phase extraction with analysis by normal phase liquid chromatography (LC) with ion trap mass spectroscopy (IT-MS), using positive polarity atmospheric pressure chemical ionisation (APCI). Limits of detection (LOD) and quantification (LOQ) for Vit D and 25OH-Vit D were 0.03 and 0.05μg/100g respectively. Deuterium labelled Vit D and 25OH-Vit D internal standards were added as surrogates prior to saponification, correcting for extraction inefficiencies and potential MS matrix enhancement or suppression effects. Recoveries using internal/surrogate standard correction ranged from 80% to 100% for all vitamers. Measurement uncertainty ranged from 6% to 15% for all vitamers in this method. This process required only 7.5g of sample per extraction and a batch of 28 extractions could be completed in six hours.

Development of a Screening Method for the Determination of PCBs in Water Using QuEChERS Extraction and Gas Chromatography-Triple Quadrupole Mass Spectrometry

A new method has been developed and validated for the simultaneous analysis of 11 polychlorinated biphenyls (PCBs), in water samples at trace levels by gas chromatography coupled to triple quadrupole mass spectrometry (GC-QqQ-MS/MS). Water samples were extracted by the QuEChERS (Quick Easy Cheap Effective Rugged and Safe) method. The QqQ analyzer acquired data in multiple reactions monitoring (MRM), permitting both quantification and confirmation in a single injection with a running time reduced up to 11.0 min. The effect of matrix interferences in extracts on analyte quantification and the identification of PCBs in water samples was deeply studied. The results showed that PCBs were prone to strong matrix interactions in water samples, and the quantification and identification of PCBs were highly affected by a matrix enhancement effect. To evaluate the performance of the method, validation experiments were carried out on water samples at three spiking levels (1.6, 8.0, 40.0 µg L(-1)). Recovery was in the range of 95 - 109% at 1.6 µg L(-1), 90 - 95% at 8.0 µg L(-1) and 97 - 102% at 40.0 µg L(-1), respectively. Precision values expressed as relative standard deviation (RSD) were lower than 15%. Linearity in the range of 0.5 - 50.0 µg L(-1) provided determination coefficients (R(2)) higher than 0.999 for all compounds. The limits of detection (LODs) for PCBs were ≤0.1 µg L(-1) and the limits of quantification (LOQs) ranged from 0.04 to 0.3 µg L(-1). The applicability of the proposed method to detect and quantify PCBs has been demonstrated in analyse of 15 real samples.

Using dried-droplet laser ablation inductively coupled plasma mass spectrometry to quantify multiple elements in whole blood

This paper describes a simple procedure for the direct analysis and determination of multiple elements in dried blood samples on a filter membrane using laser ablation coupled with inductively coupled plasma mass spectrometry (LA-ICP-MS). With this technique, we simultaneously quantified 13 elements in whole blood: Be, Mn, Co, Ni, Tl, Bi, Sb, Pb, Cu, Zn, Ba, Mg, and Cd. The measured accuracies was in agreement with the Seronorm CRM certified values, except for Mn, Zn, Ba and Cd, which presented absolute differences higher than the expanded uncertainty for these elements. The within-run precision was less than 5.7% (relative standard deviation, RSD), except for the analyses of Be, and Mn (8.6% and 11.1%, respectively). The reproducibility (between-run precision) was calculated in terms of the RSD obtained for 12 analyses (i.e., four replicates of each sample in three analytical runs). Apart from Be, Mn, and Zn, the reproducibilities of all the elements listed above ranged between 4.0% and 8.5%. In contrast, for Cd, the concentration obtained was significantly different from the certified value; analyses of this element exhibited low reproducibility. Applying the matrix-matched calibration method, the accuracy for Cd measured was in agreement with both SRM966 and BCR 635; thus, matrix-matched calibration is a practical means of overcoming matrix-enhancement effects for the quantification of Cd. Sample throughput (ca. 5 min per sample) made it possible to rapidly screen a larger number of samples relative to other techniques that require time-consuming sample preparation steps (e.g., removal of a portion of the solid sample or digestion).

Characterization of (13C24) T-2 toxin and its use as an internal standard for the quantification of T-2 toxin in cereals with HPLC–MS/MS

In this paper, the structure and the identity of fully 13C-substituted T-2 toxin were confirmed using high-resolution mass spectrometry, 1H-NMR, 13C-NMR, tandem mass spectrometry and HPLC-DAD. The purity of this compound was estimated to be at least 98.8% according to UV data. The isotopic distribution of (13C(24)) T-2 toxin indicated a total isotopic enrichment of 98.2 +/- 1.0 atom% 13C, and the application of different MS measurement modes revealed the MS/MS fragmentation pattern of T-2 toxin. Furthermore, a stable isotope dilution mass spectrometry method for the quantification of T-2 toxin was developed using (13C(24)) T-2 toxin as internal standard. The method was evaluated with and without conventional clean-up and validated for maize and oats. Both cereals showed strong matrix enhancement effects, which could be compensated for through the application of the isotope-substituted internal standard.

Determination of Acephate in Human Urine

Acephate is a commonly used organophosphate insecticide applied on agricultural crops and in residential communities. Because very little acephate is metabolized prior to excretion, the parent pesticide compound can be measured in human urine. The residue method must be sensitive enough to determine human exposure and potential health risk for both agricultural workers and their families who may be exposed by pesticide drift or by inadvertent carry-home residues. A reliable and sensitive method was developed to measure acephate concentrations in human urine. Urine was diluted with water and acetone, adjusted to a neutral pH, and partitioned twice in acetone-methylene chloride (1 + 1, v/v), with NaCl added to aid separation. The solvent-reduced organic phase extracts were clarified by activated charcoal solid-phase extraction and then adjusted to a final volume with the addition of a D-xylose analyte protectant solution to reduce matrix enhancement effects. Acephate concentrations in urine were determined by gas chromatography using pulsed flame photometric detection. The method limit of detection was established at 2 microg/L, with a method limit of quantitation of 10 microg/L. The average recovery from urine fortified with 10-500 microg/L was 102 +/- 12% (n = 32).

Determination of chlorpyrifos 20% EC (Dursban 20 EC) in scented rose and its products

The method for determination of chlorpyrifos is validated and dissipation behaviour of residue in scented rose and percent transfer in different products is described. GC–electron-capture detection with a HP-1, 30 m × 0.53 mm, 3.0 μm capillary column and nitrogen at 1 ml/min was used in the study. Plant matrices studied were: leaves, flowers, soil, rose water, absolute and concrete. Detector response linearity and sensitivity, limit of detection and determination, percent recovery were determined based on area response (mm2) of the standard. Analytical field and laboratory samples (rose water by hydro-distillation of the flowers, concrete and absolute by hexane extraction and condensation) were analysed for evaluation of the method. Samples were extracted with acetone, partitioned with water, saturated sodium chloride solution and dichloromethane. The organic layer was rotary-evaporated to 2 ml for cleanup with silica–carbon column. The column was eluted with dichloromethane–toluene–acetone (10:2:2, v/v/v) and the derived solution was rotary-evaporated to 5 ml for end analysis. Matrix enhancement effect was observed for leaf and soil samples for which corrective approach was followed to compensate for overestimation of the residue. Limit of detection for chlorpyrifos standard was 0.05 mg/l with good linearity of detector response (R2 = 0.99). Percent recovery ranged from 78 to 117% in different plant matrices (fortification level 1, 4 and 8 mg/l). Dissipation behaviour showed that chlorpyrifos was below detection limit by the 12th day of application on the scented rose with half life of 3.40 days on leaves and 3.10 days on flowers at 0.1% dosage. Percent transfer studies showed that 5.71, 46.91 and 38.80% of the residue from flowers was transferred to rose water, concrete and absolute, respectively.