固相萃取-液相色谱-三重四极杆串联质谱测定养殖废水中17种氟喹诺酮类抗生素

采用固相萃取-液相色谱-三重四极杆串联质谱(SPE-LC-MS/MS)技术,建立了养殖废水中17种氟喹诺酮类抗生素(FQs)的测定方法。水样在采用固相萃取法富集前,先用 0.45 μm 的聚四氟乙烯滤膜过滤,而后加入5%甲醇(体积比),用盐酸溶液将水样pH调节至2.0±0.5,经固相萃取柱富集,最后用9 mL 0.1%甲酸甲醇洗脱。以C18柱为分离柱,0.1%甲酸−5 mmol·L⁻¹ 甲酸铵水溶液和甲醇为流动相,采用液相色谱－三重四极杆串联质谱多反应监测离子模式(MRM)对目标化合物进行了检测和分析。在优化实验条件下,17种FQs的线性范围为0.50 -100 μg·L⁻¹时,目标化合物峰面积与内标物质峰面积之比与质量浓度的线性关系良好(R²>0.99),方法检出限为0.08-0.3 ng·L⁻¹。在加标量为0.01 μg·L⁻¹和0.09 μg·L⁻¹时,空白加标的平均回收率为58.6%-104.2% 和65.3%-91.0%,相对标准偏差(RSD)在2.1%-19.3%(n=6)。以养殖废水为基质,17种FQs的加标回收率在47.8%-118.7%,RSD小于20%(n=6)。应用该方法测定了广州某水产养殖场的养殖废水。结果表明,氧氟沙星检出浓度最高(9.36 ng·L⁻¹),达氟沙星次之(5.96 ng·L⁻¹)。该方法快速、准确,可适用于养殖废水中17种FQs的测定。     

用固相萃取-高效液相色谱-三重四极杆串联质谱法测定海洋沉积物中13种氟喹诺酮类抗生素

为进一步探索海洋沉积物中氟喹诺酮类抗生素的污染情况,基于固相萃取-高效液相色谱-三重四极杆串联质谱(SPE-LC-MS/MS)技术,建立了海洋沉积物中 13 种FQs的测定方法;采用高效液相色谱-三重四极杆串联质谱多反应监测离子模式(MRM)对FQs进行分离检测。结果表明：在优化实验条件下,13种FQs的质量浓度为0.50~100 μg·L⁻¹,目标化合物峰面积与内标物质峰面积之比与质量浓度的线性关系良好(R²>0.99),方法检出限为0.003~0.03 μg·kg⁻¹;在加标量为1 μg·kg⁻¹和10 μg·kg⁻¹时,空白加标的平均回收率为73.5%~124.6%和67.5%~118.5%,相对标准偏差(RSD)为1.0%~9.7%(n=7);以海洋沉积物为基质,13种目标物的加标回收率为67.7%~142.4%,RSD小于10.2%(n=6);使用该方法对广州某湾区海洋沉积物中 13 种 FQs 的残留量进行了实地检测,培氟沙星质量分数最高,为1.6 μg·kg⁻¹,氧氟沙星、环丙沙星和恩诺沙星质量分数次之,为0.7 μg·kg⁻¹。该方法实现了对海洋沉积物中 13种 FQs 的同时检测,具有快速、准确等优点,适用于海洋沉积物中13种FQs的测定。本研究成果可为海洋生态环境保护提供数据基础及技术支撑。     

Pilot scale application of a method for the analysis of perfluorinated compounds in surface soils

A growing number of studies now indicate that perfluorinated compounds (PFCs) are globally distributed in the environment. Their widespread distribution and presence in remote locations has led to questions about the importance of atmospheric and oceanic transport. Describing their distribution in surface soils is also an essential but neglected element in developing a comprehensive understanding of their occurrence in the environment. Soils are the critical link between global atmospheric and hydrologic processes where both local and distant contaminants can accumulate and be released into aquatic and terrestrial communities. Because PFC concentrations in soils will influence ground and surface water, wildlife, and crops, methods to accurately measure PFCs in soil are clearly needed. To help answer this need, we developed a method for the analysis of nine perfluorinated carboxylic acids and four perfluorinated sulfonic acids in soil. Samples from six nations (n = 10 per nation) were analyzed by LC-MS/MS to demonstrate the method performance parameters and to make preliminary observations about the occurrence of the PFCs in soils in different parts of the world. The resulting method shows acceptable performance characteristics for the target compounds in most soils while documenting the widespread occurrence of PFCs in surface soils.     

Development of in-house ELISA for detection of chloramphenicol in bovine milk with subsequent confirmatory analysis by LC-MS/MS

This study was undertaken to develop and validate direct competitive ELISA for the determination of chloramphenicol residues in bovine milk. Antisera and an enzyme-tracer for chloramphenicol were prepared and used to develop an ELISA with inhibition concentrations, IC₂₀ and IC₅₀, of 0.09 and 0.44 ng mL^?1, respectively. Milk samples were spiked with standards equivalent to 0, 0.2, 0.3, 0.5, 1.0 &; 1.5 ng mL^?1 and extracted in methanol. The mean recoveries were found to be 73–100% with coefficient of variance 7–11%. The decision limit (CCα) and detection capability (CCβ) were calculated as 0.10 and 0.12 ng mL^?1, respectively. The results were found comparable with the commercial ELISA, having recoveries of 87 to 100%, CCα 0.09 ng mL^?1 and CCβ 0.12 ng mL^?1. As per Commission Decision 2002/657/EC, in-house ELISA was further validated by using LC-MS/MS. Mass spectral acquisition was done by using electrospray ionization in the negative ion mode applying single reaction monitoring of the diagnostic transition reaction for CAP (m/z 152, 194 and 257). The calibration curve showed good linearity in concentrations from 0.025 to 1.6 ng mL^?1 with correction coefficient 0.9902. The mean recoveries were found to be 88 to 100%. The CCα was calculated as 0.057 ng mL^?1 and CCβ 0.10 ng mL^?1. Since CCα and CCβ are less than half of the MRPL (0.15 ng mL^?1), the test was found suitable for screening and quantification of CAP residues in bovine milk samples. Results of surveillance studies indicated that out of 31 analyzed milk samples, 12.9% samples were found with CAP residues but only 3.2% samples were declared positive with maximum concentration 0.31 ng mL^?1, slightly above the MRPL.     

Simple analytical method for determination of pesticide residues in human serum by liquid chromatography tandem mass spectrometry

The aim of this study was to develop an analytical method for the determination of residues of organophosphorus and carbamate pesticides which are widely used in Tunisia. This method involves a liquid-liquid extraction procedure followed by liquid chromatography tandem mass spectrometry (LC/MS/MS) for the identification and quantification of compounds. Ionization of molecules was performed by the electrospray mode. Multiple reactions monitoring (MRM) was the acquisition mode used for the monitoring of two MS/MS transitions for each compound. The average recoveries obtained, at three different fortification levels, ranged between 65% and 106% for most of the pesticides studied, except for methamidophos (lower than 25%).The linearity of the method was in the range of 5 to 50 μ g/L with a correlation coefficient from 0.995 to 0.999, depending on the analyte. The estimated limit of detection and limit of quantification were 2 μ g/L and 5 μ g/L, respectively. The precision of the analytical procedure was satisfactory and the coefficients of variation, evaluated at three concentration levels were lower than 15% for most pesticides studied. The application of the method was investigated in a population of agricultural workers chronically exposed to various pesticides some of which, such as carbofuran, carbendazim, methomyl and pirimicarb, were detected in some serum samples.     

Validation and global uncertainty of a gas chromatographic with mass spectrometry method for fenamidone analysis in grapes and wines

Fenamidone is an imidazolinone fungicide recently introduced in viticulture practices. This work reports the validation and assessment of global uncertainty of a gas chromatographic with mass spectrometry method to analyze fenamidone in grapes and wines. This method consists in a simple and fast liquid-liquid extraction step followed by chromatographic determination. Limits of detection for fenamidone in grapes and wines were, respectively, 0.05 mg/kg and 0.06 mg/L, precision was below 9.4% and average recovery was 89 ± 5%. In the concentration range from 0.05 to 1.00 mg/kg (or mg/L) of fenamidone, global uncertainty calculated following the EURACHEM/CITAC rules, and also by the Horwitz function, was below 25%. The EURACHEM/CITAC global uncertainty budget used gave lower estimates than those obtained from the Horwitz function.     

Validation of reliable and selective methods for direct determination of glyphosate and aminomethylphosphonic acid in milk and urine using LC-MS/MS

Simple high-throughput procedures were developed for the direct analysis of glyphosate [N-(phosphonomethyl)glycine] and aminomethylphosphonic acid (AMPA) in human and bovine milk and human urine matrices. Samples were extracted with an acidified aqueous solution on a high-speed shaker. Stable isotope labeled internal standards were added with the extraction solvent to ensure accurate tracking and quantitation. An additional cleanup procedure using partitioning with methylene chloride was required for milk matrices to minimize the presence of matrix components that can impact the longevity of the analytical column. Both analytes were analyzed directly, without derivatization, by liquid chromatography tandem mass spectrometry using two separate precursor-to-product transitions that ensure and confirm the accuracy of the measured results. Method performance was evaluated during validation through a series of assessments that included linearity, accuracy, precision, selectivity, ionization effects and carryover. Limits of quantitation (LOQ) were determined to be 0.1 and 10 µg/L (ppb) for urine and milk, respectively, for both glyphosate and AMPA. Mean recoveries for all matrices were within 89–107% at three separate fortification levels including the LOQ. Precision for replicates was ≤7.4% relative standard deviation (RSD) for milk and ≤11.4% RSD for urine across all fortification levels. All human and bovine milk samples used for selectivity and ionization effects assessments were free of any detectable levels of glyphosate and AMPA. Some of the human urine samples contained trace levels of glyphosate and AMPA, which were background subtracted for accuracy assessments. Ionization effects testing showed no significant biases from the matrix. A successful independent external validation was conducted using the more complicated milk matrices to demonstrate method transferability.     

Rapid and Sensitive LC/MS/MS Direct Injection Method for the Determination of Trace Level Corexit EC9500A Oil Dispersant in Seawater

A rapid and sensitive liquid chromatography tandem mass spectrometry (LC/MS/MS) method for the determination of trace dioctyl sulfosuccinate (DOSS) concentrations in seawater samples has been established. The method is well suited to aquatic environment impact monitoring following application of the dispersant Corexit EC9500A. Linearity of the method was demonstrated down to 0.05 ng/mL^?1 (0.05 µgL^?1) DOSS in seawater, with a 2.4% relative standard deviation precision for preparation replicates. A US EPA method limit of detection of <0.02 ng/mL^?1 (<0.02 µgL^?1) was calculated and specificity was confirmed by monitoring of two qualifier ions at 291.1 m/z and 227.1 m/z. These transitions were confirmed by QToF analysis to be associated with the DOSS precursor ion at 421.2 m/z. For application to seawater samples and samples containing oil particulates, a practical and repeatable calibration range of 0.5 ng/mL^?1 (0.5 µgL^?1) to 25.0 ng/mL^?1 (25.0 µgL^?1) DOSS is reported. The method was shown to have excellent precision and accuracy, with a consistent ≤1.6% relative standard deviation for system suitability standards at 0.5 ng/mL^?1 (0.5 µgL^?1) and linear weighted (1/x) regression coefficients of determination ≥0.995. The surfactant nature of the analyte is discussed in relation to detection limit and loss of analyte. Speculation of a relationship between DOSS in association or aggregation with divalent cations, such as Ca²⁺ present in salt water and hard water, is suggested. The consequent effects on cell ionic balance and membrane function are discussed.