Validation of an enzyme-linked immunosorbent assay (ELISA) for the determination of 4-nonylphenol and octylphenol in surface water samples by LC-ESI-MS

4-Nonylphenol (NP) and octylphenol (OP) were measured by direct ELISA in both laboratory-fortified and surface water samples collected monthly from 10 rivers. In this procedure, samples were concentrated by solid phase extraction (SPE) using Lichrolut RP-18 sorbent with good recoveries obtained for both LC-MS and ELISA, giving a low level of detection (LOD) at the range of low μg L⁻¹ and good reproducibility. Analysis of 40 surface water samples demonstrated that the ELISA may be a useful screening tool for the determination of the alkylphenols in surface water matrices. The concentration of NP and OP in surface waters ranged from 0.11 to 6.58 μg L⁻¹. A good correlation of results obtained by ELISA and LC-MS within the concentration range of 0.08-6.86 μg L⁻¹ was found in the river samples [R² = 0.924, n = 39]. The influence of various factors on assay determination was also discussed.     

A new competitive enzyme-linked immunosorbent assay (ELISA) for determination of estrogenic bisphenols

Bisphenol A and other hydroxylated diphenylalkanes (generally known as bisphenols) have been identified as potential estrogenic substances. In this paper, a specific polyclonal antibody was produced against these compounds by immunization of rabbits with a conjugate of 4,4-bis (4-hydroxyphenyl) valeric acid and bovine serum albumin (BHPVA-BSA). The polyclonal antibody showed specific recognition of the bisphenol structure, while the cross reactions of other common phenolic compounds such as phenol, hydroquinol and p-hydroxybenzoic acid were all lower than 1%. The linear range of bisphenol A calibration curve was 1–10 000 ng ml⁻¹. Real water samples and mouse serum samples were spiked with known amount of bisphenol A and measured by the competitive ELISA. Recoveries were between 92 and 105%. The detection limits were found to be 0.1 ng ml⁻¹ for real water samples and 2 ng ml⁻¹ for serum samples. The method is very useful for monitoring bisphenol compounds in environmental and biological samples.     

Development and validation of an SPE methodology combined with LC-MS/MS for the determination of four ionophores in aqueous environmental matrices

A multi-residue analytical methodology has been established for the determination of the four ionophores: lasalocid, monensin, salinomycin and narasin in aqueous environmental matrices, using nigericin as internal standard. The samples were filtrated prior to solid phase extraction. All compounds were measured using liquid chromatography coupled to tandem mass spectrometry applying electro spray ionisation. The absolute recoveries ranged from 92 to 110% (relative standard deviation: 2–14%) for spiked river water. The final method allowed for detection of ionophores down to a few ng/L in natural water bodies with LOQs for the entire methodology being 40, 49, 67, and 14 ng/L for lasalocid, monensin, salinomycin, and narasin, respectively.     

Development of an enzyme-linked immunosorbent assay for pentachlorophenol

Pentachlorophenol (PCP) is a hazardous pollutant with toxicity and potential carcinogenic properties being a serious threat to the environment. In this work, the development of an immunoassay for PCP is presented. A hapten was synthesised and conjugated to protein for rabbit immunisation. Three polyclonal antibodies were obtained and the best results were achieved in the antibody-coated format using antiserum R3. Calibration range was 0.3–30.5 ng ml⁻¹, with an average I₅₀ value of 2.9 ng ml⁻¹ and a detection limit of 0.1 ng ml⁻¹. The specificity of the assay was tested against PCP structurally related compounds. The method is highly specific for PCP and shows low cross-reactivity (CR) for chlorine-containing phenols, nitrophenols, benzenic and piridinic compounds. The good recoveries achieved with different water samples indicate that this assay can be a good alternative method for the determination of PCP in this kind of samples.     

Ultra-trace determination of aquaculture chemotherapeutants and degradation products in environmental matrices by LC-MS/MS

Two of the most common products currently used to control parasitic sea lice in fin fish aquaculture, salmon in particular, are Slice® and AlphaMax®. Emamectin benzoate (EB) is the active ingredient in Slice® and deltamethrin is the active ingredient in AlphaMax®. Several analytical methods have been developed for the determination of the active ingredients in these products but these have been focused on specific matrices and lack the sensitivity and versatility required in environmental monitoring. Here we present a validated, versatile, and simple analytical method for the determination of EB, its desmethyl degradation product (AB), and deltamethrin in a wide range of environmental matrices (sea water, marine sediment, and tissue). Sediments and tissues were extracted by accelerated solvent extraction (ASE®) and sample cleanup was achieved by solid phase extraction (SPE) while sea water was extracted using SPE disks. Analyte identification and quantification was based on liquid chromatography tandem mass spectrometry (LC-MS/MS) instrumentation with electrospray ionization, and multiple reaction monitoring (MRM). Method detection limits for the target analytes was in the parts per trillion (pg?g^?1) level for tissue and sediment and parts per quadrillion (pg?L^?1) for water. Except for deltamethrin in sea water, method performance in terms of analyte recoveries was better than 60%, and the method precision was RSD<20%. The method was used to determine EB and AB concentrations in water, sediment and prawn tissue samples collected near salmon aquaculture sites treated with Slice®. A distinct concentration gradient was observed in the immediate vicinity (within 50 to 100?m radius) of the salmon aquaculture sites where EB was detected at low ng?g^?1 levels for tissue (EB ranged from 0.041 to 3.0?ng?g^?1) and sediment (EB ranged from 0.051 to 35?ng?g^?1) and pg?L^?1 levels (EB ranged from 3 to 209?pg?L^?1) for water samples.     

Automated flow enzyme-linked immunosorbent assay (ELISA) system for analysis of methyl parathion

Sensitive detection of pesticides is of utmost importance in environment and food analysis. Immunological methods are widely used to detect pesticides in agricultural and environmental samples wherein antibodies are employed against the target molecules. Accurate diagnosis depends on the affinity and specificity of the antibody preparation used, and high affinity antibodies are essential for the detection of very small amounts of pesticides. Enzyme linked immuno sorbent assay (ELISA) coupled with flow injection analysis (FIA) technique provides a very high sensitivity with high throughput of analyses. Automation of this analysis scheme ensures precise detection with high accuracy. The present development aims at providing a user-friendly system for achieving this objective. It employs a 8952 microcontroller for precise flow of reagents, samples, substrate and conjugates used for analysis to be passed through an immobilized antibody column at predetermined time. With the sequence and flow control of buffers used, it also provides the option for reuse of the immobilized antibody column. The system is flexible to accommodate multiple sequences up to a maximum of 99 steps. It is customizable for different flow ELISA applications. It can control up to eight solenoid valves (dc 24 V) and two peristaltic pumps and has one 12 bit analog channel for data acquisition. With the serial interface port, the system provides convenient means for data acquisition into the computer. The system has been successfully tested for immuno analysis of organophosphorous pesticide methyl parathion.     

Development of a solid-phase extraction—enzyme-linked immunosorbent assay method for the determination of estrone in water

Estrone has been identified as a potential endocrine-disrupting chemical (EDC). To facilitate its analysis, a highly selective and sensitive enzyme-linked immunosorbent assay (ELISA) method with a simple solid-phase extraction (SPE) for analysis of estrone in aquatic environments has been developed. The specific polyclonal antibody was produced against a conjugate of estrone-3-hemisuccinate and keyhole limpet hemocyanin (KLH). The obtained ELISA showed specific recognition of estrone, without cross-reactions for three other major estrogenic compounds (17β-estradiol, estriol, and 17α-ethynylestradiol) commonly found in water. The ELISA had a limit of detection of 0.14 μg/l estrone in water. Combining a SPE method to extract and pre-concentrate estrone from water samples and ELISA to specifically quantify estrone content, the SPE-ELISA can detect estrone down to 1.25 ng/l level in water. Good recovery with spiked river water was obtained with this SPE-ELISA method. The developed SPE-ELISA system was applied to analyze the real influent and effluent samples of sewage treatment plant in Penrith (Australia) and the results correlated well with those obtained using GC and HPLC methods. The developed SPE-ELISA method is capable of being applied for the specific detection and routine monitoring of estrone in environmental water samples.     

Improved methods for urinary atrazine mercapturate analysis--assessment of an enzyme-linked immunosorbent assay (ELISA) and a novel liquid chromatography-mass spectrometry (LC-MS) method utilizing online solid phase extraction (SPE)

Elimination of interfering substances in urine by solid phase extraction (SPE) prior to analysis resulted in 10-fold improvement in the sensitivity of atrazine mercapturate (AM) enzyme-linked immunosorbent assay (ELISA) compared to previous reports. Of the two tested SPE systems, Oasis^® HLB and MCX, the mixed-mode MCX gave good recoveries (82%) of AM in spiked samples measured by ELISA, whereas the reverse-phase HLB phase was not compatible with the immunochemical method. At relatively high concentrations of urinary AM (>20 ng mL⁻¹), sample dilution was effective enough for the elimination of interfering substances. The new liquid chromatography-mass spectrometry (LC-MS) method developed for AM utilizes online-SPE with Oasis^® HLB, column switching and a stable-isotope internal standard. The limit of quantification (0.05 ng mL⁻¹) indicates improved sensitivity compared with most previously published LC-MS methods for AM. Validation of all three methods, LC-MS, ELISA + SPE and ELISA + dilution with spiked urine samples showed good correlation between the known and measured concentrations with R² values of 0.996, 0.957 and 0.961, respectively. When a set (n = 70 plus 12 blind duplicates) of urine samples from farmers exposed to atrazine was analyzed, there was a good agreement (R² = 0.917) between the log normalized data obtained by ELISA + SPE and LC-MS. High correlation among the data obtained by the two tested methods and the LC-MS method by the Center of Disease Control and Prevention (CDC), together with low variability among the blind duplicates, suggests that both methods reported here would be suitable for the analysis of urinary AM as a biomarker for human exposure of atrazine.     

LC-MS/MS法快速高效检测尿液中尼古丁及其9种代谢物

以氘代尼古丁、氘代可的宁、3-OH-氘代可的宁、氘代尼古丁葡萄糖醛酸复合物、氘代可的宁葡萄糖醛酸复合物、3-OH-氘代可的宁葡萄糖醛酸复合物作内标, 在LC-MS/MS的大气压化学电离(APCI)离子化模式下, 建立了快速检测吸烟者尿液中尼古丁及其9种代谢物的方法, 并对19个实际样品进行了测试和判别分析(DA). 实验前处理简单, 色谱运行时间仅为3.8 min. 结果表明, 尼古丁及其代谢物的精密度在0.5%～5.5%之间, 回收率在94%～109%之间, 线性相关系数均大于0.995. DA分析充分区别开了不同量的吸烟者, 进一步的相关性分析表明吸烟者24 h尿液中的尼古丁及其9种代谢物含量与卷烟抽吸量的分析因子之间均有较强正相关性.     

Multiresidue method for the determination of 13 pesticides in three environmental matrices: water, sediments and fish muscle

Pesticides residues in aquatic ecosystems are an environmental concern which requires efficient analytical methods. In this study, we proposed a generic method for the quantification of 13 pesticides (azoxystrobin, clomazone, diflufenican, dimethachlor, carbendazim, iprodion, isoproturon, mesosulfuron-methyl, metazachlor, napropamid, quizalofop and thifensulfuron-methyl) in three environmental matrices. Pesticides from water were extracted using a solid phase extraction system and a single solid-liquid extraction method was optimized for sediment and fish muscle, followed by a unique analysis by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). Limits of quantification were below 5 ng L⁻¹ for water (except for fluroxypyr and iprodion) and ranged between 0.1 ng g⁻¹ and 57.7 ng g⁻¹ for sediments and regarding fish, were below 1 ng g⁻¹ for 8 molecules and were determined between 5 and 49 ng g⁻¹ for the 5 other compounds. This method was finally used as a new routine practice for environmental research.     

Development and evaluation of an enzyme-linked immunosorbent assay (ELISA) method for the measurement of 2,4-dichlorophenoxyacetic acid in human urine

An enzyme-linked immunosorbent assay (ELISA) method was developed to quantitatively measure 2,4-dichlorophenoxyacetic acid (2,4-D) in human urine. Samples were diluted (1:5) with phosphate-buffered saline containing 0.05% Tween and 0.02% sodium azide, with analysis by a 96-microwell plate immunoassay format. No clean up was required as dilution step minimized sample interferences. Fifty urine samples were received without identifiers from a subset of pesticide applicators and their spouses in an EPA pesticide exposure study (PES) and analyzed by the ELISA method and a conventional gas chromatography/mass spectrometry (GC/MS) procedure. For the GC/MS analysis, urine samples were extracted with acidic dichloromethane (DCM); methylated by diazomethane and fractionated by a Florisil solid phase extraction (SPE) column prior to GC/MS detection. The percent relative standard deviation (%R.S.D.) of the 96-microwell plate triplicate assays ranged from 1.2 to 22% for the urine samples. Day-to-day variation of the assay results was within ±20%. Quantitative recoveries (>70%) of 2,4-D were obtained for the spiked urine samples by the ELISA method. Quantitative recoveries (>80%) of 2,4-D were also obtained for these samples by the GC/MS procedure. The overall method precision of these samples was within ±20% for both the ELISA and GC/MS methods. The estimated quantification limit for 2,4-D in urine was 30 ng/mL by ELISA and 0.2 ng/mL by GC/MS. A higher quantification limit for the ELISA method is partly due to the requirement of a 1:5 dilution to remove the urine sample matrix effect. The GC/MS method can accommodate a 10:1 concentration factor (10 mL of urine converted into 1 mL organic solvent for analysis) but requires extraction, methylation and clean up on a solid phase column. The immunoassay and GC/MS data were highly correlated, with a correlation coefficient of 0.94 and a slope of 1.00. Favorable results between the two methods were achieved despite the vast differences in sample preparation. Results indicated that the ELISA method could be used as a high throughput, quantitative monitoring tool for human urine samples to identify individuals with exposure to 2,4-D above the typical background levels.     

液相色谱-串联质谱法测定食品中合成色素

提出了液相色谱-串联质谱法测定食品中8种合成色素柠檬黄、苋菜红、胭脂红、日落黄、诱惑红、亮蓝、赤藓红和偶氮玉红的含量。固体(半固体)样品经乙醇-氨水-水(70+1+29)溶液溶解,所得滤液烘干后用水溶解,经Waters Atlantis dC18色谱柱(2.1 mm×150 mm,5μm)分离,用甲醇和10 mmol.L-1乙酸铵溶液以不同体积比混合进行梯度洗脱,采用电喷雾正离子模式串联质谱检测。8种合成色素的质量浓度均在50μg.L-1以内与其峰面积呈线性关系,检出限(3S/N)在0.003～0.020 mg.kg-1之间。方法应用于食品样品中8种合成色素的测定,回收率在83.0%～112.0%之间,测定值的相对标准偏差(n=6)均小于5%。     

液相色谱-串联质谱法测定食品中甲基磺草酮

食品用乙腈-水(3+1)溶液进行提取,经凝胶色谱、固相萃取柱净化后,用液相色谱-串联质谱法进行测定和确证,外标法定量。色谱分离用甲醇和甲酸-水(0.1+99.9)溶液以不同体积比混合为流动相梯度洗脱,采用负离子模式电喷雾离子源在多反应监测模式下进行检测。甲基磺草酮的质量浓度在0.01~0.2 mg·L-1范围内与其峰面积呈线性关系。以4种食品样品为基体,加入3种浓度水平的甲基磺草酮标准做回收试验,测得回收率在73.2%~100.6%之间;测定值的相对标准偏差(n=10)在4.1%~11%之间。     

LC-MS/MS法定量测定人血浆中的氯氮平

建立了人血浆中氯氮平的固相萃取及LC-MS/MS定量检测方法.血浆中的氯氮平用固相萃取柱(Bond Elut Certify)萃取,采用Waters AtlantisTMd C18色谱柱,电喷雾离子源,正离子检测,多反应监测方式进行定量分析,SKF525a作为内标.对氯氮平的定量下限为100 ng/mL,氯氮平质量浓度...     

液相色谱-串联质谱法测定鸡饲料中硝基咪唑类药物

提出了鸡饲料中5种硝基咪唑类药物(甲硝唑、洛硝哒唑、二甲硝唑、替硝唑和奥硝唑)的液相色谱-串联质谱分析方法。鸡饲料样品经乙酸乙酯-5g.L-1碳酸钠混合溶液提取后,取有机相蒸发至干。用0.1mol·L-1磷酸溶液溶解残余物,HLB柱固相萃取净化,所得的乙腈洗脱液经C8色谱柱为分离柱,甲醇和水混合溶液为流动相作梯度淋洗,采用正离子模式多反应监测。5种硝基咪唑类药物的线性范围均为10～500μg.L-1,检出限(3S/N)均为10μg.kg-1。加标回收率为79.4%～91.3%,批内相对标准偏差(n=6)为5.5%～13.9%,批间相对标准偏差(n=6)为6.7%～18.2%。     

液相色谱-串联质联法测定食品用塑料包装中邻苯二甲酸酯类增塑剂

采用液相色谱-串联质谱法(LC-MS/MS)测定了食品用塑料包装材料中的3种邻苯二甲酸酯(DBP、BBP、DEHP)的含量。样品经正己烷超声提取后,以Hypersil Gold色谱柱为固定相,以甲醇-水(95+5)溶液为流动相进行洗脱,采用电喷雾正离子源-多反应检测模式检测。3种邻苯二甲酸酯的质量浓度在5.00~250μg·L-1范围内与其峰面积呈线性关系,方法的检出限(3S/N)在0.1~0.2μg·L-1之间。对空白样品进行加标回收试验,回收率在92.5%~101%之间,测定值的相对标准偏差(n=6)在4.6%~6.9%之间。     

Novel indirect enzyme-linked immunosorbent assay (ELISA) method to detect Total E. coli in water environment

In order to establish ELISA (enzyme-linked immunosorbent assay) method to detect Total E. coli in water environment, E. coli multi-characters antigens in water environment were prepared according to the characters of kinds of E. coli serotypes, including antigen of whole cell, antigen of disrupted whole cell, somatic antigen, flagellar antigen and fimbrial antigen. Total E. coli polyclonal antibodies were obtained from the New Zealand rabbits immunized with these five antigens, respectively. Antibodies generated in this research are with high titers and good purity, can conjugate with antigens, specifically, stably and strongly. Indirect ELISA shows the titers of antibody of whole cell and antibody of disrupted whole cell are both over 1 × 10⁵. The cross-reactivity of the antibody is from 12 to 30% which indicate the specificity of the antibody against Total E. coli. Based on these antibodies, we established indirect ELISA method to detect Total E. coli in water environment. The matrix effects were studied and the results show that there is no significant influence by all the factors. The ELISA result shows that the detection limitation could be 10⁴ CFU (colony forming units) L⁻¹. The indirect ELISA method developed in this study is well suited for Total E. coli analysis in real water samples as a rapid screen method.     

液相色谱-串联质谱法测定牛奶中11种真菌毒素残留量

采用液相色谱-串联质谱法测定牛奶中11种真菌毒素的残留量。样品经乙腈沉淀蛋白和提取,正己烷脱脂,无水硫酸钠干燥,M160型多功能净化柱净化。以Agilent Eclipse XDB-C18色谱柱为分离柱,以不同体积比的水和甲醇混合液为流动相进行梯度洗脱,采用多反应监测模式检测。11种真菌毒素的质量分数均在4.0μg·kg-1以内与其峰面积呈线性关系,方法的检出限(3S/N)在0.001~0.006ng之间。加标回收率在60.1%~95.2%之间,测定值的相对标准偏差(n=6)在3.2%~9.6%之间。     

液相色谱-串联质谱法测定桃中31种农药残留

取均质后的桃皮或桃肉,在匀浆机上用乙腈提取;加入氯化钠及硫酸镁振荡盐析;取上清液与PSA混匀并离心进行净化。取经滤膜过滤的滤液与水混匀后供液相色谱-串联质谱分析。用Agilent Eclipse plus C18 RRHT色谱柱为分离柱,用含甲酸的5mmol·L-1甲酸铵溶液与乙腈以不同比例的混合液作流动相进行梯度淋洗。质谱测定中采用电喷雾正离子源动态多反应监测模式进行检测。所测31种农药在一定质量分数范围内保持线性关系,方法的检出限(3S/N)在0.04~20μg·kg-1之间,回收率在73.6%~119%之间,测定值的相对标准偏差(n=6)在0.70%~17%之间。     

LC-MS/MS法快速测定吡罗昔康制剂中吡罗昔康含量

建立了快速液相色谱-质谱/质谱联用法测定吡罗昔康制剂中吡罗昔康含量的方法。样品以0.1 mol/L盐酸甲醇溶液提取、微孔滤膜过滤、离心后,通过电喷雾离子化(ESI),采用多反应检测(MRM)方式进行正离子检测,用于定量分析的检测离子为m/z 332.2→94.8。采用Shim-pack XR-ODS(3.0 mm×75mm,2.0μm)柱分离,以乙腈-水-甲酸(60:40:0.1,V/V/V)为流动相,流速为0.40 mL/min,在3 min内完成吡罗昔康定量分析。线性范围为2.5～1000.0ng/mL,最低检测限为2.5 ng/mL;日内测定的相对标准偏差小于3.2%,日间测定的相对标准偏差小于3.8%。方法可作为吡罗昔康制剂的质量中吡罗昔康控制方法,并可用于少量血浆样品的测定,也适用于药物代谢动力学研究。