Determination of eight selected organophosphorus insecticides in postmortem blood samples using solid-phase extraction and gas chromatography/mass spectrometry

A simple, rapid and sensitive method is described for the determination of omethoate, dimethoate, diazinon, chlorpyrifos, parathion‐ethyl, chlorfenvinphos, quinalphos and azinphos‐ethyl in postmortem whole blood samples. The analytes and internal standard (ethion) were isolated from the matrix by solid‐phase extraction, and were analysed by gas chromatography/mass spectrometry in the selected ion monitoring mode. The method has shown to be selective after analysis of postmortem samples of 40 different origins. Calibration curves were established between 0.05 (0.1 for omethoate) and 25 µg/mL, and the values obtained for intra‐ and interday precision and accuracy were within the criteria usually accepted for bioanalytical method validation. Lower limits of quantitation were 50 ng/mL for all compounds, except for omethoate (100 ng/mL); the limits of identification of the method were 25 ng/mL for all analytes, except for omethoate, for which 50 ng/mL was obtained. Absolute recovery was determined at three concentration levels, and ranged from 31 to 108%. The proposed method is simple and fast, and can be routinely applied in the determination of these compounds in postmortem whole blood samples within the scope of forensic toxicology. In addition, mass spectrometry has demonstrated to be a powerful and indispensable tool for the unequivocal identification of the analytes, since the acceptance criteria were accomplished even at very low levels, thus allowing obtaining forensically valid and sound results. Copyright © 2010 John Wiley & Sons, Ltd.     

Determination of dimethoate and omethoate in human serum samples. Risk assessment for the operator

A simple and effective analytical procedure has been developed for the determination of dimethoate (DIM) residues and its metabolite, omethoate, in serum samples of pesticide operators. For the selection of the most appropriate method for sample treatment, techniques such as headspace solid phase micro extraction and solid phase extraction and liquid–liquid extraction were applied. The applied method was based on toluene (2?mL) extraction of a 0.5?mL serum sample. In this report, it was observed that DIM concentration level affected the ratio of the area response of DIM and one of its oxygenated metabolite, omethoate. In this context, higher concentrations favoured the predominance of DIM while lower concentrations lead to the formation of omethoate. The method was validated using human serum samples spiked with DIM. Good linearity was obtained in the range of 1–10?ng/mL co-calculating DIM and omethoate. Various concentrations of DIM were mixed with serum and stored up to five days at ?20°C. Recoveries ranged from 72% to 88% at two spiking levels for six replicates. The detection and quantification limit were calculated at 0.12 and 0.36?ng/mL of serum, respectively. Finally the comparison with the Acceptable Operator Exposure Level (AOEL) of DIM revealed that the maximum exposure of the operators reached the 30% of the AOEL for only two cases.     

Aptamer-wrapped gold nanoparticles for the colorimetric detection of omethoate

Organophosphorous pesticide(OP) contamination has serious adverse effects on human health and the environment. Due to the toxicity of OPs and the threat presented by their accidental or intentional release in populated areas, the determination and monitoring of these OPs in food products and environment is of great importance. OPs are present in very small quantities and therefore, methods for their detection need to be highly sensitive and selective. Here, we aimed to develop a simple and selective aptamer-based colorimetric assay for the detection of omethoate, which is one of the commonly used OPs. The principle of the assay is that single-stranded DNA(ss DNA)-wrapped gold nanoparticles(Au NPs) are resistant to salt-induced aggregation. By employing an "artificial antibody" organophosphorous pesticide-binding aptamer(OBA) as the recognition element, aptamer-wrapped Au NPs(Au-apta) show high selectivity towards omethoate, resulting in the disconnection of aptamers from Au NPs and the aggregation of Au NPs. As there is a significant color change from the interparticle plasmon coupling during the aggregation of Au NPs, the established assay showed good linearity between 0.1 and 10 μmol/L, with a low detection limit of 0.1 μmol/L. Other OPs such as profenofos, phorate, and isocarbophos would not interfere with the detection of omethoate despite having similar structures. Thus, the colorimetric method shows potential for use in the detection of omethoate in real soil samples.     

Simultaneous determination of dimethoate and its metabolite omethoate in curry leaf using LC-MS/MS and risk assessment

This study presents the method development, validation, and simultaneous determination of dimethoate and its metabolite omethoate in curry leaf. Samples were extracted following modified quick, easy, cheap, effective, rugged, and safe extraction protocol and analyzed using liquid chromatography-tandem mass spectrometry. The limit of quantification in the matrix was 0.005 μg g⁻¹ for dimethoate and omethoate. Extraction using acetonitrile recorded the average recoveries in the range of 82.25 to 112.97% for dimethoate and 85.57 to 107.22% for omethoate at 0.005, 0.025 and 0.050 μg g⁻¹ fortification levels and relative standard deviation less than 5%. Similarly, the relative standard deviation values for intraday (Repeatability) and interday (Reproducibility) tests were less than 15%. Dissipation kinetics of dimethoate 30% emulsifiable concentrate at 200 and 400 g a.i h⁻¹ recorded initial deposits of 5.20 and 10.05 μg g⁻¹ and 0.33 and 0.48 μg g⁻¹ for dimethoate and omethoate, respectively, and half-life of 3.07 and 3.34 days. The estimated hazard index value found more than one at a day after dimethoate application. It is not safe for consumer health to use curry leaves in the initial days after application.     

基于纳米金的分子印迹传感器检测果蔬中的氧化乐果和乐果

以甲基丙烯酸为功能单体,氧化乐果为印迹分子,构建了一种可用于检测果蔬中氧化乐果和乐果的分子印迹传感器.在金电极上电沉积金纳米粒子,然后将修饰电极浸入10 mL含有氧化乐果和甲基丙烯酸的聚合物溶液中进行9次循环电聚合(-0.3～0.3 V),无水甲醇/乙酸洗涤除去模板分子.循环伏安法和电化学阻抗谱表征传感器,差分脉冲伏安...     

Validation of a method for the determination of multiclass pesticide residues in fruit juices by liquid chromatography/tandem mass spectrometry after extraction by matrix solid-phase dispersion

A multiresidue method was developed and validated for the determination of pesticide residues (omethoate, dimethoate, carbendazim, propoxur, thiabendazole, carbaryl, pirimicarb, azinphos-methyl, methidathion, and iprodione) in fruit juices. The samples were extracted by matrix solid-phase dispersion with diatomaceous earth and analyzed by liquid chromatography/tandem mass spectrometry. The method detection limits were <0.2 ppb for all pesticides; the relative standard deviations for analyses of samples fortified over the range of 2-50 ng/g were <9%, and the recoveries for each pesticide were all between 77 and 102%. The proposed method was used to analyze 21 commercial fruit juices; pesticide residues were found in 71% of the samples.     

Rapid Colorimetric Determination of Procalcitonin Using Magnetic Separation and Enzymatic Catalysis

Human procalcitonin is an early diagnostic biomarker for sepsis and bacterial infections and can be used in distinguishing bacterial infections from viral infections. In this study, a colorimetric sensing platform for the rapid determination of procalcitonin was developed. The approach involves the capture of procalcitonin by immunomagnetic beads, and a detection antibody labeled with horseradish peroxidase to perform sandwich format, where it catalyzes the oxidation of 3,3′,5,5′–tetramethylbenzidine to produce the colorimetric signal. Under the optimal conditions, a detection limit of 0.04?ng/mL (3σ) was obtained within the calibration range 0.1–10?ng/mL. The proposed method was performed in less than 90?min and exhibited good specificity without interferences from other biomarkers including C-reactive protein and human serum albumin. Overall, the proposed method provided a new alternative strategy for procalcitonin detection due to its sensitive, rapid, specific, and simple characteristics. This method is suitable for rapid screening of various biomedical targets.     

人血清中cTnI的化学发光酶免疫分析研究——实验条件的优化

采用高效化学发光试剂3-(2'-螺旋金刚烷)-4-甲氧基-4-(3"-羟基)苯-1,2-二氧杂环丁烷磷酸(AMPPD)作为检测底物, 并将传统的ELISA两步双抗夹心法改为一步法, 得到了高灵敏测定人血清中心肌肌钙蛋白I(cTnI)的化学发光酶免疫分析优化条件. 采用单因素变化法和方阵滴定法得到的最佳实验条件为: 捕获抗体包被浓度为10.0 μg/mL, 以pH=7.0的PBS作为免疫反应缓冲底液, 以含质量分数为1.0%的BSA pH=9.6的碳酸盐溶液缓冲液, 于4 ℃封闭过夜, 生物素-检测抗体(Biotin-IgG2)以及碱性磷酸酶-亲和素(ALP-Avidin)结合物均采用1:2000稀释度, 免疫反应条件为37 ℃, 孵育时间60 min, 以去离子水作为洗涤剂, 以1:100稀释的AMPPD作为发光反应底物, 发光反应时间10 min(37 ℃). 检出限为0.02 ng/mL, 比现行ELISA法灵敏度提高一个数量级; 测定周期约75 min, 比两步法ELISA快得多; 线性范围(0.04~36.20 ng/mL)比ELISA法扩宽了两个数量级; 加标回收率97.5%~102.8%, 对标准样品的测定结果与用ELISA法的测定结果吻合; 重复性好, 3个样品批内变异系数均小于8.5%(n=12).     

气相色谱-火焰光度法测定土壤中有机磷农药残留

建立了气相色谱-火焰光度(GC-FPD)分析土壤中敌敌畏、氧化乐果、二嗪农、乐果、甲基对硫磷、马拉硫磷、对硫磷、水胺硫磷、喹硫磷等9种有机磷农药残留量的方法。样品用丙酮-二氯甲烷(1:3)提取,浓缩、定容后用Hp-5MS(30m×0.25 mm×0.25μm)毛细管柱分离,FPD检测器检测。方法回收率在68.71%～110.39%之间;RSD在5.5%～11%之间;检出限在0.397～1.60μg/mL之间,方法可用于环境土壤样品中有机磷农药残留的测定。     

A colorimetric method for highly sensitive and accurate detection of iodide by finding the critical color in a color change process using silver triangular nanoplates

In this contribution, we demonstrated a novel colorimetric method for highly sensitive and accurate detection of iodide using citrate-stabilized silver triangular nanoplates (silver TNPs). Very lower concentration of iodide can induce an appreciable color change of silver TNPs solution from blue to yellow by fusing of silver TNPs to nanoparticles, as confirmed by UV–vis absorption spectroscopy and transmission electron microscopy (TEM). The principle of this colorimetric assay is not an ordinary colorimetry, but a new colorimetric strategy by finding the critical color in a color change process. With this strategy, 0.1 μM of iodide can be recognized within 30 min by naked-eyes observation, and lower concentration of iodide down to 8.8 nM can be detected using a spectrophotometer. Furthermore, this high sensitive colorimetric assay has good accuracy, stability and reproducibility comparing with other ordinary colorimetry. We believe this new colorimetric method will open up a fresh insight of simple, rapid and reliable detection of iodide and can find its future application in the biochemical analysis or clinical diagnosis.     

血浆中有机磷农药的固相萃取－气相色谱法测定

建立了固相萃取、 GC－ FPD（火焰光度检测器）测定血浆中有机磷农药含量的方法。血样经固相萃取, GC－ FPD分析,杂质干扰少,血中有机磷农药提取回收率在 74％以上, RSD在 7.8％～ 20％。检出限：敌敌畏、乐果为 10 μ g /L;甲拌磷、对硫磷为 5 μ g/L 。经实际中毒病人样品分析,证明该法操作简便、准确可靠,灵敏度高。     

A sensitive colorimetric label-free assay for trypsin and inhibitor screening with gold nanoparticles

Gold nanoparticles (Au-NPs) with negative charges aggregate in the presence of Arg(6) due to electrostatic interactions resulting in the red-shift of the plasmon absorption. But, after incubation of Arg(6) with trypsin the aggregation of Au-NPs can be prohibited. Accordingly, a newly designed-Au-NPs based colorimetric assay method for trypsin activity is established. Trypsin with a concentration as low as 1.6 ng mL(-1) can be assayed with this new colorimetric assay. This colorimetric label-free assay for trypsin can be performed in aqueous solution and both Au-NPs and Arg(6) are easily accessible. Thus, this assay method is useful for screening inhibitors of trypsin.     

气相色谱检测甘蔗中乐果和特丁磷的残留量

甘蔗经加速溶剂萃取仪萃取,应用气相色谱仪定量法检测乐果和特丁磷,建立了定量检测甘蔗中乐果和特丁磷的快速、准确、高灵敏度的方法。经方法学验证,该方法对乐果最低检出限(LOD)为0.01 mg/kg,特丁磷LOD为0.05 mg/kg。乐果和特丁磷在1.0～100.0μg/mL的线性范围内,相关系数r>0.999 9。乐果回收率为91.5%～99.6%,相对标准偏差(RSD)为1.9%～3.2%,特丁磷回收率为81.0%～93.2%,RSD为2.0%～3.5%。结果表明,该检测方法灵敏度高、操作简单、定量准确、测定浓度范围广,是甘蔗样品中乐果和特丁磷含量检测的理想方法。     

Solid-phase microextraction for gas chromatographic/mass spectrometric analysis of dimethoate in human biological samples

A new, simple and rapid procedure for the determination of dimethoate in urine and blood samples was developed using direct immersion solid-phase microextraction and gas chromatography/mass spectrometry. This technique required only 0.1 mL of sample, and ethion was used as internal standard. Two types of coated fibre were compared (100 microm polydimethylsiloxane, and 65 microm Carbowax/divinylbenzene). Other parameters, such as extraction temperature, adsorption and desorption time, salt addition, agitation and pH, were optimized to enhance the sensitivity of the method. Limits of detection (LODs) and quantitation (LOQs) were 50 and 100 ng/mL for urine and 200 and 500 ng/mL for blood, respectively. The method was found to be linear between the LOQ and 40 microg/mL for urine, and between the LOQ and 50 microg/mL for blood, with correlation coefficients ranging from 0.9923-0.9996. Precision (intra- and interday) and accuracy were in conformity with the criteria normally accepted in bioanalytical method validation. The mean absolute recoveries of dimethoate were 1.24 and 0.50% for urine and blood, respectively. Because of its simplicity and the fact that small volumes of sample are used, the described method can be successfully used in the diagnosis of poisoning by this pesticide, namely in those situations where the sample volume is limited, as frequently occurs in forensic toxicology.     

A highly sensitive,dual-signal assay based on rhodamine B covered silver nanoparticles for carbamate pesticides

A highly sensitive sensor for determination of carbamate pesticides based rhodamine B (RB) modified silver nanoparticle (RB-AgNPs) was developed. Compared with the classical method, it combined colorimetric with fluorescence for detecting carbamate pesticides in complex solutions. Carbamate pesticides can inhibit the activity of acetylcholinesterase (AChE), thus preventing the generation of thiocholine. On the other hand, thioncholine can transform the yellow RB-AgNPs solutions gray color and unquenches the fluorescence of RB simultaneously. Once the activity of AChE was inhibited by the pesticide, the color of the RB-AgNPs solution remains yellow and the fluorescence of RB molecules remains quenched. Under optimized experimental conditions, carbaryl was detected in a concentration range from 0.1 ng/L to 8.0 ng/L with a detection limit of 0.023 ng/L (it was detected by fluorescence spectra). This simple method is suitable for determination of carbamate pesticides in complex samples, such as tomato, apple and river water.     

Determination of Dimethoate in Olive Oil by Adsorptive Stripping Square‐Wave Voltammetry

A method for the determination of dimethoate in olive oil by adsorptive stripping square‐wave voltammetry has been developed on the base that this pesticide is hydrolyzed in basic media giving rise to an adsorptive‐reductive peak at ?0.780 V. Extraction of dimethoate from olive oil with ethanol‐water and posterior clean‐up with C18 cartridges is carried out. Response Surface Methodology has been used for the optimization of the extraction procedure. A matrix effect is observed in olive oil extract; therefore the standard addition method must be used. The detection limit is 19.00 ng g^?1 and recoveries for three levels of fortification are ranged from 79.9% to 104.5%.     

Electrochemical ELISA for the detection of cucumber mosaic virus using o-pheneylenediamine as substrate

A sensitive electrochemical enzyme-linked immunosorbent assay (ELISA) for the determination of cucumber mosaic virus (CMV) was proposed in this paper. The activity of labeled enzyme, horseradish peroxidase, was measured with electrochemical methods using o-phenylenediamine as substrate. The enzymatic reaction product is 2,3-diaminophenazine, which can be easily reduced on the dropping mercury electrode with improved sensitivity. Coupled with the plate trapped antigen indirect ELISA format using polyclonal rabbit antibody of CMV, the electrochemical detection was performed for CMV with the detection limit of 0.5 ng ml⁻¹, which is ten times more sensitive than the colorimetric ELISA method. The conditions for enzymatic reaction and immunoassay were carefully optimized.     

Dual-signal immuno-competitive determination of brain natriuretic peptide based on magnetic nanozyme

Brain natriuretic peptide (BNP) has been a disease marker in the diagnosis of heart failure. In this study, gold nanoparticles modified with Hemin (H-AuNPs) as nanozymes were used to oxidize ABST and MB to amplified colorimetric and electrochemical redox signals respectively. BNP was combined with H-AuNPs (BNP-H-AuNPs) through electrostatic adsorption to construct competitive nanozyme probes. Target BNP in the sample compete with BNP-H-AuNPs to bind the antibody-modified magnetic nanoparticles (AntiBNP-MNPs). Due to the excellent catalytic performance of the nanozyme, BNP can be observed well by colorimetric and electrochemical assays. Electrochemical method ensured more accurate detection of BNP with a wide detection range (1–200 pg/mL) and a low detection of limit (0.03 pg/mL). Meanwhile, the results of the experiment can be easily observed with the naked eye by simple colorimetric method with a range from 5 ng/mL to 25 ng/mL and a limit of detection down to 80.3 pg/mL. Thus, based on the important role of H-AuNPs, this assay has exhibited potential value of detection the other small proteins through this competitive nanozyme method.     

A new colorimetric platform for ultrasensitive detection of protein and cancer cells based on the assembly of nucleic acids and proteins

An amplified colorimetric method has been developed for the detection of protein and cancer cells based on the assembly of nucleic acids and proteins for the first time. In this process, the assembly of nucleic acids was triggered by a biotinylated DNA strand after a sandwich immunoreaction. The biotinylated DNA strand and sandwich immunocomplex were connected by streptavidin. Then, the assembly of biotinylated bovine serum albumin (Biotin-BSA) and streptavidin-horseradish peroxidase (SA-HRP) occurred at a node of the assembled products of nucleic acids through the biotin-streptavidin reaction. Under the catalysis of horseradish peroxidase, 3,3′,5,5′-tetramethylbenzidine (TMB) was oxidized by H₂O₂ and the oxidized product was analyzed by its UV–vis absorbance signal and sensitive colorimetric detection. This colorimetric sensor could not only achieve the quantitative determination of protein by UV–vis absorbance but could also be applied for semiquantitative determination by digital visualization. Using alpha-fetoprotein (AFP) as the model target, this proposed colorimetric method showed a wide linear range from 5 pg/mL to 1 ng/mL with a detection limit of 1.95 pg/mL by the instrument, and even 5 pg/mL target protein could be distinguished simply by the naked eye. This approach was then expanded to detect cancer cells based on the recognition of folic acid receptors that were over-expressed on the cancer cells by folic acid-tethered DNA. More importantly, this strategy can be further used as a universal colorimetric method for the determination of viruses or other proteins by changing the corresponding antibodies.     

Target recycling amplification for label-free and sensitive colorimetric detection of adenosine triphosphate based on un-modified aptamers and DNAzymes

Based on target recycling amplification, the development of a new label-free, simple and sensitive colorimetric detection method for ATP by using un-modified aptamers and DNAzymes is described. The association of the model target molecules (ATP) with the corresponding aptamers of the dsDNA probes leads to the release of the G-quadruplex sequences. The ATP-bound aptamers can be further degraded by Exonuclease III to release ATP, which can again bind the aptamers of the dsDNA probes to initiate the target recycling amplification process. Due to this target recycling amplification, the amount of the released G-quadruplex sequences is significantly enhanced. Subsequently, these G-quadruplex sequences bind hemin to form numerous peroxidase mimicking DNAzymes, which cause substantially intensified color change of the probe solution for highly sensitive colorimetric detection of ATP down to the sub-nanomolar (0.33 nM) level. Our method is highly selective toward ATP against other control molecules and can be performed in one single homogeneous solution, which makes our sensing approach hold great potential for sensitive colorimetric detection of other small molecules and proteins.