The first validated HPLC method for separation and quantification of imiprothrin and deltamethrin in insecticide spray formulation

This work is concerned with novel, accurate and precise determination of two common insecticides, imiprothrin and deltamethrin, using HPLC. The chromatographic conditions were optimised for the best separation. The column was Intersil ODS (4.6 x 250 mm with 5 µm particle size). The mobile phase consists of a mixture of acetonitrile and water (90:10, v/v) at a flow rate of 1.2 mL/min. UV detection was accomplished at 230 nm using chlorpyriphos as an internal standard. The method was validated according to International Conference on Harmonization (ICH) guidelines and was found to be linear over the range 7.5–45 µg/mL for imiprothrin and 5–30 µg/mL for deltamethrin. The method was applied to the assay of both insecticides in the combined spray formulation from the Egyptian market. Statistical comparison between the proposed and the reported methods showed no significant difference. The method can be applied for simultaneous determination of both compounds in different market products with high specificity and in quality control laboratories for insecticide residue monitoring.     

Determination of Pyrethroid Residues in Pork Muscle by Immunoaffinity Cleanup and GC-ECD

A method was developed to determine six pyrethroids (tau-fluvalinate, fenpropathrin, λ-cyhalothrin, cyfluthrin, α-cypermethrin and deltamethrin) in pork muscle by immunoaffinity column cleanup and gas chromatography-electron capture detection. Spiked pork muscle samples at 5, 20, 50 μg kg^?1 were extracted with petroleum spirit-diethyl ether (1:1, v/v). Fat was eliminated by liquid–liquid partition between acetonitrile and petroleum spirit. An immunoaffinity column (IAC) was used for further cleanup. The IAC column was prepared by coupling the polyclonal antibodies to the protein A sepharose gel and the resulting affinity gel columns were sufficiently stable for multiple reuse. Target compounds were adsorbed at pH 7.4 and after extensive washing, eluted with 3 mL methanol. Recoveries of the six pyrethroids were typically >70%. The detection limit was 2 μg kg^?1 for λ-cyhalothrin and α-cypermethrin and 5 μg kg^?1 for cyfluthrin, deltamethrin, fenpropathrin and tau-fluvalinate. Repeat analyses of pork muscle samples showed good repeatability. The method was applied to detect residues in meat samples.     

Aalysis of the fatty acid composition of the lipid classes in human blood serum under normal diet and when supplemented with fish oil

Total lipids have been extracted from human serum with chloroform–methanol 2:1 (v/v) and separated into individual classes by TLC. After transesterification the fatty acid methyl esters were analyzed by capillary gas chromatography on an FFAP column. The quantitation of ω-3 fatty acids has been performed using internal and external standards. Internal lipid standards for each lipid class were carried throughout the entire analytical procedure. Under normal diet eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are incorporated into the lipid classes to different extents: cholesterol esters; EPA, 6.5 ± 1.9 γ/ml serum; DHA, 4.3 ± 1.9 μg/ml: phospholipids; EPA, 5.9 ± 2.7 μg/ml; DHA, 31.8 ± 8.1 μg/ml. Fish oil supplementation leads to a 4 to 6-fold rise in EPA and to an approximately 2-fold rise in DHA.     

UPLC-MS/MS法同时检测番茄与黄瓜中的24种杀虫剂

建立了超高效液相色谱-串联质谱检测番茄和黄瓜中24种杀虫剂残留的分析方法。样品用乙腈提取,经QuEChERS方法净化,高速离心,过滤膜后以超高效液相色谱-串联质谱(UPLC-MS/MS)检测。结果表明:在0.1~50μg/L质量浓度范围内,24种杀虫剂线性良好,相关系数(r2)大于0.99;在0.002、0.01、0.1、1.0 mg/kg 4个加标水平下,24种杀虫剂在番茄和黄瓜中的平均回收率为70.3%~110%,相对标准偏差(RSD)小于15%;方法的定量下限(LOQ)为0.05~5μg/kg,检出限(LOD)为0.01~1.82μg/kg。方法的定量下限和检出限均符合检测要求。该方法具有高灵敏度、高准确度和高效率的优点,适用于番茄和黄瓜中24种杀虫剂的同时检测。     

Detection of catecholamine metabolites in urine based on ultra-high-performance liquid chromatography–tandem mass spectrometry

The excretion of neurotransmitter metabolites in normal individuals is of great significance for health monitoring. A rapid quantitative method was developed with ultra-performance liquid chromatography–tandem mass spectrometry. The method was further applied to determine catecholamine metabolites vanilymandelic acid (VMA), methoxy hydroxyphenyl glycol (MHPG), dihydroxy-phenyl acetic acid (DOPAC), and homovanillic acid (HVA) in the urine. The urine was collected from six healthy volunteers (20–22 years old) for 10 consecutive days. It was precolumn derivatized with dansyl chloride. Subsequently, the sample was analyzed using triple quadrupole mass spectrometry with an electrospray ion in positive and multireaction monitoring modes. The method was sensitive and repeatable with the recoveries 92.7–104.30%, limits of detection (LODs) 0.01–0.05 μg/mL, and coefficients no less than 0.9938. The excretion content of four target compounds in random urine samples was 0.20 ± 0.086 μg/mL (MHPG), 1.27 ± 1.24 μg/mL (VMA), 3.29 ± 1.36 μg/mL (HVA), and 1.13 ± 1.07 μg/mL (DOPAC). In the urine, the content of VMA, the metabolite of norepinephrine and adrenaline, was more than MHPG, and the content of HVA, the metabolite of dopamine, was more than DOPAC. This paper detected the levels of catecholamine metabolites and summarized the characteristics of excretion using random urine samples, which could provide valuable information for clinical practice.     

Development and validation of a multiresidue method for the simultaneous determination of organophosphorus insecticides and their toxic metabolites in sugarcane juice and refined sugar by gas chromatography with flame photometric detection

A multiresidue method has been developed and validated for the simultaneous determination of organophosphorus insecticides and their toxic metabolites in sugarcane juice and refined sugar by gas chromatography with flame photometric detection. Limits of quantification of the method varied between 0.007 and 0.01 μg/g. Ethyl acetate based extraction followed by dispersive solid‐phase extraction cleanup with primary secondary amine yielded internationally acceptable recoveries of acephate, chlorpyrifos, dichlorvos, monocrotophos, malathion, malaoxon, phorate, phorate‐sulfoxide, phorate‐oxon, phorate‐sulfone, and quinalphos from selected matrices. The recoveries of target analytes from cane juice were 75.55 ± 0.5–102.57 ± 4.2, 77.45 ± 4.7–103.33 ± 3.3, and 80.55 ± 6.6–105.82 ± 9.8% at 0.01, 0.02, and 0.1 μg/g levels of fortification, respectively. The recoveries from cane sugar were 73.24 ± 3.5–104.47 ± 1.9, 75.23 ± 1.5–116.10 ± 3.7, and 70.75 ± 5.7–110.15 ± 2.7%, respectively at 0.01, 0.02, and 0.1 μg/g levels of fortification. Matrix effect and measurement uncertainty were within the permissible limit (less than 20%) as prescribed for pesticide residue analysis.     

A new spray reagent for the detection of synthetic pyrethroids containing a nitrile group on thin-layer plates

This paper describes a new spray reagent for selective detection of synthetic pyrethroids containing -cyano group i.e. lambda-cyhalothrin, deltamethrin, cyfluthrin and fluvalinate by thin layer chromatography. These synthetic pyrethroids on alkaline hydrolysis, yield a cynohydrin derivative which degrades to give HCN and a corresponding aldehyde. This liberated HCN reduces 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyl tetrazolium chloride (INT) to formazan, a pink product in the presence of phenazonium methosulfate (PMS). The pink colour formed remain stable for more than 24 h. Other group of insecticides like organophosphorus, organochlorine and carbamate do not interfere in the determination. Pyrethroid insecticides not containing hydrolysable nitrile group also do not interfere. The limit of detection is from 0.5 to 1 μg.     

Effect of different temperatures on the properties of pyrolysis products of Parthenium hysterophorus

This research encompasses the use of noxious weed Parthenium hysterophorus as feedstock for pyrolysis carried out at varying temperatures of 300, 450 and 600°C. Temperature significantly affected the yield and properties of the pyrolysis products including char, syngas and bio-oil. Biochar yield decreased from 61% to 37% from 300 °C to 600 °C, whereas yield of gas and oil increased with increasing temperature. The pyrolysis products were physico-chemically characterized. In biochar, pH, conductivity, fixed carbon, ash content, bulk density and specific surface area of the biochar increased whereas cation exchange capacity, calorific value, volatile matter, hydrogen, nitrogen and oxygen content decreased with increasing temperature. Thermogravimetric analysis showed that the biochar prepared at higher temperature was more stable. Gas Chromatography-Mass Spectrometry analysis of biochar indicated the presence of alkanes, alkenes, nitriles, fatty acids, esters, amides and aromatic compounds. Number of compounds decreased with increasing temperature, but aromatic compounds increased with increasing temperature. Scanning electron micrographs of biochar prepared at different temperatures indicated micropore formation at lower temperature while increase in the size of pores and disorganization of vessels occurred at increasing temperature. The chemical composition was found to be richer at lower pyrolysis temperature. GC–MS analysis of the bio-oil indicated the presence of phenols, ketones, acids, alkanes, alkenes, nitrogenated compounds, heterocyclics and benzene derivatives.     

Thin-layer chromatographic detection of monocrotophos in biological materials

An organophosphorus insecticide monocrotophos is increasingly being used in agriculture to control insects on a wide range of crops. Its ready access has resulted in misuse in many instances of homicidal and suicidal poisoning cases. This paper describes a chromogenic spray reagent for the detection of monocrotophos in biological materials by thin-layer chromatography. Monocrotophos on alkaline hydrolysis yields N-methylacetoacetamide which in turn reacts with diazotized sulphanilamide or sulphanilic acid to give a red colour. Other organophosphorus insecticides do not give a coloured spot. Moreover, organochlorine and synthetic pyrethroid insecticides and constituents of viscera (amino acids, peptides, proteins etc.) which are generally co-extracted with the insecticides, do not interfere. However, phenolic compounds and hydrolysed product of carbamate insecticides, may interfere and are differentiated from monocrotophos by R_F values. The limit of detection is ca 1 μg.     

PDMS extraction bars for the determination of volatile aromatic hydrocarbons in water and wastewater

In this study, the preparation and application of extraction bars of PDMS were investigated to preconcentrate and determine benzene, toluene, ethylbenzene, and xylene in water and wastewater by means of HPLC with fluorescence detection. Aliquot samples from hospital wastewater were used as the model effluent. The independent variables for the sorptive extraction were as follows: ionic strength (added amounts of NaCl); pH; temperature and time of absorption; temperature and time of desorption. Under optimized conditions, by using a factorial design, the suspended extraction bars could allow the determination of benzene, toluene, ethylbenzene, and xylene (1.20 ± 0.05 μg/L; 10.40 ± 0.02 μg/L; 1.80 ± 0.04 μg/L; 15.9 ± 0.04 μg/L, respectively) in hospital effluent (fortified samples), by recoveries of 71.9 ± 4.9 to 74.8 ± 5.6%. This procedure represents an innovation that eliminates the time‐consuming stage of vacuum microfiltration, and allows the determination of volatile organic compounds by HPLC. As far as we know, this procedure is original and represents an important contribution to the field.     

Profiling of esterified fatty acids as biomarkers in the blood of dengue fever patients using a microliter‐scale extraction followed by gas chromatography and mass spectrometry

An improved gas chromatography with mass spectrometry procedure was developed to highlight the esterified fatty acids in 100 μL blood of dengue fever patients in the early febrile phase versus healthy volunteers. 24 adult patients and 24 healthy volunteers were included in this study. The recoveries of targeted esterified fatty acids content were in the range of 92.10–101.00% using methanol/dichloromethane (2:1, v/v) as the extraction solvent. An efficient chromatographic separation of targeted 17 esterified fatty acid methyl esters was obtained. The limits of detection and quantification were within the range of 16–131 and 53–430 ng/mL, respectively. The relative standard deviation of intraday and interday precision values ranged from 0.4 to 5.0%. The statistical data treatment showed a significant decrease of the content of four saturated fatty acids, C14:0, C15:0, C16:0, and C18:0 (P value < 0.05), and also showed a decrease of the content of eight unsaturated fatty acids, C16:1, C18:3n6, C18:2n6, C18:1n9, C20:3n3, C20:4n6, C20:2, and C22:6n3 (P value < 0.05) in dengue fever patients. Moreover, the amount of three omega‐6 fatty acids including C18:3n6, C18:2n6, and C20:4n6 was dramatically decreased in the blood of dengue fever patients to a limit of 50 ± 10%.     

An expedient reverse‐phase high‐performance chromatography (RP‐HPLC) based method for high‐throughput analysis of deferoxamine and ferrioxamine in urine

The present study was planned to optimize and validate an expedient reverse‐phase high chromatography (RP‐HPLC) based protocol for the analysis of deferoxamine (DFO) and ferrioxamine (FO) in urinary execration of patients suffering β ‐thalassemia major. The optimized RP‐HPLC method was found to be linear over the wide range of DFO and FO concentration (1–90 μg/mL) with appreciable recovery rates (79.64–97.30%) of quality controls at improved detection and quantitation limits and acceptable inter and intraday variability. Real‐time analysis of DFO and FO in the urine of thalassemic patients (male and female) at different intervals of Desferal®(Novartis Pharmaceuticals Corporation) injection revealed DFO and FO excretion at significantly (p < 0) different rates. The maximum concentrations of DFO (76.7 ± 3.06 μg/mL) and FO (74.2 ± 3.25 μg/mL) were found in urine samples, collected after 6 h of drug infusion while the minimum levels of DFO (1.10 ± 0.12 μg/mL) and FO (2.97 ± 0.13 μg/mL) were excreted by patients after 24 h. The present paper offers balanced conditions for an expedient, reliable and quick determination of DFO and FO in urine samples.     

The determination of low lead levels in the bone of lead-depleted mice by graphite furnace atomic absorption spectrometry

Low lead levels in the femurs of mice fed with a lead-depleted diet have been determined by use of electrothermal atomic absorption spectrometry with Zeeman-effect background correction. The method is based on the use of Mg(NO₃)₂/Pd as matrix modifier which enables significant reduction of the spectral interferences prevalent if chemical modifiers based on NH₄H₂PO₄ with either Ca or Mg are used for samples rich in Ca₃(PO₄)₂ matrix. The method was developed and validated by use of the NIST standard reference material 1486 bone. Bones were decomposed in a pressurized microwave-heated system using 70% nitric acid. Forty-three mice femurs, with a mass of 74.62 ± 12.54 mg, were dissolved in concentrated nitric acid. The lead results found in SRM 1486 (1.25 ± 0.15 μg g^–1, n = 9) were in good agreement with the certificate (1.335 ± 0.014 μg g^–1). Recoveries of 200 ng lead added to the SRM before or after digestion were 99.0 ± 1.4% and 98.5 ± 1.6%, respectively. The lead detection limit in bone samples is 0.06 μg g^–1 dry mass. This method is, therefore, suitable for the determination of very low lead levels (0.06–0.20 μg Pb kg^–1 bone) in the femurs of mice fed a diet with lead level of < 20μg kg^–1.     

Determination of lead in whole blood with a simple flow-injection system and computerized stripping potentiometry

An automated (24 samples/hour) procedure is described for the determination of lead (0–1000 μg l^?1) in human blood based on flow-injection stripping potentiometry. The samples are diluted 20-fold with 0.5 M hydrochloric acid containing 100 mg l^?1 mercury and 40 μg l^?1 cadmium (II), and a 1.1 ml aliquot is injected into the flow system. With a mercury-coated carbon fibre as working electrode, lead (II) is determined by using cadmium (II) as internal standard and a calibration graph prepared from bovine blood. Analyses of two human blood reference samples yielded results of 335±37 and 691±24 μg l^?1 lead, the certified values being 332 and 663 μg l^?1, respectively.     

Optimization of programmed‐temperature vaporization injection preparative capillary GC for compound specific radiocarbon analysis

Preparative capillary GC (PCGC) is a powerful tool for the separation and purification of compounds from any complex matrix, which can be used for compound‐specific radiocarbon analysis. However, the effect of PCGC parameters on the trapping efficiency is not well understood. Here, we present a comprehensive study on the optimization of parameters based on 11 reference compounds with different physicochemical properties. Under the optimum conditions, the trapping efficiencies of these 11 compounds (including high‐boiling‐point n‐hentriacontane and methyl lignocerate) are about 80% (60–89%). The isolation of target compounds from standard solutions, plant and soil samples demonstrates that our optimized method is applicable for different classes of compounds including n‐alkanes, fatty acid esters, long‐chain fatty alcohol esters, polycyclic aromatic hydrocarbons (PAHs) and steranes. By injecting 25 μL in large volume injection mode, over 100 μg, high purity (>90%) target compounds are harvested within 24 h. The recovery ranges of two real samples are about 70% (59.9–83.8%) and about 83% (77.2–88.5%), respectively. Compared to previous studies, our study makes significant improvement in the recovery of PCGC, which is important for its wide application in biogeochemistry, environmental sciences, and archaeology.     

果蔬中8种苯甲酰脲类农药残留量的液相色谱-串联质谱法测定

建立了果汁蔬菜中8种苯甲酰脲类(杀虫脲、氟苯脲、氟虫脲、氟啶脲、除虫脲、氟铃脲、灭幼脲、氟丙氧脲)农药残留量的液相色谱-电喷雾串联质谱(LC-ESI MS/MS)测定方法。样品用乙腈提取后无需净化,经盐析过滤并以水稀释(1∶1)后,经Waters Atlantis(d C18色谱柱分离,5 mmol/L乙酸铵水溶液和乙腈梯度洗脱,以电喷雾电离串联质谱在负离子多反应监测(MRM)模式下进行测定并确证,外标法定量。8种苯甲酰脲类农药在1.0~100μg/L范围内线性良好,相关系数为0.990 0~0.999 9。对8种农药在毛豆基质中3个添加水平下的回收率进行测定,平均回收率为92%~110%,相对标准偏差为5.5%~12%。方法的检出限(S/N=3)为0.04~0.42μg/kg,定量下限(S/N=10)为0.2~1.5μg/kg。     

Determination of triallate and its metabolite 2,3,3-trichloro-prop-2-en-sulfonic acid in soil and water samples

A method based on solid phase extraction was developed for the determination of the herbicide triallate and its metabolite 2,3,3-trichloro-prop-2-en-sulfonic acid (TCPSA). Soil samples were extracted with methanol and diluted with water to yield a methanol/water ratio of 1?:?4. Triallate was adsorbed on C₁₈ cartridges while TCPSA was enriched on quaternary amine anion exchange resins. Cartridges were eluted with methanol/ethyl acetate and methanol/sulfuric acid mixture, respectively. TCPSA methyl ester was formed using trimethyl orthoformate and subsequently analyzed by GC/ECD. Determination limits of both target compounds were 5 μg/kg soil with recoveries of 100 ± 12% for triallate and 57 ± 5% for TCPSA. In water analysis, determination limits were 0.05 μg/L with recoveries of 84 ± 14% for triallate and 100 ± 22% for TCPSA. In laboratory batch experiments, concentration of triallate decreased from 2690 to 1550 μg/kg soil within 59 days. 14 days after triallate application, TCPSA was determined to be 14 μg/kg which increased to 98 μg/kg soil at the end of the incubation period. Soil/water distribution coefficients in loamy sand soil were 102 for triallate and 0.02 for TCPSA which indicated a higher leaching tendency of the polar metabolite.     

Development of a colourimetric pH assay for the quantification of pyrethroids based on glutathione-S-transferase

Recombinant glutathione-S-transferases (GSTs) can be used as analytical tools for the development of simple insecticide quantification assays. This assay explores the ability of pyrethroids to promote inhibition of the GST-catalysing 1-chloro-2,4-dinitrobenzene (CDNB)/glutathione (GSH) conjugation reaction. The sensing scheme is based on the pH change occurring in a weak buffer system by the GST reaction, which is measured using a spectrophotometer and the dye indicator bromothymol blue (616 nm). Practical use depends on the recognition affinity of the GST for insecticides, inhibition kinetics, enzyme stability and compatibility with the detection assay. In this study we compared the recombinant GSTs AgGSTD1-6 and AdGSTD1-1 from the mosquito vectors Anopheles gambiae and Anopheles dirus, respectively, with high affinity for pyrethroids, for their suitability for detecting pyrethroids in vector disease control programmes. The results showed that AgGSTD1-6 was the most suitable enzyme with the best structural stability at higher temperatures (T _m = 57°C) and pH optima in the alkaline range (pH 7.7). Using the AgGSTD1-6, we subsequently developed a pH - change colourimetric assay for detecting pyrethroids. Linear calibration curves were obtained for deltamethrin (R ² = 0.99) with useful concentration ranges of 0–50 µg mL^?1. The effect of temperature in the range 25–40°C on the pyrethroid quantification assay was negligible. The assay was validated with extracts from insecticide sprayed surfaces and found to be reproducible and reliable compared with the standard reverse-phase high performance liquid chromatography (Rp-HPLC) method. The potential of the assay for monitoring insecticide residues in the frame of insecticide based malaria control interventions is discussed.     

Application of the QuEChERS method for the analysis of pyrethrins and pyrethroids in fish tissues

The application of the quick easy cheap effective rugged and safe (QuEChERS) method has generally been used in the preparation of produce samples (e.g., lettuce and oranges) for pesticide analysis. In the present study, the QuEChERS method was successfully applied to the determination of the natural pyrethrins (cinerin I and II, jasmolin I and II, and pyrethrin I and II), as well as two pyrethroid insecticides, cypermethrin and deltamethrin, in fin and non-fin fish products. Analysis of these compounds was performed using gas chromatography–mass spectrometry. Although cypermethrin is not and has not been registered for pest control use in aquaculture operations in Canada, cypermethrin was detected in domestically produced salmon. Cypermethrin was detected in seven of the 18 Canadian farmed salmon samples (39%), although it was not detected in any wild domestic salmon (n = 3). Cypermethrin concentrations ranged from 0.3 to 6.5 ng/g in the positive samples. It was not, however, observed in any imported fish product or any other domestically produced fish product.     

Metabolic Profiling of Aliphatic,hydroxy, and Methyl-Branched Fatty Acids in Human Plasma by Gas Chromatography–Mass Spectrometry

An efficient method for the simultaneous profiling analysis of 44 fatty acids including 24 aliphatic, 12 hydroxyl, and eight methyl-branched fatty acids as tert-butyldimethylsilyl (TBDMS) derivatives was developed by gas chromatography–mass spectrometry. In this study, new mass spectral databases of isolauric, 11-methyllauric, isomyristic, isopentadecylic, isopalmitic, isostearic, 17-methylstearic, and 19-methylarachidic acids were constructed as TBDMS derivatives. Under the optimal conditions, linearity in the range of 0.1–10.0?µg/mL (24 aliphatic fatty acids) and 0.01–1.0?µg/mL (eight methyl-branched and 12 hydroxy fatty acids) showed good correlation coefficients (r?≥?0.997). The repeatability showed relative standard deviation of less than 11.2% and accuracy (percent relative error) varied from ?11.0 to 7.8 for the 44 fatty acids studied. The recoveries ranged from 61.7 to 90.1% with good repeatability. When applied to human plasma sample, 18 aliphatic, three 2-hydroxy, three 3-hydroxy, and five methyl-branched fatty acids were positively identified and quantified. Therefore, the present method will be useful for profiling analysis of various fatty acids in biological samples including plasma.