Determination of total arsenic by photo-decomposition of organoarsenic compounds and hydride generation electrothermal atomic absorption spectrometry

A method was developed for the determination of total arsenic concentration in less than ng/ml level by decomposition of organoarsenicals using photo -oxidation combined with in situ trapping of arsenic hydride on a palladium coated graphite tube with subsequent atomization and detection by AAS. The organoarsenicals include monomethylarsenic, dimethylarsenic, arsenobetaine, arsenocholine, o -aminobenzenarsenate and p -aminobenzenarsenate. The method is simple and sensitive. Detection limit was obtained from different arsenic compounds over the range from 0. 058 to 0.063 ng/ml as As (based on three times of the standard deviation of 10 blank measurements) and the relative standard deviations for ten replicate measurements were from 2.0 to 3.8%. The calibration curves of arsenic compounds including inorganic and organic arsenicals were linear over the range from 0.1 to 3.0 ng/ml as As. The recommended method has been applied to the determination of total arsenic in tap and lake water samples at ng/ml leve     

Determination of alkali-labile phosphoprotein phosphorus from fish plasma using the Tb^3＋-tiron complex as a fluorescence probe

A sensitive method based on the fluorescence quenching effect of the Tb^3＋-Tiron complex is proposed for the determination of alkali-labile phosphoprotein phosphorus （ALP） released from fish plasma. The detection limit was 5.4 ng/ml （S/N=2）, and the relative standard deviation of the quenching effect （6 replicates） was 4.6%. The results obtained by the proposed method were in good agreement with those obtained by the colorimetric assay. The advantages of the present method are its relatively simple detection procedure, the lack of toxic organic solvents, and high sensitivity.     

Validation of a HRGC–ECNI/LRMS method to monitor short-chain chlorinated paraffins in human plasma

Short-chain chlorinated paraffins(SCCPs) are produced in high volume and have the high potential to pose a threat to human health. However, little information is available for SCCP contamination in human blood/plasma/serum, mainly due to the difficulty of sample preparation and quantitative analysis. A method using high resolution gas chromatography coupled with electron capture negative ionization low resolution mass spectrometry(HRGC–ECNI/LRMS) was developed and validated to measure SCCPs in human plasma. The pretreatment process included protein denaturation and lipid elimination, liquid–liquid extraction with a mixture of n-hexane/dichloromethane(1:1, V/V), and cleanup on a multilayer silica column. The blank controls, including procedural blank, vacuum blood collection tube blank, and instrumental blank, were the most pivotal points for the reliable analysis of SCCPs. The average value of procedural blanks was 9.0 ng/g; and the method detection limit(MDL), calculated as the sum of the average procedural blank value and 3 times of the standard deviation of the procedural blanks, was 12.6 ng/g plasma. The validated method was applied to measure the concentrations of the total SCCPs(∑ SCCPs) in50 plasma samples from a general population. The measured plasma concentrations of ∑SCCPs ranged from MDL to 203 ng/g wet weight(ww), with an average value of 32.0 ng/g ww.The relative abundance profiles of SCCPs in plasma samples were dominated by C10- and C11-CP congener groups centered on Cl6–7. The developed method can be used for the comprehensive and large-scale investigation of SCCP levels in human plasma.     

Quantitative determination of AI-2 quorum-sensing signal of bacteria using high performance liquid chromatography–tandem mass spectrometry

Autoinducer 2(AI-2), an important bioactive by-product of the Lux S-catalyzed S-ribosylhomocysteine cleavage reaction in the activated-methyl-cycle, has been suggested to serve as a universal intra- and inter-species signaling molecule. The development of reliable and sensitive methods for quantitative determination of AI-2 is highly desired.However, the chemical properties of AI-2 cause difficulty in its quantitative analysis.Herein, we report a high performance liquid chromatography-tandem mass spectrometric method that enables reproducible and sensitive measurement of AI-2 concentrations in complex matrixes. 4,5-Dimethylbenzene-1,2-diamine(DMBDM), an easy-to-obtain commercial reagent, was used for the derivatization treatment. The assay was linear in the concentration range of 1.0–1000 ng/m L(R~2= 0.999) and had a lower limit of quantification of0.58 ng/m L. The method exhibited several advantages, e.g., high selectivity, wide linear response range, and good sensitivity. Furthermore, the effectiveness of the method was further validated through measuring AI-2 concentrations in the cell-free culture supernatant from Escherichia coli wild type.     

Application of multiwalled carbon nanotubes treated by potassium permanganate for determination of trace cadmium prior to flame atomic absorption spectrometry

In this study we investigated the enrichment ability of oxidized multiwalled carbon nanotubes (MWCNTs) and established a new method for the determination of trace cadmium in environment with flame atomic absorption spectrometry.The MWCNTs were oxidized by potassium permanganate under appropriate conditions before use as preconcentration packing.Parameters influencing the recoveries of target analytes were optimized.Under optimal conditions,the target analyte exhibited a good linearity (R~2=0.9992) over the concentration range 0.5-50 ng/ml.The detection limit and precision of the proposed method were 0.15 ng/ml and 2.06%, respectively.The proposed method was applied to the determination of cadmium in real-world environmental samples and the recoveries were in the range of 91.3%-108.0%.All these experimental results indicated that this new procedure could be applied to the determination of trace cadmium in environmental waters.     

Rapid detection of multiple class pharmaceuticals in both municipal wastewater and sludge with ultra high performance liquid chromatography tandem mass spectrometry

This work described the development, optimization and validation of an analytical method for rapid detection of multiple-class pharmaceuticals in both municipal wastewater and sludge samples based on ultrasonic solvent extraction, solid-phase extraction, and ultra high performance liquid chromatography-tandem mass spectrometry quantification. The results indicated that the developed method could effectively extract all the target pharmaceuticals （25） in a single process and analyze them within 24 min. The recoveries of the target pharmaceuticals were in the range of 69%-131% for wastewater and 54%-130% for sludge at different spiked concentration levels. The method quantification limits in wastewater and sludge ranged from 0.02 to 0.73 ng/L and from 0.02 to 1.00μg/kg, respectively. Subsequently, this method was validated and applied for residual pharma- ceutical analysis in a wastewater treatment plant located in Beijing, China. All the target pharmaceuticals were detected in the influent samples with concentrations varying from 0.09 ng/L （tiamulin） to 15.24 μg/L （caffeine）; meanwhile, up to 23 pharmaceuticals were detected in sludge samples with concentrations varying from 60 ng/kg （sulfamethizole） to 8.55 mg/kg （ofloxacin）. The developed method demonstrated its selectivity, sensitivity, and reliability for detecting multiple-class pharmaceuticals in complex matrices such as municipal wastewater and sludge.     

Determination of paraquat in water samples using a sensitive fluorescent probe titration method

Paraquat (PQ), a nonselective herbicide, is non-fluorescent in aqueous solutions. Thus, its determination through direct fluorescent methods is not feasible. The supramolecular inclusion interaction of PQ with cucurbit[7]uril was studied by a fluorescent probe titration method. Significant quenching of the fluorescence intensity of the cucurbit[7]uril-coptisine fluorescent probe was observed with the addition of PQ. A new fluorescent probe titration method with high selectivity and sensitivity at the ng/mL level was developed to determine PQ in aqueous solutions with good precision and accuracy based on the significant quenching of the supramolecular complex fluorescence intensity. The proposed method was successfully used in the determination of PQ in lake water, tap water, well water, and ditch water in an agricultural area, with recoveries of 96.73% to 105.77%. The fluorescence quenching values (ΔF) showed a good linear relationship with PQ concentrations from 1.0×10^-8 to 1.2× 10^-5 mol/L with a detection limit of 3.35×10^-9 mol/L. In addition, the interaction models of the supramolecular complexes formed between the host and the guest were established using theoretical calculations. The interaction mechanism between the cucurbit[7]uril and PQ was confirmed by ¹H NMR spectroscopy.     

Application of closed-vessel microwave digestion method for the determination of multi-elements in environmental samples by sequential ICP-AES

A closed-vessel microwave digestion method is described for the rapid dissolution of environmental samples such as foods, soils and sediments. Depending on the sample type, 0.1-0.2 g sample was decomposed with HNO3/H2O2 or HNO3 / H2O2/HF acid mixture in a PTFE digestion vessel by using microwave heating for 2-3 min at 500W of microwave power. The solution, or to which 0.5 g of boric acid was added, was diluted to 25-50 ml and directly determined by sequential ICP-AES. The accuracy of the procedure was validated by the analysis of six standard reference materials for 10 elements. Ail results were in a good agreements with the certified values.     

Multiresidue determination and potential risks of emerging pesticides in aquatic products from Northeast China by LC–MS/MS

A simple method for determining 33 pesticides with a wide polarity range(log Kow0.6-4.5) in aquatic products was developed based on LC–MS/MS. The target analytes included three types of widely used pesticides: insecticides, fungicides and herbicides. Based on the optimization of ultrasonic assisted extraction and GPC clean-up procedures, the matrix effect, extraction recoveries and LOD were improved distinctively. LOQ of this method was below 0.5 ng/g for all pesticides, which is superior to values in the literature, and the matrix effect was reduced effectively(-14.7% to 7.5%). The method was successfully applied to investigate the pesticide residue levels of twenty-five samples including seven common kinds of fishes from Northeast China. The results showed that all targeted pesticides were present in the fish samples; however, their levels were low, except for atrazine, linuron,ethoprophos, tetrachlorvinphos, acetochlor and fenthion. Atrazine and linuron caught our attention because the concentrations of atrazine in fish samples from Liaoning province were in the range of 0.5-8 ng/g(w/w) with mean concentration of 2.3 ng/g, which were far above those of other pesticides. The levels of linuron were in the range of 0.6-6 ng/g(mean concentration 2.8 ng/g), which were the highest among all targeted pesticides in the Inner Mongolia. This is the first systematic investigation on the characteristics and levels of these pesticides in aquatic products from northeast China. Considering their toxicity and bioaccumulation, the potential risk of atrazine and linuron from consuming aquatic products should be paid more attention.     

Quantitative extraction of methylgermanium species at trace levels and determination by on-column capillary gas chromatography with flame photometric detector

A solvent extraction procedure for the quantitativeextraction of trace levels of methylgermanium species as theirchloride complex has been developed and the extract was determinedby an on-column capillary gas chromatography with a lab-modifiedflame phorometric detector(FPD) using quartz surface-inducedgermanium emission after pentylation with Grignard reaction. Theextracted percentages for TMGe, DMGe and MMGe in a 100-ml 9mol/LHCl aqueous solution by a single extraction with 1 ml hexane are86.6%, 87.4% and 96.2%, respectively. The precision for overallprocedure range from 3.9% to 7.5%. The extraction was found to beindependent of the initial concentration of methylgermanium speciesin the aqueous phase, which typically varied from 0.1 to 10 μg. This method is suitable for most types of environmental samples and, are superior to all hydride generation coupled spectrometric andspectrophotometric methods in terms of selectivity and toleranceability to interference.     

Sensitized effect of β-cyclodextrin on the fluorescence in the determination of carbaryl

Based on the significant enhancement of fluorescence intensity of carbaryl in inclusion complex, a spetrofluorimetric method with high sensitivity was developed for the determination of carbaryl in aqueous solution. Under the optimum conditions, the complex had excitation and emission maxima at 278 nm and 332 nm, respectively. The linear range of the method was 7.0 ng/ml-1500 ng/ml with a detection limit of 1.2 ng/ml. The proposed method was successfully used to determine quantitatively of carbaryl in cottonseeds.     

痕量硒的示波极谱测定

在０．６０ｍｏｌ／Ｌ醋酸－０．００２０ｍｏｌ／Ｌ对氨基苯磺酸介质中,Ｓｅ（Ⅵ）－对氨基苯磺酸配合物于－０．６３Ｖ处产生一敏锐的单扫描示波极谱波。硒含量在０．３－８０ｎｇ／ｍｌ范围内与波高有线性关系,检出限达０．１５ｎｇ／ｍｌ。利用该波测定实际试样中痕量硒,结果较好。     

A novel, simple and sensitive resonance scattering spectral method for the determination of chlorite in water by means of rhodamine B

A new resonance scattering method was proposed for the determination of chlorite, basing on the resonance scattering effect of rhodamine dye. In HCl-sodium acetate buffer solution, chlorite oxidizes 1- into 12 and the reaction of 12 and excess 1- results in If. It is respectively combined with rhodaminc dyes, including rhodamine B （RhB）, butyl rhodamine B （b-RhB）, rhodamine G （RhG） and rhodamine S （RhS）, to form association complex particles, which exhibit stronger resonance scattering （RS） effect at 400 nm. The chlorite concentration of ClO2 in the range of 0.00726-0.218 μg/ml, 0.0102-0.292 μg/ml, 0.00726-0.145 μg/ml and 0.0290- 0.174 μg/ml is respectively linear to the RS intensity of association complex particle systems at 400 nm for the RhB, b-RhB, RhG and RhS. The detection limits of the four systems were respectively 0.00436, 0.00652, 0.00580 and 0.01450μg/ml ClO2^-. In the four systems, the RhB system possesses good stability and high sensitivity. It has been applied to the analysis of chlorite in wastewater with satisfactory results.     

甲萘威在蒙脱石和高岭石表面的吸附行为研究

研究了甲萘威在蒙脱石和高岭石两种粘土矿物表面的吸附行为,考察了时间、pH值和农药浓度对吸附的影响,并用FTIR探讨了其吸附机理。结果表明,蒙脱石和高岭石对甲萘威的吸附是一个先快后慢的过程,10h吸附可基本达到平衡。用动力学方程对甲萘威的吸附过程进行拟合,发现Elovich方程为最佳模型(R20.93,p0.05,n=12),其次是一级动力学方程和双常数方程;甲萘威在蒙脱石和高岭石表面的等温吸附均很好地符合Langmuir方程(R20.99,p0.05,n=6),其最大吸附量分别为3.651mg/g和1.688mg/g;蒙脱石对甲萘威的吸附强度大于高岭石;在实验pH范围内,甲萘威在两种矿物表面的吸附量均随体系初始pH的升高而减小;红外光谱分析结果表明,甲萘威分子可能通过氢键与蒙脱石和高岭石发生结合。     

液液萃取-高效液相色谱法同时测定饮用水中阿特拉津与甲萘威

通过液液萃取-高效液相色谱法实现了饮用水中农药残留阿特拉津与甲萘威的同时测定。用二氯甲烷萃取水样中阿特拉津与甲萘威,浓缩定容后,以甲醇∶水=60∶40(体积分数)为流动相,用Zorbax SB-C18柱进行分离,通过具有紫外检测器的高效液相色谱仪进行测定。阿特拉津与甲萘威的最低检出限均可达0.000 1 mg/L,加标量为1 ug时平均回收率分别为85.45%和83.35%,加标量为0.1 ug时平均回收率分别为81.09%和80.23%。平行7次进行精密度试验,相对标准差在4.10%～4.59%。结果表明:方法简便、准确、快速、重现性好,适合饮用水中阿特拉津与甲萘威的同时测定。     

在线分离富集FI分光光度法直接测定铜

本文针对ＡＡＳ法测定痕量铜时，大量铁存在表现干扰，研究并建立了流动注射（ＦＩ）在线螯合树脂分离富集光度法直接测定痕量铜的新方法，具有灵敏度高、选择性强；因此，已成功地用于水样中痕量铜的测定，该法在水质检验和环境监测中有一定的适用性．     

气相色谱法测定水中甲萘威

通过改进预处理方法,采用带氮磷检测器的毛细柱气相色谱仪测定水中甲萘威的含量,得到了较好的精密度和准确度。     

超高效液相色谱-串联四级杆质谱法快速测定阿特拉津、甲萘威、微囊藻毒素LR、丙烯酰胺和联苯胺

以地表水环境质量标准为依据,建立了直接进样-超高效液相色谱-串联四级杆质谱法快速同时测定地表水中阿特拉津、甲萘威、微囊藻毒素LR、联苯胺和丙烯酰胺的方法。水样采集后经0．22μm滤膜过滤后直接进样,使用C18反相柱为分离柱,柱温40℃,流速0．2 ml/min,乙腈和甲酸水(0．1%)作为流动相,采用梯度洗脱,串联质谱采用MRM模式,使用ESI(+)源电离水样,每个样品分析时间仅需2．5 min。五种物质检出限为0．0001~0．0003 mg/L,加标回收率为80．0%~118．9%,满足国家标准要求。针对地表水所需检测项目进行优化,提高了实验室水质检测效率,同时测定多组分且分析时间短,适用于地表水中相关项目的监测。