超声水浴-王水浸提-全自动测汞仪测定重度污染土壤中的总汞

为准确测定重度污染土壤中的总汞含量,本文建立了以超声水浴辅助王水浸提,使用全自动测汞仪测定的方法。 通过单因素实验考察了王水用量、超声时间和超声温度对土壤中总汞测定的影响,得到最佳前处理方法,最后应用建立的方法对重度污染土壤进行方法验证。确定了0.5 g土壤样品中加入5 mL的王水溶液,放入超声波清洗器中70℃水浴下超声提取70 min,使用超纯水定容至50mL的前处理方法,直接进样测定的实验方法。对该实验进行验证,结果表明,该方法汞低标准曲线汞含量在0～20ng范围内线性良好,相关系数R=0.9995;汞高标准曲线汞含量在20～150 ng范围内线性良好,相关系数R=0.9993;方法检出限为0.0055 mg/kg,方法定量下限为0.022 mg/kg;通过对土壤样品及土壤加标样品的测定,回收率为90.40～116.80%,表明该方法的准确度较高,RSD为1.89～3.34%（n=6）,表明该方法的精确度较高。超声水浴-王水浸提-全自动测汞仪法用于测定重度污染土壤中的总汞,前处理简单,自动化程度较高,可快速,高效的用于重度污染土壤总汞测定工作。     

An improved approach for the determination of plasma-free catecholamines by HPLC-ED: Application to normal and hypertensive patients

Summary A dual-step procedure for the rapid, quantitative isolation of free catecholamines (norepinephrine, epinephrine and dopamine) from plasma, using a little column of CM-Sephadex and alumina adsorption, is described. Sensitive high performance liquid chromatography is also discussed, employing an amperometric detector for the quantitative determination. The recovery of the three catecholamines, and of N-methyldopamine used as the internal standard, was about 70–80%; the detection limits were 2pg for norepinephrine, 3pg for epinephrine and 3pg for dopamine. The combination of the rather specific and easy to handle two-step sample clean-up procedure, the high resolving power of the chromatography and the high sensitivity of electrochemical detection provided a simple method for the determination of free catecholamines in plasma samples of normal and essential hypertensive subjects under different conditions (supine position for 45 min, standing for 5 and 10 min). It was found that a significant increase in epinephrine levels (P<0.01) occurred in hypertensive patients under the three conditions studied.     

Preparation and evaluation of a chrysotile asbestos-containing standard material for validating x-ray diffractometric quantitation

A standard material containing chrysotile asbestos for the validation of x-ray diffractometric quantitation was developed using an asbestos-containing building material i.e., perlite board. The board as the base material was crushed, pulverized, and homogenized. The homogeneity of the powder of perlite board was estimated by analysis of variance. The diffraction intensity values of the crystalline phases and the concentrations of elements determined by x-ray diffractometry and x-ray fluorescence analysis were used for analysis of variance. There is no significant difference between the within-bottle variance and the between-bottle variance, indicating that the powdered perlite board was sufficiently homogenous. The concentration of chrysotile in the material was determined using two methods: an internal standard/x-ray diffractometry method and the x-ray diffractometry/Rietveld refinement. The concentration of chrysotile in the material was determined by an internal standard/x-ray diffractometry method and the material had a chrysotile concentration of 24.1 ± 0.2 mass%.     

Determination of Hg,As, Pb,and Cd in Orchard Soils by Sequential Injection Vapor Generation Atomic Fluorescence Spectrometry

An analytical procedure was developed for determination of Hg, As, Pb, and Cd in soil samples using sequential injection vapor generation atomic fluorescence spectrometry (SI-VG-AFS) with sample preparation by microwave digestion system. The effects of analytical conditions on the fluorescence intensity were investigated and optimized. Under the optimized condition, the detection limits of the method were 5, 68, 40, and 3 ng L^?1 for Hg, As, Pb, and Cd, respectively. The accuracy of method was verified by the determination of the certified reference soil, and the recoveries for Hg, As, Pb, and Cd were in the range of 98.7–106.1%. The proposed method has been successfully applied to determine the heavy metals in navel orange orchard soils in Ganzhou, and the environmental quality of the orchard soils was assessed based on the content of the heavy metals. According to the second criterion of environmental quality standard for soils, Pb content in all soil samples collected from the orchards of 18 districts were within safe limits, but a few orchards were slightly contaminated with Hg, As, and Cd. Comparison of heavy metal mean concentrations with the safe limits of environmental quality standard for soils, the quality of Ganzhou navel orange orchard soils were in line with the request of the green food production base.     

Toward a quantitative description of the anodic oxide films on aluminum

A method to quantify the composition of anodic oxide films on aluminum using Infrared Spectroscopic Ellipsometry (IRSE) is proposed. It consists of obtaining the absorption coefficient of the film as a function of wavelength. Using values of the absorption coefficients for the pure components of the film, the percentages (mole or wt%) of each component in the sample can be calculated.The method is demonstrated in a study of the structure of the oxide film on electropolished aluminum and the anodically formed barrier layer film. Both surface oxides were found to be initially a form of amorphous Al₂O₃. While the barrier film is essentially free of water as prepared, the film on electropolished aluminum contained about 25 wt% water. Hydration of both types of films by immersion in boiling water results in the formation of pseudoboehmite (AlOOH). The technique may have more general applicability to the quantitative determination of the composition of corrosion films and other surface layers on metals.     

Rapid soil analyses of overburden material from historic mines with SNMS

Plasma-based Secondary Neutral Mass Spectrometry (SNMS) is designed and usually used for depth-resolved determination of the elements in inhomogeneous samples. This report shows that it is also advantageous for the quantification of the total elemental inventory of granular material. As an example of such an application, the quantitative elemental analysis of soil samples from residues of three historic mines in Baden-Württemberg is presented. The results obtained with SNMS, using a high primary energy of E_p = 1340 eV, were compared to the concentrations measured by Atomic Absorption Spectroscopy (AAS) and X-Ray Fluorescence (XRF). A reasonable correspondence was found with a mean deviation between all three methods of about 50%. However, SNMS measurements of standard soils, without any matrix adaptation of the elemental sensitivities, exhibited mean deviations from the certified concentrations of only 20–30 wt% down to concentrations below 10^–2 wt%. The advantages of SNMS against AAS and XRF are its simple sample preparation and the rapid detection of all elements in the analyzed material within some 10 min. In each of the three samples chromium, nickel, copper, zink and lead (only sample HS 64) were found in concentrations exceeding the limiting values of the German Sewage Sludge Ordinance (SSO).     

A rapid method for the determination of organic carbon in soil

TIURIN'S method for the determination of organic carbon in soil is modified to give results practically identical with those of the dry combustion method. The standard deviation of a single determination is only 12%. By using 50 mg of soil and 10 ml of 0.2 N dichromate solution, soils with a carbon, content up to 12% can bo analysed. The method is suitable for all soils except those containing much chloride or reducing substances other than organic carbon Carbonates do not interfere.     

Effect of sample preparation conditions on the determination of the total concentrations of unsymmetrical dimethylhydrazine in soils

It is shown that, for a correct determination of the total concentration of unsymmetrical dimethylhydrazine (UDMH) in soil, it is necessary to consider the simultaneous presence of active products of its transformation, capable of hydrolysis to the parent compound, such as formic acid 1,1-dimethylhydrazide (FADMH). A comparative study is performed of the methods known in the literature for sample preparation to select conditions for the quantitative extraction of UDMH bonded by various mechanisms to organic and mineral fractions of soil, as well as FADMH as one of the most common active transformation products. It is found that the distillation with a 40% NaOH solution with an addition of Na₂S enables the quantitative recovery of UDMH and FADMH from soils of all types and the determination of the maximum concentration of UDMH in the analysis of real samples of contaminated soils, which allows us to recommend this option to determine the total concentration of UDMH.     

The problem of arsenic interference in the analysis of Cd to evaluate its extractability in soils contaminated by arsenic

The arsenic (As) spectral interference observed in the determination of cadmium (Cd) by inductively coupled plasma atomic emission spectrometry (ICP-AES) was studied in atomic absorption spectrometry (AAS) using flame (FAAS) and graphite furnace (GFAAS) as atomizers. The soils of 15 kitchen gardens located near two smelters in the North of France were selected according the ratio As/Cd. Four different extracting solutions usually used to evaluate the mobility of Cd were chosen to extract Cd from these soil samples: citric acid 0.11 M, acetic acid 0.11 M, calcium chloride 0.01 M and water. The quantitative determinations of Cd in the 15 soils for each solvent were investigated by ICP-AES at two lines (228.802 and 214.438 nm) and by FAAS or GFAAS with two-way background compensation. Compared to the Cd concentrations measured in the acid solutions and in the CaCl₂ solution after the addition of a chemical modifier, it was clearly demonstrated that the high-speed self-reversal background compensation (HSSR-method) was the method of choice to eliminate the spectral interference of As during Cd determination by FAAS and by GFAAS. In water, it was shown that the deuterium lamp used for the background compensation (D₂-method) was able to eliminate the most of the As interference. In comparison with Cd concentrations in water after adding a chemical modifier, those obtained with the HSSR-method were similar and a very good correlation was obtained between these two methods (R² = 0.995). It was therefore established that the HSSR-method would be able to replace the chemical modifiers to eliminate As interference in the determination of Cd-extractable from As contaminated soils.     

气相色谱-质谱法检测鳗鱼中三氯杀螨醇残留量

建立了固相萃取-气相色谱-质谱(SPE-GC-MS)检测鳗鱼中三氯杀螨醇残留量的分析方法。样品先用正己烷配合乙腈、水均质提取,再加入氯化钠继续均质,离心分层;取部分乙腈层溶液浓缩后过Florisil柱净化,用正己烷淋洗去除油脂,再用乙酸乙酯-正己烷(1:19, v/v)洗脱分析物;将洗脱液吹干后用正己烷溶解定容,并进行GC-MS分析。采用选择离子监测(SIM)模式检测,外标法定量。在优化的样品前处理条件和GC-MS条件下,方法的定量限(S/N=10)小于0.01 mg/kg;在加标水平为0.01～0.1 mg/kg时,回收率为91%～105%,相对标准偏差为4.3%～6.1%。该方法准确、灵敏、快速,可满足鳗鱼中三氯杀螨醇残留的检测要求。     

Fast determination of phenols in contaminated soils

An extraction method for the determination of phenols in contaminated soils, based on the application of solid-phase microextraction (SPME) coupled with GC-flame ionization detection analysis, was developed and tested. This method was developed using a natural soil spiked with phenol to a concentration level typical of an acute contamination event that can occur in an industrial site. The effects of the extraction parameters (pH, extraction time and salt concentration) on the extraction efficiency were studied and the method was then applied to determine the pollutant concentration at the beginning and during the biological treatment of a soil, contaminated with phenol and 3-chlorophenol, respectively. The SPME results were validated by comparison with those obtained with an US Environmental Protection Agency certified extraction method. The SPME method was also successfully applied to the determination of the adsorption behavior of 3-chlorophenol on a natural clay soil and was shown to be suitable for different matrices and phenolic compounds. Application of SPME technique results in a sharp reduction of the extraction times with negligible solvent consumption.     

Comparison of perchloroethylene extraction techniques in soil gas survey quantification

Subsurface pollution by volatile organic compounds has emerged as a widespread problem in industrialized countries. This study compares static headspace technique and methanol extraction/purge-and-trap analysis followed by thermal desorption/gas chromatography in attempts for quantification of gas survey results in the determination of these chemicals in soil. Several soils were contaminated with aqueous solution of perchloroethylene (PCE) (140 mg L⁻¹) using a vapor treatment method. Soil spiking took place up to 24 h in desiccator by exposing individual soil samples contained in open 40 mL glass vials to PCE evaporated from the solution. After exposure the samples were stored and analyzed within 2 days. The achieved results strongly suggest that gas extraction can provide quantitative results, regarding PCE concentration in soils, which are not significantly different from liquid based extraction analysis.      

Determination of glyphosate residues in plants by precolumn derivatization and coupled-column liquid chromatography with fluorescence detection

A rapid method was developed for the trace-level determination of glyphosate in olives. After extraction of the glyphosate with water-dichloromethane and simultaneous removal of the olive oil, an aliquot of the aqueous extract is derivatized with 9-fluoroenylmethyl chloroformate (9-fluorenylmethoxycarbonyl chloride; FMOC-CI) to produce a highly fluorescent derivative. A 2 mL aliquot of this extract is injected directly into a coupled-column liquid chromatography system with fluorimetric detection (LC/LC-FD). The procedure was validated by recovery experiments at 3 spiking levels; recoveries ranged from 80 to 97% with relative standard deviations of 3-6%. The limits of detection and quantitation were estimated to be 0.01 and 0.05 mg/kg, respectively. The method was also applied to other plant materials, i.e., tomato plants, strawberry plants, and pear trees (branches, leaves, and fruits) suspected to be contaminated by glyphosate. In all these cases, the extraction was performed in aqueous media. The derivatization reaction was modified by increasing the FMOC-CI concentration, to ensure a quantitative reaction between analyte and reagent in the presence of high levels of coextractives, which also react with FMOC-CI. The final determination was by LC/LC-FD, yielding a rapid, selective, and sensitive method for the determination of glyphosate residues in these samples. The method was tested with real-world samples after application of glyphosate to the surrounding area of crops.     

The determination of small amounts of organic hydroperoxides in the presence of hindered amine light stabilizers and their nitroxyls

A method for the quantitative determination of hydroperoxide (ROOH) in the presence of hindered amine light stabilizers (HALS) and/or their nitroxyl free radical derivatives has been elaborated. The method is based on the quantitative reduction of hydroperoxides by triphenyl phosphine. The resulting compounds (alcohols) are then determined by GLC using the internal standard technique. The method has been tested on the hydroperoxides derived from 2,4-dimethylpentane. Its sensitivity and reproducibility appear to be comparable with other methods for ROOH determination but, unlike the latter, it has the advantage that its results are not influenced by the presence of HALS and/or their nitroxyl radical derivatives in the analyzed medium.     

Identification and quantification of different species in animal fibres by LC/ESI‐MS analysis of keratin‐derived proteolytic peptides

In the present paper, a proteomic method for species determination in fibres has been developed. Keratin was extracted from yak, wool and cashmere fibres and digested by trypsin, providing peptide mixtures that were analyzed by liquid chromatography coupled with electrospray mass spectrometry (LC/ESI‐MS) in order to identify peptidic species‐specific markers able to differentiate the fibres. Several suitable peptide markers were identified and validated in different fibres of different origin and having undergone different technological treatments, showing 100% specificity and 100% selectivity. Most of the peptide markers were also identified by means of high‐resolution mass spectrometry, confirming the origin from species‐specific keratin sequences. Some peptides were also used for the quantification of the different species in mixed fibres by LC/ESI‐MS. Validation experiments and blind tests confirmed their ability to act as very specific quantitative and qualitative markers. The method here developed is a valid complement to the standard benchmark methods for fibre identification and quantification and will be very useful for assessing the authenticity of textile products. Copyright © 2013 John Wiley & Sons, Ltd.     

Comparison of sample preparation methods for determination of free carbon in boron carbide by X-ray powder diffraction

Several sample preparation methods were evaluated for determination of free carbon in boron carbide powders by quantitative X-ray diffraction method, including ultrasonication, wet ball milling and dry ball milling–wet mixing. Quantitation was based on measuring the integral peak area ratio of the diffraction lines of graphite (002) to boron carbide (012) in samples spiked with pure graphite. The dry milling–wet mixing method provided the best precision and accuracy in all the measurements as well as in determination of free carbon in a boron carbide reference material. There was a linear relationship between the integral peak area ratios and graphite added to boron carbide samples which were purified from their free carbon content. The method provided a low detection limit of 0.05 wt% free carbon.     

Simultaneous determination of parts-per-million level Cr,As, Cd and Pb,and major elements in low level contaminated soils using borate fusion and energy dispersive X-ray fluorescence spectrometry with polarized excitation

Energy-dispersive polarized X-ray fluorescence (ED-P-XRF) spectrometry was evaluated for the analysis of low level contaminated soils for four important contaminant elements (Cr, As, Cd and Pb) and major elements (Fe, Mn, Ti, P, Ca, K, Si, Al, Mg and Na) commonly found in soils. Using a LiBO₂ and Li₂B₄O₇ fusion method, synthetic standards were prepared in Al₂O₃ matrices for trace elements and SiO₂ matrices for major elements. Matrix corrections were based on loss-eliminated alpha coefficients and the sample analysis was carried out on an ‘as-received basis’. The method was validated using certified reference materials. Analytical figures of merit and the effect of the use of catch-weights are presented. The results of this study demonstrate that this ED-P-XRF method is suitable for the as-received analysis of contaminated soils for the determination of low parts-per-million level contaminant elements and percent level major elements.     

Quantitative analysis of fatty-acid-based biofuels produced by wild-type and genetically engineered cyanobacteria by gas chromatography-mass spectrometry

Simple and rapid quantitative determination of fatty-acid-based biofuels is greatly important for the study of genetic engineering progress for biofuels production by microalgae. Ideal biofuels produced from biological systems should be chemically similar to petroleum, like fatty-acid-based molecules including free fatty acids, fatty acid methyl esters, fatty acid ethyl esters, fatty alcohols and fatty alkanes. This study founded a gas chromatography-mass spectrometry (GC-MS) method for simultaneous quantification of seven free fatty acids, nine fatty acid methyl esters, five fatty acid ethyl esters, five fatty alcohols and three fatty alkanes produced by wild-type Synechocystis PCC 6803 and its genetically engineered strain. Data obtained from GC-MS analyses were quantified using internal standard peak area comparisons. The linearity, limit of detection (LOD) and precision (RSD) of the method were evaluated. The results demonstrated that fatty-acid-based biofuels can be directly determined by GC-MS without derivation. Therefore, rapid and reliable quantitative analysis of fatty-acid-based biofuels produced by wild-type and genetically engineered cyanobacteria can be achieved using the GC-MS method founded in this work.     

Scaling model for prediction of radionuclide activity in contaminated soils using a regression triplet technique

A scaling model was built to calculate the activity of alpha emitting radionuclides in contaminated soil in the lysimeter field. Linear regression can be applied for the evaluation of radioactivity measurement data. Activities of the radionuclides ²⁴¹Am, ²³⁸Pu, ^239,240Pu and ⁹⁰Sr obtained by experiments from real contaminated soils of the experimental lysimeter placed in a nuclear power plant (NPP) in Slovakia were evaluated using linear regression models with the method of least squares. A suitable scaling model for monitoring the ²⁴¹Am, ²³⁸Pu, ^239,240Pu alpha radionuclide activity was built using the regression triplet analysis and regression diagnostics. A regular designed scaling model opens the possibilities of longtime activity monitoring of these radionuclides, thus decreasing the number of necessary radiochemical analyses. The Fisher-Snedecor test, however, confirmed that the regression model for ⁹⁰Sr activity monitoring by ²⁴¹Am, ^239,240Pu activity determination in contaminated soils can not be recommended.