A new method for the determination of trichloroacetic acid in spruce foliage and other environmental media

Trichloroacetic acid (TCAA) is a phytotoxic chemical, present throughout the environment. The majority of methods for analysis of TCAA require chemical derivatisation and multiple extraction steps prior to analysis by gas-chromatography. Here, a new analytical method for TCAA determination in environmental matrices is reported. The method is based on a modified Nielsen-Kryger steam distillation that combines into one 1 h reflux the thermal decarboxylation of TCAA to CHCl3 and the partitioning and concentration of the CHCl3 into 5 ml of hexane, which is analysed by GC. Sample preparation is minimal and no matrix standard additions are required. The background CHCl3 in the sample is removed prior to extraction by degassing the solution for 1 h with nitrogen. Optimisation of the method gave recoveries from three separate solutions of 0.31 ppb aqueous TCAA standards of 93 +/- 15% (n = 9), 110 +/- 9% (n = 9) and 105 +/- 11% (n = 6). The extraction method has been compared with a decarboxylation and headspace GC method for determination of TCAA in Sitka spruce needles. No significant difference in TCAA concentration or replicate precision between the two methods was observed.     

Interlaboratory trial to determine the analytical state-of-the-art of bromate determination in drinking water

The new European Directive for water intended for human consumption has established a regulatory level for bromate at 10 microg L(-1). This Maximum Admissible Concentration requires analytical methods with detection limits of a least 2.5 microg L(-1). A project funded by the Standards, Measurements and Testing Programme of the European Commission has enabled the improvement and/or development of methods for the determination of bromate at such concentration levels. This collaborative work was concluded by the organisation of an interlaboratory trial involving 26 European laboratories, which enabled the testing of both a draft ISO Standard method and alternative methods. This paper presents the results of this interlaboratory trial, along with results of a bromate stability study. The progress made with respect to the analytical state-of-the-art for bromate will greatly benefit the quality of measurements carried out in water quality monitoring.     

Addressing the challenges of tetracycline analysis in soil: extraction, clean-up, and matrix effects in LC-MS

An optimized extraction and clean-up method for the analysis of chlortetracycline, doxycycline, oxytetracycline, and tetracycline antibiotics in soil is presented in this work. Soil extraction using different solvents was performed, but the use of a 50 : 50 (v/v) methanol : acetate buffer (pH 8) solvent mixture in a pressurized liquid extraction (PLE) system proved to give the best extraction efficiency and reproducibility. The effect of soil composition on the PLE extraction efficiency was also examined, and results indicated that recovery data for one soil is not necessarily consistent with other soil types containing different compositions of clay and organic matter content. The percent recoveries of the optimized PLE method varied between the soils and ranged from 22-99%, depending on soil type, and more specifically clay content. In addition, the extent of ionization suppression caused by co-extracted humic acids was examined in an ion trap mass spectrometer (MS), and a single quadrupole MS. It was found that under positive electrospray ionization, the single quadrupole MS was less susceptible to ionization suppression than the ion trap MS. Therefore, various sample clean-up procedures were evaluated to selectively reduce the amount of co-extracted humic acids in the soil extracts. The most effective clean-up was obtained from the use of StrataX sorbent in combination with a strong anion exchange cartridge.     

Comparison of three sampling and analytical methods for the determination of airborne hexavalent chromium

A field study was conducted with the goal of comparing the performance of three recently developed or modified sampling and analytical methods for the determination of airborne hexavalent chromium (Cr(VI)). The study was carried out in a hard chrome electroplating facility and in a jet engine manufacturing facility where airborne Cr(VI) was expected to be present. The analytical methods evaluated included two laboratory-based procedures (OSHA Method ID-215 and NIOSH Method 7605) and a field-portable method (NIOSH Method 7703). These three methods employ an identical sampling methodology: collection of Cr(VI)-containing aerosol on a polyvinyl chloride (PVC) filter housed in a sampling cassette, which is connected to a personal sampling pump calibrated at an appropriate flow rate. The basis of the analytical methods for all three methods involves extraction of the PVC filter in alkaline buffer solution, chemical isolation of the Cr(VI) ion, complexation of the Cr(VI) ion with 1,5-diphenylcarbazide, and spectrometric measurement of the violet chromium diphenylcarbazone complex at 540 nm. However, there are notable specific differences within the sample preparation procedures used in three methods. To assess the comparability of the three measurement protocols, a total of 20 side-by-side air samples were collected, equally divided between a chromic acid electroplating operation and a spray paint operation where water soluble forms of Cr(VI) were used. A range of Cr(VI) concentrations from 0.6 to 960 microg m(-3), with Cr(VI) mass loadings ranging from 0.4 to 32 microg, was measured at the two operations. The equivalence of the means of the log-transformed Cr(VI) concentrations obtained from the different analytical methods was compared. Based on analysis of variance (ANOVA) results, no statistically significant differences were observed between mean values measured using each of the three methods. Small but statistically significant differences were observed between results obtained from performance evaluation samples for the NIOSH field method and the OSHA laboratory method.     

氨基酸法现场快速测定废水中的磷酸盐

通过磷酸盐与钼酸盐、氨基酸反应使样品呈淡蓝色,讨论了在事故现场快速测定水中磷的方法。试验表明方法灵敏,操作简单快速。检测范围0～15mg/L。     

Evaluation of analytical strategies for the determination of metal concentrations to assess landfill leachate contamination

Due to the complex nature of landfill leachates, metal and metalloid analyses prove to be tricky and suffer from a lack of standard protocols. A complete approach has been adopted to investigate the influence of the different steps during the sample processing of French landfill leachates. The validation of the entire protocol has been achieved using a laboratory reference material. This material, which is a real landfill leachate, is representative of real samples. Its evaluation has allowed a quality control for metal and metalloid analyses in landfill leachates. Precautions concerning storage temperature, aeration and filtration are proposed to perform accurate metal analyses in these complex matrices. The sample processing has been applied to the seasonal monitoring of a French landfill. The assessment of major leachate metallic contaminants such as As, Cr, Sb, Sn, has been performed by evaluating the relative enrichment of metals and metalloids in comparison with rain water and groundwater. In addition, hydrological data are useful and complementary information for pointing out the main factors affecting metal concentrations and thus their potential remobilisation pathways.     

The determination of the extractability of selected elements from agricultural soil

Concentrations of Ag, Al, Ba, Cd, Co, Cr, Cu, Fe, K, Mn, Na, Ni, Pb, Sr, and Zn—isolated by sequential extraction steps from apple orchard soil—were analyzed by inductively coupled plasma-atomic emission spectroscopy and compared to the total amount of metal in soil determined by XRF. The extractable amount of each metal was calculated by the extraction yields of the four steps. The LODs of the different elements in all extracts ware below 3 μg/L except for Ba (steps 1 and 2), Cu (step 1), Fe (all steps), K (steps 1–3), Mn (step 2), Na (steps 1–3), Ni (step 1), Pb (steps 1 and 4), and Zn (steps 1 and 2). The highest LOD (>10 μg/L) was found for Fe, K, and Na (step 1). The recovery of all metals after four sequential extraction steps was 90–112%. The repeatability (<1.1%), the intermediate precision (<5.3%), the day-to-day reproducibility (<6.2%), and the overall uncertainty of measurement (approximately 4–8.5%) for all analyzed metals supports the choice of the method used.     

Comparison study of five analytical methods for the fractionation and subsequent determination of aluminium in natural water samples

Five methods for aluminium fractionation used in different laboratories in Norway and Finland were compared using six control, 75 soil water and 10 lake water samples. Different fractionation principles [cation exchange, formation of the Pyrocatechol Violet (PCV) or quinolin-8-ol (oxine) complex], types of cation exchanger [Amberlite (Na/H) or Bond Elut (H)], reaction time (from 2.3 s), flow systems (flow injection analysis or segmented flow) and determination principles (molecular absorption spectrometry or ICP-AES) were tested. Determination of the 'labile' fraction was strongly dependent on the method used and the largest differences were observed between the ICP-AES method with cation exchange (Bond Elut H form) and the 'quickly reacting' method (oxine, 2.3 s). Different flow systems, both using cation exchange and determination of the PCV complex but with different reaction times and an extra acidification step, resulted in large differences in the 'reactive' and 'non-labile' fractions determined. However, the determination of the labile fraction gave similar results with both these methods. The two different types of cation exchanger used (with and without pH buffering and with different counter ions) in the ICP-AES methods resulted in differences, mainly because of a smaller 'non-labile' fraction in the non-buffered system. The two flow injection systems (oxine and PCV complexation) showed common trends, which may be connected with the short reaction times used. Comparison with theoretical equilibrium calculations using the model ALCHEMI suggested that the best correlation for the determination of the 'labile' fraction were obtained with the ICP-AES method with an Amberlite column.     

Optimization of sampling for the determination of mean radium-226 concentration in surface soil

There are thousands of properties in the United States on which the soil has been contaminated to some degree with uranium mill tailings. An effort is now underway by the United States Department of Energy to identify sites contaminated with tailings and to perform remedial action when ²²⁶Ra levels exceed current guidelines. Because of the large number of sites involved, it is imperative that sample collection be performed in a cost-effective manner. In this paper we describe the results of a study in which we compared the efficiencies of different methods of sample collection in order to determine an optimal method for estimating the mean ²²⁶Ra concentration in soil. The study involved a field experiment in which extensive sampling was performed on sites known to be contaminated with uranium tailings. The experiment was designed to identify the advantages and limitations of composite sampling, the relative merits of random and uniformly spaced sample collection, the use of field gamma measurements for supplementing and reducing soil sample collection, and practical levels of accuracy and precision that can be obtained. Conclusions regarding gamma measurements are unique to ²²⁶Ra contamination. On the other hand, conclusions concerning composite sampling and random versus uniformly spaced sampling may depend primarily on the way the contamination was spread by man and hence may not be unique to ²²⁶Ra.Research sponsored by the Department of Remedial Action Projects, Office of Terminal Waste Disposal, U. S. Department of Energy under contract DE-AC05-84OR21400 with the Martin Marietta Energy Systems, Inc.ORNL—Grand Junction Office, Grand Junction, Colorado.     

离子色谱法测定废气中的丙酸

建立了用离子色谱法测定有组织废气和无组织废气中丙酸的新方法,常规无机阴离子对该方法的测定没有干扰。对实际废气样品进行分析,丙酸的回收率分别为91．5％～106％。该方法分析速度快,所需样品量少,且无需复杂的前处理,简便、灵敏、可靠。     

Validation of spectrophotometric method for Se(IV) determination: analytical applications

As selenium is an important part of the antioxidant enzymes and also because there are several studies suggesting a possible link between cancer and selenium deficiency, this paper presents a spectrophotometric method for the assay of Se(IV), using N,N-diethyl-p-phenylenediamine monohydrochloride as reagent. The proposed method is based on the reaction between the selenium and potassium iodide in low acidic medium, when iodine is released. This last product will further oxidise the new reagent. The final obtained product is strongly coloured in red and has an absorption maximum at 552 nm and molar extinction coefficient (ε) of 6.1?×?10⁴ L mol^?1 cm^?1. The optimum working conditions were established, and the developed method was validated, being characterised by a good linearity (in the range of 0.5–3.0 μg/mL), a limit of detection (0.0573 μg/mL) and a limit of quantification (0.1737 μg/mL). At the same time, the repeatability, the precision of the method and the accuracy were established. The proposed and validated method was applied with good results for the determination of Se(IV) in spring and bottled water from Iasi and also in pharmaceutical and cosmetic products.     

Second derivative spectroscopy for the determination of volatilized ammonia from urea-amended soil

A second derivative spectrometer custom fitted with a 1 m stainless steel White cell and maintained at 105°C is used to make real-time measurements of volatilized NH₃ from urea-amended soil. Comparison of the technique to impinger data shows a 5–16% discrepancy between the two techniques; however, other experiments presented suggests that this is not real. Sulfur dioxide and nitrous oxide interferences are discussed, though they were not found to be present in this study. Instrument response time is shown to be fast if 67% of the total response is achieved in less than 5 min. Fast response is achieved for ammonia if wall-adsorption effects are minimal and if ammonia mass flow is maintained at 0.2 μg min^-1.     

Sampling and analytical methodology development for the determination of primary and secondary low molecular weight amines in ambient air

In this project, a sampling device and an analytical method have been developed to simultaneously analyse the most frequently found low molecular weight amines, including aliphatic, aromatic and alcohol amines. These amines are diethanolamine, ethanolamine, methylamine, isopropylamine, morpholine, dimethylamine, and aniline. A sampling device was developed using a 37 mm cassette with glass fibre filters impregnated with sulfuric acid. Immediately after sampling, the filter was transferred to vials containing a solution of dansyl chloride. Dansyl chloride was used for derivatisation because it forms aromatic sulfonamides that are fluorescent and easy to protonate for MS detection. The effect of using an internal standard made with the dansylated derivative of 1-(2-methoxyphenyl)piperazine (MOPIP) on the uncertainty and efficiency of the method was also evaluated. This internal standard was spiked directly onto filters. The coupling of HPLC/ESI-MS was used for the simultaneous analysis of all the derivatives. This method showed detection limits of about 0.03 microg mL(-1) to 0.3 microg mL(-1) of amine with an average expanded uncertainty of 3% to 6% depending on the amine. The methodology recoveries are close to 100% for all the amines, and the overall estimated expanded uncertainties vary between 10% and 13% depending on the amine. This new strategy will be useful in evaluating workplace air since a unique sampling system will be used, independent of the amine to be quantified.     

石墨炉原子吸收光谱法测定土壤中的微量砷

土壤样品经ＨＮＯ３－ＨＣＩＯ４消解处理后,采用Ｎｉ作为基体改进剂,偏振塞曼效应扣去背景,实现了砷的石墨炉原子吸收法的直接测定。该方法操作简单,干扰少,灵敏度高,砷的检测下限为０．７ｎｇ／ｍｌ,样品分析回收率９４％－１０８％,相对标准偏差５．１％。     

微波萃取-气相色谱/质谱法测定土壤中的有机氯农药

通过微波萃取提取土壤中的有机氯农药,萃取溶液经浓硫酸脱色、佛罗里硅土柱净化,最后用气相色谱/质谱法分析.以石英砂为基体进行加标回收测定,有机氯农药的回收率在75.5%～103%之间,检出限为0.01μg/kg.     

A field-based spectrophotometric flow-injection system for automatic determination of chloride in soil water

The use of chloride as a tracer for soil water investigations is discussed. Limitations with laboratory based soil core and field based sampling are considered with respect to the poor suitability of the data for rigorous assessment of mechanistic models. Investigation of water movement in soil has been restricted by limitations in spatial and temporal sampling. Fine resolution sampling generates large numbers of samples which cause problems with post sampling laboratory analysis. This paper describes a field-based system for the analysis of chloride in soil water. There are three component parts to the system, (i) a custom sampling sub-system comprising of ceramic cup suction samplers and sample traps, (ii) a sample routing sub-system to channel sample to (iii) a sample analysis sub-system utilizing a flow injection method for sample analysis using a custom built photo-diode detector. The three sub-systems were controlled by a suitably equipped personal computer. A calibration procedure is described with a third order polynomial equation derived to convert millivolt response from the detector into chloride concentration. Field and laboratory data from a tracer experiment are presented and discussed, and it is concluded that the system is well suited to field-based applications. Finally it is noted that the photo-detector is suitable for colourimetric analysis of any tracer with suitable chemical determination.     

Soil heterogeneity effects on acid flushing of lead-contaminated soil

A compact model for evaluation of acid flushing of heavy-metal-contaminated soil in a small-scale on-site treatment plant is proposed. The model assumes that the soil was re-packed in a container after excavation resulting in a soil structure with heterogeneous and random physical and chemical properties. To evaluate the effects of heterogeneity on the efficiency of contaminant removal by acid flushing, a numerical analysis of lead transport in the heterogeneous soil medium was performed. The model examines cation exchange and surface complexation reactions involving three cations (Ca, Pb, and H) and one anion (Cl) in both dissolved and exchangeable forms, two Pb surface complexes (SOPbCl and SOPbOH), and one Cl surface complex (SOH₂Cl). The transport of these species during flushing with acid in a synthetically generated two-dimensional heterogeneous soil was simulated in the model. Results indicated that the flushing fluid preferentially followed pathways with large permeability. The heterogeneous cation exchange capacity (CEC) distribution and surface complexation sites had a significant effect on the transport of dissolved species. Because the CEC was set to a relatively low value, Pb was adsorbed mainly as surface complexes (SOPbCl and SOPbOH). Simulation results suggest that blocks of low hydraulic conductivity located in the upper part of the model domain greatly impede solute transport. Ponding conditions did not significantly affect the efficiency of decontamination. The model and its results are useful in the design of small-scale treatment plants for acid flushing.     

Accumulation of different sulfur fractions in Chinese forest soil under acid deposition

Atmogenic sulfur (S) deposition loading by acid rain is one of the biggest environmental problems in China. It is important to know the accumulated S stored in soil, because eventually the size (and also the "desorption" rate) determines how rapidly the soil water pH responds to decrease in S deposition. The S fractions and the ratio of total carbon/total sulfur (C/S) of forest soil in 9 catchments were investigated by comparing soils at the rural and urban sites in China. The S fractions included water-soluble sulfate-S (SO(4)-S), adsorbed SO(4)-S, insoluble SO(4)-S and organic S. The ratio of C/S in soil at the rural site was significantly (p < 0.05) greater than that at the urban site. C/S of soil in the A horizon was significantly (p < 0.05) and negatively correlated with the wet S-deposition rate. The ratio of C/S presents a better indicator for atmogenic S loading. Organic S was the dominant form in soils at rural sites; contributing more than 69% of the total S in the uppermost 30 cm soil. Organic S and adsorbed SO(4)-S were the main forms of S in soil at urban sites. High contents of water-soluble SO(4)-S and adsorbed SO(4)-S were found in uppermost 30 cm soils at urban sites but not at rural sites. Decades of acid rain have caused accumulation of inorganic SO(4)-S in Chinese forest soil especially at the urban sites. The soil at urban sites had been firstly acidified, and the impacts on the forest ecosystem in these areas should be noticed.     

Methodological uncertainties in multi-regression analyses of middle-atmospheric data series

Multi-regression analyses have often been used recently to detect trends, in particular in ozone or temperature data sets in the stratosphere. The confidence in detecting trends depends on a number of factors which generate uncertainties. Part of these uncertainties comes from the random variability and these are what is usually considered. They can be statistically estimated from residual deviations between the data and the fitting model. However, interferences between different sources of variability affecting the data set, such as the Quasi-Biennal Oscillation (QBO), volcanic aerosols, solar flux variability and the trend can also be a critical source of errors. This type of error has hitherto not been well quantified. In this work an artificial data series has been generated to carry out such estimates. The sources of errors considered here are: the length of the data series, the dependence on the choice of parameters used in the fitting model and the time evolution of the trend in the data series. Curves provided here, will permit future studies to test the magnitude of the methodological bias expected for a given case, as shown in several real examples. It is found that, if the data series is shorter than a decade, the uncertainties are very large, whatever factors are chosen to identify the source of the variability. However the errors can be limited when dealing with natural variability, if a sufficient number of periods (for periodic forcings) are covered by the analysed dataset. However when analysing the trend, the response to volcanic eruption induces a bias, whatever the length of the data series. The signal to noise ratio is a key factor: doubling the noise increases the period for which data is required in order to obtain an error smaller than 10%, from 1 to 3-4 decades. Moreover, if non-linear trends are superimposed on the data, and if the length of the series is longer than five years, a non-linear function has to be used to estimate trends. When applied to real data series, and when a breakpoint in the series occurs, the study reveals that data extending over 5 years are needed to detect a significant change in the slope of the ozone trends at mid-latitudes.