Comparison of methods for the extraction and determination of polychlorinated biphenyls in shiphull antifoulings

A method is presented for the determination of PCBs in chlorinated rubber antifoulings. In ten different brands, no PCB concentrations above 0.5 mg kg^?1 were found.     

Determination of etoxazole residues in fruits and vegetables by SPE clean-up and HPLC-DAD

A method for determination of etoxazole residues in apples, strawberries and green beans was developed and validated. The analyte was extracted with acetonitrile from foodstuff and a charcoal-celite cartridge was used for clean-up of raw extracts. Reversed phase high performance liquid chromatography with photodiode array detector (HPLC-DAD) was used for the determination and quantification of etoxazole residues in the studied samples. The calibration graphs of etoxazole in a solvent or three blank matrixes were linear within the tested intervals 0.01–2 mg L^?1, with correlation coefficient of determination >0.999. The combined solid phase extraction (SPE) clean-up and the chromatographic method steps were sensitive and reliable for simultaneous determination of etoxazole residues in the studied samples. The average recoveries of etoxazole in the tested foodstuffs were between 93.4 to 102% at spiking levels of 0.01, 0.10, and 0.50 mg kg^?1, with relative standard deviations ranging from 2.8 to 4.7%, in agreement with directives for method validation in residue analyses. The limit of detection (LOD) of the HPLC-DAD system was 100 pg. The limit of quantification of the entire method was 0.01 mg kg^?1.     

Formaldehyde emission—Comparison of different standard methods

The emission of formaldehyde is an important factor in the evaluation of the environmental and health effects of wood-based board materials. This article gives a comparison between commonly used European test methods: chamber method [EN 717-1, 2004. Wood-based panels—determination of formaldehyde release—Part 1: formaldehyde emission by the chamber method. European Standard, October 2004], gas analysis method [EN 717-2, 1994. Wood-based panels—determination of formaldehyde release—Part 2: formaldehyde release by the gas analysis method, European Standard, November 1994], flask method [EN 717-3, 1996. Wood-based panels—determination of formaldehyde release—Part 3: formaldehyde release by the flask method, European Standard, March 1996], perforator method [EN 120, 1993. Wood based panels—determination of formaldehyde content—extraction method called perforator method, European Standard, September 1993], Japanese test methods: desiccator methods [JIS A 1460, 2001. Building boards. Determination of formaldehyde emission—desiccator method, Japanese Industrial Standard, March 2001 and JAS MAFF 233, 2001] and small chamber method [JIS A 1901, 2003. Determination of the emission of volatile organic compounds and aldehydes for building products—small chamber method, Japanese Industrial Standard, January 2003], for solid wood, particleboard, plywood and medium density fiberboard.The variations between the results from different methods can partly be explained by differences in test conditions. Factors like edge sealing, conditioning of the sample before the test and test temperature have a large effect on the final emission result. The Japanese limit for F **** of 0.3 mg l⁻¹ (in desiccator) for particleboards was found to be equivalent to 0.04 mg m⁻³ in the European chamber test and 2.8 mg per 100 g in the perforator test. The variations in inter-laboratory tests are much larger than in intra-laboratory tests; the coefficient of variation is 16% and 6.0% for the chamber method, 25% and 3.5% for the gas analysis method and 15% and 5.2% for the desiccator method.     

Simultaneous determination of organochlorine and pyrethriod pesticide residues in the Chinese patent medicines by gas chromatography-tandem mass spectrometry

A simple, sensitive, reliable method was developed for the simultaneous determination of organochlorine and pyrethriod pesticide residues in Chinese patent medicines Six ingredient rehmannia pills and Xiaoyao pills. These pesticides were extracted by ethyl acetate. The extraction time and volume of ethyl acetate were optimized. Cleanup of extracts was performed with dispersive-solid phase extraction using graphitized carbon black as the sorbent. The determination of pesticides in the final extracts was carried out by gas chromatography–tandem mass spectrometry in multiple reaction monitoring mode (GC-MS/MS, MRM). The linearity of the calibration curves is good in matrix-matched standard and yields the coefficients of determination (R²) ≥0.99 for all of the target analytes. Under optimized conditions, the average recoveries (five replicates) for most pesticides range from 75.5% to 114.6%, and RSDs are less than 10.0%. The LODs of 18 pesticides in Six ingredient rehmannia pill and Xiaoyao pills are in the range of 0.01–8.82 μg kg^?1. The developed method meets the requirements of pesticide residue analysis and could be effectively used for routine analysis of the organochlorine and pyrethriod pesticide residues in Six ingredient rehmannia pills and Xiaoyao pills.     

Gas chromatographic determination of phenolic compounds in water,as their pentafluorobenzoyl derivatives

A sensitive gas chromatographic method for the determination of phenolic compounds in water samples has been developed. The phenols are converted by means of pentafluorobenzoyl chloride to the corresponding acyl derivatives. The procedure, specific for phenolic compounds, is compared with pentafluorobenzylation and was found to be faster and simpler. The method has been applied to industrial waste water.     

Determination of the insecticide diflubenzuron in mushrooms by kinetic method and high-performance liquid chromatographic method

In the present study, a new sensitive and simple kinetic-spectrophotometric method for the determination of the insecticide diflubenzuron [1-(4-chlorophenyl)-3-(2,6-diflubenzoil)urea] is proposed. The method is based on the inhibited effect of diflubenzuron on the oxidation of sulphanilic acid (SA) by hydrogen peroxide in phosphate buffer in presence Cu(II) ion. Diflubenzuron was determined with linear calibration graph in the interval from 0.31 to 3.1 μg mL?1 and from 3.1 to 31.0 μg mL?1. The optimized conditions yielded a theoretical detection limit of 0.18 μg mL?1 corresponding to 0.036 mg kg(-1)mushroom sample based on the 3S(b) criterion. The RSD is 5.03-1.83 % and 2.81-0.71 % for the concentration interval of diflubenzuron 0.31-3.1 μg mL?1 and 3.1-31.0 μg mL?1, respectively. The reaction was followed spectrophotometrically at 370 nm. The kinetic parameters of the reaction are reported, and the rate equations are suggested. The developed procedure was successfully applied to the rapid determination of diflubenzuron in spiked mushroom samples of different mushroom species. The HPLC method was used like a comparative method to verify results.     

Development and validation of a method for analysis of "dioxin-like" PCBs in environmental samples from the steel industry

A method, previously used for determination of 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), has been modified for quantitative analysis of "dioxin-like" polychlorobiphenyls (PCBs) in environmental samples from the steel industry. The existing sample clean-up procedure, involving liquid chromatography on multi-layered silica and Florisil columns, has been extended to include a third chromatography stage on a basic alumina stationary phase. The additional clean-up stage is required for PCB analysis in order to eliminate interferences from relatively large concentrations of saturated cyclic and aliphatic hydrocarbons. Samples were analysed for WHO-12 congeners using high resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS) and standard solutions of the method US EPA 1668A. Replicate analysis of method blanks revealed background contamination for PCBs 118, 105 and 77, which are generally abundant in ambient air. These contaminants were taken into account using a subtraction method. The entire procedure was validated by replicate analysis (N = 3) of a certified reference sediment. The RSD for each WHO-12 congener was below 15%, 13C12-labelled PCB internal standard recoveries were in the range 70-95%. A waste dust sample collected in the electrostatic precipitator of a UK sinter plant was analysed for determination of PCDD/Fs and WHO-12 PCBs and exhibited a PCDD/F I-TEQ of 148.5 +/- 21.2 ngkg(-1) and a WHO-TEQ of 7.2 +/- 1.5 ngkg(-1). WHO-12 congeners contributed only 4.6% to the overall TEQ and PCB 126 was the major congener contributing to the WHO-TEQ (96%). The contribution to the overall TEQ of the waste dust sample was mainly attributed to PCDF followed by PCDD, which accounted for 86.6% and 8.7% to the overall TEQ, respectively.     

自配消解液分光光度法测定污水中的COD

以自配消解液代替ThermoFisher公司AQ4001COD测定系统的专用消解液，比较了自配消解液分光光度法与国家标准重铬酸钾法(GB 11914-1989)测定化学需氧量(COD)的差异。对比试验表明，自配消解液分光光度法测定COD的结果精确度和准确度高，与国家标准方法无显著性差异。自配消解液分光光度法测定水样COD值的相对标准偏差;低量程(30～150 mg/L)为1.38%～2.53%，中量程(0～1 500 mg/L)为0.47%～3.63%，高量程（2 000～15 000 mg/L）为0.17%～3.53%，在国家标准方法测试水样COD值的允许误差范围内。除制革废水外，自配消解液可以代替AQ4001COD测定系统的专用消解液，适用不同量程范围内污水COD的测定。自配消解液分光光度法具有试剂使用量少、速度快、经济、二次污染小等优点，值得在环境科学领域及废水水质监测中推广应用。     

Determination of dithiocarbamate fungicide propineb and its main metabolite propylenethiourea in airborne samples

A simple, rapid and sensitive GC–MS method for the determination of dithiocarbamate fungicide propineb [polymeric zinc propylenebis (dithiocarbamate)] and an improved HPLC procedure for the simultaneous determination of its main metabolite, propylenethiourea, and ethylenethiourea, the main metabolite of all ethylenedithiocarbamates, in airborne samples are described. The method for the analysis of propineb involves the evolution of carbon disulfide (CS₂), under acidic conditions in the presence of stannous chloride, extraction of the generated CS₂ into a layer of isooctane which is then analyzed for CS₂ content by GC–MS in SIM mode. Under the optimum conditions, the retention time of CS₂ was 1.89 min and the total time of chromatographic analysis was 5 min. Recoveries from spiking glass microfibre filters (GF/A) and silica gel filters were 86 ± 7 (n = 9) and 89 ± 4 (n = 9), respectively. The limit of detection is 0.7 ng per filter, which is equivalent to about 0.8–1.0 ng m⁻³ in air. In parallel, an HPLC method with ultraviolet detection is presented for the simultaneous analysis of the metabolites. Separation of the two metabolites was attained in less than 5 min. Recoveries from spiking GF/A and silica gel filters for ethylenethiourea were 100 ± 1 (n = 3) and 98 ± 2 (n = 3), respectively, while for propylenethiourea were 102 ± 1 (n = 3) and 98 ± 1 (n = 3), respectively. The detection limits are about 36–43 and 40–49 ng m⁻³ in air for ethylenethiourea and propylenethiourea, respectively. All the analytes spiked in the filters are proven to be stable for more than one month, at −4 °C.     

Measurement of the pesticide methomyl by modified quartz crystal nanobalance with molecularly imprinted polymer

A simple and cost-effective analysis method based on quartz crystal nanobalance (QCN) coated with a molecularly imprinted polymer (MIP) for measurement of methomyl was investigated. In the first part of this study, a sensitive, selective and reliable quartz crystal nanobalance (QCN) sensor was designed for the selective determination of methomyl in aqueous solutions. In the second part, in order to demonstrate the applicability and performance of the fabricated sensor in the real world situation, it was successfully applied for the determination of methomyl residual in photo catalytic degradation by ZnO powders in aqueous solutions. The fabricated sensor presents a high selectivity and sensitivity (4.56 Hz per mg L^?1) for methomyl and it can be used for determination of methomyl concentration ranged between 1 to 45 mg L^?1. Furthermore, good reproducibility, R.S.D. = 2.14% (n = 5) was observed. To investigate the performance of the sensor, the change in the insecticide concentration during the photocatalytic degradation of methomyl by ZnO was investigated by QCN and UV/Vis spectroscopy. Results obtained from QCN sensor and UV/Vis spectroscopy measurement are in good mutual agreement. So the fabricated sensor may provide an efficient, low cost, easy-to-use method for the in-field evaluation of specific targeted analytes in aqueous solutions which in turn may lead to improved food and water safety.     

Rapid and Sensitive LC/MS/MS Direct Injection Method for the Determination of Trace Level Corexit EC9500A Oil Dispersant in Seawater

A rapid and sensitive liquid chromatography tandem mass spectrometry (LC/MS/MS) method for the determination of trace dioctyl sulfosuccinate (DOSS) concentrations in seawater samples has been established. The method is well suited to aquatic environment impact monitoring following application of the dispersant Corexit EC9500A. Linearity of the method was demonstrated down to 0.05 ng/mL^?1 (0.05 µgL^?1) DOSS in seawater, with a 2.4% relative standard deviation precision for preparation replicates. A US EPA method limit of detection of <0.02 ng/mL^?1 (<0.02 µgL^?1) was calculated and specificity was confirmed by monitoring of two qualifier ions at 291.1 m/z and 227.1 m/z. These transitions were confirmed by QToF analysis to be associated with the DOSS precursor ion at 421.2 m/z. For application to seawater samples and samples containing oil particulates, a practical and repeatable calibration range of 0.5 ng/mL^?1 (0.5 µgL^?1) to 25.0 ng/mL^?1 (25.0 µgL^?1) DOSS is reported. The method was shown to have excellent precision and accuracy, with a consistent ≤1.6% relative standard deviation for system suitability standards at 0.5 ng/mL^?1 (0.5 µgL^?1) and linear weighted (1/x) regression coefficients of determination ≥0.995. The surfactant nature of the analyte is discussed in relation to detection limit and loss of analyte. Speculation of a relationship between DOSS in association or aggregation with divalent cations, such as Ca²⁺ present in salt water and hard water, is suggested. The consequent effects on cell ionic balance and membrane function are discussed.     

Spectrophotometric Determination of Atmospheric Acidity by means of the Displacement of the Equilibrium of Acid-Base Indicators

A method is described for determining acidity by means of the spectrophotometric determination of the displacement of the equilibrium of açid-base indicators. The method is simple, sensitive and free of known interferences. There is no dependence on costly or sophisticated equipment and the results obtained are reliable and reproducible.     

Non-isothermal gaseous exchange between soil and atmosphere

The theoretical and experimental basis of a non-isothermal rotary gas exchange (NRGE) between soil and atmosphere is given. A method of measurement for the NRGE intensity in porous media, including soil, is given and its validity is examined. The global NRGE of selected gases is determined. Relatively high NRGE intensities are found to exist for some gases. The heat transfer determination method is given. An electrical scheme for simulating the NRGE process is also described.     

Spatial distribution of organotins in sediments of lowland river catchments

A method is described for the measurement of nanogram quantities of a range of methyl and butyltin compounds. The method utilises a modified purge and trap/boiling point separation technique for the determination of organotin compounds in sediment samples. A spatial survey of sediment samples within 5 river systems in the East Anglia region of the United Kingdom was undertaken and identified a range of organotin compounds with concentrations of tributyltin (TBT) ranging from <3.9 ng g(-1) up to 1291 ng g(-1). The highest values were found in areas connected with boating activities. Wherever TBT was present, dibutyltin and monobutyltin were most commonly found along with small concentrations of certain methyltins.     

A simple spectrophotometric method for the determination of cobalt in industrial, environmental, biological and soil samples using bis(salicylaldehyde)orthophenylenediamine

Bis(salicylaldehyde)orthophenylenediamine (BSOPD) has been proposed as new analytical reagent for the direct non-extractive spectrophotometric determination of cobalt. It reacts with cobalt in slightly acidic (0.0002-0.001 M H(2)SO(4)) 50% 1,4-dioxanic medium to form a red-orange chelate with a molar ratio 1:1. The reaction is instantaneous and the maximum absorbance was obtained at 458 nm and remains constant for over 24h. The average molar absorption coefficient and Sandell's sensitivity were found to be 1.109 x 10(4)l mol(-1)cm(-1) and 20 ng cm(-2) of Co(II), respectively. Linear calibration graph was obtained for 0.1-15 mg l(-1) of Co(II) with a correlation coefficient value of 0.995 for Co-BSOPD complex. Large excess of 44 cations, anions and complexing agents do not interfere in the determination. The method was successfully used in the determination of cobalt(II) from synthetic mixture and certified reference materials for the purpose of validating the method and the results of analyses were found to be excellent agreement with those of actual values. This developed method was also used for determination of cobalt in some environmental waters (potable and polluted), biological (blood and urine) and soil samples and solution containing both cobalt(II) and cobalt(III). The results of the proposed method for biological samples were comparable with AAS and were found to be in good agreement. The method has high precision and accuracy (s=+/-0.01 for 0.5 mg l(-1)).     

Determination of the insecticide diflubenzuron in mushrooms by kinetic method and high-performance liquid chromatographic method

In the present study, a new sensitive and simple kinetic-spectrophotometric method for the determination of the insecticide diflubenzuron [1-(4-chlorophenyl)-3-(2,6-diflubenzoil)urea] is proposed. The method is based on the inhibited effect of diflubenzuron on the oxidation of sulphanilic acid (SA) by hydrogen peroxide in phosphate buffer in presence Cu(II) ion. Diflubenzuron was determined with linear calibration graph in the interval from 0.31 to 3.1 μg mL^?1 and from 3.1 to 31.0 μg mL^?1. The optimized conditions yielded a theoretical detection limit of 0.18 μg mL^?1corresponding to 0.036 mg Kg^?1mushroom sample based on the 3S_b criterion. The RSD is 5.03–1.83 % and 2.81–0.71 % for the concentration interval of diflubenzuron 0.31–3.1 μg mL^?1and 3.1–31.0 μg mL^?1, respectively. The reaction was followed spectrophotometrically at 370 nm. The kinetic parameters of the reaction are reported, and the rate equations are suggested. The developed procedure was successfully applied to the rapid determination of diflubenzuron in spiked mushroom samples of different mushroom species. The HPLC method was used like a comparative method to verify results.     

A Portable Fiber-Optic Chemical Device for the Quantitative Determination of Carbon Monoxide from Automobile Exhaust Emissions

ABSTRACT

A colorimetxic method for the quantitative determination of CO by diffuse reflectance is described. This method is based on the reduction by CO of Mo (VI) from the indicator reagent molybdosilicic acid (H₈Si[Mo₂O₇]₆). The reduction yielded a change of color from clear yellow to dark green on white disk filter chart paper wetted with reagent indicator solution. The gaseous mixture containing CO was forced to pass through this chart paper, initiating the reaction. The intensity of the color produced, measured by diffuse reflectance, was proportional to the CO concentration present in exhaust gases in the range from 0.02 to 12% volume/volume (v/v). A 650-nm light-emitting diode was used as a light source. A two-fiber-optic system carried the light from the source to the detection system, which was composed of a photodiode, an amplification circuit, and a digital display. The method was applied with success in field measurements for automobiles in the Otto cycle. In a previous paper, this method was used for the quantitative determination of exhaust emissions from diesel-fueled vehicles.¹     

电热蚊香片益多克含量的气相色谱测定

叙述了采用气相色谱法,以ＦＩＤ检测器和内标法定量测定电热蚊香片中益多克的含量。方法的变异系数为１．１％,回收率达到９８．７％,线性相关系数为．９９９１。该方法适用电热蚊香片中益多克的含量测定。     

Comparison of naphthalene bioavailability determined by whole-cell biosensing and availability determined by extraction with Tenax

A rapid biological method for the determination of the bioavailability of naphthalene was developed and its value as an alternative to extraction-based chemical approaches demonstrated. Genetically engineered whole-cell biosensors are used to determine bioavailable naphthalene and their responses compared with results from Tenax extraction and chemical analysis. Results show a 1:1 correlation between biosensor results and chemical analyses for naphthalene-contaminated model materials and sediments, but the biosensor assay is much faster. This work demonstrates that biosensor technology can perform as well as standard chemical methods, though with some advantages including the inherent biological relevance of the response, rapid response time, and potential for field deployment. A survey of results from this work and the literature shows that bioavailability under non-equilibrium conditions nonetheless correlates well with K_oc or K_d. A rationale is provided wherein chemical resistance is speculated to be operative.     

GC/MS法测定润滑油基础油中多环芳烃

对润滑油基础油中多环芳烃的气相色谱/质谱(GC/MS)测定方法进行了研究,探讨了样品的提取,固相萃取柱净化等前处理方法,同时也对仪器测定条件进行了优化.结果表明,在检测润滑油基础油中多环芳烃时,经优化的GC/MS法的加标回收率和精密度均达到较满意的水平.