A review of analytical methods for the determination of trichloroethylene and its major metabolites chloral hydrate, trichloroacetic acid and dichloroacetic acid

Trichloroethylene (TCE) and some of its metabolites are potentially carcinogenic compounds that the general population is commonly exposed to in drinking water. Concentrations of TCE, dichloroacetic acid (DCA) and trichloroacetic acid (TCA) given to laboratory animals in cancer bioassays are high, whereas drinking water levels of the compounds are very low. It is not clear whether the trace amounts of TCE, DCA and TCA in drinking water pose a cancer risk to humans. The accuracy of pharmacokinetic studies relies on the analytical method from which blood and tissue concentration data are obtained. Models that extrapolate cancer risks of TCE and its metabolites from laboratory animals to humans, in turn, rely on the results of pharmacokinetic studies. Therefore, it is essential to have reliable analytical methods for the analysis of TCE and its metabolites. This paper reviews the methods currently in the literature for the analysis of TCE, DCA, TCA and, to a lesser extent, chloral hydrate (CH). Additional aspects of analytical methods such as method validation, species preservation and future directions in the analysis of TCE and its metabolites are also discussed.     

Flow injection microbial trichloroethylene sensor

A flow type microbial biosensor for direct measurement of trichloroethylene (TCE) was developed. The unique features of this novel microbial sensor were the use of the TCE degrading bacterium Pseudomonas aeruginosa JI104, the electrical detection of the chloride ion released by microbial degradation, and flow cell made of glass. Glass cell was used in order to suppress adsorption of TCE and made a closed reaction cell. Vaporization of TCE during the measurement was prevented using closed flow cell. The performance of the sensor was evaluated from following aspects; such as pH of the carrier solution, amount of the immobilized microbe, flow rate and injection volume. The sensor signals were linearly proportional to the concentration of TCE in the range from 0.03 to 2 mgl(-1), which is suitable for the determination of suspected samples to be drinkable water or not. The sensor performance was checked on the real sample, and this system showed good response in ground water, indicating its applicability for the on line monitoring at TCE contaminated areas or hazardous sites.     

A new bacterial biosensor for trichloroethylene detection based on a three-dimensional carbon nanotubes bioarchitecture

Trichloroethylene (TCE), a suspected human carcinogen, is one of the most common volatile groundwater contaminants. Many different methodologies have already been developed for the determination of TCE and its degradation products in water, but most of them are costly, time-consuming and require well-trained operators. In this work, a fast, sensitive and miniaturised whole cell conductometric biosensor was developed for the determination of trichloroethylene. The biosensor assembly was prepared by immobilising Pseudomonas putida F1 bacteria (PpF1) at the surface of gold interdigitated microelectrodes through a three-dimensional alkanethiol self-assembly monolayer/carbon nanotube architecture functionalised with Pseudomonas antibodies. The biosensor response was linear from 0.07 to 100 μM of TCE (9–13,100 μg L⁻¹). No significant loss of the enzymatic activity was observed after 5 weeks of storage at 4 °C in the M457 pH 7 defined medium (two or three measurements per week). Ninety-two per cent of the initial signal still remained after 7 weeks. The biosensor response to TCE was not significantly affected by cis-1,2-dichloroethylene and vinyl chloride and, in a limited way, by phenol. Toluene was the major interference found. The bacterial biosensor was successfully applied to the determination of TCE in spiked groundwater samples and in six water samples collected in an urban industrial site contaminated with TCE. Gas chromatography–mass spectrometric analysis of these samples confirmed the biosensor measurements.     

The bitterness intensity of clarithromycin evaluated by a taste sensor

The purpose of this study was to evaluate the ability of a quantitative prediction method using a taste sensor to determine the bitterness of clarithromycin powder suspensions of various concentrations and of a commercial clarithromycin dry syrup product (Clarith dry syrup, Taisho Pharmaceutical Co., Ltd., Tokyo) containing aminoalkyl methacrylate polymer as a taste-masker. The bitterness of the clarithromycin dry syrup product dissolved in various beverages was also evaluated in gustatory sensation tests and using the taste sensor. In the sensor measurements, three variables were used to predict bitterness in single and multiple regression analysis: relative sensor output (R), the change of membrane potential caused by adsorption (CPA), and CPA/R ratio. The CPA values for channel 3 of the sensor predicted well the bitterness of clarithromycin powder suspensions and their filtered solutions. For Clarith dry syrup, the sensor output was small, suggesting that aminoalkyl methacrylate polymer was successful in almost complete masking of the bitter taste of the dry syrup product. When the bitterness intensities of mixtures of 1 g of Clarith dry syrup with 25 ml of water, coffee, tea, green tea, cocoa, milk, and a sports drink were examined, a good correlation was obtained between the results from human taste tests and the predicted values calculated on the basis of multiple regression analysis using CPA data from channel 4, and the CPA/R ratio from channel 3 of the taste sensor (r(2)=0.963, p<0.005). Co-administration of 1 g of Clarith dry syrup with an acidic sports drink was found to be the most bitter using either method.     

Influence of relative humidity in sensing halogenated hydrocarbons with Reflectometric Interference Spectroscopy (RIfS)

For stand-alone sensor systems apart from defined laboratory circumstances sensors are required, which show a high stability against perturbing environmental influences like the relative humidity (r.h.). We present a portable sensor system, which is capable to quantify tetrachloroethene (TCE) in humid air. The system works highly reproducible and shows only negligible cross-sensitivity towards relative humidity. This allows a single calibration valid from 0 to 80% r.h.. Therefore, referencing with an extra sensor for humidity is not necessary. Binary mixtures of TCE and freone R113 were quantified for 0 and 40% r.h. with a root mean square error of prediction of approximately 3% with respect to the maximum concentration of TCE and R113. The sensitive elements used in the experiments consisted of thin polymer films on glass substrates. The measurements were performed with the optical measurement technique RIfS (Reflectometric Interference Spectroscopy).     

Analysis of dichloroacetic acid in rat blood and tissues by hydrophilic interaction liquid chromatography with tandem mass spectrometry

Dichloroacetic acid (DCA) is a compound found in chlorinated drinking water. In addition, the compound is a metabolite of several halogenated solvents, including trichloroethylene (TCE) and perchloroethylene (PCE). Exposure to DCA is of concern because high doses of the compound have been shown to cause cancer in laboratory animals. Dosages of TCE administered to animals in cancer studies are designed to elicit maximal DCA formation in vivo, whereas levels of DCA to which individuals are exposed in drinking water are very low. Analysis of DCA in biological samples has been quite challenging. Derivatizing reagents commonly used to convert DCA into a more volatile form for analysis by gas chromatography (GC) have been found to convert trichloroacetic acid (TCA), a major metabolite of TCE and PCE, into DCA. High-performance liquid chromatography (HPLC) analysis does not require derivatization of DCA and can thus avoid this problem. However, the most popular stationary phases in HPLC columns do not retain small, polar compounds such as DCA well. The liquid chromatography/tandem mass spectrometry (LC/MS/MS) method described in this paper uses hydrophilic interaction liquid chromatography (HILIC), a type of chromatography that is able to retain these small, polar compounds. Method validation was performed using the United States Food and Drug Administration (USFDA) and International Conference on Harmonziation (ICH) Guidance for Industry: Bioanalytical Method Validation as a guide. Levels of DCA found in rats dosed with 2 g/kg TCE were 17.2 ng/mL (liver), 262.4 ng/mL (kidney), 175.1 ng/mL (lung), and 39.5 ng/mL (blood).     

Optimization, validation and application of a method for the determination of trichloroethylene in rat plasma by headspace solid-phase microextraction gas chromatography mass spectrometry

Trichloroethylene (TCE) is a small halogenated compound that has been used extensively as a metal degreaser and a solvent for the past 100 years. As a result of its widespread use, TCE can be found in the groundwater of about one-third of the hazardous waste sites on the United States Environmental Protection Agency's National Priorities List. Human exposure to TCE in the environmental media is of concern because TCE has been found to be carcinogenic in laboratory animals. This paper describes the development and validation of a HS-SPME-GC/MS method for determination of TCE in rat plasma. The effects of different parameters such as sample volume, extraction and desorption conditions, fiber positions and salt addition were investigated and optimized. The method is rapid, simple, sensitive and requires a very small sample volume. The lower limit of quantitation was 0.25 ng/mL and correlation coefficient (r(2)) values for the linear range of 0.25-100 ng/mL were 0.996 or greater. The precision and accuracy for intra-day and inter-day were better than 8.0%. This validated method was successfully applied to study the toxicokinetic behavior of TCE following low levels of oral administration. Copyright (c) 2008 John Wiley & Sons, Ltd.     

Photooxidation of aqueous trichloroethylene using a buoyant photocatalyst with reaction progress monitored via micro-headspace GC/MS

Although photooxidation has previously been shown to be successful in removing organic contaminants from water, methods combining the rapid photooxidation of the desired contaminant with easy catalyst manipulation and removal are few and far between. In the absence of an easy means of catalyst removal, the photooxidation process becomes more costly and time consuming, and photocatalysis cannot be employed as an in situ method for the remediation of aqueous organic contaminants. In this study, the photocatalyst was added to an aqueous trichloroethylene (TCE) solution in the form of TiO₂-coated buoyant microspheres. The solution, placed in a flow-cell photoreactor along with the buoyant catalyst, was irradiated with a UV-filtered Xenon light source. Limited sample sizes necessitated the development of a low-cost headspace GC/MS analysis method, utilizing a standard direct-injection autosampler. This analytical technique aptly monitored reaction progress and indicated that aqueous TCE concentration decreases by nearly 90% in the first hour of irradiation. Subsequent solvent extraction GC/MS analysis indicated that the TCE is initially sorbed by the photocatalyst spheres, but as irradiation continued, TCE is removed from the catalyst spheres surfaces. During the course of irradiation, the expected TCE mineralization product hydrochloric acid appeared, as indicated by a decrease in pH and ion chromatography analysis. The microsphere-born catalyst was easily removed from the treated solution by filtration. Thus, it is possible that a method for effective, low-cost in situ photooxidation of aqueous organic contaminants will be realized in the near future.     

Influence of relative humidity in sensing halogenated hydrocarbons with Reflectometric Interference Spectroscopy (RIfS)

For stand-alone sensor systems apart from defined laboratory circumstances sensors are required, which show a high stability against perturbing environmental influences like the relative humidity (r.h.). We present a portable sensor system, which is capable to quantify tetrachloroethene (TCE) in humid air. The system works highly reproducible and shows only negligible cross-sensitivity towards relative humidity. This allows a single calibration valid from 0 to 80% r.h.. Therefore, referencing with an extra sensor for humidity is not necessary. Binary mixtures of TCE and freone R113 were quantified for 0 and 40% r.h. with a root mean square error of prediction of approximately 3% with respect to the maximum concentration of TCE and R113. The sensitive elements used in the experiments consisted of thin polymer films on glass substrates. The measurements were performed with the optical measurement technique RIfS (Reflectometric Interference Spectroscopy). Received: 29 May 1998 / Revised: 4 August 1998 / Accepted: 8 August 1998     

Interference studies on a PVC-matrix membrane calcium ion-selective electrode based on calcium bis-di[4-(1,1,3,3-tetramethylbutyl)phenyl] phosphate as sensor and tri-n-pentyl phosphate as solvent mediator

Interference potentials, E(M), defined as the difference between the observed potential and the potential calculated assuming that there is no interference, have been determined, and their fit to the equation E(M) = -(RT/F) 1n [1 + K(M)a(B)/(a(Ca))1 2 (z(B)) discussed for a PVC-matrix membrane calcium ion-selective electrode based on calcium bis-di[4-(1,1,3,3-tetramethylbutyl)phenyl]phosphate as sensor with tri-n-pentyl phosphate as solvent mediator in mixed solutions of CaCl(2)BCl(x), where B = Li, Na, K, Mg, Zn or Cu, at total ionic strengths of 0.2, 0.4 and 0.6. Generally, K(M) for the alkali metal ions is considerably less for this electrode than for a comparison electrode based on Orion 92-20-02 liquid ion-exchanger in PVC. Occasionally, the data do not fit the equation. Thus, particularly for the bivalent ions, although the plots of exp[-E(M)F/RT] vs. a(B)/(a(Ca))1 2 (z(B)) are usually linear, they frequently do not intercept the ordinate at 1.00 and/or may give negative slopes and hence negative K(M) values.     

On the possible catalysis by single water molecules of gas-phase hydrogen abstraction reactions by OH radicals

The gas phase hydrogen abstraction reaction between OH and CY(2)XH, where X = H, F, OH, or NH(2) and Y = H, CH(3) or F, in the absence and presence of a single water molecule is investigated using both density function theory, B3LYP, and explicitly correlated coupled cluster theory, CCSD(T)-F12. We find that a single water molecule could have a catalytic effect at low temperatures possible in laboratory experiments, but does not seem to catalyze these reactions at 298 K, and will not play a role under relevant atmospheric conditions.     

Monitoring and evaluation of dechlorination processes using compound-specific chlorine isotope analysis

A simple, quick and sensitive method for the compound-specific stable chlorine isotope analysis of chlorinated solvents by conventional quadrupole gas chromatography/mass spectrometry (GC/MS) is presented. With this method, compound-specific stable chlorine isotope ratios of typical chlorinated solvents like tetrachloroethene (PCE) and trichloroethene (TCE) can be determined quantitatively within 30 min by direct injection. The chlorine isotope ratios of target substances are calculated from the peak areas of several selected molecular ions and fragment ions of the substances, using a set of unique mathematical equations. The precision of the method was demonstrated through reproducibility tests. An internal precision of +/-0.4 per thousand to +/-1.1 per thousand was obtained when analyzing PCE and TCE in the 10-1000 pmol range. The validity of the method was further demonstrated by determining the chlorine isotopic fractionation factor during the reductive dechlorination of TCE in a batch experiment using zero-valent iron. The chlorine isotopic fractionation factor was calculated as 0.9976 +/- 0.0011 with a correlation coefficient of 0.9469 (n = 38). The high correlation coefficient indicates that compound-specific stable chlorine isotope analysis can be performed with sufficient accuracy using conventional quadrupole GC/MS when significant fractionation takes place during a reaction. For the first time, the chlorine isotope fractionation factor of TCE during an abiotic anaerobic dechlorination process was determined using quadrupole GC/MS, without offline sample preparation.     

X射线荧光光谱法测定钠冰晶石的主要化学成分

选用国家标准样品和高纯物质配制实验用标准样品,采用混合熔剂(67%Li2B4O7+33%LiBO2)熔融制样,使用X射线荧光光谱法测定钠冰晶石中SiO2、Fe2O3、MgO、CaO、K2O、TiO2、P2O5、Na、F、Al各组分的含量,实验结果表明,各组分的相对标准偏差(RSD)在0.57%~6.5%,与第三方实验室对比测定结果表明,方法可以满足工厂检测要求。     

Trichloroethylene Combustion in a Submerged Thermal Plasma: Results and Chemical Kinetics Model

This work deals with incineration of organic liquid wastes using an oxygen thermal plasma jet, submerged in water. The results presented here concern incineration of trichloroethylene (TCE). During a trial run, the CO₂ and CO content in the exhaust gas is continuously measured; samples taken periodically from the solution are analyzed by appropriate methods: total organic carbon and chlorine content are measured. Process efficiency during tests with a few L/h of TCE is given by the mineralization rate. The trapping rate of chlorine as HCl is near 100 %. The TCE destruction and removal efficiency, measured by MS/GC, is better than 99.9999 %. A simplified kinetic model of gas quenching was constructed from a single-phase plug-flow reactor model taking into account 14 species and 34 reactions. It satisfies the requirements of heat balance and major components analysis, and reveals the major role of the OH radical on the concentrations of CO as well as HCl and/or Cl₂ in the off-gas stream.     

Evaluation of semiquantitative analysis mode in ICP-MS

Semiquantitative analysis mode in inductively coupled plasma mass spectrometry (ICP-MS) has been popularly used for fast screening purposes. Although the benefit of it has been studied by many researchers, its performance of application in real-world routine analyses has not been reported.

In this study, we evaluated the reliability of semiquantitative analysis mode through inter-laboratory comparison using two different ICP-MS systems with one multi-element calibration standard. The suitability of semiquantitative analysis mode in routine analysis laboratory was demonstrated by evaluating its application in different laboratories and in real production laboratory practices. Twenty one elements were measured, namely, Be, B, Al, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, As, Sr, Mo, Ag, Cd, Sn, Sb, Ba, Tl, and Pb in various fresh water reference samples. Good results concerning accuracy (relative percentage error within 10%) and reproducibility (relative standard deviation lower than 5%) were obtained in more than 90% analyzed samples at concentrations equal to or greater than 10 times the detection limit (DL). Semiquantitative analysis mode also enabled the determination of elements that are not present in the calibration standard. The results demonstrated the potential of semiquantitative analysis mode as a reliable approach in routine laboratory determination of simple matrices, where high throughput and cost-effectiveness are desired, as well as in emergency situations where speed of analysis is critical and quite often limited sample information is available.     

一维链状冠醚配合物[K(B18-C-6)]_2[M(SCN)_4](M=Pd,Pt)的合成与结构

合成了苯并18-冠-6（B18-C-6）与K_2[Pd(SCN)_4]生成的配合物[K（B18-C-6 ）]_(12) [Pd(SCN)_4] (1), [K(B18-C-6)]_2[Pt(SCN)_4] (2)和[K(B18-C-6)]_2 [Pt(SCN)_4]·C_2H_4Cl_2 (3),并通过元素分析、红外光谱、单晶X射线衍射进行 了表征。1和2为单斜晶系,空间群P2_l/n,晶体学数据：1, a = 1.00970(17) nm, b = 1.3157(2) nm, c = 1.7303(3) nm, β = 94.841(2)°, V = 2.2852(7) nm~3, Z = 2, F(000) = 1136, R_1 = 0.0257。3为三斜晶系,空间群P1,晶体学 数据：a = 0.95914(18) nm, b = 1.2137(2) nm, c = 2313(2) nm, α = 63.693 (2)°, β = 76.293(2)°, γ-1.2406(4) n~3, Z = 1 F(000)618,R_1 = 0.0366 。在固态,三个配合物相邻的两个[K（B18-C-6）]~+基团通过冠醚氧化原子与钾的 子的相边接而形成一维链状结构。     

A new method for evaluating the bitterness of medicines by semi-continuous measurement of adsorption using a taste sensor

We describe a new method for the evaluation of the bitterness of medicines by semi-continuous measurement of adsorption using a multichannel taste sensor or 'electric tongue'. The bitterness of 10 basic medicines was evaluated by both the taste sensor and in human gustatory sensation tests with 11 volunteers. The sensor part of the taste sensor consists of eight electrodes made of lipid/polymer membranes. Three variables were obtained from the taste sensor data: sensor output (S), the change of membrane potential caused by adsorption, corresponding to aftertaste (C), and the ratio C/S. These variables were used to predict an estimated bitterness score in multiple regression analysis. Semi-continuous measurement of C (every 30 s up to 150 s) was adopted as an additional explanatory variable, and the attenuation rate of C was defined as C'. These data were also subjected to multiple regression analysis. The correlation coefficient (r) estimated for the bitterness score predicted by the taste sensor, using C' for channel 2 and C/S for channel 4, and the score obtained by human gustatory sensation, was 0.824. This value was greater than that obtained using C/S for both channels 2 and 4 (0.734). The method described in the present study seems to offer good predictability for the evaluation of bitterness.     

碳氟键均裂解离能的密度泛函理论研究

运用6种密度泛函方法(B3LYP, B3P86, B3PW91, PBE1PBE, MPW1B95, MPW1K)对15个含氟有机化合物的碳氟键均裂解离能进行理论计算, 得到的理论值与实验值比较, 发现B3P86方法用于碳氟键均裂解离能的计算相对可靠. 使用验证后的理论方法对含氟杂环有机化合物和卤氟烃中的碳氟键均裂解离能进行了预测和分析, 并进一步讨论了α-取代基效应以及Hammett型取代基效应对碳氟键均裂解离能的影响.     

Use of spatiotemporal response information from sorption-based sensor arrays to identify and quantify the composition of analyte mixtures

Linear sensor arrays made from small molecule/carbon black composite chemiresistors placed in a low-headspace volume chamber, with vapor delivered at low flow rates, allowed for the extraction of new chemical information that significantly increased the ability of the sensor arrays to identify vapor mixture components and to quantify their concentrations. Each sensor sorbed vapors from the gas stream and, thereby, as in gas chromatography, separated species having high vapor pressures from species having low vapor pressures. Instead of producing only equilibrium-based sensor responses that were representative of the thermodynamic equilibrium partitioning of analyte between each sensor and the initial vapor phase, the sensor responses varied depending on the position of the sensor in the chamber and the time since the beginning of the analyte exposure. The concomitant spatiotemporal (ST) sensor array response therefore provided information that was a function of time, as well as of the position of the sensor in the chamber. The responses to pure analytes and to multicomponent analyte mixtures comprised of hexane, decane, ethyl acetate, chlorobenzene, ethanol, and/or butanol were recorded along each of the sensor arrays. Use of a non-negative least-squares (NNLS) method for analysis of the ST data enabled the correct identification and quantification of the composition of two-, three-, four-, and five-component mixtures from arrays using only four chemically different sorbent films. In contrast, when traditional time- and position-independent sensor response information was used, these same mixtures could not be identified or quantified robustly. The work has also demonstrated that, for ST data, NNLS yielded significantly better results than analyses using extended disjoint principal components modeling. The ability to correctly identify and quantify constituent components of vapor mixtures through the use of such ST information significantly expands the capabilities of such broadly cross-reactive arrays of sensors.