Determination of benzene series compounds and chlorobenzenes in water sample by static headspace gas chromatography with flame ionization detection

A simple, efficient, solvent‐free, and readily commercially available approach for the determination of eight benzene series compounds and 12 chlorobenzenes in water samples using the static headspace sampling and gas chromatography with flame ionization detection has been described in this paper. The proposed static headspace sampling method was initially optimized, and the optimum experimental conditions explored were 10 mL water sample containing 20% w/v sodium chloride placed in a 20 mL vial and stirred at 70°C for 43 min. The linearity of the method ranged from 1 to 200 μg/L for 20 analytes, with correlation coefficients ranging between 0.9962 and 0.9994. The limits of detection were in the μg/L level, ranging between 0.15 and 0.4 μg/L. The relative recoveries of spiked benzene series and chlorobenzenes with external calibration method at different concentration levels in pure, tap, and sea water samples were 84–113, 78–115 and 85–119%, respectively, with relative standard deviations of 3.8–6.8, 4.1–5.8, and 4.8–5.4% (n = 5), respectively. That this method can be successfully applied to the determination of benzene series compounds and chlorobenzenes in pure, tap, and sea water samples, simultaneously.     

Determination of volatile chlorinated hydrocarbons in water samples by static headspace gas chromatography with electron capture detection

A simple, efficient, solvent‐free, and commercial readily available approach for determination of five volatile chlorinated hydrocarbons in water samples using the static headspace sampling and gas chromatography with electron capture detection has been described. The proposed static headspace sampling method was initially optimized and the optimum experimental conditions found were 10 mL water sample containing 20% w/v sodium chloride placed in a 20 mL vial and stirred at 50ºC for 20 min. The linearity of the method was in the range of 1.2–240 μg/L for dichloromethane, 0.2–40 μg/L for trichloromethane, 0.005–1 μg/L for perchloromethane, 0.025–5 μg/L for trichloroethylene, and 0.01–2 μg/L for perchloroethylene, with coefficients of determination ranging between 0.9979 and 0.9990. The limits of detection were in the low μg/L level, ranging between 0.001 and 0.3 μg/L. The relative recoveries of spiked five volatile chlorinated hydrocarbons with external calibration method at different concentration levels in pure, tap, sea water of Jiaojiang Estuary, and sea water of waters of Xiaomendao were in the range of 91–116, 96–105, 86–112, and 80–111%, respectively, and with relative standard deviations of 1.9–3.6, 2.3–3.5, 1.5–2.7, and 2.3–3.7% (n = 5), respectively. The performance of the proposed method was compared with traditional liquid–liquid extraction on the real water samples (i.e., pure, tap, and sea water, etc.) and comparable efficiencies were obtained. It is concluded that this method can be successfully applied for the determination of volatile chlorinated hydrocarbons in different water samples.     

Trace analysis of chlorobenzenes in water samples using headspace solvent microextraction and gas chromatography/electron capture detection

In the present work, a rapid method for the extraction and determination of chlorobenzenes (CBs) such as monochlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene and 1,2,4-trichlorobenzene in water samples using the headspace solvent microextraction (HSME) and gas chromatography/electron capture detector (ECD) has been described. A microdrop of the dodecane containing monobromobenzene (internal standard) was used as extracting solvent in this investigation. The analytes were extracted by suspending a 2.5 μl extraction drop directly from the tip of a microsyringe fixed above an extraction vial with a septum in a way that the needle passed through the septum and the needle tip appeared above the surface of the solution. After the extraction was finished, the drop was retracted back into the needle and injected directly into a GC column. Optimization of experimental conditions such as nature of the extracting solvent, microdrop and sample temperatures, stirring rate, microdrop and sample volumes, the ionic strength and extraction time were investigated. The optimized conditions were as follows: dodecane as the extracting solvent, the extraction temperature, 45 °C; the sodium chloride concentration, 2 M; the extraction time, 5.0 min; the stirring rate, 500 rpm; the drop volume, 2.5 μl; the sample volume, 7 ml; the microsyringe needle temperature, 0.0 °C. The limit of detection (LOD) ranged from 0.1 μg/l (for 1,3-dichlorobenzene) to 3.0 μg/l (for 1,4-dichlorobenzene) and linear range of 0.5–3.0 μg/l for 1,2-dichlorobenzene, 1,3-dichlorobenzene and from 5.0 to 20.0 μg/l for monochlorobenzene and from 5.0 to 30 μg/l for 1,4-dichlorobenzene. The relative standard deviations (R.S.D.) for most of CBs at the 5 μg/l level were below 10%. The optimized procedure was successfully applied to the extraction and determination of CBs in different water samples.     

Part-per-trillion determination of chlorobenzenes in water using dispersive liquid-liquid microextraction combined gas chromatography-electron capture detection

In this study, a simple, rapid and efficient method, dispersive liquid-liquid microextraction (DLLME) combined gas chromatography-electron capture detection (GC-ECD), for the determination of chlorobenzenes (CBs) in water samples, has been described. This method involves the use of an appropriate mixture of extraction solvent (9.5 μl chlorobenzene) and disperser solvent (0.50 ml acetone) for the formation of cloudy solution in 5.00 ml aqueous sample containing analytes. After extraction, phase separation was performed by centrifugation and the enriched analytes in sedimented phase were determined by gas chromatography-electron capture detection (GC-ECD). Our simple conditions were conducted at room temperature with no stiring and no salt addition in order to minimize sample preparation steps. Parameters such as the kind and volume of extraction solvent, the kind and volume of disperser solvent, extraction time and salt effect, were studied and optimized. The method exhibited enrichment factors and recoveries ranging from 711 to 813 and 71.1 to 81.3%, respectively, within very short extraction time. The linearity of the method ranged from 0.05 to 100 μg l⁻¹ for dichlorobenzene isomers (DCB), 0.002-20 μg l⁻¹ for trichlorobenzene (TCB) and tetrachlorobenzene (TeCB) isomers and from 0.001 to 4 μg l⁻¹ for pentachlorobenzene (PeCB) and hexachlorobenzene (HCB). The limit of detection was in the low μg l⁻¹ level, ranging between 0.0005 and 0.05 μg l⁻¹. The relative standard deviations (R.S.D.s) for the concentration of DCB isomers, 5.00 μg l⁻¹, TCB and TeCB isomers, 0.500 μg l⁻¹, PeCB and HCB 0.100 μg l⁻¹ in water by using the internal standard were in the range of 0.52-2.8% (n = 5) and without the internal standard were in the range of 4.6-6.0% (n = 5). The relative recoveries of spiked CBs at different levels of chlorobenzene isomers in tap, well and river water samples were 109-121%, 105-113% and 87-120%, respectively. It is concluded that this method can be successfully applied for the determination of CBs in tap, river and well water samples.     

Static headspace and purge-and-trap gas chromatography for epichlorohydrin determination in drinking water

Epichlorohydrin (ECH) can enter drinking-water supplies due to leaching from epoxy resins in contact with water and/or through the use of flocculating water treatment agents. Potential human exposure from drinking waters poses a particular concern on account of toxicological studies showing severe acute and long-term toxic effects of ECH. Recently a parametric value of 0.1 μg/L for ECH in drinking water has been established by European Union.A few methods for ECH determination in water are available. However, they usually adopt cumbersome procedures for sample preparation and provide sensitivity not matching the EU criteria for water monitoring purposes.In this study we investigated the analytical performance of gas extraction techniques, such as static headspace (HS) and purge and trap (P&T), coupled to gas chromatography (GC) with an electron capture detector (GC-ECD) for the determination of ECH in drinking water. The influence of different parameters affecting the analytical response was studied in details in order to enhance the method sensitivity, thus fulfilling the regulatory requirements.The P&T GC-ECD method was proved capable of determining ECH in water for human consumption at a detection limit of 0.01 μg/L fully complying the regulatory levels. On the contrary, the HS GC-ECD method is far less sensitive (LOD≅40 μg/L) than the previous cited method. The P&T GC-ECD method is simple, rapid, automated, safe for operators and does not require large sample volumes. Therefore, it is useful for routine laboratory activities both for control and research actions.     

On-line determination of organochlorine pesticides in water by solid-phase microextraction and gas chromatography with electron capture detection

This paper describes the extraction of 20 organochlorine pesticides (OCPs) from water samples using solid-phase microextraction (SPME). Three fused-silica fibers coated or bonded with polydimethylsiloxane (PDMS) of different film thicknesses (20-, 30-, and 100-μm) were evaluated. The extraction time, the effects of stirring and addition of NaCl to the aqueous sample, the linear range and the precision of this technique, and the effect of carryover were examined for 20 analytes and are presented here. A comparison with results using conventional liquid-liquid extraction demonstrate that the SPME technique is well suited as a fast screening technique for OCPs in water samples.     

Phenyl‐functionalized silica‐coated magnetic nanoparticles for the extraction of chlorobenzenes,and their determination by GC‐electron capture detection

We have prepared a solid phase for the extraction of chlorobenzenes (CBs) by coating magnetic (Fe₃O₄) nanoparticles with silica via a sol‐gel process using a mixture of tetraethoxysilane and triethoxyphenylsilane. The nanoparticles were characterized by SEM, energy‐dispersive spectroscopy, and X‐ray diffractometry. The nanoparticles were used for the extraction of 1,4‐dichlorobenzene (1,4‐DCB), 1,2,3‐trichlorobenzene (1,2,3‐TCB), 1,2,4‐trichlorobenzene (1,2,4‐TCB), and 1,2,3,4‐tetrachlorobenzene (1,2,3,4‐TeCB) from water, followed by their determination by GC‐electron capture detection. Under optimal conditions, enrichment factors ranging from 220 to 360 were obtained. All determination coefficients (r²) are >0.99, and linear response is found in range 0.025–1.5 μg/L (at the lower end), and 6–120 μg/L (at the higher end). Detection limits are 6, 10, 11, and 500 ng/L for 1,2,3,4‐TeCB, 1,2,4‐TCB, 1,2,3‐TCB, and 1,4‐DCB, respectively. All RSDs are <6% (for n = 5). The method was successfully applied to the determination of CBs in environmental water samples.     

Derivatization and determination of arsenic in marine samples by gas chromatography with electron capture detection

Summary Arsenic in marine samples was determined by gas chromatography with electron capture detection after derivatization with 2,3-dimercaptopropanol. Biological tissues and sediments were analyzed after acid decomposition. For sea water, arsenic was preconcentrated by coprecipitation with hydrous iron (III) oxide. The results obtained by this approach compare favourably with the certified values of the reference materials analyzed. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984     

气相色谱-电子捕获检测法测定海水中十氯酮残留

通过考察提取溶剂、毛细管柱、净化条件及共溶出干扰物等因素对十氯酮测定的影响,建立了二氯甲烷液-液富集萃取、硫酸净化分离、气相色谱法(GC)-电子捕获检测器(ECD)测定海水介质中有机氯农药类持久性有机污染物十氯酮残留分析方法。1 L海水经50 mL二氯甲烷萃取富集,浓缩后采用硫酸净化,以1%(体积分数)甲醇/正己烷混合溶液转移定容后,采用DB-5非极性毛细管柱进行GC分离,电子捕获检测器可测定其中十氯酮的含量;该方法采用外标法定量,在5～100 μg/L范围内呈线性,线性相关系数为0.9989。低、中、高3个浓度水平的平均加标回收率为81%～108%,相对标准偏差为1.2%～5.1%(n=6)。方法的检出限为0.6 ng/L。结果表明,该方法灵敏度高,线性关系好,可以满足简便、快速、准确测定海水中十氯酮的要求。     

气相色谱-微池电子捕获器检测尿液中的三唑仑

建立了气相色谱-微池电子捕获检测器(GC-μECD)检测尿液中三唑仑的方法。筛选了pH值、提取溶剂、涡旋时间,优化了液-液萃 取条件。在0.2～50 ng/mL范围内,线性关系良好,相关系数为0.9995;方法的检出限为0.1 ng/mL,日内和日间测定的相对标准偏差分 别为4.17%和5.31%,平均回收率为93.9%。该方法操作简便、灵敏度高、线性范围广、回收率高,完全能够满足日常检测工作的需要。     

Optimization of conditions in static headspace GC

The precision and sensitivity of head-space GC can be improved by careful selection of the operating conditions: partitioning in the vapor phase can be promoted by altering the sample matrix; the ratio of the volumes of the gaseous and liquid phases, the sample temperature, the equilibration time, and the effect of sample mixing should also be considered. Most of the principles covered here can be applied to either manual headspace GC or to headspace GC utilizing an automated sampler.     

Determination of partition coefficients by automatic equilibrium headspace gas chromatography by vapor phase calibration

Summary Equilibrium headspace gas chromatography has been applied to the determination of the partition coefficients of volatile compounds in water-air systems. Only techniques that are suited to a fully automatic headspace procedure using the pneumatic headspace sampling-technique have been considered. Particularly simple is the technique of vapor phase calibration —VPC where an external vapor standard is used to calibrate the concentration of the volatile analyte in the headspace, while the concentration in the sample is found from the difference in the total amount in the vial. This technique is described in detail for 2-butanone in water. Finally, the water-air partition coefficients of several selected volatile compounds at different temperatures are listed together with their temperature functions.Dedicated to Professor Leslie S. Ettre on the occasion of his 70th birthday.     

Ultrasound‐assisted extraction and solid‐phase extraction as a cleanup procedure for organochlorinated pesticides and polychlorinated biphenyls determination in aquatic samples by gas chromatography with electron capture detection

The feasibility of developing a quick, easy, efficient procedure for the simultaneous determination of organochlorinated pesticides and polychlorinated biphenyls in aquatic samples using gas chromatography with electron capture detection based on solid‐phase extraction was investigated. The extraction solvent (n‐hexane/acetone, cyclohexane/ethyl acetate, n‐hexane/dichloromethane, n‐hexane) for ultrasound‐assisted solid–liquid extraction and solid‐phase extraction columns (florisil, neutral alumina, acidic alumina, aminopropyl trimethoxy silane, propyl ethylenediamine, aminopropyl trimethoxy silane/propyl ethylenediamine, graphitized carbon black and silica) for cleanup procedure were optimized. The gas chromatography with electron capture detection method was validated in terms of linearity, sensitivity, reproducibility, and recovery. Mean recoveries ranged from 75 to 115% with relative standard deviations <13%. Quantification limits were 0.20–0.40 ng/g for organochlorinated pesticides and polychlorinated biphenyls. The satisfactory data demonstrated the good reproducibility of the method with relative standard deviations lower than 13%. In comparison to other related methods, this method requires less time and solvent and allows for rapid isolation of the target analytes with high selectivity. This method therefore allows for the screening of numerous samples and can also be used for routine analyses.     

Analysis of volatile aromatic compounds in gasoline-contaminated ground water samples by static headspace sampling and high speed gas chromatography

A 15 second, high speed, gas chromatographic determination has been performed on the volatile aromatic compounds in gasoline-contaminated ground water following manual, static headspace sampling. Retention time reproducibility of the seven peaks studied ranged from 0.25 to 0.67 per cent (average relative standard deviation). Excellent linear correlations were obtained for plots of either peak height or peak area against the concentration of the compounds. Comparison was made between the results obtained from the analysis of three replicate samples of gasoline-contaminated ground water by the high speed GC, by two field-portable GCs, and by a laboratorybased GC. It is worthy of note that all the high speed GC analyses required for this study were accomplished in one day.     

Determination of synthetic polycyclic musks in water by microwave-assisted headspace solid-phase microextraction and gas chromatography-mass spectrometry

This paper describes a rapid and solvent-free method, microwave-assisted headspace solid-phase microextraction (MA-HS-SPME), for the extraction of six commonly used synthetic polycyclic musks: galaxolide (HHCB), tonalide (AHTN), celestolide (ADBI), traseolide (ATII), cashmeran (DPMI) and phantolide (AHMI) from water samples prior to their determination using gas chromatography-mass spectrometry (GC-MS). The effects of various extraction parameters for the quantitative extraction of these analytes by MA-HS-SPME were systematically investigated and optimized. The analytes in a 20-mL water sample (in a 40-mL sample-vial containing 4 g of NaCl) were efficiently extracted by a polydimethylsiloxane-divinylbenzene (PDMS-DVB) fiber placed in the headspace when the system was microwave irradiated at 180 W for less than 4 min. The limits of detection (LODs) ranged from 0.05 to 0.1 ng/L, and the limits of quantification (LOQs) were less than 0.2 ng/L. A preliminary analysis of wastewater samples revealed that HHCB and AHTN were the two most commonly detected synthetic polycyclic musks; using a standard addition method, their concentration were determined to range from 1.2 to 37.3 ng/L with relative standard deviation (RSD) ranging from 2 to 6%. The results obtained using this approach are better than those from the conventional oil-bath HS-SPME.     

Determination of organophosphorous pesticides in water using in-syringe ultrasound-assisted emulsification and gas chromatography with electron-capture detection

An in-syringe ultrasound-assisted emulsification microextraction (USAEME) was developed for the extraction of organophosphorus pesticides (OPPs) from water samples. The OPPs subsequently analyzed gas chromatography (GC) using a microelectron capture detector (μECD). Ultrasound radiation was applied to accelerate the emulsification of μL-level low-density organic solvent in aqueous solutions to enhance the microextraction efficiency of OPPs in the sample preparation for GC-μECD. Parameters affecting the efficiency of USAEME, such as the extraction solvent, solvent volume, pH, salt-addition, and extraction time were thoroughly investigated. Based on experimental results, OPPs were extracted from a 5 mL aqueous sample by the addition of 20 μL toluene as the extraction solvent, followed by ultrasonication for 30 s, and then centrifugation for 3 min at 3200 rpm, offered the best extraction efficiency. Detections were linear in the concentration of 0.01–1 μg/L with detection limits between 1 ng/L and 2 ng/L for OPPs. Enrichment factors ranged from 330 to 699. Three spiked aqueous samples were analyzed, and recovery ranged from 90.1% to 104.7% for farm-field water, and 90.1% to 101.8% for industrial wastewater. The proposed method provides a simple, rapid, sensitive, inexpensive, and eco-friendly process for determining OPPs in water samples.     

Comparison of quantitative analytical methods in headspace gas chroamtography of residual solvents

Summary The aim of this work was to compare quantitative methods used for headspace gas chromatographic analysis of residual solvents in standard aqueous solutions and to apply the methods to the analysis of medicines. We found that all three quantitative methods (external standard, ESTD; internal standard, ISTD; and standard addition, ASTD) enable determination of the total amount of solute in the equilibrated system by analysis of defined volumes of headspace gas. The results showed that the ISTD method is more precise than ESTD and ASTD when there is no strong interaction between the residual solvents and the pharmaceutical base material. When, however, there is a strong polarpolar interaction between them, the ESTD and ISTD methods give worse results than the ASTD method, because the ASTD method can eliminate the matrix effect. Presented at Balaton Symposium on High Performance Separation Methods, Siófok, Hungary, September 1–3, 1999     

Analysis of trace levels of trichothecene mycotoxins in Austrian cereals by gas chromatography with electron capture detection

Summary Various analytical methods developed for trichothecene determination, including TLC, HPLC, GC, supercritical fluid chromatography (SFC) and enzyme immuno assay (EIA) are reviewed. In addition a new method is described for the simultaneous determination of the trichothecene mycotoxins deoxynivalenol (DON), nivalenol (NIV), 3-acetyldeoxynivalenol (3-ADON), diacetoxyscirpenol (DAS), T-2 toxin (T-2), HT-2 toxin (HT-2) and T-2 triol (TRIOL), in Austrian wheat and corn samples by GC-ECD. A clean-up procedure has been developed using a combination of liquid-liquid and liquid-solid extraction. Trichothecenes were detected as their heptafluorobuturyl esters or alternatively as trimethylsilyl ethers (only sensitive for deoxynivalenol and nivalenol) using nandrolone or chloramphenicol as internal standard. Four derivatization techniques using HFBI, HFBA+DMAP on polystyrene, TMSI and TMSI+BSA+TMCS have been studied and the advantages and disadvantages of each are discussed. Quantification of trichothecenes from 10 to 1000 ppb in cereals could be accomplished routinely.Presented at the 19th ISC, Aix-en-Provence, France, September 13–18, 1992.     

Determination of chlorobenzenes in environmental samples using solid phase microextraction, thermal desorption and analysis by gas chromatography coupled to FID, ECD, MSD, IRD detectors

Summary A complex method was developed for the determination of chlorobenzenes in soil and groundwater samples. Samples were taken at two sites in Baranya county, where a mixture of chlorobenzene waste was deposited, causing severe contamination in the environment. Clean-up of these sites demands modern and reliable analytical methods. Several sample preparation techniques were used, such as solid phase microextraction (SPME), supercritical fluid extraction (SFE), and a recently developed thermal desorption method. The applicability of various sample preparation methods was compared by measuring recovery percentages, relative standard deviations and by investigating the matrix dependency of these values. Gas chromatography was used for quantitative determination of chlorobenzenes, using MS, IR, FID and ECD detection techniques. Detection levels were as low as 1 ppt in water, and 10 ppt in soil samples. Chlorobenzene concentration was in the range 1 ppt-1 ppm in water and 100 ppb-100 ppm in soil samples. Identification and calibration of these compounds were performed by quantitative standards. This complex analytical method can be used for rapid and precise quantitative and qualitative determination of chlorobenzenes. Presented at: Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 3–5, 1997