Solid-phase microextraction coupled with gas chromatography-ion trap mass spectrometry for the analysis of haloacetic acids in water

Headspace solid-phase microextraction (SPME) was studied as a possible alternative to liquid-liquid extraction for the analysis of haloacetic acids (HAAs) in water. The method involves derivatization of the acids to their ethyl esters using sulphuric acid and ethanol after evaporation, followed by headspace SPME with a polydimethylsiloxane fibre and gas chromatography-ion trap mass spectrometry (GC-IT-MS). The derivatization procedure was optimized: maximum sensitivity was obtained with esterification for 10 min at 50 degrees C in 30 microl of sulphuric acid and 40 microl of ethanol. The headspace SPME conditions were also optimized and good sensitivity was obtained at a sampling temperature of 25 degrees C, an absorption time of 10 min, the addition of 0.1 g of anhydrous sodium sulfate and a desorption time of 2 min. Good precision (RSD lower than 10%) and detection limits in the ng l(-1) range (from 10 to 200 ng l(-1)) were obtained for all the compounds. The optimized procedure was applied to the analysis of HAAs in tap water and the results obtained by standard addition agreed with those of EPA method 552.2, whereas discrepancies due to matrix interferences were observed using external calibration. Consequently, headspace SPME-GC-IT-MS with standard addition is recommended for the analysis of these compounds in drinking water.     

Separation and determination of seleno amino acids using gas chromatography hyphenated with inductively coupled plasma mass spectrometry after hollow fiber liquid phase microextraction

A new derivatization–extraction method for preconcentration of seleno amino acids using hollow fiber liquid phase microextraction (HF‐LPME) was developed for the separation and determination of seleno amino acids in biological samples by gas chromatography–inductively coupled plasma mass spectrometry (GC–ICP‐MS). Derivatization was performed with ethyl chloroformate (ECF) to improve the volatility of seleno amino acids. Parameters influencing microextraction, including extraction solvent, pH of sample solution, extraction time, stirring speed, and inorganic salt concentration have been investigated. Under the optimal conditions, the limits of detection (LODs) obtained for Se‐methyl‐selenocysteine (SeMeCys), selenomethionine (SeMet), and selenoethionine (SeEth) were 23, 15, and 11 ng Se l⁻¹, respectively. The relative standard deviations (RSDs) were 14.6%, 16.4%, and 19.4% for SeMeCys, SeMet, and SeEth (c = 1.0 ng ml⁻¹, n = 7), respectively, and the RSDs for SeMeCys, SeMet could be improved obviously if SeEth was utilized as the internal standard. The proposed method was applied for the determination of seleno amino acids in extracts of garlic, cabbage, and mushroom samples, and the recoveries for the spiked samples were in the range of 96.8–108% and 93.4–115% with and without the use of SeEth as internal standard. The developed method was also applied to the analysis of SeMet in a certified reference material of SELM‐1 yeast and the determined value is in good agreement with the certified value. Copyright © 2008 John Wiley & Sons, Ltd.     

Quantitative analysis of volatile selenium metabolites in normal urine by headspace solid phase microextraction gas chromatography-inductively coupled plasma mass spectrometry

The combination of headspace-solid phase microextraction (HS-SPME) and gas chromatography-inductively coupled plasma mass spectrometry (GC-ICPMS) was evaluated for the determination of volatile selenium metabolites in normal urine samples, i.e. without selenium supplementation. HS-SPME operating conditions were optimised and a sampling time of 10 min was found to be suitable for simultaneous extraction of dimethylselenide (DMSe) and dimethyldiselenide (DMDSe). The amount of DMSe and DMDSe extracted onto fibre coating was calculated in clean matrix, i.e. Milli-Q water, on the basis of depletion experiments. When applied to normal urine samples, the developed method allowed the detection of four volatile selenium containing species, among which DMSe and DMDSe could be quantified by standard additions.     

Serum/plasma methylmercury determination by isotope dilution gas chromatography-inductively coupled plasma mass spectrometry

A method for the determination of methylmercury in plasma and serum samples was developed. The method uses isotope dilution with ¹⁹⁸Hg-labeled methylmercury, extraction into dichloromethane, back-extraction into water, aqueous-phase ethylation, purge and trap collection, thermal desorption, separation by gas chromatography, and mercury isotope specific detection by inductively coupled plasma mass spectrometry. By spiking 2 mL sample with 1.2 ng tracer, measurements in a concentration interval of (0.007–2.9) μg L⁻¹ could be performed with uncertainty amplification factors <2. A limit of quantification of 0.03 μg L⁻¹ was estimated at 10 times the standard deviation of concentrations measured in preparation blanks. Within- and between-run relative standard deviations were <10% at added concentration levels of 0.14 μg L⁻¹, 0.35 μg L⁻¹ and 2.8 μg L⁻¹, with recoveries in the range 82–110%. Application of the method to 50 plasma/serum samples yielded a median (mean; range) concentration of methylmercury of 0.081 (0.091; <0.03–0.19) μg L⁻¹. This is the first time methylmercury has been directly measured in this kind of specimen, and is therefore the first estimate of a reference range.     

固相微萃取-气相色谱-红外光谱联用技术分析水处理药剂

在循环水系统中,水处理药剂起着重要的作用,它可以缓蚀阻垢,还可抑制细菌增长,提高水源质量.开发水处理药剂有着广泛的市场.水处理药剂的组成不同性能会有所差别,分析不同组成的药剂从而有针对性地开发新品种,加快了产出速度.本文利用固相微萃取-气相色谱-红外光谱联用技术对某水处理药剂进行了剖析,从而为开发新型药剂提供了依据,节约了开发周期.固相微萃取技术是90年代发展的一种集萃取,浓缩,进样于一体的样品前处理方法.基本的固相微萃取是通过石英纤维头表面涂渍的高分子层对样器中直接热解吸,使样品预处理过程大为简化,提高了分析速度和灵敏度,其检出限的数量级位ng/g～pg/g,相对标准偏差小于30%,线性范围为3～5个数量级.气相色谱-红外光谱联用技术结合了气相色谱分离性能高的特点和红外光谱的定性能力较强的特点,在实验过程中对于色谱条件我们选用固相微萃取技术,大大提高了检出度,通过改善气相色谱分离条件,很好地分析了水处理药剂中的组成.根据相似相容原理,结合分析物的极性,沸点和分配系数,选用了聚二甲基硅氧烷涂层萃取纤维;通过考虑分析物的分配系数,物质的扩散速率,样品基质,样品体积,萃取头膜厚等因素萃取时间选为5 min;选择热辑吸时间为3 min,进样口温度为300℃时,解析完全.利用程序升温,检测出10余个组分,对其中10个组分给出定性结果,依保留时间增大顺序,检出的10个峰分别为:水,1,2丙二醇,N,N二甲基十二烷基胺,癸醛,硫醇,N,N二甲基十二烷基胺同系物,1-溴十一烷,N,甲基二辛胺及其同系物等.定性结果与红外标准谱的匹配率均在90%以上.结果表明,该水处理药剂含有氮-氮类化合物,这类化合物正是发挥药剂作用的核心.     

Solid-phase microextraction: a powerful sample preparation tool prior to mass spectrometric analysis

Sample preparation is an essential step in analysis, greatly influencing the reliability and accuracy of resulted the time and cost of analysis. Solid-Phase Microextraction (SPME) is a very simple and efficient, solventless sample preparation method, invented by Pawliszyn in 1989. SPME has been widely used in different fields of analytical chemistry since its first applications to environmental and food analysis and is ideally suited for coupling with mass spectrometry (MS). All steps of the conventional liquid-liquid extraction (LLE) such as extraction, concentration, (derivatization) and transfer to the chromatograph are integrated into one step and one device, considerably simplifying the sample preparation procedure. It uses a fused-silica fibre that is coated on the outside with an appropriate stationary phase. The analytes in the sample are directly extracted to the fibre coating. The SPME technique can be routinely used in combination with gas chromatography, high-performance liquid chromatography and capillary electrophoresis and places no restriction on MS. SPME reduces the time necessary for sample preparation, decreases purchase and disposal costs of solvents and can improve detection limits. The SPME technique is ideally suited for MS applications, combining a simple and efficient sample preparation with versatile and sensitive detection. This review summarizes analytical characteristics and variants of the SPME technique and its applications in combination with MS.     

Determination of trace-level haloacetic acids in drinking water by ion chromatography-inductively coupled plasma mass spectrometry

A new method for the determination of nine haloacetic acids (HAAs) with ion chromatography (IC) coupled to inductively coupled plasma mass spectrometry (ICP-MS) was developed. With the very hydrophilic anion-exchange column and steep gradient of sodium hydroxide, the nine HAAs could be well separated in 15 min. After suppression with an ASRS suppressor that was introduced in between IC and ICP-MS, the background was much decreased, the interference caused by sodium ion present in eluent was removed, and the sensitivities of HAAs were greatly improved. The chlorinated and brominated HAAs could be detected as 35ClO and 79Br without interference of the matrix due to the elemental selective ICP-MS. The detection limits for mono-, di-, trichloroacetic acids were between 15.6 and 23.6 microg/l. For the other six bromine-containing HAAs, the detection limits were between 0.34 and 0.99 microg/l. With the pretreatment of OnGuard Ag cartridge to remove high concentration of chloride in sample, the developed method could be applied to the determination of HAAs in many drinking water matrices.     

Speciation of butyltin compounds in environmental and biological samples using headspace single drop microextraction coupled with gas chromatography-inductively coupled plasma mass spectrometry

A method based on headspace single drop microextraction (HS-SDME) in combination with gas chromatography-inductively coupled plasma mass spectrometry (GC-ICP-MS) was proposed for the speciation analysis of butyltin compounds in environmental and biological samples. The sodium tetraethylborate (NaBEt4) and sodium tetrahydroborate (NaBH4) were used as the derivatizing reagent for in situ derivatization of the butyltins. For the two derivatizations, the HS-SDME parameters such as organic solvent, drop volume, sample pH, stirring rate, temperature, extraction time and the ionic strength were examined systematically. The analytical performance including the linearity ranges, limits of detection (LODs) and reproducibilities of the two derivatizations were compared under the respective optimized conditions. Derivatization with NaBEt(4) proved to be more sensitive and robust than that with NaBH4, leading to the LODs of 1.4 ng/L for MBT, 1.8 ng/L for DBT and 0.8 ng/L for TBT. The reproducibilities, expressed as relative standard deviations (RSDs), were in the range of 1.1-5.3% (c=1 microg/L, n=3). With tripropyltin (TPrT) as internal standard, HS-SDME-GC-ICP-MS with NaBEt(4) derivatization was applied for the speciation analysis of butyltins in real seawater and shellfish samples. The butyltins found in the real-world samples are 31ng/L MBT, 79 ng/L DBT and 32 ng/L TBT for seawater, and 11.6-30.4 ng/g MBT, 11.8-8.9 ng/g DBT and 12.8-52.6 ng/g TBT for different shellfish samples. For validation, the developed method was also employed for the speciation analysis of butyltins in certified reference material (CRM) of PACS-2 sediment, and the determined values are in a good agreement with the certified values. The developed method is simple, rapid, sensitive, and cost-effective and provides an attractive alternative for butyltins speciation in biological and environmental samples with complex matrix.     

On-line capillary supercritical fluid chromatography-inductively coupled plasma mass spectrometry for the analysis of organometallic compounds

Supercritical fluid chromatography with inductively coupled plasma-mass spectrometric detection is a new and useful technique for the analysis of organometallic compounds. An interface has been developed for coupling these techniques. The interface is compact, easy to assembel, and causes minimal disruption to either instrument. A series of organotin, organoarsenic, and organorion compounds has been used to evaluate the interface and ICPMS as a detector for SFC. The effect of analyte concentration and restrictor temperature on peak intensity has been investigated and the effect of the mobile phase on the plasma has also been studied to assess background interference from changes in the plasma.     

Solid-phase microextraction method for carbon isotopic analysis of volatile carboxylic acids in human plasma by gas chromatography/combustion/isotope ratio mass spectrometry

A new analytical method is described for the determination of the physiological concentration and low-level enrichment of (13)C-short-chain volatile organic acids (SCVAs) (e.g. (13)C-acetate and (13)C-butyrate) in human plasma. This two-step method involves solid-phase microextraction (SPME) coupled to gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) without any organic solvents or derivatizing agents. Two SCVA extraction methods were compared using a carboxen/polydimethylsiloxane fiber: headspace sampling (HS) and liquid sampling (LS) SPME. The influences of extraction temperature and time were tested to optimize the adsorption of SCVAs onto the fiber. The comparison of the peak area responses of the acids in the two adsorption methods showed better sensitivity in the human physiological concentration range in the LS mode than in the HS mode.The accuracy of isotopic enrichment measurement was determined using plasma spiked with (13)C-acetate and (13)C-butyrate solution from 0 to 1 mol percent excess (MPE). The linearity and repeatability (RSD < 5%) were measured in LS mode. Plasma SCVA concentrations were also determined relative to 3-methylvalerate (internal standard). Linearity and repeatability were observed from 0 to 400 microM for acetate, from 0 to 20 microM for propionate, and from 0 to 10 microM for butyrate. This method was also used to determine plasma acetate production obtained from lactulose (an undigestible disaccharide) fermentation in one healthy volunteer over 3 h. The acetate concentration increased twofold, 2 h after oral lactulose intake. These results are in agreement with the data obtained by GC/MS in healthy volunteers and obese adults following a lactulose intake by using higher amounts of labelled tracers.SPME coupled with GC/C/IRMS can be used to analyze (13)C-SCVAs at low enrichment (<0.5 MPE) within the physiological concentration measured in human plasma.     

Simultaneous determination of arsenic species by ion chromatography-inductively coupled plasma mass spectrometry

Six arsenic species, arsenite, arsenate, monomethylarsonic acid, dimethylarsinic acid, arsenobetaine and arsenocholine, were separated by coupled column ion chromatography using carbonate and nitric acid as eluents, and were detected by inductively coupled plasma mass spectrometry. Coupling of an anion column with a cation column made the simultaneous determination of both the cationjic and the anionic arsenic species possible by ion chromatography. Extremely low detection limits, below 0.2 μg/1 (as arsenic), were obtained for all the species studied.     

Speciation of halogenides and oxyhalogens by ion chromatography-inductively coupled plasma mass spectrometry

A speciation method utilizing ion chromatography coupled with inductively coupled plasma mass spectrometry is described for simultaneous analysis of eight halogenides and oxyhalogens: chloride, chlorite, chlorate, perchlorate, bromide, bromate, iodide and iodate. The method was applied for the analysis of drinking water samples collected from water treatment plants in areas in Finland, which are known to have high bromine concentrations in ground water. Water samples collected before and after disinfection were analyzed to get information about potential species conversion as a result of purification. Chloride and chlorate were the chlorine species found in these water samples, and iodine existed as both iodate and iodide. In the case of bromine, species conversion had taken place, since total bromine concentrations were increased during disinfection but bromide concentrations were decreased. No bromate was observed in the samples. The detection limits for all the chlorine species studied were 500 μg/l, for bromine species studied 10 μg/l, for iodide 0.1 μg/l and for iodate 0.2 μg/l.     

Solid-phase microextraction: a promising technique for sample preparation in environmental analysis

Solid-phase microextraction (SPME) is a simple and effective adsorption and desorption technique, which eliminates the need for solvents or complicated apparatus, for concentrating volatile or nonvolatile compounds in liquid samples or headspace. SPME is compatible with analyte separation and detection by gas chromatography and high-performance liquid chromatography, and provides linear results for wide concentrations of analytes. By controlling the polarity and thickness of the coating on the fibre, maintaining consistent sampling time, and adjusting other extraction parameters, an analyst can ensure highly consistent, quantifiable results for low concentration analytes. To date, about 400 articles on SPME have been published in different fields, including environment (water, soil, air), food, natural products, pharmaceuticals, biology, toxicology, forensics and theory. As the scope of SPME grew, new improvements were made with the appearance of new coatings that allowed an increase in the specificity of this extraction technique. The key part of the SPME fibre is of course the fibre coating. At the moment, 27 variations of fibre coating and size are available. Among the newest are a fibre assembly with a dual coating of divinylbenzene and Carboxen suspended in poly(dimethylsiloxane), and a series of 23 gauge fibres intended for specific septumless injection system. The growth of SPME is also reflected in the expanding number of the accessories that make the technology even easier to use Also available is a portable field sampler which is a self-contained unit that stores the SPME fibre after sampling and during the shipment to the laboratory. Several scientific publications show the results obtained in inter-laboratory validation studies in which SPME was applied to determine the presence of different organic compounds at ppt levels, which demonstrates the reliability of this extraction technique for quantitative analysis.     

Speciation analysis of arsenic compounds in edible oil by ion chromatography-inductively coupled plasma mass spectrometry

An inductively coupled plasma mass spectrometer (ICP-MS) was used as an ion chromatographic (IC) detector for the speciation analysis of arsenic in edible oil. The arsenic species studied include arsenite, arsenate, monomethylarsonic acid, dimethylarsinic acid, arsenobetaine and arsenocholine. Gradient elution using (NH(4))(2)CO(3) and methanol at pH 8.5 allowed the chromatographic separation of all species in less than 8 min. Effluents from the IC column were delivered to the nebulizer of ICP-MS for the determination of arsenic. The concentrations of arsenic species have been determined in several used and fresh vegetable oil samples. In this study, a microwave-assisted extraction method was used for the extraction of arsenic species from oil samples. The extraction efficiency was better than 92% and the recoveries from spiked samples were in the range of 90-105%. The precision between sample replicates was better than 8% for all determinations. The limits of detection were in the range of 0.008-0.024 ng mL(-1) for various arsenic species based on peak height, which corresponded to 0.08-0.24 ng g(-1) in the original oil sample. The major arsenic species in the used oil samples varied based on the food items cooked.     

Solid-phase microextraction coupled with gas chromatography and gas chromatography—Mass spectrometry for public health pesticides analysis

Summary Public health pesticides in two-component mixed solutions were analyzed using solid-phase microextraction (SPME) coupled with gas chromatography (GC) and gas chromatography—mass spectrometry (GC-MS). The two-component mixed solutions used were allethrin mixed with cyfluthrin, cypermethrin mixed with tetramethrin, and transfluthrin mixed with cyfluthrin. Quantitative SPME-GC and SPME-GC-MS analyses using calibration and standard addition methods were evaluated. Using SPME pretreatment saved several tens to hundreds of mL of organic solvent. Quantitative analyses of the SPME-GC and SPME-GC-MS using the calibration and standard addition methods showed promise for simple, fast, and solventless public health pesticide analysis.     

Speciation of chromium in waste waters by coupled column ion chromatography-inductively coupled plasma mass spectrometry

An application of coupled column ion chromatography (IC)-inductively coupled plasma mass spectrometry (ICP-MS) is presented for speciation of chromium in waste waters. By coupling an anion column with a cation column, both the cationic Cr(III) and anionic Cr(VI) species can be analyzed with detection limits below 0.5 μg/1. The separation of the interfering ions (chloride, chlorate, perchlorate, sulphate, sulphite, sulphide, thiosulphate, carbonate, cyanide and some organic compounds) from the chromium peaks is discussed, and the use of different chromium isotopes for data acquisition is compared. Based on the results, m/z 52 was considered as an ideal isotope for speciation of chromium in waste waters by the coupled column IC-ICP-MS, because it did not suffer from polyatomic interferences and due to the high sensitivity for chromium. The analysis of the waste water samples should be performed as soon as possible after sampling according to the stability tests of the species.     

Speciation of mercury in water samples by dispersive liquid-liquid microextraction combined with high performance liquid chromatography-inductively coupled plasma mass spectrometry

The dispersive liquid-liquid microextraction (DLLME) combined with high performance liquid chromatography-inductively coupled plasma mass spectrometry for the speciation of mercury in water samples was described. Firstly methylmercury (MeHg⁺) and mercury (Hg²⁺) were complexed with sodium diethyldithiocarbamate, and then the complexes were extracted into carbon tetrachloride by using DLLME. Under the optimized conditions, the enrichment factors of 138 and 350 for MeHg⁺ and Hg²⁺ were obtained from only 5.00 mL sample solution. The detection limits of the analytes (as Hg) were 0.0076 ng mL⁻¹ for MeHg⁺ and 0.0014 ng mL⁻¹ for Hg²⁺, respectively. The relative standard deviations for ten replicate measurements of 0.5 ng mL⁻¹ MeHg⁺ and Hg²⁺ were 6.9% and 4.4%, respectively. Standard reference material of seawater (GBW(E)080042) was analyzed to verify the accuracy of the method and the results were in good agreement with the certified values. Finally, the developed method was successfully applied for the speciation of mercury in three environmental water samples.     

Elemental speciation by liquid chromatography-inductively coupled plasma mass spectrometry with direct injection nebulization.

A new version of the direct injection nebulizer (DIN) is used to interface liquid chromatographic (LC) separations with element-selective detection using inductively coupled plasma mass spectrometry (ICP-MS). The DIN injects all of the sample into the ICP and has a dead volume of less than 1 microliter. Charged species of arsenic and tin are separated as ion pairs on a micro-scale (1 mm i.d.), packed, reversed-phase column. Detection limits are 0.2-0.6 pg for arsenic and 8-10 pg for tin. For methanol + water eluents, the signal is highest at 25% methanol and stays within 25% of this maximum as the methanol fraction is varied from 20 to 80%. Compared with LC-ICP-MS with conventional nebulizers, the absolute detection limits and chromatographic resolution are substantially superior, and the dependence of analyte signal on solvent composition is somewhat less severe with the DIN.     

Determination of arsenic compounds in beverages by high-performance liquid chromatography-inductively coupled plasma mass spectrometry

Arsenic compounds including arsenous acid (As(III)), arsenic acid (As(V)), dimethylarsinic acid (DMA) and monomethylarsonic acid (MMA) were separated by high-performance liquid chromatography (HPLC) and detected by inductively coupled plasma mass spectrometry (ICP-MS). A Hamilton PRX-100 anionic-exchange column and a pH 8.5 K₂HPO₄/KH₂PO₄ 5.0 × 10⁻³ mol L⁻¹ mobile phase were used to achieve arsenic speciation. The separation of arsenic species provided peaks of As(III) at 2.75 min, DMA at 3.33 min, MMA at 5.17 min and As(V) at 12.5 min. The detection limits, defined as three times the standard deviation of the lowest standard measurements, were found to be 0.2, 0.2, 0.3 and 0.5 ng mL⁻¹ for As(III), DMA, MMA and As(V), respectively. The relative standard deviation values for a solution containing 5.0 μg L⁻¹ of As(III), DMA, MMA and As(V) were 1.2, 2.1, 2.5 and 3.0%, respectively. This analytical procedure was applied to the speciation of arsenic compounds in drinking (soft drink, beer, juice) samples. The validation of the procedure was achieved through the analysis of arsenic compounds in water and sediment certified reference materials.     

Simultaneous determination of trimethyl-and triethyllead in urban dust by species-specific isotope dilution/gas chromatography-inductively coupled plasma mass spectrometry

Both (206)Pb-labeled trimethyllead (TML) and triethyllead (TEL) were synthesized from (206)Pb-enriched metallic Pb certified reference material (NIST SRM 983) and iodomethane or iodoethane through a one-process reaction in a closed system using centrifuge tubes, respectively. Organolead compounds in an urban dust reference material (BCR CRM 605) were extracted with an acetic acid/methanol (1:1) solution, which was mechanically shaken for 24 h. After adjusting the pH of the extracted solution to pH 5, the extracted organolead compounds were derivatized by tetrabutylammonium tetrabutylborate (TATB) and measured with GC-ICPMS. The analytical results of TML and TEL for BCR CRM 605 were 8.22 +/- 0.04 microg kg(-1) (mean +/- standard deviation, n = 3) and 1.12 +/- 0.06 microg kg(-1), respectively. The analytical results of TML agreed well with the certified value (7.9 +/- 1.2 microg kg(-1)).