Speciation of alkyllead and inorganic lead by derivatization with deuterium-labeled sodium tetraethylborate and SPME-GC/MS

Online measurement of tetraethyllead in aqueous samples utilizing monolith-based magnetism-enhanced in-tube solid phase microextraction coupled with chromatographic analysis

A new procedure that utilizing a preconcentration system based on magnetism-enhanced in-tube solid phase microextraction (ME/IT-SPME) and detection by HPLC with diode array detector (DAD) after liquid desorption from the microextraction column has been developed for the online measurement of tetraethyllead (TEL) in various aqueous samples. In this connection, according to the chemical features of TEL, porous monolith mingled with Fe₃O₄ nanoparticles were designed and synthesized in a silica capillary, and used as the microextraction column of ME/IT-SPME. To favor the implement of variable magnetic fields during extraction procedure, the as-prepared microextraction column was twined a magnetic coil. Results revealed that the exertion of magnetic field during the adsorption and eluting procedures assisted the extraction of TEL with an enhancement by 52% in extraction efficiency. Under the most beneficial conditions, the developed ME/IT-SPME was online hyphenated with HPLC/DAD to measure trace TEL in various aqueous samples. The limit of detection was 0.082 μg/L and the RSDs for precision were in the range of 6.3-8.5%. The recoveries with low, medium and high fortified levels varied from 80.6% to 95.0% with good repeatability. To the best of knowledge, this is the first study that using IT-SPME to extract TEL and then online quantification with HPLC/DAD.

Determination of Tetraethyl Lead in Gasoline fuel

  Tetraethyl lead TEL is an organometallic component that is added to gasoline to improve engine performance. This material is also called an anti-knock because it reduces the knocking of the engine. The engine starts to throttle if the oil in its pistons burns quickly or after a short period of time from entering it. In this study, a sensitive,  simple, economical, fast and accurate, an indirect spectral analytical method has been developed  using Eriochrome Black T as chelating agent without use of separation and  isolation to estimate the amount of lead in the gasoline by using UV-Visible spectrophotometer instrument. The accuracy and sensitivity of the method were 99.9067 ± 0.09 and 0.0338 while the limits of detection (LOD) and qualification (LOQ) were 0.0721 and    0.2186 μg ml-1 respectively. The developed method can be applied to water, biological, environmental and fuel sample.

Advanced Solid-Phase Microextraction Techniques and Related Automation: A Review of Commercially Available Technologies

The solid-phase microextraction (SPME), invented by Pawliszyn in 1989, today has a renewed and growing use and interest in the scientific community with fourteen techniques currently available on the market. The miniaturization of traditional sample preparation devices fulfills the new request of an environmental friendly analytical chemistry. The recent upswing of these solid-phase microextraction technologies has brought new availability and range of robotic automation. The microextraction solutions propose today on the market can cover a wide variety of analytical fields and applications. This review reports on the state-of-the-art innovative solid-phase microextraction techniques, especially those used for chromatographic separation and mass-spectrometric detection, given the recent improvements in availability and range of automation techniques. The progressively implemented solid-phase microextraction techniques and related automated commercially available devices are classified and described to offer a valuable tool to summarize their potential combinations to face all the laboratories requirements in terms of analytical applications, robustness, sensitivity, and throughput.

Solid phase microextraction techniques used for gas chromatography: a review

In the last decade, the development and adoption of greener and sustainable microextraction techniques have been proved to be an effective alternative to classical sample preparation procedures. In this review, 10 commercially available solid-phase microextraction systems are presented, with special attention to the appraisal of their analytical, bioanalytical, and environmental engineering. This review provides an overview of the challenges and achievements in the application of fully automated miniaturized sample preparation methods in analytical laboratories. Both theoretical and practical aspects of these environment-friendly preparation approaches are discussed. The application of chemometrics in method development is also discussed. We are convinced that green analytical chemistry will be really useful in the years ahead. The application of cheap, fast, automated, “clever”, and environmentally safe procedures to environmental, clinical, and food analysis will improve significantly the quality of the analytical data.

Microextraction techniques used in the procedures for determining organomercury and organotin compounds in environmental samples

Due to human activities, the concentrations of organometallic compounds in all parts of the environment have increased in recent decades. The toxicity and some biochemical properties of mercury and tin present in the environment depend on the concentration and chemical form of these two elements. The ever-increasing demand for determining compounds at very low concentration levels in samples with complex matrices requires the elimination of interfering substances, the reduction of the final extract volume, and analyte enrichment in order to employ a detection technique, which is characterised by high sensitivity at low limits of quantification. On the other hand, in accordance with current trends, the analytical procedures should aim at the miniaturisation and simplification of the sample preparation step. In the near future, more importance will be given to the fulfilment of the requirements of Green Chemistry and Green Analytical Chemistry in order to reduce the intensity of anthropogenic activities related to analytical laboratories. In this case, one can consider the use of solvent-free/solvent-less techniques for sample preparation and microextraction techniques, because the use of the latter leads to lowering the quantity of reagents used (including solvents) due to the reduction of the scale of analysis. This paper presents an overview of microextraction techniques (SPME and LPME) used in the procedures for determining different chemical forms of mercury and tin.

Simultaneous separation and speciation of inorganic As(III)/As(V) and Cr(III)/Cr(VI) in natural waters utilizing capillary microextraction on ordered mesoporous Al2O3 prior to their on-line determination by ICP-MS

In this paper, a system of flow injection (FI) capillary microextraction (CME) on line coupled with inductively plasma mass spectrometry (ICP-MS) was proposed for simultaneous separation and speciation of inorganic As(III)/As(V) and Cr(III)/Cr(VI) in natural waters. Ordered mesoporous Al2O3 coating was prepared by sol-gel technology and used as CME coating material. Various experimental parameters affecting the capillary microextraction of inorganic arsenic and chromium species have been investigated and optimized. Under the optimized conditions, the limits of detection were 0.7 and 18 ng L(-1) for As(V) and Cr(VI), 3.4 and 74 ng L(-1) for As(III) and Cr(III), respectively, with an enrichment factor of 5 and a sampling frequency of 8h(-1). The relative standard deviations (R.S.D.) were 3.1, 4.0, 2.8 and 3.9% (C=1 ng mL(-1), n=7) for As(V), As(III), Cr(VI) and Cr(III), respectively. The proposed method was successfully applied for the analysis of inorganic arsenic and chromium species in mineral water, tap water and lake water with the recovery of 94-105%. In order to verify the accuracy of the method, two certified reference of GSBZ50027-94 and GSBZ50004-88 water samples were analyzed and the results obtained were in good agreement with the certified values. The ordered mesoporous Al2O3 coated capillary showed an excellent solvent and thermal stability and could be re-used for more than 30 times without decreasing extraction efficiency.

Determination of organochlorine pesticides in water using solvent cooling assisted dynamic hollow-fiber-supported headspace liquid-phase microextraction

The organic solvent film formed within a hollow fiber was used as an extraction interface in the headspace liquid-phase microextraction (HS-LPME) of organochlorine pesticides. Some common organic solvents with different vapor pressures (9.33-12,918.9 Pa) were studied as extractants. The results indicated that even the solvent with the highest vapor pressure (cyclohexane) can be used to carry out the extraction successfully. However, those compounds (analytes) with low vapor pressures could not be extracted successfully. In general, the large surface area of the hollow fiber can hasten the extraction speed, but it can increase the risk of solvent loss. Lowering the temperature of the extraction solvent could not only reduce solvent loss (by lowering its vapor pressure) but also extend the feasible extraction time to improve extraction efficiency. In this work, a solvent cooling assisted dynamic hollow-fiber-supported headspace liquid-phase microextraction (SC-DHF-HS-LPME) approach was developed. By lowering the temperature of the solvent, the evaporation can be decreased, the extraction time can be lengthened, and, on the contrary, the equilibrium constant between headspace phase and extraction solvent can be increased. In dynamic LPME, the extracting solvent is held within a hollow fiber, affixed to a syringe needle and placed in the headspace of the sample container. The extracting solvent within the fiber is moved to-and-fro by using a programmable syringe pump. The movement facilitates mass transfer of analyte(s) from the sample to the solvent. Analysis of the extract was carried out by gas chromatography-mass spectrometry (GC-MS). The effects of identity of extraction solvent, extraction temperature, sample agitation, extraction time, and salt concentration on extraction performance were also investigated. Good enrichments were achieved (65-211-fold) with this method. Good repeatabilities of extraction were obtained, with RSD values below 15.2%. Detection limits were 0.209 microg/l or lower.

Application of solid-phase microextraction in analytical toxicology

Solid-phase microextraction (SPME) is a miniaturized and solvent-free sample preparation technique for chromatographic-spectrometric analysis by which the analytes are extracted from a gaseous or liquid sample by absorption in, or adsorption on, a thin polymer coating fixed to the solid surface of a fiber, inside an injection needle or inside a capillary. In this paper, the present state of practical performance and of applications of SPME to the analysis of blood, urine, oral fluid and hair in clinical and forensic toxicology is reviewed. The commercial coatings for fibers or needles have not essentially changed for many years, but there are interesting laboratory developments, such as conductive polypyrrole coatings for electrochemically controlled SPME of anions or cations and coatings with restricted-access properties for direct extraction from whole blood or immunoaffinity SPME. In-tube SPME uses segments of commercial gas chromatography (GC) capillaries for highly efficient extraction by repeated aspiration-ejection cycles of the liquid sample. It can be easily automated in combination with liquid chromatography but, as it is very sensitive to capillary plugging, it requires completely homogeneous liquid samples. In contrast, fiber-based SPME has not yet been performed automatically in combination with high-performance liquid chromatography. The headspace extractions on fibers or needles (solid-phase dynamic extraction) combined with GC methods are the most advantageous versions of SPME because of very pure extracts and the availability of automatic samplers. Surprisingly, substances with quite high boiling points, such as tricyclic antidepressants or phenothiazines, can be measured by headspace SPME from aqueous samples. The applicability and sensitivity of SPME was essentially extended by in-sample or on-fiber derivatization. The different modes of SPME were applied to analysis of solvents and inhalation narcotics, amphetamines, cocaine and metabolites, cannabinoids, methadone and other opioids, fatty acid ethyl esters as alcohol markers, gamma-hydroxybutyric acid, benzodiazepines, various other therapeutic drugs, pesticides, chemical warfare agents, cyanide, sulfide and metal ions. In general, SPME is routinely used in optimized methods for specific analytes. However, it was shown that it also has some capacity for a general screening by direct immersion into urine samples and for pesticides and other semivolatile substance in the headspace mode.

Determination of methylmalonic acid and glutaric acid in urine by aqueous-phase derivatization followed by headspace solid-phase microextraction and gas chromatography-mass spectrometry

In this work, a novel technique of aqueous-phase derivatization followed by headspace solid-phase microextraction and gas chromatography-mass spectrometry was developed for the determination of organic acids in urine. The analytical procedure involves derivatization of organic acids to their ethyl esters with diethyl sulfate, headspace sampling, and GC/MS analysis. The proposed method was applied to the determination of methylmalonic acid and glutaric acid in urine. The experimental parameters and method validation were studied. Optimal conditions were obtained: PDMS fiber, extraction temperature 55 degrees C, extraction time 30 min, and 60 microL of diethyl sulfate as derivatization reagent with 2 mg of the ion pairing agent tetrabutylammonium hydrogensulfate. The method was linear over three orders of magnitude, and detection limits were 21 nM for methylmalonic acid and 34 nM for glutaric acid, respectively. Consequently, in-situ derivatization/HS-SPME/GC/MS is an alternative and powerful method for determination of organic acids as biomarkers in biological fluids.

Applications of solid phase microextraction for the determination of metallic and organometallic species

This paper reviews recent developments of solid phase microextraction (SPME) and its application to the analysis of organometallic species of lead, arsenic, mercury, tin, and selenium by hyphenation with HPLC-GC-atomic spectrometry. In the first part, a background of the technique is given in terms of derivatization, fibers used, extraction and desorption conditions. The second part summarizes typical SPME applications to the determination of organometallic species and the main experimental conditions with the aid of specific examples. Most of the applications comprise alkylation with NaBEt4 and headspace extraction followed by gas chromatographic separation with a suitable detector.

Determination of chromium(III) in water by solid-phase microextraction with a polyimide-coated fiber and gas chromatography-flame photometric detection

A method for the determination of trace Cr(III) in aqueous solution by solid-phase microextraction (SPME) coupled with gas chromatography (GC)-flame photometric detection (FPD) was developed. Aqueous Cr(III) was first converted to the volatile chromium trifluoroacetylacetonate (Cr(tfa)3) by derivatization with 1,1,1-trifluoroacetylacetone (Htfa), followed by SPME extraction using a polyimide-coated silica fiber. The distribution constants (K) of derivatized cis- and trans-Cr(tfa)3 between the polyimide phase and aqueous phase were 2012 and 2214, respectively. The two Cr(tfa)3 isomers extracted can be efficiently separated by a DB-210 GC column within 9 min. Selective detection of Cr was performed by a FPD equipped with a 385-nm long-pass filter. Linearity (r> 0.99) over the concentration range 5-300 ng ml(-1) Cr was obtained and the limit of detection was 2 ng ml(-1) Cr. The relative standard deviation was 7% at 10 ng ml(-1) Cr (n = 5). Applicability of this method to water analysis was tested by analyzing the chromium content in a reference standard water sample and an industrial effluent.

Miniaturization in sample treatment for environmental analysis

The increasing demand for faster, more cost-effective and environmentally friendly analytical methods is a major incentive to improve the classical procedures used for sample treatment in environmental analysis. In most classical procedures, the use of rapid and powerful instrumental techniques for the final separation and detection of the analytes contrasts with the time-consuming and usually manual methods used for sample preparation, which slows down the total analytical process. The efforts made in this field in the past ten years have led to the adaptation of existing methods and the development of new techniques to save time and chemicals, and improve overall performance. One route has been to develop at-line or on-line and, frequently, automated systems. In these approaches, miniaturization has been a key factor in designing integrated analytical systems to provide higher sample throughput and/or unattended operation. Selected examples of novel developments in the field of miniaturized sample preparation for environmental analysis are used to evaluate the merits of the various techniques on the basis of published data on real-life analyses of trace-level organic pollutants. Perspectives and trends are briefly discussed.

Full automation of derivatization--solid-phase microextraction-gas chromatography-mass spectrometry with a dual-arm system for the determination of organometallic compounds in aqueous samples

The determination of organometallic compounds in aqueous samples by in-vial derivatization and headspace solid-phase microextraction (SPME)-gas chromatography (GC)-mass spectrometry (MS) has been fully automated using a Twin PAL dual-arm robotic system. Linearity, accuracy, sensitivity for a series of n-methyl, n-ethyl, and n-phenyl metal substituted chloride compounds of tin, lead, and mercury were investigated. The automated method was compared to similar manual methods and improved precision, speed and throughput was achieved. By originally programming the Twin PAL dual-arm system with the supplier's software (Cycle Composer, Version 1.5.0) the arms on the robot were only able to work in sequence. However, in order to have a flexible system and exploit time efficiently the robotic arms must work simultaneously. This was accomplished by programming the robot with the new software package called Cruise Control 4-2 for Twin PALs. Compared to Cycle Composer, Cruise Control 4-2 enhanced the speed and throughput of the automated system further. In addition, with a built-in crash prevention protocol and an improved user interface a more user-friendly system was obtained.

Multielemental speciation analysis of organometallic compounds of mercury, lead and tin in natural water samples by headspace-solid phase microextraction followed by gas chromatography–mass spectrometry

The development of a simple and rapid multielemental speciation method is described with the ultimate goal to simultaneously determine various organometallic compounds of mercury, lead and tin (inorganic mercury, methylmercury, trimethyllead, triethyllead, monobutyl-, dibutyl- and tributyltin) in natural water samples. The analytical method consists on the ethylation with NaBEt4, simultaneous headspace-solid phase microextraction (HS-SPME) of the derivatives and final gas chromatographic-mass spectrometric (GC-MS) analysis. After optimization of important process parameters, like SPME fiber coating, extraction time and extraction temperature, the analytical characteristics were evaluated. Detection limits in the low ng l(-1) level, linearity over three orders of magnitude and repeatability in the range of 3-20% were achieved for all compounds under study. The accuracy of the method in terms of average percentage recovery of the compounds in spiked river water and seawater samples was better than 90%. Finally, application of the proposed method to real natural aqueous samples enabled the simultaneous determination of all the compounds under study in seawater samples obtained from the marina area of Gijón (Asturias, Spain).

In vitro and in vivo dose-dependent inhibition of methylmercury on glutamine synthetase in the brain of different species

Glutamine synthetase (GS) catalyzes the synthesis of glutamine from glutamate and ammonia and is associated with ischemic injury and neurological diseases. We investigated whether the in vitro and in vivo exposure to methylmercury (MeHg) produce changes in GS activity in the brain of different species. The brain in rats and mice was dissected into different regions for GS assay. MeHg levels in the brain tissues and blood of mice treated 2, 4 or 10 mg/kg MeHg were determined by a gas-chromatography/mass selective detector. In vitro exposure of MeHg (0.1-100 μM) produced dose-dependent decreases of GS activity in rat brains with 50% inhibition occurred at 10-20 μM. MeHg was a more potent GS inhibitor in vitro in the rat brain than other GS inhibitors (e.g., methionine sulfoximine, kainic acid). These effects were further confirmed using purified GS of sheep brains. In vivo GS activity was also inhibited in the hippocampus of mice given 4 or 10 mg/kg of MeHg. In mice concentration ratios of brain tissues to blood were 0.05-0.14 at 24 h post-dose. These data showed that MeHg produced significant changes in GS activity, indicating that GS is an effective biomarker for MeHg exposure.

Headspace solid-phase microextraction procedures for gas chromatographic analysis of biological fluids and materials

Solid-phase microextraction (SPME) is a new solventless sample preparation technique that is finding wide usage. This review provides updated information on headspace SPME with gas chromatographic separation for the extraction and measurement of volatile and semivolatile analytes in biological fluids and materials. Firstly the background to the technique is given in terms of apparatus, fibres used, extraction conditions and derivatisation procedures. Then the different matrices, urine, blood, faeces, breast milk, hair, breath and saliva are considered separately. For each, methods appropriate for the analysis of drugs and metabolites, solvents and chemicals, anaesthetics, pesticides, organometallics and endogenous compounds are reviewed and the main experimental conditions outlined with specific examples. Then finally, the future potential of SPME for the analysis of biological samples in terms of the development of new devices and fibre chemistries and its coupling with high-performance liquid chromatography is discussed.

Current awareness

In order to keep subscribers up-to-date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of mass spectrometry. Each bibliography is divided into 11 sections: 1 Books, Reviews & Symposia; 2 Instrumental Techniques & Methods; 3 Gas Phase Ion Chemistry; 4 Biology/Biochemistry: Amino Acids, Peptides & Proteins; Carbohydrates; Lipids; Nucleic Acids; 5 Pharmacology/Toxicology; 6 Natural Products; 7 Analysis of Organic Compounds; 8 Analysis of Inorganics/Organometallics; 9 Surface Analysis; 10 Environmental Analysis; 11 Elemental Analysis. Within each section, articles are listed in alphabetical order with respect to author (6 Weeks journals - Search completed at 7th. June 2000)