Speciation analysis of triethyl-lead and tributyl-tin compounds in human urine by liquid-liquid extraction and gas chromatography microwave-induced plasma atomic emission detection

This work describes the development of a fast method for speciation analysis of triethyl-lead and tributyl-tin species in urine samples after in situ derivatization by tetraethyl- or tetrapropyl-borate reagents. The alkylation reaction is done in the aqueous and urine medium and the less-polar derivatives are extracted in hexane by liquid-liquid extraction. The species were extracted and the extract was efficiently collected from the aqueous phase after centrifugation. Finally, the organometallic species are separated by gas chromatography and determined from the emission signals of elemental lead and tin. Atomic lead and tin are formed from the organolead and organotin compounds during atomization of the column eluate in a microwave-induced helium plasma source. The simultaneous measurement of lead (Pb) at 405.780 nm and tin (Sn) at 303.419 nm was achieved by an atomic emission detector. Finally, the analytes were determined with satisfactory precision (<5%) and detection limits of 0.05 μg Pb/L and 0.48 μg Sn/L, respectively, when 10 mL of urine is extracted with 1 mL of hexane and 1 μL of extract is injected.     

Gas chromatography – inductively coupled plasma – time-of-flight mass spectrometry for the speciation analysis of organolead compounds in environmental water samples

The application of inductively coupled plasma – time-of-flight mass spectrometry for the speciation analysis of organolead compounds in environmental waters is described. Construction of the transfer line was achieved by means of a relatively simple and rapid coupling procedure. Derivatization of the ionic lead species was achieved by in-situ propylation with sodium tetrapropylborate; simultaneous extraction of the derivatized compounds in hexane was followed by separation and detection by capillary gas chromatography hyphenated to inductively coupled plasma–time-of-flight mass spectrometry. Detection limits for the different organolead species ranged from 10 to 15 fg (as Pb), corresponding to procedural detection limits between 50 and 75 ng L^–1, on the basis of a 50 mL snow sample, extraction with 200 μL hexane, and subsequent injection of 1 μL of the organic extract on to the column. The accuracy of the system was confirmed by additional analysis of the water samples by capillary gas chromatography coupled with microwave-induced plasma–atomic-emission spectrometry and the analysis of a standard reference material CRM 605 (road dust) with a certified content of trimethyllead.     

The determination of arsenic and selenium by HPLC combined with alternating current plasma detection and post-column hydride formation

A helium alternating current plasma detector in combination with HPLC has been evaluated for the determination of arsenic and selenium-containing compounds after post-column hydride generation. The construction, operation, and optimization of the system is presented. Detection limits for the compounds under study ranged from 45–60 pg/s. Determination of arsenic and selenium in spiked river water samples has been used to demonstrate the applicability of the technique.     

Speciation of alkyllead in aqueous samples with application of liquid membrane probe for extraction and preconcentration

Lead is known to be toxic, especially in its organic forms (organolead, OL). In the environment tetraalkyllead species are rapidly degraded by sunlight and atmospheric constituents like ozone or hydroxyl radicals. Such breakdown yields the soluble forms such as trialkyllead and dialkyllead and finally ionic lead species. The liquid membrane extraction probe (LMP) device has been developed and used as an extraction and preconcentration tool for the speciation analysis of organolead compounds by GC/MS. It allows analysis of OL species at low concentrations in complicated matrices of environmental samples. The effect of pH, stirring rate, and time that influence the extraction efficiency of OL extraction by the LMP method were optimized. The transformation of tetramethyllead in aqueous media at different concentrations of major ions K(+), Na(+), Ca(2+), Mg(2+), Cl(-), SO(4)(2-) and the application of LMP to environmental samples are presented. It was found that degradation of tetramethyllead takes between 24 and 37 days. The detection limit (LOD) of the method for all organolead species investigated is around 4.7 microg/L, with a limit of quantitation of 15 microg/L.     

Selective determination of organofluorine compounds by capillary column gas chromatography with an atmospheric pressure helium microwave-induced plasma detector

Fluorinated analogs of compounds typical of those found in metabolic and other biological studies are detected with high selectivity using a gas chromatograph/microwave-induced plasma detector (GC-MIPD), which permits fluorine-selective detection by monitoring the emission at 685.6 nm. Using the described atmospheric pressure helium-sustained plasma detector, the minimum detectable level, fluorine selectivity (relative to carbon), and linear dynamic range of this GC-MIPD system were determined to be 4.8 pg-F/s, 1060, and 5000, respectively. The utility of this GC-MIPD system for the selective detection of organofluorine compounds is demonstrated by its application in the analysis of the metabolic fate of a fluorinated substrate administered to a mixture of wheat germ phosphatase and potato apyrase, as well as by analysis of synthetic mixtures.     

Discovery of a transalkylation mechanism--identification of ethylmercury+ at a tetraethyllead-contaminated site using sodiumtetrapropylborate, GC-AED and HPLC-AFS

Although organolead as a gasoline additive is banned in most countries, contamination by organolead compounds is still present. Little is known about transformation reactions of organolead compounds and especially transalkylation reactions with other metals. Laboratory experiments to clarify transalkylation reactions between organolead and inorganic mercury, and investigations of sites, where organolead compounds were emitted, are reported. Under laboratory conditions, inorganic mercury is ethylated to ethylmercury+ in presence of tetraethyllead. These transalkylations take place very fast and almost completely. In soil samples from an industrial site contaminated with organolead compounds and inorganic mercury, EtHg+ was clearly identified in high concentrations (up to 46 mg Hg/kg dw). Furthermore, methylmercury+ was found in concentrations up to 27 mg Hg/kg dw. It is the first time, that a transethylation of an organolead compound to an organomercurial compound in the environment is reported. It must be assumed, that this transalkylation takes place at sites, where organolead compounds occur and Hg2+ is available. Thus, it will be necessary to assess the risk of these sites.     

Bioanalysis of Naproxen by High Performance Reversed Phase Liquid Chromatography with Photometric and Fluorimetric Detection

Abstract

Methods for the quantitative determination of NAPROXEN and its main metabolite in plasma and urine are described. The separation is based on reversed phase liquid chromatography with LiChrosorb RP 8 (5 μm) as the support and methanol/phosphate buffer pH 7 as mobile phase, in some cases with addition of tetrabutyl ammonium ion as ion-pairing agent to improve the chromatographic selectivity. With UV-detector and a simple filter fluorometer an extraction-evaporation procedure is used for both plasma and urine determinations, while the high selectivity and sensitivity of a sophisticated fluorescence detector permits the direct injection of diluted samples on to the column. Use of an internal standard improves the within-run precision (s_rel%), which for plasma determinations of NAPROXEN are - with UV-detection, 0.2 – 1.7% (range 10 – 40 μg/ml), with filter fluorometer, 2.4 – 5.9% (range 12 – 58 μg/ml), and with fluorescence detector, 0.8 – 4.1% (range 5 – 20 μg/ml).     

Rapid and sensitive gas chromatographic determination of diacetylmorphine and its metabolite monoacetylmorphine in blood using a nitrogen detector.

A quantitative gas chromatographic method for the determination of plasma concentrations of diacetylmorphine and its metabolite monacetylmorphine using an alkali flane detector (nitrogen detector) is described. Plasma samples (pH 9.0) containing ethylmorphine acetate as internal standard are extracted with benzene. The dried benzene extracts are analysed as their corresponding acetylated derivatives following treatment with trifluoroacetic anhydride-benzent (1:5). The nitrogen detector permits quantitation of narcotic levels down to 100ng/ml with detection as low as 20 ng/ml. The higher sensitivity and selectivity of the nitrogen detector are compared to those obtained in flame ionization detection. Species differences in the rate of conversion of diacetylmorphine to monacetylmorphine in vitro in blood are also presented.     

Discovery of a transalkylation mechanism – Identification of ethylmercury+ at a tetraethyllead-contaminated site using sodiumtetrapropylborate, GC-AED and HPLC-AFS

Although organolead as a gasoline additive is banned in most countries, contamination by organolead compounds is still present. Little is known about transformation reactions of organolead compounds and especially transalkylation reactions with other metals. Laboratory experiments to clarify transalkylation reactions between organolead and inorganic mercury, and investigations of sites, where organolead compounds were emitted, are reported. Under laboratory conditions, inorganic mercury is ethylated to ethylmercury⁺ in presence of tetraethyllead. These transalkylations take place very fast and almost completely. In soil samples from an industrial site contaminated with organolead compounds and inorganic mercury, EtHg⁺ was clearly identified in high concentrations (up to 46 mg Hg/kg dw). Furthermore, methylmercury⁺ was found in concentrations up to 27 mg Hg/kg dw. It is the first time, that a transethylation of an organolead compound to an organomercurial compound in the environment is reported. It must be assumed, that this transalkylation takes place at sites, where organolead compounds occur and Hg²⁺ is available. Thus, it will be necessary to assess the risk of these sites.     

Simultaneous determination of allopurinol and oxypurinol by liquid chromatography using immobilized xanthine oxidase with electrochemical detection

A novel liquid chromatographic method using an immobilized xanthine oxidase reactor and an electrochemical detector was developed for the simultaneous determination of allopurinol and oxypurinol in rat plasma, intestinal wash and bile. Xanthine oxidase was immobilized on 5-microns aldehyde silica (prepacked into a 2 mm x 10 mm cartridge) in a simple procedure. Allopurinol eluted from an analytical column was converted to oxypurinol in the enzyme reactor with the eluent as the reaction medium and detected with high selectivity using an amperometric detector with a glassy carbon electrode at the applied potential of +0.85 V. High specificity of the enzymatic reaction combined with selectivity of the electrochemical detection eliminated the need for an extensive sample preparation. The assay was linear in the range 15-500 ng/ml of rat plasma, intestinal wash and bile with a low limit of detection of 10 pg on-column (signal-to-noise ratio = 4) for both allopurinol and oxypurinol.     

Simplified derivatization method for the speciation analysis of organolead compounds in water and peat samples using in-situ butylation with tetrabutylammonium tetrabutylborate and GC-MIP AES

A simplified derivatization method for the speciation analysis of organolead compounds in environmental samples followed by gas chromatography-microwave induced plasma atomic emission detection is developed. An in-situ butylation using tetrabutylammonium tetrabutylborate in an acetate buffer medium of pH 4.0 with simultaneous extraction of the derivatized organolead species into hexane was performed; for the analysis of the peat samples, the desorption of the different species from the matrix by acid leaching was also included. Detection limits at the sub-ng L^–1 range, comparable to those achieved by Grignard-alkylation, were obtained for the different species. The accuracy of the method was confirmed by analysis of a standard reference material (BCR-CRM 605, road dust). Examples of applications for the analysis of tap water and peat are given. Received: 16 February 1998 / Revised: 25 May 1998 / Accepted: 29 May 1998     

In situ ethylation of organolead,organotin and organomercury species by bromomagnesium tetraethylborate prior to GC‐ICP‐MS analysis

An analytical method for simultaneous in situ ethylation, of organolead, organotin and organomercury compounds in aqueous samples was developed using a new derivatisation agent, bromomagnesium tetraethylborate (BrMgEt₄B). The determination of lead, tin and mercury compounds was done by species‐specific isotope dilution, derivatisation and GC–inductively coupled plasma MS (GC‐ICP‐MS) or by GC‐MS. The recovery and accuracy of the derivatisation were evaluated. The effect of pH and the relative quantity of derivatisation agent were studied.     

Evaluation of a radio frequency plasma for oxygen-selective detection in capillary gas chromatography

A radio frequency plasma detector for capillary GC has been modified for oxygen-selective detection. Purification of the plasma gas and purging of both ends of the discharge region with helium were crucial to minimizing oxygen background emission from impurities in the plasma. With a pure helium plasma, eluting hydrocarbons released oxygen from the discharge region resulting in interfering signals on the oxygen channel. These interfering signals were efficiently reduced by using a methane-doped (0. 15%) low power RF plasma (15 W) sustained in a high make-up flow (150 mL/min). With this plasma, a 10³:1 oxygen-to-carbon selectivity and a 100 pg oxygen/s detection limit were obtained. The detector was linear over three orders of magnitude. The detection system has been used to screen for oxygenated compounds in two environmental samples.     

Gas chromatography--inductively coupled plasma--time-of-flight mass spectrometry for the speciation analysis of organolead compounds in environmental water samples

The application of inductively coupled plasma--time-of-flight mass spectrometry for the speciation analysis of organolead compounds in environmental waters is described. Construction of the transfer line was achieved by means of a relatively simple and rapid coupling procedure. Derivatization of the ionic lead species was achieved by in-situ propylation with sodium tetrapropylborate; simultaneous extraction of the derivatized compounds in hexane was followed by separation and detection by capillary gas chromatography hyphenated to inductively coupled plasma-time-of-flight mass spectrometry. Detection limits for the different organolead species ranged from 10 to 15 fg (as Pb), corresponding to procedural detection limits between 50 and 75 ng L(-1), on the basis of a 50 mL snow sample, extraction with 200 microL hexane, and subsequent injection of 1 microL of the organic extract on to the column. The accuracy of the system was confirmed by additional analysis of the water samples by capillary gas chromatography coupled with microwave-induced plasma-atomic-emission spectrometry and the analysis of a standard reference material CRM 605 (road dust) with a certified content of trimethyllead.     

Organic fuelled flames in selective ionization detectors for chromatography

Summary The selectivities of two flame-based ionization detectors identified as a Remote FID (RFID) and a Flame Thermionic Ionization Detector (FTID) have been improved by introducing methane as a fuel for the flame. Both the RFID and FTID feature a detector struture in which the ionization polarizer and collector are located several centimeters downstream of an oxygen-rich flame, rather than immediately adjacent to the flame as in a flame ionization detector. The RFID detects long-lived negative ions produced in the flame by the combustion of lead, tin, phosphorus, or silicon compounds. The FTID re-ionizes and detects neutral electronegative products generated by combustion of nitrogen, halogen, or phosphorus compounds. An organic-fuelled RFID can detect 1 pg Pb (Sn, P)/sec with a selectivity of the order of 10⁶ versus hydrocarbons. An organic fuelled FTID is applicable to detection of compounds at nanogram and higher levels. FTID selectivity for PCB compounds in a transformer oil matrix is of the order of 10⁵1. The improved selectivity achieved by using an organic-fuelled flame is also applicable to the detection of phospholipid and other non-volatile N, P, or Cl compounds using an FID/FTID detector accessory for a TLC/FID analyser.     

Simplified derivatization method for the speciation analysis of organolead compounds in water and peat samples using in-situ butylation with tetrabutylammonium tetrabutylborate and GC-MIP AES

A simplified derivatization method for the speciation analysis of organolead compounds in environmental samples followed by gas chromatography-microwave induced plasma atomic emission detection is developed. An in-situ butylation using tetrabutylammonium tetrabutylborate in an acetate buffer medium of pH 4.0 with simultaneous extraction of the derivatized organolead species into hexane was performed; for the analysis of the peat samples, the desorption of the different species from the matrix by acid leaching was also included. Detection limits at the sub-ng L^–1 range, comparable to those achieved by Grignard-alkylation, were obtained for the different species. The accuracy of the method was confirmed by analysis of a standard reference material (BCR-CRM 605, road dust). Examples of applications for the analysis of tap water and peat are given. Received: 16 February 1998 / Revised: 25 May 1998 / Accepted: 29 May 1998     

Features of a micro-gas chromatograph equipped with enrichment device and microchip plasma emission detection (muPED) for air monitoring

A field portable gas chromatograph (GC) was constructed allowing the enrichment of organic solutes from air samples on a miniaturized chemical trap and the subsequent gas chromatographic analysis on a resistively heated capillary column. The heart of the system is an integrated chip-based plasma emission detector (muPED). As a non-selective detector, the sensitivity is similar to that of a flame ionization detector (FID). The detector shows good selectivity for phosphorus, sulfur and chlorine-containing compounds with relative selectivities of ca. 5 x 10(5) gP gC(-1), 50 gS gC(-1) and 10(2) gCl gC(-1). The lifetime of the plasma chip under air monitoring conditions exceeded 3000 analyses.     

Microplasma-based atomic emission detectors for gas chromatography

This paper is an update on the development of microplasmas as detectors for gas chromatography. Direct current (dc), alternating current (ac), and radio frequency (rf) microplasmas developed in recent years will be described with their significant analytical results, which mostly concern the detection of halogens and sulfur. New results will be added which employ a microhollow cathode discharge (MHCD) as excitation source. Emphasis will be given to this microplasma which has already been implemented as an element-selective detector for emission spectrometry and as ionization source for mass spectrometry. The possibility to use it as a multielement-selective detector for gas chromatography will be presented. A discussion of the published detection limits of all these microplasmas is given.     

Analysis of medazepam, diazepam, and metabolites in plasma by gas-liquid chromatography with electrolytic conductivity detection.

An improved electrolytic conductivity detector allowed the gas-liquid chromatographic analysis of medazepam, diazepam, and major metabolites in 2 ml plasma at concentrations of 20 microgram/l. The detector had a sensitivity limit of less than 1 ng (or 100 pg nitrogen) when operated in the nitrogen-selective mode and a nitrogen/carbon elemental selectivity ratio of greater than 100,000 compared to octadecane and cholesterol. Detector response when operated in various element-selective chemical modes was investigated, and its application to the analysis of the title compounds was compared to electron capture and flame ionization detection systems.