Improvements of Speciation Analyses in Environmental Matrices

The release of some organometallic compounds and other chemical forms of elements in the environment has led to great international concern because of their high toxicity. The validation of the analytical techniques became of paramount importance which led the Community Bureau of Reference (BCR) to decide on the organisation of a series of projects for the improvement of the quality of speciation analyses. In addition, it was found useful to discuss thoroughly the different sources of error likely occurring in speciation analyses and a workshop was organized for this purpose; the aim of this workshop was to discuss the state of the art of speciation determinations, to define use, applicability and necessity of determinations of element species, to investigate where limitations exist and discuss the work necessary to overcome these and to detect where techniques have sufficiently been developed to produce reliable and valuable results. This paper presents the organization of the workshop, its main issue and describe the state of the current BCR projects on speciation.Abbreviations AAS Atomic absorption spectrometry - CVAAS Cold vapour AAS - DPP Differential pulse polarography - ECD Electron capture detector - ETAAS Electrothermal AAS - FIA Flow injection analysis - FID Flame ionisation detector - FLUOR Spectrofluorimetry - FPD Flame photometric detector - GC Gas chromatography - HG Hydride generation - HPLC High performance liquid chromatography - HPLC-AES HPLC atomic emission spectrometry - INAA Instrumental neutron activation analysis - ICPAES Inductively coupled plasma AES - MS Mass spectrometry - QFAAS Quartz furnace AAS - RNAA Neutron activation analysis with radiochemical separation     

Recent developments in speciation and determination of organometallic compounds in environmental samples

Summary Recent developments in the techniques of speciation and determination of organometallic compounds in the environment are reviewed. There is an increasing trend in the use of high performance liquid chromatography as separation tool, and in the use of plasma-excited atomic emission spectrometry as detector. New techniques have been reported to overcome the historically difficult interface of HPLC to furnace AAS. There are also new techniques in the derivatization of ionic organometallic species for gas chromatography. Tandem analytical systems are getting more and more sophisticated, so are the sensitivity and specificity.     

Performance of NAA Methods in an International Interlaboratory Reference Material Characterization Campaign

An extensive database of analytical results from a recent biological matrix Reference Material Characterization Campaign permitted an intercomparison of the performances of various methods among each other and with "true" best estimate concentration values established for these materials. Six different variants of neutron activation analysis (NAA) methods were employed including: instrumental neutron activation analysis, instrumental neutron activation analysis with acid digestion, neutron activation analysis with radiochemical separation, neutron capture prompt gamma activation analysis, epithermal instrumental neutron activation analysis, and neutron activation analysis with preconcentration. The precision and accuracy performance of NAA-based analytical methods are compared with three other major techniques, atomic absorption spectrometry (AAS), atomic emission spectrometry (AES) and mass spectrometry (MS) for 28 elements in 10 natural matrix materials.     

Determination of some trace metals in water and sediment samples by flame atomic absorption spectrometry after coprecipitation with cerium (IV) hydroxide

A cerium(IV) hydroxide coprecipitation method was developed for the determination of some trace elements (Cu, Co, Pb, Cd, Ni) in aqueous solutions, water and sediment samples by flame atomic absorption spectrometry (AAS). Several parameters governing the efficiency of the coprecipitation method were evaluated including pH of sample solution, amount of carrier element, volume of sample solution and the effect of possible matrix ions The procedure was validated by the analysis of GBW 07309 standard reference material sediment and by use of a method based on a solid phase extraction.     

Trace and major element compositions of Black Sea aerosol

Instrumental neutron activation analysis (INAA), flame atomic absorption spectrometry (FAAS), flame atomic emission spectrometry (FAES), graphite furnace atomic absorption spectrometry (GF-AAS), ion chromatography (IC) and visible spectrometry (VIS) were used to determine the composition of atmospheric aerosols, collected at a rural site in the Western Black Sea Coast of Turkey. A total of 354 daily aerosol samples were analyzed for 46 trace and major elements and ions. Sample preparation, quality control procedures, instrumental operating conditions for INAA and source apportionment work is presented.     

Coupling of ultrasonic nebulization to flame furnace atomic absorption spectrometry—new possibilities for trace element determination

The use of ultrasonic nebulization (USN) with desolvation system for sample introduction in flame atomic absorption spectrometry (F AAS) and flame furnace atomic absorption spectrometry (FF AAS) with a nickel tube is described. Polytetrafluorethylene (PTFE) adaptors were built to replace the pneumatic nebulizer for USN-F AAS measurements. For USN-FF AAS analysis, an alumina injector allowed the direct introduction of the dry aerosol into the nickel tube. The analytical performance of both systems is shown for Ag, Bi, Cd, Cr, Cu, Mn, Pb, Sb, Se, Tl and Zn. The results demonstrate that a sensitivity gain of up to 39 times can be achieved using USN-FF AAS, mainly due to the increase in residence time and to the absence of dilution of the analyte by the flame gases, as the atomization takes place inside the nickel tube. However, elements that require higher atomization temperatures, such as Cr and Mn, are more efficiently determined using USN-F AAS. To evaluate the accuracy of the proposed methods for the determination of trace elements, five certified reference samples were analyzed, and good agreement was, in general, achieved between certified and determined values at a 95% confidence level. The relative standard deviation was frequently below 5%, demonstrating good precision, particularly for USN-FF AAS. In this sense, coupling of USN with F AAS and especially with FF AAS has proved to be simple, safe, with high precision and good accuracy, also maintaining some of the most important features of F AAS, such as the high analytical frequency and the low running cost.     

Certification of total mercury and methylmercury concentrations in mussel homogenate (Mytilus edulis) reference material, IAEA-142

Due to the increased demand for new reference materials certified for total and methylmercury (MeHg) a sample of mussel homogenate (IAEA-142) has been prepared. Thirteen experienced laboratories reported results for total Hg of which 9 laboratories also reported results for MeHg content. Laboratories reporting MeHg results used various isolation techniques (solvent extraction, saponification, acid leaching, ion-exchange separation, and distillation) and detection systems (cold vapour atomic absorption spectrometry (CV AAS), cold vapour atomic fluorescence spectrometry (CV AFS), gas chromatography with electron capture detector (GC/ECD) and HPLC with CV AAS detector). In the case of total Hg, most of the laboratories used acid digestion, only two used alkaline dissolution, followed either by CV AAS or CV AFS. One laboratory used neutron activation analyses with radiochemical separation. The data received were in good agreement. The value for total Hg was certified to be 126 ng/g, with a 95% confidence interval from 119 to 132 ng/g. For MeHg the certified value of 47 ng/g expressed as Hg was assigned, with a 95% confidence interval from 43 to 51 ng/g. Stability testing has shown that both total and MeHg are stable if samples are stored in a dry and dark place at room temperature. The sample is now available as a certified reference material and is, in particular, useful for quality control measurements of Hg and MeHg in mussel samples at low concentration levels. Received: 24 September 1996 / Revised: 20 November 1996 / Accepted: 8 December 1996     

Certification of total mercury and methylmercury concentrations in mussel homogenate (Mytilus edulis) reference material, IAEA-142

Due to the increased demand for new reference materials certified for total and methylmercury (MeHg) a sample of mussel homogenate (IAEA-142) has been prepared. Thirteen experienced laboratories reported results for total Hg of which 9 laboratories also reported results for MeHg content. Laboratories reporting MeHg results used various isolation techniques (solvent extraction, saponification, acid leaching, ion-exchange separation, and distillation) and detection systems (cold vapour atomic absorption spectrometry (CV AAS), cold vapour atomic fluorescence spectrometry (CV AFS), gas chromatography with electron capture detector (GC/ECD) and HPLC with CV AAS detector). In the case of total Hg, most of the laboratories used acid digestion, only two used alkaline dissolution, followed either by CV AAS or CV AFS. One laboratory used neutron activation analyses with radiochemical separation. The data received were in good agreement. The value for total Hg was certified to be 126 ng/g, with a 95% confidence interval from 119 to 132 ng/g. For MeHg the certified value of 47 ng/g expressed as Hg was assigned, with a 95% confidence interval from 43 to 51 ng/g. Stability testing has shown that both total and MeHg are stable if samples are stored in a dry and dark place at room temperature. The sample is now available as a certified reference material and is, in particular, useful for quality control measurements of Hg and MeHg in mussel samples at low concentration levels.     

Application of Ion Chromatography,Nuclear and Spectrochemical Techniques for Trace and Major Element Determination in Seaside Aerosols

Instrumental neutron activation analysis, flame atomic absorption spectrometry, flame atomic emission spectrometry, graphite furnace atomic absorption spectrometry, ion chromatography and visible spectrometry were applied to determine the compositions of atmospheric aerosols, which were collected at a rural site in the Western Black Sea Coast of Turkey. A total of 354 daily aerosol samples were analyzed for about 46 trace and major elements and ions. Sample preparation, quality control procedures, and instrumental operating conditions were reported. Most of the elements measured commonly by the above techniques have very large correlation coefficients and low intercept values indicating the agreement between the results.     

Molecular absorption spectrometry in flames and furnaces: A review

Molecular absorption spectrometry (MAS), originally developed in the 1970s, is a technique to determine non-metals in flames and graphite furnaces by monitoring the absorbance of diatomic molecules. Early studies employed low resolution instruments designed for line source atomic absorption, which provided a limited choice of analytical wavelengths, insufficient spectral resolution, and spectral interferences. However, the development of high-resolution continuum source atomic absorption spectrometry (HR-CS AAS) instrumentation has allowed the analysis of challenging samples for non-metals as well as some difficult elements to determine by AAS, such as aluminum and phosphorus. In this review, theory and analytical considerations for MAS are discussed. The principles and limitations of low resolution MAS are described, along with its applications. HR-CS AAS instrumentation is reviewed, emphasizing performance characteristics most relevant for MAS. Applications of flame and HR-CS GFMAS are reviewed, highlighting the most significant work to date. The paper concludes with an evaluation of the enhanced analytical capabilities provided by HR-CS MAS.     

Interferences in ultratrace speciation of organolead and organotin by gas chromatography with atomic spectrometric detection

Interferences in trace and ultratrace speciation analysis of organotin and organolead compounds in various samples by gas chromatography coupled with atomic absorption spectrometry (AAS) and/or microwave induced plasma atomic emission spectrometry (MIP AES) are investigated. Particular attention is given to the effects of matrix co-extractives and reagents impurities introduced during sample preparation. Their influence on the detection limits is discussed in terms of baseline noise level, blank value, formation of artefacts and signal suppression. Loss of column resolution during the analysis of some matrices is observed.     

Determination of trace impurities in electronic grade quartz: Comparison of inductively coupled plasma mass spectroscopy with other analytical techniques

An analytical procedure for the determination of uranium and thorium in the sub-ng/g range as well as of other trace elements in the ng/g to g/g range in high purity quartz samples is described. The results obtained by inductively coupled plasma mass spectroscopy (ICP-MS) are compared to those obtained by other analytical techniques (instrumental neutron activation analysis, INAA; flame atomic absorption spectrometry, AAS; Zeeman graphite furnace atomic absorption spectrometry, ZGFAAS; total reflection X-ray fluorescence analysis, TRFA; direct current arc optical emission spectrometry, DC-arc OES; and X-ray fluorescence analysis, XRFA). For the ICP-MS measurements, the decomposition of the samples is carried out with HF/HNO₃/H₂SO₄-mixtures. The results obtained by the different methods show reasonable agreement. For uranium and thorium, ICP-MS proves to be the most sensitive method: detection limits of about 50 pg/g can be achieved for both elements.Presented in part at the 1989 European Winter Conference on Plasma Spectrochemistry, Reutte, Austria     

Determination of Trace Elements in Aerosol Samples Collected on Polycarbonate Filters by Atomic Absorption Spectrometry

Abstract

The multi-element analysis of aerosol samples collected on polycarbonate filters and the wet digestion procedure in open vessel were investigated. The concentrations of Na, K, Ca, Mg and Zn were determined by flame atomic absorption spectrometry with a micro injection system while Cd, Pb, Cu, Ni and V were determined by graphite furnace atomic absorption spectrometry (AAS).

NIES N[ddot] 8 “Vehicle Exhaust Particulate” Certified Reference Material from the Japan Environment Agency was used to study the decomposition of the samples. Different treatments were applied in order to completely dissolve the aerosol samples. It was found that, from all the methods tested, attack with micro-quantities of HNO₃ and HCIO₄ in an air pressure digestion system was the best procedure for the determination of the elements by AAS.

The recommended method was appropriate for all elements and it was applied to real samples. Two nondestructive analytical techniques for the determination of Na, K, Ca, Mg, Zn and Pb have been compared with the proposed method: proton induced X-ray emission (PIXE) and neutron activation analysis (NAA). Results obtained by the application of these three techniques were similar.     

原子吸收及原子荧光光谱分析

本文是《分析试验室》期刊定期评述中关于原子吸收光谱 (AAS)及原子荧光光谱 (AFS)分析的第 9篇综述文章。文中对 2 0 0 0年 12月～ 2 0 0 2年 11月期间我国在AAS AFS领域所取得的主要进展进行评述。内容包括概述、仪器装置、火焰原子吸收光谱法、电热原子吸收光谱法、化学蒸气发生技术以及原子荧光光谱法等。收集文献 35 8篇。     

Determination of organotin compounds in marine sediments using graphite furnace atomic absorption spectrometry

Organotin compounds, especially tributyltin, began to cause concern 10 years ago due to a high toxicity towards marine organisms. Several methods of analysing organotin compounds in various matrices have already been developed to determine organotin species simultaneously, but these are quite expensive as special equipment and specialized staff are needed. A simple screening method, which determines the organic tin compounds in the sediment, has therefore been developed and validated. The method can easily be implemented in laboratories accustomed to tracelement analyses; the sediment is extracted by a two-phase extraction and the organic extract is analysed using graphite furnace atomic absorption spectrometry (GF AA.) The screening method has been validated using high-pressure liquid chromatography-inductively coupled plasma mass spectrometry (HPLC–ICP MS).     

Certified sediment reference materials for trace element analysis from the National Metrology Institute of Japan (NMIJ)

Two types of sediment reference material (NMIJ 7302-a and 7303-a) for trace elements analysis have been prepared and certified by the National Metrology Institute of Japan in the National Institute of Advanced Industrial Science and Technology (NMIJ/AIST). The original materials were collected from a bay near industrial activity in Kyushu (NMIJ CRM 7302-a; marine sediment) and from Lake Biwa (NMIJ CRM 7303-a; lake sediment). The sediment materials were air-dried, sieved, homogenized, packaged in 1000 glass bottles (60 g each), and radiation sterilized. Certification of these CRM for trace elements was conducted by NMIJ, where each element was determined by at least two independent analytical techniques. Isotope-dilution inductively coupled plasma mass spectrometry (ICP–MS) was applied for certification of all the elements except mono-nuclide elements such as As and Co. Other techniques such as ICP–MS with quadrupole mass spectrometry and sector-field mass spectrometry, inductively coupled plasma atomic emission spectrometry (ICP–AES), and atomic absorption spectrometry (AAS), were also used. Certified values have been provided for 14 elements (Sb, As, Cd, Cr, Co, Cu, Pb, Hg, Mo, Ni, Se, Ag, Sn, and Zn) in both CRM.     

Determination of methyl-and ethylmercury compounds using gas chromatography atomic fluorescence spectrometry following aqueous derivatization with sodium tetraphenylborate

Summary An analytical procedure is described for the determination of methylmercury and ethylmercury compounds in fish and sediment samples, using gas chromatography atomic fluorescence spectrometry following aqueous phenylation with sodium tetraphenylborate. The derivatization products were identified by gas chromatography mass spectrometry. The advantages of using phenylation with sodium tetraphenylborate over ethylation with sodium tetraethylborate are discussed. The validation of the analytical procedure was performed by analyzing standard reference material (DORM-2). Applications for the analysis of fish and sediment samples were carried out and compared to other techniques.     

Speciation of organotin in sediments by multicapillary gas chromatography with atomic emission detection after microwave-assisted leaching and solvent extraction-derivatization

Microwave-assisted leaching of organotin compounds from sediment samples followed by the simultaneous extraction-derivatization of the extracted species was revisited with the goal to compare the existing procedures, improve their recoveries and extend them to phenyltin compounds. The stability of butyl- and phenyltin compounds under microwave field, real recoveries of the whole analytical procedure, effect of the extraction solvent, and the necessity for an internal standard were evaluated using two candidate reference sediments. The combination of the optimized sample preparation procedure with multicapillary chromatography resulted in a rapid (2 min leaching + 5 min extraction-derivatization + 3 min chromatographic separation) and efficient analytical procedure for speciation analysis of organotin compounds in sediment samples. The detection limit achieved with a microwave-induced plasma atomic emission detector was 2 ng g^–1. Received: 27 July 1998 / Revised: 31 August 1998 / Accepted: 4 September 1998     

Sample treatment in chromatography-based speciation of organometallic pollutants.

Speciation analysis is nowadays performed routinely in many laboratories to control the quality of the environment, food and health. Chemical speciation analyses generally include the study of different oxidation state of elements or individual organometallic compounds. The determination of the different chemical forms of elements is still an analytical challenge, since they are often unstable and concentrations in different matrices of interest are in the microg l(-1) or even in the ng l(-1) range (e.g., estuarine waters) or ng g(-1) in sediments and biological tissues. For this reason, sensitive and selective analytical atomic techniques are being used as available detectors for speciation, generally coupled with chromatography for the time-resolved introduction of analytes into the atomic spectrometer. The complexity of these instrumental couplings has a straightforward consequence on the duration of the analysis, but sample preparation to separate and transfer the chemical species present in the sample into a solution to be accepted readily by a chromatographic column is the more critical step of total analysis, and demands considerable operator skills and time cost. Traditionally, liquid-liquid extraction has been employed for sample treatment with serious disadvantages, such as consumption, disposal and long-term exposure to organic solvent. In addition, they are usually cumbersome and time-consuming. Therefore, the introduction of new reagents such as sodium tetraethylborate for the simultaneous derivatization of several elements has been proposed. Other possibilities are based in the implementation of techniques for efficient and accelerated isolation of species from the sample matrix. This is the case for microwave-assisted extraction, solid-phase extraction and microextraction, supercritical fluid extraction or pressurized liquid extraction, which offer new possibilities in species treatment, and the advantages of a drastic reduction of the extraction time and the embodiment into on-line flow analysis systems. This new generation of treatment techniques constitutes a good choice as fast extraction methods for feasible species-selective analysis of organometallic compounds under the picogram level, that can be used for national regulatory agencies, governmental and industrial quality control laboratories, and consequently, for manufacturers of analytical instrumentation.     

Working Methods Paper: Certification of methylmercury compounds concentration in marine sediment reference material,IAEA-356

An intercomparison exercise was organized between seven laboratories using various isolation procedures (extraction, distillation, ion-exchange and alkaline digestion) and detection systems (CV AAS, cold vapour atomic absorption spectroscopy; CV AFS, cold vapour atomic fluorescence spectroscopy; GC, ECD, gas chromatography electron capture detector and HPLC with CV AFS detection) for determination of methylmercury compounds in sediment sample. All certification criteria were fulfilled and therefore the value for total concentration of methylmercury compounds was certified to be 5.46 ng g^?1, with a 95% confidence interval from 4.07–5.84 ng g^?1. The acceptable range, calculated as two times the confidence interval of the mean is therefore from 4.68–6.23 ng g^?1. This is the first sediment reference material ever to be certified for concentration of methylmercury compounds. Comparison of the data obtained by various methodologies has shown that the most critical step is the isolation of methylmercury compounds from binding sites. Acid leaching only cannot release methylmercury compounds quantitatively. Total release of methylmercury compounds could only be achieved by alkaline digestion or distillation. This simple intercomparison exercise has shown that since large numbers of laboratories world-wide are performing methylmercury compound analyses using various improved and specific separation methods and sensitive detection systems, certification of methylmercury compounds in different biological and environmental samples should not be a problem in the future.