Hyphenation techniques, for speciation

Principles and Characteristics The fastest growing area in elemental analysis is in the use of hyphenated techniques for speciation measurement. Elemental spe-ciation analysis, defined as the qualitative identification and quantitative determination of the individual chemical forms that comprise the total concentration of an element in a sample, has become an important field of research in analytical chemistry. Speciation or the process yielding evidence of the molecular form of an analyte, has relevance in the fields of food, the environment, and occupational health analysis, and involves analytical chemists as well as legislators. The environmental and toxicological effects of a metal often depend on its forms. The determination of the total metal content... 

The aim of this work was to investigate the arsenic mobilization from the tailings material (200 - 500 pg/g As) into the seepage water (up to 3.5 mg/L As) and the process of seepage water effluent forming an immobilized precipitate (up to 8 % As) in the creek. Different analytical methods for the determination of total concentrations and different sequential extraction methods as well as hyphenated techniques for speciation analysis were applied to follow the way of the arsenic in this environment. 

Figure 1.12 Species-selective hyphenated techniques for speciation analysis.

Microwave-induced plasma optical emission spectrometry (MIP-OES) is very sensitive for volatile species containing metals. Hence its use has been also proposed as a detector in the development of hyphenated techniques for speciation. GC MIP-OES has been successfully applied for the speciation of alkylmetal species of low molecular weight (Hg, Sn and Pb compounds) in many different environmental applications [23]. 

E. Dumont, F. Vanhaecke, R. Cornelis, Hyphenated techniques for speciation of Se in in vitro gastrointestinal digests of Saccharomyces cerevisiae, Anal. Bioanal. Chem., 379 (2004), 504D511. 

Lobinski, R., 1996. Hyphenated techniques for speciation analysis, status and trends. In Welz, B. (Ed.), CANAS 95 Colloquium Analytische Atomspektroskopie, Bodenseewerk. Perkin-Elmer, Ueberlingen, pp. 389-397. 

Trends in mass spectrometry focus on the improvement of instrumentation, of several techniques in order to minimize sample volume, to improve sensitivity and to reduce detection limits. This is combined with increasing the speed of several analyses, with automation of analytical procedures and subsequently reducing the price of analysis. A minimizing of sample volumes means a reduction of waste volume with the aim of developing green chemistry . Furthermore, new analytical techniques involve a development of quantification procedures to improve the accuracy and precision of analytical data. Special attention in future will be given to the development of hyphenated mass spectrometric techniques for speciation analysis and of surface analytical techniques with improved lateral resolution in the nm scale range. 

J. Szpunar, R. Lobinski and A. Prange, Hyphenated techniques for elemental speciation in biological systems, Appl. Spectrosc., 57, 2003, 102A-112A. 

R. Ritsema, Environmental applications of hyphenated techniques for the speciation of tin, arsenic and mercury (dissertation). University of Pau, 1997. 

Gas chromatography coupled with AAS has been the most popular hyphenated technique for the speciation of metals and organometals. Among different atomizer designs employed in coupling GC with AAS, electrothermal atomization, especially the electrother-mally heated quartz tube, is preferred because of its high sensitivity, simple operation, and low cost [6]. The quartz tube (—100 X 10 mm inner diameter) is usually constructed in house and wrapped with Nichrome resistance wire and ceramic isolation material. A thermocouple is attached to the surface of the quartz burner for temperature control (Fig. 1). If necessary, hydrogen and air can be supplied from side arms of the burner. The furnace can be heated to more than 1000°C by means of a variable transformer. 

Prange A and Schaumloffel D (2002) Hyphenated techniques for the characterization and quantification of metallothionein isoforms. Analytical and Bioanalytical Chemistry 373 441 53. Sanz-Medel A, Montes-Bayon M, and Fernandez Sanchez ML (2003) Trace element speciation hy ICP-MS in large hiomolecules and its potential for proteomics. A review. Analytical and Bioanalytical Chemistry 377 236-247. Suzuki KT (1991) Metallobiochemistry Part B, metallothionein and related molecules. In Riordan JF and VaUee BL (eds.) Methods of Enzymology, vol. 205, pp. 252-262. San Diego Academic Press. 

Without discussion, the tools most commonly used for trace element speciation analysis nowadays are hyphenated techniques , which is the coupling of more than one technique one or more of them facilitating the separation of the various forms of the element of interest and the other for the final sensitive and selective detection of the element. The main separation methods and detectors commonly used in hyphenated or coupled techniques for speciation analysis have been summarized in Figure 3. These species separation techniques can be coupled online or offline with the detector (usually an atomic spectroscopic detector). 

T. Perez-Corona, Y. Madrid-Albarran, C. Camara, and E. Beceiro. Living organisms as an alternative to hyphenated techniques for metal speciation. Evaluation of baker s yeast immobilized on silica gel for Hg speciation. Spectrochimica Acta Part B 53 321-329,1998. 

J. J. Berzas Nevado, R. C. Rodriguez Martin-Doimeadios, E. M. Krupp, F. J. Guzman Bernardo, N. Rodriguez Farinas, M. Jimenez Moreno, D. Wallace and M. J. Patino Ropero, Comparison of gas chromatographic hyphenated techniques for mercury speciation analysis, J. Chro-matogr. A, 2011, 1218(28), 4545-4551. 

Fig. 15.1. The state-of-the art toolbox with hyphenated techniques for element speciation analysis and metaUomics. The upper right section presents the tools of inorganic mass spectrometry. Reproduced from Ref. [21 ] with permission. WUey Periodicals Inc., 2006.

Applications Since the introduction of commercial GC-MIP-AES systems, organometallic analysis can be performed routinely, e.g. for speciation of organotin compounds used as PVC stabilisers [356], The hyphenated GC-AED technique can be used to improve the efficiency of additive analysis. While on the one hand... 

A hyphenated technique, the coupling of ion chromatographic separation (DX-100, DIONEX) and inductively coupled plasma mass spectrometric detection (ELAN-5000, PERKIN-ELMER) was used for the speciation... 

Szpunar, Lobinski el al. have reported on several hyphenated techniques (especially CE-ICP-MS and HPLC-ICP-MS) for elemental speciation in biological systems,51-54 describing e.g. the quasi-simultaneous determination of more than 30 selenopeptides using HPLC-ICP-MS. 

Transient signals are typically obtained in atomic spectrometry when samples are introduced by flow injection techniques or when the spectrometer is used as an element-specific detector in hyphenated techniques. Inductively coupled plasma mass spectrometry has nowadays become the detection technique of choice for multielement-specific detection in speciation as it allows multielemental... 

---