Hyphenation techniques, for speciation analysis

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.

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. 

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... 

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. 

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). 

The nutritional, chemical, biological, and toxicological properties of a chemical element are known to be critically dependent on the form in which it occurs in food. The recognition of this fact has spurred the development of species-selective (speciation) analytical methods for food additives and contaminants. According to the IUPAC s dehnition, speciation analysis deals with the analytical activities of identification and/or measurement of the quantities of one or more individual chemical species in a given sample [1], The analytical approach is usually based on the combination of a chromatographic separation technique with an element-specif>c detection technique. The former ensures that the analyte compound leaves the column unaccompanied by other species of the analyte element, whereas the latter enables a sensitive and specil>c detection of the target element. Coupled (also called hyphenated) techniques have become a fundamental tool for speciation analysis and have been discussed in many published reviews [2D6]. 

The choice of hyphenated techniques available for speciation analysis in foods is schematically shown in Figure 16.1. In the most frequent cases a separation technique, for example, GC, HPLC, electrochromatography or GE, is combined with ICP-MS. 

Methods for Speciation Analysis in Human Milk Typically Using Hyphenated Techniques and Off-Line Combinations... 

K. Wrobel, S. S. Kannamkumarath, K. Wrobel, J. A. Caruso, Environmentally friendly sample pretreatment for speciation analysis by hyphenated techniques, Green Chem., 5 (2003), 250D259. 

The combination of flame AAS and gas chromatography represents probably the first example of a hyphenated technique used for speciation analysis [30]. It is particularly favorable since the analytes arrive at the detector already in the gaseous state. Interfacing is straightforward, and in most cases a simple heated transfer line is used to direct the analytes to the atomiser. However, despite its apparent simplicity, the design of such a transfer line is critical since peak broadening due to dead volumes, cold spots, or lack of chemical inertness have to be avoided. 

Figure 3 Possibilities of hyphenation of different separation techniques to different types of atomic detectors for speciation analysis. FAAS = Flame atomic absorption spectrometry QC = quartz tube concentrator.

CE)] with a sensitive and element-specific atomic detector (usually an atomic absorption, emission or mass spectrometer) have become fundamental tools for speciation analysis, as can be seen in a special journal issue devoted to such application. Some of the hyphenated techniques available for spedes-selective analysis in biological and environmental materials are schematically shown in Figure 1.12. The choice of hyphenated technique depends primarily on the objective of the research. Speciation analysis in environmental and/or biological samples faces two main challenges because of the usually low concentrations of the analytes (below 1 pgg ) and the complexity of the matrix itself. 

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 strong preference in speciation analysis is to use a separation step that can be combined with a detection step in an on-line system [45]. In such coupling, analytical selectivity relies on the application of different chromatographic or electrophoretic methods, while the use of atomic spectrometric techniques assures high sensitivity and f>t-for-purpose limits of detection (LoDs). However, hyphenated techniques with element-specif>c detection do not provide structural information on the species. If appropriate standards are available, the assignation of chromatographic peaks can be accomplished by spiking experiments. On the... 

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