On-line trace matrix separation

When combined with solid-phase extraction, flow injection in flame AAS also enables on-line trace matrix separations to be performed. Here the matrix can be complexed and the complexes kept on the solid phase while trace elements pass on towards the atomizer. For the case of the trace analysis of Zr(>2, after dissolution it was thus possible to keep up to 4 pg of Zr as a TTA (thenoyltrifluoroacetone) complex on the column, while impurities such as Fe were eluted and determined with a high efficiency [133]. This opens up a new line of research on the use of on-line trace-matrix separations for any type of complex samples. 

The addition of oxygen was found to be helpful when nebulizing effluents from HPLC containing organic eluents such as acetonitrile. This was useful when using ICP-MS for on-line detection in speciation as well as in trace-matrix separations. Here, however, it is useful to use desolvation, even in the case of low consumption, high efficiency nebulizers, such as the HEN or DIHEN. This can be done efficiently with membrane desolvation using Nafion membranes [148]. 

Many different trace/matrix separation procedures are also applied prior to the ICP-MS determination, or even on-line (e.g. Muller and Heumann 2000). ID finds increasing application in combination with ICP-MS, thereby reducing the problems of analyte losses in sample preparation, but not the problem of interferences in the ICP-MS measurements (e.g., Yi and Madusa 1996) and that of contamination during sample preparation. Schuster and Schwarzer (1998) have described a new very versatile online capable column t/m-separation and preconcentration procedure for the selective separation and preconcentration of Pd even from solutions containing high concentrations of the other PGM. Moldovan et al. (2003) recently published another method for on-line preconcentration and determination of Pd using ICP-MS. 

Modifiers can be used very effectively in on-line SFE-GC to determine the concentration levels of the respective analytes. This presents an advantage in terms of the use of modifiers in SFE, since they appear as solvent peaks in GC separations and do not interfere with the target analyte determination. Although online SFE-GC is a simple technique, its applicability to real-life samples is limited compared to off-line SFE-GC. As a result, on-line SFE-GC requires suitable sample selection and appropriate setting of extraction conditions. If the goal is to determine the profile or matrix composition of a sample, it is required to use the fluid at the maximum solubility. For trace analysis it is best to choose a condition that separates the analytes from the matrix without interference. However, present SFE-GC techniques are not useful for samples... 

AAS with flames and furnaces is now a mature analytical approach for elemental determinations. However, its development has not yet come to an end. This applies to primary sources, where tunable diode lasers open new possibilities and even eliminates the requirement of using expensive spectrometers. It also applies to atom reservoirs, where new approaches such as further improved isothermal atomizers for ETAAS or the furnace in flame technique (see e.g. Ref. [326]) have now been introduced, but also to spectrometers where CCD based equipment eventually with smaller dimensions will bring innovation. Furthermore, it is dear that on-line coupling both for trace element-matrix separations and speciation will enable many analytical challenges to be more effectively tackeld. 

ICP-MS is a powerful technique for multi-element trace determinations in water samples. However, its application to the analysis of saline waters is limited to those with dissolved solid contents below 0.2%. in order to avoid instrumental drifts caused by solid deposition on the orifice. The analysis of sea water therefore demands a separation of the salt matrix prior to determination by ICP-MS. Beauchmin and Berman [19] used an on-line column packed with silica immobilized quinolin-8-oI ion-exchanger to separate the matrix and determine Mn, Co, Ni. Cu. Pb and U in the standard reference open ocean water NASS-2 using an isotope dilution technique and a standard addition method. 

Coedo, A.-G., Dorado, M. T., and Padilla, I. (2002) On-line ion-exchange matrix separation and inductively coupled plasma mass spectrometric determination of trace impurities in high-purity aluminium. J. Anal. At. Spectwm., 17, 502-6. 

Kozono, S., Takahashi, S., and Haraguchi, H. (2002) Determination of trace phosphorus in high purity tantalum materials by inductively coupled plasma mass spectrometry subsequent to matrix separation with on-line anion exchange/coprecipitation. Anal Bioanal Chem., 372, 542-8. 

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