Sample Preparation for Atomic Spectrometry

In a large number of atomic spectrometric methods sample preparation is required but depending on the method or sample introduction technique used, it can vary widely from a simple polishing step to a complete sample dissolution and subsequent analyte-matrix separation. 

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One unique type of MS, ICP-MS, needs to be discussed separately because it does not deal with molecular species, but with atomic ones. The inductively coupled plasma is a common atomization source for atomic spectrometry. This sample preparation/ sample introduction mode has been coupled with an MS to yield an instrument capable of trace level elemental analysis. Each element has a unique set of isotopes in known proportions. These can be used to quantify the element. In the case of elements with overlapping isotopic mass numbers, simple deconvolution can be used to give results for each. ICPMS has very low detection limits. 

M. C. Yebra and A. Green, Analytical method using ultrasound in sample preparation for the flow injection determination of iron, manganese, and zinc in soluble solid samples by flame atomic absorption spectrometry, J. Anal. Meth. Chem., 2012, doi 10.1155/2012/298217. 

At present the real strength of LA lies in the measurement of distribution patterns of minor and trace elements in solid samples with high spatial resolution. Homogeneity testing is an application of LA-ICP-MS. There is an increasing demand for the development and validation of accurate and robust analytical technologies for the determination of the chemical characteristics of polymeric products in support of industrial needs, EC regulations (e.g. Directive on toy safety) or research. Needs are particularly acute for techniques able to determine trace element contents in solids with a minimum sample preparation. For this purpose, laser ablation-based methods, such as LA-ICP-AES/MS and laser-induced plasma atomic emission spectrometry (LIP-AES, LA-AES or LIBS) have already... 

The very low Hg concentration levels in ice core of remote glaciers require an ultra-sensitive analytical technique as well as a contamination-free sample preparation methodology. The potential of two analytical techniques for Hg determination - cold vapour inductively coupled plasma mass spectrometry (CV ICP-SFMS) and atomic fluorescence spectrometry (AFS) with gold amalgamation was studied. 

The complex of the following destmctive and nondestmctive analytical methods was used for studying the composition of sponges inductively coupled plasma mass-spectrometry (ICP-MS), X-ray fluorescence (XRF), electron probe microanalysis (EPMA), and atomic absorption spectrometry (AAS). Techniques of sample preparation were developed for each method and their metrological characteristics were defined. Relative standard deviations for all the elements did not exceed 0.25 within detection limit. The accuracy of techniques elaborated was checked with the method of additions and control methods of analysis. 

ASTM. 1998c. ASTM E 1645. Standard practice for the preparation of dried paint samples for subsequent lead analysis by atomic spectrometry. American Society for Testing and Materials. 

Techniques for analysis of different mercury species in biological samples and abiotic materials include atomic absorption, cold vapor atomic fluorescence spectrometry, gas-liquid chromatography with electron capture detection, and inductively coupled plasma mass spectrometry (Lansens etal. 1991 Schintu etal. 1992 Porcella etal. 1995). Methylmercury concentrations in marine biological tissues are detected at concentrations as low as 10 pg Hg/kg tissue using graphite furnace sample preparation techniques and atomic absorption spectrometry (Schintu et al. 1992). 

A sample of CBI ceramic aggregate was prepared for elemental analysis by initially evaporating the sample to dryness in a mixture of concentrated hydrofluoric and sulfuric acids. The residue was then dissolved in hydrochloric acid and analyzed by atomic absorption spectrometry. Table 3 presents these results, and corresponding data from TTLC analyses of unfired and fired samples of the same material. 

Until now, little attention has been given to the analysis of ancient copper alloys with LA-ICP-MS. This type of material is usually analyzed with fast or instrumental neutron activation analysis (FNAA or INAA), particle induced X-ray emission (PIXE), X-ray fluorescence (XRF), inductively coupled plasma-atomic emission spectrometry or inductively coupled plasma-atomic absorption spectrometry (ICP-AES or ICP-AAS). Some of these techniques are destructive and involve extensive sample preparation, some measure only surface compositions, and some require access to a cyclotron or a reactor. LA-ICP-MS is riot affected by any of these inconveniences. We propose here an analytical protocol for copper alloys using LA-ICP-MS and present its application to the study of Matisse bronze sculptures. 

Wet chemical methods involve sophisticated sample preparation and standardization with National Bureau of Standards reference materials but are not difficult for the analytical chemist nor necessarily time consuming (Figure 1). The time from sample preparation to final results for various analytical methods, such as GFAA (graphite furnace atomic absorption), ICP (inductively coupled plasma spectroscopy), ICP-MS (ICP-mass spectrometry), and colorimetry, ranges from 0.5 to 5.0 h, depending on the technique used. Colorimetry is the method of choice because of its extreme accuracy. Typical results of the colorimetric analysis of doped oxides are shown in Tables I and II, which show the accuracy and precision of the measurements. 

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