Analysis of High Solid Content in Biological Samples by Flame Atomic Absorption Spectrometry

Abstract

The analysis of organic samples by flame atomic absorption spectrometry (FAAS) involves the difficulties of the digestion step. This fact was partially overcome by the use of the microwave assisted digestion technique (Skip, 1998). The digestion of the samples has the analytical advantage of an appropriated presentation for the analysis by different techniques. Nevertheless it has some disadvantages as could be analyte losses, risk of contamination, higher cost, longer analysis time and obligatory dilution of analyte, in some cases to undetectable levels (Bugallo et al, 2007; Marco and Hernandez, 2004). It is desirable the development of methods those avoid the sample digestion step. The technique of flow injection atomic absorption spectrometry is well suited for this purpose (Trojanowicz, 2000), in the determination of elemental levels in slurry samples and high solid content samples. It allows to the analysis of solid samples in a simple manner. (Arroyo et al, 2002; Koleva and Ivanova, 2008). The analysis of slurry samples gives the advantage of a liquid while allowing the introduction of a solid. The slurry method is reported for the analysis of prior dried samples (Januzzi et al, 1997; Da Silva et al, 2006; Mokgalaka et al, 2008), precalcined (Andrade et al, 2008). The analysis by FAAS of solid samples or high solid content samples, as could be crude clinical samples is not frequently found in the literature. It is reported the use of slurries from crude tissues combining the FAAS technique with nebulization with a Babington type nebulizer for the introduction of high solids content samples (Mohamed and Fry, 1981; Fry and Denton, 1977). Brandao et al, 2011 reported a simple and fast procedure for the sequential multi-element determination of Ca and Mg in dairy products employing slurry sampling and high resolution-continuum source flame atomic absorption spectrometry (HR-CS FAAS). The main experimental conditions optimized were 2.0 mol L−1 hydrochloric acid, sonication time of 20 min and sample mass of 1.0 g for a slurry volume of 25 mL. The elements were determined using aqueous standards for the external calibration with limits of quantification of 0.038 and 0.016 mg g−1, respectively. The precision expressed as relative standard deviation varied from 2.7 to 2.9% for a yogurt sample containing Ca and Mg concentrations of 1.40 and 0.13 mg g−1, respectively.