Determination of total selenium by multicommutated-flow hydride generation atomic absorption spectrometry. Application to cow's milk and infant formulae

Abstract

A multicommutated flow system was designed and evaluated for the determination of selenium by hydride generation atomic absorption spectrometry (HG-AAS). It was applied to the determination of total selenium in samples of cow's milk (fluid and powder) and infant formulae. Linearity was satisfactory in the range up to 27.5 mg L À1 (h ¼ 0.082 C + 0.0033, h ¼ peak-height, absorbance, C ¼ concentration in mg L À1 , r 2 ¼ 0.999). Detection (3s) and quantification (10s) limits in solution were LD ¼ 0.08 mg L À1 and LQ ¼ 0.27 mg L À1 , corresponding to LD ¼ 3.2 mg kg À1 and LQ ¼ 10.8 mg kg À1 in solid samples, and to LD ¼ 0.8 mg L À1 , LQ ¼ 2.7 mg L À1 in fluid milk samples. Trueness was verified by analysis (n ¼ 5) of two reference materials (NIST 1549, Non-fat Milk Powder and NIST 1846 Infant Formula). At the 95% significance level, results were statistically equivalent to the certified values. Instrumental precision (s r (%), n ¼ 5) was in the range 1.4% to 11.7%, analytical precision (s r (%), n ¼ 5) being 4.2 and 9.3% respectively for the determination of the above mentioned reference materials. The sampling frequency of the system was 160 hour À1 .

Determination of Total Selenium in Infant Formulas: Comparison of the Performance of FIA and MCFA Flow Systems

“…It was then cooled down to room temperature, 1 mL of 30% hydrogen peroxide was added, and the vial (loosely capped) was heated again for 2 minutes at 40% power. Afterwards, the contents of the vial were transferred quantitatively to a 50 mL Erlenmeyer flask containing 10 mL of 10% (w/v) sulfamic acid solution and 10 mL of concentrated HCl; the prereduction step was carried out by heating at gentle boiling on a hot plate for 1 hour and then cooled down to room temperature and diluted with water to 20.0 mL [ 29 ].…”

“…It has been already used by Ródenas-Torralba et al for the determination of tellurium in milk by hydride generation but coupled to atomic fluorescence detection [ 21 ]. In a previous work we developed and validated a multicommutated flow system for the determination of total selenium in milk and infant formulas [ 29 ].…”

“…The aim of this work is the comparison and evaluation of the performance of two flow systems based on different techniques: a FIA system developed, optimized, and validated, presented in this work and a MCFA system developed and validated in a previous work [ 29 ]. This comparison is proposed in order to investigate the benefits that either technique could provide for the determination of total selenium in infant formulas.…”

Automated method for the determination of total arsenic and selenium in natural and drinking water by HG-AAS

“…The flow system was described elsewhere (Pistón et al 2009). It was based upon a Gilson (Villiers-le-Bel, France) Minipuls 2 multichannel peristaltic pump and two 3-way 12 V solenoid valves (NResearch, West Caldwell, NJ, USA, model 161T031) which were used for fluid control.…”

“…Since MCFA is a microanalytical technique, methods based on it usually present low reactive consumption and generate low volumes of chemical residues. The literature reflects the usefulness of this technique that has been applied to the determination of different analytes in a wide range of matrixes (Knochen et al 2005;Pistón et al 2006;Sixto and Knochen 2009;Pistón et al 2009). …”