Three pressurized mineralization procedures that permit subsequent flame atomic spectrometric determination of Ca, Fe, K, Mg and Zn in bovine blood plasma-containing cookies and in standard reference materials

Pressurized mineralizations done in Parr digestion reactors, heated by either convection or microwave irradiation, and in microwave-heated closed vessels with pressure relief valves, were used for the decomposition of bovine blood plasma-containing (BBPC) cookies, and of Chlorella and rice flour standard reference materials from the National Institute for Environmental Studies. These three alternative procedures were tested for their suitability to permit the subsequent flame atomic absorption spectrometric determinations of calcium, iron, magnesium and zinc and flame atomic emission spectrometric determination of potassium. No significant differences (p > 0.01) were observed between metal data obtained from the three decomposition procedures. For all metals, precision (R.S.D.) was better than 4%, for both the within- and between-run (day-to-day) precisions. Mineralization in convection-heated bombs required a considerable time, about 2 h. Digestion in Parr bombs heated by microwave irradiation was much faster (70 s). However, both pressurized mineralizations could only accept a maximum sample loading of 70 mg per bomb, which reduced the capability to adjust to the detection limits of the metals under consideration. Thus, these two pressurized mineralizations required to pool the digestion solutions to reach metal concentrations that could afterwards be detected spectrometrically. Contrarily, microwave-assisted mineralization in closed vessels with pressure relief valves (ca. sample size admitted > 500 mg) provided digestion solutions suitable for the posterior straightforward spectrometric determinations; unfortunately, this type of pressurized mineralization required a total mineralization time of > 50 min. Therefore, a compromise between analysis time and spectrometric detection should be established for the mineralization method of choice. The proposed procedures were used to establish the mean metal concentrations ( ± one S.D., μg g−1) as well as the ranges (μg g−1) found in the BBPC cookies: Fe 19 ± 4 (12–23), Ca 289 ± 9 (273–302), K 1861 ± 79 (1711–1950), Mg 175 ± 7 (164–187) and Zn 11 ± 2 (8–14). It was concluded that the pressurized mineralization procedures described permitted the adequate dissolution of the solid samples, leading to precise.