Direct determination of calcium in milk by atomic absorption spectrometry using flow-injection analysis

Abstract

A flow-injection system with sample and reagent addition by the synchronous merging zones approach for calcium determination in milk by flame AAS is proposed. Main parameters were optimized using a factorial design with central point. The optimum conditions were 2.5% (m/v) for La concentration, 8 mL min-1 for the carrier flow-rate, 20 cm for coiled reactor and 250 ìL for sample volume. Different sample preparation procedures were evaluated such as dilution in water or acid and microwave-assisted decomposition using concentrated or diluted acids. The optimized flow system was applied to determine Ca in eleven commercial milk samples and two standard reference materials diluted in water. Similar calcium levels were encountered comparing the results obtained by the proposed method (dilution in water) with those obtained using microwave-oven digestion. Results obtained in two standard reference materials were in agreement at 95% confidence level with those certified. Recoveries of spiked samples were in the 93% - 116% range. Relative standard deviation (n = 12) was < 5.4% and the sample throughput was 150 measurements per hour, corresponding to a consumption of 250 µL of sample and 6.25 mg La per determination.

Development and Validation of a Capillary Zone Electrophoresis Method for the Determination of Calcium in Composite Biomaterials

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Effect of milk fat content on absorption of calcium carbonate and calcium phosphate mixture in Sprague Dawley rats

“…The preparation of sample destruction was based on a method used by Moreno-Torrese et al (2000), Zafar et al (2003), Ayed and Thannoun (2006) and Petrovich et al (2007). On solid samples such as feed, milk and feces, drying and ashing at 550 o C were done until samples become white ash.…”

First Derivative Spectrophotometry for Simultaneous Determination of Iron and Calcium Using Bromopyrogallol Red.

“…Calcium is an essential macronutrient for humans, which represents approximately 2% of body weight in an adult person. This element has mainly a structural function in bones and teeth, and also to regulate many vital biological functions [8]. The iron content of milk is of physiological interest.…”