Keywords
milk
flame atomic absorption spectrometry
flow-injection analysis
How to Cite
Abstract
A flow-injection system with sample and reagent addition by the synchronousmerging 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.
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