SEQUENTIAL INJECTION SYSTEM IN FLAME ATOMIC-ABSORPTION SPECTROMETRY FOR THE DETERMINATION OF CALCIUM AND MAGNESIUM IN MINERAL WATERS

A flow set-up based on sequential injection analysis (SIA) is proposed to increase the versatility and robustness of routine flame atomic ab sorption analytical methods, Four procedures were selected to allow th e determinations of calcium within the ranges of 0.03-10.00 and 0.58-2 00.00 mg l(-1), and magnesium within 0.03-1.5 and 0.80-50.0 mg l(-1), in mineral waters. The sample aliquots inserted were 70.8 and 12 mu l for calcium and 13 and 12 mu l for magnesium. Moreover the system deve loped enabled to restrict the consumption of the releasing agent to re spectively 142 and 97 mu l in the determinations of calcium and to 26 and 12 mu l in the determinations of magnesium. The results obtained i n the analysis of 15 mineral waters were compared with those obtained by the corresponding conventional procedures yielding the equations: [ Ca mg l(-1)](SIA)=1.008(+/-0.004)[Ca mg l(-1)](conv.) -0.3 (+/-0.3) a nd [Mg mg l(-1)](SIA)=0.992(+/-0.006)[Mg mg l(-1)](conv.) +0.0 (+/-0. 1). In all cases the sampling rates achieved were higher than 110 h(-1 ), and reproducibility being better than 3%. (C) 1998 Elsevier Science B.V.