FLOW-INJECTION FLUOROMETRIC-DETERMINATION OF TRACES OF CALCIUM IN BRINE

2-[(2-Amino-5-methylphenoxy)methyl]-6-methoxY-8-aminoquinoline-N,N,N',N'-tetraacetic acid (Quin 2) reacts with calcium ion to form a fluorescent complex (lambda(ex) 328 nm, lambda(em) 496 nm). Calcium in brine could be determined with Quin 2 in the presence of at least 24 mg l-1 magnesium with a simple flow-injection system. Highly concentrated sodium chloride solution (ca. 5 M) could be directly injected into the carrier containing 0.05 M piperazine-N,N'-bis(2-ethanesulphonic acid) (PIPES)-sodium hydroxide buffer. The relative standard deviation was 3.5% for twelve injections of 20-mu-g l-1 Ca. The detection limit of calcium was 3.4-mu-g l-1. The sensitivities were the same for samples not containing and containing sodium chloride. The method permits the determination of calcium in chlor-alkali brine.