QUANTITATIVE-DETERMINATION OF CHLORIDE BY MEANS OF FLOW-INJECTION ANALYSIS WITH SPECTROPHOTOMETRIC DETECTION IN THE UV-VIS RANGE

Chloride is determined indirectly by spectrophotometric flow injection analysis. Two systems are compared, both based on the principle of io n exchange of easily detectable anions versus chloride from suitable m ercury salts. The first method is based on the exchange of chloride wi th chloranilate which is detected at 332 nm or at 306 nm in neutral or in acidic medium respectively. In the second case, chloride reacts wi th Hg(SCN)2. The liberated thiocyanate forms a strongly coloured compl ex with FE(III) in acidic solution with an absorption maximum at 460 n m. Both methods have a detection limit of about 5 mumol Cl-/l (175 ng/ ml). In the case of the thiocyanate method, the relative standard devi ation is about 2% (7 measurements) in the range of 5 to 150 mumol/l an d decreases significantly to a value of approximately 0.2% at higher c oncentrations; for the chloranilate method it is 10% for lower and abo ut 1% for higher concentrations respectively.