ONLINE COATED COLUMNS FOR THE SPECTROPHOTOMETRIC DETERMINATION OF METALS BY CONTINUOUS-FLOW ANALYSIS

The immobilization of xylenol orange, 1-(2'-pyridylazo)-2-naphthol and sulfophenylazo)-2'-sulfo-4'-nitrodiazoaminobenzene disodium salt (Cad ion) on reversed-phase silica (C-16, C-8, phenyl, C-1, C=N) and capill ary tubes with a hydrophobic inner surface (C-6, C-phenyl, C-1) in the flow were studied. The flow system including a microcolumn or a capil lary tube for the determination of metal ions is suggested. Its versat ility and flexibility is provided by on-line coating of the sorbents o r inner surface of the capillary tubes. The procedures for the flow sp ectrophotometric determination of Cd, Co, Cu and Fe(III) in the range 8 X 10(-8)-3 X 10(-5) M with on-line preconcentration are suggested. T he preconcentration factors are up to 9 for the microcolumns and up to 19 for the capillary tubes. The throughput of the system is 19 sample s per hour. The method of simultaneous determination of two metals in the mixture (Cu(II) and Co(II), Co(II) and Fe(III), Fe(III) and Zn, Mn (II) and Pb(II)) in the range 1 X 10(-6)-7 X 10(-5) M at 30-60 samples per hour is developed.