The oxidation of Cu(II)/tetraglycine complex in borate buffer (pH=9.2) in aqueous medium, by dissolved oxygen is strongly accelerated by S(IV). The reaction is adequate for S(IV) determination as the concentration of (Cu(H-3G4)]−formed is proportional to SO32- concentration. The [Cu(H-3G4)]−presents a maximum absorbance at 365 nm (ε = 7400 mol−1.L.cm−1) and it was followed spectrophotometrically by flow injection analysis procedure. The detection limit was 7×10−6mol.L−1and the linear regression showed a standard deviation of 0.02% (n=5). Kinetics studies showed the catalytic effect of some transition metal ions, “which can be present in environmental samples, in the oxidation of S(IV). The pseudo-first-order rate constants were determined in the presence of formaldehyde.