Silver(I)-assisted reduction of Blue tetrazolium chloride (3,3′-(3,3′-dimethoxy[1,1′-biphenyl]-4,4′-diyl)-bis(2,5-diphenyl-2H-tetrazolium) dichloride, BTC) by semicarbazide hydrochloride (SCH) was investigated in water-chloroform medium. The obtained colored products can be used for the visual detection and sensitive liquid-liquid extraction–spectrophotometric determination of Ag(I). Under the optimum conditions the calibration curve (which can be best approximated by a third-order polynomial; R2=0.9990) has two linear segments. For Ag(I) concentrations up to 0.011 g/ml, the linear regression equation had an intercept that was statistically indistinguishable from zero. The limit of detection, limit of quantitation, and molar absorptivity coefficient at λmax=573 nm were 0.6 ng/ml, 2 ng/ml and 1.2×106 l/(molcm), respectively. The regression equation of the second linear segment (0.021–0.028 g/ml) was A = 200γ – 3.5 (R2=0.9989), where γ is the concentration in μg/ml. The relative standard deviation at the 22 ng/ml level (n = 5) was 3.8 %. The effect of concomitant ions was studied, and the analysis of real samples tested the applicability of the developed procedure.

Vidka Vassileva Divarova, Denitsa Dimitrova Kiradzhiyska and Kiril Blazhev Gavazov