The ligand, 1-(1H-benzimidazol-2-yl)guanidine (GBI) gives two absorbance peaks at 245 nm and 295 nm respectively. GBI complexes with mercury(II) to form a white coloured complex. The analytical parameters such as effect of pH, reagent dosage, reaction time, effect of mercuric ion concentration, effect of interfering ions have been studied. The range of detection was determined to be 0.01 – 1000 μg/mL. The minimum detection limit is 10 ng/mL. The method is fairly sensitive and does not involve any preconcentration procedures. The method was appropriately validated using analytical procedures.