Highly selective determination of total mercury(II) sub microgram per liter by β-cyclodextrin polymer solid-phase spectrophotometry using 1,3-di-(4-nitrodiazoamino)-benzene

A highly selective β-cyclodextrin polymer solid-phase spectrophotometric (β-CDPSPS) method is described for the determination of total mercury(II) sub microgram per liter. The methods are based on the chromogenic reaction of mercury(II) with 1,3-di-(4-nitrodiazoamino)-benzene (DNAAB) loaded on β-cyclodextrin polymer (β-CDP). In pH 10.0 borax buffer, Hg(II)-DNAAB complex on β-CDP gives a positive peak at 445 nm and a negative one at 545 nm. The absorbance was measured at two peaks and the net absorbance (As) was calculated between the difference of positive and negative peaks. The apparent molar absorptivity is 1.1 × 107 l mol−1 cm−1 (82-fold of it in solution) for 100 ml sample and the linear range of the determination is 0.062-250 μg l−1. The selectivity for coexistent ions was greatly improved, only silver(I) interfered with the mercury determination and the amount of the others was reduced 25-1000 times compared to previous solution method. The interference caused by silver(I) can be eliminated using tri-n-octylmethylammonium bromide as masking agent. The detection limit and the quantification limit were found to be 0.024 and 0.062 μg l−1, respectively. The relative standard deviation of ten replicate determinations of 5.0 μg mercury(II) in 100 ml sample was of 2.4%. The method was validated by analyzing the water and soil reference materials and successfully applied to the determination of mercury(II) in locally collected water and dust samples.