Spectrophotometric Determination of Trace Mercury (II) in Dental – Unit Wastewater and Fertilizer Samples using the Novel Reagent 4-hydroxy-3-(2-oxoindolin-3-ylideneamino)-2-thioxo-2H-1,3-thiazin-6(3H)-one and the Dual - Wavelength β - Correction Spectrophotometry

A simple and low cost method for the determination of trace mercury (II) ions in dental – unit wastewater and fertilizer samples has been developed and validated. The method was based on the reaction of mercury (II) ions with the novel reagent 4-hydroxy-3-(2-oxoindolin-3-ylideneamino)-2-thioxo-2H-1,3thiazin-6(3H)-one, to form complex in the presence of Britton – Robinson (BR) buffer (pH4–6) which shows an absorption λ_{max at 505 nm}.The corrected absorbance of the formed complex at λ _max was obtained employing βcorrection spectrophotometric method. Beer's - Lambert law and Ringworm's plots of the colored Hg-reagent complex were obeyed in the concentration range 0.2− 2.0 and 0.32–0.96 μg mL⁻¹ mercury (II) ions, respectively with a relative standard deviation in the range of ±1.3–2.1%. The limits of detection (LOD) and quantification (LOQ) of the procedure were 0.026 and 0.086 μg mL⁻¹ Hg²⁺, respectively. The proposed method was applied for the analysis of mercury (II) in dental – unit wastewater and fertilizer samples. The validation of the developed method was tested by comparison with the data obtained by the inductively-coupled plasma- mass spectrometry (ICP-MS). The statistical treatment of data in terms of student's- t and variance ratio 'f-tests revealed no significance differences.