Study on chromogenic reaction of molybdenum(VI) with 4-(2-thiazolylazo)-1,2,3-trihydroxybenzene and its application

The chromogenic reaction of molybdenum with the reagent 4-(2-thiazolylazo)-1,2,3-trihydroxybenzene in the presence of cetylpyridimium bromide has been studied in detail.Molybdenum reacts with the reagent to form a stable red complex(1∶2) in the medium of pH 1.6~4.2,The maximum absorption of the complex lies at 550 nm with the apparent molar absorptivity of 5.48×104 L·mo-1·cm-1.Beer′s law is obeyed in the range of 0-50 μg for molybdenum in 25 mL solution.Using NaF,ascorbic acid and mandelic acid as masking reagents to avoid interferences from Al3+,Fe3+and Ti respectively,the proposed method has been applied to the determination of molybdenum in alloy steel standard samples with relative standard deviation(RSD) of 2.18%-2.75% and the determination results are consisted with the certified values or those obtained by 5-Br-PADAP spectrometry.