Stability Studies of Reactive Black 5 (RB5) Dye Standard Solution in Various Conditions Using UV–VIS Spectrophotometry

Abstract

Studies of Reactive Black 5 (RB5) dye in various conditions based upon azo functional group using a UV–VIS Spectrophotometry are described as part of method development using voltammetric technique. 20 and 200 mg/L concentrations of RB5 dye standard solutions were multiple scanned at maximum wavelength (596 nm). The absorbance of RB5 dye exposed to the ambient weather for 7 h a day for three consecutively days in 1 month time was measured. The average absorbance for three consecutive days of 20 mg/L RB5 dye ranged from 0.3589 ± 0.0073 to 0.3640 ± 0.0024 whereas for 200 mg/L was in the range of 3.5199 ± 0.0342 to 3.5643 ± 0.0481. Within 1 month, the absorbance range for 20 and 200 mg/L were from 0.3721 ± 0.0032 to 0.3769 ± 0.0032 and 3.4215 ± 0.0074 to 3.5361 ± 0.0180, respectively. Using dye solutions unexposed to the ambient, the average range of 20 and 200 mg/L RB5 dye was from 0.3470 ± 0.0045 to 0.3640 ± 0.0024 and 3.4290 ± 0.0187 to 3.5630 ± 0.0536 for 3 days measurement, respectively. The absorbance range was from 0.3577 ± 0.0036 to 0.3668 ± 0.0050 and 3.4246 ± 0.0213 to 3.5513 ± 0.0059 for respective concentrations within one month. Another stability studies have been performed by considering the effect of heat. The solutions were boiled and cooled to room temperature before measurements were made. The average range of 20 and 200 mg/L for three consecutive day measurement was 0.4013 ± 0.0022 to 0.4178 ± 0.0027 and 3.6837 ± 0.0191 to 3.6882 ± 0.0344, respectively. Finally, the impact of acid (pH 2.5) and basic medium (pH 9.0) to the absorbance of RB5 dye was carried out within 3 days. For RB5 dye with concentrations of 20 and 200 mg/L at pH 2.5, the average range was from 0.3493 ± 0.0029 to 0.3586 ± 0.0025 and 3.4904 ± 0.0225 to 3.5184 ± 0.0294 whereas for pH 9.0, the range was from 0.3515 ± 0.0043 to 0.3564 ± 0.0054 and 3.6007 ± 0.0296 to 3.6352 ± 0.0134, respectively. It was concluded that the RB5 dye standard solutions are stable in these four different conditions within 1 month time and the azo functional group of this dye which is electroanalytical active was not affected.