A comparison of flow injection methods for sulfide determination based on phenothiazine dyes produced from diverse aromatic amines |
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Authors: | Josué Carinhanha Caldas Santos Mauro Korn |
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Institution: | a Instituto de Química, Universidade Federal da Bahia, Campus de Universitário de Ondina, R. Barão de Geremoabo, s/n, 40170-290, Salvador, Bahia, Brazil b NQA/Departamento de Ciências Exatas e da Terra, Universidade do Estado da Bahia, R. Silveira Martins, 2555, Cabula, Salvador, 41195-001, Bahia, Brazil |
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Abstract: | In the present work a systematic comparison among spectrophotometric flow injection methods for sulfide determination based on phenothiazine dye production from diverse aromatic p-substituted amines were performed. The behavior of N,N-dimethylphenyl-p-diamine (DMPD), N,N-diethylphenyl-p-diamine (DEPD), phenyl-p-diamine (PPD), p-aminophenol (PAP) and other three aromatic amines was investigated and the chemical parameters of proposed flow methods were optimized by applying central composite design. For each evaluated method the concentration of amine, Fe3+ and H2SO4 was optimized and after the evaluation of reagents addition order the flow parameters were independently ascertained. Analytical signal was strongly diminished in the presence of iodide for flow methods based on the reaction of sulfide with DMPD, PPD or DEPD while fluoride was considered as an important interference for methods based on the reaction with PPD or PAP. The evaluated aromatic amines have permitted sulfide determination in a wide concentration range from 0.05 to 3.0 mg L− 1 and limits of detection (3σ) varying from 18.8 to 51.0 μg L− 1, for DEPD and PPD, respectively. The sensitivity of flow methods based on PPD and DMPD was higher even as PAP has permitted sulfide determination in a large sulfide concentration range. In addition, higher throughput was attained for DMPD method. The proposed methods were applied for sulfide determination in industrial wastewater and the obtained results were in agreement with reference method at 95% confidence level. |
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Keywords: | Sulfide determination Aromatic p-substituted amines Faced composite central design Flow injection analysis Wastewater analysis |
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