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800C Determination of Vanadium in Food by Oxidation of Methyl Violet by Oxidation of Potassium Periodate
This paper was completed by a researcher from the Department of Chemistry of Tangshan Teachers College to discuss the paper on the determination of vanadium in foods by potassium iodate oxidative methyl violet fading reaction. It was published in the important journal Journal of Nankai University.
A method for the determination of vanadium (V) in food by spectrophotometry was established. In the citric medium, vanadium (V) in food was determined according to the fading reaction of methyl violet by potassium periodate. The reaction medium and reagent dosage were studied. , reaction temperature and reaction time and other factors, simultaneously determine the apparent activation energy and apparent rate constant, and draw a working curve to determine the linear range and detection limit. Wet digestion and microwave digestion respectively to treat sweet potatoes, cucumbers and snow lotus The results were determined by spectrophotometry. The experimental results show that the determination wavelength is 583 nm. In citric medium, vanadium has a strong catalytic effect on the oxidation of methyl violet by potassium periodate. The best experimental conditions: 0.2 mol/L Citric acid 3.0 mL, 2× 10-2 mol/L potassium periodate 2.5 mL, 1.0× 10-4 mol/L methyl violet 3.0 mL, reaction temperature 90 °C, reaction time 10 min, The detection limit of the method was 1.98× 10-2μg/mL, the linear range was 0-1.0 μ g/(25 mL), the apparent activation energy of the catalytic reaction was 10.097 kJ/mol, and the apparent rate constant was 1.625× 10-3 s-1. Processing samples by microwave digestion High precision. Experimentally determined content of the samples did not exceed 120 mg / kg, sample vanadium (Ⅴ) contents are satisfactory.
In the citric acid medium, vanadium (V) strongly catalyzed the fading reaction of methyl violet by oxidizing potassium periodate, and established a spectrophotometric method for the determination of vanadium (V) in food. The experimental conditions were determined: 0.2 mol/L citric acid 3.0 mL, 2× 10-2 mol/L potassium periodate 2.5 mL, 1.0× 10-4 mol/L methyl violet 3.0 mL, reaction temperature 90 ° C, reaction time For 10 min, the detection limit of the method was 1.98× 10-2 μg/mL, the linear range was 0-1.0 μ g/(25 mL), and the apparent activation energy of the reaction was 10.097 kJ/mol. The apparent rate constant is 1.625× 10-3 s-1. The reaction is determined to be a first-order reaction. The quantitative basis for the determination of vanadium is determined by the method. The experiment uses wet digestion and microwave digestion on sweet potato, cucumber and snow lotus respectively. The pretreatment was carried out and determined according to the experimental method. The experimental results showed that the microwave digestion method was the best. The content of vanadium in the sample measured by this method did not exceed 120 mg/kg, and the vanadium content of the sample was all qualified. Microwave digestion treatment of samples and determination by spectrophotometry with good selectivity, high sensitivity and anti-interference energy The method is strong and easy to operate, and is used for the determination of vanadium in food. The recovery rate is 85.0%-97.0%, which indicates that the method has good feasibility.
Weigh 0.25 g of the uniformly mixed sample into the PTFE digestion tank of the cleaned microwave digestion apparatus, add different acid systems, mix and stand overnight. Cover the safety valve and put it into the microwave digestion system. According to the microwave digestion operation manual, set the analysis conditions of microwave digestion, set three experimental stages, and increase the temperature in sections, 120-150-180 °C in turn, set the time of each stage to 4 min, set the power to 1 200 W, set the pressure. After 1.0 MPa. digestion, remove the digestion tank, cool to room temperature, transfer the digested sample to the Erlenmeyer flask, and then heat on the electric furnace to remove the acid. The remaining sample is dissolved in deionized water, and the volume is reduced to In the 50 mL colorimetric tube, use this as the sample solution to be mixed and set aside.