1. Determination of iodine in kelp by Indigo Carmine oxidation fading spectrophotometry. Iodine is known as the “intellectual element” and is one of the essential trace elements for the human body. The iodine content in healthy adults is about 30 mg. Its main function is to promote energy metabolism and heat production in the human body, and promote physical and brain development. Iodine deficiency in early childhood will cause brain development to lag behind in varying degrees, thereby affecting intelligence. , and this effect is irreversible. Excessive eating can also cause goiter and hyperthyroidism. Experts and scholars have found that the IQ of students in high-iodine areas is significantly lower than that in iodine-appropriate areas. Adults should not take more than 2,000 μg of iodine per day, otherwise potentially dangerous goiter will occur. The food sources of iodine are mainly salt, seafood, vegetables and dairy products, etc. It is very meaningful to study and determine trace iodine in kelp.
2 Indigo Carmine Catalytic Fading Spectrophotometric Determination of Cobalt. The use of cobalt to catalyze the oxidative fading reaction of dye-based chromogenic agents has been reported in the determination of trace cobalt in environmental testing, life sciences, food, and medicine. Cobalt was determined using the fading reaction of oxidized acid blue 74. Acid blue 74 (5,5′-indigo sodium sulfonate) reagent, a dye-based chromogenic agent, is a reversible redox reaction system in aqueous solution. In a solution with a pH value < 8.0, its redox potential can be expressed by the following formula :
The pH value of the experimental system is 7.8. Under this condition, the redox pair of the transition metal ion as the catalyst is intermediate between the redox pair of the reactant, that is, XHO-2/OH- > XCo(OH)3/Co( OH )2> XIo /Ir , indicating that Co2+ is the catalyst of this reaction system, and the reaction mechanism is as follows:
The linear range of this method is 0～1.0μg/25 mL, the detection limit is 9.92×10- 7 g/L, and the apparent activation energy of the reaction is 8.66 k J/mol l. Analysis, the result is satisfactory.
3. Determination of protein by Indigo Carmine resonance Rayleigh scattering method. Protein is the material basis of life, and its determination is of great significance in medicine, pharmacy, life science and food nutrition. The photochemical analysis methods for protein determination mainly include absorptiometry and fluorescence analysis. In recent years, Resonance Rayleigh Scattering (RRS), as a new analytical technique, has been widely used in the analysis of biological macromolecules such as proteins and nucleic acids. Based on the aggregation of dye chromophores on biomacromolecules, resulting in strong resonant light scattering.
Studies have shown that the enhancement of RRS signal is related to the molecular weight and electrical properties of proteins. In systems where electrostatic interactions dominate, proteins are positively charged when the pH of the solution is less than the protein’s isopoint. Anionic dyes and proteins combine to form complexes through electrostatic interaction, that is, dyes accumulate on proteins to form larger particles, which generate strong RRS enhancement signals. Using the resonance light scattering technique, the resonance light scattering signal at 393 nm is significantly enhanced through the interaction between protein and acid blue 74 in the medium of pH 2.34, and the enhancement degree is proportional to the protein content. method.
In B-R buffer solution at pH 2.34, the resonance Rayleigh scattering (RRS) of Indigo Carmine and protein are very weak. But when the two are combined, the formed complex can sharply enhance the RRS signal, and the maximum scattering wavelength is 393 nm. The linear ranges of human serum albumin, bovine serum albumin, γ-human globulin and ovalbumin are 0.1~3.7, 0.08~3.0, 0.05~2.0, 0.1~2.4 mg/L respectively; the corresponding detection limits are respectively 24.6, 20.7, 20.4, 25.7 μg/L. This method is used for the determination of total protein in human serum, milk, soybean milk, and urine, and the results are consistent with the classic Coomassie brilliant blue method.