Determination of Cadmium in Rice by Ultraviolet Spectrophotometer

Release time：2019-03-19

Cadmium is a heavy metal element, which is very important in metallurgy, plastics, electronics and other industries, but it will do harm to human body. According to different ways of intake, cadmium has different effects on health. The intake of cadmium through rice and other foods belongs to the "long-term low dose", which is mainly harmful to kidneys and bones. WHO safety standards for cadmium are based on toxicity to kidneys, with an upper limit of 7 micrograms per kilogram per week. This is equivalent to a person who weighs 60 kilograms and does not exceed 60 micrograms per day. For example, if a person weighing 60 kilograms eats 500 grams of rice with cadmium content of 0.15 mg per kilogram per day, such rice is qualified.



Based on GB/T 5009.15 "Determination of Cadmium in Food", the solution of cadmium detection in cereals is based on three sets of overall solutions, which are universal atomic absorption spectrophotometer, special cadmium detector and spectrophotometer. This scheme can meet the requirements of enterprise quality control and daily inspection of law enforcement and supervision departments in the production, storage, processing and circulation of grain industry chain. Among them, spectrophotometric detection solution_low cost_frontier technology. Strong practicability. Safety and environmental protection



The methods are as follows:



Preparation of HBBrPT



Reagent-2-hydroxy-4-n-butoxy-5-bromophenylacetone thiosemicarbazone was prepared by simple condensation of 2-hydroxy-4-n-butoxy-5-bromophenylacetone, which was prepared by standard procedure. The structure of the compound is given below (I).




Option 1. 2-hydroxy-4-n-butoxy-5-bromophenylacetone thiosemicarbazone.



The structure was obtained by infrared spectroscopy, nuclear magnetic resonance and mass spectrometry. The melting point of HBBrPT is 108-109 degrees Celsius. Preparation of Solution



Buffer solution was cultured with hydrochloric acid, acetic acid and sodium acetate in acidic preparation and medium of ammonium hydroxide and ammonium chloride.



Preparation of Metal Solution and Reagent Solution



The solution of cadmium (II) was prepared by the analytical reagent cadmium nitrate. The amount of cadmium (II) used in this solution is determined by EDTA14. A suitable amount of 2-hydroxy-4-n-butoxy-5-bromophenylacetone thiosemicarbazone was dissolved in benzene to prepare 0.0005 M reagent solution.



Thiosemicarbazone solution containing 5.62-16.86 ug/mL of cadmium (II), 10 ml of alkaline buffer solution with pH of 10 and 1 ml of 0.0005 M-2-hydroxy-4-n-butoxy-5-bromophenylacetone was volumetrized in 25 mL volumetric flask with distilled water. The absorbance of the solution was 440 nm compared with that of the blank reagent.



Shanghai Austrian UV1901PC ultraviolet-visible spectrophotometer is equipped with a 1 cm quartz pond for absorbance measurement. The PH meter is used to measure the pH.




RESULTS AND DISCUSSIONS



Cadmium (II) reacts with 2-hydroxy-4-n-butoxy-5-bromophenylacetone thiosemicarbazone under alkaline conditions to obtain yellow products. The colour reaction of cadmium (II) with reagent occurs instantaneously even at room temperature. The absorbance of the yellow product corresponds to the maximum wavelength at 440 nm and remains constant for at least one hour. The effect of pH value on absorbance was studied. It was found that the maximum value was formed when the pH value was 10.00. Ten times too much reagent is sufficient for complete colour development. In addition, whether the excessive reagents have adverse effects on the absorbance of reagents. The order in which various components are added shows the effect on absorbance. The analytical characteristics of cadmium by physicochemistry are shown in (II) - Table 1 of HBBrPT data. The molar absorptivity and Sandel sensitivity are 4035 mol-1 cm-1 and 0.02765 UG cm-2, respectively, when the linear correlation affecting cadmium (II) exists between the concentration of metal ions and the absorbance range of 5.62-16.86 mg/ml.



Table 1. Analytical Characteristics of Physicochemical and Cd(II)-HBBrPT



RESULTS AND DISCUSSIONS



Cadmium (II) reacts with 2-hydroxy-4-n-butoxy-5-bromophenylacetone thiosemicarbazone under alkaline conditions to obtain yellow products. The colour reaction of cadmium (II) with reagent occurs instantaneously even at room temperature. The absorbance of the yellow product corresponds to the maximum wavelength at 440 nm and remains constant for at least one hour. The effect of pH value on absorbance was studied. It was found that the maximum value was formed when the pH value was 10.00. Ten times too much reagent is sufficient for complete colour development. In addition, whether the excessive reagents have adverse effects on the absorbance of reagents. The order in which various components are added shows the effect on absorbance. The analytical characteristics of cadmium by physicochemistry are shown in (II) - Table 1 of HBBrPT data. The molar absorptivity and Sandel sensitivity are 4035 mol-1 cm-1 and 0.02765 UG cm-2, respectively, when the linear correlation affecting cadmium (II) exists between the concentration of metal ions and the absorbance range of 5.62-16.86 mg/ml.





Table 1. Physicochemical and analytical properties of Cd(II)-HBBrPT.



Characteristic results



PH 10



Maximum 440 nm of lambda



Yellow color



Molar absorptivity, Lmol-1cm-1 4035



State, UG cm-20.02765



The validity of Bill's law is ug/ml 28.10



Concentration range, ug/mL 5.62-16.86



Stability constant (K) 8.46X106



Standard deviation (S) 0.299



Go, K.



Cadmium (II) Metal Ionic Form