High Pressure Digestion-Atomic Absorption Spectrometry Determination of Chromium Content in Capsules Beijing Dongxi Instrument Co., Ltd. Abstract: According to the standard method of gelatin hollow capsules of the 2010 edition of the Chinese Pharmacopoeia, the high pressure digestion method was used to treat the samples, and the atomic absorption spectrophotometer-graphite furnace method was used to determine the chromium Cr content in the user‘s gelatin hollow capsules. The detection limit of the method is 0.47pg;, the relative standard deviation RSD is 2%, and the collection rate is 98%. The method is simple, accurate, easy to master, economical and applicable, especially suitable for users who are not equipped with a microwave digestion instrument. 1. Method Summary Chromium is an essential trace element for the human body. The lack or excess of chromium will cause serious harm to the human body and animals. An appropriate amount of chromium can increase the decomposition and excretion of cholesterol in the human body, and is an active component in the glucose energy factor in the body. The lack of chromium will affect the metabolism of sugars and lipids, but the excess of chromium will also have the risk of carcinogenesis. The determination of chromium is usually by colorimetry and atomic absorption spectrometry. Colorimetry has many interfering factors and complicated operations; atomic absorption spectrometry has the advantages of simple, rapid and accurate operation. This paper refers to the 2010 edition of "Chinese Pharmacopoeia" and the food detection method GB-T5009.123-2003 "Determination of Chromium in Food". The sample was dissolved by high pressure digestion method and tested by graphite furnace. Satisfactory results were obtained. Second, the preparation of reagents and standard solutions 2.1 reagent nitric acid (HNO3): superior pure water or deionized water chromium single element standard solution (national standard material research center) 2.2 standard solution preparation 2.2.1 preparation of chromium standard intermediate solution: absorption of 100uL concentration of 1000ug/mL chromium single element standard solution placed in a 100mL volumetric flask, 2mL nitric acid, diluted with deionized water to scale, to obtain a concentration of 1μg/mL chromium standard intermediate solution. 2.2.2 standard curve preparation: absorption of the above preparation of chromium standard intermediate solution 0, 0.25, 0.50, 0.75, 1.00, 1.50mL in a 50mL volumetric flask, add 1mL nitric acid, bandwidth evaluation with deionized water, formulated 0, 5, 10, 15, 20, 30ng/mL series. III. Instrument and working conditions Constant temperature drying oven High pressure digestion tank AA7003 atomic absorption spectrophotometer (equipped with Cr hollow cathode lamp, Beijing East-West Analytical Instrument Co., Ltd.) Instrument working parameters are as follows: Table 1 Host measurement parameters

Wavelength (lambda/nm) Lamp current (I/mA) Deuterium lamp current (I/mA) Spectral passband width (Delta lambda/nm) Background deduction 357.8721000.2 Deuterium lamp Table 2 Graphite furnace heating program

Id Step name Initial temperature Termination temperature Heating time Gas path auxiliary Gas path mode 1 Drying 408030 Open and close power 2 Drying 8012010 Open and close power 3 Gray 12080010 Open and close power 4 Gray 8008008 Open and close power 5 Gray 8008004 Close and close power 6 Atomization 270027003 Close and close power 7 Clear 280028003 Open and close power 8 Cooling 0025 Open and close power, 4. Analysis steps and analysis results 4.1 Sample preparation Weigh 0.5g sample (accurate to 0.0001g) in the PTFE inner tank, add an appropriate amount of HNO3, gently shake well, soak overnight, cover the inner cover, tighten the stainless steel jacket, put it in a constant temperature drying oven at 130 C for digestion, after digestion is complete, cool to room temperature, place the inner tank of the digestion tank on an electric hot plate and slowly heat it until the reddish-brown steam evaporates clean, and steam the solution to About 2~ 3mL, remove, cool, wash with 2% HNO3 and transfer into a 50mL volumetric flask, dilute to scale with 2% HNO3, shake well for later use, and make a blank reagent. 4.2 Determination The standard solution and sample solution were measured according to the working conditions of the instrument shown in the table above, and the injection volume was 10 μL. 4.3 Result Calculation X = (C-C0) N V 10-3/m In the formula: X - the content of chromium in the sample, in μg/g; C - the content of chromium in the digestive solution of the sample, in ng/mL; C0 - the content of chromium in the reagent blank solution, in ng/mL; N - the dilution multiple after sampling from the sample stock solution; V - bandwidth evaluation volume, in mL; m - the mass of the sample, in g. Three significant digits are reserved for the calculation results. 4.4 Standard curve and analysis results

Cr Curve equation: Curve equation: y = 0.0174 * x-0.0019 Linear correlation coefficient: 0.99998 Table 3 Standard recovery test data Sample name Sample solution content ng/mL Add standard amount ng/mL Actual detection results ng/mLRSD% collection rate (%) 1 #3.658.451.7972 #3.758.39293.8 V. Conclusion 1) In this paper, atomic absorption spectrometry-graphite furnace method (AAS) is used to determine chromium in hollow capsules. It has the advantages of accurate results, simple operation, fast and easy to grasp. It has been widely used in daily analysis of samples. 2) The minimum detection limit of this experiment: 0.47pg; collection rate: (93.8-97) %. Precautions: This experiment has high requirements for the nitric acid used. Before processing the sample, a blank reagent should be configured to test whether the Cr content is low and can meet the requirements of this experiment. References: [1] "Atomic Absorption Spectrometer Analysis Method" Beijing Dongxi Analytical Instrument Co., Ltd., 2008, 9 [2] "Chinese Pharmacopoeia" 2010 Edition [3] GB-T5009.123-2003 Food Hygiene Inspection Method, Determination of Chromium in Food [4] Kathryu J L, Steve J H, Microwave Digestion Procedures for Environment at Matrices [J], Anatyst, 1998, 123 (7): 103-133.