Determination of chromium content in hollow capsules by graphite furnace atomic absorption spectrometry - Master's thesis - Dissertation

Determination of Chromium in Hollow Capsules by Graphite Furnace Atomic Absorption Spectrometry

Key words: atomic absorption spectrometer; chromium content in hollow capsules; AA1800H; April 15, 2012, CCTV "Weekly Quality Report", the program "The Secret in the Capsule" revealed that some companies in Hebei treated leather waste with quicklime and produced industrial gelatin, which was then sold to companies in Shaoxing Xinchang to make medicinal capsules. These capsules eventually entered pharmaceutical companies and reached patients' bodies. Since leather is processed industrially, chromium-containing compounds are used, leading to excessive chromium levels in the final product. Testing found that 13 batches of drugs had chromium levels exceeding standards. Industrial gelatin primarily comes from leather, and the chrome tanning process (mainly using chromium oxide) has been dominant due to its effectiveness. Therefore, high chromium content is a key indicator distinguishing industrial from edible gelatin. The Chinese Pharmacopoeia 2010 edition sets strict guidelines for gelatin, including gel strength, pH, light transmittance, conductivity, sulfite, peroxide, loss on drying, ignition residue, chromium content, heavy metals, arsenic salts, and microbial limits. Some companies have been exposed for producing gelatin from blue suede, disregarding public health. Poor production conditions and substandard materials lead to high chromium content in capsules, which is highly toxic. Even low concentrations can cause chronic poisoning, lung diseases, and cancer. The pharmacopoeia limits chromium in medicinal gelatin to no more than 2 mg/kg. This method introduces a chromium detection solution for medicinal hollow capsules based on the 2010 Chinese Pharmacopoeia, offering reference for industry use. It also supports users with after-sales service and technical application, ensuring accurate and efficient testing. 1. Main Equipment and Consumables: - Atomic absorption spectrophotometer AA1800H (US Analysis Co., Ltd.) - Nitric acid (premium grade, Chinese medicine reagent) - Chromium standard solution (1000 ppm) - Ammonium dihydrogen phosphate (premium grade) 2. Sample Preparation: - Weigh about 0.5g of hollow capsules and place in a 100mL PTFE digestion tank. - Add 5–10 mL of concentrated nitric acid, mix, cover, and heat at 120–140°C. - After digestion, evaporate to dryness on a hot plate, filter, and dilute to 25 mL with 1% nitric acid. Prepare a blank sample similarly. 3. Instrument Analysis Conditions: - Lamp current: 4 mA - Graphite tube type: Pyrolytic coating - Wavelength: 357.9 nm - Injection volume: 20 µL - Slit: 0.2 nm - Matrix modifier injection: 5 µL - Lighting mode: BGC-D2 Heating Program: - Stage 1: 150°C for 30 sec (RAMP, Low Argon 0.32 L/min) - Stage 2: 250°C for 15 sec (RAMP, Low Argon 0.3 L/min) - Stage 3: 350°C for 10 sec (RAMP, Low Argon 0.7 L/min) - Stage 4: 400°C for 10 sec (RAMP, Low Argon 0.7 L/min) - Stage 5: 550°C for 5 sec (RAMP, High Argon 0.0 L/min) - Stage 6: 2200°C for 3 sec (STEP, High Argon 0.0 L/min) - Stage 7: 2300°C for 2 sec (STEP, Low Argon 1.0 L/min) For chromium detection in pharmaceutical capsules, the GB/T 5009.123-2003 standard applies. The method described here uses high-pressure digestion, which offers faster digestion, less pollution, and higher accuracy compared to dry ashing. Key words: atomic absorption spectrometer; chromium content in hollow capsules; aesthetic analyzer; AA1800H

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