應用鉻管柱固相萃取及火燄原子吸收光譜儀間接檢測抗壞血酸   全文下載

Application of Column Solid Phase Extraction of Chromium for Indirect Determination of Ascorbic Acid by Flame Atomic Absorption Spectrometry

本研究描述一種間接方法用以檢測果汁及維生素C 錠片中抗壞血酸含量。此法是根據下列原理：鉻（vI）與抗壞血酸進行還原反應產生鉻（III）， 未反應的鉻（vI） 經由Amberlite XAD-16 管柱分解成1,5-diphenilcarbazide 複合物，該複合物藉由10 mL 硫酸（0.05 mol/L）甲醇溶液沖提，最後利用火燄原子吸收光譜儀檢測。由鉻（vI）與抗壞血酸之反應量可換算出抗壞血酸之含量。檢測方法的最適條件，包括pH 及樣品溶液之體積，均被評估。干擾物在抗壞血酸回收的影響上亦被研究。抗壞血酸濃度範圍在0.5 - 20 μg/mL 之間時，本分析方法有最高的靈敏度與最佳的選擇性。此法具精確性，在五重複的12 μg/mL 抗壞血酸下，呈現3.4%的相對標準偏差。本法的準確性藉由分析實物添加抗壞血酸之測試，而與AoAC 方法（967.21 official Method）所檢測之結果比較。綜合顯示，本檢驗方法成功地應用在製藥、檸檬口味之清涼粉泡飲料及果汁上。實物上檢測抗壞血酸之相對誤差低於8%。"

An indirect method for the determination of ascorbic acid in fruit juice and vitamin C tablets by flame atomic absorption spectrometry was described. This method is based on the reduction of chromium (VI) to chromium(III) with the reducing action of ascorbic acid, separation of unreacted Cr(VI) as its 1,5-diphenilcarbazide complex on a column filled with Amberlite XAD-16, elution of the complex by 10 mL of 0.05 mol L-1 H2SO4 in methanol, and determination by flame atomic absorption spectrometry. Amount of the ascorbic acid was calculated from the amount of Cr(VI) reacted with ascorbic acid. The optimum conditions for the determination of ascorbic acid, including pH and volume of sample solution were examined. The effect of interfering species on the recovery of the ascorbic acid was also investigated. The proposed method allows high sensitive and selective determination of ascorbic acid in the range 0.5-20 μg/mL. The proposed method is precise as it provides relative standard deviation of 3.4% during five replicate determinations of 12 μg/mL of ascorbic acid. Accuracy of the procedure was tested by analyzing spiked real samples and applying 967.21 Official Method (AOAC) for the determination of ascorbic acid. The procedure described was successfully applied for the determination of ascorbic acid in pharmaceutical preparation, lemon flavored soft powder drink and fruit juices. Ascorbic acid has been determined in real samples with relative error lower than 8%.