比色法、薄层色谱法及高效液相色谱法在罗红霉素溶液稳定性研究中的比较

分别以水、人工胃液和人工肠液为介质配制了罗红霉素溶液，用比色法、TLC及HPLC法对上述三种溶液的稳定性进行了研究。三种方法均表明罗红霉素在水和人工肠液中是稳定的，而对于罗红霉素在人工胃液稳定性结果，比色法所得结论与TLC以及HPLC法相反。TLC及HPLC法鉴别发现，罗红霉素在人工胃液中不稳定，分别在2h和10min内就有分解产物出现。HPLC测定结果表明，在10min和2h分别有8.15%和62．02％的药物分解，而比色法则认为该药在168h仍稳定。比色法用于罗红霉素在人工胃液稳定性测定时出现假稳定结果，此现象说明分解产物和显色剂显色后对原形药物的比色法测定有严重干扰。因此，比色法不适用于罗红霉素在酸性条件下的稳定性研究及含量测定，同样可以推测，如果罗红霉素的分解产物仍具有抗菌活性，则微生物活也不适用于该药的含量测定及稳定性研究。

A Comparative Study on the Stability of Roxithromycin in Different pH Solutions by Colorimetry, TLC and HPLC

In the present study, roxithromycin solutions of different pH values were prepared with water, simulated gastric fluid (SGF) and simulated intestinal fluid (SIF). Stability of roxithromycin in the above solutions were determined separately by colorimetry, TLC and HPLC. All the three methods achieved an identical conclusion that this drug was stable in water and SIF. However, for the stability test of roxithromycin in SGF, the results obtained by colorimetry were contrary to those by TLC and HPLC. According to the results by colorimetry, this drug was stable in SGF for as long as 168 hours. However, when tested by TLC and HPLC, decomposition of this drug was found within 2 h and 10 min separately. According to the determination by HPLC, 8.15 % and 62.02 % of roxithromycin were decomposed in 10 min and 2 h in SGF, which can be explained like this: the decomposition products reacted with H2SO4 to form a solution with the same photo-absorptivity range as that of the original drug. Accordingly, colorimetry is not suitable for the assay and stability test of roxithromycin in acidic solution like SGF. Similarly, we also have reason to predict that microbacterial assay is not suitable for roxithromycin in acidic solution if the decomposition product still has antibacterial activities.