Abstract
High-speed liquid chromatography (HSLC) was used for the stability test of ascorbic acid dipalmitate (AsA-DP) in ointments and ointment bases, under the following conditions: model, JASCO FLC-350; detector, UVIDEC-I; wavelength, 254 nm; column, ZORBAX ODS (4.6×250 mm); mobile phase, MeOH; flow rate, 1ml/min; pressure, 100kg/cm2; chart speed, 0.5cm/min (at room temperature). The extracted AsA-DP was directly injected into the HSLC column. The amount of AsA-DP was determined from the peak height on the chromatogram. Absorption ointment, hydrophilic ointment, hydrophilic petrolatum, and 14 kinds of ointment bases containing 1% AsA-DP were exposed to air at 40° where their stability to oxidation was measured with HSLC. The results were as follows:1) The decomposition in ointments and ointment bases was pseudo-first order. 2) AsA-DP in ointments was stable in order of hydrophilic petrolatum, hydrophilic ointment and absorption ointment. 3) AsA-DP in stearyl alcohol, cetanol, and sorbitan sesquioleate was unstable, while that in white petrolatum, liquid paraffin, and stearic acid was very stable. 4) The decomposition product of AsA-DP in ointments and ointment bases was ascorbic acid-6-monopalmitate.
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