Effect of purity of sodium dodecyl sulfate on dissolution testing results of candesartan cilexetil

Objective: To study the effect of sodium dodecyl sulfate( SDS) purity on dissolution testing results of candesartan cilexetil,so as to reveal the influence of the SDS purity and the proportion of mixed substances on the test result of dissolution. Methods: SDS was converted to dodecyl alcohol by refluxing with 25 m L of 0. 5mol·L- 1sulfuric acid solution and extracting with diethyl ether. Resulting dodecyl alcohol was determined by GC method. For the GC method,the HP- 5 column( 30 mm × 0. 53 mm,2. 65 μm) was adopted with the inlet temperature of 270 ℃,the FID detector temperature of 300 ℃,and nitrogen as the carrier gas. The flow rate was 3. 0 m L·min- 1,the split ratio 10∶ 1 with temperature programming starting at 80 ℃ kept for 1 min then increased to 260 ℃ at a speed of 10 ℃ · min- 1maintained for 3 min. The injection volume was 1 μL. Results: Four batches of SDS were prepared as the dissolution testing media. In the four media,the concentration of saturated candesartan cilexetil solution was determined as 6. 28 × 10- 3mg · m L- 1,11. 59 ×10- 3mg·m L- 1,6. 17 × 10- 3mg·m L- 1and 23. 36 × 10- 3mg·m L- 1,respectively. Conclusion: The ability of SDS to promote solubilization is related with its purity and the length of the carbon chain of the mixed substances. At the same purity level of SDS produced by different manufacturers,the solubility and the dissolution would be better with longer carbon chain.