Calibration of a dissolution apparatus is necessary to produce accurate results for dissolution testing of pharmaceutical dosage forms and to allow comparison between batches and between laboratories. USP requirements for calibration are given in the Apparatus Suitability Test in USP <711> Dissolution.1 Each individual apparatus (i.e. spindle or basket) must be tested with disintegrating type and non-disintegrating type USP dissolution calibrators. The calibrator tablets available from the USP-NF include prednisone, (50 mg, disintegrating type) and salicylic acid (300 mg, non-disintegrating type). The test involves determining the percentage of drug that dissolves in 900 mL dissolution medium under specified conditions (50 or 100 RPM) after a specified time interval (30 minutes). The apparatus is deemed suitable if the results are within the acceptable range stated in the certificate for the calibrator (i.e the specifications sheet for that particular lot number of calibrator).
USP <711> specifies that both prednisone and salicylic acid are to be measured by UV spectrophotometry (242 nm and 296 nm) by comparison to a standard solution of known concentration. (Compendial requirements for UV spectrophotometry are given in USP <851> Spectrophotometry and Light Scattering.2)
This application note describes how spectrophotometric analyses for dissolution calibration can be quickly and conveniently carried out in a 96-well format using the SPECTRAmax PLUS microplate spectrophotometer. The PathCheck feature of the SPECTRAmax PLUS automatically corrects the results to a 1 cm pathlength, therefore samples read in a microplate give the same values that they would if read in a standard cuvette. Accurate pipetting of the samples into the wells is not necessary; indeed PathCheck corrects for pipetting errors. Using flexible custom formulas and the spreadsheet capability of SOFTmax PR