A rapid quantitative assay of intact paracetamol tablets by reflectance near-infrared spectroscopy

Near-infrared (NIR) reflectance spectroscopy was used to determine rapidly and non-destructively the content of paracetamol in bulk batches of intact Sterwin 500 mg tablets by collecting NIR spectra in the range 1100-2500 nm and using a multiple linear regression calibration method. The developed NI R method gave results comparable to the British Pharmacopoeia 1993 UV assay procedure, the standard errors of calibration and prediction being 0.48% a nd 0.71% m/m, respectively. The method showed good repeatability, the stand ard deviation and coefficient of variation for six NIR assays on the same b atch on the same day being 0.14 and 0.16% m/m, respectively, while measurem ents over six consecutive days gave 0.31 and 0.36% m/m, respectively. Apply ing the calibration to a parallel test set gave a mean bias of -0.22% and a mean accuracy of 0.45%. The developed method illustrates how the full pote ntial of NIR can be utilised and how the ICH guidelines which recommend the validation of linearity, range, accuracy and precision for pharmaceutical registration purposes can be applied. Duplicate determinations on bulk batc hes could be performed in under 2 min, allowing the potential use of the me thod on-line for real time monitoring of a running production process.