Improving Impurity Analysis in Photodiode Array Detection

When conducting impurity analysis of pharmaceuticals, researchers need to detect trace-level impurities along with the main ingredient, which is present at a high concentration. To accomplish this accurately requires a detector that provides linearity over a wide concentration range.
Furthermore, a high S/N (signal-to-noise) ratio is also required of the detector in order to provide high-accuracy quantitation of any impurities present at trace levels. Improving S/N might be achieved by increasing the sample concentration or injection volume, but increasing the sample concentration could decrease the solubility of the main ingredient, which is already present at a high concentration. Also, the common technique of increasing the solution temperature to facilitate dissolution of the main component may result in its decomposition.
Finally, if the injection volume is increased, peak shape distortion may occur due to the effect of the sample solvent. Therefore, to detect trace impurities at a reasonable sample injection volume and concentration range, a high-sensitivity detector is essential.

Here, we introduce our evaluation of the sensitivity and linearity obtained in impurity analysis using the new SPD-M30A photodiode array detector incorporated with a high-sensitivity flow cell with an 85 mm path length.