Empower Tip: Review Window and the Processing Method

In this tip, we will review Peak Purity results for samples that have been spiked with different levels of an impurity. Remember from Tip 136 that the results for the Purity Angle vs the Purity Threshold and the Purity Plot should agree before making a conclusion regarding Peak Purity.

STEP 1 The first sample is ‘un-spiked’ and both the numerical results and the Purity Plot indicate that the peak is spectrally homogeneous.

The second sample was ‘spiked’ with an impurity at the 20% level. The numerical results and the Purity Plot indicate the peak is not spectrally pure and you can see from the Purity Plot that the impurity is near the tail of the peak.

The third sample was ‘spiked’ with an impurity at the 1% level. The numerical results indicate that the peak is spectrally pure, however, the Purity Plot sill indicates an impurity towards the tail of the peak.

If we compare the results of the Caffeine peak to the 2-Acetamidophenol peak, we see roughly the same Purity Threshold. However, the Purity Angle for Caffeine is approximately 3 times larger than the Purity Angle for the 2-Acetomidophenol. Given that the peaks are at roughly the same absorbance, we should expect similar Purity Angles. This is another indication that there is a problem with the Caffeine peak in this sample.

The last sample was ‘spiked’ at the 0.5% level. The numerical results indicate that the peak is spectrally pure, however, the Purity Plot indicates an impurity towards the tail of the peak.

The Purity Plot is a sensitive tool for detecting spectral differences across a chromatographic peak.

It’s that easy!