A substance was tested for Impurity A using liquid chromatography. 2 determinations were performed.
In the 1st chromatogram, Impurity A was not detected, i.e. no Impurity A peak was observed and in the 2nd chromatogram, Impurity A peak was observed with a value of 0.3%.
Is it correct to average the 2 readings to give 0.15% or should the test be repeated?
I don't think it is proper to average the two reading. I think the test should be repeated.
In this scenario, it is not correct to simply average the two readings of Impurity A, which were 0% and 0.3% respectively, to get a value of 0.15%. Averaging these two values would not accurately reflect the presence or absence of the impurity.
Liquid chromatography is a sensitive analytical technique that can detect and quantify impurities in a substance. In this case, the first chromatogram showed no peak corresponding to Impurity A, indicating that it was not detected. However, in the second chromatogram, a peak for Impurity A was observed with a value of 0.3%.
To determine how to proceed, it is necessary to understand the reasons behind the discrepancy between the two determinations. There are several possibilities to consider:
1. Analytical Error: It is possible that there was an error in the analysis of the second determination. This could be due to issues such as incorrect calibration of the instrument, improper sample preparation, or human error during the analysis.
2. Sample Variability: Another possibility is that the sample itself had some variability, resulting in a presence of Impurity A in the second determination. This could be due to factors such as sample heterogeneity or degradation over time.
To gain more confidence in the results, it is recommended to repeat the analysis to confirm the presence or absence of Impurity A. Repeat the test using the same sample, taking care to follow proper analytical procedures, and compare the results obtained. This repetition will help determine if the initial absence of Impurity A in the first chromatogram was accurate or if there was an error or variability in the second determination.
By repeating the test, you can validate the results and ensure the accuracy of the analysis, enabling you to make an informed decision regarding the presence or absence of Impurity A in the substance.