Hi,
I am currently reviewing a student's work, and they were advised to correct some of their calculations for % recovery of the spiked standards based on the recovery of one of the mid range calibration standards (2.5, 5, 10 15 ug/mL). So, where the spiked standard was say, 5 ug/mL of a hydrocarbon, the recovery from triplicate analysis was 4.65 ug/mL. With an increase in molecular weight and interference from high organic matrix, the spiked standard target analyte, a heavier non-polar compound was 3.25 ug/mL. From my own experience, I would run standards, compare recovery of internal spiked standard to the calibration curve standards and use that result. I am self trained organic soil chemist, so still learning.
Could anyone let me know, in what situations, adjusting for error associated with matrix interference is warranted, if warranted at all? So, if you had repeatable recoveries of 3.25 ug mL when spiking with 5 ug mL, could you obtain % recovery on the recovery - standard recovery is 3.25 ug/mL and in the sample, the associated native compound is 3.00. So 3.00/3.35 X 100.
Appreciate if anyone can assist with this matter.
Best regards,
Cal Leech
This really breaks down to two questions. The first issue is the presence of the matrix interference. The best way to address the impact of the matrix interference is to modify the method to minimize the matrix interference. Even before this the question that comes up is have you assured that the interference is not in fact actually some quantity of the compound that you are looking to quantify? As far as an approach to quantifying the recovery of the analyte is to use the method of standard additions. The sample would be homogenized, and aliquots of the net sample separated and different known quantities of standard added to different aliquots, with one or more having no standard added. Then process as normal. This still does not address the interference, which will appear as some quantity of analyte, but the recovery can then be addressed directly.
To evaluate matrix interference, you need to perform a series of experiments, each called Pre-Spike, Post-Spike, and Neat Blank. I should also note that it’s important to run everything at least 3 times. That way we know our results are reproducible and not just a fluke .
Source: https://sampleprep.biotage.com/blog/how-to-calculate-percent-recovery-and-matrix-effects-for-your-analytical-assays
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