By Anonymous on Monday, March 22, 2004 - 05:14 am:
In a genral way: recovery is supposed to be as stated:
'Recovery experiments should be performed by comparing the analytical results for extracted samples at three concentrations (low, medium, and high) with unextracted standards that represent 100% recovery.'
In other way, we can determine recovery by using linearity data, and comparing the obtained area of chromatogram (=[(observerd area ratio with IS -,+ C)/M]. Where (Y= MX+ C)
My question is, is there any term like absolute and relative recovery?
How we can mathematically determine the recovery (first definition) comparing with working standard solution, and spiked plasma samples. For more clear, If I use 5ng working solution, and 1ml of plasma sample (spiked with 5 ng working solution) having both of same amount of injection volume. How I should I calculate recovery?
Hope some one can help me to understand.
Thanks in advance.
By Anonymous on Wednesday, March 24, 2004 - 05:39 am:
Recovery = (peak area of standard spiked in plasma / peak area of standard spiked in mobile phase) x 100. So the unit of calculation is %.
For example, if the condition for standard plasma preparation is "490 ul plasma (blank plasma, no standard in plasma) + 10 ul working standard solution" (the total is 500 ul), and then you do sample preparation (such as precipitation with acetronitrile and go on) and finally you inject with 50 ul to HPLC system. But the important thing is the final volume of sample being ready for injection is also 500 ul (such as after precipitation with acetronitrile, you dry your sample with nitrogen, then reconstitiute with 500 ul of mobile phase, and then inject with 50 ul volume).
The conditon for standard working solution spiked in mobile phase is "490 ul mobile phase + 10 ul working standard", then mix together, and directly inject with 50 ul volume to HPLC system.
After both injection, you get the peak area so you can calculate the recovery.