I would call this not acceptable. The drug could be to tightly bound too some plasma protein or the conditions (like pH) are too much different between the aqeous solution and plasma workup.

What is also interesting, do you obtain the same recovery from plasma in every experiment, with a high reproducebility?

I would recommend a maximum difference in recovery of 5-10% and results should be highly reproducible.

I would like to say that your recovery values are valid and honest. Low recovery case has been observed in lipoic acid (thioctic acid) determination (please see file; Lipoic acid Avidin). C.V. (coefficient of variation) of recovery less than 5% is desirable. Recovery values are total (bound-form and free-form) lipoic acid 16.5 ± 0.40% and free-form lipoic acid 69.8 ± 3.70%, respectively. Therefore, correction factors are used at 6.06 for total lipoic acid detemination and 1.43 for free-form lipoic acid determination, respectively.

Compounds or molecules containing sulphur atom (S) seem to give low recovery. Hydrophobic molecules should be extracted by using Folch’s solution (chloroform: methanol = 2 : 1 (v/v)).

By the way, HPLC-photometric assay such as shown in the above article is quantitative, but HPLC-MS is not quantitative.

Dear Urvesh,

You may refer to FDA Bioanalytical Method Validation guidance (May 2018): „The sponsor should optimize the recovery of the analyte to ensure that the extraction is efficient and reproducible. Recovery need not be 100 percent, but the extent of the recovery of an analyte and of the ISs should be consistent and reproducible.” Summing up, if the recovery is constant across your calibration range (within +/- 15%), then your method will produce reliable results.

Best regards,

Piotr

Dear patel,

same time it is acceptable but in recent past recovery should be between the extracted and post extracted. we should compare the extracted recovery with post extracted samples.for more details refer (what is post extracted) from FDA guidence for industry for bioanaltyical mehods. or can u call me at 8790807587 after 8.30 PM

Best Regards,

Madhusudhan.

50% recovery is accepatable as long as it is independent from the analyte concentration and, if protein binding may appear, is independent from the protein concentration of the plasma.

Thus, you should examine whether the recovery is constant, e.g. over the therapeutic concentration range of the drug and also for toxic concentrations and this for samples with low, normal, and increased plasma protein concentration.