Spiking volume [Bioanalytics]

posted by Ohlbe – France, 2015-09-17 12:45 (3507 d 06:07 ago) – Posting: # 15416
Views: 7,755

Dear Ladi,

❝ This is my first time posting here.


Welcome !

❝ What I understand we should have done is actually used the same volume of blank plasma and study samples. For example, we could use 500 uL of blank plasma and then spike with 20 uL or 50 uL of analyte solution. Then, what we should do is add 20 uL or 50 uL of diluent to all study samples too.


That would indeed be the best practice. Especially with a large spiking volume. Unfortunately, this practice is not that common.

❝ Also I understand that the %solution spiked into plasma should not be more than 5% (not sure where this number is from) [...]



Pure rule of thumb, AFAIK.

❝ [...] of total plasma volume. What i am not clear is 5% 'organic solvent' or 5% 'spiking solution'?


More than 5 % organic solvent is likely to denaturate proteins to some extent and can affect protein binding and recovery. More than 5 % spiking solution will dilute the sample, which may change recovery and matrix effects. If you add the same volume of diluent to all samples you will get the same effect in all your samples. But due to the possible combined effect of freeze/thaw I would still avoid higher spiking volumes.

Regards
Ohlbe

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