I am doing aflatoxin analysis in rice by hplc-fld
I have prepared same sample on two different days
Say One day i got 5 ppb Aflatoxin B1
Other day i got 7 ppb Aflatoxin B1
I am confused why i am getting such different concentration ?
Method is already validated and in use from long time
Are you running standards along with your samples? Did you recently check autosamoler injection reproducibility?
Yes i am running linearity everytime
No, i haven't checked autosampler injection reproducibility
Though my recovery for Spike sample is close to 100% everytime
I would inject the same sample three times and see how similar they are. What is the acceptable variability for your analysis?
Where was your sample stored prior to the prep for Aflatoxin analysis?
There are number of factors which can affect the interday variability. If method is validated even then sometimes we generally ignore the minor steps while taking care of major steps.
. One most important thing is the solution used for sample preparation. Is it the same which you used in previous day or freshly prepared. If same where it was stored (Some buffers need specific temperature), like to make sure it was at ambient temperature before use if you stored it at 4C or as specified.
. Sample storage before use or what was the temperature of the samples while running.
.When you prepared the mobile phase? fresh or previously used? If pH specific mobile phase then did you check the pH of previously used or fresh mobile phase
.Difference in concentration can also be due to vials, not properly washed vials or caps can influence the concentrations
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