Does this analytical methods has an internal standard (IS) or QC sample, why is

Question

Does this analytical methods has an internal standard (IS) or QC sample, why is this so?

Analytical Method

Plasma imatinib concentrations were determined us- ing a high-performance liquid chromatography/tan- dem mass spectrometry (HPLC/MS/MS) assay.16 This method was validated for both monkey and human plasma. Plasma samples were prepared using a C18 solid-phase extraction procedure (3M Empore C8 ex- traction disk). Sample extracts were analyzed using reversed-phase chromatography with a Waters Sym- metry column (Waters Corp., Milford, MA) followed by detection with a Sciex API 3000 mass spectrometer (PE Biosystems, Foster City, CA). The lower limit of quanti- fication was 4 ng/mL, and the assay was fully vali- dated. The accuracy and precision from prestudy vali- dation were 97.8% ± 6.4% at the lower limit of quantification and 91.5%-102% ± 0.4%-8.2% over the entire concentration range of 1 to 10,000 ng/mL.

Explanation / Answer

Answer:

No, They havenot used any Internal standard (IS) or QC sample.

An internal standard in (analytical method) is a chemical substance that is added in a constant quantity to samples, the blank and calibration standards in a chemical analysis. Later, this substance can be used for calibration by plotting the ratio of the analyte signal to the internal standard signal as a function of the analyte concentration of the standards. Internal standard (IS) is need when we need to deal with large fluctuations which occur at different stages of the analytical method used. With an internal standard (IST) you can determine the amount of your analyte by the response factor (intensity ratio of IST and analyte.

In the given method the accuracy and precision has very low difference which is 97.8% ± 6.4% at the lower limit of quantification and 91.5%-102% ± 0.4%-8.2%. Thus, internal standard is not used here.

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