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Table. 2.

Table. 2.

Validated method specifications for LC-MS/MS for of DNA-TG quantification

Method specification Levels and materials tested and validated Results Acceptance criteria
Linearity 10-5,000 fmol TG/mg DNA R2 = 0.9987, regression equation: y= 0.0036 x-0.0014 R2 > 0.99
LLOQ 10 fmol TG/mg DNA S/N ratio 49, bias –1.2%, CV 5.6% S/N ratio > 10, bias < 20%, CV < 20%
Precision 80 fmol TG/mg DNA Within-run CV 3.4%, between-run CV 5.8% CV < 15%
800 fmol TG/mg DNA Within-run CV 4.9%, between-run CV 5.3%
Accuracy 50 fmol TG/mg DNA Bias 3.5% Bias < 15%
100 fmol TG/mg DNA Bias –3.2%
250 fmol TG/mg DNA Bias –10.4%
800 fmol TG/mg DNA Bias –1.5%
Selectivity Blank DNA < 20% of analyte and < 5% of internal standard Response area of LLOQ, < 20% of analyte and < 5% of internal standard
Carry-over Blank DNA after control sample at 5,000 fmol TG/mg DNA Response area < 20% of LLOQ Response area < 20% of LLOQ
Extraction recovery Pre-and post-SPE responses of e-TG Extraction recovery 85.7–116.2%, response area CV 5.1–12.1% Response area CV < 15%
Matrix effect Two linear calibration curves prepared in DNA and in distilled water whose slopes were compared Slope 1.007 for calibrators in DNA with deviation percentage range 0.72% to –7.24% and slope 1.010 for calibrators in distilled water with deviation percentage range –0.01% to –14.95% Deviation percentage < 15%

Abbreviations: DNA-TG, DNA-incorporated 6-thioguanine; TG, 6-thioguanine; e-TG, etheno-thioguanine; LC-MS/MS, liquid chromatography-tandem mass spectrometry; LLOQ, lower limit of quantification; R2, coefficient of linearity; S/N, signal to noise; SPE, solid-phase extraction.

Ann Lab Med 2021;41:145~154 https://doi.org/10.3343/alm.2021.41.2.145

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