Fig. 3.

Accuracy of the in-house vitamin B6 assay in measuring the NIST standard reference material 3950. The top panel shows that measured results of PLP were about 19% lower than the NIST assigned value using the in-house assay with calibrator values assigned by absorbance measurement. After the calibrators were calibrated against the NIST SRM 3950, measured results of PLP matched the NIST assigned value with difference less than 5%. The Bottom panel shows that measured results of PA matched the NIST assigned value with or without the calibrators calibrating against the NIST reference standards.