ISO 20636:2018 pdf free
ISO 20636:2018 pdf free.Infant formula and adult nutritionals – Determination of vitamin D by liquid chromatography-mass spectrometry
Vitamin D is sensitive to light. Perform all steps under low-level incandescent lighting. If exclusively vitamin D3 is required for analysis, then standards pertaining to vitamin D2 need not be used and vice versa. Calibration standards should be bracketed at the beginning and at the end of an analytical run.
Vitamin D2 stable isotope labelled stock standard solution, ρ≈10 μg/ml. Dispense the contents ofa 1 mg vial of d6-vitamin D2 (5.1.4) into a 100 ml volumetric flask. Dissolve in 90 ml of ethanol (5.1.10). To promote dissolution, sonicate if necessary. Mix thoroughly, make up to volume with ethanol (5.1.10). Measure the absorbance of an aliquot at 265 nm. The spectrophotometer should be zeroed against an ethanol (5.1.10) blank solution. Calculate and record concentration. Immediately dispense aliquots (~ 1,3 ml) into cryogenic vials and freeze at < -15℃ for up to 6 months.
Vitamin D3 stable isotope labelled stock standard solution, ρ≈10 μg/ml. Dispense the contents ofa 1 mg vial of d6- vitamin D3 (5.1.5) into a 100 ml volumetric flask. Dissolve in 90 ml of ethanol (5.1.10). To promote dissolution, sonicate if necessary. Mix thoroughly, make up to volume with ethanol (5.1.10). Measure the absorbance of an aliquot at 265 nm. The spectrophotometer should be zeroed against an ethanol (5.1.10) blank solution. Calculate and record concentration. Immediately dispense aliquots (~1,3 ml) into cryogenic vials and freeze at< -15℃ for up to 6 months.
Stable isotope labelled internal standard solution,p≈1 ug/ ml. Depending on the number of samples that need to be analysed in a run, more or less stable isotope labelled internal standard solution needs to be made up. For every 15 samples (or part thereof) in an analytical run, remove 1 vial of Vitamin D2 stable isotope labelled stock standard solution (5.3.2) and/or 1 vial of Vitamin D3 stable isotope labelled stock standard solution (5.3.3) from the freezer and allow to warm to room temperature.
Pipette 1,0 ml of vitamin D2 stable isotope labelled stock standard solution (5.3.2) and/or 1,0 ml of vitamin D3 stable isotope labelled stock standard solution (5.3.3) into a 10 ml volumetric flask (use a separate 10 ml volumetric flask for each set of 15 samples). Make each 10 ml volumetric flask to volume with acetonitrile, pool together and mix thoroughly. Make fresh daily.ISO 20636 pdf free download.
