BS ISO 20634:2015 pdf free.Infant formula and adult nutritionals — Determination of vitamin B 12 by reversed phase high performance liquid chromatography (RP-HPLC).
6.2.1.5 Elemental formulas For products containing free amino acids and no intact protein, add 0,5 g of calcium caseinate or non- fat dry milk to 3,0 g of a wet blended homogeneous powder diluted with 25 ml water or 20 g to 25 g of a liquid or reconstituted dry blended nonhomogeneous powder. Mix well to dissolve the protein. Immediately add 30 ml of sodium acetate buffer (4.12.2.11) and 1 ml of 1 % potassium cyanide. Dilute to volume with water, filter, and clean up and concentrate up to 60 ml of filtrate on a preconditioned 900 mg C8 or C18 cartridge. Do not heat the sample in the 105 °C oven.
6.2.2 Extraction Add 30 ml of sodium acetate buffer (4.12.2.11) to each sample extract and swirl to mix. In a fume hood, add 1 ml of freshly prepared 1 % potassium cyanide (4.12.2.10) to each sample and swirl to mix. Heat samples in a 105 °C oven for at least 60 min, but for no more than 120 min. The oven temperature will drop when the door is opened. Start timing when the oven temperature returns to 105 °C.
Remove samples from the oven and immediately cool in an ice bath. Dilute samples to volume with water. Mix well. Filter samples through a filter paper (5.12) into 125 ml conical flasks or equivalent glassware. If necessary, filter papers can be changed if they become clogged. If prepared samples are opaque and contain very small insoluble particles, centrifuge samples and transfer the liquid layer to funnels lined with filter paper. Do not heat any samples to which calcium caseinate has been added, see 6.2.1.5.
6.2.3 Sample concentration To clean up and concentrate the sample, insert a 900 mg SPE cartridge (5.17) onto the stopcock of the vacuum manifold and attach a 30 ml disposable syringe barrel to the top of each cartridge. Condition each cartridge with at least 20 ml of acetonitrile (elute by gravity) and rinse each cartridge with at least 10 ml of water. Using volumetric pipets, transfer sample filtrates to cartridges using the guidelines in Table 1. If the vitamin B 12 concentration is unknown, use guidelines for RTF products containing 1 µg/l to 10 µg/l. If necessary, apply enough vacuum so that the samples drip steadily through the cartridges. Sample filtrates should pass through the cartridges at a rate of no more than 120 drops/min. Discard eluent.
After all of the sample filtrate has passed through the cartridge, rinse each cartridge with 5 ml water and discard eluent. Air dry each cartridge by pulling a vacuum until no more eluent is observed. Close each stopcock.BS ISO 20634 pdf download.