Hunan Normal University, P. R. China (Bo Chen)
Comments on VB12 analysis:
1. The SPE procedure is a key step for the high recovery. We tested different brands of SPE
cartridge during vitamin B12 multi-laboratory testing study. When using Welchrom C18
500mg/6ml, Orochem C18 500mg/3ml, Agela C18 200mg/3ml, and Supelco C18 500mg/6ml
respectively, the recovery was about 60%. Only Supelco C18 1000mg/6ml can gave above 95%
recovery. Therefore, the method should specially point out the performance of SPE cartridge (not
just equivalent). Otherwise, the results will be difficult to guarantee when Alltech SPE is not used.
2. In D1 (sample prepare), the sample is in 100-mL volumetric flask, then heated at 105
°
C
(extraction step). We think the operation is not rigorous because the volume of the volumetric
flask will be changed. Normally, the volumetric flask should be not heated at high temperature;
otherwise, the volume will be not accurate.
3. Although SPE procedure is controlled by vacuum, the flow rate is not
precise. It will affect the
recovery significantly, especially to other brands of SPE cartridge. Although Hg vac or -15 kPa
with Alltech cartridges is required in the method description, we think the vacuum control
performance of the vacuum pump should be mentioned in Apparatus section.
