Developed for Measuring Vitamin B12
By Rosalie Marion
September 16, 2003
A new method to measure quantities
of vitamin B12, both in foods and in dietary supplements, has been developed by
Agricultural Research Service
Vitamin B12 is an essential nutrient linked to human growth and cell
development. The Food and
Nutrition Board of the Institute of
Medicine, which establishes reference values for nutrient intakes,
advocates research related to absorption and bioavailability of this important
Scientifically, vitamin B12 is a family of compounds called cobalamins. Each
form has its own potential biological activity in terms of absorption and
potency. Naturally occurring forms of B12 are found predominantly in meat and
dairy products. A synthetic form, called cyanocobalamin, is used in the United
States to fortify foods and to make dietary supplements.
A microbiological assay has commonly been used to analyze the amount of B12
in samples, but that method takes days and is expensive. Another drawback is
that it measures the total amount of B12 in a sample, but not how much of each
of the individual forms.
The newer method for quantifying cobalamins uses one of two separation
techniques (one is capillary electrophoresis, or CE, and the other is
micro-high-performance liquid chromatography, or HPLC) combined with a
detection technique called inductively coupled plasma mass spectrometry, or
This hybrid method allows scientists to quickly detect and measure levels of
specific cobalamins, according to research chemist Nancy Miller-Ihli, who heads
the trace element lab in the Food
Composition Laboratory at the ARS Beltsville Human Nutrition Research
Center in Beltsville, Md. ARS is the U.S.
Department of Agriculture's chief scientific research agency.
The ARS lab is now testing various food and supplement samples using
CE-ICP-MS to measure the various cobalamins. Preliminary results report
important data findings in commercial vitamin supplements. Future projects will
focus on human breast milk.
Accuracy in measuring the quantity of each of the cobalamins in foods and
supplements is crucial for understanding absorption mechanisms, which will lead
to health recommendations important to the public.