Submitted to: Spectrochimica Acta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 25, 2000
Publication Date: August 1, 2000
Citation: Baker, S.A., Miller-Ihli, N.J. 2000. Determination of cobalamins using ce-icp-ms. Spectrochimica Acta. 55: 1823-1832. Interpretive Summary: Vitamin B12 is an essential nutrient. It plays a role in growth,cell development, and is integral in the development and maintenance of the sheath surrounding nerve cells. The primary source is meat and dairy products. Typical levels range from the low ng/g range for cheese and fish to hundreds of ng/g for liver and fortified cereals. Methods commonly employed for the measurement of cobalamin levels are typically specific only to cyanocobalamin, which means that the other forms cannot be detected. In this work, a method was developed using capillary electrophoresis combined with inductively coupled plasma mass spectrometry detection for the separation and on-line detection of 4 cobalamins and a potentially harmful analog. This will permit generation of food composition data for the various species. Micellar electrokinetic chromatography (a variation of CE) was used to provide rapid separation of free cobalt and cyanocobalamin in less than 10 minutes. This method is particularly useful for rapid screening of pharmaceutical preparations and fortified products since cyanocobalamin is most often used because of its excellent stability.
Technical Abstract: The determination of cobalamins using capillary electrophoresis inductively coupled plasma mass spectrometry (CE-ICP-MS) was investigated. Both traditional capillary electrophoresis (CE) and micellar electrokinetic chromatography (MEKC) modes of operation were studied. Optimal separation of four cobalamin species (cyanocobalamin, hydroxocobalamin, methylcobalamin, and 5'-deoxyadenosylcobalamin) and a potentially harmful corrinoid analogue (cobinamide dicyanide) was obtained using CE at a pH of 2.5. Both 20 mM phosphate and 20 mM formate buffers were used with success, although the formate buffer provided improved resolution. The CE-ICP-MS method was used to quantify cyanocobalamin in a vitamin supplement and the analytical results were in good agreement (± 5 %) with values obtained by ICP-MS for total Co levels. Solution detection limits for cobalamins using CE-ICP-MS were approximately 50 ng/mL. MEKC was found to be useful for screening of vitamin preparations because it provided a rapid means of distinguishing cyanocobalamin (the form most commonly used in vitamin preparations) from free cobalt. Separation of free cobalt and cyanocobalamin using MEKC was achieved in less than 10 minutes.