This paper reports a novel method for the rapid determition of vitamin B12 concentration in a continuous-flow lab-on-a-chip system. This new method is based on luminol-peroxide chemiluminescence (CL) assays for the detection of cobalt(II) ions in vitamin B12 molecules. The lab-on-a-chip device consisted of two passive micromixers acting as microreactors and a double spiral microchannel network serving as an optical detection region. This system could operate in two modes. In the first mode, samples are acidified and evaluated directly in the microchip. In the second mode, samples are treated exterlly by acidification prior to detection in the microchip. In the first mode, the linear range obtained was between 1.00 ng ml-1 to 10 姠ml-1, R2 = 0.996, with a relative standard deviation (RSD) of 1.23 to 2.31% (n = 5) and a limit of detection (lod) of 0.368 pg ml-1. The minimum sample volume required and the alytical time were 30 嬠and 3.6 s, respectively. In the second mode, the linear range obtained was between 0.10 ng ml-1 to 10 姠ml-1, R2 = 0.994, with the RSD of 0.90 to 2.32% (n = 6) and a lod of 0.576 pg ml-1. The minimum sample and the alytical time required were 50 嬠and 6 s, respectively. The lab on a chip working in mode II was successfully used for the determition of vitamin B12 concentrations in nutritiol supplemental tablets and hen egg yolks.
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