抄録
Methods of treatment and extraction of porcine blood were investigated for measurement of vitamin B_<12> (B_<12>) using a mutant of Escherichia coli which requires B_<12> for growth. B_<12> Values in whole blood treated with heparin, heparinized plasma and serum were almost the same, but those in plasma treated with EDTA were approximately 1.5 times as high as those by other treatments. The values of B_<12> were stable in the acetate buffer adjusted at pH 4.5-5.0, and not affected by addition of 0.5ml or less of KCN. The recovery of B_<12> by the boiling method was higher than that by the autoclave procedure, and the variance coefficients of the values obtained were lower in the former. The same value of B_<12> was obtained regardless of addition of meta-phosphoric acid. Almost constant B_<12> values were obtained until 7 days after sampling when serum and B_<12> extracts were stored below 4℃.
