Some observations on sialic acid determination by the Warren thiobarbituric acid method

Some factors affecting determination of sialic acids by the Warren thiobarbituric acid method are reported. These are: (1) conditions of hydrolysis, (2) sample size, (3) use of trichloroacetic acid and (4) stability of thiobarbituric acid solutions. Use of the modifications described here results in more reliable values. In addition, an improved procedure for chromphore production is outlined. It should be noted that failure to observe the suggested precautions can lead to cumulative errors.