Field experiments on the magnesium requirement of cereals, potatoes and sugar beet in relation to nitrogen and potassium application

✍ Scribed by J. A. Birch; J. R. Devine; M. R. J. Holmes

• Publisher: John Wiley and Sons
• Year: 1966
• Tongue: English
• Weight: 532 KB
• Volume: 17
• Category: Article
• ISSN: 0022-5142
• DOI: 10.1002/jsfa.2740170207

✦ Synopsis

Absorbance was measured on a Unicam SP500 spectrophotometer. Chromatograms were repeated several times : the results are as follows : Extract Method 1 1 2 2 PC TLC PC TLC No. of chromatograms 5 5 4 4 Mean absorbance at 500mp 0.621 0.601 0.986 0,985 R.m.s. deviation 0.009 0.010 0.030 0.012 Coefficient of variation 1 . 5 1 . 6 3.1 1 . 3 %

In a series of 14 assays, each performed in triplicate by TLC, the coefficient of variation was in the range 0.3-3.2 %, with a mean coefficient of variation for the 14 assays of 1 -6%.

McKeown & Mark3 quote pairs of results of assays of annatto extract which differ by 0-4%, the mean difference for the six pairs being 1.6%.

In our hands, thin layer chromatography has proved as suitable as paper chromatography for the separation of bixin before assay. Reproducible results can be obtained very rapidly.