An internal standard for amino acid analyses: S-β-(4-pyridylethyl)-l-cysteine
✍ Scribed by James F. Cavins; Mendel Friedman
- Publisher
- Elsevier Science
- Year
- 1970
- Tongue
- English
- Weight
- 289 KB
- Volume
- 35
- Category
- Article
- ISSN
- 0003-2697
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✦ Synopsis
Determination
of absolute concentrations of amino acids is the primary objective of most amino acid analyses. The conventional method of quantitating amino acid results is based on external standards (1, 2). The external standard method, however, cannot correct for changes in the system which occur between the standard and the actual analyses. Several investigators have suggested the use of internal standards in amino acid analysis (3-7). However, few compounds have been found suitable because of the rigid requirements they must meet. A suitable compound must (a) not be a naturally occurring amino acid, (b) be ninhydrin-positive and give a color yield obeying Beer's law, (c) be stable to acid hydrolysis, and (d) elute in a position that does not overlap with other normal peaks. The new rapid systems of analysis have made fulfilling these requirements even more difficult owing to crowding of peaks.
This paper describes the preparation and evaluation of a new internal standard for calculation of data from amino acid analyses. The results indicate that the new amino acid S-p-(4-pyridylethyl) -L-cysteine (PEC) is an excellent internal standard for use on a column for separating basic amino acids.