The automatic analyzer
The inception of the automatic analyzer is the most exciting and important system developed yet. The principle of the automatic analyzer is still that which Moore and Stein developed.
The automatic analyzer has been modified and refined over the years and is now obviously more sophisticated and powerful.
The Moore and Stein Method
The amino acids are separated on a cation exchange resin (contained in a column) with buffers of carefully defined sale concentration and pH.
The resin on which the ion exchange takes place, consists of small spherical beads of polystyrene, sulphonated to provide and electrical charge and reacted with divinylbenzene to achieve the required degree of 'cross linkage' between the polymerised chains of styrene.
The accuracy of the bead size distribution, as well as cross-linkage, determines the separation power.
(The sensitivity of an amino acid analyser is inversely proportional to the square of the column diameter).
Depending on the amino acids present in the sample, either sodiumor lithium salts are used for the buffers. The 'eluate' from the ion exchange column is passed through the teflon coil, placed in a boiling warer bath.
Before entering the coil, the column effluent is mixed with an acetate buffer containing the reduced ninhydrin. This compund reacts with the amino acids forming a dye complex.
The absorption, i.e. the amount of light passing through the dye complex is determined in a photometer and registered as peaks on a chart recorder.
The area under the peaks corresponds to the amounts of amino acids present in the sample.
The moore and Stein method applied to the automatic analyzer
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