Report for Analytical Chemists
However, the whole system was ex tremely complicated and difficult to operate, and therefore, he tried to develop some other technique which would do the job. As described by Martin (18) : "In 1940, it occurred to me that the crux of the problem was that we were trying to work two liq uids in opposite directions simul taneously . . . Then I suddenly realized that it was. not necessary to move both the liquids; if I just moved one of them, the re quired conditions were fulfilled. I was able to devise a suitable ap paratus the very next day, and a modification of this eventually became the partition chromatograph with which we are now familiar." In their early work, chloroform containing a small amount of alco hol was used as the mobile phase, water as the stationary phase, and silica gel as the support; they could separate the monoamino monocarboxylic acids, and, according to Martin, "One foot of tubing in this apparatus could do substantially better separations than all the ma chinery we had constructed until then." In their paper, Martin and Synge (15) emphasized that, by the selec tion of suitable mobile phase—sta tionary phase combinations, the technique can be used for many other separations, and they pre dicted that: "The mobile phase need not be a liquid but may be a vapour. We show below that the efficiency of contact between the phases (theo retical plates per unit length of column) is far greater in the chromatogram than in ordinary distillation or extraction columns. Very refined separation of vola tile substances should therefore be possible in a column in which permanent gas is made to flow over gel impregnated with a non volatile solvent in which the sub stances to be separated approxi mately obey Raoult's law." It is interesting to note that, al though this prediction clearly and unequivocally predicted the possi bility of gas-liquid partition chro matography, nobody picked it up,
and it took 10 years until Martin, then with A. T. James, proved its great potential.
a new way to record nanosecond transients
Paper Chromatography
Liquid partition chromatography, as described originally by Martin and Synge, had superior separation power. However, in their original work, using water as the stationary phase and silica gel as the support, they were unable to separate the dicarboxylic and basic amino acids. They realized that the problem lay in the adsorptive power of silica gel and thus, were looking for some other support. As Martin ex plained, he had seen a "paper chromatogram" of dyes before and thus their first choice was paper. First, they used circles of papers in a Petri dish containing water ; a drop of the amino acid solution was placed in the center of the paper, and water-saturated butanol was fed to the center of the paper; when it reached the edge, the paper was dried and sprayed with ninhydrin, a substance found by Gordon to give proper color reaction with the amino acids, enabling the detection of their spots. Later, they used pa per strips in boxes, in an atmo sphere saturated with water, and the edge of the paper was dipped into the solvent (the moving phase). They also learned to run the paper in two dimensions. This is how paper chromatography, which revo lutionized biochemical analysis, was born (16). Gas-Liquid Partition Chromatography
As mentioned earlier, Martin and Synge predicted, in their original paper, the possibility of using a gas as the moving phase in partition chromatography. However, no body thought to test experimentally this prediction at that time al though gas adsorption chromatogra phy underwent an important devel opment in the 1940's. (See, e.g., the works of G. Hesse, E. Cremer, S. Claesson, E. Glueekauf, and C. S. G. Phillips ; for a listing of their pa pers, see Bibliography, ref. 20). In 1948, Martin moved to the Na tional Institute for Medical Re search, where A. T. James, who had previously been working with Synge, joined him. They were en gaged in research work which did
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ANALYTICAL CHEMISTRY, VOL. 43, NO. 14, DECEMBER 1971
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