Automatic sample preparation and separation techniques

AUTOMATIC SAMPLE-PREPARATION AND SEPARATION TECHNIQUES [CH. 4 Gas Chromatograph Canopy... 

Multidimensional liquid chromatography encompasses a variety of techniques used for seunple separation, cleanup and trace enrichment [12,279-289]. A characteristic feature of these methods is the use of two or more columns for the separation with either manual or automatic switching by a valve interface of fractions between columns. These techniques require only minor modification to existing equipment, and of equal importance, enable the sample preparation and separation procedures to be completely automated. 

Automated or semiautomated sample applicators are available as well. These devices apply consistent and reproducible sample spots, but it is a misconception that they are necessary for quantitative work. With proper technique, manual methods of sample application can provide results entirely comparable to those from automatic devices. Commercial automated units employ syringes or rows of microcapillaries to apply a spot or band of sample, and some actually .spray the sample onto the layer. Many are designed for preparative separations, applying large amounts of sample as streaks across the sorbent layer. 

Gross and Pitt-Rivers (18) described a technique for the separation of TRITh and Tx on a column of kieselguhr by a modification of the Gronk-vist-Hellberg (13) procedure. The stationary phase used is 0.5 N NaOH and the mobile one is n-butanol mixed with 20% chlorofonn. The preliminary treatment of the adsorbant, the preparation of the column, and the fractionation of the effluent are carefully described in the originai paper. The samples separated by an automatic fraction collector must be tested for radioactivity in order to locate and, eventually, identify the labeled constituents of the mixture. Radiochromatography of some of the fractions may be necessary to control their homogeneity or for identification purposes. 

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