Slip Chromatography: A Semiquantitative TLC Technique Hara and Matsumura' have described a simple method for semiquantitative determination of traces of Cd using a modified frontal analysis2on a cation exchange thin layer. In an attempt ta use this method for estimating lead-traded from cerarnicca new and still simpler tle technique was developed. The simplicity of this technique makes it a good tool for teaching purposes. The adsorbent deposited on an ordinary tlc glass plate (20 X 20 cm) is divided into thin slips of equal width, the number of slips depending upon the desired slip-width. With 10 slips it is possible to apply, e.g., 8 standards and 2 samples to the same plate. In this way the standards and the samples will be analyzed under exactly the same conditions. Each standard and sample is 100 pl ofa buffered acetic acid solution of metal ion moles. The adsorbent is a mixture of cellulose and carhaxycontaining about methylcellulose and the adsorhenee is thus mostly due to ion exchange. The ion exchanee eaoacitv can be varied. aceordine t o the relative amount of carboxvmethvlr e ~ u l k ein . thinwav it is ~ossibie to adiusithe conditions in accordance with tge conc&tration of metal ion. When the samoles accuracy is 10% relative. It has not yet been possible to use the method for solutions containing more than one cation.
Experimental Equipment: Desaga standard tlc equipment, Blender: The cellulose and carhoaymethylcellulose must be mixed thoroughly. A two-tooth fork: Anordinary fork with only two teeth is a quitesufficient tool for keeping theslip-width constant. A rack: The tleplates must be kept in a strictly vertical position while the samplesare beingapplied and adsorbed. A water repellent tray of plastic (25 X 10 cm). A 100-pl Hamilton spray. A spray gun for solution. Chemicals and solutions: CMcellulose fiir die Diinnsehieht-Chromatographie (Merck). Cellulosepulver. MN 300 zur Diinnschicht-Chromatographie (Maekeray Nagel & Co., Diiren). Diphenylcarhazide (analytical) (Merck).Lead acetate ( C H ~ C O O ) Z P3H20 ~ , (analytical) (RiedeI.de Ha&"). Adsorbent: CM-cellulose/cellulose are mixed in wlw proportians of 1:10,1:20 and 1:40. Fifteen grams of the cellulose mixture is blended with about 90 ml of distilled water for 15 min. The mixture should end op hnvinga consistenc.likr paint. Hu//
