Stanley Samuels
New York University Medical Center New York, New York 10016
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A Simple Sprayer for Quantitative ~ h h - 1 i y e rchromatography
M a n y different types of chromatographic sprayers are commercially available. In general, they have in common that they are quite expensive, easily broken, and costly to repair. By contrast, artists' mouth-type atomizers are of very simple construction and quite inexpensive. These, are, however, generally constructed of metals which are readily attacked by many of the reagents used in chromatography. This design, therefore, has been incorporated in a simple, inexpensive sprayer for chromatographic use which can be easily constructed by a student as a laboratory project. It can be used as a mouth atomizer or, with a simple accessory, it can be attached to a source of compressed air. The Sprayel
A hole is bored with a #1 cork borer about 2 mm in from the larger end of a #l,l-hole rubber stopper (Fig. l,c). The hole is bored only halfway through the stopper and a t a right angle to the existing hole. The mouth piece (b) is prepared from 6-mm tubing sharply tapered to 4 mm 0.d. a t one end. Eight to ten centimeters is a convenient length. This tube is inserted into the rubber stopper from the small end so that the tapered tip falls just short of the crosswise hole. The inlet tube (a) is constructed from 4-mm tubing which is constricted and tapered to give a 0.5-1-mm opening a t one end. The overall length of this tube can be varied according to the height of the reagent bottle used. The tube is inserted, tapered-end first into the crosswise hole of the stopper so that i t ends a t about the middle of the mouthpiece opening. When the inlet tube is dipped into the reagent, a fine, uniform spray can b e p r o dnced by blowing through the mouthpiece. In practice, the smaller size orifice (0.5 mm) is most suitable for spraying reagents while sDravers . " with a large opening (1.0 air I mm) can be used for spray-coating Figure 1 (left). Diogrmm of the rproyer. Figure 2 (right). Diagram of adapter for thin-layer plates. attachment to compressed .ir line*.
438
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Journal o f Chemical Educmfion
A Sprayer Adapter
Many reagents are corrosive or otherwise unpleasant and it is undesirable to spray by mouth. In those cases, a convenient adapter can be used (Fig. 2). A piece of 6-mm polyethylene tubing about 15 cm long is carefully heated over a small burner flame, and slightly constricted about 4 cm in from one end (d). The tube is immersed in cold water to help it retain its shape. It is then carefully heated a t its center and a right angle bend is made by shaping and cooling. One end of the tube is then stoppered, carefully heated with a small burner just below the bend (away from the constriction), and a small hole is blown out (e). In use, the mouth piece of a sprayer is fit snugly against the constriction of the adapter. The glass tube fits easily into the plastic and does not bind. The side opening is used to provide thumb control of the air pressure. Advantages
The sprayers are simple to construct, quite inexpensive, and the glass tubes easily replaced if they are broken. The sprayers are generally resistent to most of the reagents that are used. It is convenient to have one for each reagent, kept in a small test tube taped onto the side of the bottle. Polyethylene tubing is about as easy to work with as glass and has the advantage of being unbreakable. It was particularly suitable for the spraying adapter and would have been ideal for the sprayers themselves, but glass tubing and rubber stoppers were more readily available. Microplates (76 X 76 mm)' have been routinely spray-coated with cellulose or silica by means of a sprayer of this type and used for qualitative and quantitative TLC. Chromatograms developed by spraying with ninhydrin, silver nitrate-sodium hydroxide, or a number of other reagents were sufficiently uniform for quantitative scanning of the spots by direct densitometry. The performance of this sprayer was a t least equal to that of commercial models. This work was supported by NIH Grant Number MH10359-02.
' SAMUELS,S., AND
J. CHEM.EDUC.,43, 145 (1966). SAMUELS, S. WARD,S., J . Lab. Clin. Med., 67, 669 (1966).
