from the specialists in liquid chromatography
Report for Analytical Chemists
Newest UV monitor outperforms all others.
Why settle for less? The most sophisticated UV monitor on the market costs only $ 1 3 9 5 . It's the Chromatronix 220 Absorbance Detector. Our Model 220 gives you superior resolution—shown at right compared to a popular model of a leading competitor when both were operated at a full-scale range of 0.16 absorbance units. It gives you easily quantifiable curves, since output is linear from .0002 to 1.0 OlFS absorbance units. It gives you the ability to detect very low concentrations by using our 1 cm path length cell to get a sensitivity of .0002 A per centimeter. It keeps very high concentrations on scale when you use our .05 cm path length cell to get a linear range up to 20 A per centimeter (1.0 A -r- .05 cm). It gives you the accuracy of true double-beam optics, in which the output is the difference between beam absorbance in the sample cell and in the reference cell. It gives you two switch-selectable wavelengths, 280 nm and 254 n m — s o you can cope with compounds insensitive to one or the other. And if you opt for our two-channel version (Model 230, $1795), it gives you simultaneous read-outs of absorbance at 280 nm and 254 nm. This is a monitor you should know more about. Ask for a demonstration or send for 4-page product bulletin right now.
Theirs
Chromatronix, Inc., 2743 Ninth Street, Berkeley, CA 94710. Phone (415) 841-7221.
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CIRCLE 35 O N READER SERVICE CARD
ANALYTICAL CHEMISTRY, VOL. 44, NO. 9, AUGUST 1972
T h e X A D - 2 resin technique has t h e advantages of avoiding emulsions which can plague liquid-liquid methods a n d extracting some of t h e polar drug metabolites. Preprepared columns are available commercially (Brinkman I n s t r u m e n t s , Inc., " D r u g Skreen," Westbury, N . Y . ) , and they provide t h e added nicety of a phase-separating interface at t h e end of t h e column which substantially avoids t h e problem of eluting unwanted absorbed water. I t also overcomes t h e operational disadvantages of washing and purifying t h e resin before use a n d t h e necessity t o assemble a n d pack t h e columns. T h e columns cannot b e reused indefinitely, a n d tests m u s t be m a d e t o determine their life span. T h e loss of activity can be precipitous. T h e r e are a variety of organic solvents and solvent mixtures used t o elute t h e drugs from t h e column. E t h y l e n e dichloride-ethyl acetate is advised for t h e commercially prepared columns, b u t ethyl acetate followed by methanol is most frequently used a n d is efficient. I t s disadvantage is t h a t methanol removes water and in common with all other eluting systems, also removes absorbed urine pigments resulting in intolerably dirty residues. Clean-up steps are necessary before acceptable gas or thin-layer chromatography can be achieved {21). T h e efficiency of extraction of t h e drugs is dependent upon t h e p H of the urine as it passes t h r o u g h t h e resin column, and unfortunately, the optimal p H of 8.5-9.5 for morphine and other amphoteric bases is not ideal for phenethylamines such as amphetamine (pH 7-9) or t h e barbiturates (pH 5-7). Either an u n h a p p y compromise p H must be
