WHEATON INSTRUMENTS

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GAS FACTS published periodically To remedy this situation, for analytical chemists Scott has begun an experi­

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mental program to evaluate several systems of interest to chromatographers. First to be Miscibilities in examined was methanol/ supercritical carbon dioxide. A few of the experimental curves are fluids shown. It can be seen that In supercritical fluid chroma­ solubility of methanol in C02 tography, the use of a mobile is not significantly influenced phase containing a polar by either temperature or compound, ie, CH3OH in C02, pressure changes in the region can change separation prop­ below 100 atmospheres-and erties without altering that in this pressure range, critical temperature, viscosity mole fraction of the alcohol or density of the fluid. Such must be kept below 0.15 to additions can greatly extend maintain a homogeneous the applications of this system. Above about 120 analytical method. However, atmospheres, pressure and it is necessary to know the temperature both exert miscibility of the two com­ significant effects. During ponents under operating con­ the experiments, it was also ditions. Unfortunately, observed that after tempera­ experimental data do not ture changes, several hours exist and sufficient data are were required before the not available for use in system reached a new 1 Peng-Robinson or other equilibrium. theoretical models. If you are interested in learning more of this pioneering work, get in touch with Scott. We'll be happy to discuss 52 'C with you our efforts to generate solubility information olubility of me thanol 1η carbc η diox de so essential for chemists On, involved in supercritical fluid chromatography and extrac­ tion. You can also learn about /24l C mixtures at conditions near and below the critical point.

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Expand rotary evaporator glassware to combine operations

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Performs solvent extractions and solvent stripping in the same system

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Collect micro samples directly into chromatography vials

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For more information cail toll-free 1-800/225-1437.

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CIRCLE 177 ON READER SERVICE CARD ANALYTICAL CHEMISTRY, VOL. 60, NO. 13, JULY 1, 1988 · 801 A