INSTRUMENTATION
nuclear
• chicago
can be approximated by multiplying the peak height by its half-band width, which gives very satisfactory results. It was also found that the retention times—i.e., distance of peak from the starting point— were somewhat pro portional to these half-band widths. Therefore, one can also obtain the area by multiplying the peak height by the retention time. This brief summary of the Vapor Fractometer has been derived from an extensive report by H. H. Hausdorff of the Perkin-Elmer Corp. More de tailed information will undoubtedly be forthcoming from this source. The Vapor Fractometer will find use wherever mixtures of gases or low boiling liquids are analyzed routinely. The method may also be used for the separation of unknown components from a mixture, which can then be qualitatively analyzed by infrared or mass spectrometry, or other means. Time for analysis varies from 0.5 to 5 minutes per component. The repro ducibility is better than 0.5%. As little as 1 mg. of sample per analysis is required. A few other characteristics or speci fications may be of interest: Amount of sample for full scale deflection : gases, 0.1 mg.; low boilers (25° to 50° C ) , 1 mg.; medium boilers (50° to 100° C ) , 5 mg.; high boilers (100° to 200° C ) , 10 to 20 mg. Sample volume required for multicomponent mixtures: liquids, 5 to 20 μΐ. gases, 100 to 500 μΐ. Op timum speed, 2 to 3 minutes per com ponent. Stability and noise, 0.25% of full scale. Reproducibility, 0.25 to 0.50% concentration even if flow rates, temperatures, and sample quan tities are varied over a wide range. Resolution (retention time Va band width), 15 for a 4-foot column length. For qualitative analysis the abscissa values for peaks are characteristic of the component and independent of other components present. For quan titative analysis, the area under each peak is proportional to sample quantity. Perfect symmetry of bands permits obtaining area proportionality by mul tiplying peak heights by half-band widths (or retention times). Thermal conductivity corrections can be neg lected if helium gas is used as a carrier. A large cylinder of gas can be used for 4 months with average daily use. This costs $16 for nitrogen or $18 for helium. The instrument is insensitive to vibration. The tentative price of the Vapor Fractometer is $1500 and deliveries are scheduled for September 1955. We congratulate Perkin-Elmer on this splendid example of automatic analysis. I t is bound to find many uses and applications.
For further information, circle number 36 A on Readers' Service Carl, page 39 λ
36 A
ANALYTICAL
CHEMISTRY
