Ultrahigh Resolution Chromatography
New' S a t i n d e r A h u j a , Editor CIBA-GEIGY Corporation
Figure 3. Aerosols from pneumatic nebulizers (top) AA nebulizer (bottom) ICP nebulizer
transport properties. Indirect methods are generally unreliable, and those wishing to carry out en or W measure ments are referred to recent publica tions for better procedures (2, 3). The essential point to note is that except where transport efficiencies are excep tionally high, i.e., 20% or greater, the simple arithmetic of calculation en sures that data obtained by indirect waste collection will have a much higher error than data obtained by di rect aerosol collection. Errors with ICP systems are especially high, be cause of the generally low (0.5-2.0%) transport efficiencies common to them. With indirect procedures, it is easy to obtain en values with a 500% positive error (2). Aerosol Generation and Transport Processes The limitations of pneumatic nebu lizers are clear from looking at Figure 3. Aerosols produced from atomic ab sorption and ICP nebulizers can be seen to have both extremely wide drop size ranges, and very turbulent gas flow patterns. The photographs were taken with the nebulizers operating in free air, and the presence of a spray
chamber modifies the flow patterns considerably. Nevertheless, a compa rable range of drop sizes, and equally turbulent gas and aerosol flow pat terns, will still exist in the more con strained environment. The Sauter mean diameter of the aerosol produced by pneumatic nebu lizers (e.g., the diameter of the drop whose volume-to-surface-area ratio is the mean of the distribution) has tra ditionally been described by the equa tion due to Nukiyama and Tanasawa. The relationship, derived from their classic series of papers (4), is:
*-?(f
Expands the field of chromatography by recording these recent advances in ultrahigh resolution chromatography. Reports the latest developments in capillary GLC, HPLC, and SFC. Cov ers topics such as interactions be tween relative peak, relative reten tion, and absolute retention; the effect of column diameter reduction in capillary chromatography; and the use of a small volume thermal con ductivity detector. CONTENTS Overview: Multiple Pathways to Ultrahigh Resolution Chromatography · Statistical Model of Component Overlap by Com puter-Generated Chromatograms · Ultra high Resolution GC · Interactions Between Relative Peak, Relative Retention, and Ab solute Retention · Reduction of Column Diameter in Capillary GC · Small Volume Thermal Conductivity Detector for Capil lary GC · Advances in Liquid Chromatogaphic Selectivity · Narrow-Bore, Microparticle-Packed Column High Performance GC · Micro High Performance GC Applica tion to Separation of Complex Mixtures · High Resolution SFC · C 0 2 Based SFC · Super Resolution in Chromatography by Numerical Deconvolution · Role of Ultra high Resolution Chromatography in Chem ical Industry Based on a symposium sponsored by the Divi sion of Analytical Chemistry of the American Chemical Society
ACS Symposium Series No. 250
where ds (μπι) is the Sauter mean di ameter, V, the velocity difference be tween gas and liquid flows (m/s), σ, the surface tension of the liquid (dyn/ cm), p, the liquid density (g/cm 3 ), η, the liquid viscosity (poise), and Qi and Qg, the volume flow rates of liquid and gas, respectively (cm 3 /s). The limitations of this equation are well known, and it is doubtful that it
790 A · ANALYTICAL CHEMISTRY, VOL. 56, NO. 7, JUNE 1984
237 pages (1984) Clothbound LC 84-2792 ISBN 0-8412-0835-2 US & Canada $44.95 Export $53.95 Order from: American Chemical Society Distribution Office Oept. 74 1155 Sixteenth St., N.W. Washington, DC 20036 or CALL TOLL FREE 800-424-6747 and use your VISA, MasterCard, or American Express credit card.
