GAS FACTS published periodically linear approximations f o r analytical chemists between responses of the introduced standard. The algorithm used to calculate sample response is based on determining response of the standard, Rix, at the time of analysis of a sample:
Compensation by computer for instrument drift
Instrument drifts of the order of 0.5%/hr can pose problems when making very accurate and precise measurements. To control drift to better than 0.1 % over a 10 hr period, Scott has developed a unique computer
Rix = Ru + Pn - RE! t y / f t d RJI is initial response of the standard, Ri2 is response of the standard after time t 4 , and t x is time elapsed between RM and Rix. For linear response instruments,
BRIEFS Dielectric Characterization of Binary Solvents Containing Acetonitrile 674 N o n l i n e a r regression functions a r e established for 10 acetonitrile cosolvent pairs, and t h e factors d e t e r m i n i n g t h e deviations from ideal dielectric behavior for t h e m i x t u r e s a r e identified. Orland W. Rolling, Chemistry Department, Southwestern College, Winfield, Kan. 67156 Anal. Chem., 59 (1987)
Correspondence Characterization of a Microinjector for Capillary Zone Electrophoresis
678
Ross A. Wallingford and Andrew G. Ewing*, Department of Chemistry, The Pennsylvania State University, University Park, Pa. 16802 Anal. Chem., 59 (1987)
Application of a Modulated Magnetic Field to a Flame Photometric Detection Burner in the Detection of Phosphorus
681
Nobuko I. Wakayama*, Hisakazu Nozoye, and Ichiro Ogasawara, National Chemical Laboratory for Industry, Tsukuba Research Center, Yatabe, Ibaraki 305, Japan Anal. Chem., 59 (1987)
Aids for Analytical Chemists Purge Gas Enhancement of Peak Resolution in Differential Scanning Calorimetry 684 Guang-Way J a n g , Ranjana Segal, and K r i s h n a n Rajeshwar*, Department of Chemistry, The University of Texas at Arlington, Arlington, Tex. 76019-0065 Anal. Chem., 59 (1987)
controlled system. In it, signal-to-noise ratio is enhanced by digital filtering and signal averaging, and drift is compensated by introducing a standard on a preestablished time basis (ea 10 min) and tracking its response. The computer maintains records of time and responses for both standard and sample. A few assumptions underlie the program. One is that "zero" drift is negligible in comparison to span drift which is derived by successive
a new slope, Mx, can be calculated from M x = [y - b ] / [Rix] where y is standard concentration and b is initial intercept. Sample concentration at t x can then be calculated. Scott has used this technique to monitor the stability of gases such as CO and H2S over time frames of more than a year. Ask for more information. INFORMATION HOTLINE: 800-331-4953 8:00AM-5:00PM Eastern time In PA: Z15-766-8861
Automated Ion-Exchange Column System for Biological Sample Fractionation 687 Y. T. Kim and Christiaan Glerum*, Ontario Tree Improvement and Forest Biomass Institute, Ontario Ministry of Natural Resources, Maple, Ontario, Canada L0J 1E0 Anal. Chem., 59 (1987)
Correction. Elemental Characterization of the National Bureau of Standards Milk Powder Standard Reference Material by Instrumental and Radiochemical Neutron Activation Analysis 688 Robert R. Greenberg, Center for Analytical Chemistry, National Bureau of Standards, Gaithersburg, Md. 20899 Anal. Chem., 59 (1987)
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CIRCLE 152 ON READER SERVICE CARD 312 A · ANALYTICAL CHEMISTRY, VOL. 59, NO. 4, FEBRUARY 15, 1987
