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Quantitative Infrared Analysis of Borophosphosilicate Films Using Multivariate Statistical Methods 1208
published periodically for analytical chemists
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
linear approximations 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: Rix = Ru + Pu ~ Ri2] [tx)/[t4] Rn is initial response of the standard, Ri2 is response of the standard after time t 4 , and t x is time elapsed between Rn and Rix. For linear response instruments,
Partial least-squares, principal components regression, and classical least-squares methods are compared for the rapid IR determination of boron, phosphorus, and thickness of thin-film silicate glasses used in integrated circuits. David M. Haaland, Sandia National Laboratories, Albuquerque, N.M. 87185 Anal. Chem., 60 {1988)
Alleviation of Overlap Interferences for Determination of Potassium Isotope Ratios by Inductively Coupled Plasma Mass Spectrometry 1217 Plasma operating conditions can be adjusted to remove virtually all the Ar + and ArH + ions so that potassium isotope ratios can be determined without interference from these background peaks. Shiuh-Jen Jiang, R. S. Houk*, and Max A. Stevens, Ames Laboratory—U.S. Department of Energy and Department of Chemistry, Iowa State University, Ames, Iowa 50011 Anal. Chem., 60 (1988) Quantitative Determination of Organic Compounds by Diffuse Reflectance Fourier Transform Infrared Spectrometry 1221 A method for the determination of the absolute reflectance of the matrix material used in DRIFTS is shown, allowing the correct application of the Kubelka-Munk equation even at low concentrations. Dietmar Reinecke and Anton Jansen, Fachhochschule Munster, Fachbereich Chemie—Ingenieurwesen, 4430 Steinfurt, Federal Republic of Germany, and Friedrich Fister* and Ulrich Schernau, BASF Lacke + Farben AG, 4400 Munster, Federal Republic of Germany Anal. Chem., 60 (1988)
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 Mx = [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: 215-766-8861
Analysis of Inorganic Powders by Time-Wavelength Resolved Luminescence Spectroscopy 1224 A time-wavelength resolved luminescence spectrometer is described along with the evaluation of an algorithm for resolving highly overlapped spectral envelopes. Edgar F. Paski and M. W. Blades*, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Y6 Anal. Chem., 60 (1988)
Low-Blank Chemical Separation of Rhenium and Osmium from Gram Quantities of Silicate Rock for Measurement by Resonance Ionization Mass Spectrometry 1231 Separation efficiencies are >70% for both elements at the nanogram level. Duplicate analyses give results generally within 5% of the average. Richard J. Walker, National Measurement Laboratory, Center for Analytical Chemistry, A 21 Physics Building, National Bureau of Standards, Gaithersburg, Md. 20899 Anal. Chem., 60 (1988)
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CIRCLE 148 ON READER SERVICE CARD 670 A • ANALYTICAL CHEMISTRY, VOL. 60, NO. 11, JUNE
1, 1988
