The only thing variable about the SF 770 Spectroflow Monitor for liquid chromatography is the wavelength!
• It consistently offers highest sensitivity with low noise and baseline drift. • It classically follows Beer's law in its measurements. • It routinely includes an automatic gain control and zero suppression. • It equally interfaces with all Liquid Chromatography systems. • It inconspicuously takes up very little room. • It uniquely incorporates a doublebeam design. • It invariably is an honest instrument, not relying on gimmicks to achieve unrealistic specs. • It indubitably is preferred by more liquid chromatographers than all other models combined. Call or write now!
24 B O O K E R STREET, W E S T W O O D , NEW JERSEY 07675 (201) 664-7263
SCHOEFFEL INSTRUMENT CORPORATION
CIRCLE 462 O N READER SERVICE CARD
relations between the accepted methods and the NIR methods. Note that differences between the two methods can be attributed to errors in both methods and not just the NIR method. Other Applications
Reports of the determination of constituents in agricultural products other than grains and grain products have been published. Massie (20) reported a correlation coefficient of +0.82 between fat content of ground beef determined with a gallium arsenide infrared emitter and by a chemical method. However, there were problems with the life of the emitter and accuracy of the determination. Neotec Instruments, Inc., markets a ground meat analyzer (GM/A) for the estimation of percentage fat in ground meat. The GM/A uses a low intensity light source to illuminate the meat sample. An optical scanning system measures the amount of light reflected by the sample at the appropriate absorption wavelengths of the fat. The instrument is calibrated to a sample of known fat content. The author is not aware of any published information regarding the precision and accuracy of the GM/A. However, Weiner Associates, Inc. (21 ) , evaluated the GM/A, and their unpublished report shows that the standard deviation band for measurements of fat content of ground beef differs by less than 1 wt % fat content from the standard deviation of measurements made by the official AOAC procedure. Norris et al. (22) showed the potential of NIR reflectance for prediction of the quality of forages. They correlated the second derivative of log (1/R) vs. wavelength with compositional and nutritional data of 87 forage samples. When up to nine wavelength points were used for the prediction equations, correlation coefficients ranged from +0.80 for digestible matter intake to +0.99 for crude protein and +0.98 for neutral detergent fiber. Norris (personal communication) also found excellent correlations between the contents of certain amino acids in agricultural products and NIR reflectance values. Problems
RAININ INSTRUMENT CO INC
94 Lincoln St., Brighton, MA 02135 ·
1-800-225-4590
CIRCLE 179 O N READER SERVICE CARD 8 3 8 A • A N A L Y T I C A L CHEMISTRY, V O L . 4 9 , NO. 9, A U G U S T
1977
The primary problem of NIR analysis of grains and oilseeds for protein, oil, and moisture is preparation of the sample. These problems have been discussed (23) and are summarized here. Because the samples in most cases must be ground, uniform grinding is a major problem. Hymowitz et al. (14) showed that grinding time affected protein and oil results of soybeans and oats determined by NIR. A
