Near-infrared spectrometry calibration

Adams, M.J., Latham, K., Barnett, N. W., and Poynton, A. J. (1999). Calibration models for determining moisture and fat content of processed cheese using near-infrared spectrometry. J. Sci. Food Agric. 79,1232-1236. 

Because a diffuse reflectance spectrum is scatter-dependent, information on mean particle sizes is also obtainable, which is a parameter of great importance in powder technology. An approach using near-infrared spectrometry combined with multivariate calibration has been presented by Ilary, Martens, and Isaksson. Included was a spectrum standardization by multiplicative scatter correction (see later). 

Keywords near-infrared spectrometry (NIRS), lake sediments, calibration models, palaeolimnological reconstruction, optimal sample selection. NlRtheoiy, spectral filters, instrument design, sanple preparation. 

Near-infrared spectrometrie method This method has also been shown to be particularly suited to the determination of moisture in dried vegetables. Absorption is measured at wavelengths characteristic of molecular vibration in water and compared with a calibration equation derived from reference samples of known composition. 

M. Blanco, J. Coello, H. Iturriaga, S. Maspoch and C. Pezuela, Strategies for constructing the calibration set in the determination of active principles in pharmaceuticals by near infrared diffuse reflectance spectrometry. Analyst, 122, 761-765 (1997). 

For the application of indirect calibration methods, one should have several samples available with known constitution. These samples should be of exactly the same type as the unknown sample. For example for the determination of the fat, water and protein content in wheat by near infrared reflectance spectrometry, one should have available a number of wheat flour samples of which the amount of fat, water and protein is known, or determined by a conventional method. 

The liquid products were quantified by GC-FID (gas chromatograph with flame ionisation detector) and characterised with GC-MS (gas chromatograph with mass spectrometer). The aromatics content was monitored on-line with a near infrared spectrometer that was calibrated by proton nuclear magnetic resonance spectrometry. 

See also-. Bioassays Overview. Chemometrics and Statistics Multivariate Calibration Techniques. Infrared Spectroscopy Near-Infrared. Liquid Chromatography Size-Exclusion Liquid Chromatography-Mass Spectrometry Liquid Chromatography-Nuclear Magnetic Resonance Spectrometry. Pharmaceutical Analysis Drug... 

Gotor et ah (2007) reported the use of near-infrared reflectance spectrometry (NIRS) to predict the contents of tocopherol and phytosterol in sunflower seeds. About 1000 samples of ground sunflower kernels were scanned by NIRS at 2 nm intervals from 400 to 2500 nm. For each sample, standard measurements of tocopherol and phytosterol contents were made. The total tocopherol and phytosterol contents were assessed by FIPLC with a FL detector and GC, respectively. The calibration data set for tocopherol and phytosterol ranged from 175 to 1005 mg/kg oil (mean value around 510 140 mg/kg oil) and from 180 to 470 mg/100 g oil (mean value 320 50 mg 100/g oil), with values of 0.64 and 0.27, respectively. In this study, calibrations were obtained by a modified PLS method. 

---