Analysis of Cheese Using Step-Scan Fourier Transform Infrared Photoacoustic Spectroscopy

2000 ◽  
Vol 54 (4) ◽  
pp. 595-600 ◽  
Author(s):  
Joseph Irudayaraj ◽  
Hong Yang
Keyword(s):  
Signal Processing ◽  
Fourier Transform ◽  
Photoacoustic Spectroscopy ◽  
Depth Profiling ◽  
Cheddar Cheese ◽  
Digital Signal ◽  
Fourier Transform Infrared ◽  
Intact Sample ◽  
Ft Ir ◽  
Infrared Photoacoustic Spectroscopy

The potential of Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS) for examination of food and the package was demonstrated. Full-fat cheddar cheese slices wrapped in polymer package were chosen as the food sample for analysis. Photoacoustic spectroscopy (PAS) in conjunction with the step-scan and digital signal processing (DSP) function was used to perform depth-profiling studies of the intact sample and package. Well-separated PAS bands of fat and protein were obtained in the spectra of cheddar cheese samples with minimum sample preparation. Cheese samples were kept in a dessicator overnight to minimize the effect of moisture on the PAS spectra. Depth profiling study of the cheese polymer package indicated that there is a diffusion of cheese components into the package during storage.

Fourier Transform Infrared Photoacoustic Spectroscopy Characterization of Sulfur-Oxygen Species Resulting from the Reaction of SO2 with CaO and CaCO3

1987 ◽  
Vol 41 (1) ◽  
pp. 120-126 ◽  
Author(s):  
Meg A. Martin ◽  
Jeffrey W. Childers ◽  
Richard A. Palmer
Keyword(s):  
Fourier Transform ◽  
Photoacoustic Spectroscopy ◽  
Depth Profiling ◽  
Fourier Transform Infrared ◽  
Product Layer ◽  
Oxygen Species ◽  
Initial Product ◽  
Ft Ir ◽  
Infrared Photoacoustic Spectroscopy

Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS) has been used to investigate the reaction of SO2, in He with CaO and CaCO3 particles at temperatures between 25 and 900°C. The reaction of SO2 with CaO occurs at 25°C, while the reaction of CaCO3 with SO2 is first evident at 550°C. The initial product of both of these reactions is CaSO3. The CaSO3 then further reacts with SO2 to form CaSO4, CaS2O3, and CaS at higher temperatures. At 900°C and above, the net production of SO4= and S2O3= is decreased because of the decomposition of SO3=. FT-IR/PAS depth-profiling experiments indicate the formation of a reaction-limiting product layer of SO3= and SO4= from the above reactions on the surface of the CaO and CaCO3 particles.

Depth Profile Study of Large-Sized Coal Samples by Fourier Transform Infrared Photoacoustic Spectroscopy

1986 ◽  
Vol 40 (2) ◽  
pp. 214-217 ◽  
Author(s):  
Tiziana Zerlia
Keyword(s):  
Fourier Transform ◽  
Depth Profile ◽  
Photoacoustic Spectroscopy ◽  
Modulation Frequency ◽  
Fourier Transform Infrared ◽  
Qualitative Description ◽  
Difference Spectra ◽  
Compositional Depth Profile ◽  
Ft Ir ◽  
Infrared Photoacoustic Spectroscopy

A multidisciplinary approach is demonstrated to elucidate coal weathering at a molecular level. Fourier Transform Infrared Photoacoustic Spectroscopy (FT-IR/PAS) provides a technique for a compositional depth profile of coal by simply varying the modulation frequency (mirror velocity) of the light impinging upon the solid surface. In order that the potential of this technique in this field could be evaluated, large-sized coal samples were examined. The PA difference spectra obtained from the spectra taken at different modulation frequencies (i.e., different depths), on a sample aged in air, demonstrate the appearance of negative features in the CH infrared absorption which are indicative of a coal alteration. Therefore, different coal layers can be distinguished by FT-IR/PAS. The application of the same technique to the study of a coal sample heated in air at 200°C allows the detection of different oxidation mechanisms operating inside and outside the coal. Although quantitative results are difficult to obtain, the technique can be successfully proposed for a qualitative description of coal weathering.

Digital Signal Processing for Step-Scan Fourier Transform Infrared Photoacoustic Spectroscopy

1997 ◽  
Vol 51 (4) ◽  
pp. 453-460 ◽  
Author(s):  
David L. Drapcho ◽  
Raul Curbelo ◽  
Eric Y. Jiang ◽  
Richard A. Crocombe ◽  
William J. McCarthy
Keyword(s):  
Signal Processing ◽  
Fourier Transform ◽  
Digital Signal Processing ◽  
Phase Modulation ◽  
Modulation Frequency ◽  
Digital Signal ◽  
Sampling Depth ◽  
Ft Ir ◽  
Infrared Photoacoustic Spectroscopy ◽  
Additional Hardware

A software-based digital signal processing (DSP) method using the data system processor has been developed to demodulate the photoacoustic responses of a sample to the fundamental phase modulation frequency and its harmonic frequencies (up to the ninth harmonic) in step-scan FT-IR photoacoustic measurements, without the use of any additional hardware. The DSP algorithm and its sampling depth multiplexing advantages are compared to conventional hardware demodulation. Comparison of results from the DSP method to those from hardware demodulators are shown at both the phase modulation frequency and the harmonics, and application of the DSP method to step-scan photoacoustic measurements with phase modulation is discussed as it applies to obtaining depth profile information in heterogeneous materials.

Infrared Photoacoustic Spectroscopy of Conducting Polymers. I. Undoped and n-Doped Polyacetylene

1981 ◽  
Vol 35 (6) ◽  
pp. 557-559 ◽  
Author(s):  
Stephen M. Riseman ◽  
Stuart I. Yaniger ◽  
Edward M. Eyring ◽  
David Macinnes ◽  
Alan Graham Macdiarmid ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Infrared Spectrum ◽  
Conducting Polymers ◽  
Infrared Spectra ◽  
Photoacoustic Spectroscopy ◽  
Fourier Transform Infrared ◽  
Spectral Shifts ◽  
Ft Ir ◽  
Infrared Photoacoustic Spectroscopy

Fourier transform infrared photoacoustic (FT-IR-PA) spectroscopy has been used to obtain the first published infrared spectrum of a heavily n-doped polyacetylene. Comparisons are made with the FT-IR-PA spectrum of undoped polyacetylene. All the infrared peaks in the FT-IR-PA spectrum of undoped polyacetylene agree in wavelength to ±10 cm−1 with transmission infrared peaks previously assigned by Shirakawa and Ikeda. Spectral shifts and intensity differences between the n-doped and undoped polyacetylene are similar to changes noted previously in the infrared spectra of p-doped polyacetylenes.

Infrared Photoacoustic Spectroscopy of Conducting Polymers III. Polyparaphenylene and its Derivatives

1984 ◽  
Vol 38 (1) ◽  
pp. 7-11 ◽  
Author(s):  
Stuart I. Y. Aniger ◽  
David J. Rose ◽  
William P. McKenna ◽  
Edward M. Eyring
Keyword(s):  
Fourier Transform ◽  
Conducting Polymers ◽  
Organic Semiconductor ◽  
Photoacoustic Spectroscopy ◽  
Fourier Transform Infrared ◽  
High Quality ◽  
Organometallic Derivative ◽  
Ft Ir ◽  
Infrared Photoacoustic Spectroscopy

Fourier Transform Infrared Photoacoustic (FT-IR/PA) spectroscopy provides a means to obtain high quality spectra of polyparaphenylene (PPP), an organic semiconductor. Spectra of PPP prepared by two different methods, heavily n-doped PPP, and a new organometallic derivative, PPP(Mo(CO)3)0.25 are presented. Spectral acquisition times for these polymers can be as low as one minute.

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