Opto-acoustic effect. Revival of an old technique for molecular spectroscopy

Harshbarger, W. R.; Robin, M. B.

doi:10.1021/ar50070a001

“…Thus, we obtained the photoacoustic spectra of olanzapine in a nonscattering mixture and in a scattering mixture respectively. As shown in figure 3, there are two characteristic absorption band in the photoacoustic spectrum of the pure olanzapine powder between 360 and 500nm and between 680 and 820 nm, and the former has higher magnitude, which is consistent with the reports on the absorption spectra of olanzapine [19,20] . The photoacoustic spectrum of the base powder is flat, and there is only a weak absorption peak at 860 nm.…”

Section: Data Processingsupporting

confidence: 87%

“…An electret microphone and its preamplifier (MPA251, BSWA Technology Co., Ltd., Beijing, China) was used to detect the acoustic signal, and then the signal was fed into a chopper was 20Hz, and the time constant of the lock-in amplifier was 1s. The photoacoustic spectra of all the samples were normalized with the photoacoustic spectrum of carbon black to remove the spectral features of the light source and the optical system [19] .…”

Section: Pas Measurementsmentioning

confidence: 99%

Scattered light: improving photoacoustic spectral measurement with a drug tablet

Yu

¹

,

Jiang

²

,

Yu

³

et al. 2013

SPIE Proceedings

0

View full text Add to dashboard Cite

Photoacoustic spectroscopy (PAS) is a powerful tool for the study of the absorption spectra of solid samples.Scattered light, which used to be a main error source in conventional absorption spectroscopy, is not a problem for PAS, and furthermore, in this paper it is helpful for photoacoustic spectroscopy measurement. In this work, the photoacoustic spectra of an olanzapine tablet and its powder have been investigated. Differential analysis was used to eliminate the background signal generated by the photoacoustic cell. It is found that the photoacoustic spectrum of olanzapine in the powdered olanzapine tablet has the same spectral features as that of the pure olanzapine powder, while the photoacoustic spectrum of the olanzapine tablet does not have, although the ingredients in both are completely the same. This phenomenon can be interpreted as the light scattering effects in the powdered olanzapine tablet. The light scattering effects in a solid mixture amplify the photoacoustic spectral features of the main light-absorbing ingredient in the mixture, rather than enhance the measured photoacoustic signal over the whole measured wavelength range, which is different from the influence of light scattering effects on a single-ingredient solid powder. Based on this work, a method is proposed to preliminarily fast identify the light-absorbing ingredient in a solid mixture. Using the method, a drug tablet can be measured directly in solid state and hardly need sample preprocessing, and thus the time for composition analyses will be reduced significantly.

show abstract

“…The photoacoustic effect can be used to quantify the transfer of radiative energy to heat, in many cases enabling the direct measurement of absorption coefficients (Moosmüller et al, 2009). Photoacoustic instruments have been used since 1973 to study photolysis of NO 2 by comparing extinction and photoacoustic spectra of NO 2 (Harshbarger and Robin, 1973). The original system developed by Harshbarger and Robin ( Figure 1) used a 4-kW xenon lamp as the light source, a chopper to modulate the incident light, a monochromator for wavelengh scanning, a microphone, preamplifier, and lock-in amplifier to obtain the acoustic signal, and a radiometer to measure the optical power of the monochrometer output beam.…”

Section: Introductionmentioning

confidence: 99%

“…However, for a multispectral photoacoustic instrument, this research is not sufficient to quantify the photolysis of NO 2 , as explained at the end of the following paragraph. Comparison of the optical extinction and spectrophone (i.e., photoacoustic) spectra of NO 2 at 1333 Pa pressure (Harshbarger et al, 1973). Multispectral photoacoustic instruments and wide-spectralrange photoacoustic spectrometers are now available and are used to measure light absorption by aerosol and gases (Haisch et al, 2012;Ajtai et al, 2010;Lewis et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Influence of photolysis on multispectral photoacoustic measurement of nitrogen dioxide concentration

Tian

¹

,

Moosmüller

²

,

Arnott

³

2013

Journal of the Air & Waste Management Association

View full text Add to dashboard Cite

Multispectral photoacoustic instruments are commonly used to measure aerosol and nitrogen dioxide (NO 2 ) light absorption coefficients to determine the radiation budget of the atmosphere. Here a new photoacoustic system is developed to explore the effect of photolysis on the measured signal in a multispectral photoacoustic spectrometer. In this system, a 405-nm laser is used primarily as light source for photolysis. Additionally, a well-overlapped 532-nm laser, modulated at the resonant frequency of the photoacoustic instrument, is used to probe the NO 2 concentration. As a result, the photolysis effect at 405 nm can be observed by the photoacoustic instrument through the 532-nm laser. This work determines an 11% reduction of the photoacoustic signal caused by the photolysis effect for typical conditions, which needs to be taken into account when calibrating multispectral photoacoustic spectrometers with NO 2 .Implications: Multispectral photoacoustic instruments are commonly used to measure aerosol and nitrogen dioxide (NO 2 ) light absorption coefficients to determine the radiation budget of the atmosphere. A 405-nm laser is often used in these multispectral photoacoustic instruments. Although NO 2 absorbs strongly at 405 nm, it also has a strong photolysis pathway that is accessible by light of the same wavelength. Photolysis reduces the photoacoustic signal, necessitating special care when interpreting photoacoustic measurements. This paper offers a method for the multispectral photoacoustic instrument user to quantify the influence of the 405-nm NO 2 photolysis effect on the photoacoustic signal.

show abstract

“…Simple solutions of the thermal diffusion equation can be used only under certain conditions. Areas of use [283] include investigation of waste gases (see Fig. 43), absolute measurements of fluorescence quantum yields [284], determination of dye concentrations in films, investigation of thin films in catalysis [280,285], and biological and physiological problems such as the investigation of leaves and samples of skin or blood.…”

Section: Photoacoustic Spectroscopy (Pas)mentioning

confidence: 99%

Ultraviolet and Visible Spectroscopy

Gauglitz

¹

2008

Ullmann's Encyclopedia of Industrial Chemistry

0

View full text Add to dashboard Cite

The article contains sections titled: 1. Introduction 1.1. Comparison with Other Spectroscopic Methods 1.2. Development and Uses 2. Theoretical Principles 2.1. Electronic States and Orbitals 2.2. Interaction Between Radiation and Matter 2.2.1. Dispersion 2.2.2. Absorption 2.2.3. Scattering 2.2.4. Reflection 2.2.5. Band Intensity 2.3. The Lambert–BeerLaw 2.3.1. Definitions 2.3.2. Deviations from the Lambert ‐ Beer Law 2.4. Photophysics 2.4.1. Energy Level Diagram 2.4.2. Deactivation Processes 2.4.3. Transition Probability and Fine Structure of the Bands 2.5. Chromophores 2.6. Optical Rotatory Dispersion and Circular Dichroism 2.6.1. Generation of Polarized Radiation 2.6.2. Interaction with Polarized Radiation 2.6.3. Optical Rotatory Dispersion 2.6.4. Circular Dichroism and the Cotton Effect 2.6.5. Magnetooptical Effects 3. Optical Components and Spectrometers 3.1. Principles of Spectrometer Construction 3.1.1. Sequential Measurement of Absorption 3.1.2. Multiplex Methods in Absorption Spectroscopy 3.2. Light Sources 3.2.1. Line Sources 3.2.2. Sources of Continuous Radiation 3.2.3. Lasers 3.3. Selection of Wavelengths 3.3.1. Prism Monochromators 3.3.2. Grating Monochromators 3.3.3. Electro‐Acoustic and Opto‐Acoustic Wavelength Generation 3.4. Polarizers and Analyzers 3.5. Sample Compartments and Cells 3.5.1. Closed Compartments 3.5.2. Modular Arrangements 3.5.3. Open Compartments 3.6. Detectors 3.7. Optical Paths for Special Measuring Requirements 3.7.1. Fluorescence Measurement 3.7.2. Measuring Equipment for Polarimetry, ORD, and CD 3.7.3. Reflection Measurement 3.7.4. Ellipsometry 3.8. Effect of Equipment Parameters 3.9. Connection to Electronic Systems and Computers 4. Uses of UV ‐ VIS Spectroscopy in Absorption, Fluorescence, and Reflection 4.1. Identification of Substances and Determination of Structures 4.2. Quantitative Analysis 4.2.1. Determination of Concentration by Calibration Curves 4.2.2. Classical Multicomponent Analysis 4.2.3. Multivariate Data Analysis 4.2.4. Use in Chromatography 4.3. Fluorimetry 4.3.1. Inner Filter Effects 4.3.2. Fluorescene and Scattering 4.3.3. Excitation Spectra 4.3.4. Applications 4.4. Reflectometry 4.4.1. Diffuse Reflection 4.4.2. Color Measurement 4.4.3. Regular Reflection 4.4.4. Determination of Film Thickness 4.4.5. Ellipsometry 4.5. Resonance Methods 4.5.1. SurfacePlasmon Resonance 4.5.2. Grating Couplers 4.5.3. Other Evanescent Methods 4.5.4. Interferometric Methods 4.6. On‐Line Process Control 4.6.1. Process Analysis 4.6.2. Measurement of Film Thicknesses 4.6.3. Optical Sensors 4.7. Measuring Methods Based on Deviations from the Lambert – Beer Law 5. Special Methods 5.1. Derivative Spectroscopy 5.2. Dual‐Wavelength Spectroscopy 5.3. Scattering 5.3.1. Turbidimetry 5.3.2. Nephelometry 5.3.3. Photon Correlation Spectroscopy 5.4. Luminescence, Excitation, and Depolarization Spectroscopy, and Measurement of Lifetimes 5.5. Polarimetry 5.5.1. Sugar Analysis 5.5.2. Cellulose Determination 5.5.3. Stereochemical StructuralAnalysis 5.5.4. Use of Optical Activity Induced by a Magnetic Field 5.6. Photoacoustic Spectroscopy (PAS)

show abstract

Opto-acoustic effect. Revival of an old technique for molecular spectroscopy

Abstract: Over 90 years ago, Alexander Graham Bell described qualitatively the results of a series of experiments which have gone virtually unnoticed by succeeding generations of molecular spectroscopists

Cited by 156 publications

References 17 publications

Scattered light: improving photoacoustic spectral measurement with a drug tablet

Scattered light: improving photoacoustic spectral measurement with a drug tablet

Influence of photolysis on multispectral photoacoustic measurement of nitrogen dioxide concentration

Ultraviolet and Visible Spectroscopy

Contact Info

Product

Resources

About