Photoacoustic Instruments for Practical Applications: Present, Potentials, and Future Challenges

Bozóki, Zoltán; Pogány, Andrea; Szabó, Gábor

doi:10.1080/05704928.2010.520178

Cited by 127 publications

(119 citation statements)

References 83 publications

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“…Selectivity means that PA is not only a zero background technique (i.e. in the absence of light absorption no PA signal is generated) but in addition to that the PA response is inherently unaffected by the non-absorbing aerosol particles present in the sampled aerosol stream, and also by the non-absorbing compounds of the individual aerosol particles (Moosmüller et al, 2009;Bozóki et al, 2011). The accuracy of the recently published PA instruments for aerosol measurement is in the range of a few percent, which is at least an order of magnitude better than that of the most commonly used filter-based instruments, even when their readings are corrected posteriorly after the measurement .…”

Section: Introductionmentioning

confidence: 99%

Mass-specific optical absorption coefficients and imaginary part of the complex refractive indices of mineral dust components measured by a multi-wavelength photoacoustic spectrometer

et al. 2015

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Abstract. Mass-specific optical absorption coefficients (MACs) and the imaginary part (κ) of the refractive indices of various mineral dust components including silicate clays (illite, kaolin and bentonite), oxides (quartz, hematite and rutile), and carbonate (limestone) were determined at the wavelengths of 1064, 532, 355 and 266 nm. The MAC values were calculated from aerosol optical absorption coefficients measured by a multi-wavelength photoacoustic (PA) instrument, the mass concentration and the number size distribution of the generated aerosol samples as well as the size transfer functions of the measuring instruments. Values of κ were calculated from the measured and particle-loss-corrected data by using a Mie-theory-based retrieval algorithm. The determined values could be used for comparisons with calculated wavelength-dependent κ values typically deduced from bulkphase measurements by using indirect measurement methods. Accordingly, the presented comparison of the measured and calculated aerosol optical absorption spectra revealed the strong need for standardized sample preparation and measurement methodology in case of bulk-phase measurements.

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Section: Introductionmentioning

confidence: 99%

Mass-specific optical absorption coefficients and imaginary part of the complex refractive indices of mineral dust components measured by a multi-wavelength photoacoustic spectrometer

et al. 2015

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“…However, this technique may only be applied to rather polluted air due to its limited sensitivity (Lack et al, 2006;Bozoki et al, 2011). The 4λ-PAS system used in this study is described by Ajtai et al (2011), where the measurement results are also presented.…”

Section: Photoacoustic Spectrometer -The 4λ-pasmentioning

confidence: 99%

Real-Time Determination of Absorptivity of Ambient Particles in Urban Aerosol in Budapest, Hungary

Nagy

Czitrovszky

Kerekes

et al. 2016

Aerosol Air Qual. Res.

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The absorption properties of ambient urban aerosols as well as their size distributions were measured in real-time using a dual wavelength optical particle spectrometer (DWOPS). A photoacoustic spectrometer (PAS) was simultaneously used to directly measure light absorptivity of the particles in question along with an Aethalometer and a commercial optical particle counter (OPC). The sizing performance of the DWOPS was compared with the commercial OPC unit showing very good agreement. The data from DWOPS, PAS and Aethalometer instruments are presented and show the potential of the DWOPS technique for a direct and simple assessment of the absorbing part of the complex refractive index of ambient particles as a function of particle size.

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“…Telecommunication NIR diode , total pressure of 1000, 500 and 300 mbar (a). Absorbance spectra at a total pressure of 300 mbar of 100 ppmv H 2 S in a standard air matrix with 100 ppmv water and 500 ppmv CO 2 content and 100 ppmv H 2 S in a possible process air matrix of 10,000 ppmv H 2 O and 5000 ppmv CO 2 lasers have been used by several groups in various photoacoustic applications with traditional capacitive microphones as the pressure sensing device [24]. A novel detection approach, developed by Wilcken and Kauppinen [35], utilizes a silicon cantilever as an optical microphone with interferometric measurement of the sensor displacement and is termed cantilever-enhanced photoacoustic spectroscopy (CEPAS) [27,35,36].…”

Section: Cantilever-enhanced Photoacoustic Spectroscopymentioning

confidence: 99%

“…Although the detection of H 2 S concentrations of several ppb has been demonstrated by employing integrated cavity output spectroscopy approach (ICOS) [20], such sensitivities are difficult to obtain in field measurements as the robustness of this kind of systems remains limited [21,22]. Possible alternatives to bulky multipass absorption or delicate sensing schemes based on cavity spectroscopy are photoacoustic H 2 S measurement strategies [23][24][25][26]. A fully developed and industry-tailored H 2 S sensor to meet the specific selectivity requirements based on photoacoustic spectroscopy employing dual-channel longitudinal-type resonator cell with capacitive microphone readout and a LOD of 0.5 ppmv is described in [23].…”

Section: Introductionmentioning

confidence: 99%

Cantilever-enhanced photoacoustic detection of hydrogen sulfide (H2S) using NIR telecom laser sources near 1.6 µm

Moser

Lendl

2016

Appl. Phys. B

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concentrations as low as 500 pptv manifesting in the characteristic odor of rotten eggs can already be detected by the human olfactory sense, the total loss of olfactory sensation starts at 150-200 ppmv [3]. Because of the wide occurrence of H 2 S in industrial processes and its often negative impact on process stabilities and product quality, its concentration needs to be tightly monitored. Furthermore, safety considerations and legal concentration limits also necessitate the accurate determination of H 2 S levels. In practice, concentrations ranging from sub-ppm levels at low pressures to several per cents at atmospheric conditions need to be monitored. Due to such diverse requirements, H 2 S analyzers based on different measurement technologies have been developed and are in industrial use. Apart from spectroscopic techniques based on absorption measurements, a range of other analytical techniques such as pulsed UV fluorescence [4], sulfur chemiluminescence [5], colorimetry employing a lead acetate tape [6], flame photometry as detector in gas chromatography [7] as well as electrochemical detection techniques ranging from potentiometric, galvanic, coulometric and amperometric detection [8] is frequently employed. It is interesting to note that in the petrochemical industry the lead acetate tape method is still in frequent use. Also, gas chromatographic methods are popular as they can be used to detect several components almost simultaneously, but this technique requires preparation and extraction of the sample gas leading to a time-consuming measurement. A general drawback of nonspectroscopic techniques is the fact that they do not allow for direct measurements. This, however, also applies to H 2 S detection based on UV fluorescence as this technique requires sample combustion as well as detection by chemoluminescence, where addition of reagents is required.Most of the spectroscopic techniques are based on the detection of the absorption spectrum of the molecules in Abstract Sensitive detection of hydrogen sulfide (H 2 S) at different pressure levels using a cantilever-enhanced photoacoustic detector in combination with a telecom NIR L-band laser source is reported. Amplitude and wavelength modulation schemes for photoacoustic signal generation are compared. A detection limit (3σ) of 8 ppmv was achieved for amplitude modulation mode with a 50-s averaging time for the H 2 S absorption near 1.6 µm. As compared to simulated spectra, the cantilever-enhanced photoacoustic detection approach in combination with the sufficiently stable and narrow bandwidth NIR laser is able to reproduce the rotationally resolved H 2 S spectrum at low pressures of 300 mbar.

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Photoacoustic Instruments for Practical Applications: Present, Potentials, and Future Challenges

Cited by 127 publications

References 83 publications

Mass-specific optical absorption coefficients and imaginary part of the complex refractive indices of mineral dust components measured by a multi-wavelength photoacoustic spectrometer

Mass-specific optical absorption coefficients and imaginary part of the complex refractive indices of mineral dust components measured by a multi-wavelength photoacoustic spectrometer

Real-Time Determination of Absorptivity of Ambient Particles in Urban Aerosol in Budapest, Hungary

Cantilever-enhanced photoacoustic detection of hydrogen sulfide (H2S) using NIR telecom laser sources near 1.6 µm

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