Real-time and in situ determination of ammonia concentrations in the atmosphere by means of intermodulated stark resonant CO2 laser photoacoustic spectroscopy

Sauren, H.; Gerkema, E.; Bićanić, D.; Jalink, H.

doi:10.1016/0960-1686(93)90075-a

Cited by 10 publications

(5 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Several groups have developed photothermal detection techniques that we will compare to PTI. Rooth et al, Sauren et al, , Moeckli et al, and Thony and Sigrist detected pressure waves (sound) from modulated infrared absorption by ammonia using microphones in photothermal acoustic cells (PTA). de Vries et al ,, and Zimerman and Boccara , detected the photothermal deflection (PTD) of a He−Ne probe beam by a modulated CO 2 laser beam.…”

Section: Resultsmentioning

confidence: 99%

“…PTA detectors built by Sauren et al, ,, Rooth et al, and Moeckli et al , do not as yet have detection limits below 1 ppb and require signal integration or zeroing times between 40 s and several minutes. A common problem with resonant PTA is resonant frequency noise and drift with water vapor concentration and temperature, which is avoided by PTI detection at a quiet, nonresonant frequency.…”

Section: Resultsmentioning

confidence: 99%

“…A common problem with resonant PTA is resonant frequency noise and drift with water vapor concentration and temperature, which is avoided by PTI detection at a quiet, nonresonant frequency. Electric field modulation has been used with PTA by Sauren et al, , with detection at the combined laser and Stark modulation frequency. A disadvantage of measuring these sidebands of the mixed signal is that the signal voltages are very small for concentrations of ammonia in the low-ppb range, less than 1 μV …”

Section: Resultsmentioning

confidence: 99%

See 2 more Smart Citations

A Photothermal Interferometer for Gas-Phase Ammonia Detection

1999

View full text Add to dashboard Cite

Detection of gas-phase ammonia is particularly challenging because ambient ammonia concentrations may be less than 1 ppb (molecules of NH(3) per 10(9) molecules of air), ammonia sticks to many materials commonly used to sample air, and particles containing ammonium may interfere with gas-phase measurements. We have built a new and sensitive photothermal interferometer to detect gas-phase ammonia in situ, under typical atmospheric conditions. Ammonia molecules in sampled air absorb infrared radiation from a CO(2) laser at 9.22 μm, with consequent collisional heating, expansion, and refractive index change. This change in refractive index is detected as a phase shift in one arm of a homodyne interferometer. Measurements of vibrational and electrical noise in the interferometer correlate to an instrumental lower limit of detection of 6.6 ppt ammonia in 1 s. The CO(2) laser output is modulated at 1.2 kHz, and the ac signal from the interferometer is measured with a lock-in amplifier. The detector is zeroed by sampling through a H(3)PO(4)-coated denuder tube and is calibrated by dynamic dilution of two permeation tube outputs and by standard addition. Signal gain is insensitive to CO(2) or H(2)O in the sample, and the signal is linear over 5 orders of magnitude. The instrument 2σ precision is 31 ppt when the signal is integrated for 100 s and 250 ppt with a 1-s integration time. The windowless sample cell and inlet is fabricated entirely of glass to minimize sample loss and hysteresis. The instrument response time is demonstrated to be about 1 s.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

A Photothermal Interferometer for Gas-Phase Ammonia Detection

1999

View full text Add to dashboard Cite

show abstract

“…79 Additionally, another procedure for NH 3 monitoring reported a detection limit of 2-3 ppbV in ambient air. 80 Moreover, 12 trace gases were measured simultaneously, mainly VOCs, in collected samples from car exhausts with the CO laser PA system. 81 Lead salt diode lasers.…”

Section: Powerful Ir Sourcesmentioning

confidence: 99%

The ways to the trace level analysis in infrared spectroscopy

et al. 2011

View full text Add to dashboard Cite

“…Since meaningful information is obtained as the difference between these two quantities, such an indirect approach provides no satisfacfory results at [ow analyte concentrations. In recent years the photoacoustic (PA) approach, a direct method to measure the absorption, was shown to be a very good candidate technique for trace analysis of many gaseous pollutants (Bicanic 1992, Meyer and Sigrist 1990, Olafsson 1990, Sauren et al 1993, in particular when combined with strong infrared sources such as for example CO and CO2 lasers. The PA-based instrument for detection of TOC implies thus the intrinsic necessity for a sensitive CO2 detector.…”

Section: Introductionmentioning

confidence: 99%