Search

The effect of moisture on the adsorption of ammonia was systematically studied using different surface materials and humidity levels. The experimental water amount fractions varied between 6 and 18,000 mu molmol(-1), and the ammonia amount fraction was 400nmolmol(-1). The investigated materials included plain 316L stainless steel and stainless steel cured with Dursan, SilcoNert 2000 and halocarbon wax coatings. Furthermore, Teflon (PTFE) and polyvinylidene difluoride (PVDF) polymer surfaces were studied. Dynamically diluted ammonia, test tubes prepared with the investigated materials, a commercial ammonia analyzer based on cavity ring-down spectroscopy, and a commercial dew-point transmitter were employed. The adsorption was assessed quantitatively using continuous flow conditions and real-time monitoring of the adsorption process. The ammonia adsorption was found to increase substantially in dry conditions for all the studied materials except PVDF. The increase was largest for plain stainless steel which was the most adsorbing material. The coatings applied on stainless steel decreased the adsorption significantly in dry conditions. Polymers PVDF and PTFE were the least-adsorbing materials. In water amount fractions between 1000 and 10,000 mu mol mol(-1), the ammonia adsorption was at its lowest. The adsorption increased again above 1% humidity levels.

Adsorption of dynamically diluted ammonia at part-per-billion to low part-per-million concentrations in dry nitrogen was studied with treated and non-treated stainless steel and polymer test tubes. The treatments included electropolishing and two types of coatings based on amorphous silicon. Cavity ring-down spectroscopy with an external cavity diode laser operating in the near-infrared wavelength range was used to monitor the adsorption process in real time in continuous-flow conditions to obtain quantitative assessment of the adsorptive properties of the studied surfaces. The investigated polymers were all less adsorptive than any of the treated or non-treated stainless steel surfaces. Some of the commercial coatings reduced the adsorption loss of stainless steel by a factor of ten or more. Polyvinylidene fluoride was found to be superior (less adsorption) to the four other studied polymer coatings. The number of adsorbed ammonia molecules per surface area obtained at different ammonia gas phase concentra- tions was modeled with Langmuir and Freundlich iso- therms. The time behavior of the adsorption-desorption process occurring in the time scale of seconds and minutes was simulated with a simple kinetic model.

Biological monitoring usually relies on the collection of blood and urine samples. Although being non-invasive and providing an inextinguishable sampling pool, the analysis of exhaled breath is not ...

The environmental impacts of ammonia (NH3) in ambient air have become more evident in the recent decades, leading to intensifying research in this field. A number of novel analytical techniques and monitoring instruments have been developed, and the quality and availability of reference gas mixtures used for the calibration of measuring instruments has also increased significantly. However, recent inter-comparison measurements show significant discrepancies, indicating that the majority of the newly developed devices and reference materials require further thorough validation. There is a clear need for more intensive metrological research focusing on quality assurance, intercomparability and validations. MetNH3 (Metrology for ammonia in ambient air) is a three-year project within the framework of the European Metrology Research Programme (EMRP), which aims to bring metrological traceability to ambient ammonia measurements in the 0.5-500 nmol mol-1 amount fraction range. This is addressed by working in three areas: (1) improving accuracy and stability of static and dynamic reference gas mixtures, (2) developing an optical transfer standard and (3) establishing the link between high-accuracy metrological standards and field measurements. In this article we describe the concept, aims and first results of the project.

In this article we present the spectrum of H13C13CH near 13 000 cm−1 and its ro-vibrational analysis. Our high repetition rate cavity ringdown spectrometer was used to record the spectrum. Seven vibrational bands, including six to previously unobserved vibrational states, were recorded and rotationally analysed. The band origin of the cold 3010000 stretching vibrational combination transition ((31-) in the local mode notation) was measured at 12 960.28807(38) cm−1. The vibrational transition dipole moments were determined through intensity measurements of the spectral peaks. The values of the unperturbed vibrational transition dipole moment, , and the first Herman–Wallis coefficient, A 1, for the 3010000 band were found to be 1.1570(26)×10-9 D2 and -9.5(6)×10-4, respectively. The numbers in parentheses represent a one-standard error in the least significant digits.

Dans le cadre du Programme de Recherche Europeen en Metrologie (EMRP), un projet de trois ans a debute en juin 2014 avec l’objectif d’ameliorer la comprehension et la tracabilite metrologique des mesures d’ammoniac (NH3) ambient, dans le domaine 0.5 - 500 nmol/mol. Les trois tâches principales de ce projet sont 1) d’ameliorer l’exactitude et la stabilite de melanges de gaz de reference statiques et dynamiques, 2) de developper un etalon de transfert optique et 3) d’etablir un lien entre les standards metrologiques de haute precision et les mesures de terrain. Les resultats attendus de ce projet vont ameliorer l’exactitude et la fiabilite des estimations d’emissions et ainsi aider a l’evaluation de l’efficacite des mesures de reduction d’emission prescrites par les reglementations internationales. Dans cette publication nous decrivons le concept, les objectifs et les premiers resultats du projet.

This article describes the measurement and rotational analysis of several overtone vibrational bands of H 13 C 13 CH in the region between 12 100 cm −1 and 12 265 cm −1 using cavity ringdown spectroscopy. The recorded spectra contain three perpendicular bands and one parallel band. We present rotational parameters and vibrational term values for seven different vibrational states. In the experimental technique employed, the laser source is frequency stabilised to a transmission maximum of a high-finesse ringdown cavity. After each exponential decay, the laser re-acquires the lock and maintains it until the next ringdown is commenced. Some improvements have been made to the initial version of the experimental setup and these are discussed.

A high resolution vibration–rotation spectrum of deuterated monobromoacetylene (DCCBr) has been recorded with a Bruker IFS 120 Fourier Spectrometer in the wavenumber region 1700–2800 cm −1 , which covers the C–D and C C stretching fundamental ( ν 1 and ν 2 , respectively) and the C C and C–Br stretching vibrational combination ( ν 2 + ν 3 ) band systems. The analysis of the spectrum provides accurate vibrational term values and rotational constant for 20 vibration–rotation bands for both isotopic species, DCC 79 Br and DCC 81 Br.

Fourier-transform intra-cavity laser absorption spectroscopy has been used to record high-resolution vibration–rotation overtone spectra of carbon-13 substituted acetylenes, H 12 C 13 CH and H 13 C 13 CH, in the third CH stretching overtone region between 12 500 and 12 730 cm −1 . The observed spectra of both species contain only parallel bands for which rovibrational spectroscopic parameters have been determined. Several anharmonic resonances have been identified and rotationally analysed using traditional vibration–rotation theory. Altogether six bands, which include ν 1 + 3 ν 3 and 4 ν 3 for H 12 C 13 CH and ν 1 + 3 ν 3 for H 13 C 13 CH, have been observed for both species. Four of the six bands in each molecule are reported for the first time.

The laser-induced dispersed vibration–rotation fluorescence method has been developed further when compared with a previous publication [Saarinen et al., J. Chem. Phys. 110, 1424 (1999)]. More than one order of magnitude better signal-to-noise ratio has been achieved in the wave-number region 2900–3500 cm−1 by taking advantage of directionality of the fluorescence signal. The improvement has been applied to overtone spectroscopy of normal acetylene where for high CH stretching excitations separate spectra of ortho and para forms are obtained containing basically just single CH stretching vibrational quantum transitions from the pumped antisymmetric vibrational (ν1+3ν3(Σu+) and ν2+3ν3(Σu+)) and close-lying symmetric vibrational local mode (4ν3(Σg+) and ν1+ν2+2ν3(Σg+)) states. No nuclear spin conversion is observed in these spectra. Two new symmetric vibrational states (ν1+2ν2+4ν40(Σg+)(29%) and (50%)) have been observed and the precision of the spectroscopic parameters of previously published symmetric sta...

Two sensitive high-resolution laser absorption techniques, intra-cavity photo-acoustic and cavity ring-down spectroscopy (CRDS), are discussed in the context of laser-induced dispersed fluorescence studies of molecular overtone states. These absorption methods provide spectral data of comparable quality. The laser-induced dispersed fluorescence experiment offers new possibilities when applied to vibration–rotation states within the ground electronic states. Particularly, some new states in symmetrical molecules not accessible by one-photon absorption spectroscopy can be reached. Interesting collisional effects including nuclear spin conversion can also be investigated.

High-resolution vibration—rotation spectra of monochloroacetylene (HCCCl) have been recorded in two different wavenumber regions. Fourier transform infrared interferometer measurements in the 4000–10000cm−1 range have been performed with a resolution of 0.005–0.016cm−1 and titanium: sapphire ring laser intracavity photoacoustic measurements in the 12500–12600cm−1 and 12800–12860cm−1 regions have been carried out with a Doppler-limited resolution of about 0.02 cm−1. Altogether, 40 vibrational bands belonging to the HCC35 Cl and 15 bands belonging to the HCC37 Cl isotopic species have been rotationally assigned. A vibrational model, based on the conventional rectilinear normal coordinate theory including anharmonic Fermi, Darling—Dennison and vibrational l-type doubling resonances, has been used to attach vibrational labels to the bands. This approach is found to describe well the rovibrational energy level structure at least in the energy range covered in this work. The model shows that the CH oscillator b...

It is known that the oral cavity is a production site for mouth-exhaled NH3. However, the mechanism of NH3 production in the oral cavity has been unclear. Since bacterial urease in the oral cavity has been found to produce ammonia from oral fluid urea, we hypothesize that oral fluid urea is the origin of mouth-exhaled NH3. Our results show that under certain conditions a strong correlation exists between oral fluid urea and oral fluid ammonia (NH4(+)+NH3) (rs = 0.77, p 0.001). We also observe a strong correlation between oral fluid NH3 and mouth-exhaled NH3 (rs = 0.81, p 0.001). We conclude that three main factors affect the mouth-exhaled NH3 concentration: urea concentration, urease activity and oral fluid pH. Bacterial urease catalyses the hydrolysis of oral fluid urea to ammonia (NH4(+)+NH3). Oral fluid ammonia (NH4(+)+NH3) and pH determine the concentration of oral fluid NH3, which evaporates from oral fluid into gas phase and turns to mouth-exhaled NH3.

The cavity ring-down laser method using a continuously tunable titanium:sapphire ring laser with an external high-finesse cavity has been used to record a high-resolution overtone spectrum of a gaseous 12 C 2 H 2 sample in the wavenumber region 12 260–12 380 cm −1 . A direct non-linear least-squares fitting of the ring-down signal is found to lead to increased sensitivity when compared with the linear-least squares methods. Two new bands have been observed and rotationally analysed. A comparison of the new results with previous theoretical work shows a good agreement.

Photoacoustic overtone spectra of monobromoacetylene, HCCBr, have been recorded in the wavenumber region 11600-13400 cm-1 using a titanium:sapphire ring laser spectrometer. All together, eight overtone bands of HCC79Br and eight bands of HCC81Br have been observed in the rotational analysis. A Fermi resonance model based on conventional normal coordinate theory has been used to vibrationally assign the rotationally analyzed bands. The resonance model employed reproduces well the observed vibrational band origins and rotational constants. Copyright 1998 Academic Press. Copyright 1998Academic Press

The overtone spectrum of H 2 S has been studied by intracavity laser absorption spectroscopy in the wavenumber region 12 270–12 670 cm −1 . The rovibrational analysis has provided upper state rotational parameters for the three interacting vibrational states, (401), (104), and (024), observed in the region. The rotational levels of the first two states, constituting the local mode pair 41 ± , are strongly coupled by a strong H 22 type interaction. The (024) state is observed via a local perturbation. Altogether, 399 rovibrational lines have been assigned, including 172 rotational upper state sublevels which have been reproduced calculationally within the experimental accuracy of 0.015 cm −1 . A local mode type behavior is evidenced by the values of the rotational parameters.

Ammonia concentrations in exhaled breath (eNH(3)) and skin gas of 20 healthy subjects were measured on-line with a commercial cavity ring-down spectrometer and compared to saliva pH and plasma ammonium ion (NH4+), urea and creatinine concentrations. Special attention was given to mouth, nose and skin sampling procedures and the accurate quantification of ammonia in humid gas samples. The obtained median concentrations were 688 parts per billion by volume (ppbv) for mouth-eNH(3), 34 ppbv for nose-eNH3, and 21 ppbv for both mouth-and nose-eNH(3) after an acidic mouth wash (MW). The median ammonia emission rate from the lower forearm was 0.3 ng cm(-2) min(-1). Statistically significant (p < 0.05) correlations between the breath, skin and plasma ammonia/ammonium concentrations were not found. However, mouth-eNH(3) strongly (p < 0.001) correlated with saliva pH. This dependence was also observed in detailed measurements of the diurnal variation and the response of eNH(3) to the acidic MW. It is concluded that eNH(3) as such does not reflect plasma but saliva and airway mucus NH4+ concentrations and is affected by saliva and airway mucus pH. After normalization with saliva pH using the Henderson-Hasselbalch equation, mouth-eNH(3) correlated with plasma NH4+, which points to saliva and plasma NH4+ being linked via hydrolysis of salivary urea.

The infrared spectrum of a sample of natural monobromoacetylene (HCCBr) has been recorded with the Bruker IFS 120 Fourier spectrometer in the wavenumber region 1100-9800 cm −1 with a resolution close to the Doppler limit. The 2ν 4 , ν 1 , 2ν 1 , and 3ν 1 band systems have been analyzed. Altogether, 24 vibrational bands belonging to the HCC 79 Br and 26 bands belonging to the HCC 81 Br isotopic species have been observed and rotationally assigned. An anharmonic resonance model based on rectilinear normal coordinate theory has been used to produce the vibrational assignments for the observed bands.

A high-resolution vibration-rotation overtone spectrum of natural monobromoacetylene (HCCBr) has been recorded with a titanium:sapphire ring laser spectrometer in the wave number region 12520–12840 cm −1 . The main band assigned as 4 ν 1 , its accompanying hot bands and some overtone bands have been rotationally analysed. Altogether nine vibrational bands belonging to the HCC 79 Br and eleven bands belonging to the HCC 81 Br isotopic species have been observed. Vibrational assignments for most of the vibrational bands have been obtained by employing a simple Fermi resonance model based on normal coordinates.

A high-resolution vibration–rotation overtone spectrum of H13C12CH has been recorded with a Fourier transform infrared spectrometer in the wavenumber region 6400 to 6700 cm−1. The main band, assigned as the C–H stretching combination band ν1+ν3, and some overtone and hot bands have been rotationally analyzed. Altogether eight parallel bands have been observed. The vibrational labels have been deduced on the basis of the assignments of the fundamental ν3 antisymmetric C–H stretching band system.

The hydrogen cyanide (HCN) concentration in exhaled human breath and skin gas samples collected with different sampling techniques was measured using near-infrared cavity ring-down spectroscopy. The median baseline HCN concentrations in samples provided by 19 healthy volunteers 2-4 h after the last meal depended on the employed sampling technique: 6.5 parts per billion by volume (ppbv) in mixed (dead space and end-tidal) mouth-exhaled breath collected to a gas sampling bag, 3.9 ppbv in end-tidal mouth-exhaled breath, 1.3 ppbv in end-tidal nose-exhaled breath, 1.0 ppbv in unwashed skin and 0.6 ppbv in washed skin samples. Diurnal measurements showed that elevated HCN levels are to be expected in mouth-exhaled breath samples after food and drink intake, which suggests HCN generation in the oral cavity. The HCN concentrations in end-tidal nose-exhaled breath and skin gas samples were correlated, and it is concluded that these concentrations best reflect systemic HCN levels. 863QS Times Cited:2 Cited References Count:39

Intracavity photoacoustic overtone spectrum of monofluoroacetylene, HCCF, has been recorded in the wave number region 10 750–14 500 cm−1 with a titanium:sapphire ring laser. The spectrum contains many dense vibration–rotation band systems which can be resolved with Doppler limited resolution. Altogether 58 individual overtone bands have been analyzed rotationally. Many of the observed bands show perturbations of which some have been attributed to anharmonic resonance interactions. A Fermi resonance model based on conventional rectilinear normal coordinate theory has been used to assign vibrationally bands from this work and from earlier studies. Many of the observed vibrational term values and rotational constants can be reproduced well with this model. The results show the importance of the Fermi resonance interactions at the high overtone excitations.

A titanium:sapphire ring laser has been used in a high-resolution intracavity photoacoustic study of a natural sample of acetylene in the infrared region 11 480-11 880 cm−1. The spectra show a dense structure of vibration-rotation overtone hands of H 12C 12CH and H 12C 13CH. Altogether 35 hands have been analyzed rotationally yielding a set of upper-state rotational parameters. Some of the observed upper state perturbations have been explained successfully by Fermi, Coriolis, and rotational l-resonance interactions.

Diode laser-based continuous wave cavity ring-down spectroscopy (cw-CRDS) in the near-infrared region has been used to measure the mixing ratio of acetylene (C(2)H(2)) in ambient air. Detection limits of 120 parts per trillion by volume (pptv) for 20 min and 340 pptv for 70 s acquisition time were achieved without sample pre-concentration, measuring on a C(2)H(2) absorption line at 6565.620 cm(-1) (similar to 1523 nm). Several indoor and outdoor air samples were collected at different locations in the Helsinki metropolitan area and analyzed using static-cell measurements. In addition, flow measurements of indoor and outdoor air have been performed continuously over several days with a time resolution of down to one minute. Baseline acetylene levels in the range of 0.4 to 3 parts per billion by volume (ppbv), with a maximum around midday and a minimum during the night, were measured. Sudden high mixing ratios of up to 60 ppbv were observed in outdoor air during daytime on a minute time scale. In general, the indoor mixing ratios were found to be higher than those in outdoor air. The acetylene levels correlated with the ambient CO levels and with outdoor temperature. 678VQ Times Cited:4 Cited References Count:36

Hydrogen cyanide (HCN) in breath has been suggested as a diagnostic tool for cyanide poisoning and for cyanide-producing bacterial infections. To distinguish elevated levels of breath HCN, baseline data are needed. Background levels of HCN were measured in mixed exhaled air from 40 healthy subjects (26 men, 14 women, age 21-61 years; detection limit: 1.5 ppb; median: 4.4 ppb; range

A high-resolution vibration—rotation spectrum of acetylene has been obtained in the wavenumber region 17360–17560 cm −1 with a new ring-dye-laser spectrometer where an intracavity photoacoustic detection method has been used. The spectra obtained show large signal-to-noise ratios. Five new very weak bands have been observed and successfully analyzed to provide a set of vibrational term values and rotational constants.

Mouth-exhaled hydrogen cyanide (HCN) concentrations have previously been reported to originate from the oral cavity. However, a direct correlation between the HCN concentration in oral fluid and in mouth-exhaled breath has not been explicitly shown. In this study, we set up a new methodology to simultaneously measure HCN in the headspace of oral fluid and in mouth-exhaled breath. Our results show that there is a statistically significant correlation between stimulated oral fluid HCN and mouth-exhaled HCN (rs = 0.76, p < 0.001). This confirms that oral fluid is the main contributor to mouth-exhaled HCN. Furthermore, we observe that after the application of an oral disinfectant, both the stimulated oral fluid and mouth-exhaled HCN concentrations decrease. This implies that HCN production in the oral cavity is related to the bacterial and/or enzymatic activity.

High-resolution vibration-rotation spectra of gas-phase deuterobromoacetylene have been recorded in the 240-990 cm-1 infrared region. The analyzed band systems are rich in hot bands and have a high density of lines. Five band systems and a total of 124 vibration-rotation bands of the isotopic species DCC79Br and DCC81Br have been rotationally analyzed. Accurate rotational parameters and vibrational wavenumbers for 33 vibrational states of each species have been obtained from the rotational analysis. l doubling and rotational l resonance have been observed on some states and the respective resonance parameters have been obtained through nonlinear least-squares optimization. A Fermi resonance block model with perturbation terms has been used for the analysis of the vibrational states. With optimized parameters, the model produces root-mean-square deviations of observed - calculated wavenumbers of about 0.3 cm-1 for both isotopic species. Copyright 1999 Academic Press.

The first and second C-H overtone vibration-rotation absorption spectra of monoiodoacetylene (HCCI) have been recorded using an FTIR spectrometer with an instrument resolution of about 0.005 cm-1 (0.9/MOPD). The third overtone spectrum has been obtained using a titanium:sapphire ring laser spectrometer with a spectral resolution of about 0.02 cm-1. Due to anharmonic resonances like Fermi and Darling-Dennison resonances, accompanying bands can be observed close to the main overtone band. All the observed bands have been rotationally analyzed. Published vibrational data together with present results are used in a model which includes anharmonic resonances. Vibrational assignments of the observed bands are based on this calculation. The agreement between calculated and observed energy levels is good considering the amount of data available. Copyright 1997 Academic Press. Copyright 1997Academic Press

We have measured the acetylene concentration in the exhaled breath of 40 volunteers (31 non-smokers, nine smokers) using near-infrared cavity ring-down spectroscopy. The acetylene levels were found to be the same as in ambient air for non-smokers, whereas elevated levels were observed for smokers. Real-time measurements with sub-second time resolution have been applied to measure the elimination kinetics of acetylene in breath after exposure to tobacco smoke. Three exponential time constants can be distinguished from the data and these can be used to define the residence times for different compartments, according to the multi-compartment model of the human body. 687DS Times Cited:2 Cited References Count:29

The first CH stretching overtone band system of diacetylene (1,3-butadiyne) in the range of 6350–6750 cm−1 has been recorded with a high resolution Fourier transform infrared interferometer at room temperature. Although the spectrum obtained may be resolved rotationally, two different computational procedures have been used to enhance the resolution due to severe congestion in the central parts of the band system. It has become possible both to find one new band and to achieve higher precision. Altogether five bands with the lower state being the ground vibrational state have been analysed rotationally. The results obtained are discussed in the context of a previous molecular beam study of a small part of the same band system.

We describe the design, construction, and initial performance evaluation of a high-repetition-rate cavity ringdown spectrometer. The spectrometer is based on the use of the Pound-Drever-Hall technique to lock the laser frequency to the maximum of a transmission fringe of the interferometer used as a sample cell. This results in continuous injection of light into the interferometer. The injection is repetitively interrupted with an acousto-optical modulator to generate ringdowns (exponential decays) at a typical rate of 10 kHz. Averaging of these large numbers of fitted ringdown times allows us to attain a minimum detectable absorption of 1.43×10−11 cm−1 Hz−1/2 short term and 9.0×10−11 cm−1 Hz−1/2 long term. In addition, the spectrometer has a continuous tuning capability of ∼1 cm−1, which allows the use of standard linearization and frequency calibration techniques for the spectrum. To illustrate the operation and sensitivity of the spectrometer, part of the Q-branch of a weak acetylene overtone has been recorded.