Denis D. Arslanov

Current methods for detecting ethylene in plants

BACKGROUND In view of ethylenes critical developmental and physiological roles the gaseous hormone remains an active research topic for plant biologists. Progress has been made to understand the ethylene biosynthesis pathway and the mechanisms of perception and action. Still numerous questions need to be answered and findings to be validated. Monitoring gas production will very often complete the picture of any ethylene research topic. Therefore the search for suitable ethylene measuring methods for various plant samples either in the field, greenhouses, laboratories or storage facilities is strongly motivated. SCOPE This review presents an update of the current methods for ethylene monitoring in plants. It focuses on the three most-used methods - gas chromatography detection, electrochemical sensing and optical detection - and compares them in terms of sensitivity, selectivity, time response and price. Guidelines are provided for proper selection and application of the described sensor methodologies and some specific applications are illustrated of laser-based detector for monitoring ethylene given off by Arabidopsis thaliana upon various nutritional treatments. CONCLUSIONS Each method has its advantages and limitations. The choice for the suitable ethylene sensor needs careful consideration and is driven by the requirements for a specific application.

Real-time, subsecond, multicomponent breath analysis by Optical Parametric Oscillator based Off-Axis Integrated Cavity Output Spectroscopy

Breath analysis is an attractive field of research, due to its high potential for non-invasive medical diagnostics. Among others, laser-based absorption spectroscopy is an excellent method for the detection of gases in exhaled breath, because it can combine a high sensitivity with a good selectivity, and a high temporal resolution. Here, we use a fast-scanning continuous wave, singly-resonant Optical Parametric Oscillator (wavelength range between 3 and 4 μm, linewidth 40 MHz, output power > 1 W, scanning speed 100 THz/s) with Off-Axis Integrated Cavity Output Spectroscopy for rapid and sensitive trace gas detection. Real-time, low- ppbv detection of ethane is demonstrated in exhaled human breath during free exhalations. Also, simultaneous, real-time multi-component gas detection of ethane, methane and water was performed in exhaled breath using a wide spectral coverage over 17 cm(-1) in 1 second. Furthermore, real-time detection of acetone, a molecule with a wide absorption spectrum, was shown in exhaled breath, with a sub-second time resolution (0.4 s).

Optical parametric oscillator-based photoacoustic detection of hydrogen cyanide for biomedical applications

Abstract. A versatile, continuous wave, optical parametric oscillator is used in combination with photoacoustic spectroscopy for long-term trace gas experiments of volatile compounds emitted by biological samples. The optical parametric oscillator-based spectrometer (wavelength near 3 μm, 8-MHz linewidth, output power ∼1  W) is successfully tested for the detection of hydrogen cyanide (HCN) emission from clover leaves, and Pseudomonas bacteria; in addition, the presence of HCN in exhaled human breath is measured. For specific experiments, the spectrometer is operated continuously up to 10 days and has a detection limit of 0.4 parts-per-billion volume of HCN in air over 10 s, using the P8 rotational line in the ν3 vibrational band of HCN at 3287.25  cm−1. This results in an overall sensitivity of the system of 2.5×10−9  cm−1 Hz−1/2.

Optical parametric oscillator based off-axis integrated cavity output spectroscopy for rapid chemical sensing

An optical parametric oscillator (OPO), pumped by a fiber-amplified diode laser, is combined with off-axis integrated cavity output spectroscopy (OA-ICOS). The cw OPO (power 1.2 W, tunability 3-4 μm, 5 cm(-1) mode-hop-free tuning) has a tuning speed of 100 THz/s, which is ideal for rapid and sensitive trace gas detection. Combined with OA-ICOS, a detection limit of 50 parts per trillion by volume (1×10(12)) of ethane (C(2)H(6)) in nitrogen was obtained in 0.25s at 2997 cm(-1), corresponding to a noise equivalent absorption sensitivity of 4.8×10(-11) cm(-1) Hz(-1/2). The system demonstrates real-time measurements of methane and water in exhaled human breath.

Real-time monitoring of hydrogen cyanide (HCN) and ammonia (NH3) emitted by Pseudomonas aeruginosa

We present the real-time monitoring of hydrogen cyanide (HCN) production from Pseudomonas aeruginosa (P. aeruginosa) strains in vitro, using laser-based photoacoustic spectroscopy. Simultaneously, the production of ammonia (NH3) was measured, and the influence of different factors (e.g. the medium, temperature and antibiotics treatment) was assessed. Both reference strains and clinical isolates of patients with CF were studied, and compared to other pathogens commonly present in lungs/airways of CF patients. Hydrogen cyanide production starts to rise as soon as P. aeruginosa bacteria reach the stationary phase ((9.0-9.5) × 10(9) colony forming units, CFUs), up to concentrations of 14.5 microliters per hour (µl h(-1)). Different strains of P. aeruginosa produced HCN to varying degrees, and addition of tobramycin strongly reduced HCN production within 2 h from application. Burkholderia cepacia also produced HCN (up to 0.35µl h(-1) in 9.0  ×  10(9) CFU) while other pathogens (Aspergillus fumigatus, Stenotrophomonas maltophilia, Mycobacterium abscessus) did not produce detectable levels. Our study reveals for the first time a broad overview of the dynamics of the HCN production in vitro.

Optical parametric oscillator based detection of hydrogen cyanide for bio-medical applications

There is an increasing interest in the development of sensitive and selective methods to detect hydrogen cyanide (HCN) from biological samples [1,2]. Several studies have been conducted with different types of matrices, such as water, soil, air, exhaled breath and food. Different methods have been used to monitor HCN; however, most of them are complex and involve a large amount of manipulations of samples or the use of solvents. Additionally, they feature slow response time (in the order of minutes) and therefore hardly any continuous gas monitoring over days or weeks can be performed. In most cases the reported detection limit is in the part-per-million volume (ppmv) mixing range, which is not sufficient to perform trace emission experiments on small amounts of biological samples. Thus, the development of more sensitive methods able of measuring ppbv (parts-per-billion volume) level of HCN, becomes very motivated.

Optical parametric oscillator based detection of HCN for bio-medical applications

A cw OPO, combined with photoacoustic spectroscopy, is used for the detection of HCN emission from leaves, seeds and Pseudomonas bacteria; next to its presence in human breath, with a detection limit of 0.4 ppbv (10s).

OPO based Off-Axis Integrated Cavity Output Spectroscopy for rapid chemical sensing

We presented rapid and sensitive trace gas detector based on a high power and fast scanning cw OPO in combination with Off-Axis Integrated Cavity Output Spectroscopy. A detection limit of 2×10^-9 cm^-1 Hz^-1/2 was obtained.