CO2 laser photothermal deflection (limit 1 nl I-') and photoacoustic detection (limit 6 pl I-') systems were used to measure ethylene emission rates from point sources of a wide range of mature nonclimacteric and climacteric fruits. In addition, an infrared gas analyzer was used to measure CO2 from the same samples. As well as total rates, the percentages emanating from the skin, tissue at the distal end (floral scar) and the pedicel were established. Possible links with fruit behaviour during abscission are discussed.

Using a CO2 laser photoacoustic spectroscopy with intracavity setup and multicomponent method we have done measurement on the ammonia, ehtylene and acetone gas concentrations in the breath of liver disease patients and in the healthy volunteers. The results of multicomponent analysis show that the average concentration of ammonia gas obtained from the breath of liver disease patients and healthy volunteers are (3.27 ± 0.75) and (1.34 ± 0.24) ppm, respectively. The highest and the lowest ammonia gas concentration of liver disease patients are 4.77 and 1.99 ppm. While, the highest and the lowest ammonia gas concentration of healthy volunteers are 1.89 and 1.08 ppm. For the ethylene and acetone concentrations, we found no significant difference between the average concentrations in the liver disease patients and in the healthy volunteers.

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Abstrak -Pengembangan sistem deteksi gas hembus pernapasan manusia yang memiliki kepekaan tinggi telah dilakukan dalam penelitian ini. Laser QCL (Quantum Cascade Laser) kontinyu dengan panjang gelombang 4610 nm sebagai sumber radiasi yang dikombinasikan dengan teknik spektroskopi off-axis ICOS (integrated cavity output spectroscopy) digunakan untuk medeteksi gas Karbon Monoksida (CO) bertekanan rendah. Sel sampel gas dengan panjang 15 cm yang dilengkapi dengan cermin high-finesse sekaligus berfungsi sebagai rongga resonator laser dengan lintasan optik efektif mencapai 400 m. Batas deteksi sebesar 1 ppbv dalam waktu akuisisi kurang dari 2 detik telah berhasil dicapai. Pendeteksian kasar pada gas hembus pernapasan manusia telah berhasil mendeteksi gas CO sebesar 0,7 ppmv.Abstract -An ultra sensitive exhaled breath gas detection system has been developed. DFB cw quantum cascade laser (QCL) centered at 4610 nm as a radiation source was used in combination with an off-axis integrated cavity output spectroscopy for carbon monoxide (CO) gas detection in a low gas pressure. a 15 cm long high-finesse cavity with an effective optical path length of 400 m has also been used as a sample gas cell. We demonstrated detection limit of 1 ppb with less than 2 second averaging time. 0,7 ppmv concentration of CO has been identified on a robust measurement of an exhaled breath detection.

Telah dilakukan monitoring beberapa parameter difusi (waktu relaksasi, koefisien resistansi dan koefisien difusi) gas SF 6 di dalam buah tomat (Lycopersicon esculentum) dengan menggunakan metode spektroskopi foto-akustik (SFA) laser CO 2 . Gas SF 6 menyerap paling kuat pada garis 10P16 dan etilen pada garis laser 10P14 dengan frekuensi resonansi sebesar 1650±5 Hz. Batas deteksi terendah (BDT) yang dihasilkan oleh SFA untuk gas SF 6 diperoleh 2, 6±0, 4 ppt dan untuk etilen sebesar 0, 32±0, 03 ppb. Monitoring difusi gas SF 6 pada buah tomat dan pengukuran emisi etilen dalam kurun waktu 15 hari menghasilkan pola karakteristik waktu relaksasi, koefisien resistansi dan koefisen difusi terhadap emisi etilen. Dalam proses pematangan, waktu relaksasi dan koefisien resistansi buah tomat mengalami penurunan masing-masing dari 2, 85 ± 0, 07 menit ke 0, 86 ± 0, 01 menit dan dari (5, 95 ± 0, 27) × 10 2 detik cm −1 ke (1, 53 ± 0, 06) × 10 2 detik cm −1 .Sedang koefisien difusi mengalamai kenaikan dari (1, 73 ± 0, 01) × 10 −2 cm 2 detik −1 ke (6, 70 ± 0, 03) × 10 −2 cm 2 detik −1 . Dari hasil tersebut dapat direkomendasikan kepada pengelola pengendalian pematangan buah tomat untuk mendapatkan optimasi parameter difusi sehingga diperoleh pematangan sesuai dengan kebutuhan pasar.Kata Kunci : Spektroskopi fotoakustik, waktu relaksasi, koefisien resistensi & difusi, buah tomat. AbstractMonitoring of diffusion parameters (relaxation time, resistance coefficient and diffusion coefficient) has been carried out by SF 6 gas in tomato fruit (Lycopersicon esculentum) using CO 2 laser photoacoustic spectroscopy (PAS) method. SF 6 gas absorbs the strongest on the 10P16 and ethylene lines on the 10P14 laser line with a resonant frequency of 1650 ± 5 Hz. The lowest limit detection (LLD) produced by PAS for SF 6 gas was 2.6 ± 0.4 ppt and for ethylene was 0.32±0, 0.03 ppb. Monitoring of diffusion of SF 6 gas in tomatoes and measurement of ethylene emissions within 15 days resulted in a characteristic pattern of relaxation time, resistance coefficient and diffusion coefficient on ethylene emissions. In the ripening process, the relaxation time and the tomato resistance coefficient decreased respectively from 2.85 ± 0.07 minutes to 0.86 ± 0.01 minutes and from (5.95 ± 0.27) × 10 2 seconds cm −1 to (1, 53 ± 0, 06) × 10 2 seconds cm −1 . While the diffusion coefficient has increased from (1.73 ± 0.01) × 10 −2 cm 2 seconds −1 to (6.70 ± 0.03) × 10 −2 cm 2 seconds −1 . From the results, it can be recommended to the manager of control of ripening of tomatoes to get optimization of diffusion parameters so that maturation can be obtained according to market needs.