Pulsed amperometric detection of furan compounds in transformer oil

The failure of high voltage transformers can result in significant cost and supply implications to both power supplier and consumer alike and in extreme cases may result in explosion, serious injury or death. Transformer failure can be predicted by measuring furanics present in the oil, produced by the thermolytic breakdown of cellulosidic insulators. Failing units can have furanic levels of up to 10 μg ml⁻¹. The use of pulsed amperometric detection (PAD) to measure furanics in transformer oils in real time is reported here. Oils were examined by pre-extraction or direct suspension in aqueous measurement solution or by solubilisation and direct PAD measurement in organic solvents. Linear relationships between PAD response and furanic concentration was found for 2-furaldehyde and furfuryl alcohol (F-OH) across the range of 0–10 μg ml⁻¹, with PAD proving most sensitive to the latter compound. PAD was performed directly in the organic phase in t-butanol with 0.1 M tetramethyl ammonium hydroxide, with aged oils containing >2 μg ml⁻¹ of 2-furaldehyde yielding data within close agreement (<9%) of a standard chromatographic method. The simplicity and rapidity of this method offers the power transmission industry a means of monitoring furanic levels in transformers in real time, thereby reducing the risk of uncontrolled transformer failure.     

Pharmacokinetics, tissue distribution and excretion of a new photodynamic drug deuxemether

Deuxemether was a new photodynamic drug effective for many kinds of solid tumor therapy, which was mainly composed of 3-(or 8-)-(1-methoxyethyl)-8-(or 3-)-(1-hydroxyethyl)-deutero-porphyrin IX (MHD) and 3,8-di(1-methoxyethyl)-deuteroporphyrin IX (DMD). The aims of this study were to elucidate its pharmacokinetic characteristics, tissue distribution, plasma protein binding and excretion properties and underlying mechanisms of deuxemether in rats based on the simultaneous determination of MHD and DMD. The pharmacokinetic profiles of both MHD and DMD in rats after intravenous doses were linear and best fitted to a two compartment model, characterized with a rapid distribution phase (MHD: t_1/2, 0.09–0.14 h; DMD: t_1/2, 0.07–0.11 h) and a relatively slow elimination phase (MHD: t_1/2β, 2.03–3.20 h; DMD: t_1/2β, 2.51–3.20 h). The tissue distributions of MHD and DMD in rats were rather limited as evidenced from their low distribution volume (0.75–1.70 L/kg) and the results of tissue distribution study. Protein binding of MHD and DMD were moderate (65.36–89.99% for MHD; 45.43–76.23% for DMD), independent of drug concentrations and similar between human and rat plasma over a concentration range of 0.50–50.0 μg/mL. Both MHD and DMD were predominantly (>74.1%) eliminated from rats as the parent drugs through the hepatobiliary systems and finally excreted into the feces. The multidrug resistance-associated proteins 2 (MRP2) inhibitors, bromosulfophthalein and probenecid, substantially inhibited the hepatobiliary elimination of MHD and DMD while the P-gp inhibitor digoxin had little effect, suggesting that MRP2 may contribute to the rapid and extensive hepatobiliary excretion of deuxemether. There were no significant differences between MHD and DMD for all pharmacokinetic characteristics studied. In conclusion, this study provided firstly the full pharmacokinetic characteristics and mechanisms of deuxemether, which would be helpful for its clinical regiment design.     

Promotion of hydrocarbon selectivity in CO2 hydrogenation by Ru component

We investigated catalytic behavior of iron in CO₂ hydrogenation with and without a ruthenium component. Calcined iron-based catalysts were reduced by H₂ and characterized by XRD, BET surface area and CO₂, CO and C₂H₄ temperature-programmed desorption (TPD), and tested for CO₂ hydrogenation. When Fe-K/γ-Al₂O₃ was used as a catalyst, CO₂ conversion was 36%, but when Fe-Ru-K/γ-Al₂O₃ was used, CO₂ conversion was 41%. The product selectivities for catalysts with and without the ruthenium component were also compared. Fe-K/γ-Al₂O₃ exhibited higher methane (16 mol%) and C₂–C₄ selectivity (39.6 mol%) than Fe-Ru-K/γ-Al₂O₃. The main products obtained with Fe-Ru-K/γ-Al₂O₃ were higher hydrocarbons such as C₅⁺ hydrocarbons. For Fe-Ru-K/γ-Al₂O_3, the product distribution followed the Anderson–Schultz–Flory (ASF) distribution. However, in the case of Fe-Ru-K/γ-Al₂O₃, the hydrocarbon distribution deviates from the ideal ASF distribution. It is concluded that the readsorption rates of the primary hydrocarbon product increase exponentially with chain length in the ruthenium promoted catalytic system. The behavior of catalysts with and without the ruthenium will be explained by the CO₂-, CO- and C₂H₄– profiles. In this study, it was confirmed that ruthenium component promoted the readsorption ability of -olefin, and then the chain length of hydrocarbon is higher. In addition, the microcrystalline wax produced in CO₂ hydrogenation was a high-crystalline and olefin-rich hydrocarbon.     

Determination of neutral oligosaccharides in vegetables by matrix-assisted laser desorption/ionization mass spectrometry

In this work, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI–TOF–MS) was used for characterization of oligosaccharides in some vegetable samples (Jerusalem artichoke, red onion, glucose syrup from potatoes). The selection of suitable matrix has critical importance for quality of MALDI–TOF spectra. Therefore six selected matrices (2,5-dihydroxybenzoic acid, 2,4,6-trihydroxyacetophenone, -cyano-4-hydroxycinnamic acid, 2-(4-hydroxyphenylazo)benzoic acid, 3-aminoquinoline and sinapinic acid) were tested. The optimization of experimental conditions was carried out for two model carbohydrates that are important in food chemistry—inulin and starch. The experiments were performed in both positive linear and reflectron mode. The signals of the standard samples in reflectron mode were weak and repeatability of the measurements was lower than in linear mode. 2,4,6-Trihydroxyacetophenone for inulin and 2,5-dihydroxybenzoic acid for starch were found as the best matrices. Therefore, the real samples were analyzed with these two matrices in linear mode. The distribution of oligosaccharides from Jerusalem artichoke showed the degree of polymerization (DP) of the oligosaccharides in the range from 2 to 25. Red onion contained the saccharides with DP from 1 to 14. Glucose syrup from potatoes had DP from 2 to 48. MALDI–TOF–MS was found more sensitive for detection of oligosaccharides than the chromatographic methods used for the some purpose.     

Comparison of pulsed amperometric detection and integrated voltammetric detection for inorganic sulfur compounds in liquid chromatography

A Variety of potential–time waveforms are useful in pulsed electrochemical detection (PED) when applied for the amperometric detection of numerous polar organic compounds following their separation by liquid chromatography (LC). Here, we compare the waveforms for pulsed amperometric detection (PAD) and integrated voltammetric detection (IVD) applied for detection of organosulfur compounds at Au electrodes in acidic media. In PAD waveforms, electrodes response is measured at a constant detection potentials. In IVD waveforms, electrodes current is integrated throughout a fast cyclic scan of the detection potential. As a consequence of this difference in detection strategy, the background signal for IVD is significantly smaller for PAD in the detection of organosulfur compounds whose response mechanisms require the concomitant formation of surface oxides on Au electrodes. Furthermore, in comparison to Pad, IVD has a larger sensitivity and a diminished system peak from 0₂ dissolved in the sample. Use of a preadsorption step increases detection sensitivity in both PAD and IVD. The limit of detection (S/N=3)for cysteine in LC-IVD is ca. 6 nM for a 50-μl injection (i.e., 300 fmol) using a detection waveform that includes a 1000-ms preadsorption period.     

Study of molar response of dextrans in electrochemical detection

In this work, a methodological approach is reported, aimed at assessing the electrochemical response of some model gluco-oligosaccharides (dextrans). Such strategy is based on the complementary use of both anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) and capillary zone electrophoresis coupled with UV detection (CZE-UV). Unlike HPAEC-PAD, CZE-UV required derivatization with a chromophoric dye (i.e., 8-aminonaphtalene-1,3,6-trisulphonic acid, ANTS) to enhance UV response and separation selectivity. From the comparison between chromophore response and PAD signal, the reliability of HPAEC-PAD for quantitative evaluation of dextran mixtures containing mainly oligomers with polymerization degree (DP) up to 18 could be proved, due to the fairly constant molar response. For higher DPs (up to 41), a maximum in the trend of the molar responses was observed followed by a steep decrease for DPs higher than about 30-35; indeed, an underestimation of weight-average molecular weight of dextran mixtures containing such oligomers was noticed.     

Flow injection analysis of doxycycline or chlortetracycline in pharmaceutical formulations with pulsed amperometric detection

A flow injection with pulsed amperometric detection for determination of doxycycline or chlortetracycline in pharmaceutical formulations is described. Doxycycline or chlortetracycline were studied at a gold rotating disk electrode with cyclic voltammetry as a function of pH of supporting electrolyte solution. The optimized PAD waveform parameters were obtained with a flow injection system. The optimized pulsed conditions of doxycycline were 1150 mV (versus Ag/AgCl reference electrode) detection potential (E_det) for 220 ms (150 ms delay time and 70 ms integration time), 1500 mV (versus Ag/AgCl reference electrode) oxidation potential (E_oxd) for 70 ms oxidation time (t_oxd) and 250 mV (versus Ag/AgCl reference electrode) reduction potentail (E_red) for 400 ms reactivation time (t_red). The optimized pulsed conditions of chlortetracycline were 1050 mV (versus Ag/AgCl reference electrode) detection potential (E_det) for 300 ms (200 ms delay time and 100 ms integration time), 1300 mV (versus Ag/AgCl reference electrode) oxidation potential (E_oxd) for 70 ms oxidation time (t_oxd) and 250 mV (versus Ag/AgCl reference electrode) reduction potentail (E_red) for 400 ms reactivation time (t_red). The optimized PAD waveform was applied to the determination of doxycycline hydrochloride and chlortetracycline hydrochloride standard solution and in pharmaceutical formulations. The linear dynamic ranges of doxycycline hydrochloride and chlortetracycline hydrochloride were 1 μM–0.1 mM. The sensitivity of this method was found to be 23 μA/mM for doxycycline hydrochloride and 33.76 μA/mM for chlortetracycline hydrochloride. The detection limit for both compounds is 1 μM. The doxycycline hydrochloride and chlortetracycline hydrochloride content in commercially available tablet dosage forms by the proposed method was comparable to those specified by the manufacturer.     

Sterilization of health care products by 5 MeV bremsstrahlung (X ray)

Radiation sensitivities of . pumilus and spores were examined to bremsstrahlung of 5 MeV EB and Cobalt -60 γ rays in order to confirm the effects of radiation and dose rate. Biological indicators (SPORTROL, NAmSA, USA) were irradiated with the X ray in the dose rate range of 4.7–47kGy/h. D-value of spores was 1.4–1.5 kGy, and that of was 1.1–1.3 kGy. The D-values of and have very small dose rate dependences to X ray, and the D-values are similar to those of γ ray. Dose distribution by X-ray and γ irradiation was measured for cartons containing 32 unit dialyzers. The D_max./D_min. of the X-ray irradiation (1.2) was smaller than that of γ ray (1.3).     

Pulsed voltammetric/amperometric detection of polycyclic aromatic sulfur heterocycles (PASHs) at the gold disc electrode for studies in petroleum asphalts

This work describes the voltammetric and amperometric behavior of a high number of PASHs (sulfides, thiophenes, benzothiophenes, dibenzothiophenes, indenothiophenes, naphtothiophenes, thienothiophenes, phenanthrothiophenes, and acenaphtothiophenes) at gold disc electrodes aiming at their identification and determination in petroleum asphalts. The adsorption/redox processes expected for sulfur compounds at gold electrodes could be observed in all the studied PASHs in DMSO and hydromethanolic medium. Differential pulse (DP) voltammetry in non-aqueous solutions (0.1 mol L⁻¹ NaClO₄ in DMSO) was approached for determining non-volatile PASHs in asphalts submitted to different aging processes. It was found herein that the DP voltammetric monitoring of PASH oxidation at + 0.7 V (vs. Ag/AgCl/LiCl 3 mol L⁻¹) for virgin/aged asphalts can be used for the comparative study of asphalts based on the consumption of PASHs. Additionally, pulsed amperometric detection (PAD) in hydroalcoholic solution (10 mmol L⁻¹ acetate buffer in 65% methanol) coupled with a chromatographic separation was approached for determining volatile PASHs in asphalts submitted to thermal decomposition processes. A detection cycle of 2 s involving oxidative (0.4 s at + 0.4 V) and reductive (1.2 s at − 1.0 V) cleaning pulses after a detection pulse of − 0.8 V (0.4 s) applied successively to the gold electrode (vs. Pd/PdO) was found to be optimal for regenerating the gold surface during successive chromatographic runs of PASHs. Thus, reversed-phase liquid chromatography (LC)–coupled PAD was found useful to separate a complex mixture of PASHs. The optimized PAD and LC separation was further applied to investigate the presence of electroactive PASHs as volatile compounds in asphalt fumes generated at 260 °C.

     

Detection of lipopolysaccharide binding peptides by the use of a lipopolysaccharide-coated piezoelectric crystal biosensor

A method has been developed to monitor the interaction between a lipopolysaccharide (LPS) and LPS-binding peptides using a piezoelectric quartz crystal (PQC). Different pH conditions were evaluated to coat LPS onto AT-cut crystals that had been sputtered with gold and carboxylated with a 4,4-dithiodi(n-butyric acid). The optimal pH for LPS coating onto the crystal was 4–5. Synthetic peptides that represent different regions of human bactericidal/permeability-increasing protein, BPI (BPI 85–99, BPI 90–101, BPI 157–167) and polymyxin B (PmB) as well as negative control peptide (HBsAg 139–147) were utilized to compare their binding ability to this LPS-coated PQC sensor. The results showed that PmB gave the greatest decrease to the resonant frequency indicating greatest binding ability. BPI 85–299, considered the main part of the LPS binding domain of BPI, was the next greatest, while BPI 157–167 and HBsAg 139–147 showed little response. In addition, BPI 90–101 and PmB-mimicking peptide showed intermediate LPS-binding ability, which was less than that of BPI 85–99, but was higher than that of BPI 157–167. These results suggest the PQC biosensor is potentially useful for the detection and comparison of the LPS-binding ability of different peptides by using an LPS-coated piezoelectric crystal.     

Simultaneous determination of total arsenic and total selenium in Chinese medicinal herbs by hydride generation atomic fluorescence spectrometry in tartaric acid medium

By HG-AFS, a new method was proposed for simultaneous determination of total arsenic and total selenium existed in the Chinese medicinal herbs in tartaric acid medium. The effects of analytical conditions and coexisting ions on the fluorescence signal intensity of analytes were investigated. The proposed method was provided with linear response ranges above 22 μg l⁻¹ for As and 44 μg l⁻¹ for Se, and the detection limits of 0.13 and 0.12 μg l⁻¹ were obtained for As and Se respectively. The recoveries of 93.8–96.1% for As and 95.3–99.1% for Se, and the precision of 1.2–3.8% and 2.4–5.3% (R.S.D., n = 8) respectively, were obtained via simultaneous determined four samples of Chinese medicinal herbs and three certified botanic reference materials successfully. The proposed method has the advantages of simple operation, high sensitivity and high efficiency.     

Pulsed amperometric detection of DNA with an ssDNA/polypyrrole-modified electrode

Pulsed amperometric detection (PAD) of target DNA with platinum electrodes modified by single-stranded DNA (ssDNA) entrapped within polypyrrole (ssDNA/Ppy) is reported for the first time. Single-stranded DNA 20-mers complementary to the target DNA were used to construct the DNA biosensors. Polymerase chain reaction (PCR) amplified bovine leukaemia virus (BLV) provirus DNA was used as target DNA. Electrochemical impedance spectroscopic (EIS) investigation of ssDNA/Ppy before and after incubation in target DNA-containing sample revealed significant changes in terms of an imaginary (Z) vs. a real (Z) component. The PAD results were in good agreement with EIS investigations. The PAD method was selected, because it does not require such sophisticated equipment as it is used to perform EIS and the results obtained can be more easily estimated. Optimum conditions for performing PAD and evaluating an analytical signal were elaborated. No label-binding step was necessary for detection of target DNA in PCR-amplified amplicons and detection time was reduced by as much as 30–35 min. The changes of PAD signals were at least 6–7 times higher if ssDNA/Ppy-modified electrodes instead of blank Ppy-modified electrodes were incubated in the target DNA solutions. If ssDNA/Ppy modified electrodes were incubated in non-complementary (control) DNA solution changes in PAD signals were smaller than those detected after incubation in complementary (target) DNA-containing solution by a factor of at least 6–8.     

A consideration of electrode polishing prior to application of pulsed amperometric detection

An examination was made of the effect of electrode polishing on the direct pulsed amperometric detection (PAD) and indirect PAD response to penicillin G. The polishing procedure produced a temporary loss of sensitivity for both types of PAD, which over time relaxed back to higher levels. A temporary increase in the electrode kinetics can be observed as well, particularly for a PAD waveform in the crossover region between direct and indirect PAD. In extreme cases, the penicillin G response can undergo a complete polarity reversal. By observing post-polish equilibration times, it was recommended that the direct and indirect PAD user observe 3 and 5 h delay times, respectively, to insure stable electrode response following an electrode polish.     

Spectroscopic and theoretical investigations on effective and selective complexation between porphyrins and fullerenes

We have tailored some interesting mono- and diporphyrins, viz., 5, 10, 15, 20-tetrakis(octadecyloxyphenyl)-21H,23H-porphyrin (TP), 5, 15-bis(3, 5-dioctylphenyl)-2, 8, 12, 18-tetramethyl-3, 7, 13, 17-tetradodecyl-21H,23H-porphyrin (AP) and 1, 3-bis(10′,20′-diundecyl-21′H,23′H-porphyrin-5′-yl)benzene (DP) as host molecules to study their complexation behavior with C₆₀ and C₇₀. Fluorescence spectroscopic measurements showed that emission of TP, AP and DP in toluene was quenched in the presence of C₆₀ or C₇₀. Large binding constants (K) in the magnitude of 1.5 × 10⁴ dm³ mol⁻¹ have been obtained for the 1:1 complexes of C₇₀ with TP, AP and DP. However, the C₆₀ complexes have exhibited 8.5 times smaller K compared to C₇₀ complexes. Ab initio theoretical calculations give a good support in favor of strong complexation between C₇₀ and porphyrins.     

Determination of diethylhexyl phtalate in water by solid phase microextraction coupled to high performance liquid chromatography

Difficulties detected in the determination of the diethylhexylphthalate (DEHP) at trace levels by gas chromatography–mass spectrometry (GC–MS) using SPME, due to its ubiquitous distribution in the environment has been overcome and a new method for the determination of DEHP in drinking water has been proposed. The method is based on solid phase microextraction (SPME) coupled to high-performance liquid chromatography (HPLC). Detection was carried out spectrophotometrically. Calibration graph was linear in the range 10–110 μg/L with a regression coefficient of r² = 0.998 and a detection limit of 0.6 μg/L. The relative standard deviation was 5 and 2% (n = 4) for chromatographic areas and retention times, respectively. The usefulness of the SPME–HPLC technique was confirmed.     

Effect of laser modified surface microtopochemistry on endothelial cell growth

The introduction of microelectronics technology in the area of biological sciences has brought forth previously unforeseeable applications such as DNA or protein biochips, miniaturized, multiparametric biosensors for high performance multianalyte assays, DNA sequencing, biocomputers, and substrates for controlled cell growth (i.e. tissue engineering). We developed and investigated a new method using “cold” excimer laser beam technology combined with microlithographical techniques to create surfaces with well defined 3D microdomains in order to delineate critical microscopic surface features governing cell–material interactions. Microfabricated surfaces with microgrooves 30–3 μm deep, 10–1 μm wide spaced 30 μm apart were obtained with micron resolution, by “microsculpturing” polymer model surfaces using a computer controlled laser KrF excimer beam coupled with a microlithographic projection technique. The laser beam after exiting a mask was focused onto the polymer target surface via an optical setup allowing for a 10-fold reduction of the mask pattern. Various 3D micropatterned features were obtained at the micron level. Reproducible submicron features could also be obtained using this method. Subsequently, model human umbilical endothelial cells (HUVEC) were cultured on the laser microfabricated surfaces in order to study the effects of specific microscopic surface features on cell deposition and orientation. Cell deposition patterns were found to be microstructure dependant, and showed cell orientation dependency for features in the cell range dimension, a behaviour significantly different from that of a previously studied cell model (osteoprogenitor cell). This model may be a promising in so far as it is very rapid (a time frame less than a second per square centimeter of micropatterned surface) and provides further insights into the effects of surface microtopography on cell response with possible applications in the field of biosensors, biomedical and/or pharmaceutical engineering sciences.     

Aliphatic polyamine oxidation response variability and stability at boron-doped diamond thin-film electrodes as studied by flow-injection analysis

Previously it was shown that four different aliphatic polyamines can be quantitatively electrooxidized at boron-doped diamond thin film electrodes without derivatization or the use of pulsed voltammetric waveforms [Anal. Chem. 71 (1999) 1188; Anal. Chem. 69 (1997) 4041]. The flow injection analysis (FIA-EC) investigation (amperometric detection mode) of cadaverine (CAD), putrescine (PUT), spermine (SPM) and spermidine (SPMD), reported previously [Anal. Chem. 71 (1999) 1188], are updated herein with particular emphasis on the electrode response variability and stability. Most of the measurements were made with a film deposited from a 0.50% methane-to-hydrogen (C/H) volumetric ratio. In general, films deposited with C/H ratios near this value tend to possess the requisite physicochemical properties to support anodic oxygen transfer reactions. The electrode performance was evaluated in terms of the linear dynamic range, limit of quantitation, response variability and response stability. A linear dynamic range from 1.0 μM to 1.0 mM and a limit of quantitation of 1.0 μM or 20 pmol injected (S/N≥3) were found for CAD, PUT, and SPMD. For SPM, a linear dynamic range from 0.32 μM to 1.0 mM and a limit of quantitation of 0.32 μM or 6.4 pmol were observed. The response variability, as low as 2–4%, was observed which is vastly improved over previous results. The improvement was achieved by introducing a 3–6 min delay period between injections. The long-term response stability was good with no evidence for any progressive response attenuation or complete fouling by the reaction product, even though a solid deposit was observed to accumulate on the electrode surface with extended use. The deposit appears to partially reduce the active electrochemical area for polyamine oxidation and to decrease the overpotential for water discharge. Preliminary chromatographic results demonstrated the possibility of separating and detecting the polyamines by a simple reverse-phase scheme at constant applied potential.     

A biosensor based on graphite epoxy composite electrode for aspartame and ethanol detection

A gelatin membrane with carboxyl esterase and alcohol oxidase was subsequently integrated onto the surface of a graphite epoxy composite electrode (GECE). The developed biosensors showed linearity in the range of 2.5–400 μM for aspartame and 2.5–25 μM for ethanol with response times of 170 and 70 s for each analyte, respectively. The resulting bienzyme biosensor was used for aspartame detection in diet coke samples and ethanol detection in beer and wine samples. From the obtained results, it can be concluded that the developed biosensor is a selective, practical and economic tool for aspartame and ethanol detection in real samples.     

Studies on phenol permeation through supported liquid membranes containing functionalized polyorganosiloxanes

In this study, the functionalized, linear, hydrophobic fluid organosiloxane polymers, namely, methylhydrosiloxane–dimethylsiloxane copolymers supported on a polypropylene microporous flat sheet membrane (Celgard 2502 and 2402) have been tested as supported liquid membranes (SLMs) for phenol recovery from aqueous phases into a 0.1 M NaOH phase. The functionalized polymers include, Me₃SiO[MeSi(OR)O]_x[Me₂SiO]_ySiMe₃ (containing x = 15–18, 25–35 and 50–55 mol% of R, where R is –(CH₂)_nNMe₂ (n = 3 or 4 or 6) or –(CH₂)₂OEt pendent organofunctional groups. The functionalities, R, tested were derived from the commercially available 3-dimethylamino-1-propanol and 2-ethoxyethanol as well as newly synthesized 4-dimethylamino-1-butanol and 6-dimethylamino-1-hexanol which have been made for the purpose of this study.

The study showed that phenol permeation expressed as permeate flux through the membranes increases with the larger number of carbon spacers in the alkyl chain of the aminoalcohol pendent, larger porosity of the polypropylene support films, higher mol% of the methylhydrosiloxane portion functionalized and faster flow rates of both the feed and the receiving phases. Phenol permeation was enhanced significantly when the mol% of the methylhydrosiloxane portion was 50–55 or 25–35 with 6-dimethylamino-1-hexanol functionality supported on Celgard 2502.     

Study of near resonant energy transfer from laser excited CO2 to SO2

Collisional energy transfer from CO₂ to SO₂ was studied subsequent to pumping of CO₂ (ν₃) by a Q-switched laser. The measurements were made in the temperature range 300–800 K and in the pressure range 1–30 Torr. The fluorescence from the ν₃ level of CO₂ was monitored with the help of a Ge:Au detector at 77 K with an estimated response time of ≈2 μs. The probability of the energy transfer was found to be increasing with increasing temperature. The probable kinetic models for the V---V relaxation pathways were discussed and the experimentally measured energy transfer rate is related to the cross-over transfer processes. Theoretical calculations using both a simple SSH-breathing sphere model and the Sharma-Brau theory were carried out to evaluate the probabilities of the involved cross-over energy transfer processes and the results were compared with the experimental rates.