Application of the photoionization detector for the determination of ethanol in aqueous solutions and human breath

A determination of ethanol is described, which is based on a purging system in conjunction with a photoionization detector. With that system a fast and reliable determination of ethanol in aqueous solutions is possible. The system has been used for the analysis of wine. The 3-detection limit has been 0.005% ethanol, the relative standard deviation 4.8 to 6.0% and the time constant of the entire analytical system 20 s. The photoionization detector has been also applied to the analysis of artificial and genuine human breath. A comparison with gas-chromatography and non-dispersive IR-detection has been proven the reliability of results.     

Basic experimental studies on the operation of photoionization detectors

Commercially available and self-made photoionization detectors have been studied in a simple flow manifold without chromatographic column. The self-made detector allowed the independent variation of the detector volume, the electrode surface area and a selective irradiation of the anodes and cathodes. The photoionization of ethanol and acetone has been measured in hydrogen as carrier gas. All experimental results were consistent with a model based upon a photoionization proceeding in the adsorption layer of the electrodes as the main signal generating process. It has been shown that the photoionization of molecules in the gas phase plays only a marginal role. Received: 11 November 1997 / Revised: 12 December 1997 / Accepted: 10 January 1998     

Determination of dimethylselenide and dimethyldiselenide by gas chromatography-photoionization detection

A simple method for the determination of volatile selenium compounds employing a gas chromatograph equipped with a photoionization detector is described. The method involves the direct injection of dimethylselenide (DMS) or dimethyldiselenide (DMDS) into the gas chromatograph; no derivatization of the sample was required. The photoionization detector was capable of detecting 60 pg (0.55 pmol) of DMS and 150pg (0.80pmol) DMDS. Sensitivity was 10-50 times greater with DMS and 4-20 times greater with DMDS when the photoionization detector was employed than when the flame ionization detector was employed.     

Universal and discriminative detection using a miniaturized pulsed discharge detector in comprehensive two-dimensional GC

A miniaturized pulsed discharge detector (Mini-PDD) has been successfully demonstrated for comprehensive 2-D GC (GC x GC) analysis of pyrolysis gasoline and the pyrolysis GC x GC analysis of a polyethylene copolymer. The detector cell volume of the Mini-PDD is reduced to 25% of the Valco plug-in PDD D-3. An n-C11 peak width at base is 96 ms for the Mini-PDD, about 23% larger than a peak width of 78 ms detected by a flame ionization detector (FID). The Mini-PDD has sufficient response time for most GC x GC applications. When Mini-PDD is operated in helium photoionization mode (Mini He-PDD), it is a universal detector for both inorganic and organic compounds. This is especially useful when detection of water is needed in GC x GC applications. When krypton is doped in the helium discharge gas (Mini Kr-PDD), it can suppress signals of compounds having higher ionization potentials and enhance relative signal intensities of aromatic compounds. The determination of aliphatic to aromatic hydrocarbon ratios is essential to the operation of petroleum crackers. Comparison of the signal from two modes of the Mini-PDD is a simple and fast way to verify the location of aromatics in comprehensive 2-D gas chromatograms.     

Determination of sugars and alcohols in apple juice and cider by high performance liquid chromatography

Summary The application of a high-performance liquid chromatographic produre to the separation and determination of major sugars, sorbitol, glycerol and ethanol in apples, apple juice and cider is described. The HPLC system consisted of a cation-exchange resin column in calcium form, a solvent system of an aqueous solution with calcium EDTA and a refractive index detector. The analysis was completed after 16 minutes. A recovery greater than 91% was observed for all compounds with most recoveries nearing 100%. The coefficients of variation ranged from 2% to 6%.     

Individual and simultaneous enzymatic determination of ethanol and acetaldehyde in wines by flow injection analysis

The individual and simultaneous enzymatic determination of ethanol and acetaldehyde in wine by flow injection analysis is described. Individual determinations of 0.002–0.016% (v/v) ethanol or 1.0–8.0 μg ml^?1 acetaldehyde with r.s.d. 0.7% and 0.5%, respectively, are done with a single-beam spectrophotometer, based on the use of alcohol dehydrogenase and aldehyde dehydrogenase. A diode-array detector and dual reagent injections are used for the simultaneous determination of the two compounds. The errors are 〈 3.5% and 〈 2.0% for ethanol and acetaldehyde, respectively, when the method is applied to wine samples.     

Enzymatic microreactors for the determination of ethanol by an automatic sequential injection analysis system

A sequential injection analysis system with two enzymatic microreactors for the determination of ethanol has been designed. Alcohol oxidase and horseradish peroxidase were separately immobilized on glass aminopropyl beads, and packed in 0.91-mL volume microreactors, working in line with the sequential injection analysis system. A stop flow of 120 s was selected for a linear ethanol range of 0.005-0.04 g/L +/- 0.6% relative standard deviation with a throughput of seven analyses per hour. The system was applied to measure ethanol concentrations in samples of distilled and nondistilled alcoholic beverages, and of alcoholic fermentation with good performance and no significant difference compared with other analytical procedures (gas chromatography and high-performance liquid chromatography).     

Rapid analysis of hydrocarbons and inert gases by a multidimensional gas chromatograph

A combination of a pressure switching system with multiple columns and photoionization detectors makes possible rapid analysis of a mixture of inorganic gases and hydrocarbons. Hydrocarbons are separated by a narrow bore capillary column. An alumina PLOT column is used for the separation of lower molecular weight hydrocarbons, especially C4 isomers, while a combination of a micro-packed column with Porapak N and a PLOT capillary column with Molecular Sieve 5A is used for the fast separation of inorganic gases. A photoionization detector is a powerful additional tool for organic gas analysis.     

Determining the procedure for routine residue monitoring of sulfamethazine in edible animal tissues.

A simplified method to determine/identify residual sulfamethazine (SMZ) in edible tissues from cattle, pigs, chickens and sheep by a high-performance liquid chromatography (HPLC) with a photo-diode array detector is presented. The sample preparation was performed by homogenizing with 30% (v/v) ethanol in water followed by an Ultrafree-MC/PL as a centrifugal ultra-filtration unit. For determination/identification of SMZ, a reversed-phase C(4) column and a mobile phase of 15% (v/v) ethanol in water with a photo-diode array detector was used. Average recoveries from spiked SMZ (0.1-1.0 mg kg(-1)) were >or=80% with coefficients of variation between 1.3 and 4.3%. The limits of quantitation were calculated to be 0.057-0.060 mg kg(-1). The total time and solvent required for the analysis of one sample were <40 min and <2 mL of ethanol, respectively.     

Operating the pulsed discharged detector in both the electron-capture and photoionization modes within the same GC analysis

Summary Since the electron-capture detector (ECD) is highly selective, it is imperative to use a more universal ionization detector in conjunction with the ECD in order to detect non-capturing or weakly capturing compounds. Also in an EC study of weakly or moderately strong electron-capturing compounds, it is necessary to identify the EC peak of the compound by identifying the major component with an ionization detector. In this paper we have shown that the pulsed discharge detector can be interchanged between the EC and the helium ionization modes within 4–6 s. The application of this procedure has been illustrated with a mixture of alkane/alkene chlorocompounds. The interchange between EC and argon photoionization modes has also been investigated. The change from EC to argon photoionization also occurs in 4–6 s but the reverse process requires 9 s.     

脉冲放电氦光离子化检测器分析有机化合物的性能研究

研究本实验室组装的脉冲放电氦光离子化检测系统上PDPID的性能、各种操作参数对信号的影响、操作最佳化及信号线性。用该系统分析了汽油、酮醇混合物和痕量挥发性有机化合物等样品,它们的色谱图可以同FID相比。     

Sensitive assay of methadone in plasma by using capillary gas chromatography with photoionization detection

A new gas chromatographic assay for methadone, utilizing a fused-silica capillary column, is presented. Extreme sensitivity was reached, compared to nitrogen-phosphorus and mass spectrometry detection, by employing a photoionization detector. Plasma concentrations of methadone as low as 1 ng/ml can easily be detected and, by further optimization, 0.1 ng/ml was reached. The minimum detectable amount of methadone reaching the detector was 70 fg. The results indicate that the photoionization detector has potential as a tool in drug monitoring.     

Automatic flow procedure for the determination of ethanol in wine exploiting multicommutation and enzymatic reaction with detection by chemiluminescence

An automatic procedure for the determination of ethanol in wines using a flow system based on multicommutation and enzymatic reaction is described. Alcohol oxidase was immobilized on aminopropyl glass beads and packed in an acrylic column. The peroxide due to enzymatic reaction with ethanol reacted with luminol and generated the chemiluminescence radiation that was monitored by using a laboratory-made detector based on photodiodes. The system manifold comprised a set of 3-way solenoid valves controlled by a microcomputer furnished with electronic interfaces, which ran on software written in Quick BASIC 4.5 to provide facilities to perform on-line sample dilution, reagent addition, and data acquisition. After system parameters optimization, ethanol samples were processed without prior pretreatment. The following suitable features were achieved: linear response ranging from 2.5 to 25% (v/v) ethanol, relative standard deviation of 1.8% (n = 10), detection limit of 0.3% (v/v) ethanol, sampling rate of 23 determinations per hour, and low reagent consumption of 0.23 mg luminol and 7 mg hexacyanoferrate (III) per determination. When the results were compared with those obtained using the AOAC Official Method, no significant difference at the 90% confidence level was observed.     

Carbon-carbon bond cleavage in the photoionization of ethanol and 1-propanol clusters

Tunable VUV laser was used to initiate the ion-molecule reactions in the clusters of ethanol and 1-propanol by photoionization in the region between 10.49 to 10.08 eV. Ionic products were detected by the time-of-flight mass spectrometer. In addition to the protonated clusters from proton transfer reactions, the products corresponding to beta carbon-carbon bond cleavage were found to be one of the major products for small sizes of clusters. A comparison with photoionization of methanol clusters and the results of ab initio calculation has been made.     

Fluorometric determination of ethanol in liquor samples by flow-injection analysis using an immobilized enzyme-reactor column with packing prepared by coupling alcohol oxidase and peroxidase onto chitosan beads

A flow-injection system was developed for the determination of ethanol with an immobilized enzyme-reactor column. This system, which consisted of hand-made reactor columns packed with alcohol oxidase and horseradish peroxidase immobilized onto chitosan beads, and a fluorometric detector, was applied to the determination of ethanol in liquor samples. Under the recommended conditions, the ethanol, which was present in the pretreated samples, was converted to hydrogen peroxide when it was passed through the immobilized alcohol oxidase (AOD) column with 0.1 mol/dm3 phosphate buffer (pH 7.0). A sample can be analyzed with this system in <10 min. The calibration curve for ethanol was linear from 2.0 to 0.1 mg/dm3. The determination limit, which was defined by the difference between the sample peak and blank peak, was estimated to be 50 microg/dm3 for ethanol. Interferences from some substances present in actual liquor samples decreased the analytical response and activity of the immobilized AOD-reactor column, but they were removed by dilution and pretreatment with an octyldecylsilane cartridge.     

Simultaneous determination of benzene and toluene in the blood using head-space gas chromatography

A head-space method for the simultaneous determination of benzene and toluene in blood using a gas chromatograph equipped with a photoionization detector was developed. Internal standards for benzene and toluene were fluorobenzene and o-xylene, respectively, and the detection limit was 5 nmol/l for both solvents. This method is sensitive enough for needs of biological monitoring of benzene and toluene in exposed workers. With automation it offers a possibility for routine measurements. An application of the method in monitoring exposed workers in the industry is presented.     

Trace level determination of low-molecular-weight alcohols in aqueous samples based on alkyl nitrite formation and gas chromatography.

A simple and sensitive method for the determination of liquid methanol and ethanol at trace levels by an alkyl nitrite formation reaction has been established. Alcohol was allowed to react with nitrous acid, which was yielded from sulfuric acid and sodium nitrite in the solution, to form the corresponding alkyl nitrite in the hexane organic phase. Alkyl nitrites in hexane were analyzed by a gas chromatograph with an electron capture detector (GC-ECD). The detection limits, which were determined at a signal-to-noise ratio of 3, were 1.1 and 0.7 micrograms/L for methanol and ethanol, respectively, by 1 microL injection. The relative standard deviations for n = 8 were 4.0 and 3.3% for methanol and ethanol, respectively. The method was applied to determine the alcohol concentration in a rice paddy, pond water, tap water, and well water. Those aqueous samples were also spiked with standard alcohols; the average recoveries of spiked methanol and ethanol were 98 and 91% with relative standard deviations of 6.1 and 4.0%, respectively.     

Application of the photoionization detector for single determinations of hydride forming elements

The application of a photoionization detector in conjunction with a flow-through system is described for the determination of arsenic, antimony, selenium, tellurium, bismuth, tin, sulfide and ammonia. The analytical procedure is based upon a preliminary generation of the hydride compounds, their subsequent transfer to the gas phase and finally their detection in the photoionization detector. Linear calibration curves were obtained over three to four orders of magnitude with the following 3s-detection limits: 4 ng/ml As, 0.3 ng/ml Sb, 0.5 ng/ml Se, 3.0 ng/ml Te, 0.1 g/ml Bi, 0.5 g/ml Sn, 10.0 ng/ml S^2–, 0.5 g/ml NH₃.     

A new method for the high performance liquid chromatographic determination of TA-870, a dopamine prodrug (catechol ester compound)

A new method for the high performance liquid chromatographic (HPLC) determination of N-(N-acetyl-L-methionyl)-O,O-bis(ethoxycarbonyl)dopamine (TA-870), a dopamine prodrug, in biological fluid has been developed. In order to measure with an electrochemical detector (ECD), TA-870 was passed first through an immobilized carboxylesterase column to be converted to the electrochemically active deethoxycarbonylated TA-870 (DEC-TA-870). The properties of this carboxylesterase immobilized on Sepharose 4B were examined by this flow injection system. Hydrolysis of TA-870 with this immobilized carboxylesterase was a maximum at pH 7-8 and 50 degrees C, and the activity decreased in the presence of organic solvent such as acetonitrile. For the determination of TA-870 in biological fluids, an HPLC-immobilized enzyme-ECD system using a column-switching technique was developed. The blood was deproteinized with ethanol, and TA-870 in the ethanol extracts was adsorbed in Bond Elut C18. The dichloromethane eluate from Bond Elut C18 was injected into the HPLC system. The HPLC apparatus was composed of three pumps, two separation columns (LiChrosorb Si 60 and mu Bondasphere), a trap column (Bond Elut), an enzyme column, ECD and the column-switching system. The calibration curve for TA-870 in blood was linear in the range from 2 to 200 ng/mL. This new assay method might be useful also for the determination of other catechol ester compounds.     

Gas-Chromatographic Determination of Butanol and Butyl Acrylate in Aqueous Solutions with the Use of Headspace Analysis

A procedure has been developed for the determination of the concentration of butanol and butyl acrylate in aqueous solutions in the range of 0.5–20 MPC. The procedure is based on static headspace gas-chromatographic analysis on a column filled with the Chromaton N-AW-HMDS sorbent containing 15 wt % of polyethylene glycol adipate with detection by a flame-ionization detector.