Jim O. Olsson

Soxhlet extraction of acrylamide from potato chips

The problem of complete extraction of acrylamide from potato chips was investigated. A method was developed based on the Soxhlet extraction technique. A defatted sample was extracted continuously with methanol, for 10 days, in a Soxhlet extractor. After about 7 days, a constant concentration of acrylamide was reached. This indicates that all the acrylamide that could be removed from the sample had been extracted. Acrylamide was identified in the extract using GC-MS and scan mode. Total concentration was 14500 microg kg(-1) using GC-FID and standard additions. Complementary determinations, using an external standard (GC-FID and GC-MS) and an internal standard (GC-FID), showed results within +/- 5%. A previously published study, using a static extraction method and GC-MS and LC-MS-MS, showed concentrations of 2287 and 1993 microg kg(-1), respectively. The results are discussed in relation to a recent model and analogous experiments. The extracted amount of acrylamide is affected by several parameters: solvent properties, solvent volume, extraction time, temperature, particle size, and the microstructure of the sample.

OXIDATION OF RAPESEED OIL, RAPESEED METHYL ESTER (RME) AND DIESEL FUEL STUDIED WITH GC/MS.

Abstract Small samples (5 μl) of rapeseed oil, rapeseed oil methyl ester (RME) and a superior quality diesel oil according to the Swedish environmentally class 1 (SEC1) were oxidised at 550°C in a reactor. The compounds produced were analysed using a gas chromatographic (GC) method: direct gas injection with GC/MS. Rapeseed oil and RME produced factor 10 more 1-alkenes, dienes, and benzene in comparison with diesel SEC L Rapeseed oil produced high amounts of acrolein and other aldehydes. Oxidation of RME produced significant amounts of methyl acrylate (2-propenoic acid, methyl ester). The different oils produced a varying number of compounds during the oxidation. The rapeseed oil produced 72 peaks with a peak-area above 100 000-area counts and RME produced 61 peaks, in comparison the SEC 1 produced only 27 peaks.

Apparatus with nanosecond field transition times for field reversal studies of surface processes at high temperatures

A new type of field‐reversal apparatus is described. It is intended for desorption and surface reaction studies in systems with surface ionization. The problems of mechanically modulating the molecular beam are circumvented by instead reversing the electric field outside the surface and thus perturbing the steady‐state desorption conditions. The short field reversal time of ⩽ 10 ns with a 90 V voltage step is reached by using VMOS transistors with optoisolated driving circuits. The ions from the ionizing surface are converted to electrons on a Cu–Be dynode. The electrons give photons in a scintillator, and the photons are detected by a photomultiplier outside the vacuum wall. The apparatus dependent signal rise time is around 40 ns, which means that surface processes with very short characteristic time constants can be measurable.

Slow pyrolysis of spruce and pine samples studied with GC/MS and GC/FTIR/FID

Abstract Small samples (10 – 150 mg) from eight pine and spruce species were pyrolysed at 550 °C. The samples were taken from Scotch pine, Austrian pine, Lodgepole pine, Ponderosa pine, Norway spruce, White spruce, Black spruce and Sitka spruce. The compounds produced from the pyrolysis were analysed with several gas chromatographic (GC) methods: direct injection with GC/MS or GC/FTER/FID and pre-concentration with GC/MS and GC/FID. The product distributions of organic compounds from the different conifers show common features. Large amounts of oxygenated organic compounds were formed: aldehydes, acids, ketones and methoxylated phenols. The pine species produced less methoxylated phenols than the spruce species.

Molecular beam surface ionization detection: II. Field reversal and surface ionization study of Na on Re with adsorbed oxygen

Abstract The desorption and surface ionization of Na on a polycrystalline Re surface with various amounts of adsorbed oxygen have been studied by field reversal, surface ionization and thermoelectronic emission methods. In this work the unique properties of the field reversal method are taken advantage of, i.e. that both neutral and ionic desorption rate constants can be determined simultaneously. Absolute ionization coefficients have been measured by field reversal and have been compared with values found by the “oxygen coverage” method and by static surface ionization. The application to beam flux density determinations is discussed. The simultaneous variation of the neutral and ionic desorption rate constants during oxygen adsorption and the temperature dependence of them have been studied. The Re surface in 2 × 10−8 Torr of oxygen and at 1300–1500 K is shown to be very stable and to behave differently than in studies at higher temperatures. The very rapid change in both desorption rate constants at an effective work function Φe = 5.35 V is here correlated with the results of LEED experiments (Gorodetskii and Knysh) and is proposed to indicate a change from a stable Re oxide surface at low Φe (and oxygen coverage) to a different surface structure at higher Φe. Desorption energies have been determined at various values of Φe. The neutral desorption energy at low oxygen pressure is 2.70 ± 0.06 eV, which agress well with earlier, here corrected modulated beam results. The energy (Schottky) cycle for surface ionization is shown to be closed at low Φe, which has been difficult to show with other methods in any other case.

Simple surface ionization detector with field reversal for absolute ionization coefficient and ionic and neutral desorption measurements

Recent absolute reactive scattering experiments have demonstrated the need for and usefulness of absolute flux measuring molecular beam detectors. A field reversal detector of the type described here can conveniently and accurately (<±3%) measure the absolute flux of molecular beams of easily ionizable substances, without external calibrations or surface condition or surface temperature changes. The detector is mechanically very similar to the common surface ionization detector and uses uncomplicated electronics. With such a detector the neutral and ionic desorption rates may also be accurately determined separately. Thus the values of the true desorption parameters may be measured; such values have usually not been produced by previous methods for desorption rate measurements.

Combustion of gasolines in premixed laminar flames European certified and California phase 2 reformulated gasoline.

Two gasoline qualities, European unleaded certified gasoline (EUCG) and California phase 2 reformulated gasoline (P2 RFG), were analysed. EUCG contained about twice the amount of alkyl benzenes compared to P2 RFG and a large amount of cyclohexane. As a balance, P2 RFG contained higher amounts of isooctane and MTBE. The gasolines were burned in a premixed laminar flame burner at 1 atm and at about stoichiometric fuel/air ratio. The species profiles were measured using on-line GC/MS. About 40 compounds were be detected in the gasoline flames. The EUCG resulted in formation of more reactive and toxic compounds. The combustion profiles of the fuel components showed a similar slope, which suggests that the fuel components burn quite independently of each other. Ethene and propene were the dominating species produced from the two gasolines. Commonly, substantial amounts of higher alkenes were found. Combustion of P2 RFG produced higher amounts of isobutene, propene, propyne, propadiene and methanol compared to combustion of EUCG. The high amount of isobutene is reasonably a result of high concentration of isooctane and MTBE in the fuel. The high amount of methanol formed is probably due to the MTBE present in the gasoline. EUCG produced significantly higher amounts of 1,3-butadiene, which quite likely is formed from the cyclohexane in the fuel. The benzene profiles from both gasolines shows an almost constant level up to 800 microm from the burner surface; this is probably due to formation of benzene from alkyl benzenes.

Molecular beam surface ionization detection: I. Absolute ionization coefficients and work function of “low work function” Pt(8%W) surfaces

Abstract Absolute ionization coefficients β have been measured for K on a “low work function” PtW surface by the field reversal method. The modified Langmuir-Saha equation has been fitted by a least-squares procedure to the static surface ionization values as a function of temperature, and ionization coefficients have been computed from the best fit parameter values. The agreement between the two methods is satisfactory at low temperatures, within 9% at β = 0.7–0.8, with the largest error probably lying in the coefficients from static ionization. By a comparison with other methods used for determinations of β

Desorption of potassium from carbon film surfaces

Abstract The desorption of potassium from carbon-covered Pt-8%W was studied in the temperature interval 950 – 1100 K with potassium fluxes of the order of 1017 atoms m−2s−1 and lower generated by a steady state molecular beam. The ionic (k+) and atomic (k0) rate constants for desorption were measured simultaneously as a function of temperature with the field reversal method. The Arrhenius desorption rate parameters calculated were very stable and reproducible but varied somewhat with the surface state. The largest values found were l+ = 2.89 eV, l0 = 3.10 Ev. A+ = 1 × 1018s−1 and A0 = 5 × 1018s−1 at a surface coverage of 10−6 monolayer. The ratio k+/k0 indicates as effective work function of 4.49 V comparable with pure graphite. On metals the factors A+ and A0 are almost always 1018−10113s−1. The carbon (graphite) layers increase the pre-exponential factors A and the rate constant about 103–104 times compared with metal surfaces, which means that the coverage is correspondingly lower on carbon. No acceptable theory to explain these large A values is yet available.

Slow pyrolysis of willow (Salix) studied with GC/MS and GC/FTIR/FID

Abstract Small samples (15–150 mg) of wood and bark from basket willow ( Salix viminalis ) clone Jorr were pyrolysed at 550°C. Samples from pure wood of European White (Silver) Birch ( Betula pendula (alba) ) and Norway Spruce ( Picea abies ) were used as references. The compounds produced during pyrolysis were analysed using gas chromatographic (GC) methods: direct injection with GC/FTIR/FID, direct injection with GC/MS, and pre-concentration with GC/MS. The samples from salix, birch and spruce all produced a range of low molecular weight compounds: aliphatic acids, esters, aldehydes, and ketones as well as furans. Commonly, these samples also formed aromatic compounds: phenol, methyl-phenols, and the guiacol (2-Methoxyphenol) series of compounds. Salix and birch both produced the syringol (2,6-Dimethoxyphenol) series of compounds. Syringol derivatives were not detected from the pyrolysis of spruce.