Anders Colmsjö

Characterization of the cellulosic residues from lithium chloride/N,N-dimethylacetamide dissolution of softwood kraft pulp

Abstract In contrast to hardwood kraft pulps, softwood kraft pulps are not completely soluble in LiCl DMAc . Characterization of the undissolved fraction was made in order to obtain an understanding of the reason for its limited solubility. It was found that the residue consisted mainly of latewood fibers. In comparison with the initial pulp, the residue contains a higher relative amount of mannan, lignin and nitrogen. The nitrogen was assumed to originate from degraded proteins retained in the pulp. In contrast, the softwood pulp xylan seems to be easily dissolved and mainly amorphous structures were present in the residue. On the addition of LiCl DMAc , gel formation occurs, probably caused by the glucomannan content of the softwood kraft pulp. The gel formation also seems to be the main reason for the limited solubility of pulps with low lignin content.

Gas chromatographic analysis of high-molecular-mass polycyclic aromatic hydrocarbons: II. Polycyclic aromatic hydrocarbons with relative molecular masses exceeding 328

Abstract Three columns were used for the gas chromatographic analysis of polycyclic aromatic hydrocarbons (PAHs) with relative molecular masses (Mr) up to 450. Two of the columns were commercially available, coated with a 50% methyltrifluoropropyl-substituted polysiloxane a 5% diphenyl-substituted methylpolysiloxane. The third column was laboratory made, coated with a biphenyl-substituted silarylene-siloxane copolymer. All three columns were utilized for the analysis of high-Mr PAHs as regards both thermal stability of the stationary phases, i.e., low bleeding rate, and chromatographic efficiency. The column coated with a trifluoropropyl-substituted stationary phase showed, however, a low separation efficiency, possibly owing to low solute stationary phase compatibility. The biphenyl-substituted stationary phase, on the other hand, showed a very high separation efficiency, but the retention of the PAHs was significantly higher on this column compared with the other two, leading to the demand for higher oven temperatures. Different retention mechanisms were observed on these columns, as shown by differences in the retention indices of the PAHs measured in a system using PAHs as retention index markers. A comparatively faster elution of non-planar PAHs was observed on the columns coated with the trifluoropropyl-substituted stationary phase and the biphenyl-substituted stationary phase compared with the column coated with the 5% diphenyl-substituted polymer. The usefulness of the columns for separations of high-Mr PAHs is demonstrated by gas chromatograms of carbon black extracts and a coal tar extract standard reference material.

Sampling techniques and clean up procedures for some complex environmental samples with respect to PCDDs and PCDFs and other organic contaminants

Abstract In this paper we present a clean-up method that enables both the separation and subsequent analyses of PCDD, PCDF, PAH and PCB respectively. The method includes open column chromatography and a HPLC separating method. To illustrate the method different types of samples were analyzed; air sample from a car tunnel in central Stockholm sampled with glass fiber filters and polyurethane foam plugs, sludge samples from two sewage treatment works in Stockholm, settling particulate matter (SPM) sampled with a sediment trap, and soil sample from arable land fertilized with sewage sludge. These samples were also used as part of a study to determine any affect that transport may have on the chemical composition of samples collected in the field.

Backflush HPLC for the isolation of polycyclic aromatic compounds — A comparative study

SummarySemipreparative HPLC utilizing a polar bonded phase was applied to the isolation of polycyclic aromatic compounds (PAC) from complex samples using a backflush technique. Aminopropyl- and cyanopropyl-modified silica was tested. Aminopropyl-modified silica was found to be superior in achieving rapid, selective and non discriminating isolation of PAC. This was compared with the most commonly used isolation methods, dimethylsulfoxide (DMSO), dimethylformamide (DMF) and nitromethane liquid-liquid extractions, and silica and SephadexLH-20 open column chromatography. Strong discrimination of alkylated PAC and polycyclic aromatic nitrogen heterocyclics (PANH) was found for the liquid-liquid extractions and the LH-20 column chromatography. These comparisions were made using both standard compounds and a sample of used crankcase oil, indicating the necessity of using a real sample for evaluation of extraction methods. Recoveries of 42 PACs are reported.

Four different b-type cytochromes in the halophilic archaebacterium, Halobacterium halobium

The halophilic archaebacterium, Halobacterium halobium has been found to contain four different b-type cytochromes. The four components were recognized by their potentiometric characteristics in situ in their functional environment in the membrane of H. halobium. Oxidation-reduction midpoint potentials of these four b-type cytochromes were determined to be +261, +160, +30, and -153 mV, respectively. We also demonstrate that the pathway involved in the transport of reducing equivalents from succinate to oxygen proceeds through the b-type cytochromes with oxidation-reduction midpoint potentials of +261 and +161 mV. The cytochrome with oxidation-reduction midpoint potential of -153 mV was not substrate reducible by NADH but was chemically reducible by dithionite. Antimycin inhibits reduction of b-type cytochrome in the succinate pathway, but has no effect on b-type cytochrome reduction when reducing equivalents are provided by NADH. The carbon monoxide difference spectrum of H. halobium membranes shows at least one carbon monoxide-binding b-type cytochrome, indicating a terminal oxidase. A scheme for electron transport in H.halobium involving the b-type cytochromes and terminal oxidase is suggested.

Isolation and fingerprinting of some high-molecular-weight polynuclear aromatic compounds

The high-molecular-weight polynuclear aromatic hydrocarbon (PAC) fraction of a carbon black extract was isolated with a backflush technique, and applied to an amino-bonded stationary phase for HPLC. This fraction was further separated into 44 sub-fractions by means of reversed-phase HPLC, on an ODS column. Low-temperature fluorescence, utilizing the Shpolskii effect, was then applied to each fraction. By this method, quasilinear spectra were recorded from mostly peri- condensed PACs with molecular weights up to 400 daltons. Nine compounds with molecular weights exceeding 300 daltons were identified.

Group separation of PCDDs, PCDFs, PACs and aliphatic compounds on an amino bonded stationary phase for HPLC

SummaryA HPLC method for the clean up of PCDD and PCDF samples is presented. The method utilizes the possibility of separating compounds according to the number of double bonds by using an amino bonded stationary phase. Aliphatics as well as compounds with higher aromaticity than PCDD/PCDF are removed. In addition, the latter can be collected as one fraction. The fractionation in fast, done in one step and automated.

Characterization of Dissolved Kraft Lignin by Capillary Zone Electrophoresis

Abstract This report presents a method to characterize underivatized lignin by Capillary Zone Electrophoresis (CZE), in which separation is achieved by differences in mobility due to differences in the charge-to-size ratios of the solutes. A comparison has been made between the separation of lignin by CZE and earlier studies1 regarding the size and phenolic content of dissolved lignin. The samples were isolated at different times from a flow-through kraft cook and characterized by CZE in an alkaline solution. The resulting electropherograms show a molecular mobility distribution. The molecular mobility distribution of each fraction is in good agreement with its molecular size distribution and phenolic content. As the cook proceeds, the mobility of the lignin fragments increases with increasing phenolic content. Although the molecular size distribution shows a slight increase in molecular weight at the end of the cook according to Size Exclusion Chromatography (SEC), this does not seem to affect the mobili...

Gas chromatographic analysis of high-molecular-weight polynuclear aromatic hydrocarbons: I. Molecular weight 328

Abstract Various columns were investigated with respect to the gas chromatographic analysis of polynuclear aromatic hydrocarbons (PAHs) having molecular weights that exceed 300. Among the columns tested, four columns differing in stationary phase composition were carefully evaluated. Three of these columns were commercially available. The evaluation was focused on cata-condensed PAHs of molecular weight 328. Temperature-programmed retention indices with PAHs as reference markers were calculated and compared.

Separation of polycyclic aromatic compounds from complex oil samples using bonded phase backflush h.p.l.c. and g.c.-m.s. techniques

Abstract A novel method for the isolation of polycyclic aromatic compounds (PAC) from complex samples is presented. The method is a combination of fast separation on a short silica column and automated bonded normal phase h.p.l.c. utilizing a backflush technique. Liquid-liquid extraction with dimethylsulphoxide is added as a final step for samples of high complexity. Isolation and subsequent analysis by capillary g.c. is completed within 90 min. The method has been applied to the analysis of petroleum-derived materials, shale oil and solvent-refined coal, and is demonstrated using samples of a petroleum crude oil and of used crankcase oil.