A liquid chromatographic system with multi-detection for the direct analysis of hydrophilic organic compounds in natural waters

Summary A combined analytical LC/HPLC system was developed which allows the direct and continuous determination of organic carbon (OC), inorganic carbon (IC), UV-Vis, fluorescence, and organically bound nitrogen in aqueous solutions in the low g/l concentration range. The arrangement is well suited as detector for the direct chromatographic characterisation of organic constituents in natural surface- and groundwaters without any sample pretreatment.     

Quantifizierung organischer Substanzen in Aktivkohleextrakten mit Hilfe der Gas-Chromatographie/Massenspektrometrie

Summary Use of activated carbon plays a significant role in water technology and analytical chemistry. Therefore determination of substances adsorbed on activated carbon is of special interest. As an example, granulated activated carbon (GAC) from a water treatment plant was serially extracted with different organic solvents. Quantitative determination of some selected compounds in the combined extracts was done by gas chromatography/mass spectrometry. The method of internal standard addition and calibration by response factors was used. The determined compounds (all of substituted benzene type) were extracted from the GAC in the concentration range from 0.2 mg/100 g (m-dichlorobenzene) to 5 mg/100 g (nitrobenzene). Relative standard deviation for double determination of five independent samples from the GAC filter was less than ±20%Spike experiments were performed to determine recovery efficiences. As expected, substance specific differences appeared and the recoveries were between 36% (m-dichlorobenzene) and 80% (nitrobenzene). A significant limitation for quantitative determination results from lack of available substances for calibration.     

Non-linear calibration functions in ion chromatography with suppressed conductivity detection using hydroxide eluents

The linearity of calibration curves in ion chromatography with suppressed conductivity detection using hydroxide eluents was investigated. Theoretical calibration curves were derived for strong electrolytes and weak monobasic acids and the results compared with experimental data. At low concentrations up to 1 micromol l(-1) the autoprotolysis of water induces left-curved calibration functions even for strong electrolytes like nitrate. The experimental data are best described by a quadratic function, the differences between linear and quadratic regression being up to 10%. At higher concentrations the calibration curves for strong electrolytes are linear. Due to incomplete dissociation, the calibration curves for weak mono- and dibasic acids show a right curvature. Thus, depending on the analyte and the concentration range of interest, analysts should carefully choose between a linear and a quadratic regression function.     

Valency tautomerism of triosereductone via hydrogen bonds

The strongly temperature-dependent¹H-nmr spectrum of prop-1-en-1,2-diol-3-one (triosereductone), C₃H₄O₃, can be explained on the basis of valency tautomerism. Intramolecular hydrogen bonding is responsible for this effect.The helpful support of the Deutsche Forschungsgemeinschaft is gratefully acknowledged.     

Speciation of As(III), As(V), MMA and DMA in contaminated soil extracts by HPLC-ICP/MS

A method to separate and quantify two inorganic arsenic species As(III) and As(V) and two organic arsenic species, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA), by HPLC-ICP/MS has been developed. The separation of arsenic species was achieved on the anionic exchange column IonPac^®AS11 (Dionex) with NaOH as mobile phase. The technique was successfully applied to analyze extracts of two contaminated soils, sampled at a former tannery site (soil 1) and a former paint production site (soil 2). The soils were extracted at pH values similar to the natural environment. Extractions were performed at different pH values with 0.3 M ammonium oxalate (pH = 3), milli-Q water (pH = 5.8), 0.3 M sodium carbonate (pH = 8) and 0.3 M sodium bicarbonate (pH = 11). No organically bound arsenic was found in the extracts. As(V) was the major component. Only up to 0.04% of the total arsenic contained in soil 1 were mobilized. The highest amount of extracted arsenic was found at the highest pH. In the milli-Q water extract of soil 1 As(III) and As(V) were found. High amounts of As(V) were found in the extracts of soil 2. Up to 20% of the total arsenic bound to soil 2 constituents were released. The results show that the mobilization of arsenic depended on the pH value of the extraction solution and the kind of extracted soil. Dramatic consequences have to be expected for pH changes in the environment especially in cases where soils contain high amounts of mobile arsenic.