Removal and environmental exposure of alcohol ethoxylates in US sewage treatment.

Alcohol ethoxylates (AE) are a common nonionic surfactant employed in consumer and industrial detergents worldwide. Commercial AE are typically complex mixtures composed of > 100 homologous compounds with varying alkyl chain lengths and varying numbers of ethylene oxide (EO) units. Recent improvements in analytical methodology have enabled accurate measurement of the entire AE mixture in sewage treatment plant (STP) influents and effluents, including alkyl chain lengths from 12 to 18 carbons with a range of ethoxylation from 0 to 18 EO units. These improved analytical methods were used to measure AE concentrations at nine sites representative of sewage treatment processes and geographical locations. These new data will make possible a more accurate assessment of environmental risk for AE in the United States. The results indicate that all AE homologues are effectively removed (> 99%) in the most common treatment types. Individual STP total AE effluent concentrations ranged from a low of 0.92 microg/L for activated sludge to a high of 15.6 microg/L for a trickling filter process. For the purpose of representing a national average distribution, an average-flow-weighted wastewater treatment plant effluent concentration was determined for each AE component. The total-flow-weighted average AE effluent concentration was 3.64 microg/L.

Acute and chronic aquatic toxicity structure-activity relationships for alcohol ethoxylates.

Acute and chronic toxicity tests using the cladoceran Daphnia magna were conducted on several alcohol ethoxylate surfactants. Exposure and homologue distributions were confirmed using specific analytical methods. These data were used to test currently available acute structure-activity relationships (SARs) and to develop a new chronic SAR to extrapolate test data to effluent or receiving water mixtures. Existing acute SARs adequately predicted the toxicity of these materials with an r(2) of 0.96 based on alkyl chain length and number of ethoxylates and 0.98 based on logK(ow). The additional chronic toxicity data allowed for development of a chronic SAR based on logK(ow) and produced an r(2) of 0.93. Slopes of new and published acute, chronic, and mesocosm SARs based on logK(ow) ranged from -0.61 to -0.87. These new data and refined SARs will assist in the toxicity prediction of mixtures in the environment.

Derivatization LC/MS for the simultaneous determination of fatty alcohol and alcohol ethoxylate surfactants in water and wastewater samples.

A new LC/MS method has been developed for the simultaneous measurement, in water and wastewater samples, of all species contained in commercial samples of linear type of alcohol ethoxylate (AE) surfactants including fatty alcohols. The method requires derivatization of the terminal hydroxyl of each surfactant species with 2-fluoro-N-methylpyridinium p-toluenesulfonate, which imparts a permanent cationic charge, allowing all species including the fatty alcohols and those with only one ethoxylate to be effectively detected by electrospray MS. Detection limits of typically <10 ppt for each individual species were attained in treated wastewater, in which total AE concentrations (combination of up to 114 individual species) are not expected to exceed 10 ppb. The method was validated for clean water as well as sewage influent and effluent samples.

Rapid extraction and structural characterization of biomolecules in agarose gels by laser desorption Fourier transform mass spectrometry.

A method originally developed for the extraction of biomolecules from agarose gel slices has been utilized as a rapid means of isolating biological compounds from gels for subsequent structural characterization by matrix-assisted last desorption-ionization Fourier transform mass spectrometry (MALDI/FTMS). This "freeze-squeeze" extraction method involves pressure extrusion of fluid from frozen gel slices and provides near 50% recovery of analyte in less than 5 min. Experiments were directed at examining the recovery efficiency of the extraction method using 14C-labeled adenosine monophosphate and investigating the effect of high buffer concentrations on the laser desorption mass spectra. When coupled with this extraction technique, MALDI/FTMS can be used to detect and identify biomolecules at the low picomole level in agarose gel slices. The accurate mass measurements and MS/MS capabilities of the FTMS were exploited to provide detailed structural information at the isomeric level for oligonucleotides electrophoresed into agarose gels.

Thin-layer chromatography/liquid secondary ion mass spectrometry in the determination of major bile salts in dog bile.

Positive and negative ion liquid-state secondary-ion mass spectrometry (LSIMS) was applied to several bile acids and bile salts and their spectra were measured directly from the surface of silica gel thin-layer chromatograms. Such spectra were identical to the LSIMS spectra of the pure compound at the same concentration. Three-dimensional ion images were obtained of a model mixture of cholic, chenodeoxycholic and lithocholic acids in both the positive and negative ion modes. A sample of dog bile was prepared, and the bile acids extracted from it were separated by high-performance TLC; TLC/LSIMS spectra were obtained for sodium taurocholate and sodium taurochenodeoxycholate/taurodeoxycholate, the predominant bile salts present. Quantitative estimates of the analytes were obtained by monitoring the ion intensity for the sample spot and a standard spot that had been developed in parallel on the same TLC plate. The concentration of sodium taurocholate in the bile of this particular dog was found to be 38 mg/ml.

Imaging analysis and selected sequence monitoring of small peptides using planar chromatography/secondary ion mass spectrometry.

Mixtures of enkephalins and bradykinins contained on silica gel thin-layer chromatograms were imaged by secondary ion mass spectrometry. Spatial profiles of the sample distribution in the chromatographic plane were determined using a precision manipulator that moves the sample into and out of the primary beam generated in a liquid metal gallium source. For instance, spatial profiles are conveniently measured by monitoring the protonated molecule [M + H]+ of each compound or, in a selected-sequence monitoring experiment, by monitoring a sequence ion common to the members of each peptide group. The latter experiment is useful for quick location and identification of a class of peptides separated by planar chromatography, including thin-layer chromatography and electrophoresis.