Thorsten Reemtsma

Liquid chromatography-mass spectrometry and strategies for trace-level analysis of polar organic pollutants.

Liquid chromatography-mass spectrometry using atmospheric pressure ionization (LC-API-MS) has drastically changed the analytical methods used to detect polar pollutants in water. The present status of application of this technique to organic water constituents is reviewed. The selection of the appropriate LC conditions, whether reversed-phase liquid chromatography, ion-pair chromatography, capillary electrophoresis or ion chromatography, and of the most sensitive ionization mode, electrospray ionization (ESI) or atmospheric pressure chemical ionization (APCI), depends upon the polarity and acidity of the analytes. Strongly acidic compounds such as aromatic sulfonates, sulfonated dyes, haloacetic acids, linear alkylbenzene sulfonates, aliphatic sulfonates and sulfates and complexing agents, weakly acidic compounds such as carboxylates and phenols, neutral compound classes, namely alkylphenol ethoxylates, alcohol ethoxylates and polycyclic aromatic hydrocarbons and the basic toxins, quaternary ammonium compounds and organometallic compounds are considered. The selection of the mass spectrometer depends upon the analytical task: triple-quadrupole mass spectrometers are highly suited for sensitive quantitation and for qualitative analyses, ion traps are especially suited for structure elucidation, whereas time-of-flight mass spectrometers and quadrupole time-of-flight mass spectrometers with their higher mass resolution are ideal for the determination of molecular formulas of unknown compounds and for screening purposes. While large steps have already been made, future efforts with respect to water analysis may be directed at fine-tuning the methodical arsenal for increased sensitivity and selectivity and to extend LC-MS application to transformation products.

The use of liquid chromatography-atmospheric pressure ionization-mass spectrometry in water analysis – Part II: Obstacles

Liquid chromatography-mass spectrometry using atmospheric pressure ionization is dramatically changing the analytical methods, potential and tasks of water analysis. The present status in applying this technique to organic as well as inorganic water constituents and its use in the context of wastewater treatment and drinking water preparation is reviewed. Separation techniques such as reversed-phase HPLC, ion chromatography, capillary electrophoresis and size-exclusion chromatography are also considered. LC-MS is well established to detect industrial mass chemicals such as dyes, aromatic sulfonates, surfactants and complexing agents but also trace compounds such as drugs, endocrine-disrupting compounds, toxins, phenols and haloacetic acids. The applications of LC-MS are now expanding towards the analysis of inorganic compounds such as oxo-anion. The success in characterizing natural organic matter by LC-MS is still limited, but an interesting potential is seen in detecting organometallic complexes as well as non-covalently bound adducts following electrospray ionization.

Use of volatile amines as ion-pairing agents for the high-performance liquid chromatographic–tandem mass spectrometric determination of aromatic sulfonates in industrial wastewater

The use of trialkylamines (triethylamine, N,N-dimethyl-n-butylamine, and tri-n-butylamine) as volatile ion-pairing agents for the high-performance liquid chromatographic separation of aromatic sulfonates was investigated. Negative ion electrospray tandem mass spectrometry was used to detect both singly and multiply charged analyte ions. Sensitivity of detection was strongly reduced by amine concentrations above 2.5 mmol l(-1) in the eluent. With tributylamine as ion-pairing agent 19 aromatic sulfonic acids could be determined using time-scheduled selected reaction monitoring. Lowest orders of detection range from 3 to 74 microgl(-1). Several naphthalenesulfonic acids were determined in dyeing baths and textile wastewater in concentrations ranging from 0.1 mgl(-1) to 2.1 mgl(-1). A degradation product of sulfonated azodyes was identified in the effluent of a laboratory treatment plant.

Determination of molecular formulas of natural organic matter molecules by (ultra-) high-resolution mass spectrometry: status and needs.

Electrospray ionization (ESI) combined with ultra-high-resolution mass spectrometry on a Fourier transform ion cyclotron resonance mass spectrometer has been shown to be a very powerful tool for the analysis of fulvic and humic acids and of natural organic matter (NOM) at the molecular level. With this technique thousands of ions can be separated from each other and their m/z ratio determined with sufficient accuracy to allow molecular formula calculation. Organic biogeochemistry, water chemistry, and atmospheric chemistry greatly benefit from this technique. Methodical aspects concerning the application of Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) to NOM isolated from surface water, groundwater, marine waters, and soils as well as from secondary organic aerosol in the atmospheric are reviewed. Enrichment of NOM and its chromatographic separation as well as possible influences of the ionization process on the appearance of the mass spectra are discussed. These steps of the analytical process require more systematic investigations. A basic drawback, however, is the lack of well defined single reference compounds of NOM or fulvic acids. Approaches of molecular formula calculation from the mass spectrometric data are reviewed and available graphical presentation methods are summarized. Finally, unsolved issues that limit the quality of data generated by FTICR-MS analysis of NOM are elaborated. It is concluded that further development in NOM enrichment and chromatographic separation is required and that tools for data analysis, data comparison and data visualization ought to be improved to make full use of FTICR-MS in NOM analysis.

Microbial transformations and biological effects of fungicide-derived benzothiazoles determined in industrial wastewater.

Benzothiazole (BT), 2-mercaptobenzothiazole (MBT), and 2-(methylthio)benzothiazole (MTBT) were determined as degradation products of the fungicide 2-(thiocyanomethylthio)benzothiazole (TCMTB) in tannery wastewater and are shown to be incompletely removed (75%) in an anaerobic and aerobic wastewater treatment pilot plant. Average total concentration of these benzothiazoles is 5.7 μmol L -1 in the untreated wastewater and 1.4 μmol L- after aerobic treatment. Aerobic batch degradation tests revealed that TCMTB is transformed to MBT. MBT is primarily methylated to MTBT, which was not further degradable. BT was aerobically degraded along unknown pathways. Potential effects of benzothiazoles entering the aquatic environment are illustrated by luminescence inhibition of Vibrio fischeri (= Photobacterium phosphoreum ; EC 50 between 0.03 μmol L -1 for TCMTB and 32 μmol L -1 for BT) and growth inhibition of the same organism with TCMTB and MBT. MBT, BT, and MTBT at concentrations of 0.1- 0.2 μmol L -1 inhibit nitrification on sediment columns and mixed culture respiration determined as BOD (0.6-11 μmol L -1 ). It is concluded that 2-substituted benzothiazoles employed in industrial processes are not completely removable by biological wastewater treatment and are of concern for aquatic environment due to their limited biodegradability and potential toxicity.

Methods of analysis of polar aromatic sulfonates from aquatic environments

Methods for the analysis of aromatic sulfonates, such as linear alkylbenzene sulfonates (LAS) and (amino- and hydroxy-substituted) benzene and naphthalene sulfonates, from aqueous media are reviewed. All analytical steps including the extraction from water, clean-up from co-extracted substances, chromatographic separation and detection, and methods of identification of these compound classes are described and discussed. The techniques employed are solid-phase extraction, various modes of high-performance liquid chromatography (HPLC), capillary electrophoresis, gas chromatography (GC), GC-mass spectrometry, liquid chromatography-mass spectrometry, continuous flow- and flow injection-mass spectrometry, and spectroscopic methods. A remarkable gap becomes obvious between novel analytical methods developed with standard mixtures and those methods readily employable for environmental analysis. Finally, suggestions for future analytical developments are given.

Dissolved organics in tannery wastewaters and their alteration by a combined anaerobic and aerobic treatment

The dissolved organic load of tannery wastewater and of the effluents of an anaerobic and aerobic treatment were investigated over a 2 yr period. The average dissolved organic carbon content (DOC) of raw wastewater is 900 mg 1−1, corresponding to a discharge of 23 kg DOC t−1 raw hide. The two step biological treatment removes an average 85% of the DOC and 50% of the UV254-absorbance. The high initial toxicity of tannery wastewater, as determined in the luminescence inhibition test (EC50: 5 ml 1−1) is diminished by two orders of magnitude. GC-MS screening analyses of fractionated wastewater extracts determined about 200 individual components in the various wastewater qualities. Identified substances were grouped into 12 substance classes, among them aliphatic and aromatic carboxylic acids, alcohols, phenols, indoles, cyclohexanes and ethoxylates, and their contents were quantitatively assessed. Anaerobic and aerobic treatment exhibit significantly different impacts onto the dissolved organic matter: reproduction of raw wastewater constituents and formation/release of new components are important processes under anaerobic conditions; aromatic compounds are poorly removed. Aerobic processes aim at mineralization and are, thus, effective against all substance classes. Despite the substantial improvement of the tannery wastewater quality by the two step biological treatment, some luminescence inhibition remained (EC50: 400 ml 1−1) and persistent substances of environmental concern were identified in the fully treated effluents.

Membrane bioreactors for municipal wastewater treatment – A viable option to reduce the amount of polar pollutants discharged into surface waters?

The potential of a lab-scale membrane bioreactor (MBR) to remove polar pollutants from municipal wastewater was studied for industrial and household chemicals over a period of 22 months parallel to a conventional activated sludge (CAS) treatment. For half of the compounds, such as benzotriazole, 5-tolyltriazole (5-TTri), benzothiazole-2-sulfonate and 1,6-naphthalene disulfonate (1,6-NDSA), removal by MBR was significantly better than in CAS, while no improvement was recorded for the other half (1,5-NDSA, 1,3-NDSA, 4-TTri and naphthalene-1-sulfonate). The influence of operational conditions on trace pollutant removal by MBR was studied but no significant effects were found for variation of hydraulic retention time (7h-14h) and sludge retention time (26d-102d), suggesting that the lowest values selected have already been high enough for good removal. It is shown that the seemingly inconsistent results reported here and in previous studies regarding the comparison of trace pollutant removal in MBR and CAS are highly consistent. MBR is neither superior for well degradable compounds that are already extensively degraded in CAS treatment nor for recalcitrant compounds that are not amenable to biodegradation. For most compounds of intermediate removal in CAS treatment (15-80%), among them pharmaceuticals, personal care products and industrial chemicals, the MBR is clearly superior and reduces the effluent concentration by 20-50%. Despite of this clear benefit of MBR, the effect is not pronounced enough to serve as a sole argument for employing MBR in municipal wastewater treatment.

Determination of 14 monoalkyl phosphates, dialkyl phosphates and dialkyl thiophosphates by LC-MS/MS in human urinary samples

Human urine was analyzed for nine dialkyl (DAP) and five monoalkyl phosphates (MAP) by LC-MS/MS. Some phosphoric acid esters are industrial chemicals and other hydrolysis products of trialkyl or triaryl phosphates, used as pesticides, flame retardants or plasticizers. Five MAP and two DAP were detected here for the first time in human urine. Monobutyl, diethyl, diphenyl and diethylhexyl phosphate were determined with median concentrations in the μg/L-range. The total urinary concentration of the 14 DAP and MAP summed up to a median of 20μg/L. Inclusion of MAP in future biomonitoring studies should provide a more comprehensive picture of the exposure of humans to organophosphorus compounds.

Analysis of commercial vegetable tanning agents by reversed-phase liquid chromatography–electrospray ionization–tandem mass spectrometry and its application to wastewater

Commercial vegetable tanning agents that are derived from plants and consist of condensed or hydrolyzable tannins were analyzed by electrospray ionization-tandem mass spectrometry (ESI-MS/MS) to identify their major constituents and to study their collision-induced dissociation. In the condensed tannin wattle a series of proanthocyanidin dimers to tetramers was identified together with the flavonoid monomers catechin and gallocatechin. The composition of the hydrolyzable tannin chestnut was more heterogenous. Besides the monomers ellagic and gallic acid a variety of gallotannins were detected, namely mono-, di- and trigalloylglucose, and a variety of ellagitannins. Reversed-phase HPLC-ESI-MS/MS methods were developed to detect condensed and hydrolyzable tannins in tannery wastewaters by multiple reaction monitoring (MRM). The methods proved suitable even for highly loaded wastewaters. However, the detected amount of wattle tanning agent in spent retanning baths was about two orders of magnitude below the amount used for the retanning. This suggests that the condensed tannins of polyphenolic structure are rapidly transformed during the tanning process to yet unknown products.