LC-MS analysis in the aquatic environment and in water treatment technology ? a critical review

Environmental contaminants of recent concern are pharmaceuticals, estrogens and other endocrine disrupting chemicals (EDC) such as degradation products of surfactants, algal and cyanobacterial toxins, disinfection by-products (DBPs) and metalloids. In addition, pesticides (especially their transformation products), microorganisms, and humic substances (HS), in their function as vehicles for contaminants and as precursors for by-products in water treatment, traditionally play an important role. The present status of the application of LC-MS techniques for these water constituents are discussed and examples of application are given. Solid-phase extraction with various non-selective materials in combination with liquid chromatography (LC) on reversed-phase columns have been the most widely used methods for sample preconcentration and separation for different compound classes like pesticides, pharmaceuticals or estrogens. Electrospray ionization (ESI) and atmospheric pressure ionization (APCI) are the most frequently used ionization techniques for polar and ionic compounds, as well as for less polar non-ionic ones. The facilities of LC-MS have been successfully demonstrated for different compound classes. Polar compounds from pharmaceuticals used as betablockers, iodinated X-ray contrast media, or estrogens have been determined without derivatization down to ultratrace concentrations. LC-MS can be viewed as a prerequisite for the determination of algal and cyanobacterial toxins and the homologues and oligomers of alkylphenol ethoxylates and their metabolites. Tandem mass spectrometric techniques and the use of diagnostic ions reveal their usefulness for compound-class specific screening and unknown identification, and are also valid for the analysis of pesticides and especially for their transformation products. Structural information has been gained by the application of LC-MS methods to organometallic species. New insights into the structural variety of humic substances have been made possible by FT-ICR-MS due to its ultrahigh mass resolution. Finally, exciting possibilities for rapid detection and identification of microorganisms have been made possible by MALDI and LC-MS methods.

Kinetic study of photocatalytic degradation of carbamazepine, clofibric acid, iomeprol and iopromide assisted by different TiO2 materials--determination of intermediates and reaction pathways

The light-induced degradation of clofibric acid, carbamazepine, iomeprol and iopromide under simulated solar irradiation has been investigated in aqueous solutions suspended with different TiO2 materials (P25 and Hombikat UV100). Kinetic studies showed that P25 had a better photocatalytic activity for clofibric acid and carbamazepine than Hombikat UV100. For photocatalytic degradation of iomeprol Hombikat UV100 was more suitable than P25. The results can be explained by the higher adsorption capacity of Hombikat UV100 for iomeprol. The study also focuses on the identification and quantification of possible degradation products. The degradation process was monitored by determination of sum parameters and inorganic ions. In case of clofibric acid various aromatic and aliphatic degradation products have been identified and quantified. A possible multi-step degradation scheme for clofibric acid is proposed. This study proves the high potential of the photocatalytic oxidation process to transform and mineralize environmentally relevant pharmaceuticals and contrast media in water.

Effect of an industrial waste water on the nitrification in fixed-bed biofilm reactors--use of fluorescence in-situ hybridization (FISH)

The influence of an industrial waste water containing partly toxic and poorly biodegradable substances on an autotrophic biocenosis was investigated. Nitrifying bacteria were identified using fluorescently-labeled oligonucleotide probes and epifluorescence microscopy. Industrial waste water was used untreated and after ozonation to simulate the effects of indirect discharge to municipal waste water treatment plants. Results were compared to those obtained with acetate as a non-toxic and easily biodegradable substance and a mixture of acetate and pyruvate. The degradation of ammonium and the formation of nitrite and nitrate were measured and compared with the results obtained by fluorescence in-situ hybridization (FISH). The untreated waste water, containing higher amounts of refractory substances, disturbed nitrification, which was restored after reaching higher elimination of the organic substances. However, it showed only minor effects on the bacterial composition. These findings were similar to those reached by the addition of acetate and pyruvate. On the other hand, the ozonated waste water, showing higher toxicity than the untreated waste water, caused a stabilization in nitrification, but the composition of the population of ammonium-oxidizing bacteria changed significantly. In all cases, nitrite-oxidizing bacteria were only little affected both in activity and abundance.

LC-MS analysis in the aquatic environment and in water treatment--a critical review. Part I: Instrumentation and general aspects of analysis and detection

LC-MS has become an invaluable technique for trace analysis of polar compounds in aqueous samples of the environment and in water treatment. LC-MS is of particular importance due to the impetus it has provided for research into the occurrence and fate of polar contaminants, and of their even more polar transformation products. Mass spectrometric detection and identification is most widely used in combination with sample preconcentration, chromatographic separation and atmospheric pressure ionization (API). The focus of the first part of this review is directed particularly toward instruments and method development with respect to their applications for detecting emerging contaminants, microorganisms and humic substances (HS). The current status and future perspectives of 1) mass analyzers, 2) ionization techniques to interface liquid chromatography (LC) with mass spectrometry (MS), 3) methods for preconcentration and separation with respect to their application for water analysis are discussed and examples of applications are given. Quadrupole and ion trap mass analyzers with electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) are already applied in routine analysis. Time-of-flight (TOF) mass spectrometers are of particular interest for accurate mass measurements for identification of unknowns. For non-polar compounds, different ionization approaches have been described, such as atmospheric pressure photoionization (APPI), electrochemistry with ESI, or electron capture ionization with APCI. In sample preconcentration and separation, solid phase extraction (SPE) with different non-selective sorbent materials and HPLC on reversed-phase materials (RP-HPLC) play the dominant role. In addition, various on-line and miniaturized approaches for sample extraction and sample introduction into the MS have been used. Ion chromatography (IC), size-exclusion chromatography (SEC), and capillary electrophoresis (CE) are alternative separation techniques. Furthermore, the issues of compound identification, matrix effects on quantitation, development of mass spectral libraries and the topic of connecting analysis and toxicity bioassays are addressed.

Photoformation of low-molecular-weight organic acids from brown water dissolved organic matter

This work describes the effects of simulated solar UV light on the bulk properties of dissolved organic matter (DOM) of bog lake water and on the formation of low-molecular-weight organic acids (LMWOAs). By means of size-exclusion chromatography it was shown that the more hydrophilic moieties of the DOM were preferentially photodegraded while the more hydrophobic ones remained relatively unaffected or were even formed. The combined photochemical-biological degradation proved to be more important than the pure photochemical mineralization. Formic, acetic, pyruvic, oxalic, malonic, and succinic acids were identified as important degradation products. Their contribution to the dissolved organic carbon increased from 0.31% before to 6.4% after 24 h irradiation. About 33% of the bioavailable photoproducts of DOM were comprised of these LMWOAs. The influence of nitrate on the formation of carboxylic acids could not be observed in the investigated system. Kinetic experiments indicated that degradation of LMWOAs occurred simultaneously during irradiation experiments, alpha-oxygen-substituted LMWOAs being more amenable to these processes. Dissolved iron acted as a catalyst of DOM photodegradation and LMWOA photoformation. Copper played an antagonistic role in the irradiation experiments, reducing the formation of formic, acetic, and malonic acids while increasing the formation of oxalic acid.

Fate of pharmaceuticals--photodegradation by simulated solar UV-light

The fate of pharmaceuticals in surface waters under solar irradiation was investigated. Photodegradation of pharmaceuticals caused by sun irradiation may be of major significance in the natural elimination process. Based on a data compilation from the literature, the lipid lowering agent metabolite clofibric acid, the iodinated X-ray contrast media iomeprol, which contribute to the adsorbable organic halogen compounds, and the antiepileptic drug carbamazepine were selected. The irradiation experiments were carried out in batch experiments with simulated UV-sunlight. The photodegradation of the pharmaceuticals showed a pseudo-first-order kinetics. The objective of this investigation was to demonstrate that the extent of photoinduced degradation of pharmaceuticals can vary significantly for the different pharmaceuticals and it strongly depends on the water constituents present in solution. The influences of different initial pharmaceutical concentrations, the presence of other pharmaceuticals like carbamazepine or clofibric acid and the presence of natural organic matter on the photochemical degradation rate of pharmaceuticals in aqueous solutions were investigated. Analyses of the pharmaceuticals and their photodegradation products were carried out by high performance liquid chromatography with diode-array and fluorescence detection.

NOM-facilitated transport of metal ions in aquifers: importance of complex-dissociation kinetics and colloid formation

The transport of metal ions (Al, Fe, Zn, Pb) complexed by natural organic matter (NOM) was investigated by column experiments. Direct breakthrough of metal-NOM complexes was observed after elution of one bed volume for Al, Fe, and Pb, but not for Zn. This observation cannot be understood assuming local thermodynamic equilibrium in the columns. Hence, a model was developed, taking into account the kinetics of the interactions of metal ions with NOM and the solid phase. Of all possible reactions during passage through the column, the dissociation of the metal-NOM complexes was assumed to be the rate-determining step. Dissociation-rate constants were determined by cation-exchange experiments with a non-NOM-adsorbing cation-exchange resin (Chelex-100). These rate constants were used to predict the migration of metal-NOM complexes in the column experiments. Experimental and modeling results were in good agreement for the bivalent metal ions. Also, the model well predicted the pH dependence of breakthrough of trivalent metal ions and the differences between Al and Fe breakthrough on a qualitative basis. This leads to the conclusion that the dissociation kinetics of metal-NOM complexes is an essential parameter for the estimation of NOM-facilitated metal transport. However, for the trivalent metals, Al and Fe, the model overestimated the direct breakthrough, thus giving a worst case prediction of metal transport. With the help of coupling size-exclusion chromatography to inductively coupled plasma-mass spectrometry, the formation of Al-hydroxide and Fe-hydroxide colloids in addition to NOM complexes was detected. These colloids, which were not considered in the model, were partially filtered off in the column, thus leading to overestimation of metal breakthrough.

Short-term tests with a pilot sewage plant and biofilm reactors for the biological degradation of the pharmaceutical compounds clofibric acid, ibuprofen, and diclofenac

The biodegradation of three active compounds of pharmaceuticals clofibric acid, ibuprofen, and diclofenac was investigated in short-term tests with a pilot sewage plant (PSP) and biofilm reactors (BFR, oxic and anoxic) as model systems for municipal sewage treatment. The PSP was characterized with respect to mixing behavior, the BFR with respect to biofilm content and sorption of the pharmaceutical compounds. The short-term experiments were carried out for 55 h in the PSP and for 48 h in the BFR. The concentration of the pharmaceuticals was in the microgram per liter range in presence of readily biodegradable substances in the milligram per liter range. Therefore, a too short time period and too low concentration to promote adaption of the microorganisms were applied. Under the operating conditions applied the biodegradation of the lipid lowering agent clofibric acid and the analgesic agents ibuprofen and diclofenac in the oxic BFR resembled that in the PSP. Clofibric acid and diclofenac were not eliminated and reached a level of approximately 95% of their initial concentration, whereas the concentration of ibuprofen was decreased to approximately 40% in the PSP and to approximately 35% in the oxic BFR. Both systems showed, therefore, an inherent ability for ibuprofen biodegradation. Elimination in the anoxic BFR resulted in a decrease of the concentration of all three substances to values between 60 and 80% of their initial concentration. In contrast to the PSP acetone revealed as inhibitor in the BFR. In both systems acetone was not degraded in the short-term tests.

Molecular weight characteristics of humic substances from different environments as determined by size exclusion chromatography and their statistical evaluation

Recorded molecular weights (MWs) for humic substances (HS) range from a few hundred to millions of daltons. For purposes of defining HS as a specific class of chemical compounds, it is of particular importance to ascertain if this broad range of MWs can be attributed to actual variability in molecular properties or is simply an artifact of the analytical techniques used to characterize HS. The main objectives of this study were (1)to establish if a preferential range of MWs exists for HS and (2) to determine any consistent MW properties of HS. To reach the goal, we have undertaken an approach to measure under standardized conditions the MW characteristics of a large set of HS from different natural environments. Seventy-seven humic materials were isolated from freshwater, soil, peat, and coal, such that each possessed a different fractional composition: humic acid (HA), fulvic acid (FA), and a nonfractionated mixture of HA and FA (HF). Size exclusion chromatography (SEC) was used as the analytical technique to determine molecular weight characteristics. The MW distributions were characterized by number (Mn) and weight (Mw) average MW, and by polydispersity. The complete range of Mw values varied within 4.7-30.4 kDa. The maximum Mw values were observed for peat HF and soil HA, whereas the smallest weights were measured for river water HF. Maximum values of polydispersity (3.5-4.4) were seen for peat HF and soil HA, while much lower values (1.6-3.1) were found for all preparations isolated with XAD-resins. Statistical evaluation showed consistent Mw and Mn variations with the HS source, while polydispersity was mostly a function of the isolation procedure used. A conclusion was made that HS have a preferential range of MW values that could characterize them as a specific class of chemical compounds.

Combined advanced oxidation and biodegradation of industrial effluents from the production of stilbene-based fluorescent whitening agents

Three different industrial wastewaters from the production of stilbene-based fluorescent whitening agents were investigated with regard to the applicability of advanced oxidation processes combined with biodegradation. Oxidation processes included the application of ozone, hydrogen peroxide, UV-radiation and Fenton's reagent (Fe(2+)/H(2)O(2)). Characterization of the combined chemical-biological treatment was done by sum parameters and HPLC analysis. In addition, toxicity was determined using the luminescence inhibition test. Results showed that processes producing OH-radicals without the need of UV-irradiation proved to be suited for the oxidation of all three wastewaters. H(2)O(2)/UV processes were ineffective due to the high inner filter effect of the effluents. Comparing the combined oxidative-biological process with biological treatment, the applied pre-oxidation steps did not always lead to a significant improvement of the biological degradation. In one case, an inverted treatment starting with biodegradation followed by oxidation turned out to be the preferable procedure. After oxidation with ozone or ozone combined with UV-irradiation, an increase in toxicity was partly observed indicating the formation of toxic intermediate products. In some cases samples had to be diluted before the biodegradation step to achieve a better biodegradability.

Optimization and application of SPME for the gas chromatographic determination of endosulfan and its major metabolites in the ng L(-1) range in aqueous solutions

In the present study an analytical method was optimized for the determination of alpha-endosulfan, beta-endosulfan, endosulfan sulfate, endosulfan ether and endosulfan lactone in small volumes of environmental aqueous samples using solid-phase microextraction (SPME) and gas chromatography-electron capture detection (GC-ECD). A 100 micro m polydimethylsiloxane (PDMS) phase was used for the extraction. The limit of detection (LOD) for the analytes varied between 0.01 and 0.03 micro g L(-1) with a relative standard deviation of 3 to 11%. The influence of the ionic strength on the extraction efficiency was investigated for the individual compounds. alpha-Endosulfan, beta-endosulfan, endosulfan sulfate and endosulfan ether were extracted successfully without salt addition. The extraction efficiency of endosulfan lactone was improved with 30% NaCl content. A general decrease in extraction efficiency for alpha-endosulfan, beta-endosulfan, endosulfan sulfate and endosulfan ether with high NaCl content (20-30%) in the solution was observed due to glass surface adsorption. No effect of dissolved organic material (DOM) on the extraction efficiency was observed. The extraction coefficients changed between Log K=2.17 and 3.33. A sample from the Antarctic region was analyzed using the optimized GC-ECD/SPME method. To confirm the results obtained for the real sample a GC with a mass spectrometer (MS) was used. Endosulfan sulfate, the most toxic metabolite of endosulfan, was found in the sample at a concentration of 0.3 micro g L(-1).

Electron-beam treatment of aromatic hydrocarbons that can be air-stripped from contaminated groundwater. 2. Gas-phase studies

The electron-beam (EB) degradation of volatile aromatics (benzene, toluene, ethylbenzene, xylenes: BTEX) in groundwater strip gas, which in the present work has been modeled by the introduction of the desired aromatic(s) to a stream of air or another gas, such as oxygen, is initiated essentially by the addition of *OH radicals to the aromatic ring, giving rise to hydroxycyclohexadienyl radicals, which form the corresponding peroxyl radicals upon addition of oxygen. As studied in some detail with benzene as a BTEX representative, various reactions of these lead to numerous oxidation products in a cascade of reactions, including the decomposition of products under the prevailing conditions of high turnover of the initial aromatic. Importantly, hydroxycyclohexadienylperoxyl radical formation is partly reversible, and the reactions of the hydroxycyclohexadienyl radicals, which thus have a significant presence in these systems, must therefore also be taken into consideration. In the gas phase, in contrast to the aqueous phase (see Part 1), the reactions of the hydroxycyclohexadienyl radicals lead to oligomeric products that appear to contribute, in addition to ionic clusters, to nucleation for the aerosols observed. Various nitrated products, among them nitrophenols, are observed when air is used for the stripping. However, these studies did not clear the pilot plant stage, since BTEX degradation using a bioreactor carried out in parallel was so successful that the EB technology was judged to be noncompetitive. As for the latter, expensive equipment consisting of a stripper, the EB machine, and an aerosol precipitator would be required. The condensed aerosols are biorefractory and would require further treatment for detoxification.

Ligand exchange rate of metal-NOM complexes by EDTA

Metal complexation by natural ligands is important for metal transport and distribution in surface and ground water. The goal of the work was to study the ligand exchange rate for two important metal ions in natural aquatic systems (Al, Fe) was determined using EDTA and natural organic matter (NOM) of humic type as ligands. After adding EDTA to a solution containing metal-NOM complexes, these complexes dissociated and metal-EDTA complexes were formed. Metal-NOM complexes were separated from metal-EDTA complexes with the help of size-exclusion chromatography and detected by on-line inductively coupled plasma-mass spectrometry (ICP-MS). Injecting the samples into the system over time after addition of EDTA allowed us to measure the rate of the exchange of NOM by EDTA. The experiments could be well described with a first-order rate law assuming that the dissociation of the metal-NOM complexes is the rate-determining step. The exchange rate of Fe was found to be faster than that of Al. This corresponds well with the exchange rate of water molecules from the coordination sphere of the metal ions, which is also faster for Fe than for Al. Furthermore, the UV and the fluorescence signal of the chromatograms were measured. The results indicate that no disaggregation of NOM molecules took place, although about 75-85% of the aggregate-forming metal ions exchanged NOM by EDTA in their coordination sphere. This suggests clearly the fundamental role of NOM in colloidal transport of metals and in their bioavailability.

Water technology for specific water usage

BACKGROUND

Water is the basis for life and culture. In addition to the availability of water its quality has become a major issue in industrialized areas and in developing countries as well. Water usage has to be seen as part of the hydrological cycle. As a consequence water management has to be sustainable. The aim of the contribution is to give water usage oriented quality criteria and to focus on the technical means to achieve them.

MAIN FEATURES

Water is used for many purposes, ranging from drinking and irrigation to a broad variety of technical processes. Most applications need specific hygienic, chemical and/or physical properties.

RESULTS

To meet these demands separation and reaction principles are applied. The reuse of water and the application of water treatment with little or no waste and by-product formation is the way to go. Membrane separation and advanced oxidation including catalytic reactions are promising methods that apply natural processes in sustainable technical performance. Thus elimination of specific water constituents (e.g. salts and metals, microorganisms) and waste water cleaning (e.g. pollutants, nutrients and organic water) can be done efficiently.

OUTLOOK

Learning from nature and helping nature with appropriate technology is a convincing strategy for sustainable water management.

Identification and quantification of polar naphthalene derivatives in contaminated groundwater of a former gas plant site by liquid chromatography-electrospray ionization tandem mass spectrometry

A liquid chromatography (LC) method followed by electrospray ionization (ESI) and tandem mass spectrometry (MS-MS) was developed for the quantification of acidic naphthalene derivatives in the concentration range 0.1 to 100 microg/l without excessive sample preparation. For optimal sensitivity the LC-MS-MS measurements were performed recording mass fragmentation by collision induced dissociation in the multiple reaction mode. The collision energy was optimized for every analyte. The matrix effects of the sample were investigated by spiking standards of 1-naphthoic acid with humic acid (HA) and with calcium chloride. While HA decreased the signal intensity an increase was observed in the presence of calcium chloride. For the investigated groundwater samples of a tar oil contaminated site a complete separation of the analytes from the sample matrix by reversed-phase separation could be obtained. The absence of matrix effects on quantification results was confirmed by comparison of results based on external calibration with those based on standard addition of the analytes to a groundwater sample. In four groundwater samples of the contaminated site naphthalene derivatives like 1-naphthoic acid, 2-naphthoic acid, 1-naphthylacetic acid, 2-naphthylacetic acid, 1-hydroxy-2-naphthoic acid, 2-hydroxy-3-naphthoic acid, and naphthyl-2-methylenesuccinic acid have been detected.

Fractionation of natural organic matter in drinking water and characterization by 13C cross-polarization magic-angle spinning NMR spectroscopy and size exclusion chromatography

Natural organic matter from drinking water sources was fractionated, and the fractions were characterized by NMR and SEC with the aim of relating NOM structure to treatability. Organic matter was isolated from two Australian surface waters (Horsham, Moorabool) by reverse osmosis and from a groundwater (Wanneroo) by anion exchange. The isolates were fractionated according to polarity and charge by resin adsorption. 13C NMR spectra of the freeze-dried fractions showed the most hydrophobic fraction to be high in aliphatic and aromatic carbon while slightly hydrophobic organics have more carbonyl and alkoxyl carbon. The Horsham and Wanneroo hydrophilic fractions show strong alkoxyl signals attributed to carbohydrate. Moorabool hydrophilics contain aromatic (phenolic) carbon; the apparent absence of carbohydrate appears to be an artifact. Size-exclusion chromatograms were recorded on the original and fractionated organics with both UV and dissolved organic carbon detection. The Horsham and Moorabool organics have similar molecular size distributions while Wanneroo is dominated by strongly absorbing species having large hydrodynamic radii. The hydrophobic and charged hydrophilic fractions also have high apparent MW, while the neutral fraction is higher in low-MW compounds of relatively low specific absorbance, suggestive of carbohydrates.

Influence of natural organic matter on the adsorption of metal ions onto clay minerals

The influence of natural organic matter (NOM) on the adsorption of Al, Fe, Zn, and Pb onto clay minerals was investigated. Adsorption experiments were carried out at pH = 5 and pH = 7 in the presence and absence of NOM. In general, the presence of NOM decreased the adsorption of metal ions onto the clay particles. Al and Fe were strongly influenced by NOM, whereas Zn and Pb adsorption was only slightly altered. The interaction of the metal ions with the minerals and the influence of NOM on this interaction was investigated by coupling SdFFF with an inductively coupled plasma mass spectrometer (ICPMS) or an inductively coupled plasma atomic emission spectrometer (ICPAES). Quantitative atomization of the clay particles in the ICP was confirmed by comparing elemental content determined by direct injection of the clay into the ICPMS with values from acid digestion. Particle sizes of the clays were found to be between 0.1 and 1 microm by sedimentation field-flow fractionation (SdFFF) with UV detection. Aggregation of particles due to metal adsorption was observed using SdFFF-ICPMS measurements. This aggregation was dependent on the specific metal ion and decreased in the presence of NOM and at higher pH value.

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.