Patrick De Wispelaere

Levofloxacin ozonation in water: rate determining process parameters and reaction pathway elucidation.

Ozonation of the quinolone antibiotic levofloxacin was investigated with focus on both the levofloxacin degradation rate and degradation product formation. Degradation was about 2 times faster at pH 10 compared to pH 3 and 7 explained by direct ozonation at the unprotonated N4(), one of the tertiary amines of the piperazinyl substituent. H2O2 concentration (2-100 microM) had only limited effect. Liquid chromatography - high resolution mass spectrometry revealed degradation at the piperazinyl substituent and the quinolone moiety, with the relative importance of both pathways being strongly affected by changes in pH. Levofloxacin N-oxide concentrations reached up to 40% of the initial levofloxacin concentration during ozonation at pH 10. Degradation at the quinolone moiety resulted in isatin and anthranilic acid type metabolites, probably formed through reaction with hydroxyl radicals. Ab initio molecular orbital calculations predicted radical attack mainly at C2 of the quinolone moiety. This is the carbon atom with the largest Fukui function. Reaction with ozone is expected to mainly occur at N(4)(), characterized by the largest negative charge.

Ciprofloxacin ozonation in hospital wastewater treatment plant effluent: Effect of pH and H2O2

The ozonation of ciprofloxacin was studied in hospital wastewater treatment plant effluent with focus on parent compound degradation, degradation product identification and residual antibacterial activity. Before ozonation, ciprofloxacin sorption on suspended solids was tested as a function of temperature (10.0-27.5 degrees C) and pH (3, 7 and 10). Temperature did not significantly affect ciprofloxacin sorption while sorption was highest at pH 7 (logK(d)=4.7) compared to pH 3 (logK(d)=4.3) and 10 (logK(d)=3.9) (n=3). Ozonation was slowest at pH 7 with ciprofloxacin half life times of 29 min, compared to 19 and 27 min at pH 10 and 3, respectively. Addition of 10-1000 microM H(2)O(2) increased ciprofloxacin half life times up to 38 min, probably influenced by competition with H(2)O(2) for ozone as well as radical species. Ciprofloxacin ozonation products were identical as previously detected during ciprofloxacin ozonation in deionized water and revealed strong pH dependence. Residual antibacterial activity was measured by agar diffusion tests. For Pseudomonas fluorescens and Escherichia coli, reduction of antibacterial activity was related to the parent compound degradation, while degradation products indicated to be the main compounds with respect to the antibacterial activity against Bacillus coagulans.

From multi-residue screening to target analysis of pharmaceuticals in water: Development of a new approach based on magnetic sector mass spectrometry and application in the Nairobi River basin, Kenya

This paper presents the development and application of a new multi-residue analytical method providing the first data on the environmental occurrence of human pharmaceuticals in Africa, particularly the Nairobi River basin (Kenya). Based on pharmaceutical consumption data available for the Nairobi region, 43 priority pharmaceutically active ingredients (PAIs) were selected for this study. On the basis of magnetic sector high-resolution mass spectrometry, a new methodology involving both full-scan screening and selective target analysis has been developed to investigate the presence of the defined priority PAIs. Subsequent analysis of the corresponding standard compounds provided the full confirmation and indicative concentrations (low ng/L-high μg/L) of 10 human PAIs in the Nairobi River. The detected compounds belong to different classes, i.e. antibiotics, analgesic/anti-inflammatory and anti-epileptic drugs, antimalarials and antiretrovirals. Ibuprofen, paracetamol, sulfamethoxazole and zidovudine showed to be the most concentrated PAIs (about 10-30 μg/L). The concentration of the antiretrovirals (lamivudine, zidovudine and nevirapine) is clearly higher than those reported in the literature, although environmental data on this class of PAIs are still very limited. To the best of our knowledge, this is the first study that provides evidence of detection of lamivudine in surface water. The presented unique data on the occurrence of selected PAIs in the aquatic environment of Africa clearly show that the high prevalence of specific diseases like HIV/AIDS infection in developing countries might result in a different pattern of PAIs in environmental waters compared to the more developed regions.

Multi-residue analysis of pharmaceuticals in wastewater by liquid chromatography–magnetic sector mass spectrometry: Method quality assessment and application in a Belgian case study

Through systematic research a novel analytical method using solid-phase extraction (SPE) and liquid chromatography magnetic sector mass spectrometry was developed for the measurement of 43 pharmaceuticals in wastewater. A thorough method validation quantified the contribution of both the extraction recovery and matrix effects in the overall method process efficiency, and a detailed uncertainty analysis was performed to elaborate a quality labelling strategy to be used in data interpretation. Compounds for which a precise (relative standard deviation<20%) process efficiency between 60% and 140% was determined, were labelled as quantitative whereas the results for other compounds should be interpreted as indicative. Method application on influent and effluent samples of (i) a conventional active sludge system and (ii) a parallel membrane bioreactor/conventional active sludge wastewater treatment plant in Belgium revealed the occurrence of 22 pharmaceuticals. The anti-inflammatory drug diclofenac and the antidepressant venlafaxine were measured in the effluents at concentrations ranging from 0.5 to 1.8 μg L(-1) and 0.2 to 0.5 μg L(-1), respectively, which indicated to be of high potential environmental risk for the receiving river Dender, Belgium.

Statistical procedures for the determination of linearity, detection limits and measurement uncertainty: A deeper look into SPE-LC-Orbitrap mass spectrometry of pharmaceuticals in wastewater.

This research addresses some critical challenges regarding the validation of a quantitative multi-residue method for pharmaceuticals in wastewater making use of modern SPE-LC-Orbitrap high-resolution mass spectrometry. Particular attention is given to study in detail response linearity, to realistically estimate detection limits, and to express the measurement precision of the analyte concentration, obtained by external calibration. First, linearity of the Orbitrap response showed to be matrix dependent in a counter intuitive way: stronger deviations from linearity were observed for pure solvent standards than for complex matrices like wastewater. Second, detection limits risk to be overestimated for ubiquitously present compounds for which true blank matrix samples are hard to find, leading to false negative findings. A novel and easy applicable methodology is presented to allow a better estimation of detection limits using the response of the natural isotopes. Third, a statistical methodology to estimate the measurement precision of the analyte concentration using basic validation parameters is developed specifically for the context of multi-residue quantification.

Volatile organic compounds in an urban environment: a comparison among Belgium, Vietnam and Ethiopia

The effects of urban and indoor air pollution on human health are a major environmental concern for all, but not much has been researched in the developing world. Specifically, quantitative data on the occurrence of volatile organic compounds (VOCs) – main contributors to air pollution – in Asia and Africa are scarce compared to the availability of data in the developed world. This paper presents one of the first studies focusing on the analysis and occurrence of VOCs in Vietnam and Ethiopia, which constitutes part of the novelty of this work. A spectrum of 34 VOCs was measured at eight different urban sites in Ghent (Belgium), Hanoi (Vietnam), Jimma and Addis Ababa (Ethiopia) during three sampling campaigns from September 2008 to September 2010. Sampling was done in an active way by means of sorbent tubes filled with Tenax TA. The analysis was done by TD-GC-MS using internal standard calibration. Data were interpreted and compared in terms of (i) individual, subgroup and total VOCs concentration (TVOCs), (ii) indoor-to-outdoor (I/O) concentration ratios, (iii) source identification by diagnostic ratio and/or correlation coefficients, and (iv) ozone formation potential (OFP) at outdoor sites based on up-to-date maximum incremental reactivity (MIR). I/O concentration ratios varied between 0.2 and 30, with big differences noticed with respect to the type of VOC(s) considered and the type of outdoor sampling location. The highest TVOC concentrations were measured in street samples with maximum values of 54u2009µg/m3 in Ghent, 507u2009µg/m3 in Hanoi and 318u2009µg/m3 in Addis Ababa illustrating the large difference in ambient air quality levels. This is also reflected in the arithmetic mean OFP values (µg/m3) of 82, 1308 and 596 in Ghent, Hanoi and Addis Ababa, respectively. Results of this study could be helpful to support formulation of national policy with regard to ambient air quality.

Development of an analytical method to determine oxy-PAHs and PAHs in Taxus baccata leaves

An analytical method was developed and optimized for the quantification of 16 polycyclic aromatic hydrocarbons (PAHs) and 12 oxygenated PAHs in Taxus baccata leaves. Emphasis was given to the development of an in-cell cleanup step using pressurized solvent extraction, a cleanup step using solid-phase extraction, and the instrumental analysis by GC-HRMS. Different extraction temperatures (between 50 and 200xa0°C) and Florisil quantities were evaluated for the extraction process. Based on the evaluation of both recoveries and matrix effect factors, a temperature of 200xa0°C and 1xa0g Florisil was selected as the optimum. However, the in-cell cleanup was not sufficient in the long term due to increasing chromatographic peak broadening, and further cleanup was necessary. Solid-phase extraction (using Florisil) was evaluated, and breakthrough curves were acquired for all target compounds to determine the optimal elution volume and avoiding matrix interference. Recoveries of the target compounds ranged from 58 to 87xa0% for the PAHs and from 5 to 105xa0% for the oxy-PAHs. Matrix effects were determined for all individual target compounds. The optimized method was applied to T. baccata samples obtained from ten sampling locations in Ghent, Belgium. This is the first biomonitoring study in Ghent for PAHs and oxy-PAHs. The presence of significant amounts of toxicologically relevant oxygenated PAHs (Oxy-PAHs) (can enhance ROS formation in human lung cells) in T. baccata was confirmed (max ∑Oxy-PAHs: 230xa0ng/g; max ∑PAHs: 389xa0ng/g). This means that these oxygenated PAHs are important pollutants and should be included in future monitoring studies.