New developments in the analysis of fragrances and earthy–musty compounds in water by solid-phase microextraction (metal alloy fibre) coupled with gas chromatography–(tandem) mass spectrometry

Synthetic Musk Fragrances in Water Systems and Their Impact on Microbial Communities

The presence of emerging contaminants in aquatic systems and their potential effects on ecosystems have sparked the interest of the scientific community with a consequent increase in their report. Moreover, the presence of emerging contaminants in the environment should be assessed through the “One-Health” approach since all the living organisms are exposed to those contaminants at some point and several works already reported their impact on ecological interactions. There are a wide variety of concerning emerging contaminants in water sources, such as pharmaceuticals, personal care products, house-care products, nanomaterials, fire-retardants, and all the vast number of different compounds of indispensable use in routine tasks. Synthetic musks are examples of fragrances used in the formulation of personal and/or house-care products, which may potentially cause significant ecotoxicological concerns. However, there is little-to-no information regarding the effect of synthetic musks on microbial communities. This study reviews the presence of musk fragrances in drinking water and their impact on aquatic microbial communities, with a focus on the role of biofilms in aquatic systems. Moreover, this review highlights the research needed for a better understating of the impact of non-pharmaceutical contaminants in microbial populations and public health.

The formation, analysis, and control of chlor(am)ination-derived odor problems: A review

Odors and tastes have become universal problems related to drinking water quality. In addition to the typical odor problems caused by algae or microorganisms, the occurrence of odors derived from drinking water disinfection have attracted attention. The chlor(am)ination-derived odor substances have certain toxicity and odor-causing characteristics, and would enter the tap water through water distribution systems, directly affecting drinking water safety and customer experience. This study provided a comprehensive overview of the occurrence, detection, and control of odor substances derived from drinking water chlor(am)ination disinfection. The occurrence and formation mechanisms of several typical types of disinfection derived odor substances were summarized, including haloanisoles, N-chloroaldimines, iodotrihalomethanes, and halophenoles. They are mainly derived from specific precursors such as halophenols, anisoles, and amino acids species during the disinfection or distribution networks. In addition, the change of disinfectant during chlor(am)ination was also one of the causes of disinfection odors. Due to the extremely low odor threshold concentrations (OTCs) of these odor substances, the effective sample pre-enrichment for instrument identification and quantification are essential. The control strategies of odor problems mainly include adsorption, chemical oxidation, and combined processes such as ozonation and biological activated carbon processes (O₃/BAC) and ultraviolet-based advanced oxidation processes (UV-AOPs). Finally, the challenges and possible future research directions in this research field were discussed and proposed.

A critical review on geosmin and 2-methylisoborneol in water: sources, effects, detection, and removal techniques

The exposure to geosmin (GSM) and 2-methylisoborneol (2-MIB) in water has caused a negative impact on product reputation and customer distrust. The occurrence of these compounds and their metabolites during drinking water treatment processes has caused different health challenges. Conventional treatment techniques such as coagulation, sedimentation, filtration, and chlorination employed in removing these two commonest taste and odor compounds (GSM and 2-MIB) were found to be ineffective and inherent shortcomings. The removal of GSM and MIB were found to be effective using combination of activated carbon and ozonation; however, high treatment cost associated with ozonation technique and poor regeneration efficiency of activated carbon constitute serious setback to the combined system. Other shortcoming of the activated carbon adsorption and ozonation include low adsorption efficiency due to the presence of natural organic matter and humic acid. In light of this background, the review is focused on the sources, effects, environmental pathways, detection, and removal techniques of 2-MIB and GSM from aqueous media. Although advanced oxidation processes (AOPs) were found to be promising to remove the two compounds from water but accompanied with different challenges. Herein, to fill the knowledge gap analysis on these algal metabolites (GSM and 2-MIB), the integration of treatment processes vis-a-viz combination of one or more AOPs with other conventional methods are considered logical to remove these odorous compounds and hence could improve overall water quality.

Increased electrode activity during geosmin oxidation provided by Pt nanoparticle-embedded nanocarbon film

The musty odor compound geosmin was electrochemically detected by using Pt nanoparticle (PtNP)-embedded nanocarbon (Pt-C) films formed with unbalanced magnetron (UBM) co-sputtering. The sputtered Pt components formed NPs (typically 1.53-4.75 nm in diameter) spontaneously in the carbon films, owing to the poor intermiscibility of Pt with carbon. The surface concentrations of PtNPs embedded in the nanocarbon film were widely controllable (Pt = 4.8-35.9 at%) by regulating the target powers of the Pt and carbon individually. The obtained film had a flat surface (Ra = 0.17-0.18 nm) despite the fact the PtNPs were partially exposed at the surface. Compared with a Pt film electrode, some Pt-C films exhibited higher electrode activity against geosmin although the surface Pt concentrations of these Pt-C films were much lower than that of the Pt film electrode, thanks to the wider potential window and lower background current that resulted from the ultraflat and stable carbon-based film prepared by UBM co-sputtering. Computational experiments revealed that the theoretical oxidation potential (Eox) value for geosmin was relatively similar to that obtained in electrochemical experiments using our Pt-C film electrode. Moreover, we also theoretically estimated the possible oxidation site of geosmin molecules and the advantage of the NP shape of the electroactive Pt parts as regards the electrochemical oxidation of geosmin. We successfully used the Pt-C film (10.6 at%) electrode to detect geosmin in combination with HPLC at a low detection limit of 100 ng L-1.

Simultaneous quantification of fifty-one odor-causing compounds in drinking water using gas chromatography-triple quadrupole tandem mass spectrometry

A wide range of compounds with various structural features can cause taste and odor (T&O) problems in drinking water. It would be desirable to determine all of these compounds using a simple analytical method. In this paper, a sensitive method combining liquid-liquid extraction (LLE) with gas chromatography-triple quadrupole tandem mass spectrometry (GC-MS/MS) was established to simultaneously analyze 51 odor-causing compounds in drinking water, including organic sulfides, aldehydes, benzenes, phenols, ethers, esters, ketones, nitrogenous heterocyclic compounds, 2-methylisoborneol and geosmin. Three deuterated analogs of target analytes, dimethyl disulfide-d₆, benzaldehyde-d₆ and o-cresol-3,4,5,6-d_4, were used to correct the variations in recovery, and five isotope-labeled internal standards (4-chlorotoluene-d₄, 1, 4-dichlorobenzene-d₄, naphthalene-d₈, acenaphthene-d₁₀, phenanthrene-d₁₀ respectively) were used prior to analysis to correct the variations arising from instrument fluctuations and injection errors. The calibration curves of the target compounds showed good linearity (R² > 0.99, level = 7), and method detection limits (MDLs) below 1/10 of the odor threshold concentrations were achieved for most of the odorants (0.10-20.55 ng/L). The average recoveries of most of the analytes in tap water samples were between 70% and 120%, and the method was reproducible (RSD < 20%, n = 7). Additionally, concentrations of odor-causing compounds in water samples collected from three drinking water treatment plants (DWTPs) were analyzed by this method. According to the results, dimethyl trisulfide, dimethyl disulfide and indole were considered to be the key odorants responsible for the swampy/septic odor. 2-Methylisoborneol and geosmin were detected as the main odor-causing compounds for musty/earthy odor in DWTP B.

Priority Substances and Emerging Organic Pollutants in Portuguese Aquatic Environment: A Review

Aquatic environments are among the most noteworthy ecosystems regarding chemical pollution due to the anthropogenic pressure. In 2000, the European Commission implemented the Water Framework Directive, with the aim of progressively reducing aquatic chemical pollution of the European Union countries. Therefore, the knowledge about the chemical and ecological status is imperative to determine the overall quality of water bodies. Concerning Portugal, some studies have demonstrated the presence of pollutants in the aquatic environment but an overall report is not available yet. The aim of this paper is to provide a comprehensive review about the occurrence of priority substances included in the Water Framework Directive and some classes of emerging organic pollutants that have been found in Portuguese aquatic environment. The most frequently studied compounds comprise industrial compounds, natural and synthetic estrogens, phytoestrogens, phytosterols, pesticides, pharmaceuticals and personal care products. Concentration of these pollutants ranged from few ng L(-1) to higher values such as 30 μg L(-1) for industrial compounds in surface waters and up to 106 μg L(-1) for the pharmaceutical ibuprofen in wastewaters. Compounds already banned in Europe such as atrazine, alkylphenols and alkylphenol polyethoxylates are still found in surface waters, nevertheless their origin is still poorly understood. Beyond the contamination of the Portuguese aquatic environment by priority substances and emerging organic pollutants, this review also highlights the need of more research on other classes of pollutants and emphasizes the importance of extending this research to other locations in Portugal, which have not been investigated yet.

Monitoring of sixteen fragrance allergens and two polycyclic musks in wastewater treatment plants by solid phase microextraction coupled to gas chromatography

A methodology based on headspace solid phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS) determination was developed for the monitoring and evaluation of the removal efficiency of 16 common fragrance allergens and two polycyclic musks in wastewater treatment plants (WWTPs). An experimental design with a full factorial model was applied to evaluate the effects of the experimental parameters on the extraction (e.g., salt content, time and extraction temperature). After determining the optimum conditions (2.4 g NaCl, 45 min at 90 °C), an external calibration was performed and quality parameters of the proposed method were evaluated. Method detection limits in the range of 0.01-1.7 μg L(-1) were obtained. Satisfactory inter-day precision values between 4% and 23% (n=5) were obtained for most compounds. The method was applied to the monitoring of the target analytes in samples from two WWTPs. Seven target compounds were detected at the primary effluent of both plants at μg L(-1) levels. Limonene, linalool and eugenol were quantitatively eliminated during the secondary treatments of both WWTPs, while lilial, benzyl salicylate, galaxolide, and tonalide were still detected at the effluent waters.