Formation of chloronitrophenols upon sulfate radical-based oxidation of 2-chlorophenol in the presence of nitrite.

Sulfate radical (SO4-)-based advanced oxidation processes (SR-AOPs) are promising in-situ chemical oxidation technologies widely applied for soil/groundwater remediation. The presence of non-target water constituents may interfere the abatement of contaminants by SR-AOPs as well as result in the formation of unintended byproducts. Herein, we reported the formation of toxic chloronitrophenols during thermally activated persulfate oxidation of 2-chlorophenol (2CP) in the presence of nitrite (NO2-). 2-Chloro-4-nitrophenol (2C4NP) and 2-chloro-6-nitrophenol (2C6NP) were identified as nitrated byproducts of 2CP with total yield up to 90%. The formation of nitrated byproducts is a result of coupling reaction between 2CP phenoxyl radical (ClPhO) and nitrogen dioxide radical (NO2). As a critical step, the formation of ClPhO was supported by density functional theory (DFT) computation. Both 2C4NP and 2C6NP could convert to 2-chloro-4,6-dinitrophenol (2C46DNP) upon further treatment via a denitration-renitration process. The formation rate of 2C4NP and 2C6NP was closely dependent on the concentration of NO2-, solution pH, and natural water constituents. ECOSAR calculation suggests that chloronitrophenols are generally more hydrophobic and ecotoxic than 2CP. Our result therefore reveals the potential risks in the abatement of chlorophenols by SR-AOP, particularly when high level of NO2- is present in water matrix.

Glycine-betaine-derived ionic liquids: Synthesis, characterization and ecotoxicological evaluation.

Ionic Liquids (ILs) are generically regarded as environmentally "harmless" and thus, assumed as "non-toxic". However, due to the endless design possibilities, their ecotoxicological profile is still poorly known. An accurate knowledge on the toxicity of a substance is required, under the scope of environmental regulation worldwide, before their application and commercialization. Knowledge on the relationship between the chemical structure and toxic effects is essential for the future design of more biocompatible solvents. Focusing on the use of ILs as base lubricants, lubricant additives, or even as potential working fluids for absorption heat pumps, the knowledge on its environmental impact is of great importance, due to the possibility of spills. In this specific context, four analogues of glycine-betaine-based ILs (AGB-ILs) and four glycine-betaine based ILs (GB-ILs) were synthesized and characterized. Their ecotoxicity was assessed using representatives of two trophic levels in aquatic ecosystems, the bacteria Allivibrio fischeri (commonly used as a screening test organism) and the microalgae Raphidocelis subcapitata (as an alternative test organism that has been proven very sensitive to several IL families). The microalgae were more sensitive than the bacteria, hence, following a precautionary principle, we recommend considering the toxicity towards microalgae as an indicator in future studies regarding the focused ILs. Although four of the studied ILs were derived from a natural amino acid, all were considered hazardous for the aquatic environment, disproving the primary theory that all ILs derived from natural compounds are benign. Furthermore, the modification in the structure of anion and the cation can lead to the increase of toxicity.

Formation of N-nitrosamines by micelle-catalysed nitrosation of aliphatic secondary amines.

N-Nitrosamines are an important class of potent human carcinogens and mutagens that can be present in water and wastewater. For instance, N-nitrosamines can be formed by reaction of nitrosating agents such as NO+ or N2O3 formed from nitrite under acidic conditions with secondary amine precursors by an acid-catalysed nitrosation pathway. This study investigates the catalytic effect of cationic and anionic micelles on the nitrosation of secondary aliphatic amines in the presence of nitrite at different pH values. The results of this study demonstrate that the nitrosation of hydrophobic secondary amines (e.g., dipropylamine and dibutylamine) by nitrite was significantly enhanced in the presence of micelles of the cationic surfactant cetyltrimethylammonium chloride whereas anionic micelles formed by sodium dodecylsulfate did not significantly enhance the formation of N-nitrosamines. Rate enhancements of up to 100-fold were observed for the formation of N-nitrosodibutylamine in the presence of cetyltrimethylammonium chloride. The magnitude of the catalytic effect of cationic micelles on the nitrosation reaction depended mainly of the hydrophobicity of the amine precursors (i.e., alkyl chain length), the stability and the charge of the micelles and pH. One important enhancement factor is the lowering of the pKa of the precursor alkylammonium ion due to the electrical potential at the micelle-water interface by up to ∼2.5 pH units. These results suggest that cationic micelle-forming surfactants might play a role in the formation of N-nitrosamines in wastewater, consumer products and in industrial processes using high concentrations of cationic surfactants.

Impact of tryptophan on the formation of TCNM in the process of UV/chlorine disinfection.

Low-pressure (LP) UV treatment after chlorine disinfection was associated with enhanced formation of trichloronitromethane (TCNM), a halonitromethane disinfection by-product (DBP), due to the chlorination of tryptophan. Evidence was found that the concentration of TCNM from tryptophan increased quickly to the maximum for the first instance. Moreover, the increase of TCNM under UV exceeded 10 times than under dark. Then, it was found to have an obvious decrease in the formation of TCNM, even finally hardly disappear. In order to elucidate reasons for this phenomenon, the effects of light intensity, initial tryptophan concentration, free chlorine concentration, pH, and tert-butanol (TBA) on the formation of TCNM were investigated under UV/chlorine treatment. Finally, the effects of tryptophan on the formation of TCNM and the direct photodegradation of TCNM under LP UV irradiation were studied for analyzing the possible pathways of TCNM formation from amino acid. Since amino acids are very common in water sources, further research into chemical oxidation of these species by LP UV and chlorine is recommended. It can help us to find the precursors of TCNM formation and reduce the risk of TCNM formation for drinking water and wastewater utilities.

Phosphorus removal by in situ generated Fe(II): Efficacy, kinetics and mechanism.

The application of in situ electrochemical generation of ferrous (Fe(II)) ions for phosphorus (P) removal in wastewater treatment was investigated with attention to the efficacy, kinetics and mechanism. At concentrations typical of municipal wastewater, P could be removed by in situ Fe(II) with removal efficiency higher than achieved on addition of FeSO4 and close to that of FeCl3 under both anoxic and oxic conditions. The generation of alkalinity due to water electrolysis at the cathode created much higher pH conditions compared to FeSO4 dosing thereby resulting in very different pathways of Fe solid phase formation and associated P removal mechanisms. The remarkably similar dependence of P removal on accumulated Fe for all investigated currents, initial P concentrations and DO conditions indicated that kinetic aspects did not play a role in P removal during in situ Fe(II) dosing. Thermodynamic modelling was undertaken to investigate possible solid phase formation pathways under anoxic conditions and these insights were extended to oxic conditions. The exclusive formation of ferrous hydroxide during anoxic in situ Fe(II) dosing implied that P removal occurred via coprecipitation and adsorption. Under oxic conditions, the high pH conditions would have resulted in rapid Fe(II) oxidation and formation of ferric oxyhydroxides with associated coprecipitation and adsorption effecting P removal in a similar pattern to that observed under anoxic conditions. In situ Fe(II) dosing represents a versatile option for chemical P removal with the precise control of Fe dosage to optimize FeP forms for possible P recovery.

Comprehensive determination of macrolide antibiotics, their synthesis intermediates and transformation products in wastewater effluents and ambient waters by liquid chromatography-tandem mass spectrometry.

Macrolide antibiotics are a prominent group of emerging contaminants frequently found in wastewater effluents and wastewater-impacted aquatic environments. In this work, a novel analytical method for simultaneous determination of parent macrolide antibiotics (azithromycin, erythromycin, clarithromycin and roxithromycin), along with their synthesis intermediates, byproducts, metabolites and transformation products in wastewater and surface water was developed and validated. Samples were enriched using solid-phase extraction on Oasis HLB cartridges and analyzed by reversed-phase liquid chromatography coupled to electrospray ionization tandem mass spectrometry. The target macrolide compounds were separated on an ACE C18 PFP column and detected using multiple reaction monitoring in positive ionization polarity. The optimized method, which included an additional extract clean-up on strong anion-exchange cartridges (SAX), resulted in high recoveries and accuracies, low matrix effects and improved chromatographic separation of the target compounds, even in highly complex matrices, such as raw wastewater. The developed method was applied to the analysis of macrolide compounds in wastewater and river water samples from Croatia. In addition to parent antibiotics, several previously unreported macrolide transformation products and/or synthesis intermediates were detected in municipal wastewater, some of them reaching µg/L levels. Moreover, extremely high concentrations of macrolides up to mg/L level were found in pharmaceutical industry effluents, indicating possible importance of this source to the total loads into ambient waters. The results revealed a significant contribution of synthesis intermediates and transformation products to the overall mass balance of macrolides in the aquatic environment.

Agglomeration potential of TiO2 in synthetic leachates made from the fly ash of different incinerated wastes.

Material flow studies have shown that a large fraction of the engineered nanoparticles used in products end up in municipal waste. In many countries, this municipal waste is incinerated before landfilling. However, the behavior of engineered nanoparticles (ENPs) in the leachates of incinerated wastes has not been investigated so far. In this study, TiO2 ENPs were spiked into synthetic landfill leachates made from different types of fly ash from three waste incineration plants. The synthetic leachates were prepared by standard protocols and two types of modified procedures with much higher dilution ratios that resulted in reduced ionic strength. The pH of the synthetic leachates was adjusted in a wide range (i.e. pH 3 to 11) to understand the effects of pH on agglomeration. The experimental results indicated that agglomeration of TiO2 in the synthetic landfill leachate simultaneously depend on ionic strength, ionic composition and pH. However, when the ionic strength was high, the effects of the other two factors were masked. The zeta potential of the particles was directly related to the size of the TiO2 agglomerates formed. The samples with an absolute zeta potential value < 10 mV were less stable, with the size of TiO2 agglomerates in excess of 1500 nm. It can be deduced from this study that TiO2 ENPs deposited in the landfill may be favored to form agglomerates and ultimately settle from the water percolating through the landfill and thus remain in the landfill.

Determination of natural and synthetic glucocorticoids in effluent of sewage treatment plants using ultrahigh performance liquid chromatography-tandem mass spectrometry.

A sensitive and comprehensive analytical method for glucocorticoids (GCs) in water samples was developed and applied to effluent of sewage treatment plants (STPs). In the present study, totally 10 natural and synthetic GCs, including cortisol, betamethasone valerate, clobetasol propionate, clobetasone butyrate, difluprednate, betamethasone, dexamethasone, betamethasone dipropionate, methylprednisolone, and prednisolone, were targeted. Analytes were extracted and concentrated using an OASIS HLB solid phase extraction cartridge. Chromatographic separation and quantification were achieved using an ultrahigh performance liquid chromatograph coupled with a tandem mass spectrometer (UHPLC-MS/MS). Method detection limits were 0.05 to 0.89 ng/L, which were 1-2 orders of magnitude more sensitive than in the previous reports. Cortisol was detected in more than half of (27 out of 50) analyzed effluent samples at concentrations in the range of ND-1.36 ng/L, indicating continuous discharge of natural GC via STP effluent. On the other hand, dexamethasone + betamethasone, prednisolone, betamethasone valerate, and clobetasol propionate were detected in 25, 8, 20, and 9 samples among 50 effluent samples, respectively, suggesting not extreme but significant administration of synthetic GCs.

Identification of precursors and mechanisms of tobacco-specific nitrosamine formation in water during chloramination.

We report here that tobacco-specific nitrosamines (TSNAs) are produced from specific tobacco alkaloids during water chloramination. To identify the specific precursors for the formation of specific TSNAs in drinking water, we have developed a solid-phase extraction-liquid chromatography-tandem mass spectrometry (SPE-LC-MS/MS) method for simultaneous determination of five TSNAs and three tobacco alkaloids. Using this method, we detected nicotine (NIC) at 15.1 ng/L in a source water. Chloramination of this source water resulted in the formation of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) (0.05 ng/L) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) (0.2 ng/L) along with the reduction of NIC to 1.1 ng/L, suggesting that NNK and NNAL were formed from NIC. To confirm that tobacco alkaloids are the precursors of TSNAs, we chloraminated water-leaching samples of tobacco from three brands of cigarettes and found that the formation of TSNAs coincides with the reduction of the alkaloids. Chloramination of individual alkaloids confirms that NNK and NNAL are produced from NIC, N-nitrosonornicotine (NNN) from nornicotine (NOR), and N-nitrosoanabasine (NAB) from anabasine (ANA). Furthermore, we have identified specific intermediates of these reactions and proposed potential pathways of formation of TSNAs from specific alkaloids. These results confirm that NNK and NNAL are the disinfection byproducts (DBPs) resulting from NIC in raw water.

Cationic gemini surfactants with cleavable spacer: chemical hydrolysis, biodegradation, and toxicity.

The paper describes synthesis and characterization of a new type of cationic gemini surfactant, which has dodecyl tails and a spacer that contains an ester bond. The nomenclature used to describe the structure is 12Q2OCO1Q12, with Q being a quaternary ammonium group and the numbers indicating the number of methylene or methyl groups. Due to the close proximity to the two quaternary ammonium groups, the ester bond is very stable on the acid side and very labile already at slightly alkaline conditions. The hydrolysis products are two single chain surfactants (i.e. 12Q2OH and 12Q1COOH) which are less surface active than the intact gemini surfactant. 12Q2OCO1Q12 was found to be readily biodegradable, i.e. it gave more than 60% biodegradation after 28 days. This is interesting because similar gemini surfactants but with ester bonds in the tails instead of the spacer, have previously been found not to be readily biodegradable. The gemini surfactant was found to be toxic to aquatic organisms (ErC50 value of 0.27 mg/l), although less toxic than the two hydrolysis products.

Enhanced formation of disinfection byproducts in shale gas wastewater-impacted drinking water supplies.

The disposal and leaks of hydraulic fracturing wastewater (HFW) to the environment pose human health risks. Since HFW is typically characterized by elevated salinity, concerns have been raised whether the high bromide and iodide in HFW may promote the formation of disinfection byproducts (DBPs) and alter their speciation to more toxic brominated and iodinated analogues. This study evaluated the minimum volume percentage of two Marcellus Shale and one Fayetteville Shale HFWs diluted by fresh water collected from the Ohio and Allegheny Rivers that would generate and/or alter the formation and speciation of DBPs following chlorination, chloramination, and ozonation treatments of the blended solutions. During chlorination, dilutions as low as 0.01% HFW altered the speciation toward formation of brominated and iodinated trihalomethanes (THMs) and brominated haloacetonitriles (HANs), and dilutions as low as 0.03% increased the overall formation of both compound classes. The increase in bromide concentration associated with 0.01-0.03% contribution of Marcellus HFW (a range of 70-200 µg/L for HFW with bromide = 600 mg/L) mimics the increased bromide levels observed in western Pennsylvanian surface waters following the Marcellus Shale gas production boom. Chloramination reduced HAN and regulated THM formation; however, iodinated trihalomethane formation was observed at lower pH. For municipal wastewater-impacted river water, the presence of 0.1% HFW increased the formation of N-nitrosodimethylamine (NDMA) during chloramination, particularly for the high iodide (54 ppm) Fayetteville Shale HFW. Finally, ozonation of 0.01-0.03% HFW-impacted river water resulted in significant increases in bromate formation. The results suggest that total elimination of HFW discharge and/or installation of halide-specific removal techniques in centralized brine treatment facilities may be a better strategy to mitigate impacts on downstream drinking water treatment plants than altering disinfection strategies. The potential formation of multiple DBPs in drinking water utilities in areas of shale gas development requires comprehensive monitoring plans beyond the common regulated DBPs.

Impact of UV/H2O2 pre-oxidation on the formation of haloacetamides and other nitrogenous disinfection byproducts during chlorination.

Haloacetamides (HAcAms), an emerging class of nitrogen-based disinfection byproducts (N-DBPs) of health concern in drinking water, have been found in drinking waters at µg/L levels. However, there is a limited understanding about the formation, speciation, and control of halogenated HAcAms. Higher ultraviolet (UV) doses and UV advanced oxidation (UV/H2O2) processes (AOPs) are under consideration for the treatment of trace organic pollutants. The objective of this study was to examine the potential of pretreatment with UV irradiation, H2O2 oxidation, and a UV/H2O2 AOP for minimizing the formation of HAcAms, as well as other emerging N-DBPs, during postchlorination. We investigated changes in HAcAm formation and speciation attributed to UV, H2O2 or UV/H2O2 followed by the application of free chlorine to quench any excess hydrogen peroxide and to provide residual disinfection. The results showed that low-pressure UV irradiation alone (19.5-585 mJ/cm(2)) and H2O2 preoxidation alone (2-20 mg/L) did not significantly change total HAcAm formation during subsequent chlorination. However, H2O2 preoxidation alone resulted in diiodoacetamide formation in two iodide-containing waters and increased bromine utilization. Alternatively, UV/H2O2 preoxidation using UV (585 mJ/cm(2)) and H2O2 (10 mg/L) doses typically employed for trace contaminant removal controlled the formation of HAcAms and several other N-DBPs in drinking water.

Review of advances in the thin layer chromatography of pesticides: 2010-2012.

Techniques and applications of thin layer chromatography (planar chromatography) for the separation, detection, qualitative and quantitative determination, and preparative isolation of pesticides and their metabolites and some related pollutants are reviewed for the period from November 1, 2010 to November 1, 2012. Analyses are described for a variety of samples types and pesticide classes. In addition to references on residue analysis, studies such as pesticide structure - retention relationships, identification and characterization of natural and synthesized pesticides, metabolism, degradation, mobility, lipophilicity, and mechanism of action are covered.

Occurrences of nitrosamines in chlorinated and chloraminated drinking water in three representative cities, China.

An investigation of the occurrence of nine nitrosamines in drinking water following different water treatment processes was conducted using samples from seven drinking water treatment plants in three cities and tap waters in one city in China. The total nitrosamine levels ranged from not detected (n.d.) to 43.45 ng/L. The species and concentrations of the nine nitrosamines varied with disinfection methods and source waters. N-nitrosodimethylamine (NDMA), which is the nitrosamines of greatest concern, was identified in raw water, disinfecting water, finished water and tap water samples, ranging from 0.8 to 21.6, 0.12 to 24.2, n.d. to 8.8, and n.d. to 13.3 ng/L, respectively. Chloramination alone produced the most significant amounts of NDMA, while ozonation followed by chloramination led to moderately reduced levels. Additionally, chlorination produced relatively less NDMA, while low pressure ultraviolet radiation followed by chlorination could also significantly reduce them. Total organic carbon is one of the most important factors influencing nitrosamines formation in disinfecting water. In contrast, the addition of chlorine following any other disinfection was found to increase the formation of the other eight species of nitrosamines. The three nitrosamines recommended for monitoring by the US EPA were detected in the tap water samples, but most were present at levels below those that pose a risk to human health. Nevertheless, the occurrence and concentration of nitrosamines regulated in the Drinking Water Contaminant Candidate List could cause some potential human effects and therefore warrant attention.

Mechanism of perchlorate formation on boron-doped diamond film anodes.

This research investigated the mechanism of perchlorate (ClO(4)(-)) formation from chlorate (ClO(3)(-)) on boron-doped diamond (BDD) film anodes by use of a rotating disk electrode reactor. Rates of ClO(4)(-) formation were determined as functions of the electrode potential (2.29-2.70 V/standard hydrogen electrode, SHE) and temperature (10-40 °C). At all applied potentials and a ClO(3)(-) concentration of 1 mM, ClO(4)(-) production rates were zeroth-order with respect to ClO(4)(-) concentration. Experimental and density functional theory (DFT) results indicate that ClO(3)(-) oxidation proceeds via a combination of direct electron transfer and hydroxyl radical oxidation with a measured apparent activation energy of 6.9 ± 1.8 kJ·mol(-1) at a potential of 2.60 V/SHE. DFT simulations indicate that the ClO(4)(-) formation mechanism involves direct oxidation of ClO(3)(-) at the BDD surface to form ClO(3)(•), which becomes activationless at potentials > 0.76 V/SHE. Perchloric acid is then formed via the activationless homogeneous reaction between ClO(3)(•) and OH(•) in the diffuse layer next to the BDD surface. DFT simulations also indicate that the reduction of ClO(3)(•) can occur at radical sites on the BDD surface to form ClO(3)(-) and ClO(2), which limits the overall rate of ClO(4)(-) formation.

NDMA formation kinetics from three pharmaceuticals in four water matrices.

N, N-nitrosodimethylamine (NDMA) is an emerging disinfection by-product (DBP) that has been widely detected in many drinking water systems and commonly associated with the chloramine disinfection process. Some amine-based pharmaceuticals have been demonstrated to form NDMA during chloramination, but studies regarding the reaction kinetics are largely lacking. This study investigates the NDMA formation kinetics from ranitidine, chlorphenamine, and doxylamine under practical chloramine disinfection conditions. The formation profile was monitored in both lab-grade water and real water matrices, and a statistical model is proposed to describe and predict the NDMA formation from selected pharmaceuticals in various water matrices. The results indicate the significant impact of water matrix components and reaction time on the NDMA formation from selected pharmaceuticals, and provide fresh insights on the estimation of ultimate NDMA formation potential from pharmaceutical precursors.

Assessment of the generation of chlorinated byproducts upon Fenton-like oxidation of chlorophenols at different conditions.

Homogeneous Fenton-like (H(2)O(2)/Fe(3+)) oxidation proved to be highly efficient in the degradation of monochlorophenols but some important issues need to be considered depending on the operating conditions. When using the stoichiometric amount of H(2)O(2) and a dose of Fe(3+) in the range of 10-20mg/L, complete breakdown of 4-CP up to CO(2) and short-chain acids was achieved. Nevertheless, when substoichiometric amounts of H(2)O(2) or lower concentrations of iron were used, significant differences between the TOC measured and the calculated from the identified species were found. These differences were attributed to condensation byproducts, including chlorinated species, formed by oxidative coupling reactions. PCBs, dioxins and dichlorodiphenyl ethers were identified. A solid residue was also formed consisting mainly in carbon, oxygen and chlorine including also Fe. The occurrence of these highly toxic species must be carefully considered in the application of Fenton oxidation to wastewaters containing chlorophenols. The possibility of reducing costs by lowering the H(2)O(2) dose below the stoichiometric one needs to take this into account.

Formation of 2'-hydroxy-2,3',4,5'-tetrabromodipheyl ether (2'-HO-BDE68) from 2,4-dibromophenol in aqueous solution under simulated sunlight irradiation.

Hydroxylated polybrominated diphenyl ethers (HO-PBDEs) have received significant attention due to their toxicities and universal presence in the environmental matrices. However, their origins are not fully understood. We explored the feasibility of the generation of HO-PBDEs through photochemical processes from bromophenol, a commonly detected pollutant with anthropogenic source in freshwater and natural source in the marine environment. The results showed that when 2,4-dibromophenol (2,4-diBP) was irradiated in aquatic solutions under simulated sunlight, significant amounts of 2'-hydroxy-2,3',4,5'-tetrabromodipheyl ether (2'-HO-BDE68) were rapidly formed as the dimeric product of 2,4-diBP. The formation of 2'-HO-BDE68 intensified with the increase of light intensity and with the initial concentration increase of 2,4-diBP, whereas it weakened with an increase in pH. Moreover, Fe(III) and fulvic acid played important roles in the formation of 2'-HO-BDE68. This study provides important insight into a possible source of HO-PBDEs from bromophenols in natural aquatic systems through photochemical approaches.

Impact of UV disinfection combined with chlorination/chloramination on the formation of halonitromethanes and haloacetonitriles in drinking water.

The application of UV disinfection in water treatment is increasing due to both its effectiveness against protozoan pathogens, and the perception that its lack of chemical inputs would minimize disinfection byproduct formation. However, previous research has indicated that treatment of nitrate-containing drinking waters with polychromatic medium pressure (MP), but not monochromatic (254 nm) low pressure (LP), UV lamps followed by chlorination could promote chloropicrin formation. To better understand this phenomenon, conditions promoting the formation of the full suite of chlorinated halonitromethanes and haloacetonitriles were studied. MP UV/postchlorination of authentic filter effluent waters increased chloropicrin formation up to an order of magnitude above the 0.19 µg/L median level in the U.S. EPA's Information Collection Rule database, even at disinfection-level fluences (<300 mJ/cm(2)) and nitrate/nitrite concentrations (1.0 mg/L-N) relevant to drinking waters. Formation was up to 2.5 times higher for postchlorination than for postchloramination. Experiments indicated that the nitrating agent, NO(2)(•), generated during nitrate photolysis, was primarily responsible for halonitromethane promotion. LP UV treatment up to 1500 mJ/cm(2) did not enhance halonitromethane formation. Although MP UV/postchloramination enhanced dichloroacetonitrile formation with Sigma-Aldrich humic acid, formation was not significant in field waters. Prechlorination/MP UV nearly doubled chloropicrin formation compared to MP UV/postchlorination, but effects on haloacetonitrile formation were not significant.

Generation and analysis of mixed chlorinated/brominated homologs of the halogenated natural product heptachloro-1'-methyl-1,2'-bipyrrole.

The 2,3,3',4,4',5,5'-heptachloro-1'-methyl-1,2'-bipyrrole (Q1, MBP-79) and further halogenated 1'-methyl-1,2'-bipyrroles (MBPs) are a class of marine natural products repeatedly detected in seafood and marine mammals from all over the world. Only Q1 is currently commercially available as reference standard and the full synthesis of mixed brominated-chlorinated compound is rather complicated. For this reason, synthetic Q1 (240 mg) was transferred into bromine-containing MBPs by UV-irradiation in the presence of bromine. Bromine, which rapidly vanished from the solutions, was renewed during the reaction in order to generate higher amounts of Br-containing MBPs. A total of ∼150 mg Q1 was transferred after ∼10 min irradiation with high amounts of Br(2) to give 30.5mg BrCl(6)-MBPs along with lower proportions of Br(2)Cl(5)-, Br(3)Cl(4)-, Br(4)Cl(3)- and traces of Br(5)Cl(2)-MBPs. Longer UV-irradiation in the presence of Br(2) even allowed for the detection of Br(6)Cl-MBPs and traces of Br(7)-MBP. However, this reaction also provided some unknown by-products. A sample stored in the dark and later in in-door light (no UV irradiation) also eliminated Q1 after 76 d in favour of heptahalogenated MBPs with up to three bromine substituents. The irradiation products were separated on silica, and fractions containing only Q1 and BrCl(6)-MBPs were then further fractionated by non-aqueous RP-HPLC. A pure isolate of the major BrCl(6)-MBP (∼1.5mg) was characterized by GC/MS and (13)C NMR to be 2-bromo-3,3',4,4',5,5'-hexachloro-1-methyl-1,2'-bipyrrole (Br-MBP-75). Partial GC enantioseparation of the axially chiral Br-MBP-75 was achieved on a ß-PMCD column. A full enantioseparation was managed by enantioselective HPLC using a NUCLEOCEL DELTA S column. Low amounts of pure BrCl(6)-MBP enantiomers could be trapped.