Determination of sucralose in foods by HPLC

A method for the determination of sucralose in various foods by RI-HPLC and ion chromatography with a pulsed amperometric detector (PAD-IC) was developed. Chopped or homogenized samples were packed into cellulose tubing with 0.01 mol/L hydrochloric acid containing 10% sodium chloride and were dialyzed against 0.01 mol/L hydrochloric acid for 24 hours. The dialyzate was passed through a Bond Elut ENV cartridge, and the cartridge was washed with 0.2 mol/L NaOH and water. Sucralose was eluted from the cartridge with methanol. The extract was taken to dryness in an evaporator and the residue was re-dissolved in water. Sucralose was separated on an Inertsil ODS-3V column with a mobile phase of acetonitrile-water (15:85) and an RI detector. It was also determined on a CarboPak PA1 column with a mobile phase of 100 mmol/L NaOH-75 mmol/L CH3COONa, using a PAD detector. The recoveries of sucralose from various kinds of foods spiked at 50 micrograms/g and 200 micrograms/g ranged from 88-105%. The detection limit in samples was 10 micrograms/g for RI-HPLC and 1 microgram/g for PAD-IC.     

Determination of sucralose in foods by liquid chromatography/tandem mass spectrometry

A simple method for the determination of sucralose in various foods using liquid chromatography-electrospray ionization tandem mass spectrometry (LC/MS/MS) was developed. Sucralose was extracted with water or methanol, and the extract was cleaned up on a C18 cartridge, and diluted with water for injection into the LC/MS/MS. The LC separation was performed with a reversed-phase gradient on an ODS column, and the mass spectral acquisition was done in the negative ion mode by applying selected reaction monitoring (SRM). The recoveries of sucralose from various kinds of foods fortified at 100 micrograms/g and 5 micrograms/g were 88.1-96.7% and 92.7-98.5%, respectively. The lower limits of quantification were 0.5 microgram/g in beverage, low-malt beer, yogurt and chocolate and 2.5 micrograms/g in other foods. Forty-three commercial foods containing sucralose were analyzed by this method. Sucralose was detected in all samples at levels of 3.8-481 micrograms/g.     

Impact of treatment processes on the removal of perfluoroalkyl acids from the drinking water production chain

The behavior of polyfluoralkyl acids (PFAAs) from intake (raw source water) to finished drinking water was assessed by taking samples from influent and effluent of the several treatment steps used in a drinking water production chain. These consisted of intake, coagulation, rapid sand filtration, dune passage, aeration, rapid sand filtration, ozonation, pellet softening, granular activated carbon (GAC) filtration, slow sand filtration, and finished drinking water. In the intake water taken from the Lek canal (a tributary of the river Rhine), the most abundant PFAA were PFBA (perfluorobutanoic acid), PFBS (perfluorobutane sulfonate), PFOS (perfluorooctane sulfonate), and PFOA (perfluorooctanoic acid). During treatment, longer chain PFAA such as PFNA (perfluorononanoic acid) and PFOS were readily removed by the GAC treatment step and their GAC effluent concentrations were reduced to levels below the limits of quantitation (LOQ) (0.23 and 0.24 ng/L for PFOS and PFNA, respectively). However, more hydrophilic shorter chain PFAA (especially PFBA and PFBS) were not removed by GAC and their concentrations remained constant through treatment. A decreasing removal capacity of the GAC was observed with increasing carbon loading and with decreasing carbon chain length of the PFAAs. This study shows that none of the treatment steps, including softening processes, are effective for PFAA removal, except for GAC filtration. GAC can effectively remove certain PFAA from the drinking water cycle.The enrichment of branched PFOS and PFOA isomers relative to non branched isomers during GAC filtration was observed during treatment. The finished water contained 26 and 19 ng/L of PFBA and PFBS. Other PFAAs were present in concentrations below 4.2 ng/L The concentrations of PFAA observed in finished waters are no reason for concern for human health as margins to existing guidelines are sufficiently large.     

Occurrence of iodinated X-ray contrast media and their biotransformation products in the urban water cycle

A LC tandem MS method was developed for the simultaneous determination of four iodinated X-ray contrast media (ICM) and 46 ICM biotransformation products (TPs) in raw and treated wastewater, surface water, groundwater, and drinking water. Recoveries ranged from 70% to 130%, and limits of quantification (LOQ) varied between 1 ng/L and 3 ng/L for surface water, groundwater and drinking water, and between 10 ng/L and 30 ng/L for wastewater. In a conventional wastewater treatment plant, iohexol, iomeprol, and iopromide were transformed to >80%, while iopamidol was transformed to 35%. In total, 26 TPs were detected above their LOQ in WWTP effluents. A significant change in the pattern of ICM TPs was observed after bank filtration and groundwater infiltration under aerobic conditions. Predominately, these TPs are formed at the end of the microbial transformation pathways in batch experiments with soil and sediment. These polar ICM TPs, such as iohexol TP599, iomeprol TP643, iopromide TP701A, and iopromide TP643, were not or only partially removed during drinking water treatment. As a consequence, several ICM TPs were detected in drinking water, at concentration levels exceeding 100 ng/L, with a maximum of 500 ng/L for iomeprol TP687.     

Determination of sucralose in foods by anion-exchange chromatography and reverse-phase chromatography

Simple and rapid methods for the determination of sucralose in foods were developed using anion-exchange chromatography (AEC) with pulsed amperometric detection and reverse-phase HPLC with refractive index detection. Sucralose was extracted with water or methanol, and the extracted solution was cleaned up on a Sep-Pak C18 cartridge and a Sep-Pak Alumina N cartridge. The AEC separation was performed on a CarboPac PA1 column (4.0 mm i.d x 250 mm) using 100 mmol/L sodium hydroxide-50 mmol/L sodium acetate solution as the mobile phase at a flow rate of 1.0 mL/min. The recoveries of sucralose from foods were 80.6-102.0%, and quantitation limits from foods except chewing gum were 0.5 microgram/g (2 micrograms/g from chewing gum). The reverse-phase HPLC separation was performed on an Inertsil ODS-3V column (4.6 mm i.d x 150 mm) using methanol-water (25:75) as the mobile phase at a flow rate of 1.0 mL/min. The recoveries of sucralose from foods were 80.2-121.2%, and quantitation limits from foods except chewing gum were 5 micrograms/g (20 micrograms/g from chewing gum).     

Bromate in chlorinated drinking waters: occurrence and implications for future regulation

Bromate is a contaminant of commercially produced solutions of sodium hypochlorite used for disinfection of drinking water. However, no methodical approach has been carried out in U.S. drinking waters to determine the impact of such contamination on drinking water quality. This study utilized a recently developed method for quantitation of bromate down to 0.05 microg/L to determine the concentration of bromate present in finished waters that had been chlorinated using hypochlorite. Forty treatment plants throughout the United States using hypochlorite in the disinfection step were selected and the levels of bromate in the water both prior to and following the addition of hypochlorite were measured. The levels of bromate in the hypochlorite feedstock were also measured and together with the dosage information provided by the plants and the amount of free chlorine in the feedstock, it was possible to calculate the theoretical level of bromate that would be imparted to the water. A mass balance was performed to compare the level of bromate in finished drinking water samples to that found in the corresponding hypochlorite solution used for treatment. Additional confirmation of the source of elevated bromate levels was provided by monitoring for an increase in the level of chlorate, a co-contaminant of hypochlorite, atthe same point in the treatment plant where bromate was elevated. This study showed that bromate in hypochlorite-treated finished waters varies across the United States based on the source of the chemical feedstock, which can add as much as 3 microg/L bromate into drinking water. Although this is within the current negotiated industry standard that allows up to 50% of the maximum contaminant level (MCL) for bromate in drinking water to be contributed by hypochlorite, it would be a challenge to meet a tighter standard. Given that distribution costs encourage utilities to purchase chemical feedstocks from local suppliers, utilities in certain regions of the United States may be put at a distinct disadvantage if future lower regulations on bromate levels in finished drinking water are put into place. Moreover, with these contaminant levels it would be almost impossible to lower the maximum permissible contribution to bromate in finished water from hypochlorite to 10% of the MCL, which is the norm for other treatment chemicals. Until this issue is resolved, it will be difficult to justify a lowering of the bromate MCL from its current level of 10 to 5 microg/L or lower.     

Bacterial community structure in the drinking water microbiome is governed by filtration processes

The bacterial community structure of a drinking water microbiome was characterized over three seasons using 16S rRNA gene based pyrosequencing of samples obtained from source water (a mix of a groundwater and a surface water), different points in a drinking water plant operated to treat this source water, and in the associated drinking water distribution system. Even though the source water was shown to seed the drinking water microbiome, treatment process operations limit the source water's influence on the distribution system bacterial community. Rather, in this plant, filtration by dual media rapid sand filters played a primary role in shaping the distribution system bacterial community over seasonal time scales as the filters harbored a stable bacterial community that seeded the water treatment processes past filtration. Bacterial taxa that colonized the filter and sloughed off in the filter effluent were able to persist in the distribution system despite disinfection of finished water by chloramination and filter backwashing with chloraminated backwash water. Thus, filter colonization presents a possible ecological survival strategy for bacterial communities in drinking water systems, which presents an opportunity to control the drinking water microbiome by manipulating the filter microbial community. Grouping bacterial taxa based on their association with the filter helped to elucidate relationships between the abundance of bacterial groups and water quality parameters and showed that pH was the strongest regulator of the bacterial community in the sampled drinking water system.     

三氯蔗糖的安全性研究进展

三氯蔗糖是一种非营养合成甜味剂,目前已广泛应用于饮料、食品、医药等行业,为评价其使用的安全性,国内外相关学者对其急性和慢性毒性、致癌性、生殖毒性等方面进行了大量研究,就三氯蔗糖在体内的吸收代谢、毒性以及国内外批准使用情况等方面进行了综述。     

高效毛细管区带电泳-间接紫外法测定食品中三氯蔗糖

目的建立利用毛细管区带电泳-间接紫外法测定食品中三氯蔗糖的方法。方法样品用超纯水提取,离心所得的上清液直接进样,以未涂层熔融石英毛细管(50μm×60.2 cm)为分离柱,3 mmol/L 3,5-二硝基苯甲酸+10 mmol/L磷酸钠+12 mmol/L氢氧化钠(p H=12.58)+0.5 mmol/L十六烷基三甲基溴化铵为分离缓冲液;检测波长200 nm,分离电压-20 k V。采用校正峰面积外标法进行定量。结果方法检出限为10 mg/L,定量限为30 mg/L,线性范围为30~300 mg/L,线性相关系数r=0.999 1。低、中、高3个质量浓度(40、60及80 mg/L)的加标回收率分别为108.1%、102.6%、103.5%,相对标准偏差(RSD)分别为1.3%、1.3%及1.0%,方法精密度为2.0%。结论本研究样品前处理操作简单,20 min之内即可完成三氯蔗糖的含量分析(预清洗6 min,分离13 min),实现了与其结构相似但又同时存在于食品中蔗糖的分离,且试剂及样品消耗量少,适用于实验室对于食品中三氯蔗糖的检测。     

气相色谱-质谱联用法测定水中嗅味物质二甲基异茨醇

目的建立二甲基异茨醇在不同水样中的检测方法。方法采用气质联用法测定水质中二甲基异茨醇。结果 2-甲基异茨醇在0~40 ng/L的浓度范围内有良好的线性范围,线性相关系数大于等于0.999,检出限为5 ng/L,定量限为10 ng/L。在不同水样的基质下,3个不同梯度浓度的回收在82.3%~98.9%之间,相对偏差在0.68%~1.31%之间。结论该方法可准确测定生活饮用水、养殖用水、鱼虾解冻用水以及水产品加工废水中的嗅味物质2-甲基异茨醇。     

Stimulatory drugs of abuse in surface waters and their removal in a conventional drinking water treatment plant

The presence of psychoactive stimulatory drugs in raw waters used for drinking water production and in finished drinking water was evaluated in a Spanish drinking water treatment plant (DWTP). Contamination of the river basin which provides raw water to this DWTP was also studied. In surface waters, illicit drugs such as cocaine, benzoylecgonine (cocaine metabolite), amphetamine, methamphetamine, MDMA (ecstasy), and MDA were detected at mean concentrations ranging from 4 to 350 ng/L. Nicotine, caffeine, and their metabolites were also found at the microg/L level. The elimination of these compounds during drinking water treatment was investigated in a real waterworks. Amphetamine-type stimulants (except MDMA) were completely removed during prechlorination, flocculation, and sand filtration steps, yielding concentrations lowerthan their limits of detection (LODs). Further, ozone treatment was shown to be effective in partially eliminating caffeine (76%), while subsequent granulated activated carbon (GAC) filtration removed cocaine (100%), MDMA(88%), benzoylecgonine (72%), and cotinine (63%). Postchlorination achieved the complete elimination of cocaine and nicotine and only one parent compound (caffeine) and two metabolites (cotinine and benzoylecgonine) persisted throughout treatment although reductions of 90% for caffeine and benzoylecgonine and 74% for cotinine were obtained.     

Determination of sucralose in foods by HPLC using pre-column derivatization

The development of a sensitive pre-column derivatization high-performance liquid chromatography (HPLC) method for determination of sucralose is reported. Sucralose is converted into a strongly ultraviolet (UV)-absorbing derivative, possessing strong absorption at 260 nm, by treatment with p-nitrobenzoyl chloride (PNBCl). Homogenized samples were dialyzed and washed with a Bond Elut ENV cartridge, then the eluate was evaporated to dryness and the residue was derivatized. Subsequently, the sucralose derivative was purified with hexane-ethyl actate (9:1) in a silica cartridge, and then the sucralose derivative was eluted with acetone. HPLC was performed on a phenyl column, using acetonitrile-water (73:27) as a mobile phase with UV detection (260 nm). The calibration curve was linear in the range of 1 microgram/mL to 50 micrograms/mL of sucralose. The recoveries of sucralose from eight kinds of foods spiked at the levels of 0.20 and 0.05 g/kg of sucralose were more than 76.2% with SD values in the range from 0.90% to 4.31%. The quantitative limit of the developed method was 0.005 g/kg for sucralose in samples.     

Evaluation of perfluorooctane surfactants in a wastewater treatment system and in a commercial surface protection product

The origin and amount of perfluorooctane surfactants in wastewater treatment systems, and the transformation these compounds may undergo during treatment, were evaluated through measurement and experiment. Influent, effluent, and river water at the point of discharge for a 6-MGD wastewater treatment plant (WWTP) were screened for eight perfluorooctane surfactants. N-EtFOSAA was quantified in influent (5.1 +/- 0.8 ng/L), effluent (3.6 +/- 0.2 ng/ L), and river water samples (1.2 +/- 0.3 ng/L), while PFOS and PFOA were quantified in effluent (26 +/- 2.0 and 22 +/- 2.1 ng/L, respectively) and river water (23 +/- 1.5 and 8.7 +/- 0.8 ng/L, respectively). Signals for PFOS and PFOA were observed in influent samples, but exact quantitative determination could not be made due to low recoveries of these two compounds in field spike samples. Although the source of PFOS and PFOA observed in WWTP effluents is not clear, two hypotheses were examined: (1) the highly substituted perfluorooctane surfactants that constitute commercially available fabric protectors can be transformed to PFOS and PFOA during biological treatment in wastewater treatment systems, and (2) the end products themselves are directly introduced to WWTPs because they are present as residual in the commercial mixtures. Biotransformation experiments of 96 h were run to determine whether N-EtFOSE (a primary monomer used in 3M's polymer surface protection products) could be transformed to lesser-substituted perfluorooctane compounds in bioreactors amended with aerobic and anaerobic sludge from the sampled plant. At the end of the aerobic biotransformation experiment, N-EtFOSAA and PFOSulfinate were the only two metabolites formed and each accounted for 23 +/- 5.0% and 5.3 +/- 0.8% of the transformed parent on a molar basis, respectively. Transformation of N-EtFOSE was not observed under anaerobic conditions. A sample of a commercially available surface protection product from 1994 was analyzed and found to contain six of the targeted perfluorinated surfactants, including PFOS and PFOA. These findings suggest transformation of precursors within wastewater treatment is not an important source of these compounds compared to direct use and disposal of products containing the end products as residual amounts.     

Perfluorinated compounds in the environment and the blood of residents living near fluorochemical plants in Fuxin, China

A fluorochemical industrial park was built in 2004 in Fuxin, China, for the production of polytetrafluoroethylene (PTFE) and perfluorobutane sulfonate (PFBS). Yet little is known about the distribution of fluorochemicals in the environment and in people living in and around the park. In this study, environmental samples were collected from 22 sites in Fuxin to investigate the extent of perfluorinated compound (PFC) contamination in the environment around the park, and in drinking water from the public water supply system and groundwater in shallow aquifers from private wells near the park. Serum samples were also collected from nonoccupationally exposed residents living in Fuxin to determine the PFC load of local residents. As the dominant contaminant of eight target PFCs, the maximum concentrations of perfluorooctanoic acid (PFOA) in sediment and river water of the River Xi along the industrial park were 48 ng/g dry weight and 668 ng/L, respectively; the highest PFOA concentration in groundwater beneath the park was 524 ng/L; and the PFOA levels in drinking water from the public water supply system ranged between 1.3 and 2.7 ng/L. In human serum, PFOA had the geometric mean at 4.3 ng/mL, ranging from 0.02 to 93 ng/mL. This study serves to document what should be the beginning of a long-term surveillance effort to minimize potential exposure of residents living in Fuxin.     

Predicting atrazine levels in water utility intake water for MCL compliance

To protect human health, atrazine concentrations in finished municipal drinking water must not exceed a maximum contaminant level (MCL) of 3 microg/L, as determined by a specific monitoring regime mandated by the United States Environmental Protection Agency. Atrazine levels were monitored along tile-fed drainage ditches draining to a major drinking water source and used to predict MCL exceedance frequencies of intake and finished drinking water. Water samples were collected daily at eight monitoring sites located at the outlets of subbasins draining 298-19 341 ha (736-47 794 ac). Flow-weighted average (FWA) atrazine concentrations ranged from 0.9 to 9.8 microg/L, and were above 3 microg/L for the majority of sites, including the largest site, which represents water quality at the intake of the local municipal water treatment plant. However, a relatively low percentage of samples near the water utility intake exceeding 3 microg/L atrazine (10.4%) made this problem difficult to detect. In order to have a 95% probability of detecting any intake sample exceeding 3 microg/L atrazine in a drainage system exceeding 3 microg/L atrazine on a FWA basis, sampling frequency would need to be every 7 days or more often during the second quarter when the potentials for field atrazine losses and temporal variability of atrazine concentrations are highest.     

Organic micropollutants in rivers downstream of the megacity beijing: sources and mass fluxes in a large-scale wastewater irrigation system

The Haihe River System (HRS) drains the Chinese megacities Beijing and Tianjin, forming a large-scale irrigation system severely impacted by wastewater-borne pollution. The origin, temporal magnitudes, and annual mass fluxes of a wide range of pharmaceuticals, household chemicals, and pesticides were investigated in the HRS, which drains 70% of the wastewater discharged by 20 million people living in Beijing. Based on Chinese consumption statistics and our initial screening for 268 micropollutants using high-resolution mass spectrometry, 62 compounds were examined in space and time (2009-2010). The median concentrations ranged from 3 ng/L for metolachlor to 1100 ng/L for benzotriazole and sucralose. Concentrations of carbendazim, clarithromycin, diclofenac, and diuron exceed levels of ecotoxicological concern. Mass-flux analyses revealed that pharmaceuticals (5930 kg/year) and most household chemicals (5660 kg/year) originated from urban wastewaters, while the corrosion inhibitor benzotriazole entered the rivers through other pathways. Total pesticide residues amounted to 1550 kg/year. Per capita loads of pharmaceuticals in wastewater were lower than those in Europe, but are expected to increase in the near future. As 95% of the river water is diverted to irrigate agricultural soil, the loads of polar organic micropollutants transported with the water might pose a serious threat to food safety and groundwater quality.     

Polar pollutants entry into the water cycle by municipal wastewater: a European perspective

The effluents of eight municipal wastewater treatment plants (WWTP) in Western Europe were analyzed by liquid-chromatography-mass spectrometry for the occurrence of 36 polar pollutants, comprising household and industrial chemicals, pharmaceuticals, and personal care products. In a long-term study of the effluents of three WWTP over 10 months, sulfophenyl carboxylates and ethylene diamino tetraacetate (EDTA) were detected above 10 microg/L on average, while benzotriazoles, benzothiazole-2-sulfonate, diclofenac, and carbamazepine showed mean concentrations of 1-10 microg/L, followed by some flame retardants, naphthalene disulfonates, and personal care products in the range of 0.1-1 microg/L. Half of the determined compounds were not significantly removed in tertiary wastewater treatment. By dividing the effluent concentration of a compound by its relative removal in WWTP a water cycle spreading index (WCSI) was calculated for each compound. We propose that this index provides a measure for the potential of a polar compound to spread along a partially closed water cycle after discharge with municipal wastewater and to occur in raw waters used for drinking water production. Polar pollutants in surface water samples of different catchments showed increasing concentration for compounds with increasing WCSI.     

Quantifying diffuse and point inputs of perfluoroalkyl acids in a nonindustrial river catchment

Recently, the role of diffuse inputs of perfluoroalkyl acids (PFAAs) into surface waters has been investigated. It has been observed that river loads increased during rain and that street runoff contained considerable loads of PFAAs. This study aims at quantifying these diffuse inputs and identifying the initial sources in a small nonindustrial river catchment. The river was sampled in three distinct subcatchments (rural, urban, and wastewater treatment plant) at high temporal resolution during two rain events and samples were analyzed for perfluorocarboxylates and perfluorosulfonates. Additionally, rain, stormwater runoff, wastewater effluent, and drinking water were sampled. PFAA concentrations in river water were all low (e.g., < 10 ng/L for perfluorooctanoate, PFOA), but increased during rainfall. PFAA concentrations and water discharge data were integrated into a mass balance assessment that shows that 30-60% of PFAA loads can be attributed to diffuse inputs. Rain contributed 10-50% of the overall loads, mobilization of dry deposition and outdoor release of PFAA from products with 20-60%. We estimated that within a year 2.5-5 g of PFOA originating from rain and surface runoff are emitted into this small catchment (6 km(2), 12,500 persons).     

Analysis of pharmaceuticals in water by isotope dilution liquid chromatography/tandem mass spectrometry

A method has been developed for the trace analysis of 15 pharmaceuticals, four metabolites of pharmaceuticals, three potential endocrine disruptors, and one personal care product in various waters. The method employs solid-phase extraction (SPE) and liquid chromatography/tandem mass spectrometry (LC-MS/MS), using electrospray ionization (ESI) in both positive and negative modes. Unlike many previous LC-MS/MS methods, which suffer from matrix suppression, this method uses isotope dilution for each compound to correct for matrix suppression, as well as SPE losses and instrument variability. The method was tested in five matrices, and results indicate that the method is very robust. Matrix spike recoveries for all compounds were between 88 and 106% for wastewater influent, 85 and 108% for wastewater effluent, 72 and 105% for surface water impacted by wastewater, 96 and 113% for surface water, and 91 and 116% for drinking water. The method reporting limits for all compounds were between 0.25 and 1.0 ng/L, based on 500 mL of sample extracted and a final extract volume of 500 microL. Occurrence of the compounds in all five matrices is also reported.     

Occurrence of halogenated furanones in U.S. drinking waters

Chlorinated and brominated forms of MX (3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone) were detected in the disinfected waters of six pairs of U.S. drinking watertreatment plants, with MX as high as approximately 310 ng/L in finished water. The strength of this study is in its comparison between pairs of plants that drew water from the same or similar watersheds and treated the raw source water with two contrasting disinfection and/or treatment schemes. As expected, the brominated MX-analogues were produced in greater abundance than MX from raw source waters with high bromide concentrations. Disinfection of waters with free chlorine produced more MX-analogues than disinfection with monochloramine. Use of chloramines as the residual disinfectant appeared to stabilize MX-analogues once they were formed. Pretreatment with ozone and biologically active granular activated carbon minimized MX-analogue formation upon subsequent chlorination or chloramination, either because MX precursors were altered by ozone, removed by granular activated carbon, or degraded by biological filtration. Pretreatment with chlorine dioxide did not minimize MX-analogue formation. In plant effluent samples, MX and chloroform were positively correlated (molar R = 0.7, N = 6). Similar formation patterns of MX-analogues, trihalomethanes, and haloacetic acids in these water treatment plants suggest that the three classes of disinfection byproduct follow a common formation mechanism from natural organic matter and chlorine.