Fortified Tap Water Research Articles

Voltammetric Detection of Irbesartan by Molecularly Imprinted Polymer (MIP)-Modified Screen-Printed Electrodes

Irbesartan is a drug used to treat hypertension and high blood pressure. Recent studies associated sartans with several forms of cancer, making removing this class of substances from the environment a high priority. The EU has categorized drugs as emerging pollutants, and they can be more potent than other substances because they were designed to operate at low concentrations. Thus, effective and sensitive methods of determining Irbesartan selectively and accurately in environmental samples are necessary. MIPs have already been used to remove pollutants from complex matrixes, so they were also chosen for this work. In particular, a polyacrylate-based MIP was used to functionalize the graphite working electrode of screen-printed cells (SPCs), aiming to develop a voltammetric method for Irbesartan sensing. The MIP composition and the experimental conditions for the electrochemical determination were optimized through a Design of Experiments (DoE) approach. The whole analysis was replicated with different SPCs obtaining similar results, which highlight the good reproducibility potential. MIP-based electrodes were also applied to determine Irbesartan in fortified tap water samples, obtaining high recovery percentages. Given the good results, the electrochemical method based on MIP-modified screen-printed electrodes is promising for quantifying Irbesartan at a trace level.

Aptamer-functionalized metal-organic framework-based electrospun nanofibrous composite coating fiber for specific recognition of ultratrace microcystin in water

A novel aptamer@AuNPs@UiO-66-NH2 electrospun nanofibrous coating fiber for specific recognition of microcystin-LR (MC-LR) was proposed by using electrospinning, metal-organic frameworks (MOF) seed growth and AuNPs bridging aptamer strategies. Characterization of morphology, structure and stability of the obtained affinity nanofibrous coating fiber were investigated. High loading of MOFs and aptamers on the nanofibrous fiber were achieved and successfully applied for accurate identification of MC-LR by solid-phase microextraction (SPME) coupled with LC-MS. Highly specific recognition of MC-LR with little interference of analogs was achieved with extremely low LOD (0.004 ng/mL), good precision (CV% < 11.0%) and low relative error (RE% = −1.5% to −10.0%), which was rather better than that of the traditional SPME or SPE protocols. Satisfactory recoveries of MC-LR were obtained in the range of 92.0–96.8% (n = 3) in fortified tap water, raw pond water and river water samples. This work revealed an attractive alternative access to specific recognition and super-sensitive analysis of MC-LR in water.

Facile synthesis of halloysite-bentonite clay/magnesite nanocomposite and its application for the removal of chromium ions: Adsorption and precipitation process

Here we report the synthesis of halloysite-bentonite clay/magnesite nanocomposite, using ball milling and calcination. It was identified that the synthesized nanocomposite enjoys the synergistic properties of both materials, i.e. clays and magnesite, and hence was assessed in terms of chromium ions removal from real tannery wastewater. To identify the optimum conditions for chromium ions removal the one factor-at-a-time (OFAT) method was applied in the design of the batch experiments. The examined parameters include mixing time, dosage, concentration, and pH, while state-of-art analytical techniques were used. Specifically, to identify the morphological properties and the elemental composition of the synthesized nanocomposite, before and after it reacted with the chromium ions, HR-SEM-EDS was used. XRD was used to identify mineralogical compositions, while BET was used to determine surface areas. ICP-MS and multi-parameter probe were employed for water quality analyses. The removal of chromium ions, post the adsorption process, was confirmed using HR-SEM-EDS. The optimum conditions for chromium ions removal were identified as 60 min contract, 0.5 g of dosage at 0.5 g: 500 mL S: L ratio, and 300 mg L−1 chromium ions concentration. The reaction was observed to be independent of pH (1–10). At optimum conditions, the nanocomposite practically removed chromium ions from all examined water matrices, i.e. real tannery wastewater, fortified tap water, groundwater, mine water, and synthetic solution. The adsorption capacity was observed to be 199 mg g−1. Regarding the regression analysis, the adsorption kinetics seem to follow the pseudo-second-order (PSO) than the pseudo-first order (PFO) model. In addition, the adsorption data better fitted the Langmuir than the Freundlich adsorption isotherm. In a nutshell, the synthesized nanocomposite was found to be very promising for chromium ions removal from wastewater and possibly for other contaminants, such as heavy metals, which will be examined in future works of our group.

Determination of Carbendazim by an Ionic Liquid-Modified Carbon Paste Electrode

ABSTRACTA new method for the electroanalytical determination of carbendazim is reported using a novel ionic liquid-based carbon paste electrode. 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and 1-butyl-1-methylpyrrolidinium bis(trifluoromethyl-sulfonyl)imide were used as additives in the paste for electrode fabrication. The electrodes were characterized by cyclic voltammetry of the couple and scanning electron microscopy. The carbon paste electrode containing 19% 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide was selected for the electrochemical determination of carbendazim by differential pulse adsorptive stripping voltammetry. The influence of electrolyte pH, accumulation potential and time, and the presence of selected pesticides on electrochemical behavior of carbendazim were characterized. The optimal conditions for differential pulse adsorptive stripping voltammetry of carbendazim were determined to be a pH 5.0 Britton–Robinson buffer, an accumulation potential of −0.05 V, an accumulation time of 120 s, a start potential of −0.10 V vs. the reference; an end potential of +1.30 V, and a scan rate of 0.050 V s−1. The linear dynamic range of the method was from 0.010 to 0.247 mg L−1 with a correlation coefficient of 0.9995. The recovery was 104.1% in fortified tap water, demonstrating its suitability for the analysis of water.

Development of an amperometric biosensor based on a novel conducting copolymer for detection of anti-dementia drugs

In this study, a new amperometric biosensor was developed for the detection of the anti-dementia drugs fortified with tap water. For this purpose, electrocopolymerization of 5,6-bis(octyloxy)-4,7-di(thiophen-2-yl)benzo[c][1,2,5]oxadiazole(BODT) with (2-(((9H-fluoren-9-yl)methoxy)carbonylamino) acetic acid (FMOC) on graphite electrode was successfully achieved and used as an immobilization matrix. Acetylcholinesterase (AChE) and choline oxidase (ChO) enzyme couple was immobilized on copolymer coated graphite electrode via covalent binding with the help of carbodiimide chemistry. Changes in the responses of the proposed biosensor based on AChE inhibition were recorded using acetylcholine as the substrate. The bi-enzymatic biosensor based on conducting copolymer showed good linear detection range between 0.01 and 12.0mM and a detection limit (LOD) of 0.014mM to acetylcholine. Surface and electrochemical characterization were performed via Scanning Electron Microscopy (SEM) and cyclic voltammetry (CV) techniques. Moreover, the design biosensor system was tested for the detection of neostigmine and donepezil as pharmaceuticals in fortified tap water samples. Very low detection limits of 0.027μg/L donepezil and 0.559μg/L neostigmine were achieved. The analysis of spiked tap water proved the biosensor capability to be used. The results were found to be in good agreement with the ones determined by HPLC/DAD technique.

An acetylcholinesterase biosensor based on a conducting polymer using multiwalled carbon nanotubes for amperometric detection of organophosphorous pesticides

A novel amperometric biosensor based on a conducting polymer using multi walled carbon nanotube modified electrode was developed for detection of organophosphorus pesticides. Acetylcholinesterase (AChE) was successfully immobilized by covalent linkage on the modified graphite electrode. Carbon nanotubes were functionalized by electrochemical treatment. A conducting polymer; poly(4-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)benzenamine) (poly(SNS-NH2)) was synthesized via electropolymerization to examine its matrix properties for biomolecule immobilization. This strategy enhanced electron transfer rate at a lower potential (+100mV vs. Ag reference) and catalyzed electrochemical oxidation of acetylthiocholine effectively. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), contact angle measurements and electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) techniques were used to monitor changes in surface morphologies and electrochemical characterizations. The proposed biosensor design offered a fast response time (6s), a wide linear range (0.05mM and 8.00mM) and a low detection limit (0.09mM) with a high sensitivity (24.16μAmM−1cm−2) for acetylthiocholine. The inhibition responses of paraoxon, parathion and chlorfenvinphos on the enzymatic activity of AChE were detected. The fabricated biosensor was tested for the detection of pesticides in fortified tap water samples. The results were found to be in good agreement with the ones determined by HPLC/DAD technique.

Gold nanorods for surface Plasmon resonance detection of mercury (II) in flow injection analysis

This article investigates the flow injection analysis of mercury (II) ions in tap water samples via surface Plasmon resonance detection. Quantitative analysis of mercury (II) is based on the chemical interaction of metallic mercury with gold nanorods immobilized on a glass substrate. A new flow cell design is presented with the ability to accommodate the detecting substrate in the sample compartment of commercial spectrometers. Two alternatives are here considered for mercury (II) detection, namely stop-flow and continuous flow injection analysis modes. The best limit of detection (2.4ngmL−1) was obtained with the continuous flow injection analysis approach. The accurate determination of mercury (II) ions in samples of unknown composition is demonstrated with a fortified tap water sample.

Voltammetric Behavior of Semicarbazide at Graphene Modified Electrode and Application to Detection

AbstractHerein voltammetric behaviors of semicarbazide (SEM) are investigated by employing a graphene modified working electrode, which displays attractive electroanalytical properties. In the acetate buffer solution of pH 4.00, there is a well‐defined oxidative peak of SEM, attributing to the irreversible and adsorption‐controlled electrode reaction with 2 electrons participation. The values of apparent heterogeneous electron transfer rate constant k′s with the redox are 0.0061 s−1 and 0.0009 s−1, respectively, for two scan rate section. After the experimental parameters, which influence the voltammetric responses of SEM, including supporting electrolyte, pH, accumulation time and accumulation potential, etc., are optimized, it is found that the anodic peak current of SEM is proportional to its concentration in the range of 4 ‐ 40 μmol/L with a detection limit of 1 μmol/L (S/N = 3). Then, an electrochemical method for detecting SEM quantitatively is developed successfully. The concentrations of SEM in fortified tap water samples are tested with satisfactory recovery, indicating that the novel method is strongly promising in the environmental monitoring application.

Transformation of the artificial sweetener acesulfame by UV light

The transformation of the artificial sweetener acesulfame by direct photolysis was investigated at various pH values, in different water types and at various concentration levels. Main photodegradation products of acesulfame were elucidated and analyzed both in laboratory experiments and in a full-scale waterworks using UV treatment for disinfection purposes. The degradation of acesulfame was found to be independent of the pH (range 5–11) and followed pseudo first order kinetics in a concentration range between 1μg∙L−1 and 10mg∙L−1. Calculated rate constants were in the range between 5.4·10−3s−1 and 7.4·10−3s−1. The main photodegradation products of acesulfame were separated by ion exchange chromatography and high performance liquid chromatography and were identified as hydroxylated acesulfame and iso-acesulfame by high resolution mass spectrometry and fragmentation experiments. In the case of iso-acesulfame an intramolecular rearrangement is assumed as the transformation product has a higher polarity and different product ions after MS fragmentation compared to acesulfame. Minor transformation products were identified as amidosulfonic acid and sulfate by comparison with analytical standards. The transformation pathway was found to be transferable to drinking water production as the identified transformation products were also detected to a similar extent in fortified tap water. In a Swiss full-scale waterworks acesulfame concentrations were reduced by approximately 30% and one of the main UV transformation products could be qualitatively detected.

Application of NaClO‐treated multiwalled carbon nanotubes as solid phase extraction sorbents for preconcentration of trace 2,4‐dichlorophenoxyacetic acid in aqueous samples

Multiwalled carbon nanotubes functionalized by oxidation of original multiwalled carbon nanotubes with NaClO were prepared and their application as solid phase extraction sorbent for 2,4-dichlorophenoxyacetic acid (2,4-D) was investigated systemically, and a new method was developed for the determination of trace 2,4-D in water samples based on extraction and preconcentration of 2,4-D with solid phase extraction columns packed with NaClO-treated multiwalled carbon nanotubes prior to its determination by HPLC. The optimum experimental parameters for preconcentration of 2,4-D, including the column activating conditions, the amount of the sorbent, pH of the sample, elution composition, and elution volume, were investigated. The results indicated 2,4-D could be quantitatively retained by 100 mg NaClO-treated multiwalled carbon nanotubes at pH 5, and then eluted completely with 10 mL 3:1 (v/v) methanol-ammonium acetate solution (0.3 mol/L). The detection limit of this method for 2,4-D was 0.15 μg/L, and the relative standard deviation was 2.3% for fortified tap water samples and 2.5% for fortified riverine water sample at the 10 μg/L level. The method was validated using fortified tap water and riverine water samples with known amount of 2,4-D at the 0.4, 10, and 30 μg/L levels, respectively.

Determination of seven commonly used organic UV filters in fresh and saline waters by liquid chromatography-tandem mass spectrometry

An analytical method for the simultaneous determination of seven of the most widely used organic UV filter compounds in tap and saline waters was developed and validated. Target compounds included oxybenzone, dioxybenzone, sulisobenzone, avobenzone, octocrylene, octinoxate, and padimate-O. Water samples were adjusted to pH 2 prior to solid-phase extraction (SPE) using Oasis HLB 500 mg cartridges. The detection and quantification were performed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) with positive electrospray ionization (ESI) using Multiple Reaction Monitoring mode (MRM). Calculated recoveries from fortified samples ranged from 74 to 109% with relative standard deviations of 6–25% for fortified tap water samples and from 71 to 111% with relative standard deviations 2–12% for fortified seawater samples, indicating acceptable method accuracy and precision (n = 5). Method reporting limits ranged from 0.5 to 25 ng L−1 for the seven compounds. Oxybenzone, avobenzone, octocrylene, octinoxate, and padimate-O were detected in seawater samples collected from Folly Beach, South Carolina in the summer of 2010, at concentrations ranging from 10 to 2013 ng L−1, demonstrating the ability of the developed method to measure target compounds in environmental samples. Oxybenzone and octocrylene were found in the highest concentrations, up to 2013 ng L−1 and 1409 ng L−1, respectively. Concentrations for avobenzone, octinoxate, and padimate-O ranged from 62–321 ng L−1, 30–264 ng L−1 and <1–111 ng L−1, respectively, in surface seawater samples (n= 4). Dioxybenzone and sulisobenzone were not detected in any samples from the four sites (method reporting limits 1 ng L−1). To our knowledge, this is the first study reporting sunscreen compounds in the coastal waters of the U.S.A.

Determination of sulfonylurea herbicides in water using solid-phase extraction followed by liquid chromatography with electrospray ion trap mass spectrometry

A method has been developed for confirmation and quantitation of ten sulfonylurea herbicides (nicosufuron, thifensulfuron-methyl, metsulfuron-methyl, sulfometuron-methyl, chlorsulfuron, ethametsulfuron-methyl, tribenuron, bensulfuron-methyl, pyrazosulfuron-ethyl and chlorimuron-ethyl) in water samples. Herbicides were extracted from water by off-line solid-phase extraction (SPE). Different types of absorbents were evaluated: silica-based ODS-C18 and two polymeric sorbents, Cleanert HXN and Oasis HLB. Analyte determination and quantitation was performed by liquid chromatography with electrospray mass spectrometry (LC-ESI-MS) instrumentation, equipped with ion trap mass filter. Confirmatory analysis was carried out by LC/MS/MS. MS data acquisition was performed by a single or two-ion extracted ion monitoring program. The ten herbicides were measured in fortified tap water. Average recoveries of the nine analytes (except for tribenuron) from water samples were in the range of 77–109%, and the RSD ranged from 0.3 to 14.5%. The limit of detections (LODs) varied from 6 to 34.8 ng/L.

Chemical, microbial and physical evaluation of commercial bottled waters in greater Houston area of Texas

Due to the increased demand and consumption of bottled water in the United States, there has been a growing concern about the quality of this product. Retail outlets sell local as well as imported bottled water to consumers. Three bottles for each of 35 different brands of bottled water were randomly collected from local grocery stores in the greater Houston area. Out of the 35 different brands, 16 were designated as spring water, 11 were purified and/or fortified tap water, 5 were carbonated water and 3 were distilled water. Chemical, microbial and physical properties of all samples were evaluated including pH, conductivity, bacteria counts, anion concentration, trace metal concentration, heavy metal and volatile organics concentration were determined in all samples. Inductively coupled plasma/mass spectrometry (ICPMS) was used for elemental analysis, gas chromatography with electron capture detector (GCECD) as well as gas chromatography mass spectrometry (GCMS) were used for analysis of volatile organics, ion chromatography (IC) and selective ion electrodes were used for the analysis of anions. Bacterial identification was performed using the Biolog software (Biolog, Inc., Hayward, Ca, USA). The results obtained were compared with guidelines of drinking water recommended by the International Bottled Water Association (IBWA), United States Food and Drug Administration (FDA), United States Environmental Protection Agency (EPA) and the World Health Organization (WHO) drinking water standard. The majority of the analyzed chemicals were below their respective drinking water standards for maximum admissible concentrations (MAC). Volatile organic chemicals were found to be below detection limits. Four of the 35 brands of the bottled water samples analyzed were found to be contaminated with bacteria.

Development of an Enzyme-Linked Immunosorbent Assay for the Pyrethroid Insecticide Cyhalothrin

A competitive enzyme-linked immunosorbent assay (ELISA) was developed for detection of the pyrethroid insecticide cyhalothrin. Three haptens with an amine or propanoic acid terminus were synthesized and then conjugated with bovine serum albumin to give immunogens. Eight polyclonal antisera produced by rabbits were screened for titers and affinity using three different coating antigens. The antiserum CWB-C had the highest affinity with cyhalothrin and a low affinity with fenvalerate, fenpropathrin, deltamethrin, and fluvalinate. The half-maximum inhibition concentration for cyhalothrin was 37.2 microg/L, and the limit of detection was 4.7 microg/L. The recoveries of different concentrations of cyhalothrin (0.1-2500 microg/L) from fortified tap water, well water, and wastewater samples as determined with the ELISA were 81-114%.

A new on‐line micellar‐enhanced photochemically‐induced fluorescence method for determination of phenylurea herbicide residues in water

A new flow injection analysis micellar-enhanced photochemically induced fluorescence (FIA-MEPIF) method was developed for the determination of four phenylurea herbicides, including isoproturon, neburon, linuron and diuron. On-line photoconversion under UV irradiation of these herbicides into strongly fluorescent photoproducts was performed in buffered aqueous solutions and in the presence of surfactants [sodium dodecyl sulphate (SDS) or cetyl trimethyl ammonium chloride (CTAC)] at micellar concentrations. The MEPIF and FIA parameters were optimized. The analytical figures of merit for the determination of the four herbicides were satisfactory, with concentration linear dynamic ranges over about one to two orders of magnitude, detection limits of 0.33-0.92 mg[sol ]L and relative standard deviations of 1.3-11%, according to the compound. Application to the analysis of fortified tap water samples yielded good recovery values (91-103%, according to the herbicide). Our results show that the on-line MEPIF-FIA method is simple, versatile, sensitive and can be easily applied to quantify pollutant residues in multiresidue systems.

Analysis of atrazine, terbutylazine and their N-dealkylated chloro and hydroxy metabolites by solid-phase extraction and gas chromatography–mass spectrometry and capillary electrophoresis–ultraviolet detection

Solid-phase extraction (SPE) with the styrene–divinylbenzene adsorbent LiChrolut EN was investigated for the extraction of the s-triazine herbicides atrazine and terbutylazine, their polar N-dealkylated degradation products deethylatrazine (DEA), deisopropylatrazine (DIA) and deethylterbutylazine (DET) and for the hydrophilic hydroxytriazine degradation products (HTDPs) hydroxyatrazine (HA), hydroxyterbutylazine (HT), deethylhydroxyatrazine (DEHA), deisopropylhydroxyatrazine (DIHA) and deethyldeisopropylhydroxyatrazine (ameline). The optimum pH value for the extraction of the HTDPs from fortified tap water at 2 μg/l is 3.0. Recovery values with 200 mg LiChrolut EN are >80% for HA, HT, DEHA and 30% for DIHA from 200 ml spiked tap and river water. Atrazine, terbutylazine, DEA, DIA and DET are quantitatively extracted by LiChrolut EN. The chlorotriazines are analyzed by GC–MS and the HTDPs by capillary zone electrophoresis (CZE) and micellar electrokinetic capillary chromatography (MECC) with an acetate buffer at pH 4.6 or a sodium borate–sodium dodecyl sulfate buffer at pH 9.3. The combined method of SPE enrichment and CE analysis allows the determination of HTDPs in the low μg/l range.