Spiked Surface Water Samples Research Articles

Dendrimer Coated Silica as a Sorbent for Dispersive Solid-Phase Extraction of Select Non-Steroidal Anti-Inflammatory Drugs from Water.

Non-steroidal anti-inflammatory drugs (NSAIDs) have been recognized as a potentially serious threat to the natural environment. NSAIDs are popular painkillers, and the main pathway for them to reach natural water is via discharge from wastewater and sewage treatment plants. In order to monitor contamination caused by these drugs, as well as their impact on the environment, a new material based on Silica Gel 60, functionalized with a dendrimeric copolymer of methylamine and 1,4-butanediol diglycidyl ether (named MA-BDDE), was prepared. Initial physicochemical characterization of the MA-BDDE material was carried out using ATR FT-IR spectroscopy as well as solid-state carbon-13 NMR spectroscopy. Its effectiveness at NSAID extraction was evaluated by the application of five select drugs in dispersive solid-phase extraction (dSPE): aspirin, ketoprofen, naproxen, diclofenac and ibuprofen. This was followed by their simultaneous determination using the HPLC-UV/Vis system demonstrating good sensitivity, with limits of detection values within the 63-265 ng mL-1 range. A comparison of the sorption capacity of each pharmaceutical with unmodified base silica showed an at least tenfold increase in capacity after modification. Initial MA-BDDE application in a quick, low-waste extraction procedure of those select NSAIDs from spiked surface water samples yielded promising results for its use as a sorbent, as recovery values of analytes adsorbed from various samples were found to exceed 72%.

Electrochemical Determination of Enrofloxacin Using an Electrode Composed of Graphite Nanosheets Fabricated by Expansion in Dimethyl Sulfoxide

A sensor based on graphite nanosheets was fabricated through the electrochemical expansion of a graphite electrode in dimethyl sulfoxide for the sensitive electrochemical determination of enrofloxacin. The modified electrode surface exhibited a distinctive structure of nanoplates, characterized by layer thickness ranging from a few nanometers to ten nanometers. The developed electrode displayed notable electrochemical properties, including a faster charge transfer rate and a larger electrochemically active surface area, which was 1.3 times greater compared to the unmodified electrode. As a result, the sensor improved square wave voltammetric signals for enrofloxacin, exhibiting a 2.4-fold enhancement compared to the unmodified electrode. By optimizing the experimental parameters such as electrode fabrication conditions, pH of analytical solution, and adsorption time for enrofloxacin, the sensor demonstrated good reproducibility and a strong linear correlation over two ranges of enrofloxacin concentrations from 0.05–0.15 μM and 0.1–20 μM. The limit of detection was determined to be 0.002 μM. The sensor was successfully employed for the determination of enrofloxacin in spiked surface water samples before and after treating enrofloxacin by a photocatalytic method. The obtained results exhibited consistency with those obtained using a liquid chromatography-tandem mass spectrometry reference method, and a high recovery rate of 105.5% further confirmed the reliability of the proposed method for enrofloxacin detection.

Hybrid nanomaterial-based indirect electrochemical sensing of glyphosate in surface water: a promising approach for environmental monitoring.

Glyphosate (GLY), a widely utilized pesticide, poses a significant threat to human health even at minute concentrations. In this study, we propose an innovative electrochemical sensor for the indirect detection of GLY in surface water samples. The sensor incorporates a nanohybrid material composed of multi-layer graphene decorated with gold nanoparticles (AuNPs), synthesized in a single-step electrochemical process. To ensure portability and on-site measurements, the sensor is developed on a screen-printed electrode, chosen for its integration and miniaturization capabilities. The proposed sensor demonstrates remarkable sensitivity and selectivity for GLY detection in surface water samples, with an exceptional limit of detection (LOD) of 0.03 parts per billion (ppb) in both buffer and surface water matrices. Moreover, it exhibits a remarkably high sensitivity of 0.15 μA ppb-1. This electrochemical sensor offers a promising approach for accurate GLY monitoring, addressing the urgent need for reliable pesticide detection in environmental samples. The proposed sensor showed high selectivity towards GLY, when analysed in the presence of other pesticides such as phosmet, chlorpyrifos and glufosinate-ammonium. The recovery percentages of GLY from spiked surface water samples were between 93.8 and 98.9%. The study's broader implications extend to revolutionizing the way environmental chemistry addresses pesticide contamination, water quality assessment, and sustainable management of environmental pollutants. By pushing the boundaries of detection capabilities and offering practical solutions, this research contributes to the advancement of knowledge and practices that are essential for preserving and protecting our environment.

Lab-In-Syringe with Bead Injection Coupled Online to High-Performance Liquid Chromatography as Versatile Tool for Determination of Nonsteroidal Anti-Inflammatory Drugs in Surface Waters

We report on the hyphenation of the modern flow techniques Lab-In-Syringe and Lab-On-Valve for automated sample preparation coupled online with high-performance liquid chromatography. Adopting the bead injection concept on the Lab-On-Valve platform, the on-demand, renewable, solid-phase extraction of five nonsteroidal anti-inflammatory drugs, namely ketoprofen, naproxen, flurbiprofen, diclofenac, and ibuprofen, was carried out as a proof-of-concept. In-syringe mixing of the sample with buffer and standards allowed straightforward pre-load sample modification for the preconcentration of large sample volumes. Packing of ca. 4.4 mg microSPE columns from Oasis HLB® sorbent slurry was performed for each sample analysis using a simple microcolumn adapted to the Lab-On-Valve manifold to achieve low backpressure during loading. Eluted analytes were injected into online coupled HPLC with subsequent separation on a Symmetry C18 column in isocratic mode. The optimized method was highly reproducible, with RSD values of 3.2% to 7.6% on 20 µg L−1 level. Linearity was confirmed up to 200 µg L−1 and LOD values were between 0.06 and 1.98 µg L−1. Recovery factors between 91 and 109% were obtained in the analysis of spiked surface water samples.

Development of a microfluidic membraneless vaporization flow system for trace analysis of arsenic.

A new design of a membraneless vaporization (MBL-VP) unit coupled with a specific flow system is presented for the determination of arsenic at trace levels using a hydride generation process. The MBL-VP unit contains two concentric conical reservoirs, with the outer cone selected as the donor reservoir. The volume of the outer donor reservoir is thereby greater than the acceptor volume, necessary for holding sufficient sample and reagents for the generation of arsine gas by reaction between As(iii) and sodium borohydride under acidic conditions. The arsine gas diffuses into the narrow headspace and is absorbed by an aliquot of 150 μL of mercuric chloride acceptor solution. The resulting reaction produces hydronium ions which is monitored by the absorbance change at 530 nm of the methyl orange indicator added in the acceptor solution. To decrease the detection limit, the aspiration and removal of the donor plug, comprising the sample, borohydride and acid, into and out of the donor cone are repeated several times, while the acceptor solution is kept unchanged. As a result, analysis of arsenic was achieved in the range of 10 to 100 μg L-1 with a detection limit of 8 μg L-1. Application to surface water was investigated. Percent recoveries of spiked surface water samples were in the range of 94-110%. For comparison of total arsenic (As(iii) and As(v)), the results obtained from the developed method are not statistically different from the ICP-OES method.

A Polydimethylsiloxane Rod Extraction-Based Method for the Determination of Pharmaceuticals and Triclosan by Liquid Chromatography in Water Samples.

A new analytical method for the determination of naproxen, ketoprofen, diclofenac, carbamazepine, and triclosan (TCS) in water samples by liquid chromatography is developed and validated. The method is based on the extraction of the analytes by a polydimethylsiloxane (PDMS) rod. The different parameters affecting extraction, such as the addition of salt, pH, initial volume, extraction and elution times and elution solvent, as well as the application of sonication, are studied. The results showed that the detection limits are all in the 0.1-0.3 µg L-1 range except for carbamazepine (6 µg L-1) with relative standard deviations in the range of 0.4%-9.7%. The method developed, which was validated by analysing spiked surface water samples at 10, 25 and 75 µg L-1 gave recoveries of between 84.8% and 111.2%. In the case of carbamazepine, a recovery of 99.1% was obtained at 75 µg L-1. The main advantage of the developed method is that allows high performance liquid chromatography-diode array detection, which is widely available in non-specialised laboratories, to be applied for pharmaceuticals and TCS determination in surface waters after performing a preconcentration/clean-up step with PDMS rods as it has been shown by analysing real water samples.

Calixarene/carbon nanotubes based screen printed sensors for potentiometric determination of gentamicin sulphate in pharmaceutical preparations and spiked surface water samples

Sensitive disposable sensors have been introduced for potentiometric determination of gentamicin sulphate (GNS) based on multi-walled carbon nanotubes–polyvinyl chloride (MWNTs–PVC) composite in presence of calixarene as a molecular recognition element. The proposed sensors showed remarkable selectivity and sensitivity in the GNS concentration range from 10−7 to 10−2molL−1 with Nernstian slope 30.5±0.4mVdecade−1 and detection limit of 7.5×10−8molL−1. Modification with carbon nanotubes improved the sensors performance was through promotion of the electron-transfer processes and enhancing the stability of potential reading, response time, and shelf lifetime of sensors. The proposed method has been applied for the potentiometric assay of GNS in different dosage forms and spiked surface water samples with average recoveries agreeable with the reported official method.

Electrodeposition of Porous Polyaniline Coating on an Etching Stainless Steel Wire as a Fiber for Solid-Phase Microextraction of Triclosan and Chlorophenols in Water Samples

A novel polyaniline (PANI) coating doped with perchlorate ions was prepared on a stainless steel (SS) wire by a three-electrode system. Before electrodeposition, the SS wire was etched by hydrofluoric acid to enhance its surface roughness. The prepared PANI-coated fiber was used for solid-phase microextraction (SPME) of 2-chlorophenol (2-CP), 2,4-dichlorophenol (2,4-DCP) and triclosan (TCS) in water samples followed by high-performance chromatography with UV detection (HPLC-UV). The extraction procedure was optimized. The proposed SPME-HPLC-UV method provided a wide linear range. The limits of detection were 0.006 ng/mL for 2-CP, 0.005 ng/mL for 2,4-DCP and 0.04 ng/mL for TCS, respectively. It was successfully applied to the analysis of spiked surface water samples with the recoveries from 99.6% to 109%.

Determination of glyphosate residues in Hungarian water samples by immunoassay

An enzyme-linked immunosorbent assay (ELISA) for the detection of glyphosate was investigated for assay performance characteristics and was applied for determination of glyphosate contamination levels in selected surface and ground water resources in Hungary in 2010 and 2011. Advantages of the method include its simplicity (no laborious extraction) and specificity (cross-reactivity is below 0.1% for related compounds, e.g. aminomethyl-phosphonic acid, glufosinate). On the basis of our experiments, the practical limit of detection (LOD) ranged between 0.05 and 0.12ng/ml. The standard curve was of sigmoid (logistic) characteristics, and it co-occurred with curves obtained for spiked surface water samples. Matrix effects were observed in tap water, possibly due to chlorination and/or heavy metal ions, e.g. copper and zinc. The method was applied for the analysis of 42 surface and ground water samples collected from Békés county in Hungary at 14 sampling sites in 2010 and 18 surface water samples collected from the Danube River and Lake Velencei in Hungary at 12 sampling sites in 2011. Exceedingly high glyphosate levels (nearly 1ng/ml) were measured in 5 samples, and significant concentrations were determined in 16 cases (0.54–0.76ng/ml) in 2010, while practically no contamination was found in 2011. The great contrast between the two sampling regimes is explained by differing agricultural locations, natural precipitation and, to a greater extent, catchment area characteristics, resulting in varying leaching or run-off of glyphosate to surface waters.

Analysis of DDT Isomers with Enzyme-Linked Immunosorbent Assay and Optical Immunosensor Based on Rat Monoclonal Antibodies as Biological Recognition Elements

New rat monoclonal antibodies (mAbs) for DDT [1,1,1 -trichloro-2,2-bis (4-chlorophenyl) ethane], namely DDT 7C12, DDT 1C1, and DDT 1B2, were developed, characterized, and applied in ELISA both in coating antigen and in enzyme-tracer format. The latter used horseradish peroxidase (HRP) or glucose oxidase as enzymes. The lowest concentration of p,p'-DDT was determined with mAb DDT 7C12 and DDT-hapten HRP, with a test midpoint (IC50) of 0.5 +/- 0.2 microg/L (n=10) in 40 mM PBS (phosphate-buffered saline). The mouse anti-rat immunoglobulin lambda-light chain mAb LA1B12 was used as capture mAb. The best IC50 for o,p'-DDT in 40 mM PBS was 1.0 +/- 0.3 microg/L (n=12) and was obtained with mAb DDT 1C1 and DDT-hapten HRP, whereas mAb DDT 1B2 was very selective for p,p'-DDT with an IC50 of 4.2 + 1.6 microg/L (in 40 mM PBS, n=9). An optical immunosensor was optimized and applied for the analysis of DDT (or DDT equivalents). This immunosensor consists of a bench-top optical readout device and disposable sensor chips, which include the fluidic system. Evanescent field excitation and emission of the fluorophore Oyster-645 was used. An IC50 for p,p'-DDT [in 5% (v/v) isopropanol in 40 mM PBS] of 4 microg/L was obtained using DDT 7C12-Oyster-645. ELISA and immunosensor were used for the analysis of p,p'-DDT in unspiked and spiked surface water samples. Within the working ranges of these immunotechniques, recoveries ranged from 80 to 120%.

Determination of tetracyclines in surface water and milk by the magnesium hydroxide coprecipitation method

A simple coprecipitation method was developed for the determination of tetracyclines (TCs) in surface water and milk by high-performance liquid chromatography with diode-array detection (HPLC–DAD). Magnesium ion was added into the surface water or the acetonitrile (MeCN) extract of milk. After alkalinization, magnesium hydroxide precipitates which had been formed can be separated from the matrix solution easily by centrifuging and then a dissolution step was performed by adding a small amount of acid. The final solution could be introduced directly into HPLC system for the determination of the analytes. Under optimal conditions, recoveries for the analysis of spiked surface water samples ranged from 83.6% to 95.1% with relative standard deviation of 2.0–5.5%. For milk samples, relative recoveries were 95.9–104.6% with relative standard deviation of 3.4–6.7%. The enrichment factors ranged from 41.5 to 48.1 for 10 mL water samples, and from 3.6 to 4.4 for 1 mL MeCN extracts of milk. Limits of detection ranged from 0.13 to 0.51 ng/mL, and from 3.0 to 8.5 ng/g for four TCs in surface water and milk samples, respectively.

A novel fluorinated polyaniline-based solid-phase microextraction coupled with gas chromatography for quantitative determination of polychlorinated biphenyls in water samples

Novel polyaniline (PANI) electrodeposited in the presence of fluorinated organic acid was applied as a new conductive polymer-based solid-phase microextraction (SPME) fiber candidate. Polychlorinated biphenyls (PCBs) were selected as representative compounds. Improved temperature resistance (<500 °C) and satisfactory extraction efficiency were obtained by introduction of fluorinated organic acid. Extraction efficiency of novel PANI for PCBs was superior to common PANI (synthesized in sulfuric acid) and polythiophene, and comparable to commercial 30 μm PDMS but with thinner stationary, i.e. 10 μm. Quantitative determination of trace PCBs in water samples was carried out using this novel SPME fiber, coupling with selective gas chromatography–microelectron capture detector (GC–μECD). The proposed method provided a linear range of approximately three orders. The detection limits were 0.05 ng L −1 for PCB 138, 153 and 180, and 0.1 ng L −1 for PCB 28, 52 and 101, respectively. The method was successfully applied to the analysis of spiked surface water samples with the recoveries from 83.0 to 110.7%.

Pesticide residue determination in surface waters by stir bar sorptive extraction and liquid chromatography/tandem mass spectrometry

In this stir bar sorptive extraction (SBSE) method, 16 pesticides were extracted from surface water samples by sorption onto 1 mm polydimethylsiloxane layer coated on a 10-mm-length stir bar magnet. After liquid desorption of the analytes with 1 ml of methanol, the detection was performed on a liquid chromatography-tandem mass spectrometry with a triple quadrupole (QqQ) analyzer using selected reaction monitoring mode via electrospray ionization. Parameters affecting SBSE operation, including sample volume, salt addition, extraction time, stirring rate, and desorption conditions, have been evaluated. The optimized SBSE method required two 50 ml aliquots of surface water samples, one aliquot was added of 30% NaCl and stirred at 900 rpm during 1 h for testing five pesticides with log K(o/w) < 3, and the other aliquot was directly extracted following the same procedure for the rest of the pesticides with log K(o/w) > 3. The method was validated in spiked surface water samples at limits of quantifications (LOQs) and ten times the LOQs showing recoveries <62%, and the LOQs reached were from 0.03 microg l(-1) for diazinon to 3 microg l(-1) for simazine. The proposed methodology was applied to the determination of these compounds in samples from Albufera Lake and surrounding channels, showing that SBSE is a powerful tool for routine control analysis of pesticide residues in surface water.

Coagulation/chlorination of surface water: A comparison between chitosan and metal salts

Coagulation and subsequent chlorination are typically used for surface water treatment in order to produce potable water. Chitosan, a linear cationic polymer of high molecular weight, has recently been proposed for application in drinking water treatment as potential alternative to metal species based coagulants. However, due to its nature some organic matter may be released during coagulation step, thus increasing the concentration of disinfection by-products as well as the toxicity of finished water. In the present paper the efficiency of chitosan and conventional coagulants (aluminium sulphate and ferric chloride) was compared in terms of turbidity and natural organic matter (NOM) removal, as well as acute toxicity on Daphnia magna of coagulated and coagulated/chlorinated surface water. The coagulation experiments were carried out by jar test using low TOC and high alkalinity surface water. Turbidity and NOM removal, as well as toxicity were investigated (i) under actual conditions, (ii) for different pH (5, 6, 7) and (iii) in humic acid (HA) spiked surface water samples. All coagulants decreased toxicity on D. magna from 100% to 0% immobilization. However, the addition of humic acids affected final toxicity in different ways according to coagulant type and dose. Moreover, the chlorination step after coagulation increased toxicity too according to the coagulant type as follows: chitosan > ferric chloride > aluminium sulphate.

Method Validation for the Simultaneous Determination of Fecal Sterols in Surface Waters by Gas Chromatography-Mass Spectrometry

Besides microbiological methods, fecal pollution of surface waters is estimated by gas chromatographic (GC) determination of sterols present in human and animal sewage effluents. The most frequently used biomarkers for the evaluation of contamination levels include coprostanol, cholesterol, dihydrocholesterol, stigmasterol, beta-sitosterol, and stigmastanol. Although several GC techniques are used to measure these compounds in aquatic systems, the analytical performance of GC-mass spectrometric (MS) determination of these sterols has not been systematically characterized. Therefore, the aim of this work is to validate a simple and rapid GC-MS method for the simultaneous analysis of six sterols, considering all parameters and requirements defined by Good Laboratory Practice. Following liquid-liquid extraction of spiked surface water samples, the extracts are silylated and analyzed by GC-MS. The method is evaluated for linearity and limits of detection and quantitation, as well as for precision, extraction efficiency, and stability. The assay is linear up to 160 ng; the limits of detection and quantitation are 5-10 ng and 20 ng, respectively. The within- and between-day precision ranged from 1% to 9% and 1% to 16%, respectively. The extraction efficiency was 65-80%. The stability studies indicate that the sterols in surface water samples begin to degrade after 24 h of refrigerated storage. However, three freeze/thaw cycles could be performed without their decomposition. The method is applied to the analysis of surface water and wastewater samples. The technical advantages make this GC-MS analysis suitable for routine environmental monitoring of fecal pollution in aquatic systems.

An enzyme flow immunoassay that uses beta-galactosidase as the label and a cellobiose dehydrogenase biosensor as the label detector.

The aim was to develop a fast generic enzyme flow immunoassay (EFIA) using a beta-galactosidase (beta-GAL) label in combination with colorimetric detection as well as with a new amperometric biosensor as the label detector. The amperometric biosensor was previously developed within the group for the determination of diphenols in surface water samples. Antigen (Ag, analyte), tracer (Ag*, antigen labeled with beta-GAL), and antibody (Ab) were incubated off-line. After the equilibrium was reached, the sample was introduced into the flow system. The antibody complexes, AgAb and Ag*Ab, were trapped in a protein G column while the free unbound tracer was eluted and detected by an amperometric biosensor downstream after substrate reaction. The enzyme label beta-GAL converted the substrate 4-aminophenyl-beta-D-galactopyranoside (4-APG) into 4-aminophenol (4-AP), which subsequently was detected by a cellobiose dehydrogenase (CDH) modified solid graphite electrode. 4-AP was first oxidized at the electrode surface at +300 mV vs Ag/AgCl, and the formed 4-imino quinone (4-IQ) was reduced back to 4-AP by the CDH in the presence of cellobiose. By combining the EFIA with the CDH biosensor, the overall signal of one tracer molecule is amplified at two occasions, i.e., one enzyme label converts the substrate into many 4-AP molecules, and second these are further amplified by the CDH biosensor. The optimum conditions for the EFIA in terms of the molar ratio between tracer and beta-GAL, temperature, flow rate, etc., was investigated with colorimetric detection, using 2-nitrophenyl-beta-D-galactopyranoside (2-NPG) as the beta-GAL substrate. The performance of both the colorimetric and CDH biosensor detection was investigated and both methods were applied for determination of the model compound atrazine in spiked surface water samples. Detection limits of 0.056 +/- 0.008 and 0.038 +/- 0.007 microg L(-1) and IC50 values of 2.04 +/- 0.294 and 0.42 +/- 0.08 microg L(-1) were obtained for colorimetric and CDH detection, respectively. Matrix effects were less pronounced with the CDH biosensor than with colorimetric detection.

The role of capacity factor in method development for solid-phase extraction of phenolic compounds. II

Recently, a simple method was developed for the determination of capacity factors of phenolic compounds on solid-phase extraction cartridges [ J. Chromatogr. A, 693 (1995) 217]. In the present paper the capacity factors determined by this method are used to predict recoveries of phenolic compounds in solid-phase extraction at three different sample volumes. The values are compared with those of recovery tests from both model solutions and spiked surface water samples. Based on calibration data the minimum sample concentrations which can be determined by the SPE procedure are also calculated from the capacity factors.

On-line coupling of solid-phase extraction and gas chromatography with atomic emission detection for analysis of trace pollutants in aqueous samples

An on-line, solid-phase extraction gas chromatography atomic-emission detection (SPE-GC-AED) system has been set up using an on-column interface to transfer 100 μl of desorbing solvent to the GC part of the system. Analytical characteristics such as recovery, precision and linearity of calibration plots were comparable with those of the off-line combination of SPE-GC-AED using organophosphorus pesticides as test compounds. The fully on-line set-up causes a marked improvement in detection because of the quantitative transfer of the analytes from the SPE module to the GC: detection limits are as low as 5–20 ng l−1 for the analysis of 10 ml raw and spiked surface water samples using the phosphorus channel. Detection levels can be further enhanced by processing up to 100 ml samples. The integrated analytical system is robust. The potential of the on-line set up has been demonstrated for the analysis of surface water and waste water.