Cigarette filter as sorbent for on-line coupling of solid-phase extraction to high-performance liquid chromatography for determination of polycyclic aromatic hydrocarbons in water

An on-line solid-phase extraction (SPE) protocol using the cigarette filter as sorbent coupled with high-performance liquid chromatography (HPLC) was developed for simultaneous determination of trace naphthalene (NAPH), phenanthrene (PHEN), anthracene (ANT), fluoranthene (FLU), benzo(b)fluoranthene (BbF), benzo(k)fluoranthene (BkF), benzo(a)pyrene (BaP), and benzo(ghi)perylene (BghiP) in water samples. To on-line interface solid-phase extraction to HPLC, a preconcentration column packed with the cigarette filter was used to replace a conventional sample loop on the injector valve of the HPLC for on-line solid-phase extraction. The sample solution was loaded and the analytes were then preconcentrated onto the preconcentration column. The collected analytes were subsequently eluted with a mobile phase of methanol-water (95:5). HPLC with a photodiode array detector was used for their separation and detection. The detection limits (S/N = 3) for preconcentrating 42 mL of sample solution ranged from 0.9 to 58.6 ng L(-1) at a sample throughput of 2 samples h(-1). The enhancement factors were in the range of 409-1710. The developed method was applied to the determination of trace NAPH, PHEN, ANT, FLU, BbF, BkF, BaP and BghiP in local river water samples. The recoveries of PAHs spiked in real water samples ranged from 87 to 115%. The precisions for nine replicate measurements of a standard mixture (NAPH: 4.0 microg L(-1), PHEN: 0.40 microg L(-1), ANT: 0.40 microg L(-1), FLU: 2.0 microg L(-1), BbF: 1.6 microg L(-1), BkF: 2.0 microg L(-1), BaP: 2.0 microg L(-1), BghiP: 1.7 microg L(-1)) were in the range of 1.2-5.1%.     

Determination of cadmium in river water by electrothermal atomic absorption spectrometry after internal standardization-assisted rapid coprecipitation with lanthanum phosphate.

Cadmium ranging from 1 - 8 ng could be coprecipitated quantitatively with lanthanum phosphate at pH 5 - 6 from up to 200 mL of river water samples spiked with 5 microg of indium as an internal standard. Cadmium and indium coprecipitated were measured by using electrothermal atomic absorption spectrometry. The cadmium content in the original sample solution could be determined by internal standardization with indium. Since complete collection of the precipitate and strict adjustment of the volume of the final solution after coprecipitation are not required in this method, the precipitate could be collected by using decantation and centrifugation, and then dissolved with 1 mL of about 2.4 mol L(-1) nitric acid. The proposed method is simple and rapid, and enrichment close to 200-times can be attained; the detection limit (3sigma, n = 6) was 0.63 ng L(-1) in 200 mL of the sample solution.     

On-line complexation of zinc with 5-Br-PADAP and preconcentration using a knotted reactor for inductively coupled plasma atomic emission spectrometric determination in river water samples

An on-line zinc preconcentration and determination system implemented with inductively coupled plasma atomic emission spectrometry (ICP-AES) associated with flow injection (FI) was studied. The zinc was retained as zinc-2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Zn-(5-Br-PADAP)) complex at pH 9.2. The zinc complex was removed from the knotted reactor (KR) with 30% v/v nitric acid. An enrichment factor of 42 was obtained for the KR system with respect to ICP-AES using pneumatic nebulization. The detection limit for the preconcentration of 10 mL of aqueous solution was 0.09 microg/L. The precision for 10 replicate determinations at the 5 microg/L Zn level was 2.3% relative standard deviation (RSD), calculated with the peak heights obtained. The calibration graph using the preconcentration system for zinc was linear with a correlation coefficient of 0.9997 at levels near the detection limits up to at least 100 microg/L. The method was succesfully applied to the determination of zinc in river water samples.     

Determination of the antifouling agent zinc pyrithione in water samples by copper chelate formation and high-performance liquid chromatography-atmospheric pressure chemical ionisation mass spectrometry

Zinc pyrithione has recently been incorporated into antifouling paints as a booster biocide, which is slowly released into the water as the paint ages. In order to determine concentrations of zinc pyrithione (ZPT) in aqueous samples, a liquid chromatographic method has been developed. Since ZPT interacts with certain reversed-phase packing materials or stainless steel components of the HPLC system, the method uses transchelation of the ZPT into the stable copper(II) complex before analysis by liquid chromatography coupled to atmospheric pressure chemical ionisation mass spectrometry. ZPT was extracted as copper pyrithione using dichloromethane with adequate recovery (77% +/- 17%, n = 6) from 2-l water samples. The limit of detection was calculated to be 20 ng/l, using selected ion monitoring. The analysis of samples collected from various UK marinas showed no detectable concentrations to be present, whilst a laboratory-based study confirmed that this is probably due to the rapid photodegradation of ZPT in seawater.     

Capabilities of microbore columns coupled to inductively coupled plasma mass spectrometry in speciation of arsenic and selenium

The performance of microHPLC-microconcentric nebulizer-inductively coupled plasma-mass spectrometry (ICP-MS) coupling for the simultaneous determination of As(III), As(V), monomethylarsenic acid (MMA), dimethylarsinic acid (DMA), selenite (SeIV) and selenate (SeVI) in water was evaluated. The accurate reduction of the off-column dead volume, specially the capillary of the micronebulizer, as well as the optimization of chromatographic conditions led to the claimed advantages expected for microbore columns: a significant diminution of sample and solvent consumption without sacrificing sensitivity and the overall resolution in faster analysis time (less than 5 min). Detection limits are in the range 0.03-0.04 microg L(-1) for arsenic species and 0.35 microg L(-1) for selenium species. The developed method was validated by analysing different spiked environmental water samples. Linearity, tested up to 50 microg L(-1), showed correlation coefficients above 0.999 and no matrix effect for high saline water samples. Good accuracy and repeatability was obtained for spiked influent and effluent water treatment plant.     

Solid-phase extraction and field-amplified sample injection–capillary zone electrophoresis for the analysis of benzophenone UV filters in environmental water samples

A field-amplified sample injection–capillary zone electrophoresis (FASI-CZE) method for the analysis of benzophenone (BP) UV filters in environmental water samples was developed, allowing the separation of all compounds in less than 8 min. A 9- to 25-fold sensitivity enhancement was obtained with FASI-CZE, achieving limits of detection down to 21–59 μg/L for most of the analyzed BPs, with acceptable run-to-run and day-to-day precisions (relative standard deviations lower than 17 %). In order to remove water sample salinity and to enhance FASI sensitivity, an off-line solid-phase extraction (SPE) procedure using a Strata X polymeric reversed-phase sorbent was used and afforded recoveries up to 72–90 % for most BPs. With the combination of off-line SPE and FASI-CZE, limits of detection in the range 0.06–0.6 μg/L in a river water matrix, representing a 2,400- to 6,500-fold enhancement, were obtained. Method performance was evaluated by quantifying a blank river water sample spiked at 1 μg/L. For a 95 % confidence level, no statistical differences were observed between found concentrations and spiked concentrations (probability at the confidence level, p value, of 0.60), showing that the proposed off-line SPE-FASI-CZE method is suitable for the analysis of BP UV filters in environmental water samples at low microgram per liter levels. The method was successfully applied to the analysis of BPs in river water samples collected up- and downstream of industrialized and urban areas, and in some drinking water samples.     

Determination of glyoxal and methylglyoxal in environmental and biological matrices by stir bar sorptive extraction with in-situ derivatization

Stir bar sorptive extraction with in-situ derivatization using 2,3-diaminonaphthalene (DAN) followed by liquid desorption and high performance liquid chromatography with diode array detection (SBSE(DAN)in-situ-LD-HPLC-DAD) was developed for the determination of glyoxal (Gly) and methylglyoxal (MGly) in environmental and biological matrices. DAN proved very good specificity as in-situ derivatising agent for Gly and MGly in aqueous media, allowing the formation of adducts with remarkable sensitivity, selectivity and the absence of photodegradation. Assays performed on spiked (1.0 microg L(-1)) water samples, under convenient experimental conditions, yielded recoveries of 96.2+/-7.9% for Gly and 96.1+/-6.4% for MGly. The analytical performance showed good accuracy, suitable precision (<12.0%), low detection limits (15 ng L(-1) for Gly and 25 ng L(-1) for MGly adducts) and excellent linear dynamic ranges (r2>0.99) from 0.1 to 120.0 microg L(-1). By using the standard addition method, the application of the present method to tap and swimming-pool water, beer, yeast cells suspension and urine samples allowed very good performance at the trace level. The proposed methodology proved to be a feasible alternative for routine quality control analysis, showing to be easy to implement, reliable, sensitive and with a low sample volume requirement to monitor Gly and MGly in environmental and biological matrices.     

Multiwalled carbon nanotubes as adsorbents of solid-phase extraction for determination of polycyclic aromatic hydrocarbons in environmental waters coupled with high-performance liquid chromatography

Multiwalled carbon nanotubes (MWCNTs) were used as a novel kind of solid-phase extraction adsorbents in this work as well as an analytical method based on MWCNTs solid-phase extraction (SPE) combined with high-performance liquid chromatography (HPLC) was established for the determination of polycyclic aromatic hydrocarbons (PAHs), some of which belong to typical persistent organic pollutants (POPs) owing to their carcinogenicity and endocrine disrupting activity. Several conditions that probably affected the extraction efficiency including the eluent volume, sample flow rate, sample pH and the sample volume were optimized in detail. The characteristic data of analytical performance were determined to investigate the sensitivity and precision of the method, and the method was applied to the determination of PAHs in environmental water samples such as river water sample, tap water sample and wastewater sample from the constructed wetland effluent. The experimental results indicated that there were excellent linear relationship between peak area and the concentration of PAHs over the range of 0.04-100 microg L(-1), and the precisions (RSD) were 1.7-4.8% under the optimal conditions. The detection limits of proposed method for the studied PAHs were 0.005-0.058 microg L(-1) (S/N=3). The recoveries of PAHs spiked in environmental water samples ranged from 78.7 to 118.1%. It was concluded that MWCNTs packed cartridge coupled with HPLC was an excellent alternative for the routine analysis of PAHs at trace level.     

On-line preconcentration of pharmaceutical residues from large volume water samples using short reversed-phase monolithic cartridges coupled to LC-UV-ESI-MS

A simplified preconcentration method for a range of ultra-trace level pharmaceuticals in natural waters has been developed. Solid phase extraction was performed on-line using a micro-reversed-phase monolithic silica column, allowing for very rapid trace enrichment from large volume (500 ml) samples with minimal sample handling. Acceptable recoveries of >70% were obtained for the majority of compounds investigated and the monolithic columns could be washed and conditioned on-line with no sample carryover and used reproducibly for up to eight extractions each. The on-line SPE-LC-UV method was coupled to electrospray ionisation ion trap mass spectrometry (ESI-MS) to increase both selectivity and specificity. Detection limits were determined in spiked river and tap water samples and found to lie in the low ng/l region using sample volumes of 500 ml, loaded at a flow rate of 10 ml/min, and therefore, were suitable for ultra trace analysis.     

Multiwalled carbon nanotubes coated fibers for solid-phase microextraction of polybrominated diphenyl ethers in water and milk samples before gas chromatography with electron-capture detection

Determination of polybrominated diphenyl ethers (PBDEs) in environmental samples has raised great concerns due to the widespread use of PBDEs and their potential risk to humans. Solid-phase microextraction (SPME) is a fast, simple, cost-effective, and green sample preparation technique and is widely used for environmental analysis, but reports on the application of SPME for determination of PBDEs are very limited, and only a few publications dealing with commercial SPME fibers are available for extraction of PBDEs. Herein, we report a novel SPME method using multiwalled carbon nanotubes (MWCNTs) as the SPME fiber coating for gas chromatography with electron-capture detection (GC-ECD) of PBDEs in environmental samples. The MWCNTs coating gave much higher enhancement factors (616-1756) than poly (5% dibenzene-95% dimethylsiloxane) coating (139-384) and activated carbon coating (193-423). Thirty-minute extraction of 10 mL of sample solution using the MWCNTs coated fiber for GC-ECD determination yielded the limits of detection of 3.6-8.6 ng L(-1) and exhibited good linearity of the calibration functions (r(2)>0.995). The precision (RSD%, n=4) for peak area and retention time at the 500 ng L(-1) level was 6.9-8.8% and 0.6-0.9%, respectively. The developed method was successfully applied for the analysis of real samples including local river water, wastewater, and milk samples. The recovery of the PBDEs at 500 ng L(-1) spiked in these samples ranged from 90 to 119%. No PBDEs were detected in the river water and skimmed milk samples, whereas in the wastewater sample, 134-215 ng L(-1) of PBDEs were found. The PBDEs were detected in all whole fat milk samples, ranging from 13 to 484 ng L(-1). In a semiskimmed milk sample, only BDE-47 was found at 21 ng L(-1).     

Simplified method for determination of polycarbamate fungicide in water samples by liquid chromatography with tandem mass spectrometry following derivatization with dimethyl sulfate

A simple and sensitive analytical method for the determination of polycarbamate in water samples was developed. In this method, polycarbamate was cleaved under alkaline conditions and derivatized with dimethyl sulfate to methyl dimethyldithiocarbamate (DMDC-methyl) and dimethyl ethylenebisdithiocarbamate (EBDC-dimethyl). After the solid-phase extraction of the resulting methyl derivatives, they were measured by liquid chromatography with tandem mass spectrometry (LC-MS/MS), based on reversed-phase separation and MS/MS detection with positive atmospheric pressure chemical ionization. The absolute recoveries (mean+/-SD) all through the procedure from polycarbamate to DMDC-methyl and EBDC-dimethyl were 62.6+/-4.3 and 73.5+/-5.9%, respectively. The limits of detection and quantification of polycarbamate in the water samples were 0.061 and 0.20 microg/L in the form of DMDC-methyl, and 0.032 and 0.11 microg/L in the form of EBDC-dimethyl, respectively. The method was validated at levels of 0.25, 1.0, and 5.0 microg/L in the tap water and river water samples, and accuracy was achieved in the range of 94-109%. The proposed method can be applied to the determination of trace amounts of polycarbamate in environmental water samples.     

Differential determination of chromium(VI) and total chromium in natural waters using flow injection on-line separation and preconcentration electrothermal atomic absorption spectrometry.

A rapid, sensitive and selective method for the differential determination of CrIII and CrVI in natural waters is described. Chromium(vi) can be determined directly by flow injection on-line sorbent extraction preconcentration coupled with electrothermal atomic absorption spectrometry using sodium diethyldithiocarbamate as the complexing agent and C18 bonded silica reversed-phase sorbent as the column material. Total Cr can be determined after oxidation of CrIII to CrVI by potassium peroxydisulfate. Chromium(III) can be calculated by difference. The optimum conditions for sorbent extraction of CrVI and oxidation of CrIII to CrVI are evaluated. A 12-fold enhancement in sensitivity compared with direct introduction of 40 microliters samples was achieved after preconcentration for 60 s, giving detection limits of 16 ng l-1 for CrVI and 18 ng l-1 for total Cr (based on 3 sigma). Results obtained for sea-water and river water reference materials were all within the certified range for total Cr with a precision of better than 10% relative standard deviation in the range 100-200 ng l-1. The selectivity of the determination of CrVI was evaluated by analysing spiked reference materials in the presence of CrIII, resulting in quantitative recovery of CrVI.     

Rapid target analysis for pesticides in water by online coated capillary microextraction combined with liquid chromatography and tandem mass spectrometry

The applicability of online trace enrichment with custom-made coated capillaries combined with tandem mass spectrometry was demonstrated for the target analysis of selected pesticides (mainly herbicides, e.g., triazines, phenylureas, and acetanilides) in water. The developed method allows rapid determination of several widely used plant protectants within a total analysis time of 11 min. Good linearity (r > or = 0.995) was obtained for the selected pesticides in the range of 0.050-50 microg/L. The relative standard deviations (RSDs) of the peak areas were < or = 3.8% for spiked Milli-Q water (5 microg/L). The RSDs obtained in analyses of spiked (1 microg/L) water samples (brook water, river water, sewage plant effluent) ranged from 2.9 to 6.8%, indicating low influence of the matrix on enrichment and detection. The detection limits, which ranged from 10 to 90 ng/L, fulfilled the requirements of the European regulations for drinking water. The polyacrylate coating of the extraction capillary showed good stability in the presence of water and acetonitrile and allowed > or = 100 extractions with 1 capillary.     

Determination of estrogens and their metabolites in water using C30 SPE-LC-MS

Triacontyl bonded silica (C(30)) material was applied as solid-phase extraction (SPE) sorbent and an SPE-LC-MS method was established for the determination of eight estrogens and their metabolites in water samples. Compared to commercial C(18) SPE cartridge, the performance of C(30) was evaluated in various important SPE conditions, such as sorbent mass, elution solvent and its volume, loading flow rate, and sample loading volume. The results showed a superior performance of C(30)-C(18) by the shorter treatment time and fewer required elution solvent. In the optimum conditions, the results showed good recoveries (80.5-109.4%), excellent linear relationships (0.02-1 ng/mL, except 2-MeO-E(2)), high precisions (lower than 10.0% RSD for both low and high spiked concentration), and low LODs (1-16 ng/L). Method validation using C(30) packed cartridge was also testified with spiked real water samples, including tap water and river water. Satisfy results demonstrated the feasibility of C(30) SPE to the analysis for real environmental waters.     

Minicolumn field sampling--preconcentration of trace zinc from seawater and its laboratory detection by flow injection flame atomic absorption spectrometry.

A simple field sampling-preconcentration method for zinc determination in seawater is described. Seawater was collected in situ by pumping it through a minicolumn packed with a chelating resin (Chelite P) connected to a field flow preconcentration system (FFPS). These packed minicolumns retain the dissolved zinc, and once are loaded with the analyte, they are returned to the laboratory where they are sequentially inserted into a flow injection system for on-line zinc elution with diluted hydrochloric acid and flame atomic absorption spectrometric detection. A factorial design has been used to optimize the FFPS and the flow injection elution process. The proposed method has a linear calibration range from 0.07 to at least 9.4 microg L(-1) of zinc, with a detection limit of 0.02 microg L(-1) and a throughput of 26 samples h(-1). Validation was carried out against certified reference water samples. This procedure has been successfully applied to the determination of Zn in seawater samples from Galicia (Spain).     

Determination of uranium in tap water by ICP-MS

A fast and accurate procedure has been developed for the determination of uranium at microg L(-1) level in tap and mineral water. The method is based on the direct introduction of samples, without any chemical pre-treatment, into an inductively coupled plasma mass spectrometer (ICP-MS). Uranium was determined at the mass number 238 using Rh as internal standard. The method provides a limit of detection of 2 ng L(-1) and a good repeatability with relative standard deviation values (RSD) about 3% for five independent analyses of samples containing 73 microg L(-1) of uranium. Recovery percentage values found for the determination of uranium in spiked natural samples varied between 91% and 106%. Results obtained are comparable with those found by radiochemical methods for natural samples and of the same order for the certified content of a reference material, thus indicating the accuracy of the ICP-MS procedure without the need of using isotope dilution. A series of mineral and tap waters from different parts of Spain and Morocco were analysed.     

Determination of some organophosphorus and azole group pesticides in water samples by dispersive liquid-liquid microextraction coupled with GC/MS

A dispersive liquid-liquid microextraction (DLLME) procedure coupled with GC/MS detection is described for preconcentration and determination of some organophosphorus and azole group pesticides from water samples. Experimental conditions affecting the DLLME procedure were optimized by means of an experimental design. A mixture of 60 microL chlorobenzene (extraction solvent) and 750 microL acetonitrile (disperser solvent), 3.5 min extraction time, and 7.5 mL aqueous sample volume were chosen for the best recovery by DLLME. The linear range was 1.6-32 microg/L. The LOD ranged from 48.8 to 68.7 ng/L. The RSD values for organophosphorus and azole group pesticides at spiking levels of 3, 6, and 9 microg/L in water samples were in the range of 1.1-12.8%. The applicability and accuracy of the developed method were determined by analysis of spiked water samples, and the recoveries of the analyzed pesticides from artesian, stream, and tap waters at spiking levels of 3, 6, and 9 microg/L were 89.3-105.6, 89.5-103.0, and 92.0-111.3%, respectively.     

Dual gradient LC method for the determination of pharmaceutical residues in environmental samples using a monolithic silica reversed phase column

Detailed below is a simple reversed-phase liquid chromatography (RP-LC) method for the simultaneous separation of up to 21 acidic, basic, and neutral pharmaceuticals using Merck Chromolith Performance RP-C18e monolithic columns with direct ultraviolet (UV) absorption detection. By simultaneously applying a solvent elution gradient program with a mobile phase flow gradient, both a decrease in the overall analysis time and a general increase in peak efficiencies were observed. Mobile phase pH and buffer concentration were optimised using the overall resolution product under applied gradient conditions. Under optimised conditions peak area reproducibility (n?=?6) ranged between 0.4 and 9.3%, determined at the method LOQ level. For real sample analysis pharmaceutical residues were extracted using an optimised solid phase extraction (SPE) procedure, utilising Strata-X extraction cartridges, which overall provided the highest relative recovery data in comparison with four other commercially available SPE sorbents (17 out of 20 residues investigated had recoveries over 70%). Complete method precision, including all sample pre-treatment and LC analysis for six spiked river water samples at the 1 and 2?µg?L^?1 level was between 10 and 29%. Using 1?L volumes of 1?µg?L^?1 spiked estuarine water samples, the majority of detection limits were found to be in the 10–50?ng?L^?1 range.     

Solid‐phase nanoextraction of polychlorinated biphenyls in water and their determination by gas chromatography with electron capture detector

A solid‐phase nanoextraction method has been developed for the extraction and preconcentration of polychlorinated biphenyls using carboxyl multiwalled carbon nanotubes as a solid nano‐sorbent. Parameters affecting extraction efficiency such as sorbent amount, desorption solvent type and volume, extraction time, pH, and salt content have been studied. Under optimized conditions, the correlation coefficient was up to 0.9989, the limits of detection was in the range of 1.4–3.5 ng/L, and limits of quantification was between 4.8 and 11.6 ng/L. The recoveries were in the range of 99–106% for different spiked analytes. The relative standard deviation for water samples spiked with two different spiking levels has been between 4 and 10%. The proposed sustainable method is rapid, easy to use, and small consumption of organic solvent for the detection and determination of trace levels of polychlorinated biphenyls in environmental waters.     

Heat-treated Saccharomyces cerevisiae for antimony speciation and antimony(III) preconcentration in water samples

An analytical method was developed for antimony speciation and antimony(III) preconcentration in water samples. The method is based on the selective retention of Sb(III) by modified Saccharomyces cerevisiae in the presence of Sb(V). Heat, caustic and solvent pretreatments of the biomass were investigated to improve the kinetics and thermodynamics of Sb(III) uptake process at room temperature. Heating for 30 min at 80 degrees C was defined as the optimal treatment. Antimony accumulation by the cells was independent of pH (5-10) and ionic strength (0.01-0.1 mol L(-1)). 140 mg of yeast and 2h of contact were necessary to ensure quantitative sequestration of Sb(III) up to 750 microg L(-1). In these conditions, Sb(V) was not retained. Sb(V) was quantified in sorption supernatant by inductively coupled plasma mass spectrometry (ICP-MS) or inductively coupled plasma optical emission spectrometry (ICP-OES). Sb(III) was determined after elution with 40 mmol L(-1) thioglycolic acid at pH 10. A preconcentration factor close to nine was achieved for Sb(III) when 100mL of sample was processed. After preconcentration, the detection limits for Sb(III) and Sb(V) were 2 and 5 ng L(-1), respectively, using ICP-MS, 7 and 0.9 microg L(-1) using ICP-OES. The proposed method was successfully applied to the determination of Sb(III) and Sb(V) in spiked river and mineral water samples. The relative standard deviations (n=3) were in the 2-5% range at the tenth microg L(-1) level and less than 10% at the lowest Sb(III) and Sb(V) tested concentration (0.1 microg L(-1)). Corrected recoveries were in all cases close to 100%.