Trace Levels In Environmental Samples Research Articles

Determination of residual bendiocarb in environmental samples using magnetic nanoparticles modified with cetyldimethylbenzylammonium chloride by UV-Vis spectrophotometry

ABSTRACT Bendiocarb (BEN), a highly toxic carbamate insecticide used in agriculture, is effective against various nuisance and disease vector insects. Utilizing Fe3O4 magnetic nanoparticles coated with cetyldimethylbenzylammonium chloride (CDMC), a simple and sensitive solid-phase microextraction technique has been devised for the preconcentration and determination of BEN at trace levels in environmental samples. Fe3O4@CDMC nanoparticles (NPs) were utilised as the magnetic solid-phase extraction agents. The azo-dye produced between BEN and the diazotised procaine benzylpenicillin (drug compound) adsorbed on the NPs was eluted using ethanol and quantified spectrophotometrically at wavelength 456 nm. Experimental factors impacting the extraction efficiency of the method were optimised: the amount of surfactant (1 mg) and the sorbent (30 mg), type and volume of base (sodium hydroxide, 2 mL), type and volume of eluent (ethanol, 1 mL), and extraction time (15 min). The relative standard deviation (RSD%) of the method was investigated and it ranged from 1.8–4.2% (n = 5). Upon optimisation, BEN could be concentrated from different samples 50-fold with an enrichment factor of 72. The linear range, correlation coefficient (R) and detection limit could reach 0.03–1.5 µg/mL, 0.9984 and 0.01 µg/mL, respectively. The technique has been effectively verified for detecting bendiocarb in various environmental samples.

Ultrasound assisted supramolecular liquid phase microextraction procedure for Sudan I at trace level in environmental samples.

A method based on supramolecular liquid phase microextraction has been developed for the preconcentration and determination of trace levels of Sudan I. 1-decanol and tetrahydrofuran were used as supramolecular solvent components. Trace levels of Sudan I were extracted into the extraction solvent phase at pH = 4.0 Analytical parameters such as pH value, supramolecular solvent volume, ultrasonication, centrifugation, model solution volume, matrix effects have been optimized. The limit of detection and the limit of quantification values for Sudan I were calculated as 1.74 μg L−1 and 5.75 μg L−1, respectively. In order to determine the accuracy of the method, addition and recovery studies were carried out to environmental samples.

Determination of Palladium in Precious Metal Waste by Sieve Conducted Two Syringes Pressurized Liquid Phase Microextraction (SCTS-PLPME) and Slotted Quartz Tube Flame Atomic Absorption Spectrometry (SQT-FAAS)

Determination of palladium at trace levels in environmental samples is essential due to its harmful properties and threats to living organisms. Hence, a simple but efficient liquid-phase microextraction method is reported by sieve conducted two syringes pressurized liquid phase microextraction (SCTS-PLPME) and slotted quartz tube flame atomic absorption spectrometry (SQT-FAAS). The originality of this system is based on the elimination of disperser solvents that are used to increase the surface area of extractant. The high pressure created by the movement of syringe plungers results in efficient dispersion of the extractants in the sample solution. Parameters that affect the overall efficiency of the extraction method were carefully optimized. The limit of detection (LOD) and quantification (LOQ) under the optimum conditions were 6.0 and 20.0 μg L−1, respectively. The developed method showed good linearity between 20 and 1000 μg L−1, and provided a 25-fold enhancement in detection power compared to conventional FAAS. The optimized method was successfully used to determine the analyte in precious metal waste samples.

Improved LC–MS/MS Method for the Simultaneous Determination of Synthetic Phenol Antioxidants and Relevant Metabolites Making Use of Atmospheric Pressure Chemical Ionization and a Trap Column

The prevalently used LC–MS/MS methods for the simultaneous determination of synthetic phenol antioxidants (SPAs) and relevant metabolites suffer from a serious drawback of low sensitivity for 2,6-di-tert-butyl-4-hydroxytoluene (BHT) and a common issue of background contamination, which hampers the simple and accurate detection of these substances at trace levels in environmental samples. In this study, we developed an improved LC–MS/MS method for the simultaneous determination of eight SPAs and four relevant metabolites, including BHT. By use of atmospheric pressure chemical ionization (APCI), the sensitivity of BHT in the LC–MS/MS was enhanced approximately 260 times versus results obtained by using electrospray ionization (ESI), which allowed the analysis of BHT up to 1.1 ng/g in indoor dust and 0.06 ng/g in human plasma. Similarly, the sensitivity of 2,4,6-tri-tert-butylphenol and 2,6-di-tert-butyl-4-sec-butylphenol was also enhanced with APCI, which avoided their separate analysis by GC–MS. By installation of a C18 column after the eluent mixer and before the injector as a trap column, the target analytes leached out from the LC system were eluted at a much later retention time than those in the samples, which resulted in complete elimination of the instrumental background contamination. These improvements enable the method to be well applied to the real samples.

Cloud point extraction and FAAS determination of copper(II) at trace level in environmental samples using N-benzamido-N'-benzoylthiocarbamide and CTAB

The present work describes a simple method to detect copper(II) using flame atomic absorption spectrometry (FAAS) after pre-concentration and separation by cloud point extraction(CPE) using N-benzamido-N'-benzoylthiocarbamide (HBBTC) complexing agent and cetyltrimethylammonium bromide (CTAB) as a cationic surfactant. The different experimental parameters such as pH, the concentration of the reagent, centrifuging time, and concentration of CTAB and potassium iodide were examined to increase the extraction efficiency of the proposed procedure. Under optimized extraction conditions the limits of detection and limits of quantification were found to be 0.9 and 2.70 ng mL−1, respectively. The present work was successfully employed for the determination of copper(II) in synthetic mixtures and in water samples with a recovery% greater than 97% and RSD(%) = 0.18 %.

Zinc(II)-based metal–organic nanotubes coating for high sensitive solid phase microextraction of nitro-polycyclic aromatic hydrocarbons

Metal–organic nanotubes (MONTs) have great potential for solid phase microextraction (SPME) on account of high specific surface area, tunable pore sizes, and exceptional thermal and chemical stability. In this work, zinc (II)-based metal–organic nanotubes (Zn-MONTs) were used as an adsorbent for the SPME of nitro-polycyclic aromatic hydrocarbons (NPAHs) at trace levels from environmental water samples. Gas chromatography–mass spectrometry was used for sample analysis and key factors were investigated and optimized. Under optimal parameters, the developed method achieved low limits of detection (1.4–7.3 ng L−1), wide linear range (10–5000 ng L−1), and high enrichment factors (1510−17,684). In comparison to the PDMS and DVB/CAR/PDMS fiber for potential commercial use, the Zn-MONTs fiber obtained MS responses 2–9 times as high as those achieved by the commercial 100 µm PDMS and 0.2–2.3 times higher than 50/30 µm DVB/CAR/PDMS fiber did. The proposed method was successfully used in the analysis of NPAHs at trace levels in environmental samples.

Thallium release from acid mine drainages: Speciation in river and tap water from Valdicastello mining district (northwest Tuscany)

In this work we present an advantageous method for the simultaneous separation and detection of Tl(I) and Tl(III) species through ion chromatography coupled with on-line inductively coupled plasma – mass spectrometry. Chromatographic separation between Tl(III) and Tl(I) was achieved in less than two minutes. The method was validated by recovery experiments on real samples, and by comparing the sum of the concentrations of individual Tl species with total thallium values obtained from continuous flow ICP-MS. The experimental procedure offers an accurate, sensitive and interference-free method for Tl speciation at trace levels in environmental samples. This allowed us to investigate the Tl speciation in acid mine drainages (AMD), surface waters and springs in a mining catchment in Valdicastello Carducci (Tuscany, Italy), where severe Tl contamination ad been evidenced previously. This study shows for the first time that Tl(III), in addition to Tl(I), is present in considerable amounts in water samples affected by acid mining outflow, raising the question of the origin of this thermodynamically unstable species.

On-line Green Solid Phase Extraction of Trace Rare Earth Elements and Uranium in Environmental Samples and ICP OES Detection

An on-line solid phase extraction (SPE) method using mini column packed with natural sorbent based on cotton roll dyed by quinalizarin was developed for simultaneously pre-concentration of rare earth elements and uranium at trace levels in environmental samples followed by inductively coupled plasma optical emission spectrometry (ICP OES) determination. Various parameters such as sample and eluent flow rate, sample volume and matrix ions on the method efficiency have been investigated. Under the optimized conditions, the limits of detection (LODs, 3σ) for rare earth elements were in the range of 0.002-0.300 µg L-1 and 0.420 µg L-1 for uranium. The relative standard deviation (n = 5) were lower than 6% except for samarium and uranium. The method was successfully applied for determination of trace rare earth elements and uranium in lake, well, tap water and carbonate mineral samples. The accuracy of the proposed method was validated by add-found method and direct analysis by ICP OES. This method has some advantages such as simplicity, rapidity, green chemistry and high sensitivity.

Synthesis, characterization and application of poly(acrylamide-co-methylenbisacrylamide) nanocomposite as a colorimetric chemosensor for visual detection of trace levels of Hg and Pb ions

In this study, a new colorimetric chemosensor based on TiO2/poly(acrylamide-co-methylenbisacrylamide) nanocomposites was designed for determination of mercury and lead ions at trace levels in environmental samples. The removal and preconcentration of lead and mercury ions on the sorbent was achieved due to sharing an electron pair of N and O groups of polymer chains with the mentioned heavy metal ions. The hydrogel sensor was designed by surface modification of a synthesized TiO2 nanoparticles using methacryloxypropyltrimethoxysilan (MAPTMS), which provided a reactive CC bond that polymerized the acrylamide and methylenbisacrylamide. The sorbent was characterized using X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscope (SEM), EDS analysis and Fourier transform in frared (FT-IR) spectrometer. This nanostructured composite with polymer shell was developed as a sensitive and selective sorbent for adsorption of mercury and lead ions from aqueous solution at optimized condition. This method involves two-steps: (1) preconcentration of mercury and lead ions by the synthesized sorbent and (2) its selective monitoring of the target ions by complexation with dithizone (DZ). The color of the sorbent in the absence and presence of mercury and lead ions shifts from white to violet and red, respectively. The detection limit of the synthesized nanochemosensor for mercury and lead ions was 1 and 10μgL−1, respectively. The method was successfully applied for trace detection of mercury and lead ions in tap, river, and sea water samples.

Detection and identification of hydrolysis products of sulfur mustards at trace levels in environmental samples using liquid chromatography solid phase extraction combined with off-line nuclear magnetic resonance analysis

An LC-UV-SPE NMR method for the analysis of polar hydrolysis products of the chemical warfare agents known as sulfur mustards at low ppm levels in environmental samples is developed. The hydrolysis products thiodiglycol (I), bis(2-hydroxyethylthio)methane (II), 1,2-bis(2-hydroxyethylthio)ethane (III), 1,3-bis(2-hydroxyethylthio)propane (IV), 1,4-bis(2-hydroxyethylthio)butane (V), 1,5-bis(2-hydroxyethylthio)pentane (VI), bis(2-hydroxymethylthioethyl)ether (VII) and bis(2-hydroxyethylthioethyl)ether (VIII) are baseline separated within 11min by the LC gradient program and trapped post-column on SPE cartridges. After elution in 2mm o.d. NMR tubes 1H NMR spectra were recorded. Recoveries vary from 43±5 for I to 102±5% for VI and are limited by volume breakthrough. The detection limits of the LC-SPE NMR method vary between 200ng for V and 450ng for I. Increasing the injection volume is shown to be more effective than multiple trapping for the analytes I–VIII to increase the amount of material trapped on the SPE cartridges. The applicability of the developed method to the analysis of environmental samples was tested by the analysis of sample 293 provided by the 29th Official OPCW (Organization for the Prohibition of Chemical Weapons) Proficiency Test. The chromatographic and 1H NMR data obtained by the method are highly reproducible and provide acceptable data for the identification of chemicals related to CWC (Chemical Weapons Convention) in case an off-site analysis for the verification of the CWC or OPCW Proficiency Tests according to the OPCW criteria for the acceptance of chromatographic and 1H NMR spectral data.

Preparation and application of poly(2-amino thiophenol)/MWCNTs nanocomposite for adsorption and separation of cadmium and lead ions via solid phase extraction

A new method which utilizes a multiwalled carbon nanotubes/poly(2-amino thiophenol) nanocomposites as an effective sorbents in solid-phase extraction has been developed for separation and preconcentration of Cd(II) and Pb(II) trace levels in environmental samples. The method is based on the adsorption of heavy metals on macromolecular chains due to sharing an electron pair of N and S groups of conducting polymer with cadmium and lead ions. The results indicate the novel nanocomposite presents a high affinity for heavy metals due to the presence of several good extractive sites (S and N) which are introduced to the synthesized nanocomposite. Some parameters including sample condition such as: pH, flow rate, sample volume, and eluent condition such as: type, volume, and concentration: moreover adsorption capacity of matrix ions was investigated on the recovery of Cd(II) and Pb(II). The maximum adsorption capacity of MWCNTs/P2AT nanocomposite as sorbents at optimum conditions for cadmium and lead ions was found to be 178.7 mg g −1 and 186.4 mg g −1, respectively. The detection limits of this method were 0.3 and 1 ng mL −1 for Cd(II) and Pb(II), respectively. The validation of the presented procedure was checked by reference material analysis. Finally, the presented procedure was applied for determination of Cd(II) and Pb(II) in some environmental samples.

Cloud point extraction and spectrophotometric determination of mercury species at trace levels in environmental samples

A new micelle-mediated separation and preconcentration method was developed for ultra-trace quantities of mercury ions prior to spectrophotometric determination. The method is based on cloud point extraction (CPE) of Hg(II) ions with polyethylene glycol tert-octylphenyl ether (Triton X-114) in the presence of chelating agents such as 1-(2-pyridylazo)-2-naphthol (PAN) and 4-(2-thiazolylazo) resorcinol (TAR). Hg(II) ions react with both PAN and TAR in a surfactant solution yielding a hydrophobic complex at pH 9.0 and 8.0, respectively. The phase separation was accomplished by centrifugation for 5min at 3500rpm.The calibration graphs obtained from Hg(II)–PAN and Hg(II)–TAR complexes were linear in the concentration ranges of 10–1000μgL−1 and 50–2500μgL−1 with detection limits of 1.65 and 14.5μgL−1, respectively. The relative standard deviations (RSDs) were 1.85% and 2.35% in determinations of 25 and 250μgL−1 Hg(II), respectively. The interference effect of several ions were studied and seen commonly present ions in water samples had no significantly effect on determination of Hg(II). The developed methods were successfully applied to determine mercury concentrations in environmental water samples. The accuracy and validity of the proposed methods were tested by means of five replicate analyses of the certified standard materials such as QC Metal LL3 (VWR, drinking water) and IAEA W-4 (NIST, simulated fresh water).

Novel coupling reactions of phytochemicals with sulfa drugs and their applications in the determination of nitrite at trace level in environmental samples

Twelve spectrophotometric methods based on new reactions for the determination of trace amounts of nitrite in environmental samples were developed. Replacement of toxic reagents was explored to attain the standards of clean chemistry. These methods utilize two classes of compounds namely; phytochemicals and sulfonamides, in the presence of limited amounts of sodium hydroxide. The methods were based on the oxidation of sulfanilamide (SAA), sulfadoxine (SDX), sulfamethoxazole (SMX) or sulfadiazine (SDZ) by nitrite in sodium hydroxide medium and coupling with cardol, cardanol or anacardic acid which yielded yellow, orange and orange red color derivatives having an absorbance maximum in the range 430, 460 and 470nm, respectively. The colors developed were stable for about 3h. Beer’s law was obeyed for nitrite in the concentration range 0.08–0.90, 0.16–1.04, 0.08–0.80 and 0.08–0.80μgml−1 for cardol; 0.80–4.40, 1.60–5.72, 0.52–5.20 and 0.80–4.40μgml−1 for cardanol and 0.80–5.70, 1.04–6.20, 1.30–5.20 and 0.80–4.00μgml−1 for anacardic acid, respectively. The reaction conditions and other important analytical parameters were optimized to enhance the sensitivity of the methods. Interference if any, by non-target ions was also investigated. The methods were applied determining nitrite in environmental samples. The performances of these methods were evaluated in terms of Student’s t-test and variance ratio F-test to find out the significance of the proposed methods over the reference spectrophotometric method.

Determination of trace silver in environmental samples by room temperature ionic liquid-based preconcentration and flame atomic absorption spectrometry

We report on a new method for preconcentration of silver ion at trace level in environmental samples, and its subsequent determination by flame atomic absorption spectrometry (FAAS). The room temperature ionic liquid (RTIL) 1-butyl-3-methylimidazolium hexafuorophosphate and the chelator 5-(4-dimethylaminobenzylidene)-rhodanine were used for extraction. Ag(I) was back-extracted from the organic phase into thiosulfate solution and then determined via FAAS. The effects of pH, concentration of chelating agent, extraction time and temperature, amounts of ionic liquid, ionic strength and potentially interfering ions were studied. Under optimized conditions, the enhancement factor is 30 was achieved. The detection limit (3 σ) is 0.28 ng mL−1, and the relative standard deviation is 4.1% for 7 replicate determinations at 5 ng mL−1 of Ag(I). The method was validated by analysis of certified reference materials and applied to the determination of Ag(I) in environmental samples with satisfactory results.

Measurement of uranium and its isotopes at trace levels in environmental samples using mass spectrometry

Actinides have widely entered the environment as a result of nuclear accidents and atmospheric weapon testing. These radionuclides, especially uranium, are outstanding radioactive pollutants, due to their high radiotoxicity and long half-lives. In addition to this, since depleted uranium (DU) has been used in the Balkan conflict in 1999, there has been a concern about the possible consequences of its use for the people and environment. Therefore, accurate, precise and simple determination methods are necessary in order to evaluate the human dose and the concentration and effects of these nuclides in the environment. The principal isotopes of uranium e.g.235U and 238U are of primordial origin and 234U present in radioactive equilibrium with 238U. 236U occurs in nature at ultra trace concentrations with a 236U: 238U atom ratio of 10−14. Concentrations of uranium in soil samples were determined using inductively coupled plasma mass spectrometry (ICP-MS) and isotope ratios of uranium were measured using a thermal ionisation mass spectrometer. Radioactive dis-equilibrium of 234/238U, depletion of 235/238U and significant evidence of 236U/238U were noticed in soil samples.

Novel oxidative coupling reactions of cisapride or metaclopramide with phenoxazines and their applications in the determination of nitrite at trace level in environmental samples

Phenoxazine (PNZ), 2-chlorophenoxazine (CPN) and 2-trifluoromethylphenoxazine (TPN) were used as new class of spectrophotometric reagents for the determination of nanoamounts of nitrite in presence of cisapride (CSP) and metaclopramide (MCP) as new electrophilic coupling reagents. The methods were based on the oxidation of CSP or MCP by nitrite in hydrochloric acid medium and coupling with PNZ, CPN or TPN to yield red color derivatives which were stable for about 3 h and having an absorbance maximum in the range 520–530 nm. Beer's law is obeyed for nitrite in the concentration range 0.08–0.80 and 0.13–1.60 μg ml −1 for phenoxazine-cisapride and phenoxazine-metaclopramide, respectively. The optimum reaction conditions and other important analytical parameters were established to enhance the sensitivity of these methods. Interference due to various non-target ions was also investigated. The methods were applied to the analysis of nitrite in environmental samples. The performance of proposed methods were evaluated by Student's t-test and variance ratio F-test indicated the significance of proposed methods over the reference spectrophotometric method (Association of Official Analytical Communities (AOAC) method for the determination of nitrite in water samples).

Fibrinogen‐Coated Bismuth Film Electrodes for Voltammetric Analysis of Lead and Cadmium using the Batch Injection Analysis

This work reports the application of fibrinogen‐coated bismuth films deposited on carbon paste electrodes (Fbg‐BiFEs) for the simultaneous determination of trace amounts of lead and cadmium by square‐wave anodic stripping voltammetry, combined with a batch injection analysis technique (BIA‐SWASV). The batch injection analysis system provides the advantages of rapid and simple electroanalysis of microliter samples. Its use in combination with Fbg‐BiFEs allowed the determination of metals at trace levels in environmental samples, given that the surfactant interference observed with stripping analysis at bismuth electrodes could be minimized by use of a fibrinogen coating. The analytical characteristics, namely sensitivity, detection limits, and resistance to surfactants in the anodic stripping voltammetry of lead and cadmium, were investigated in acetate buffer. The resulting limits of detection were 0.2 µg L−1 and 0.1 µg L−1, for Cd and Pb respectively. Finally, the system based on Fbg‐BiFEs combined with BIA‐SWASV was applied to different real samples (tap water and tea samples) for analysis of trace metals with satisfactory results.

Column Solid Phase Extraction of Copper, Iron, and Zinc Ions at Trace Levels in Environmental Samples on Amberlite XAD‐7 for Their Flame Atomic Absorption Spectrometric Determinations

A column solid‐phase extraction method for the separation and preconcentration of copper, zinc, and iron at trace levels has been established prior to their flame atomic absorption spectrometric determinations. Analytes from 0.5 M KSCN in a 1 M HCl solution were recovered using of an Amberlite XAD‐7 column. The chemical variables affecting the analytical performance of the combined methodology including reagent amounts, sample volume, flow rates of sample, and eluent solutions on the quantitative recoveries of analyte ions were studied and optimized. The presented method was applied to the analysis of natural waters and red wine sample with satisfactory results (recoveries greater than 95%, relative standard deviations (RSD) lower than 8%). The accuracy and precision of the method were confirmed by the analysis of three kinds of certified reference materials (NRCC‐SLRS‐4 riverine water, SRM 1515 apple leaves, and SRM 2711 Montana soil).

A model for fitting peaks induced by fast neutrons in an HPGe detector

Inelastic neutron scattering in the HPGe detector produces wide, triangular-shaped peaks in the spectrum. We develop an accurate model for the peak shape and show that the inclusion of the model in the gamma spectrum analysis makes it possible to quantify fast neutron scattering in the Ge crystal and improves the estimation of the baseline. This in turn facilitates the detection of fission products present at trace levels in environmental samples. The model, together with simulations, is used to deduce some properties of the underlying neutron energy distribution. The neutron evaporation temperature of 1.1 MeV is obtained from the analysis of environmental monitoring gamma spectra.

Determination of alkyltrimethylammonium chlorides in river water by gas chromatography/ion trap mass spectrometry with electron impact and chemical ionization.

This work describes a modified method to analyze alkyltrimethylammonium chlorides (ATMACs) in river water samples. The proposed method involves adding solid potassium iodide to water sample (pH adjusted to 10.0) as a counterion to enhance the extraction of ATMAC residues by dichloromethane liquid-liquid extraction. The iodide-ATMA+ ion pairs were demethylated to their corresponding nonionic alkyldimethylamines (ADMAs) by thermal decomposition in a GC injection port. The corresponding ADMAs were then identified and quantitated by gas chromatography/ion trap mass spectrometry (GC/MS) in electron impact and low-pressure positive ion chemical ionization (PICI) modes. A relatively high abundance of ADMAs was detected at a demethylation temperature above 300 degrees C in the injection port. Experimental results indicate that the proposed method is precise and sensitive in ATMACs analysis and allows quantitation at < or = 0.01 microg/L in 500 mL of the water samples. The enhanced selectivity of quasi-molecular ion chromatograms of C12-C18-ADMA, obtained using methanol PICI-MS, enables ATMAC residues to be identified at trace levels in environmental samples. Recovery of the ATMACs in various spiked water samples ranged from 70 to 94% while RSD ranged from 3 to 12%. The concentrations of total measured ATMAC residues in river water samples ranged from nondetectable to 1.24 microg/L.