Determination of chromium(III) in water by solid-phase microextraction with a polyimide-coated fiber and gas chromatography-flame photometric detection

Potential of hydrophobic paper-based sorptive phase prepared by in-situ thermal imidization for the extraction of methadone from oral fluid samples

Paper-based sorptive phases (PSPs) are functional planar materials with a demonstrated potential in analytical sample preparation. This article describes the synthesis of a polyimide coated paper by an in-situ imidization at a high temperature. Polyimides (PI) are synthesized in two subsequent steps where a hydrophilic polymer, in this case, poly(amic acid) (PAA), is formed as an intermediate product. PAA is finally transformed into hydrophobic PI by thermal curing at 180 °C. The synthesis of PI-paper takes advantage of this two-step procedure. In the first stage, a segment of filter paper is immersed into an aqueous PAA solution. After the solvent evaporation, the paper is heated at 180 °C for 1 h inducing the formation of the hydrophobic PI over the cellulose fibers. Infrared spectroscopy has been used to characterize the synthesized materials by defining a coverage factor F. The hydrophobicity of the materials has been studied using an aqueous methylene blue solution as a marker. To fully demonstrate the usefulness of the material in the sample preparation field, the extraction of methadone from oral fluid (OF) samples has been considered as a model analytical problem. The main variables affecting the synthesis (PAA concentration on the precursor solution and number of dips) and the extraction (elution and extraction times) have been fully evaluated. Working under the optimum conditions, a limit of quantification of 9 µg/L, intraday and interday precision better than 14.6%, and accuracy in the range of 87-108% were obtained.

Protective effects of melatonin and vitamin E in acetamiprid-induced nephrotoxicity

Investigation of probable toxic effects of acetamiprid (ACMP) on kidney and comparative analysis of the probable protective effects of vitamin E and melatonin were conducted in the present study. The ethics committee approval was obtained from Inonu University Medical Faculty Ethics Committee. Fifty Balb-c mice were randomly assigned to control, corn oil, ethyl alcohol, ACMP, ACMP + melatonin, ACMP + vitamin E, and ACMP + melatonin + vitamin E groups. At the end of the experiments, rat kidney tissues were incised under anesthesia. Blood samples and kidney tissues were examined. After 21 days of ACMP administration, it was observed that malondialdehyde (MDA), total oxidant status (TOS), BUN, creatinine, IL-6, IL-1β, and TNF-α levels, histopathological damage, and Caspase-3 immunoreactivity scores increased, and glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), and total antioxidant status (TAS) levels decreased, and histopathological damages were observed. Melatonin and vitamin E administration led to improvements in oxidative stress parameters, renal functions, inflammatory markers, and histopathological findings. ACMP administration led to nephrotoxicity in rat kidney tissues. Although melatonin and vitamin E administrations were effective on ACMP nephrotoxicity separately, co-administration of both was quite effective. Concomitant use of melatonin and vitamin E could be effective on prevention of toxicity.

Preparation of polymethacrylate monolith modified with cysteine for the determination of Cr(iii) ions

In this study, a simple and rapid polymer monolith microextraction procedure was developed for the determination of Cr(iii) ions by inductively coupled plasma-atomic emission spectrometry. A monolithic column modified with cysteine was synthesized and characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermal gravimetric analysis, specific surface area analysis and pore size distribution analysis. The influences of analytical parameters such as sample pH, adsorption time, eluent type, and coexisting ions were examined. The limit of detection (LOD) and limit of quantification (LOQ) for Cr(iii) ions were 0.005 μg mL-1 and 0.017 μg mL-1, and the relative standard deviation (RSD) was 7.4% (n = 5). The prepared cysteine functionalized monolithic column displayed good enrichment capacity and was successfully applied to the determination of Cr(iii) ions in real samples.

A promazine derivative-oriented chemical sensor for ultra-sensitive chromium determination

The study reports a simple and highly selective spectrofluorometric method for trace determination and speciation of chromium(iii & vi) species in water using 10-(3-dimethylaminopropyl) phenothiazine hydrochloride, namely, promazine hydrochloride (PMH) as a fluorescence tagging reagent.

Fluorescent silver nanoclusters for ultrasensitive determination of chromium(VI) in aqueous solution

In this work, a simple and sensitive Cr(VI) sensor is proposed based on fluorescent polyethyleneimine-stabilized Ag nanoclusters, which allows the determination over a wide concentration range of 0.1 nM-3.0 μM and with a detection limit as low as 0.04 nΜ and a good selectivity. The quenching mechanism was discussed in terms of the absorption and fluorescence spectra, suggesting that Cr(VI) is connected to Ag nanoclusters by hydrogen bond between the oxygen atom at the vertex of tetrahedron structure of Cr(VI) and the amino nitrogen of polyethyleneimine that surrounded Ag nanoclusters and electron transfer from Ag nanoclusters to highly electron-deficient Cr(VI) results in fluorescence quenching. Despite the failure to quench the fluorescence efficiently, Cr(III) can also be measured using the proposed Ag nanoclusters by being oxidized to Cr(VI) in alkaline solution (pH ∼ 9) containing H2O2. Therefore, our approach could be used to detect Cr(VI), Cr(III) and the total chromium level in aqueous solution. In addition, Cr(VI) analysis in real water samples were satisfactory, indicating this method could be practically promising for chromium measurements.

An ultrasound-assisted ion association dispersive liquid–liquid microextraction coupled with micro-volume spectrofluorimetry for chromium speciation

A micro-volume spectrofluorimetric coupled ultrasound-assisted ion association dispersive liquid–liquid microextraction (USA-IA-DLLME) procedure for the total determination and speciation of chromium(iii & vi) species has been presented.

Poly(neutral red) based hydrogen peroxide biosensor for chromium determination by inhibition measurements

Amperometric hydrogen peroxide enzyme inhibition biosensors based on horseradish peroxidase (HRP) immobilised on electropolymerised neutral red (NR) or directly on the surface of carbon film electrodes (CFE) have been successfully applied to the determination of toxic Cr(III) and Cr(VI). Parameters influencing the performance of the biosensor including the enzyme immobilisation method, the amount of hydrogen peroxide, applied potential and electrolyte pH were optimised. The inhibition of horseradish peroxidase by the chromium species was studied under the optimised conditions. Results from the quantitative analysis of chromium ions are discussed in terms of detection limit, linear range and sensitivity. The HRP kinetic interactions reveal mixed binding of Cr(III) with I50=3.8μM and inhibition binding constant Ki=11.3μM at HRP/PNR/CFE biosensors and uncompetitive binding of Cr(VI) with I50=3.9μM and Ki=0.78μM at HRP/CFE biosensors in the presence of H2O2 substrate. Interferences from other heavy metal ions were studied and the inhibition show very good selectivity towards Cr(III) and Cr(VI).

Surfactant Sensitized Calix[4]arenes Fluorescence Quenching Method for Speciation of Cr(VI)/Cr(III) in Water Samples

The surfactant sensitized spectrofluorimetry for speciation of chromium (Cr(VI)/Cr(III)) was developed. The analytical procedure was that the fluorescence intensity of l4,10,16,22-tetramethoxyl resorcinarene carboxylic acid derivatives (TRCA) could be selectively quenched by Cr(VI) and the fluorescence quenching value (ΔF=FTRCA-FCr(VI)-TRCA) was increased in cetyltrimethylammonium bromide (CTAB). The main influence factors on the fluorescence quenching (ΔF) were investigated in detail. Under the optimal conditions, the linear range of calibration curve for the determination of Cr(VI) was 0.10~5.00 μg/mL, and the detection limit was 0.024 μg/mL with RSD=2.10% (c=1.0 μg/mL, n=3). The concentration of Cr(III) was calculated by subtracting Cr(VI) from the total chromium determined after oxidizing Cr(III) to Cr(VI). The preliminary sensitized mechanism was discussed with the inclusion constant (K) of TRCA-Cr(VI), the fluorescence quantum yield of TRCA, and IR spectra characterization. The method has been applied to the speciation analysis of Cr(VI)/Cr(III) in water samples.

Solid phase extraction and determination of Cr(III) by spectrophotometry using cefaclor as a complexing reagent and FAAS

The present study reports on the application of modified groundnut shell as a new, easily prepared, and stable sorbent for the extraction of trace amount of Cr(III) in aqueous solution. 2-Hydroxybenzaldiminoglycine was immobilized on groundnut shells in alkaline medium and then used as a solid phase for the column preconcentration of Cr(III). The elution was carried out with 3 mL of 2 mol L(-1) HCl. The amount of eluted Cr(III) was determined by spectrophotometry using cefaclor as a complexing reagent and by flame atomic absorption spectrometry (FAAS). Different experimental variables such as pH, amount of solid sorbent, volume and concentration of eluent, sample and eluent flow rate, and interference of other metal ions on the retention of Cr(III) were studied. Under the optimized conditions, the calibration curves were found to be linear over the concentration range of 13-104 and 10-75 μg L(-1) with a detection limit of 3.64 and 1.24 μg L(-1) for spectrophotometric method and FAAS, respectively. An enrichment factor of 200 and RSD of ±1.19-1.49 % for five successive determinations of 25 μg L(-1) were achieved. The column preconcentration was successfully applied to the analysis of tap water and underground water samples.

Chromium speciation in environmental samples using a solid phase spectrophotometric method

A solid phase extraction technique is proposed for preconcentration and speciation of chromium in natural waters using spectrophotometric analysis. The procedure is based on sorption of chromium(III) as 4-(2-benzothiazolylazo)2,2'-biphenyldiol complex on dextran-type anion-exchange gel (Sephadex DEAE A-25). After reduction of Cr(VI) by 0.5 ml of 96% concentrated H(2)SO(4) and ethanol, the system was applied to the total chromium. The concentration of Cr(VI) was calculated as the difference between the total Cr and the Cr(III) content. The influences of some analytical parameters such as: pH of the aqueous solution, amounts of 4-(2-benzothiazolylazo)2,2'-biphenyldiol (BTABD), and sample volumes were investigated. The absorbance of the gel, at 628 and 750 nm, packed in a 1.0 mm cell, is measured directly. The molar absorptivities were found to be 2.11×10(7) and 3.90×10(7) L mol(-1)cm(-1) for 500 and 1000 ml, respectively. Calibration is linear over the range 0.05-1.45 μg L(-1) with RSD of <1.85% (n=8.0). Using 35 mg exchanger, the detection and quantification limits were 13 and 44 ng L(-1) for 500 ml sample, whereas for 1000 ml sample were 8.0 and 27 ng L(-1), respectively. Increasing the sample volume can enhance the sensitivity. No considerable interferences have been observed from other investigated anions and cations on the chromium speciation. The proposed method was applied to the speciation of chromium in natural waters and total chromium preconcentration in microwave digested tobacco, coffee, tea, and soil samples. The results were simultaneously compared with those obtained using an ET AAS method, whereby the validity of the method has been tested.

Preconcentration method on modified silica fiber for chromium speciation

A new method involving pre-concentration on modified silica fiber is described for the speciation of chromium(III) [Cr(III)] and chromium(VI) [Cr(VI)] in aqueous media. This method is based on the different chelating behavior of Cr(III) and Cr(VI) with morpholine-4-carbodithioate (MDTC). Both complexes are extracted on silica fiber modified by sol-gel technology by using 3-aminopropyltriethoxysilane (APS) as a precursor. All extracted samples are directly injected into an high-performance liquid chromatography injector for the simultaneous determination of Cr(III) and Cr(VI). Cr(VI) forms two different complexes, and Cr(III) forms a single complex with MDTC. Therefore, the concentration of Cr(VI) is determined directly from the peak area obtained at 5.4 min; whereas, the assay of Cr(III) is based on subtracting the peak area of Cr(VI) from the total peak area obtained at 4.3 min. Under the optimized conditions, the limits of detection for Cr(III) and Cr(VI) are found to be 0.7 ng/mL and 0.2 ng/mL, respectively.

Date-palm fibers media filters as a potential technology for tertiary domestic wastewater treatment

A number of municipal wastewater treatment systems were developed to improve effluent water quality, however economic aspects should be considered. This study was thus carried out to investigate the application of date-palm fibers filtration as an efficient method to economically remove turbidity, phosphorus, organics in term of COD and helminth eggs of secondary domestic wastewater from an activated sludge treatment process. Column experiments were investigated to study the efficiency of date-palm fibers filters media used in this work for the removal of targeted matter under operational conditions (flow rate, filter depth, and diameter of the fibers). The results indicate that diameter of the fibers had the most significant factor affecting the removal of targeted matter. Pilot test results indicated that date-palm fibers filtration removed up to 54.9% of turbidity, 80.6% of COD, 57.7% of phosphorus and 98% of helminth eggs. Definitely, it could be concluded that the date-palm fibers could offer an appreciable economic and environmental potential, which should be in a position to effectively contribute to the valorisation of such as date-palm by-products for domestic or industrial wastewater treatment in southern of Tunisia.

Microwave-assisted derivatization and single-drop microextraction for gas chromatographic determination of chromium(III) in water

A rapid and efficient sample preparation method combining microwave-assisted derivatization (MAD) and single-drop microextraction (SDME) for the gas chromatographic (GC) determination of trace Cr(III) in water was developed. Aqueous Cr(III) was first converted to the volatile chromium trifluoroacetylacetonate (Cr(tfa)3) by reaction with 1,1,1-trifluoroacetylacetone (Htfa) under the irradiation of microwave. Derivatization of Cr(III) at ng ml(-1) level could be completed in less than 1 min. The formed Cr(tfa)3 was then extracted into a small droplet (2 microl) of toluene suspended at the tip of a microsyringe needle. The optimal extraction time was 30 min. The solvent drop was directly injected into a GC equipped with a flame photometric detector (FPD) for analysis. The two Cr(tfa)3 isomers extracted could be efficiently separated in 2 min. Linearity (r>0.99) over the concentration range 2-300 ng ml(-1) Cr was obtained and the limit of detection was 0.5 ng ml(-1) Cr. The relative standard deviation was 7.8% at 20 ng ml(-1) Cr (n=5). Applicability of this method to water analysis was examined by analyzing the chromium content in a reference standard water sample and an industrial effluent.

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).

Sensitive determination of thiamethoxam, imidacloprid and acetamiprid in environmental water samples with solid-phase extraction packed with multiwalled carbon nanotubes prior to high-performance liquid chromatography

This paper describes a novel method for sensitive determination of thiamethoxam, imidacloprid and acetamiprid based on solid-phase extraction with multiwalled carbon nanotubes as the packed materials. Factors that maybe influence the enrichment efficiency, such as sample flow rate, sample pH, and sample volume, were investigated in detail. Under the optimized conditions, the detection limits of thiamethoxam, imidacloprid and acetamiprid were 6.1, 5.4 and 6.7 ng L(-1), respectively. The experimental results indicated that there was good linearity (R2>0.9993) over the range of 0.08 approximately 100 ng mL(-1) and good reproducibility with the relative standard deviations over the range of 0.7 approximately 1.1% (n=6). The proposed method has been applied to the analysis of real-world water samples, and satisfactory achievements were obtained. The average spiked recoveries were in the range of 87.5 approximately 109.8%. All the results indicated that the proposed method could be used for the simultaneous determination of the three pesticides in environmental water samples at trace levels.

Recent developments in solid-phase microextraction coatings and related techniques

During the last decade, solid-phase microextraction (SPME) has gained widespread acceptance for analyte matrix separation and preconcentration. Relatively few data are currently available dealing with in-house production of fibres with tailor-made properties to be used for SPME, though recently the number of publications evaluating new coatings has been considerably growing. This review, centred on publications that appeared during the last five years, is resuming different approaches which can be used for fibre production and further summarises alternative techniques closely related to SPME, such as in-tube extraction or single-drop microextraction (SDME). The aim is to give the reader a concise overview of recent developments in new coating procedures and materials, including the respective applications.

Effluent analysis in analytical chemistry: an overview

This review summarizes and discusses effluent analysis, focusing on the methods and techniques that have been most frequently described in the literature since 1975. The methods are classified into four main categories: (1) physical and chemical properties; (2) inorganic metals analysis; (3) inorganic non-metallic analysis; (4) organic analysis.