Simultaneous determination of iprodione,procymidone, and chlorflurenol in lake water and wastewater matrices by GC-MS after multivariate optimization of binary dispersive liquid-liquid microextraction

This study reports the optimization of a binary dispersive liquid-liquid microextraction method for the determination of iprodione, procymidone, and chlorflurenol by gas chromatography mass spectrometry. The study was aimed at using two extraction solvents to increase the extraction efficiency of all analytes. The binary solvents recorded results higher than the mono-solvents. After examining the effects of main experimental parameters and their interactions by analysis of variance, 200 μL of binary mixture (dichloromethane and 1,2-dichloroethane), 2.5 mL of ethanol, and 15 s vortex were obtained as optimum parameters. The detection and quantification limits calculated for the analytes were found to be between 0.30–1.6 and 1.0–5.3 ng/mL, respectively. Enhancement in detection power calculated as a ratio of the binary extraction detection limit to the detection limit of direct GC-MS analysis was 105-, 214-, and 233-fold for chlorflurenol, iprodione, and procymidone, respectively. In order to check the accuracy of the developed method, recovery study was performed. Water sampled from a lake and two wastewater samples from treatment facilities were spiked at two concentrations, and the percent recovery calculated for the samples ranged between 87 and 116%. These results confirmed the suitability of the method to real samples for accurate determination of the analytes at trace levels.     

Simultaneous determination of estrone and selected pesticides in water medium by GC-MS after multivariate optimization of microextraction strategy

A sensitive and accurate analytical method based on dispersive liquid-liquid microextraction was developed for the simultaneous determination of selected pesticides, hormones, and endocrine disruptors by GC-MS. The optimum conditions of the extraction procedure were determined using an experimental design of factors significantly affecting the extraction output. Analysis of variance (ANOVA) was used to evaluate the main effects of experimental factors and their interactions. The limit of detection values determined for the analytes under optimum experimental conditions were found to be between 0.30–2.0 ng/mL. The linear calibration plot of analytes span across a wide concentration range and low %RSD values from replicate measurements indicated good precision of the developed method. Spiked recovery tests were also performed on municipal wastewater, well water, lake water, sea water, and tap water matrices to determine the method’s accuracy and applicability to water samples. The recovery results obtained were satisfactory for all water samples.     

Preconcentration and speciation of Cr(III) and Cr(VI) in water and soil samples by spectrometric detection via use of nanosized alumina-coated magnetite solid phase

A novel nanomaterial has been developed for speciation of Cr(III) and Cr(VI) in water and soil samples. In this study, a new type of alumina-coated magnetite nanoparticles (Fe₃O₄/Al₂O₃ NPs) modified by the surfactant Triton X-114 has been successfully synthesized and used in magnetic mixed hemimicelles solid-phase extraction procedure. The procedure was based on the reaction of chromium(III) with 1-(2-pyridilazo)-2-naphtol as a ligand, yielding a complex, which was entrapped “in situ” in the surfactant hemimicelles. The concentration of chromium(III) was determined using flame atomic absorption spectrometry. After reduction of Cr(VI) to Cr(III) by ascorbic acid, the system was applied to the total chromium. Cr(VI) was then calculated as the difference between the total Cr and the Cr(III) content. This method can also be used for complicated matrices such as soil samples without any special pretreatment. Under the optimum conditions of parameters, the recoveries of Cr(III) by analyzing the spiked water and soil samples were between 98.6 and 100.8 % and between 96.5 and 100.7 %, respectively. Detection limits of Cr(III) were between 1.4 and 3.6 ng?mL^?1 for water samples and 5.6 ng?mg^?1 for soil samples.     

Solid phase extraction of Cd,Pb, Ni,Cu, and Zn in environmental samples on multiwalled carbon nanotubes

A simple and sensitive solid phase extraction (SPE) method on multiwalled carbon nanotubes (MWCNTs) is presented for the determination of cadmium, lead, nickel, copper, and zinc at trace levels combined with flame atomic absorption spectrometry. The effects of parameters like pH, sample volume, sample and eluent flow rates, eluent concentration, and volume and type of eluent on the recovery of trace elements was examined. The metals retained on the nanotube at pH 6.5 as α-benzoin oxime complexes were eluted by 10 mL 2 M HNO₃ in acetone. The influence of matrix ions on the developed method was also evaluated. The preconcentration factor of the method was found to be 50. The detection limits for Cd(II), Pb(II), Ni(II), Cu(II), and Zn(II) were found as 1.7, 5.5, 6.0, 2.3, and 2.4 μg L^?1, respectively. To test the accuracy of the method, the method was applied to TMDA-70 fortified lake water and Spinach 1570A standard reference materials. Addition recovery studies were applied to tap water and cracked wheat samples, and determination of the analyte elements was carried out in some food samples with good results.     

2-Nitroso-1-naphthol as a selective reagent for preconcentration of cobalt by vortex assisted combined with solidification of organic droplet and its determination by flame atomic absorption spectrometry

Highly rapid and selective vortex-assisted liquid–liquid microextraction based on solidification of organic drop has been used for determination of cobalt ion. 2-Nitroso-1-naphthol (2N1N) was used as a selective complexing agent to form stable cobalt–2N1N complex which can be extracted with 1-undecanol at a short time by the assistance of vortex agitator system followed by its determination using flame atomic absorption spectrometry. In vortex assisted, vigorous vortex stream as well as the vibrant effect of vortex system cause very fine droplets of extraction solvent to be produced and extraction occurred at a short time. Some parameters influencing the extraction process such as pH of samples, concentration of 2-nitroso-1-naphthol, extraction solvent volume, extraction time, ionic strength and surfactant addition, as well as interferences were evaluated in detail and optimum conditions were selected. At the optimum conditions, the calibration curve was linear in the range of 15 to 400 μg L^?1 of cobalt ions. The relative standard deviation based on ten replicate analysis of sample solution containing 50 μg L^?1 of cobalt was 3.4 %. The detection limit (calculated as the concentration equivalent to three times of the standard deviation of the blank divided by the slope of the calibration curve after preconcentration) was 5.4 μg L^?1. The accuracy of the proposed method was successfully evaluated by the analysis of certified reference materials. This selective and highly rapid method was used for determination of cobalt ions in different water samples.     

Determination of trace amounts of zirconium in real samples after microwave digestion and ternary complex dispersive liquid–liquid microextraction

In this study, a ternary Zr(IV) system with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) and fluoride was chosen on the basis of dispersive liquid–liquid microextraction method. Zirconium was extracted into the fine droplets of dichlorobenzene as extracting solvent. These drops dispersed as a cloud in the aqueous sample with the help of ultrasonic waves, and the procedure was done. Finally, atomic absorption spectrometry was applied for the determination of zirconium. The effects of different factors that influence complex formation and extraction, such as pH, amounts of complexing agents, type and volume of the extracting solvent, as well as sonication and centrifuging time, were optimized. Under optimum conditions, the calibration curve was linear in the range of 150.0–800.0 ng mL^?1 with a limit of detection of 44.0 ng mL^?1. Relative standard deviation was calculated to be 4.1 % (n?=?7, c?=?400.0 ng mL^?1). The enrichment factor was 80. The proposed method was successfully used to determine the zirconium in several water, wastewater, and soil samples.     

Application of nanoclay for preconcentration of ultra trace amounts of palladium in environmental samples prior to its determination by ETAAS

In the present work, a batch preconcentration technique using nanoclay with 5-(4-dimethylaminobenzylidene)rhodanine coupled with electrothermal atomic absorption spectrometry was developed for the separation and determination of trace amounts of palladium. In this method, the sample solution was stirred with nanoclay as an adsorbent. Then, adsorbed palladium was subsequently eluted with HCl in acetone (1.5 mol L^?1) and, finally, this eluate was injected to electrothermal atomic absorption spectrometry. Under the optimum conditions, the limit of detection and linear dynamic range were found to be 2.6 and 10.0–133 ng L^?1 (in original solution), respectively. Furthermore, the enrichment factor and relative standard deviation of seven replicate determinations were 148 and ±5.1 %, respectively. This suggested method is simple, selective and sensitive and can be applied to the extraction and determination of palladium in water, tea leaves, synthetic sample and certified reference material with satisfactory results.     

A new catalytic oxidation method for sensitive quantification of bromate in flours and bottled water using AgNPs

In this paper, a simple and sensitive spectrophotometric method for the determination of nanomolar level of bromate, based on the catalytic effect of silver nanoparticles on the oxidation of acid red 14 by potassium bromate, is described. The reaction rate was monitored spectrophotometrically by measuring the decrease in absorbance of acid red 14 at 516 nm. The detection limit of the method was 8 ng/mL, and the linear range was between 15 and 130 ng/mL. The effects of acidity, concentration of reactants and reaction time, and external ions were also discussed. The optimum reaction conditions were fixed, and some kinetic parameters determined. The relative standard deviation for the determination of bromate at the concentration of 50 ng/mL was calculated to be 0.996 % (n?=?10). The method has been successfully applied to the determination of bromate in flours and bottled waters.     

Determination of traces of copper and zinc in honeys by the solid phase extraction pre-concentration followed by the flame atomic absorption spectrometry detection

A simple and fast solid phase extraction procedure was developed to pre-concentrate traces of Cu and Zn prior to their determination in honey samples by flame atomic absorption spectrometry. The sample preparation included dissolution of honey samples and the passage (at 20 ml/min) of resulting 10 % m/v solutions (100 ml) through Dowex 50W?×?8-400 resin beds in order to quantitatively retain Cu and Zn and separate them from the glucose and fructose matrix. Enriched Cu and Zn traces were recovered with 5.0 ml of a 3.0 mol/l HCl solution and quantified by flame atomic absorption spectrometry. The procedure proposed was used to analyze sixty nine commercially available and freshly ripened honey samples coming from the Lower Silesia region (Poland). It enabled to measure Cu and Zn within the range of 0.01–1.42 and 0.03–15.38 μg/g, respectively, with precision better than 4 %. Accuracy, assessed on the basis of the recovery test and the comparison of results with those obtained using wet digestion and inductively coupled plasma optical emission spectrometry, was ranged from ?4 % to +6 %. Detection limits of Cu and Zn achieved with this method were 5 and 7 ng/g, respectively.     

Quantification of ultra-trace amounts of copper by using off-line solid phase extraction-flame atomic absorption spectrometric determination through the octadecyl silica-bonded phase membrane (OSPM) C18 disks impregnated with 2,2'-[ethane-1,2-diylbis(thio)]dianiline

This study reports a very selective, easy, and precise method for rapid separation of trace amounts of copper in aqueous samples using octadecyl silica-bonded phase membrane disks modified by 2,2'-[ethane-1,2-diylbis(thio)]dianiline (EDTD) combined with flame atomic absorption spectrometric determination. In addition, the synthesis and spectral characterization of EDTD have been described in detail. All the affecting experimental variables such as pH, amount of modifier, eluent type, sample and eluent flow rate, interfering ions, and disk capacity were also investigated. The target analyte (trace copper) was quantitatively retained at pH?=?4 and eluted with 6.0 mL of 0.5 M HNO₃ at flow rates of 40 and 10 mL min^?1 for analyte passage and elution steps, respectively, through the disks modified with 17.0 mg of EDTD. The proposed method also allows an enrichment factor of about 500 and has a detection limit of 0.005 ng mL^?1. The method has been successfully applied for isolation and determination of copper in different water samples, peppers, and standard alloys.     

Solid phase extractive preconcentration of silver from aqueous samples

N,N-dibutyl-N1-benzoylthiourea (DBBT) impregnated onto a polymeric matrix, Amberlite XAD-16 was prepared. The separation and enrichment of Ag(I) from solution was investigated. Effective extraction conditions were optimized in column methods prior to determination by atomic absorption spectrometry. The optimum pH range for quantitative adsorption is 2-5. Quantitative recovery of Ag was achieved by stripping with 1 mol L(-1) thiourea in 1 mol L(-1) HCl. The sorption capacity of resin is 0.115 mmol Ag+ g(-1) resin. The relative standard deviation and detection limit was 3.1% for 1 microg Ag+ mL(-1) solution and 0.11 microg L(-1), respectively. The method was used for the determination of silver in geological water samples.     

Evaluation of metal contents of household detergent samples from Turkey by flame atomic absorption spectrometry

The concentrations of cadmium, copper, chromium, cobalt, iron, lead, manganese, nickel, and zinc in detergent samples from Kayseri, Turkey were determined by flame atomic absorption spectrometry. HClO₄ (10 mL)/HNO₃ (10 mL) mixture was used for the digestion of household detergent samples. The correctness of the analytical procedures was checked with standard addition–recovery tests in different detergent samples for the investigated metal ions. The concentration ranges of the elements in the detergent samples were found as 17.2–60.1, 11.1–40.1, 2.5–32.3, 8.1–10.5, 7.2–21.6, 9.8–17.9, 1.7–3.8, 12.5–22.5, and 2.0–5.8 μg/g for iron, manganese, zinc, copper, lead, cobalt, cadmium, nickel, and chromium, respectively. The values found in this work were compared with some other studies around the world conducted on detergent samples.     

The use of silica gel modified with allyl 6-methyl-4-phenyl-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate for selective separation and preconcentration of lead in environmental samples

The aim of the present work is the assessment of a new sorbent, prepared using silica gel coated with a pyrimidine derivative (allyl 6-methyl-4-phenyl-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate), for extraction and preconcentration trace amount of lead from different samples prior to determination by flame atomic absorption spectrometry. Common coexisting ions did not interfere with the separation and determination of lead at pH?6, so that lead ion completely adsorbed on the column. The limit of detection based on three times the standard deviation of the blank was found to be 0.53 ng?mL^?1 in original solution. Obtained sorption capacity for 1 g sorbent was 5.0 mg Pb. The linearity was maintained in the concentration range of 0.1–30.0 ng?mL^?1 for the concentrated solution. Eight replicate determinations of 2.0 μg?mL^?1 of lead in the final solution gave relative standard deviation of ±2.6 %. The proposed method was successfully applied to the determination trace amounts of lead in the environmental samples such as carrot, rice, zardchoobe, and real water samples.     

Solid-phase extraction and separation procedure for trace aluminum in water samples and its determination by high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS)

In the present study, a separation/preconcentration procedure for determination of aluminum in water samples has been developed by using a new atomic absorption spectrometer concept with a high-intensity xenon short-arc lamp as continuum radiation source, a high-resolution double-echelle monochromator, and a charge-coupled device array detector. Sample solution pH, sample volume, flow rate of sample solution, volume, and concentration of eluent for solid-phase extraction of Al chelates with 4-[(dicyanomethyl)diazenyl] benzoic acid on polymeric resin (Duolite XAD-761) have been investigated. The adsorbed aluminum on resin was eluted with 5 mL of 2 mol L^-1 HNO₃ and its concentration was determined by high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS). Under the optimal conditions, limit of detection obtained with HR-CS FAAS and Line Source FAAS (LS-FAAS) were 0.49 μg L^?1 and 3.91 μg L^?1, respectively. The accuracy of the procedure was confirmed by analyzing certified materials (NIST SRM 1643e, Trace elements in water) and spiked real samples. The developed procedure was successfully applied to water samples.     

Comparison of unmodified and modified BCR sequential extraction schemes for the fractionation of heavy metals in shrimp aquaculture sludge from Selangor, Malaysia

A study was carried out to investigate the fractionation of Cd, Cr, Cu, Fe, Mn, Pb, and Zn in shrimp aquaculture sludge from Selangor, Malaysia, using original (unmodified) and modified four-steps BCR (European Community Bureau of Reference, now known as the Standards Measurements and Testing Program) sequential extraction scheme. Step 2 of the unmodified BCR procedure (subsequently called Method A) involves treatment with 0.1 M hydroxylammonium chloride at pH 2, whereas 0.5 M hydroxylammonium chloride at pH 1.5 was used in the modified BCR procedure (subsequently called Method B). Metal analyses were carried out by flame atomic absorption spectrometry. A pseudo-total aqua-regia digest of BCR CRM 701 has also been undertaken for quality assurance purposes. The recovery of Method A for all metals studied ranges from 96.14% to 105.26%, while the recovery for Method B ranges from 95.94% to 122.40%. Our results reveal that Method A underestimated the proportion of metals bound to the easily reducible fraction except for copper. Therefore, the potential mobility of these elements is higher than others. Thus, to use this sludge as a fertilizer we have to first find a remediation for reduction of heavy metal contamination.     

Development and application of microwave assisted extraction (MAE) for the extraction of five polycyclic aromatic hydrocarbons in sediment samples in Johannesburg area, South Africa

A microwave-assisted extraction (MAE) method was verified and applied for the extraction of polycyclic aromatic hydrocarbons (PAHs) in sediment samples. Soxhlet extraction was used as the reference method. The optimum MAE was carried out with 20 mL of hexane/acetone (1:1, v/v) mixture in a 1-g sample at 250 W for 20 min. Soxhlet extraction was carried out with 250 mL of dichloromethane:hexane (1:1, v/v) mixture in a 15-g sample for 24 h in a water bath maintained at 60 °C. The collected extracts were both cleaned up, reduced to 1 mL under nitrogen and then injected into an HPLC fluorescence. To increase the sample throughput, simultaneous MAE was performed. The obtained percentage recoveries ranged from 61 to 93 and 88–98 for MAE and SE, respectively. The optimised MAE method was validated using certified reference material. It was then applied to real sediment samples from in and around the greater Johannesburg area. The sediments from Jukskei River were found to be the most polluted while Hartbeespoort Dam sediments were found to be least polluted. The overall order of concentrations for the studied PAHs per site was as follows: Jukskei River?>?Kempton Park?>?Centurion Dams?>?Natalspruit River (PIT)?>?Hartbeespoort Dam.     

Single drop microextraction and gas chromatography–mass spectrometry for the determination of diflufenican, mepanipyrim, fipronil, and pretilachlor in water samples

An analytical method for the determination of diflufenican, mepanipyrim, pretilachlor, and fipronil in water samples was developed using single drop microextraction in the direct immersion mode and gas chromatography–mass spectrometry. A factorial fractionated design of type 2^6–1 at two levels was performed, to study the influence of experimental variables such as ionic strength, pH, agitation speed, extraction time, drop volume, and sample volume. To establish the optimal conditions for the variables that were significant, a Doehlert design was performed. The optimum conditions of extraction were 1 μL of heptane immersed in 4.0 mL of sample with continuous agitation at 500 rpm for 30 min at room temperature. The developed method proved to have good linearity for the range studied. The detection limits were 0.07 μg L^?1 for diflufenican, 0.03 μg L^?1 for mepanipyrim, 0.08 μg L^?1 for pretilachlor, and 1.39 μg L^?1 for fipronil. The method was validated on river water samples, showing the absence of matrix effect and recoveries ranged from 90.1 to 107.8 %. The results show that the method developed is accurate, sensitive, rapid, simple, and low cost, so it is recommended for application in the analysis of these different classes of pesticides in water samples.     

New kinetic-spectrophotometric method for monitoring the concentration of iodine in river and city water samples

A new kinetic method has been developed for the determination of iodine in water samples. The method is based on the catalytic effect of I^? with the oxidation of Indigo Carmine (IC) by KBrO₃ in the sulfuric acid medium. The optimum conditions obtained are 0.16 M sulfuric acid, 1?×?10^?3 M of IC, 1?×?10^?2 M KBrO₃, reaction temperature of 35°C, and reaction time of 80 s at 612 nm. Under the optimized conditions, the method allowed the quantification of I^? in a range of 12–375 ng/mL with a detection limit of 0.46 ng/mL. The method was applied to the determination of iodine in river and city water samples with the satisfactorily results.     

Synthesis, spectral assignment and application of a recently synthesized macrocyclic ionophore to simultaneous pre-concentration and determination of ultra traces of copper and lead by solid phase extraction-flame atomic absorption spectrometry

Ethyl(2-ethylamino)thiophenol-2,6-pyridinedicarboxylate (ETPD) was synthesized from the reaction of disodium pyridine-2,6-dicarboxylate with 1,2-dibromoethane in methanol, followed by treatment with 2-aminothiophenol. The spectral characterization of ETPD is described in detail. This electron-donating agent was successfully utilized for simultaneous enrichment of ultra trace levels of copper and lead in a wide variety of samples. By passing the aqueous solutions through octadecylsilyl bonded phase membrane disks impregnated with 12 mg of ETPD at flow rates of 45 mL min^?1, Cu and Pb were selectively trapped on the disk surface over the pH range 3.0 to 7.0, whereas most other ions were negligibly retained. Numerous chemical parameters affecting sorption and subsequent elution were also investigated. The target ions were stripped from the disk surfaces by reverse flow, at rates of 12 mL min^?1, and were immediately introduced to the nebulizer of an atomic absorption spectrometer. This inexpensive and off-line method offers enrichment factors of 400 and 300 and detection limits of 2.5 and 0.2 μg L^?1 for copper and lead, respectively. The potential applicability of the method was confirmed by its reliable use in quantification of these elements in some real water samples, industrial effluents, three tea samples and peppers, as well as by comparison with graphite furnace atomic absorption spectrometric determinations.     

顶空固相微萃取-气相色谱法测定水中氯苯类化合物

采用顶空固相微萃取（HS －SPME）技术萃取水中6种氯苯类化合物，全面分析对目标物萃取效率的影响因素，并确定萃取试验的最佳条件。用顶空固相微萃取联合气相色谱法（HS －SPME －GC）测定水中6种氯苯类化合物，方法在0.500 ng／L～2.00×10^5 ng／L范围内线性良好，检出限为0.05 ng／L ～2000 ng／L，空白样品加标回收率为69.8％～121％， RSD为4.8％～18.3％。用该方法测定实际水样，平行双样的相对偏差低于20％。