Ionic liquid-based dispersive liquid–liquid microextraction for the separation and preconcentration of lead in water samples prior to FAAS determination without chelating agent

In the present study, an environment-friendly sample preparation method termed ionic liquid-based dispersive liquid–liquid microextraction combined with flame atomic absorption spectrometry has been developed for the determination of Pb(II) ion in water samples prior to flame atomic absorption spectrometry determination. In this method, ionic liquid was used as an extraction solvent instead of the organic solvent used in the conventional dispersive liquid–liquid microextraction (DLLME) assay, and there is no need for a chelating agent. Several variables that may affect extraction efficiencies, including pH, the volume of ionic liquid, the type and volume of disperser solvent, salt addition, and the time for centrifugation and extraction were studied and optimised. Under the optimised conditions, the calibration curve exhibited linearity over the range of 20.0–1000.0 μg L^?1. The enrichment factor and the limit of detection based on 3S_b/m were 35.0 and 5.9 μg L^?1, respectively. Seven replicate determination of a solution containing of 100.0 μg L^?1 Pb(II) ions gave a relative standard deviation of ±2.1%. Finally, the feasibility of the proposed method for Pb(II) determination was assessed by the analysis of certi?ed reference material and various water samples and the satisfactory results were obtained.     

Development of ultrasound-assisted emulsification solidified floating organic drop microextraction for determination of trace amounts of iron and copper in water, food and rock samples

A simple and efficient liquid-phase microextraction technique was developed using ultrasound-assisted emulsification solidified floating organic drop microextraction combined with flame atomic absorption spectrometry, for the extraction and determination of trace amounts of iron and copper in real samples. 2-Mercaptopyridine n-oxide was used as chelating agent and 1-dodecanol was selected as extraction solvent. The factors influencing the complex formation and extraction were optimized. Under optimum conditions, an enrichment factor of ~13 was obtained for both iron and copper from only 6.7 mL of aqueous phase. The analytical curves were linear between 40–800 and 20–1,200 μg L^?1 for iron and copper respectively. Based on three SD of the blank, the detection limits were 8.6 and 4.1 μg L^?1 for iron and copper respectively. The relative SDs for ten replicate measurements of 500 μg L^?1 of metal ions were 2.9 and 1.2 for iron and copper respectively. The proposed method was successfully applied for determination of iron and copper in environmental waters and some food samples including chess, rice, honey and powdered milk. Finally, method validation was made using rock certified reference material. A student’s t test indicated that there was no significant difference between experimental results and certified values.     

Preconcentration of Pb2+ by iron oxide/amino-functionalized silica core–shell magnetic nanoparticles as a novel solid-phase extraction adsorbent and its determination by flame atomic absorption spectrometry

The use of iron oxide/amino-functionalized silica core–shell magnetic nanoparticles for preconcentration of Pb²⁺ followed by its consecutive atomic absorption spectrometry determination is described. Effects of various operating variables, namely, solution pH, initial Pb²⁺ concentration, contact time, adsorbent dosage, sample volume, concentration and volume of desorbing solution, and co-existing ions on solid-phase extraction (SPE) of Pb²⁺ were studied by batch equilibrium technique. The experimental adsorption data were well fitted to the Langmuir isotherm model. The Langmuir adsorption capacity and equilibrium time were found to be 100 mg g^?1 and 20 min, respectively. The adsorption data were also fitted to kinetic pseudo-first-order and pseudo-second-order models. Kinetic studies showed that the adsorption followed pseudo-second-order model. Under the optimal SPE conditions, the enrichment factor, detection limit and relative standard deviation for determination of Pb²⁺ were found to be 211, 1 μg L^?1, and 3.7 % for 50 μg L^?1, respectively. The proposed method was successfully applied to the determination of lead in a real sample with satisfactory results.     

Application of a new nanoporous sorbent for extraction and pre-concentration of lead and copper ions

The authors describe a method for the trace determination of copper (II) and lead (II) in water and fish samples using solid-phase extraction via siliceous mesocellular foam functionalised by dithizone. Siliceous mesocellular was functionalised with dithizone, and the resulting sorbent was characterised by scanning electron microscopy, surface area analysis, thermogravimetric/differential thermal analysis and FTIR. Following solid-phase extraction of target ions by the sorbent, copper and lead ions were quantified by flame atomic absorption spectrometry. Factors affecting the sorption and desorption of target ions by the sorbent were evaluated and optimised. The calibration plot is linear in the 1 – 500 μg L^?1 copper (II) and 3–700 μg L^?1 lead (II) concentration range. The relative recovery efficiency in real sample analysis is in the range from 96 to 102%, and precision varies between 1.7 and 2.8%. It is should be noted that the limits of detection for the copper and lead analysis were 0.8 and 1.6 μg L^?1, respectively. Also, the adsorption capacities for copper and lead ions were 120 and 160 mg g^?1, respectively. The obtained pre-concentration factor for the lead and copper ions by the proposed solid-phase extraction was 75. The method was successfully applied to the determination of low levels of copper (II) and lead (II) in tap, Caspian sea, Persian gulf and lake water and also their detection in fish samples.     

Speciation and determination of chromium ions by dispersive micro solid phase extraction using magnetic graphene oxide followed by flame atomic absorption spectrometry

A selective, simple and fast dispersive micro solid phase extraction method using magnetic graphene oxide (GO) as an efficient sorbent has been developed for the extraction, separation and speciation analysis of chromium ions. The method is based on different adsorption behaviour of Cr(VI) and Cr(III) species onto magnetic GO in aqueous solutions which allowed the selective separation and extraction of Cr(VI) in the pH range of 2.0–3.0. The retained Cr(VI) ions by the sorbent were eluted using 0.5 mL of 0.5 mol L^?1 nitric acid solution in methanol and determined by ?ame atomic absorption spectrometry. Total chromium content was determined after the oxidation of Cr(III) to Cr(VI) by potassium permanganate. All effective parameters on the performance of the extraction process were thoroughly investigated and optimised. Under the optimised conditions, the method exhibited a linear dynamic range of 0.5–50.0 µg L^?1 with a detection limit of 0.1 µg L^?1 and pre-concentration factor of 200. The relative standard deviations of 3.8% and 4.6% (n = 8) were obtained at 25.0 µg L^?1 level of Cr(VI) for intra- and inter-day analysis, respectively. The method was successfully applied to the speciation and determination of Cr(VI) and Cr(III) in environmental water samples.     

Occurrence of cytostatic compounds in hospital effluents and wastewaters,determined by liquid chromatography coupled to high-resolution mass spectrometry

The occurrence of 26 commonly used cytostatic compounds in wastewaters was evaluated using an automated solid-phase extraction (SPE) method with liquid chromatography–high-resolution mass spectrometry (LC–HRMS). Detection was optimized using Oasis HLB SPE cartridges at pH 2. Two hospital effluents and their two receiving wastewater treatment plants were sampled over five days. In hospital effluents, eight cytostatics were detected at levels up to 86.2 μg L^?1 for ifosfamide, 4.72 μg L^?1 for cyclophosphamide, and 0.73 μg L^?1 for irinotecan, the three most relevant compounds identified. Cyclophosphamide and megestrol acetate were found in wastewaters at concentrations up to 0.22 μg L^?1 for the latter. The predicted environmental concentrations (PEC) in sewage effluents of ifosfamide (2.4–4.3 ng L^?1), capecitabine (11.5–14.2 ng L^?1), and irinotecan (0.4–0.6 ng L^?1), calculated from consumption data in each hospital, published excretion values for the target compounds, and wastewater elimination rates, were in agreement with experimental values.     

Determination of Zn(II) in rock and vegetable samples after acidic digestion followed by ultrasound-assisted solid-phase extraction with reduced graphene oxide as novel sorbent,in combination with flame atomic absorption spectrometry

Graphene, a novel class of carbon nanostructures, has great promise for use as sorbent materials because of its ultrahigh specific surface area. A new method using reduced graphene oxide (RGO) as sorbent was developed for the preconcentration of trace amounts of zinc (Zn) to its determination by flame atomic absorption spectrometry. Zinc could be adsorbed quantitatively on RGO in the pH range of 1–9, and then eluted completely with 0.5 mL of 0.1 mol L^?1 HCl. Some effective parameters on the extraction were selected and optimized. Under optimum conditions, the calibration graph was linear in the concentration range of 0.2–15 μg L^?1 with a detection limit of 0.14 μg L^?1 with an enrichment factor of 100.12. The relative standard deviation for ten replicate measurements of 10 μg L^?1 of Zn was 0.58 %, respectively. The proposed method was successfully applied in the analysis of rock and vegetable samples. Good spiked recoveries over the range of 99.9–100 % were obtained. This work not only proposes a useful method for sample preconcentration, but also reveals the great potential of graphene as an excellent sorbent material in analytical processes.     

Graphene oxide-packed micro-column solid-phase extraction combined with flame atomic absorption spectrometry for determination of lead (II) and nickel (II) in water samples

A sensitive and simple method has been established for simultaneous preconcentration of trace amounts of Pb (II) and Ni (II) ions in water samples prior to their determination by flame atomic absorption spectrometry. This method was based on the using of a micro-column filled with graphene oxide as an adsorbent. The influences of various analytical parameters such as solution pH, adsorbent amount, eluent type and volume, flow rates of sample and eluent, and matrix ions on the recoveries of the metal ions were investigated. Using the optimum conditions, the calibration graphs were linear in the range of 7–260 and 5–85 μg L^?1 with detection limits (3S_b) of 2.1 and 1.4 μg L^?1 for lead and nickel ions, respectively. The relative standard deviation for 10 replicate determinations of 50 μg L^?1 of lead and nickel ions were 4.1% and 3.8%, respectively. The preconcentration factors were 102.5 and 95 for lead and nickel ions, respectively. The adsorption capacity of the adsorbent was also determined. The method was successfully applied to determine the trace amounts of Pb (II) and Ni (II) ions in real water samples. The validation of the method was also performed by the standard reference material.     

Preconcentration of beryllium via octadecyl silica gel microparticles doped with aluminon, and its determination by flame atomic absorption spectrometry

A simple and sensitive method is presented for solid phase extraction (SPE) and preconcentration of trace quantities of beryllium using octadecyl silica gel modifed with aurin tricarboxylic acid (aluminon). Beryllium is then determined by flame atomic absorption spectroscopy. Parameters affecting SPE such as pH, sample solution and eluent flow rate, type, concentration and volume of eluent, interfering ions and breakthrough volume, were investigated. Under optimal conditions, the beryllium ions were retained on the sorbent at pH 6–6.7, while 3.0 mL of 0.05 mol L^?1 HNO₃ is sufficient to elute the ions. The limit of detection (LOD) based on 3σ was 0.8 µg L^?1 for 250 mL sample solution and 5 mL 0.05 mol L^?1 HNO₃ as eluent. The LOD can reach 0.1 µg L^?1 for 1 L sample solution and 3 mL of 0.05 mol L^?1 HNO₃. The accuracy and precision (RSD %) of the method is >90% and <10%, respectively. The method was applied to the determination of beryllium in aqueous samples.     

Ionic liquid-based dispersive liquid–liquid microextraction for determination of trace amounts of iron in water, rock and human blood serum samples

A green and sensitive dispersive liquid-phase microextraction procedure based on room-temperature ionic liquid (1-hexyl-3-methylimidazolium hexafluorophosphate) for preconcentration and determination of total iron in real samples prior to flame atomic absorption spectrometry was developed. 2-Mercaptopyridine-N-oxide (pyrithione) and ethanol were used as complexing agent and dispersive solvent in the proposed method, respectively. The factors influencing the extraction were optimized. Under optimum conditions, the enhancement factor of 15 was obtained from only 11.35 mL of aqueous phase. The linear dynamic range and the detection limit were 10.0–700 and 2.4 μg L^?1, respectively. The relative standard deviation (RSD) for ten replicate measurements of 500 μg L^?1 of iron is 3.1 %. The developed method has been successfully applied for the determination of iron in water samples, human blood serum and rock certified reference material with high efficiency.     

Separation and preconcentration of gold and palladium ions with a carboxylated pillar[5]arene derived sorbent prior to their determination by flow injection FAAS

We report on the use of a water-insoluble pillar[5]arene derivative carrying ten carboxy groups as an adsorbent, packed in a glass microcolumn, for the separation and preconcentration of trace gold (Au) and palladium (Pd). Sample pH, sample loading time, sample flow rate, eluent concentration, and eluent flow rate were optimized. Effects of potentially interfering metal ions that are commonly encountered in soil were also investigated. Under the optimized conditions, the enrichment factors for Au and Pd are 12 and 16, respectively. Flow injection in combination with flame atomic absorption spectrometry was then applied for the quantitation of the elements. The analytical range is linear in the range between 0.05 and 1 μg mL^?1 for both Au and Pd. The limits of detection are 15.9 μg L^?1 for Au and 16.0 μg L^?1 for Pd, with relative standard deviations (for n?=?11) of 0.7 % (Au) and 0.4 % (Pd), respectively. The accuracy of the method was validated using certified reference materials (coal and ash) and geological samples. Figure

A pillar[5]arene derivative carrying ten carboxy groups was used for the adsorption of Au(III) and Pd(II) ions which then were determined by flow-injection FAAS. After optimization, the method was successfully applied to the determination of these ions in certified reference materials and geological samples     

Synthesis and characterisation of novel chelating resin for selective preconcentration and trace determination of Pb(II) ions in aqueous samples by innovative microsample injection system coupled flame atomic absorption spectrometry

Expanded polystyrene (EPS) foam waste (white pollutant) was utilised for the synthesis of novel chelating resin i.e. EPS-N = N-α-Benzoin oxime (EPS-N = N-Box). The synthesised resin was characterised by FT-IR spectroscopy, elemental analysis, and thermogravimetric analysis. A selective method for the preconcentration of Pb(II) ions on EPS-N = N-Box resin packed in mini-column was developed. The sorbed Pb(II) ions were eluted with 5.0 mL of 2.0 mol L^?1 HCl and determined by microsample injection system coupled flame atomic absorption spectrometry (MIS-FAAS). The average recovery of Pb(II) ions was achieved 95.5% at optimum parameters such as pH 7, resin amount 400 mg, flow rates 1.0 mL min^?1 (of eluent) and3.0 mL min^?1 (of sample solution). The total saturation capacity of the resin, limit of detection (LOD) and limit of quantification (LOQ) of Pb(II) ions were found to be 30 mg g^?1, 0.033 μg L^?1 and 0.107 μg L^?1, respectively with preconcentration factor of 300. The accuracy, selectivity and validation of the method was checked by analysis of sea water (BCR-403), wastewater (BCR-715) and Tibet soil (NCS DC-78302) as certified reference materials (CRMs). The proposed method was applied successfully for the trace determination of Pb(II) ions in aqueous samples.     

The separation–preconcentration and determination of ultra-trace gold in water and solid samples by dispersive liquid–liquid microextraction using 4-ethyl-1(2-(4-(4-nitrophenyl)piperazin-1-yl)acetyl)thiosemicarbazide) as chelating agent and flame atomic absorption spectrometry

A selective separation and preconcentration method for the determination of gold ions in water and ore samples has been developed using dispersive liquid–liquid microextraction, followed by flame atomic absorption spectrometry. 4-Ethyl-1(2-(4-(4-nitrophenyl)piperazin-1-yl)acetyl)thiosemicarbazide) (NPPTSC) has been used for the first time as new chelating reagent. A mixture of ethanol (dispersive solvent) and carbon tetrachloride (extraction solvent) was used. Some parameters affecting the extraction procedure including the type and volume of the extracting and dispersive solvents, HNO₃ concentration, the chelating agent amount, volume of sample, and foreign ions have optimized. Also, the complex formation between gold ions and the ligand has been investigated in a methanol–water solution (1:1) using UV–visible spectrometry. The spectrophotometric titration data showed that of Au–NPPTSC complex composition was found to be 3:2. After optimizing the instrumental and experimental parameters, we achieved a detection limit of 1.5 µg L^?1, a preconcentration factor of 50, and a linear dynamic range of 10.0–400.0 µg L^?1. The relative standard deviation obtained 2.1% at 50 µg L^?1 for gold ions (n = 10). The proposed method was successfully performed for the determination of gold in certified reference material, environmental water, and ore samples.     

Selective extraction and preconcentration of ultra-trace amounts of arsenic(V) ions using carbon nanotubes as a novel sorbent

In the present study, multiwalled carbon nanotubes (MWCNTs) as solid phase extraction sorbent were developed for preconcentration of arsenic(V) species prior to graphite furnace atomic absorption spectrometry (GFAAS) determination. Arsenic(V) was selectively sorbed on the packed column with MWCNTs within a pH 9.5 in the presence of 2-(5-bromo-2-pyridylazo)-5-diethyl amino phenol (5-Br-PADAP). The adsorbed species was then desorbed with 1 mL of 2.0 M HNO₃. Experimental parameters including pH, sample volume and flow rate, type, volume and concentration of eluent that influence the recovery of the arsenic(V) species were optimised. Under the optimised conditions, the calibration curve was linear in the range of 0.2–10.0 µg L^?1 with detection limit of 0.016 µg L^?1. The relative standard deviations (RSD) for seven replicate determinations at 1.0 µg L^?1 level of arsenic was 6.69%. The proposed method was successfully applied to the determination of arsenic in water samples and certified reference material (NIST RSM 1643e).     

Indirect quantification of trace levels cyanide in environmental waters through flame atomic absorption spectrometry coupled with cloud point extraction

Cloud point extraction (CPE) has been used for the preconcentration and indirect quantification of cyanide after the formation of a ion-associate complex with 3-amino-7-diethylamino-8,9-benzo-2-phenoxazine chloride (Nile blue, NB⁺) in the presence of copper (II) ions, and later analysis by flame atomic absorption spectrometry (FAAS) using polyethyleneglycolmono-p-nonylphenylether (PONPE 7.5) as extracting surfactant. The chemical variables affecting the separation phase and the viscosity affecting the detection process were optimized. At pH 5.5, preconcentration of only 50 mL of sample in the presence of 0.04 % (w/v) PONPE 7.5 and 5.64 × 10^?5 mol L^?1 Nile blue permitted the detection of 3.75 μg L^?1 cyanide. The enhancement factor was 64.7 for cyanide. The proposed method was successfully applied to the determination of free cyanide in environmental water samples. The method was compared with the pyridine–barbituric acid method and the paired t test was used to determine whether the results obtained by the two methods differ significantly.     

Determination of Antimony(III) and Total Antimony in Aqueous Samples by Electrothermal Atomic Absorption Spectrometry After Dispersive Liquid–Liquid Microextraction (DLLME)

Dispersive liquid–liquid microextraction (DLLME) technique combined with electrothermal atomic absorption spectrometry (ET-AAS) was proposed for determination of antimony(III) and total antimony at very low concentrations in water samples. The N-benzoyl-N-phenylhydroxylamine (BPHA) was used as a chelating agent, and chloroform and ethanol were used as extraction and disperser solvents, respectively. The effect of various experimental parameters on the extraction and determination was investigated. The detection limits (3σ) were 0.005 μg L^?1 for Sb(III) and 0.008 μg L^?1 for total Sb. The developed method was applied successfully to the determination of Sb(III) and total Sb in natural water samples.     

Schiff base-functionalised styrofoam resin for preconcentration of metal ions in wastewater and wastewater-irrigated vegetables samples

Polystyrene (PS) was extracted from styrofoam waste and functionalised with schiff base, N,N-bis(salicylidene)cyclohexanediamine (SCHD) through an azo spacer. The resin was characterised and used for preconcentration of Pb(II), Ni(II) and Cd(II) ions prior to their trace determinations by microsample injection system–coupled flame atomic absorption spectrometry (MIS-FAAS). The recoveries of studied metal ions were achieved ≥96.0% with relative standard deviation (RSD) ≤4.5 at optimum parameters: pH 8; resin amount 300 mg; flow rates 3.0 mL min^?1 of sample solution; and 2.0 mL min^?1 of eluent (2.0 mol L^?1 HNO₃). The limits of detection (LODs) and limits of quantification (LOQs) were found to be 0.32, 0.23 and 0.21 and 1.10, 0.78 and 0.69 μg L^?1, respectively, with preconcentration factors (PFs) of 500, 800 and 1000, respectively. The linear ranges of the method were 1–40, 1–25 and 1–20 μg L^?1 for Pb(II), Ni(II) and Cd(II) ions, respectively. The accuracy and validation of the method were evaluated by analysis of certified reference materials (CRMs). The method was successfully applied for preconcentration of studied metal ions in wastewater and wastewater-irrigated vegetable samples.     

Single Laboratory Validation of a Method for the Determination of Total Inorganic Arsenic by Hydride Generation Atomic Absorption Spectrometry

The purpose of this study consists in reporting of single laboratory validation of a method for the determination of total inorganic arsenic by hydride generation atomic absorption spectrometry from natural and residual water samples. Applicability, fitness for purpose, selectivity, and sensitivity were discussed. A calibration study was realized, linear working range (0.4–4 μg·L^?1), detection (0.11 μg·L^?1), and quantification (0.38 μg·L^?1) limits being determined. It was also proven that the method is accurate and precise. Following the bottom-up approach measurement, uncertainty was estimated (method validation data were used).     

Use of Surfactant as Mobile Phase Additive in LC for Simultaneous Determination of Metal-Pyrrolidine Dithiocarbamate Chelates

Reversed phase liquid chromatography using UV detection was developed for the simultaneous analysis of Hg(II), Pb(II), Cd(II), Ni(II), Fe(III) and V(V) ions after their complexation with pyrrolidine-dithiocarbamate (PDC). Optimum chromatographic conditions were a μ-Bondapak C₁₈ column and an isocratic mobile phase consisting of 40 mmol L^?1 SDS, 34 mmol L^?1 TBABr and 68% acetonitrile in 10 mmol L^?1 phosphate buffer pH 3.5. The separation of six PDC complexes was achieved within 8 min. Analytical performances and method validation were investigated. The detection limits ranged from 0.16 μg L^?1(Fe(III)) to 5.40 μg L^?1(Pb(II)). Recoveries obtained for all the studied samples including tap water, whole blood and vegetables were 72–98%. The results obtained from the proposed method were not significantly different compared to those obtained from atomic absorption spectrometry (P = 0.05).     

Magnetic solid-phase extraction to preconcentrate trace amounts of gold (III) using nickel ferrite magnetic nanoparticles

In this research, nickel ferrite (NiFe₂O₄) magnetic nanoparticles were synthesised by a simple method and applied as sorbent for magnetic solid-phase extraction of trace amounts of Au(III) from water samples. Detection in this technique was performed by flame atomic absorption spectrometry. The effects of sample pH, amount of sorbent, extraction time, desorption solvent and its volume on the extraction process were optimised. The effects of interfering ions on the recovery of the analyte were also evaluated in model solutions. The best results were obtained at pH 6.5 with 5 mL of eluent solution (0.1 mol L^?1 sodium thiosulphate) and an extraction time of 30 min. Under optimal conditions, the sorption capacity was 34.6 mg g^?1. Also, enhancement factor (for 100 mL of sample solution) was found to be 19.3. The calibration graph was linear in the range of 4.4–800.0 µg L^?1 gold concentration and the limit of detection was 1.32 µg L^?1. The relative standard deviation of the method (for n = 8) was 1.57%. The method was successfully applied to the extraction of Au(III) from water samples.