Solidified floating organic drop microextraction–electrothermal atomic absorption spectrometry for ultra trace determination of antimony species in tea, basil and water samples

Solidified floating organic drop microextraction was applied as a separation/preconcentration step prior to the electrothermal atomic absorption spectrometric (ETAAS) determination of ultra trace of antimony species. The method was based on the formation of an extractable complex between Sb(III) and ammonium pyrrolidinedithiocarbamate at pH ~ 5, while Sb(V) was remained in the aqueous phase. The antimony extracted into 1-undecanol was determined by ETAAS. Total antimony was determined after the reduction of Sb(V) to Sb(III) with potassium iodide and ascorbic acid. The amount of Sb(V) was determined from the difference of concentration of total antimony and Sb(III). Under the optimum conditions an enhancement factor of 437.5 and a detection limit of 5.0 ng L^?1for the preconcentration of 25 mL of sample was achieved. The relative standard deviation at 300 ng L^?1 of antimony was found to be 3.5 % (n = 6). The proposed method was successfully applied to the determination of antimony in tea, basil and natural water samples.     

Speciation of chromium in water samples using dispersive liquid–liquid microextraction and flame atomic absorption spectrometry

A novel method for preconcentration is described for chromium speciation at microgram per liter to sub-microgram per liter levels. It is based on selective complex formation of both Cr(VI) and Cr(III) followed by dispersive liquid–liquid microextraction and determination by microsample introduction-flame atomic absorption spectrometry. Effects influencing complex formation and extraction (such as pH, temperature, time, solvent, salinity and the amount of chelating agent) have been optimized. Enrichment factors up to 275 and 262 were obtained for Cr(VI) and total Cr, respectively. The calibration graph is linear from 0.3 to 20 µg L^?1, and detection limits are 0.07 and 0.08 µg L^?1 for Cr(VI) and total Cr, respectively. Relative standard deviations (RSDs) were obtained to be 2.0% for Cr(VI) and 2.6% for total Cr (n?=?7).     

Dispersive liquid–liquid microextraction based on the solidification of floating organic drop followed by inductively coupled plasma-optical emission spectrometry as a fast technique for the simultaneous determination of heavy metals

A simple, rapid and efficient dispersive liquid–liquid microextraction based on the solidification of floating organic drop (DLLME–SFO) method, followed by inductively coupled plasma-optical emission spectrometry (ICP-OES) was developed for the simultaneous preconcentration and determination of heavy metals in water samples. One variable at a time method was applied to select the type of extraction and disperser solvents. Then, an orthogonal array design (OAD) with OA₁₆ (4⁵) matrix was employed to study the effects of different parameters on the extraction efficiency. Under the best experimental conditions (extraction solvent: 140 μL of 1-undecanol; disperser solvent: 2.0 mL of acetone; ligand to metal mole ratio: 20; pH: 6 and without salt addition), the enhancement factor ranged from 57 to 96. The calibration graphs were linear in the range of 0.5–250 μg L⁻¹ for Mn, 1.25–250 μg L⁻¹ for Cr, Co and Cu with correlation coefficient (r) better than 0.990. The detection limits were between 0.1 and 0.3 μg L⁻¹. Finally, the developed method was successfully applied to extraction and determination of the mentioned metal ions in the tap, sea and mineral water samples and satisfactory results were obtained.     

Determination of As(III) using developed dispersive liquid–liquid microextraction and flame atomic absorption spectrometry

The method relies on selective complexation of As(III) with a suitable chelating agent followed by dispersive liquid–liquid microextraction (DLLME) method. Flame atomic absorption spectrometry (FAAS) equipped with microsample introduction system was utilised for determination of As(III). 1-Undecanol and acetone were used as extraction solvent and disperser solvent respectively. Some effective parameters on complex formation and extraction have been optimised. Under the optimum conditions, the enrichment factor of 108 for As(III) was obtained from 9.8?mL of water samples. The calibration graph was linear in the range of 2–15?µg?L^?1 with detection limits of 0.60?µg?L^?1 for As(III). The relative standard deviation (R.S.D.) for ten replicate measurements of 5.00?µ?gL^?1 of As(III) was 6.2%. Operation simplicity and high enrichment factors are the main advantages of DLLME for the determination of As(III) without necessity for hydride generation in water samples.     

Sequential injection ionic liquid dispersive liquid–liquid microextraction for thallium preconcentration and determination with flame atomic absorption spectrometry

A novel, automatic on-line sequential injection dispersive liquid-liquid microextraction (SI-DLLME) method, based on 1-hexyl-3-methylimidazolium hexafluorophosphate ([Hmim][PF(6)]) ionic liquid as an extractant solvent was developed and demonstrated for trace thallium determination by flame atomic absorption spectrometry. The ionic liquid was on-line fully dispersed into the aqueous solution in a continuous flow format while the TlBr(4)(-) complex was easily migrated into the fine droplets of the extractant due to the huge contact area of them with the aqueous phase. Furthermore, the extractant was simply retained onto the surface of polyurethane foam packed into a microcolumn. No specific conditions like low temperature are required for extractant isolation. All analytical parameters of the proposed method were investigated and optimized. For 15 mL of sample solution, an enhancement factor of 290, a detection limit of 0.86 μg L(-1) and a precision (RSD) of 2.7% at 20.0 μg L(-1) Tl(I) concentration level, was obtained. The developed method was evaluated by analyzing certified reference materials while good recoveries from environmental and biological samples proved that present method was competitive in practical applications.     

Dissolved carbon dioxide flotation-assisted in-syringe dispersive liquid–liquid microextraction coupled with microsampling flame atomic absorption spectrometry for selective determination of palladium in water samples

Dissolved carbon dioxide flotation-assisted in-syringe dispersive liquid–liquid microextraction (DCF-IS-DLLME) followed by microsampling flame atomic absorption spectrometry was developed as a simple, inexpensive and fast method for extraction and determination of Pd(II). In the proposed approach, N,N′-bis (naphthylideneimino) diethylenetriamine (NAPdien) was utilized as a selective complexing reagent for Pd(II) ion. Several influential factors on the extraction efficiency including types and volumes of extraction and disperser solvents, pH of the sample solution, concentration of NAPdien and interfering ions were studied. By applying the optimal conditions, a preconcentration factor of 28.7 and limit of detection of 2.5 ng mL^?1 were provided by the proposed method. Linearity was in the range of 10–400 ng mL^?1 with a correlation coefficient (R ²) of 0.9968. Intra-day RSD% values for five repetitive measurements of the spiked solutions at the concentrations of 20 and 100 ng mL^?1 were 5.2 and 2.4%, respectively, whereas it was obtained within the range of 3.6–18.6% for the real samples. Inter-day RSD% values of the spiked solutions were found to be 9.6 and 8.7%, respectively. The results demonstrated that except for Fe²⁺ and Fe³⁺, no remarkable interfering effect was created by the other studied ions for determination of Pd(II) so that the tolerance limits (W _Ion/W _Pd(II)) of the major cations and anions were in the range of 1000–10,000. Finally, DCF-IS-DLLME was successfully applied for determination of Pd(II) in different water samples and the obtained relative recoveries in the range of 94.5–105% illustrated favorable accuracies for the proposed method.     

Tandem dispersive liquid–liquid microextraction coupled with micro-sampling flame atomic absorption spectrometry for rapid determination of lead(II) and cadmium(II) ions in environmental water samples

ABSTRACT

Tandem dispersive liquid liquid microextraction coupled with micro - sampling flame atomic absorption spectrometry for rapid determination of lead2 and cadmium2 ions in environmental water samples. A simple method termed as tandem dispersive liquid–liquid microextraction coupled with micro-sampling flame atomic absorption spectrometry is used for determination of the lead(II) and cadmium(II) ions in different environmental water samples. According to the proposed method, the target analytes are extracted from an aqueous sample solution (10 mL) into a micro-volume of an organic solvent, and then they are selectively back-extracted into an aqueous acceptor solution (150 μL) to increase the compatibility of the extractant phase with a final analyser system and provide a suitable enrichment factor. The developed method is very fast, implemented in just about 7 min, and provides a high sample clean-up. The factors influencing the extraction efficiency including the type and volume of the organic solvent, pH and volume of the acceptor solution, and number of extractions are thoroughly examined and optimised. Under the optimal experimental conditions, the developed method provides a good linearity (in the range of 0.4–300 ng mL^?1 (R² ≥ 0.994)), and low limits of detection (in the range of 0.07–0.31 ng mL^?1). Finally, the method is successfully applied for the direct determination of the understudied analytes in the river, dam, and well water samples.     

Analysis of eight pyrethroids in water samples by liquid–liquid microextraction based on solidification of floating organic droplet combined with gas chromatography

A novel method was developed for the determination of eight pyrethroids in water samples by liquid–liquid microextraction based on solidification of floating organic droplets followed by gas chromatography with electron capture detection. The type and volume of the extraction solvents, extraction time, sample solution temperature, stirring rate and ionic strength were studied and optimized. Under the optimum conditions, enrichment factors ranged from 824 to 1,432, and the limit of detection range from 2.0 to 50 ng?L^?1. The calibration graph is linear from 0.15 to 80 μg?L^?1 for cyfluthrin, fenvalerate, fluvalinate and deltamethrin, 0.09 to 80 μg?L^?1 for fenpropathrin, 0.006 to 80 μg?L^?1 for lambda-cyhalothrin, 0.026 to 80 μg?L^?1 for permethrin, 0.01 to 80 μg?L^?1 for cypermethrin. The correlation coefficients (r) varied from 0.9961 to 0.9988. The method was successfully applied to the determination of pyrethroid pesticide residues in tap water, well water, reservoir water, and river water. Recoveries ranged from 79.0% to 113.6%, and relative standard deviations are between 4.1% and 8.7%.     

Efficient determination of some potentially toxic metal ions from real samples via modified nano-γ-alumina-based solid-phase extraction followed by flame atomic absorption spectrometric analysis

In the current research work, trace amounts of the Ni(II), Cu(II), Ag(I) and Zn(II) ions in water, cabbage and pomegranate juice were determined via the solid-phase extraction approach based on a new selective adsorbent in the continuous mode followed by flame atomic absorption spectrometry. This efficient and safe sorbent was easily prepared from the immobilisation of 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-BrPADAP), as a selective chelating agent, onto nano-γ-alumina coated with sodium dodecyl sulphate. Nano-γ-alumina was successfully synthesised by the solution combustion procedure and was subsequently analysed by various techniques including SEM, XRD and BET. The parameters involved in the metal ions extraction including the sample pH and volume, amount of sorbent, flow rates of the sample and the eluent, and type and concentration of the eluting agent were optimised. Under the optimal operating conditions, the proposed sample preparation method provided the good linear dynamic ranges (LDRs) 6–300, 4–300, 4–110 and 4–300 µg L^?1 for the Ni(II), Cu(II), Ag(I) and Zn(II) ions, respectively, with the correlation of determinations (R²s) higher than 0.99. The detection limit (LOD) and repeatability (RSD%) values (n = 8) obtained were found to be in the ranges of 1.50–2.00 µg L^?1 and 4.44–5.52%, respectively. The calculated enrichment factors were found to be 166.6, 166.6, 200 and 200 for the Cu(II), Ag(I), Ni(II) and Zn(II) ions, respectively. According to the adsorption studies, the Freundlich isotherm and the pseudo-second-order model showed reasonable fits to the experimental data. Also, thermodynamic studies demonstrated that the adsorption process was spontaneous and exothermic.     

Determination of carbamazepine in formulation samples using dispersive liquid–liquid microextraction method followed by ion mobility spectrometry

A simple, sensitive, fast and efficient method based on dispersive liquid–liquid microextraction (DLLME) followed by ion mobility spectrometry (IMS) has been proposed for preconcentration and trace detection of carbamazepine (CBZ) in formulation samples. In this method, 1 mL of methanol (disperser solvent) containing 80 μL of chloroform (extraction solvent) was rapidly injected by a syringe into a sample. After 5 min centrifugation, the preconcentrated carbamazepine in the organic phase was determined by IMS. Development of DLLME procedure includes optimization of parameters influencing the extraction efficiencies such as kind and volume of extraction solvent, disperser solvent and salt addition, centrifugation time and pH of the sample solution. The proposed method presented good linearity in the range of 0.05–10 μg mL^?1 and the detection limit was 0.025 μg mL^?1. The repeatability of the method expressed as relative standard deviation was 6 % (n = 5). This method has been applied to the analysis of carbamazepine formulation samples with satisfactory relative recoveries ≤75 %.     

Dispersive liquid–liquid microextraction using the freezed floating organic drop for rapid,fast, and sensitive determination of lead

A rapid, simple, and sensitive method was developed for lead preconcentration and separation in various real samples by dispersive liquid–liquid microextraction based on the freezing of floating organic drop. In this method, a suitable extraction solvent dissolved in a dispersive solvent was quickly syringed into the water sample so that the solution became turbid. Then, two phases were separated by centrifugation. The floating extractant droplet can be easily solidified on an ice bath and taken out of the water sample. Then, it can be liquefied instantly at room temperature, and analyte can be determined in it. In the creation of a hydrophobic complex with lead, 1-(2-pyridylazo)-2-naphthole (PAN) was used as the chelating agent. 1-Undecanol and acetone were used as extraction and disperser solvent. To achieve the highest recovery, some factors (type and volume of dispersive and extraction solvent, pH, PAN concentration, and salt concentration) were optimised. Under optimised conditions (pH = 9, 1.0 × 10^–3 mol L^?1 PAN, 15% w/v NaCl, 100 µL 1-undecanol, and 0.3 mL acetone), the lead calibration graph was linear from 1.5 to 80 μg L^?1. The detection limit and preconcentration factor were 0.5 μg L^?1 and 50, respectively. Lead was successfully determined in water and food (spinach, rice, potato, carrot, and black tea bag) samples by this method.     

Air-assisted liquid–liquid microextraction by solidifying the floating organic droplets for the rapid determination of seven fungicide residues in juice samples

A novel air assisted liquid–liquid microextraction using the solidification of a floating organic droplet method (AALLME-SFO) was developed for the rapid and simple determination of seven fungicide residues in juice samples, using the gas chromatography with electron capture detector (GC-ECD). This method combines the advantages of AALLME and dispersive liquid–liquid microextraction based on the solidification of floating organic droplets (DLLME-SFO) for the first time. In this method, a low-density solvent with a melting point near room temperature was used as the extraction solvent, and the emulsion was rapidly formed by pulling in and pushing out the mixture of aqueous sample solution and extraction solvent for ten times repeatedly using a 10-mL glass syringe. After centrifugation, the extractant droplet could be easily collected from the top of the aqueous samples by solidifying it at a temperature lower than the melting point. Under the optimized conditions, good linearities with the correlation coefficients (γ) higher than 0.9959 were obtained and the limits of detection (LOD) varied between 0.02 and 0.25 μg L⁻¹. The proposed method was applied to determine the target fungicides in juice samples and acceptable recoveries ranged from 72.6% to 114.0% with the relative standard deviations (RSDs) of 2.3–13.0% were achieved. Compared with the conventional DLLME method, the newly proposed method will neither require a highly toxic chlorinated solvent for extraction nor an organic dispersive solvent in the application process; hence, it is more environmentally friendly.     

Preconcentration and determination of low amounts of cobalt in black tea,paprika and marjoram using dispersive liquid–liquid microextraction and flame atomic absorption spectrometry

A dispersive liquid–liquid microextraction (DLLME) method for separation/preconcentration of ultra trace amounts of Co(II) and its determination with FAAS was developed. The DLLME behavior of Co(II) using Aliquat 336-chloride as ion pairing agent was systematically investigated. The factors influencing the ion pair formation and extraction by DLLME method were optimized. Under the optimized conditions for 150 µL of extraction solvent (carbon tetrachloride), 1.5 mL disperser solvent (acetonitrile) and 5 mL of sample, the enrichment factor was 30. The detection limit was 5.6 µg L^?1 and the RSD for replicate measurements of 1 mg L^?1 was 1.32 %. The calibration graph using the preconcentration system for cobalt was linear from 40 to 400 µg L^?1 with a correlation coefficient of 0.999. The proposed method was successfully applied for determination of cobalt in black tea, paprika and marjoram real samples.     

Simple approach based on ultrasound-assisted emulsification-microextraction for determination of polibrominated flame retardants in water samples by gas chromatography–mass spectrometry

A simple, efficient, innovative and environmentally friendly analytical technique was successfully applied for the first time for the extraction and preconcentration of polybrominated diphenyl ethers (PBDEs) from water samples. The PBDEs selected for this work were those most commonly found in the literature in natural water samples: 2,2′,4,4′-tetraBDE (BDE-47), 2,2′,4,4,5-pentaBDE (BDE-99), 2,2′,4,4,6-pentaBDE (BDE-100) and 2,2,4,4′,5,5′-hexaBDE (BDE-153). The extracted PBDEs were separated and determined by gas chromatography–mass spectrometry (GC–MS). The extraction/preconcentration technique is based on ultrasound-assisted emulsification-microextraction (USAEME) of a water-immiscible solvent in an aqueous medium. Several variables including, solvent type, extraction time, extraction temperature and matrix modifiers were studied and optimized over the relative response the target analytes. Chloroform was used as extraction solvent in the USAEME technique. Under optimum conditions, the target analytes were quantitatively extracted achieving enrichment factors (EF) higher than 319. The detection limits (LODs) of the analytes for the preconcentration of 10 mL sample volume were within the range 1–2 pg mL⁻¹. The relative standard deviations (RSD) for five replicates at 10 pg mL⁻¹ concentration level were <10.3%. The calibration graphs were linear within the concentration range of 5–5000 pg mL⁻¹ for BDE-47 and BDE-100; and 5–10,000 pg mL⁻¹ for BDE-99 and BDE-153, respectively. The coefficients of estimation were ≥0.9985. Validation of the methodology was performed by standard addition method at two concentration levels (10 and 50 pg mL⁻¹). Recovery values were ≥96%, which showed a successful robustness of the analytical methodology for determination of picogram per milliliter of PBDEs in water samples. Significant quantities of PBDEs were not found in the analyzed samples.     

Trace analysis of polycyclic aromatic hydrocarbons in suspended particulate matter by accelerated solvent extraction followed by gas chromatography–mass spectrometry

An analytical procedure based on extraction by accelerated solvent extraction (ASE) followed by gas chromatography–mass spectrometry (GC/MS) analysis has been developed for the determination of particulate polycyclic aromatic hydrocarbons (PAHs) from large-volume water samples (20 L). The effect of temperature and number of cycles on the efficiency of ASE was investigated: the best results were obtained by using a temperature of 100°C and one static cycle. A mixture of hexane/acetone 1:1 (v/v) was used as extraction solvent. Mean total method recovery under optimized conditions was 85%. The developed methodology was applied to the analysis of suspended particulate matter from Lake Maggiore waters (north of Italy). Mean PAH concentrations in suspended particulate matter from Lake Maggiore ranged from 0.2 ng L⁻¹ for anthracene to 18.7 ng L⁻¹ for naphthalene.     

Supramolecular dispersive liquid–liquid microextraction-based solidification of floating organic drops combined with electrothermal atomic absorption spectrometry for determination of chromium species

A simple, sensitive and reliable method has been developed for separation and preconcentration of chromium (VI) from aqueous samples before determination by electrothermal atomic absorption spectrometry. The method is based on the extraction of the hydrophobic complex of chromium (VI) with ammonium pyrrolidine dithiocarbamate in the coacervates made up of decanoic acid reverse micelles in the water–tetrahydrofuran mixture. Parameters affecting the extraction efficiency of the analyte were studied and optimised. Under the optimum conditions, the linear range, enhancement factor, the limit of detection and limit of quantification were found to be 0.008–0.4 µg L^?1, 127, and 1.8 ng L^?1 and 6.0 ng L^?1, of Cr(VI), respectively. The relative standard deviation at the concentration level of 0.1 µg L^?1 Cr(VI) (n = 6) was 4.2%. Total chromium was determined after the oxidation of Cr(III) to Cr(VI) with permanganate in acidic medium. The method was successfully applied to the determination of chromium species in water and human serum samples.