Extraction and preconcentration of ultra trace amounts of beryllium from aqueous samples by nanometer mesoporous silica functionalized by 2,4-dihydroxybenzaldehyde prior to ICP OES determination

A new functionalized nanometer mesoporous silica (MCM-41) using 2,4-dihydroxybenzaldehyde (4-OHsal) was applied as an effective sorbent for solid phase extraction (SPE) of beryllium ions from aqueous solution followed by inductively coupled plasma optical emission spectrometric detection (ICP OES). The influences of some analytical parameters on the quantitative recoveries of the analyte ion were investigated in batch method. In order to perform the batch mode of SPE, known amount of sorbent was added to a test tube containing sample solution buffered at pH 7.2. After manual shaking and centrifugation the aqueous phase was decanted and beryllium was desorbed by adding 1.0 mL of 1.0 mol L^?1 HNO₃ to the sedimented sorbent. The sorbent was separated by centrifugation and the concentration of beryllium in the supernatant was determined by ICP OES. The maximum sorption capacity of the modified MCM-41 was found to be 34 mg g^?1. The sorbent exhibited good stability, reusability and fast rate of equilibrium for sorption/desorption of beryllium ions. The present method was used for preconcentration and determination of beryllium for water samples. Under optimal conditions, the limit of detection (LOD) obtained was 0.3 ng L^?1. The accuracy of the procedure was evaluated by analysis of the certified reference material (NIST 1640).     

Preconcentration of trace amounts of cobalt (II) ions in water and agricultural products samples using of 5-(4-dimethylaminobenzylidene) rhodanin modified SBA-15 sorbent prior to FAAS determination

In the present study, the ?5-(4-dimethylaminobenzylidene)rhodanin-modified SBA-15? was applied as stable solid sorbent for the separation and preconcentration of trace amounts of cobalt ions in aqueous solution. SBA-15 was modified by ?5-(4-dimethylaminobenzylidene)rhodanin reagent. The sorption of Co²⁺ ions was done onto modified sorbent in the pH range of 6.8–7.9 and desorption occurred in 5.0 mL of 3.0 mol L^?1 HNO₃. The results exhibit a linear dynamic range from 0.01 to 6.0 mg L^?1 for cobalt. Intra-day (repeatability) and inter-day (reproducibility) for 10 replicated determination of 0.06 mg L^?1 of cobalt was ±1.82% and ?±1.97%?. Detection limit was 4.2 µg L^?1 (3S_b, n = 5) and preconcentration factor was 80. The effects of the experimental parameters, including the sample pH, flow rates of sample and eluent solution, eluent type and interference ions were studied for the preconcentration of Co²⁺. The proposed method was applied for the determination of cobalt in standard samples, water samples and agricultural products.     

Polythionine-decorated magnetic nanoparticles as a robust and highly effective sorbent for mercury determination in environmental water samples

Extraction, pre-concentration and determination of trace amounts of mercury ions from water samples were investigated by magnetic solid phase extraction (MSPE) method using Fe₃O₄ nanoparticles decorated with polythionine as an adsorbent. A simple chemical synthesis by catalytic reaction of thionine in the presence of FeCl₃ and hydrogen peroxide was used for preparation of the magnetic sorbent. Scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, vibrating sample magnetometer analysis and Fourier transform infrared spectroscopy were used to characterise the adsorbent. Mercury ions were determined by cold vapour atomic absorption spectrometry. The parameters for MSPE procedure, such as pH of the extraction solution, adsorption time, weight adsorbent, elution conditions (type, concentration and volume of the eluent), volume of the sample solution and effects of coexisting ions were investigated. The obtained optimal conditions were: sample pH of 4; sorbent amount of 4 mg; sorption time of 20 min; elution solvent of HNO₃ (0.3 mol L^?1)/thiourea (2% w/v) with volume of 2 mL, and breakthrough volume of 400 mL. A good linearity in the concentration range of 0.025–40 µg L^?1 (R² > 0.999) with the pre-concentration factor of 198 was obtained. The limits of detection and quantification were achieved as 0.008 and 0.025 µg L^?1, respectively. Furthermore, sea and river water samples were analysed and good recoveries (97.1–99.6%) were obtained.     

Sorbent separation and enrichment method for cobalt ions determination by graphite furnace atomic absorption spectrometry in water and urine samples using multiwall carbon nanotubes

A new cobalt ions pre-concentration method, optimised by fractional factorial design, using multiwall carbon nanotubes (MWCNTs) with further Graphite Furnace Atomic Absorption Spectrometry (GFAAS) quantification is described. The method explores the high chemical and physical stability of MWCNTs for improving the detectability of GFAAS. It is based on off-line pre-concentration of 20.0 mL of sample previously buffered (pH 8.82) on MWCNTs at a flow rate of 10.0 mL min^?1. After the pre-concentration procedure, the elution step was carried out with 500 µL of 0.524 mol L^?1 HNO₃ solution at a flow rate of 2.0 mL min^?1. Fractional factorial designs and response surface methodology were employed for optimisation of all chemical parameters involved in the pre-concentration procedure, including pre-concentration flow rate, buffer and eluent concentration, sample pH and elution volume. The method provides a linear calibration range from 0.03 up to 7.00 µg L^?1 with linear correlation coefficient higher than 0.9994 and limits of detection and quantification of 0.01 and 0.03 µg L^?1, respectively. Repeatability of the six measurements was found to be 2.38 and 1.84% for 0.3 and 4.5 µg L^?1 cobalt concentration, respectively. By pre-concentrating 20.0 mL of sample, a pre-concentration factor (PF) of 19.10-fold and a consumption index of 1.05 mL were obtained. The pre-concentration efficiency (PE) was found to be 9.55 min^?1. The proposed method was successfully applied for the pre-concentration and determination of cobalt in water and urine samples with satisfactory recovery values.     

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.     

Application of ion-imprinted polymer synthesized by precipitation polymerization as an efficient and selective sorbent for separation and pre-concentration of chromium ions from some real samples

In this study, a new Cr(III)-imprinted polymer (Cr(III)-IIP) is prepared from CrCl₃·6H₂O, methacrylic acid functional monomer, ethyleneglycoldimethacrylate cross-linking agent, 2,2?-azobisisobutyronitrile radical initiator and 2,2-(azanediylbis (ethane-2,1-diyl))bis(isoindoline-1,3-dione) ligand. To obtain the maximum adsorption capacity, the optimum condition was studied through pH, type and concentration of eluent, IIP weight, sample volume as well as the adsorption and desorption times. The Cr(III) ion content was determined via flame atomic absorption spectrometer. In optimum conditions, the adsorption capacity of the IIP for Cr(III) was obtained to be 74.65 mg g^?1, using 50 mg of IIP and the initial pH solution of 3.0. Both the adsorption and desorption times for quantitative analyses of Cr(III) ions were 15 and 5 min; respectively. After elution of the adsorbed ions by 3 mL of 4 mol L^?1 HNO₃ aqueous solution, the established IIP-based SPE procedure provides a reasonable pre-concentration factor of 100. The IIP-based pre-concentration method provides a low detection limit of 1.7 µg L^?1 with good repeatability (RSD?=?3.22%). Reusability studies confirmed that synthesis IIP is reusable and recoverable up to six cycles. According to the selectivity experiments, it was concluded that the prepared sorbent possesses more affinity toward Cr(III) ions than other ions such as Al³⁺, Pb²⁺, Cu²⁺, Mn²⁺, Fe²⁺, Zn²⁺, and Ni²⁺ ions. To evaluate the potential applicability of the proposed separation method, the pre-concentration and determination of trace amounts of Cr(III) were performed successfully in food samples with complex matrices, a bestial sample (i.e. cow liver) and an herbal product (i.e., broccoli) as real samples.     

Veterinary antimicrobials and antiparasitics in fee-fishing ponds: analytical method and occurrence*

ABSTRACT

The aim of this work was to develop and validate a method using online solid-phase extraction and ultra-high-performance liquid chromatography coupled to tandem mass spectrometry to determine residues of 22 veterinary drugs including sulfonamides, amphenicols, fluoroquinolones, benzimidazoles, trimethoprim (TMP) and oxytetracycline (OTC) in water from fee-fishing ponds. The optimal analytical conditions were as follows: XBridge C8 SPE column, Acquity UPLC CSH C18 analytical column, sample loading with water:methanol (98:2, v/v), mobile phase of water with 0.1% acetic acid:methanol (with gradient elution) and eluent flow rate of 0.3 mL min^?1. Quantification was performed in selected reaction monitoring mode and sulfadimethoxine-d₆, ciprofloxacin-d₈, florfenicol-d₃ and albendazole-d₃ were used as internal standards. Water samples collected from 11 fee-fishing ponds showed the presence of residues of FF (0.42–0.74 µg L^?1), albendazole (0.05–0.31 µg L^?1) and thiabendazole (0.45 µg L^?1). Thiamphenicol and TMP were detected at concentrations lower than the limits of quantification of the method (0.1 and 0.001 µg L^?1, respectively).     

Novel Imprinted Polymer for the Preconcentration of Cadmium with Determination by Inductively Coupled Plasma Mass Spectrometry

A novel Cd(II)-imprinted polymer was prepared with chemical immobilization using N-methacryloyl-L-Histidine as a vinylated chelating agent for online solid-phase extraction of Cd(II) for determination by inductively coupled plasma mass spectrometry. The Cd(II)–monomer complex was synthesized and copolymerized through bulk polymerization method in the presence of ethyleneglycoldimethacrylate cross-linker. The resulting polymer was leached with 1.0?mol?L^?1 HNO₃ to generate the cavities in the polymer for Cd(II) ions. The experimental conditions, including load pH, solution flow rate, and eluent concentration for effective sorption of Cd(II), were optimized using a minicolumn of the imprinted polymer. A volume of 5.0?mL sample 5?µg?L^?1 Cd(II) solution at pH 6.5 was loaded on the column at 2.0?mL?min^?1 using a sequential injection system followed by elution with 1.0?mL of 0.75?mol?L^?1 HNO₃. The relative selectivity coefficients of the imprinted polymer for Cd(II) were 38.5, 3.5, 3.0, 2.5, and 6.0 in the presence of Cu(II), Ni(II), Zn(II), Co(II), and Pb(II), respectively. Computational calculations revealed that the selectivity of the imprinted polymer was mediated by the stability of Cd(II)–N-methacryloyl-L-Histidine complex which was more stable than commonly used monomers including 4-vinyl pyridine, methacrylic acid, and vinylimidazole. The detection limit and relative standard deviation were 0.004?µg?L^?1 and 3.2%, respectively. The method was validated by the analysis of seawater certified reference material (CASS-4) and successfully used for the determination of Cd(II) in coastal seawater and estuarine water.     

Preconcentration of Trace Cadmium (II) and Copper (II) in Environmental Water Using a Column Packed with Modified Silica Gel-Chitosan Prior to Flame Atomic Absorption Spectrometry Determination

A new column loaded with modified silica gel-chitosan is proposed as a preconcentration system for adsorption of trace cadmium (II) and copper (II). The optimization steps were performed under dynamic conditions, involving pH, sample flow rate, eluent selection, concentration, volume, and flow rate. Trace Cd(II) and Cu(II) were quantitatively adsorbed by the modified silica gel-chitosan. The metal ions adsorbed on the separation column were eluted with 0.1 M HNO₃ and determined by flame atomic absorption spectrometry. Under the optimum conditions, this method allowed the determination of cadmium and copper with limits of detection (LOD) of 20 ng L^?1 and 38 ng L^?1, respectively. The relative standard deviation values (RSDs) for 1.0 mg L^?1 of cadmium and 1.0 mg L^?1 of copper were 2.62% and 2.85%, respectively.     

Activated Carbon Modified with Sodium Dodecyl Sulfonate as a Solid Phase Sorbent for the Separation and Preconcentration of Trace Cadmium in Water Samples with Detection by Electrothermal Atomic Absorption Spectrometry

A novel absorbent was prepared by sodium dodecyl sulfonate (SDS)-modified activated carbon (SDS-AC) and was employed as the microcolumn packing material for separation/preconcentration of trace Cd(II). The method based on Cd(II) was quantitatively retained by SDS-AC sorbent, which entailed cation exchange nature and negative charged surface, facilitating favorable retention of positively charged ions. The retained Cd(II) was effectively recovered with elution by 1 mol · L^?1 HNO₃, and the eluent was quantified by electrothermal atomic absorption spectrometry (ET-AAS). Under the optimized conditions, the limit of detection (LOD) for Cd(II) was 3 ng · L^?1 with the consumption of 20.0 mL sample solution. The relative standard deviation (RSD) for ten replicate measurements of 50 ng · L^?1 Cd(II) was 2.9%. The developed technique was demonstrated for the determination of trace Cd(II) in water samples and the recoveries for spiked samples were found to be in the range of 94.9–107.2%. For validation, two certified reference materials of water samples (GBW08607 and GBW08608) were analyzed, and the results obtained were in good agreement with the certified values.     

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).     

Solid-phase Extraction for Analysis of Short-Chain Chlorinated Paraffins in Water Samples

A method for analysis of short-chain chlorinated paraffins (SCCPs) in water based on solid-phase extraction (SPE) was established using electron capture negative chemical ionization mass spectrometry (GC-ENCI-MS). The SPE parameters, including the sorbent, eluent and elution volume were optimized. The Agilent Bond Elut-C₁₈ was precleaned with 3 mL of hexane and 3 mL of methanol, and subsequently conditioned with 3 mL H₂O prior to use. After the water samples were enriched by the cartridge, the sample was washed with 3 mL of 10% (V/V) methanol and eluted with 3 mL of hexane-dichloromethane (1:1, V/V) solution. The results indicated that the limits of detection (LOD) for SCCPs were 18 ng L^?1, while the corresponding limits of quantitation (LOQ) were 60 ng L^?1. The spiked recovery range was 90%–135%, with a relative standard deviation of less than 10%. Finally, 20 surficial water samples around Beijing were collected and SCCPs contents were analyzed using the proposed method. The SCCPs concentrations ranged from less than LOD to 682 ng L^?1 with a mean concentration of 216 ng L^?1.     

Chemically modified silica gel for selective solid-phase extraction and preconcentration of heavy metal ions

This paper describes our research on the synthesis of the sorbent with chemically bonded ketoimine groups, and, furthermore, using this sorbent in the SPE technique to extract and preconcentrate trace amounts of metal ions in water samples. Surface characteristics of the sorbent were determined by elemental analysis, NMR spectra for the solid phases (²⁹Si CP MAS NMR), and analysis of pore size distribution of the sorbent and nitrogen adsorption-desorption. The newly proposed sorbent with ketoimine groups was applied for the extraction and preconcentration of trace amounts of Cu (II), Cr (III) and Zn (II) ions from the water from a lake, post-industrial water and purified water unburdened back to the lake. The determination of the transition-metal ions was performed on an emission spectroscope with inductively coupled plasma ICP-OES. For the batch method, the optimum pH range for Cu (II) and Cr (III) extraction was equal to 5, and Zn(II)–to 8. All the metal ions can be desorbed from SPE columns with 10?mL of 0.5?mol?HNO₃. The detection limits of the method were found to be 0.7?µg?L^?1 for Cu (II), 0.08?µg?L^?1 for Cr (III), and 0.2?µg?L^?1 for Zn (II), respectively.     

Solid phase extraction and preconcentration of some metal ions using Schiff base immobilised silica gel followed by ICP-OES

ABSTRACT

In this study, a simple and efficient solid phase extraction procedure was developed for simultaneous separation and preconcentration of Ba, Cd, Co, Cu, Mn and Ni. The methodology was based on preconcentration of the target analytes on N,N’-bis(4-methoxysalicylidene)-1,3-propanediamine modified silica gel prior to inductively coupled plasma optic emission spectrometry detection. The experimental conditions were as follows: pH of sample 5.00; sample and eluent flow rates 3 mL min^?1; sample volume 25 mL; eluent 0.5 mol L^?1 HNO₃; eluent volume 3.0 mL. Preconcentration factor was achieved as 33.3 for Ba, Co, Mn; 83.3 for Cd, Ni; 166.7 for Cu. Limits of detection were found as 0.33, 0.26, 0.27, 0.36, 0.27 and 0.19 µg L^?1 for Ba, Cd, Co, Cu, Mn and Ni, respectively. The relative standard deviations of 2.6–3.8% were obtained via nine parallel analyses. The suggested procedure was successfully validated by the analysis of TMDA-53.3 Lake Ontario water and ERM-CA022a soft drinking water certified reference materials and applied to various natural water samples.     

Application of Ni(II)-imprinted cross-linked poly(methacrylic acid) synthesised through double-imprinting method for the on-line preconcentration of Ni(II) ions in aqueous media

The present paper describes the feasibility of on-line preconcentration of nickel ions from aqueous medium on Ni(II)-imprinted cross-linked poly(methacrylic acid) (IIP) synthesised through a double-imprinting method and their subsequent determination by FAAS. The proposed method consisted in loading the sample (20.0 mL, pH 7.25) through a mini-column packed with 50 mg of the IIP for 2 min. The elution step was performed with 1.0 mol L^?1 HNO₃ at a flow rate of 7.0 mL min^?1. The following parameters were obtained: quantification limit (QL) – 3.74 µg L^?1, preconcentration factor (PF) – 36, consumption index (CI) – 0.55 mL, concentration efficiency (CE) – 18 min^?1, and sample throughput – 25 h^?1. The precision of the procedure assessed in terms of repeatability for ten determinations was 5.6% and 2.5% for respective concentrations of 5.0 and 110.0 µg L^?1. Moreover, the analytical curve was obtained in the range of 5.0–180.0 µg L^?1 (r = 0.9973), and a 1.64-fold increase in the method sensitivity was observed when compared with the analytical curve constructed for the NIP (non-imprinted polymer), thus suggesting a synergistic effect of the Ni(II) ions and CTAB on the adsorption properties of the IIP. The practical application of the adsorbent was evaluated from an analysis of tap, mineral, lake and river water. Considering the results of addition and recovery experiments (90.2–100 %), the efficiency of this adsorbent can be ensured for the interference-free preconcentration of the Ni(II) ions.     

Simultaneous preconcentration and determination of nickel and cobalt using functionalised mesoporous silica spheres by ICP-OES

In this work functionalised mesoporous silica spheres have been utilised for the simultaneous preconcentration of nickel and cobalt. The silica spheres (SiSPs) prepared by the sol-gel method were functionalised with sodium diethyldithiocarbamate (DDTC-SiSPs). They were characterised by SEM, TEM, XRD, FTIR, CHN and nitrogen adsorption. The adsorption efficiency of DDTC-SiSPs was examined by batch equilibrium technique. The DDTC-SiSPs showed 100% adsorption for Ni (II) and Co (II). The effect of changing variables such as pH, shaking time, sample volume, preconcentration factor, eluent type and volume were investigated so as to obtain maximum recovery with high selectivity over interfering ions. The maximum adsorption capacity was found to be 15.15 mg g^?1 and 11.80 mg g^?1 for Ni (II) and Co (II) respectively using DDTC-SiSPs. 100% recovery was achieved with 5 mL of 2 M HNO₃. The maximum preconcentration factor was 400 and the 3σ limits of detection were 0.201 µg L^?1 and 0.198 µg L^?1 for Ni (II) and Co (II) respectively. Thermodynamic studies showed that adsorption of Ni (II) and Co (II) on DDTC-SiSPs is exothermic with enthalpy changes of –0.514 KJ mol^?1 and –0.854 KJ mol^?1 for Ni (II) and Co (II) respectively. The method was applied to the preconcentration and determination of Ni (II) and Co (II) from tap, river and sea water.     

On-line determination of palladium by flame atomic absorption spectrometry coupled with a separation/preconcentration minicolumn containing a new sorbent

A method was developed for the on-line determination of palladium in complex matrices with flame atomic absorption spectrometry (FAAS) using Amberlite XAD-16 resin functionalized with 2-[2-(5-thiol-1,3,4-thiadiazolyl)]-azonaphthol (TTAN) reagent. Optimum experimental conditions such as pH of sample, type of eluent, amount of resin, volumes of sample and eluent solution, flow rates of sample and eluent, and effect of interfering ions were established. A 0.1?mol?L^?1 thiourea solution in 0.5?mol?L^?1 HCl was used as the eluent and subsequently transportation the analyte ions into the nebulizer–burner system for atomization. The synthesized chelating resin material showed excellent chemical and mechanical resistance, fast adsorption kinetics permitting the use of high sample flow rates without significant losses of retention efficiency. The detection limit of the method was 1.5?µg?L^?1 while the relative standard deviation (RSD%) was 2.4% at 0.1?mg?L^?1 Pd(II) level. The developed method was successfully applied to the determination of palladium in the catalytic converter and water samples.     

Separation and spectrophotometric determination of very low levels of Cr(VI) in water samples by novel pyridine-functionalized mesoporous silica

A modified SBA-15 mesoporous silica was developed, as an adsorbent, for the removal of Cr(VI) ions from natural-water samples. The effects of experimental parameters, including pH of solution, sample and eluent flow rate, the eluent composition, the eluent volume, and the effect of coexisting ions on the separation and determination of Cr(VI), were investigated. It was shown that Cr(VI) was selectively adsorbed from aqueous solution at pH 3, but Cr(III) could be adsorbed from solution at alkaline pH range. The retained Cr(VI) was eluted with 0.5?mol?L^?1 KCl solution in 0.1?mol?L^?1 Na₂CO₃ subsequently. Under the optimum conditions, the modified mesoporous silica (py-SBA-15) with a high pore diameter exhibited an adsorption capacity of 136?mg?g^?1 and a lower limit of detection than 2.3?µg?L^?1 by using diphenylcarbazide as a chromophorous reagent for the determination of Cr(VI) ions. A preconcentration factor as high as 200 was calculated for Cr(VI). The loaded py-SBA-15 can be reactivated with recovery of more than 98.5% over at least eight cycles. The relative standard deviation (RSD) for Cr(VI) ion recovery was less than 1.8%. Validation of the outlined method was performed by analysing a certified reference material (BCR 544). The proposed method was applied to determine Cr(VI) value in natural and waste water samples successfully.     

Direct electrochemistry and electrocatalysis of hemoglobin on an indium tin oxide electrode modified with implanted carboxy ions

A flow injection on-line preconcentration system was developed for the determination of lead by hydride generation atomic fluorescence spectrometry (HG-AFS). It is based on a simple micro-column filled with multiwalled carbon nanotubes (MWCNTs). The preconcentration of lead on the MWCNTs was carried out based on the adsorptive retention of analyte via on-line introducing the sample into the micro-column system. A 0.3 mol L^?1 HNO₃ was introduced to elute the retained analyte and merged with KBH₄ solution for HG-AFS detection. Under the optimal experimental conditions, an enhancement factor of 26 was obtained with a sample consumption of 14.4 mL. The limit of detection was 2.8 ng L^?1 and the precision (RSD) of 11 replicate measurements of 0.2?μg L^?1 Pb was 4.4%. The method was validated by analyzing three certified reference materials, and was successfully applied to the determination of trace lead in natural water samples.     

Magnetic Solid Phase Extraction Based on Modified Magnetite Nanoparticles Coupled with Dispersive Liquid–Liquid Microextraction as an Efficient Method for Simultaneous Extraction of Hydrophobic and Hydrophilic Drugs

In this work, surfactant-coated Fe₃O₄@decanoic acid nanoparticles was synthesized as a viable nanosorbent for coextraction of drugs with different polarities (hydrophobic, hydrophilic). To reach desirable enrichment factors, efficient clean-up and low limits of detection (LODs), the method was combined with dispersive liquid–liquid microextraction (DLLME). The coupling of these extraction methods with GC-FID detection was applied to simultaneous extraction and quantification of venlafaxine (VLF) as a hydrophilic model drug and desipramine (DESI) and clomipramine (CLO) as hydrophobic model drugs in urine samples. The effect of sample pH, nanosorbent amount, sorption time, surfactant concentration, eluent type, eluent volume, salt content, elution time in magnetic solid phase extraction step and extraction solvent and its volume along with sample pH in DLLME step were optimized. Under the selected conditions, linearity was achieved within the range of 5–5000 µg L^?1. The LOD values were obtained in the range of 1.5–3.0 µg L^?1 for DESI, 1.2–2.5 µg L^?1 for VLF and 2.0–4.0 µg L^?1 for CLO, respectively. The percent of extraction recoveries and relative standard deviations (n?=?5) were in the range of 82.4–95.9 and 6.1 for DESI, 60.5–92.8 and 6.9 for VLF and 57.2–58.0 and 5.5 for CLO, respectively. Ultimately, the applicability of the new method was successfully confirmed by the extraction and quantification of DESI, VLF and CLO from human urine samples.