Flow Injection Solid Phase Extraction Research Articles

Simultaneous on-line preconcentration and determination of toxic elements in rice and rice-based products by SPE–ICP–MS: Multiple response optimization

Simultaneous preconcentration of five toxic elements (Cd, Hg, Mn, Pb, and Sb) was carried out using a hyphenated system by on-line coupling of flow injection (FI), solid phase extraction (SPE) and inductively coupled plasma mass spectrometry (ICP–MS). The analytes were simultaneously preconcentrated on a microcolumn filled with oxidized multiwalled carbon nanotubes (ox-MWCNTs). During the method development, SPE conditions were optimized using a chemometric approach with experimental design and desirability function by multi-response surface methodology. An enrichment factor of 104 was obtained when 50 mL of sample were passed through the microcolumn. After optimizing the FI–SPE–ICP–MS system, detection limits were calculated varying from 0.8 ng L−1 for Mn to 0.09 μg L−1 for Hg. The relative standard deviations (RSD) for all elements were < 5%. For checking accuracy two standard reference materials NIST1568b (Rice Flour) and NIST 1643f (Trace Elements in Water) were analyzed and results were in good agreement with certified values. The proposed method was successfully applied to the determination of Cd, Hg, Mn, Pb and Sb in real samples of rice and rice-based products. The concentration of the analytes spanned in the range (ng g−1): Cd, 0.18–23.5; Hg, <4.6-6.0; Mn, <0.04–744; Pb, <0.16–462 and Sb, 5.9–47.

Efficient lead preconcentration using two chemically functionalized carbon nanotubes in hyphenated flow injection-flame atomic absorption spectrometry system

Lead contamination in drinking and natural water has reached alarming concentrations, thus necessitating the development of accurate and rapid determination systems for Pb(II) in aqueous systems. Two hyphenated flow injection-solid phase extraction- FAAS (FI-SPE-FAAS) systems using oxidized and m-phenylenediamine functionalized multiwalled carbon nanotubes for Pb(II) preconcentration from industrially contaminated real water samples have been proposed. The chemical and hydrodynamic parameters affecting Pb(II) sorption/desorption were optimized. The effect of common interfering ions in water was also studied. Different figures of merit such as preconcentration factor (> 70), detection limit (≤ 1.5 µg L−1), and relative standard deviation (≤ 1.3%) were achieved at the preconcentration time of 120 s for both the preconcentration systems. The method was applied to industrially contaminated real water samples and the spike recovery tests were carried out using standard Pb(II) solution traceable to NIST. The proposed method was validated using standard reference material 1640a supplied by NIST Gaithersburg, MD, USA.

A Novel Glass Fiber Coated with Sol-Gel Poly-Diphenylsiloxane Sorbent for the On-Line Determination of Toxic Metals Using Flow Injection Column Preconcentration Platform Coupled with Flame Atomic Absorption Spectrometry.

A novel simple and sensitive, time-based flow injection solid phase extraction system was developed for the automated determination of metals at low concentration. The potential of the proposed scheme, coupled with flame atomic absorption spectrometry (FAAS), was demonstrated for trace lead and chromium(VI) determination in environmental water samples. The method, which was based on a new sorptive extraction system, consisted of a microcolumn packed with glass fiber coated with sol–gel poly (diphenylsiloxane) (sol–gel PDPS), which is presented here for the first time. The analytical procedure involves the on-line chelate complex formation of target species with ammonium pyrrolidine dithiocarbamate (APDC), retention onto the hydrophobic sol–gel sorbent coated surface of glass fibers, and finally elution with methyl isobutyl ketone prior to atomization. All main chemical and hydrodynamic factors, which affect the complex formation, retention, and elution of the metal, were optimized thoroughly. Furthermore, the tolerance to potential interfering ions appearing in environmental samples was also explored. Enhancement factors of 215 and 70, detection limits (3 s) of 1.1 μg·L−1 and 1.2 μg·L−1, and relative standard deviations (RSD) of 3.0% (at 20.0 μg·L−1) and 3.2% (at 20.0 μg·L−1) were obtained for lead and chromium(VI), respec tively, for 120 s preconcentration time. The trueness of the developed method was estimated by analyzing certified reference materials and spiked environmental water samples.

Evaluation of polypropylene and polyethylene as sorbent packing materials in on-line preconcentration columns for trace Pb(II) and Cd(II) determination by FAAS

A novel flow injection solid phase extraction system coupled with flame atomic absorption spectrometer for automatic trace metal determination has been developed. The efficiency of two commercially available low-cost polymers (high-density polyethylene and polypropylene) as packing materials in on-line preconcentration columns for metal extraction was evaluated. Sodium diethyl dithiocarbamate was used as chelating reagent to form the desirable metal complexes while methyl isobutyl ketone was adopted to elute and deliver them into the flame atomizer for measurement and quantification. A comparable study between the two sorbents regarding the analytical performance characteristics was performed and revealed that polypropylene was more suitable than high-density polyethylene regarding the metal complex retention. All main parameters affecting the sensitivity of the proposed method were thoroughly optimized. By adopting polypropylene sorbent and a preconcentration time of 90 s the sampling frequency was 30 h−1, the enhancement factor was 180 and 44, the detection limit (3s) 1.5 and 0.30 μg L−1 while the precision was 2.8% (at 50.0 μg L−1) and 2.9% (at 20.0 μg L−1), for Pb(II) and Cd(II), respectively. The accuracy of the developed method was assessed by the analysis of a certified reference material and spiked environmental water samples.

An On-Line Flow-Injection Sorbent Extraction System Coupled with Flame Atomic Absorption Spectrometry for Thallium Determination Using a PTFE Turning-Packed Column

A novel time-based flow-injection–solid-phase extraction system (FI–SPE) coupled with flame atomic absorption spectrometry (FAAS) for automatic on-line preconcentration and determination of thallium was developed. The efficiency of poly-tetrafluoroethylene (PTFE) turnings packed into a column as sorbent material was investigated for thallium extraction. Total thallium was determined by oxidizing thallium(I) to thallium(III), adding bromine in acidic solution. The formed [TlBr4]− anionic bromo complex was retained onto the PTFE turnings by on-line mixing with sodium diethyl dithiocarbamate (DDTC). The preconcentrated Tl(III)-DDTC complex was then effectively eluted with methyl isobutyl ketone (MIBK) and introduced into the flame atomizer for measurement and quantification. The column proved to be effective, stable, and reproducible, with a long lifetime. The enrichment factor was 105 for 60 s preconcentration time, and the sampling frequency 40 h−1. The detection limit was 1.93 μg L−1, and the relative standard deviation (RSD) was 3.2% at 50.0 μg L−1 concentration. The accuracy of the proposed method was estimated by analyzing certified reference materials and environmental and biological samples.

Reversed phase StrataTM-X resin as sorbent for automatic on-line solid phase extraction atomic absorption spectrometric determination of trace metals: comparison of polymeric-based sorbent materials

ABSTRACTA novel on-line flow injection solid phase extraction method for the preconcentration of trace toxic metals prior determination by flame atomic absorption spectrometry (FI-SPE-FAAS) was developed. The potential application of the hydrophobic reversed phase co-polymer sorbent StrataTM-X packed into an on-line microcolumn for the quantification of Cd(II), Pb(II), Cu(II) and Cr(VI) was demonstrated for the first time. The method was based on the on-line formation of metal complexes using sodium diethyl-dithiocarbamate (DDTC) and on the subsequent retention of them onto the sorbent material. The target analytes were completely eluted by methanol and, subsequently, directed to FAAS for quantification. All chemical and flow variables affecting the performance of the developed method were thoroughly studied and optimised. For a preconcentration time of 90 s and a sampling frequency of 28 h−1, enhancement factors of 72, 140, 185, 63 and detection limits of 0.18, 1.6, 0.20 and 1.2 μg L −1 were obtained for Cd(II), Pb(II), Cu(II) and Cr(VI), respectively. The accuracy of the FI-SPE-FAAS method was evaluated by analysing certified reference materials as well as spiked environmental water samples. Furthermore, a comparative study of the analytical characteristics, the properties as well as the chemical structures of commercial polymeric based sorbent materials was employed. Strata-X sorbent was compared against HypersepTM SCX, Bond Elut® PlexaTM PCX, Oasis-HLBTM and NobiasTM PA-1, regarding the adaptation in on-line FI-SPE-FAAS systems for metal determination, and herein presented.

Cold vapour generation electrothermal atomic absorption spectrometry and solid phase extraction based on a new nanosorbent for sensitive Hg determination in environmental samples (sea water and river water)

A rapid and simple method was developed for separation and pre-concentration of mercury by flow injection solid phase extraction coupled with on-line chemical vapour generation electrothermal atomic absorption spectrometry (CV-HG ETAAS). The system is based on chelating retention of the analyte onto the mini column filled with a new nanosorbent, mesoporous silica functionalized with 1,5 bis (di-2-pyridyl) methylene thiocarbohydrazide. The main aim of this work was to develop a precise and accurate method for the determination of Hg. Under the optima conditions and 120s preconcentration time, the detection limit obtained was 0.008μgL−1, with RSDs 3.0% for 0.2μgL−1, 2.6% for 1μgL−1 and an enrichment factor of 4. Furthermore, the method proposed has permitted the determination of Hg with low consumption of reagents and a sample throughput of about 18h−1.The method was applied to the determination of Hg in sea water and river water. For the quality control of the analytical performance and the validation of the newly developed method, the analysis of two certified samples, TMDA 54.4, Fortified Lake, and LGC6187 River sediment was addressed. The results showed good agreement with the certified values.

A solid phase extraction flow injection spectrophotometric method for the zinc determination in plants

A solid phase extraction flow injection system for the spectrophotometric determination of total zinc in plant digests was developed. Solid phase extraction was chosen as a strategy for zinc preconcentration and removal of some interferences. The determination of zinc was based on the colorimetric reaction with Zincon. As detection system, a multi-reflection flow cell coupled with a light emitting diode was used. The analytical characteristics of the methodology such as pH of standard/sample solution, nitric acid concentration, the placement of SPE column within the manifold and preconcentration flow rate were studied. The interference of some metals present in plants was also assessed. The limits of detection and quantification achieved were 0.04mgL−1 and 0.12mgL−1, respectively. The corresponding Zincon consumption was 0.17mg for each determination. The developed system was applied to plant digests and the results obtained were in agreement with those obtained with reference procedure.

On-line flow injection molecularly imprinted solid phase extraction for the preconcentration and determination of 1-hydroxypyrene in urine samples

New analytical strategies tend to automation of sample pre-treatment and flow analysis techniques provided a number of enhanced analytical methods allowing high throughput. Flow techniques are usually faster, more robust and more flexible than their batch equivalents. In addition, flow methods use less sample and reagent amounts and reduce analytical costs and waste.A flow injection solid-phase extraction pre-concentration system using a molecularly imprinted polymer (MIP) packed micro-column was developed for the determination of 1-hydroxypyrene in human urine with fluorescence detection. The pre-concentration of 1-hydroxypyrene on the MIP was carried out based on the specific retention of analyte by on-line introducing the sample into the micro-column system. Methanol and dichloromethane mixture was used to elute the retained analyte for fluorometric analysis. Important influencing factors were studied in detail, in batch and in flow (MISPE procedure optimisation, sample and eluent volumes, flow rate, dimensions of MIP micro-column and amounts of packing material, etc).To the best of our knowledge, this is the first on-line flow injection molecularly imprinted solid phase extraction for the pre-concentration and determination of hydroxylate PAH metabolite in urine samples.The optimised method was successfully applied to the determination of 1-Hydroxypyrene in spiked urine samples, with recoveries in the range of 74–85% and RSD<4.6%. Under optimum experimental conditions, the linearity concentration range used was 10–400μgL−1, R2>0.996. We obtained limit of detection and quantification of 3.1μgL−1 and 10.5μgL−1, respectively.

Determination of Trialkyl Phosphates in Wastewater by Solid Phase Extraction–Flow Injection–Atmospheric Pressure Chemical Ionization–Mass Spectrometry

ABSTRACTA solid phase extraction–flow injection–atmospheric pressure chemical ionization–mass spectrometry method was developed for the determination of tris[2-chloroethyl]phosphate, tris[2-chloroisopropyl]phosphate, tris[1,3-dichloroisopropyl]phosphate, triethyl phosphate, tributyl-n-phosphate, and tris[2-butoxyethyl]phosphate in wastewater for degradation studies. The mass spectrometry conditions were optimized for each compound and collision-induced dissociation mass spectra were obtained. Lower limits of quantitation from 3.0 to 25.2 ng ml−1 for distilled water were obtained using a 30 mg solid phase extraction cartridge for a 25-fold sample concentration. The lower limits of quantitation were from 15.3 to 70.2 ng ml−1 for wastewater. A 100-fold sample concentration was achieved using a 500 mg cartridge, leading to lower limits of quantitation for trialkyl phosphates in wastewater between 6.3 ng ml−1 for tris[2-butoxyethyl]phosphate and 83 ng ml−1 for tris[1,3-dichloroisopropyl]phosphate. Recoveries for 50.0 ng ml−1 concentrations were from 69% for tris[2-chloroisopropyl]phosphate) to 92% for tris[1,3-dichloroisopropyl]phosphate. Wastewater blanks had peak areas comparable in size to a few ng ml−1 of trialkyl phosphates, presumably from matrix interferences and procedurally generated sample contamination. Evaporative concentration was employed to further increase the sensitivity for the trialkyl phosphates.

Novel Functionalized Silica Gel for On-line Preconcentration of Cadmium(II), Copper(II), and Cobalt(II) with Determination by Flame Atomic Absorption Spectrometry

ABSTRACTSilica gel functionalized with 2-[N,N’-bis(2,3-dihydroxybenzaldimin)] aminoethylamine was employed as a novel sorbent for preconcentration of copper(II), cobalt(II), and cadmium(II) by flow injection-solid phase extraction. The pH of the analyte solution, sample and eluent flow rate, eluent volume, and the presence of concomitant ions were optimized. The limits of detection were 0.65, 0.52, and 1.42 µg/L and preconcentration factors were 12.3, 21.5, and 7.31 for cadmium(II), copper(II), and cobalt(II), respectively. The adsorption capacities of the functionalized silica gel for cadmium(II), copper(II), and cobalt(II) ions were 41.1, 31.7, and 26.5 mg/g. The preconcentration method was validated by determination of cadmium(II), copper(II), and cobalt(II) levels in Virginia Tobacco Leaves (CTA-VTL-2) and Water-Trace Elements (NWTM-15.2) certified reference materials. The method was also used to analyze water and food samples, and offers simplicity, reproducibility, high recovery, rapid and automated analysis, favorable ease of use, and low detection limits.

Simultaneous determination of traces of Pt, Pd, and Ir by SPE-ICP-OES. Test for chemical vapor generation

A method was developed for the simultaneous separation, preconcentration, and determination of platinum, palladium, and iridium by flow injection solid phase extraction coupled with online inductively coupled plasma optical emission spectrometry (SPE-ICP-OES). The system is based on the retention of the analytes onto a minicolumn filled with silica gel functionalized with 1,5-bis(di-2-pyridyl) methylene thiocarbonohydrazide (DPTH-gel) placed in the injection valve of a simple flow manifold. The determination of these elements through chemical vapor generation (CVG) was also tested and compared with the same method without CVG. So, the effects of chemicals and flow variables were investigated by both methodologies. The sensitivity of the method without CVG was better; this confirms the low yields of the reactions of these species compared with the yields of the classical hydrides and the necessity of more research work to improve these yields. With the SPE-ICP-OES method developed, the precision as relative standard deviation (n=10) was 2.8% for Pt, 2.7% for Pd, and 2.9% for Ir. The enrichment factors were 6.3, 6.7, and 6.3 for Pt, Pd, and Ir, respectively. Detection limits (3min sample loading time) were 1.4μgL−1 for Pt, 0.5μgL−1 for Pd and 0.6μgL−1 for Ir. The accuracy of the proposed method was checked with the certified reference material NIST-2557 autocatalyst. The results obtained using this method were in good agreement with the certified values. The recoveries for the method when applied to determine traces of analytes in spiked seawater were 94.5–105.8%.

Redox speciation analysis of dissolved iron in estuarine and coastal waters with on-line solid phase extraction and graphite furnace atomic absorption spectrometry detection

An automatic on-line solid phase extraction (SPE) system employing the flow injection (FI) technique directly coupled to a graphite furnace atomic absorption spectrometer (GFAAS) was established for speciation and determination of dissolved iron in estuarine and coastal waters. Fe(II) was mixed with ferrozine solution in a sample stream to form the Fe(II)–ferrozine complex which was extracted onto a C18 SPE cartridge, eluted with eluent and detected with GFAAS. In a parallel flow channel, Fe(III) was reduced to Fe(II) with ascorbic acid and then detected in the same way as Fe(II). The home-made interface between FI–SPE and GFAAS efficiently realized the sample introduction to the furnace in a semi-automated way. Parameters of the FI–SPE system and graphite furnace program were optimized based on a univariate experimental design and an orthogonal array design. The salinity effect on the method sensitivity was investigated. The proposed method provided a detection limit of 1.38nmolL−1 for Fe(II) and 1.87nmolL−1 for Fe(II+III). With variation of the sample loading volume, a broadened determination range of 2.5–200nmolL−1 iron could be obtained. The proposed method was successfully applied to analyze iron species in samples collected from the Jiulongjiang Estuary, Fujian, China. With the 2-cartridge FI–SPE system developed, on-line simultaneous determination of Fe species with GFAAS was achieved for the first time.

Flow-injection solid phase extraction using Dowex Optipore L493 loaded with dithizone for preconcentration of chromium species from industrial waters and determination by FAAS

An online flow injection preconcentration system for speciation of Cr(iii) and Cr(vi) based on the combination of solid phase extraction (SPE) and flame atomic absorption spectrometry (FAAS) has been described.

On-line flow injection solid phase extraction using imprinted polymeric nanobeads for the preconcentration and determination of mercury ions

• Presentation of a new analytical method for mercury separation. • Highly selective separation and fast determination of hazardous mercury ion. • Determination of Hg 2+ ion in water and hair samples with acceptable accuracy and precision. • On-line determination of mercury ion based on Hg-IIP NPs through FIA. This work reports a new analytical method for the preconcentration and determination of Hg 2+ ions based on flow injection technique coupled with a solid phase extraction process. Hg 2+ ion imprinted polymeric (IIP) nanomaterials were prepared by using the bulk polymerization procedure, and then applied as an efficient solid phase extractor for selective separation of Hg 2+ ions. The prepared sorbent was characterized using FT-IR spectroscopy, scanning electron microscopy (SEM), various thermal analysis methods, and Brunauer, Emmett, and Teller adsorption isotherm analysis (BET). According to the results, surface area, pore volume and average pore diameter of the prepared Hg-IIP were found to be 3.05 × 10 2 m 2 g −1 , 1.07 cm 3 g −1 and 15.33 nm, respectively. In the sorption studies, after preconcentration and loading of Hg 2+ ions on the IIP sorbent, its mercury content was eluted by suitable solution and then determined photometrically, by a designed on-line recording process coupled with a flow injection procedure. The influence of the mercury concentration, preconcentration and elution times, nature, volume, and concentration of the eluent, pH, and flow rate of the solution and eluent on the polymer affinity has been investigated. Bound Hg 2+ ions can be eluted with 5 mL of nitric acid 1.0 mol L −1 and then treated with diphenylthiocarbazone, finally quantified photometrically at 485 nm. The relative standard deviation and detection limit (3 σ ) of the method for eight replicates at optimum pH, were evaluated as 4.2% and 0.036 ng mL −1 , respectively. The IIP sorbent show an excellent selectivity for Hg 2+ ion over other metal ions and was successfully applied to the selective extraction and determination of Hg 2+ ion in water and human hair samples.

Speciation of inorganic selenium in environmental water samples by inductively coupled plasma optical emission spectrometry after preconcentration by using a mesoporous zirconia coating on coal cinder.

A simple, novel, and selective flow-injection solid-phase extraction with inductively coupled plasma optical emission spectrometry method was developed for the speciation of inorganic selenium in environmental water samples. A mesoporous zirconia film was simply introduced to coat coal cinder by means of the sol-gel technique, and the adsorptive performance of the coated material for Se(IV)/Se(VI) was investigated in different media. Both Se(IV) and Se(VI) can be retained quantitatively by the material in HCl/NaOH (pH 1.0-9.0) media, while only Se(IV) was adsorbed quantitatively in sodium acetate buffer (pH 3.5-6.0). Thus, the assay of Se(VI) is based on subtracting Se(IV) from total selenium by controlling different adsorptive media without employing any redox procedure. Under the optimum conditions, the detection limit of Se(IV) is 9.0 ng/L with an enrichment factor of 100, and the relative standard deviation is 3.6% (n = 9, C = 5.0 ng/mL). The developed method was successfully applied to the speciation of inorganic selenium in environmental water samples with satisfactory results. In order to further verify the accuracy of the developed method, it was applied to analysis of total selenium in GSBZ 50031-94 certified reference environmental water, and the determined values coincided with the certified values very well.

On-line flow injection solid phase extraction using oxidised carbon nanotubes as the substrate for cold vapour-atomic absorption determination of Hg(ii) in different kinds of water

To surmount particle agglomeration when columns filled with CNTs are used in flow sorptive systems, we propose to mix CNTs with a low molecular weight polyethylene.

Determination of Three Phthalate Esters in Environmental Samples by Coal Cinder Extraction and Cyclodextrin Modified Micellar Electrokinetic Chromatography

A new micellar electrokinetic chromatography (MEKC) method using beta-cyclodextrin (ß-CD) as the electrophoresis additive has been developed for the simultaneous determination of dimethyl phthalate (DMP), diethyl phthalate (DEP) and di(2-ethylhexyl) phthalate (DEHP) in environmental samples. To improve the sensitivity of cyclodextrin-modified MEKC (CD-MEKC), a flow injection procedure using a microcolumn packed with coal cinder as the solid-phase extractant was also investigated for the preconcentration and separation of DMP, DEP and DEHP in environmental samples. Parameters affecting CD-MEKC separation and coal cinder flow injection solid-phase extraction were systematically researched. In the presence of the running buffer [5 mmol/L of borax, 5% (v/v) methanol and 25 mmol/L of sodium dodecyl sulfate at pH 9.5], the addition of 14 mmol/L ß-CD greatly improved the separation efficiency. The analytes were quantitatively adsorbed by coal cinders and readily desorbed quantitatively with 0.2 mL of 10% (v/v) methanol-10 mmol/L disodium hydrogen phosphate. Under the optimum conditions, the enrichment factor of coal cinder was 60, and the determination limits of DMP, DEP and DEHP were 3.07, 2.07 and 4.06 ng/mL, respectively. The presented procedure was successfully applied to determine DMP, DEP and DEHP in landfill leachate and water samples with satisfactory results.

Determination of antimony, bismuth and tin in natural waters by flow injection solid phase extraction coupled with online hydride generation inductively coupled plasma mass spectrometry

A method was developed for the simultaneous separation, preconcentration and determination of antimony, bismuth and tin by flow injection solid phase extraction coupled with on-line hydride generation inductively coupled plasma mass spectrometry. The system is based on cationic retention of the analytes onto a mini-column filled with silica gel functionalised with 1,5-bis(di-2-pyridyl) methylene thiocarbonohydrazide placed in the injection valve of a simple flow manifold. The effects of chemicals and flow variables were investigated. The optimized operating conditions selected were: sample pH 3.5, sample flow rate 1.9 mL min−1, eluent flow rate 0.5 mL min−1, eluent 4% HNO3 and also 0.75% L-cysteine was added directly to the standard and sample solutions. The relative standard deviations (n = 10) were 1.4% for Sb, 1.1% for Bi and 1.5% for Sn. The enrichment factors were 7.0, 8.6 and 2.5 for Sb, Bi and Sn, respectively. Detection limits (3 min sample loading time) were 0.011 μg L−1 for Sb, 0.002 μg L−1 for Bi and 0.142 μg L−1 for Sn. The accuracy of the proposed method was checked with two certified reference materials (CRMs) of natural water TMDA-54.4 and TM-24.3. The results obtained using this method were in good agreement with the certified values of standard reference materials. The recoveries for the method when applied to determine traces of analytes in seawater were 97.0–107.5%.

3-mercaptopropyltrimethoxysilane-Modified Multi-walled Carbon Nanotubes as a New Functional Adsorbent for Flow Injection Extraction of Pb(II) from Water and Sediment Samples

In the present study, a novel synthesized adsorbent material based on 3-mercaptopropyltrimethoxysilane-functionalized multi-walled carbon nanotubes was used to increase the Pb2+ adsorption from aqueous solutions in a flow injection solid-phase extraction system coupled to flame atomic absorption spectrometry. Spectroscopic and microscopic techniques (Fourier transform infrared spectroscopy, energy dispersive spectroscopy, and scanning electron microscopy) were employed to confirm the chemical modification of the adsorbent surface. Preconcentration conditions (sample pH, flow rate, buffer solution, and eluent concentrations) were optimized using factorial and Doehlert matrix designs that made it possible to construct a linear graph in the 5.0- to 130.0-μg L−1 range (r = 0.9999) and estimate detection and quantification limits (1.7 and 5.7 μg L−1, respectively). The method precision was found to be 4.20 and 1.97 % for 5.0 and 100.0 μg L−1 Pb2+ solutions, respectively. When using the 3-mercaptopropyltrimethoxysilane-functionalized multi-walled carbon nanotubes, the sensitivity for the Pb2+ trace determination was improved to 95 % compared with the oxidized multi-walled carbon nanotubes, thus evidencing the significant enhancement of the adsorption capacity. The developed method was successfully applied to the analysis of Pb2+ species in different water samples and the PACS-2 marine sediment-certified reference material.