Removal and enrichment of copper ions from aqueous solution by 1,8-diaminonapthalene polymer

European Polymer Journal 44 (2008) 2108–2114

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European Polymer Journal

journal homepage: www.elsevier .com/locate /europol j

Removal and enrichment of copper ions from aqueous solution by1,8-diaminonapthalene polymer

Joanna Rutkowska a, Krzysztof Kilian b, Krystyna Pyrzynska a,*

a University of Warsaw, Faculty of Chemistry, Pasteura 1, 02-093 Warsaw, Polandb University of Warsaw, Heavy Ion Laboratory, Pasteura 5a, 02-093 Warsaw, Poland

a r t i c l e i n f o

Article history:Received 21 February 2008Received in revised form 27 March 2008Accepted 7 April 2008Available online 12 April 2008

Keywords:Poly(1,8-diaminonapthalene)AdsorptionHeavy metal ionspH effect

0014-3057/$ - see front matter � 2008 Elsevier Ltddoi:10.1016/j.eurpolymj.2008.04.009

* Corresponding author.E-mail address: [email protected] (K. Py

a b s t r a c t

Microparticles of poly(1,8-diaminonapthalene) (PDAN) were prepared by chemically oxi-dative polymerization by (NH4)2S2O8. The effect of pH on the sorption of Cd(II), Cu(II),Ni(II), Mn(II), Zn(II) and Pb(II) on PDAN was examined by the batch procedure. PDANshowed good sorption capacity and high selectivity towards Cu(II) in comparison withthe very popular chelating sorbent Chelex 100 containing iminodiacetic functional groups.The on-line preconcentration system containing the knotted reactor with the obtainedpolymer was examined for the sorption and desorption processes of copper ions. The appli-cability of this system was checked by analysis of Cu(II) content in standard referencematerial (NIST 1643e) and some natural water samples.

� 2008 Elsevier Ltd. All rights reserved.

1. Introduction

In the recent years, increased concern of the toxic effectsof heavy metal pollution of the environment and particu-larly bodies of water has resulted in an intensive effort to de-velop methods for their determination as well as for theirenrichment and removal from aqueous solutions. The accu-rate determination of metal ions in different samples inpractice is frequently problematic due to the presence ofinterfering matrix effects and low content of the an analytes.The most effective way to avoid these problems is to performappropriate sample pretreatment prior to analysis aimed atlowering the limits of detection, by both removal of interfer-ences and increasing the concentration of the species ofinterest. Such procedures are most advantageously per-formed using flow analysis approach where all the unit oper-ations can be executed on-line with high reproducibility andwhere risks of sample contamination are minimized [1].

Solid phase extraction techniques utilizing columnspacked with chelating resins, reversed phase silica gel

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rzynska).

and polymeric sorbents as well as those using open tubeknotted reactor produced from PTFE tubing are mostextensively used for on-line sample pretreatment in theanalysis of trace amounts of metals due to their high sep-aration and preconcentration efficiency [2,3]. The mostwidely used complexing reagents for metal preconcentra-tion in sorbent extraction have been so far diethyldithioc-arbamates [4,5], ammonium pyrrolidine-dithiocarbamate[6,7] and diethyldithiophosphate [8]. The introduction ofthe new solid materials, the development of new experi-mental configurations in order to adapt sorbent extractionto a specific situation and the improvement of automaticdevices will undoubtedly lead to their application in differ-ent fields of chemical analysis [1,9].

In the recent years, intrinsic conducting polymers withconjugated double bonds have been attracting much atten-tion as advanced materials due to their multifunctionalproperties and potential application, including ionexchangers, energy storage materials, corrosion-resistantcoating, catalysts and chemical sensors [10–14]. They havealso shown affinity to some metal ions due to their chelat-ing properties and/or reduction properties owing to theelectron donating groups (amine and secondary amino

Fig. 1. SEM image of PDAN sorbent.

J. Rutkowska et al. / European Polymer Journal 44 (2008) 2108–2114 2109

groups) on the polymer chain [14–19]. Many studies areconcentrated on the electrochemical synthesis of suchpolymers [11,15,16]. However, the resulting film has rel-atively low specific area and restrictive sites to contactwith metal ions, thus, it could not be applied for efficientrecovery of metal ions from aqueous solutions. Thechemical oxidative polymerization reaction affords uni-form and fine particles of a polymer and should facilitateits application in the solid phase extraction technique. Liet al. [17,18] employed chemically oxidative polymeriza-tion of 1,8-diaminonapthalene and 4-sulfonic diphenyl-amine to obtain the copolymer particles as a novelsorbent for effective extraction of silver ions, while finemicroparticles of poly(m-phenylenediamine), directlysynthesized by a facile oxidative precipitation polymeri-zation exhibit strong ability to adsorb lead ions fromaqueous solution [14,19].

In this work, we attempt to explore the sorptionbehavior of several divalent metal ions on microparticlesof poly(1,8-diaminonapthalene) (PDAN) prepared bychemically oxidative polymerization by (NH4)2S2O8. Theeffect of pH on the sorption of Cd(II), Cu(II), Ni(II), Mn(II),Zn(II) and Pb(II) onto PDAN was examined by the batchprocedure. For comparison similar experiments wereconducted using the very popular chelating sorbent Che-lex 100 containing iminodiacetic functional groups [20].The on-line preconcentration system containing theknotted reactor with the obtained polymer was exam-ined for the sorption and desorption processes of copperions. Such system was studied in detail for the first time.

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.

120017002200270032003700

1

2

Wavenumbers. cm-1

AU

Fig. 2. IR spectra of: (1) monomer and (2) PDAN.

2. Experimental

2.1. Reagents

The chemicals used were of analytical grade, and all thesolutions were prepared with deionized water obtained bya Milli-Q system (Millipore). 1,8-diaminonapthalene (1,8-DAN, 98% purity) and ammonium peroxydisulphate wereobtained from Sigma (St. Louis, MO, USA). Substances weredissolved in acetonitrile from Merck (Darmstadt,Germany).

The buffer components: sodium acetate, acetic acid andsodium hydroxide were of analytical grade and obtainedfrom POCH (Gliwice, Poland). Stock solutions of metal ions:Pb, Cu, Ni, Mn, Cd and Zn at a concentration of 1000 mg/Lwere purchased from Merck. Working standard solutionswere prepared daily by appropriate dilution with deion-ized water.

2.2. Preparation and characterization of polymer

Poly(1,8-DAN) was prepared in a chemical synthesis, byoxidation of a monomer with ammonium peroxydisul-phate. 4.75 g of 1,8-DAN was added to 100 mL of solutioncontaining 6.84 g of (NH4)2S2O8 in acetonitrile and stirredvigorously for 60 min. After filtration, the obtained sorbentwas rinsed with 1 M HCl and deionized water.

Scanning electron microscopy (SEM) images wereachieved by ZEISS Leo 435 VP to observe the overall mor-

phology and the microstructure of the polymer (Fig. 1).Samples were Pt covered with Polaron SC 7620 sputteringset (Quorum Tech, Newhave, UK). IR spectra were acquisit-ed in KBr pellets with Nicolet 550 FTIR spectrometer (Nico-let Tech., Madison, WI, USA) and are presented in Fig. 2.The elemental analysis was carried out on Carbo 2400 ele-ment analyzer (Perkin Elmer). The Barrett–Emmett–Teller(BET) method was utilized to calculate the surface area(ASAP 2405 analyzer).

2.3. Retention of metal ions as a function of pH

The experiments were carried out by batch procedure.15 mg of dry sorbents (PDAN and Chelex 100, respec-tively) was gently shaken for 60 min with 10 mL of1 lg/mL solution of each metal ions at an appropriatepH value. The concentration of metals was then deter-mined in the filtrate by atomic absorption spectrometry(AAS). Retention of metal ions was expressed in terms

V1

Sample

Water

HNO3

Knotted reactor

V2Pump

ONOFF

Waste

FAAS

PumpV2

Sample

Water

HNO3

FAAS

Knottedreactor

Waste

V1 FAAS

A

B

Fig. 3. Flow injection manifold for the on-line preconcentration of Cu(II). V – multifunctional valves; W – waste. (A) preconcentration step and (B) elutionstep.

2110 J. Rutkowska et al. / European Polymer Journal 44 (2008) 2108–2114

of percent of sorption calculated in comparison to theinitial metal content. The results are based on at leastthree replicates.

2.4. Sorption of copper ions in the dynamic conditions

The reactor for preconcentration in the dynamic con-ditions was prepared from PTFE tubing (1.5 m long, 0.5mm i.d.) by typing 37 interlaced knots of approximately10 mm loops. The monomer (2.5 of 1,8-DAN in 50 mL ofacetone) was introduced inside the tubing and after60 min (NH4)2S2O8 solution (0.3 mol/L) was added. Whenthe monomer changed its colour to black, the reactorwas rinsed with HCl solution, water and acetic buffer.

The used flow injection systems, shown schematicallyin Fig. 3, consisted of an Ismatec MS/4 Reglo peristalticpump, two Rheodyne RH 5020 low-pressure injectionvalves and the prepared reactor with PDAN, the ends ofwhich were fitted with cotton to retain the polymer inthe tube. The preconcentration unit was integrated intothe system between the eluent injection valve and thenebulizer of the instrument. PTFE tubes (0.8 mm i.d.)were employed for the coils. The flow system was oper-ated in the time-based mode. After pumping a samplethrough the tubing for preconcentration, the first injec-tion valve (V1) was switched to its other position and0.5 mL of 2 mol/L HNO3 solution was injected by meansof a second valve (V2) in order to release copper ions di-rectly into the nebulizer of the spectrometer. Finally, theblank carrier (deionised water) was passed for 30 s (at6.8 mL/min) in order to prepare it for the following sam-ple loading.

3. Results and discussion

3.1. Synthesis of polymer

The chemically oxidative polymerization of 1,8-DANwas performed using ammonium peroxydisulphate. Aftersynthesis the suspended polymer was filtered and washedwith acetonitrile until the eluate was colorless, followed bywashing with 1 mol/L HCl and then with water to neutralpH. The polymer was subsequently air dried for 24 h andafter that it appeared as a powder without the tendencyto form any macroscopic aggregates.

Fig. 1 presents a SEM image of the obtained PDAN nano-structure. The regular, spherical grains with diameterabout 300–500 nm were obtained which could be a poten-tial advantage in the application of this polymer in solidphase extraction technique using the flow injection meth-odology. The specific surface area of PDAN was 6.73 m2/g,according to BET equation. The pore size is mainly locatedat the macroporous region, which may favor the masstransfer in the subsequent sorption process. The resultsof the elemental analysis of the dried particles showed thatthe repeated unit of the polymer should be as {C20H15.N3.}n.It suggests that denitrogenation happens during polymeri-zation, which confirmed the earlier report [17].

To establish probably the structure of the formed poly-mers the IR spectra were recorded. The most importantrange on the spectra is that of amine N-H stretching vibra-tions, which is shown in Fig. 2. In this range, the spectrumof the monomer shows two main bands characteristicallylocated about 80 cm�1 from one another and attributableto mNH2AS and mNH2AS, respectively, at 3385 and 3470 cm�1.

J. Rutkowska et al. / European Polymer Journal 44 (2008) 2108–2114 2111

The spectrum of the polymer shows only a very broad mul-ticomponent band with maximum located at 3403 cm�1,this probably results from a mixture of primary and sec-ondary amines. This change in spectra is characteristicfor polymerization reaction via –NH–NH–bond and wasobserved in the thin film of this polymer synthesized onelectrodes [15,16].

3.2. Sorption of metal ions

The amino and/or imino groups of PDAN, which do notparticipate in the polymerization reaction, are capable ofaccumulating metal ions through a complexation reaction[14,15]. This reaction is dependent on the pH of a samplesolution due to the competition between chelate forminggroups and H+ in the solution. The effect of pH on the sorp-tion of some divalent metal ions (Cd(II), Cu(II), Ni(II),Mn(II), Zn(II) and Pb(II)) was examined by the batch proce-dure in the range of 3.0–6.0. For comparison similar exper-iments were conducted using the very popular chelatingsorbent Chelex 100 containing iminodiacetic functionalgroups [20]. The obtained results are presented in Fig. 4.

Generally, the more favourable results for sorption ofmetal ions onto PDAN particles were observed at higherpH values. Although, sorption of Cu(II) reached almost70% even at pH 3. To the contrary, retention of Mn(II) doesnot change so much with the increase of sample acidityand at pH 6 is below 18%. The retention of the examinedmetal ions at pH 4 for poly(1,8-DAN) sorbent decreasesin the order: Cu (II)� Pb(II)� Ni(II) > Mn(II) > Zn(II) > C-d(II). The pH studies revealed selective sorption of metalions onto Chelex 100 resin (Fig. 2). At pH > 4.5 a maximumand steady sorption is observed. The PDAN sorbent seemsto be very specific for the enrichment of copper ions andtheir simultaneous separation from other metals. Theselectivity coefficients (bCu/M), defined as the ratio of thedistribution coefficient (Kd) for Cu(II) and other metal ion,were 20, 35, 49 and 198 for nickel, manganese, cadmiumand zinc ions, respectively, at pH 3. This means that Cu(II)can be determined after separation when the presence ofthese metal ions causes some interferences duringmeasurement.

3.3. Sorption capacity

The sorption capacity of the PDAN particles towardsCu(II) was determined after saturation of the polymer(25 mg) with copper ions (1–10 lmol/L) at pH 3.5. Themaximum adsorption, which represents saturation of ac-tive points available for Cu(II) ions on the polymers, was23.0 mg/g (0.359 mmol/g). The obtained value is higherthan that reported recently for various chelate functional-ized solid phase extraction materials such as p-tert-butyl-calix[4]arene-1,2-crown-4-anchored chloromethylatedpolymeric resin beads [21], TDMBAC-treated analcimepyrocatechol-immobilized [22] and imprinted polymeth-acrylic microbeads with 4-(2-pyridylazo) resorcinol as aspecific Cu(II) ligand [23].

The rate of Cu(II) uptake by PDAN was studied understatic conditions. 150 mg of sorbent was equilibrated witha 10 mL of 1 lg/mL copper solution for different times at

room temperature. The sorption profiles are shown inFig. 5. Half saturation of the sorbent was achieved in lessthan 10 min and did not change significantly with pH. After30 min the equilibrium was attained, resulting in about90–95% sorption.

In order to examine the controlling mechanism of Cu(II)sorption process, pseudo-first and second order kineticsmodels were used to test the experimental data [24]. A ki-netic model for sorption analysis is the pseudo-first orderrate expression in the form:

dqt=dt ¼ k1ðqe � qtÞ ð1Þ

Integrating this for the boundary conditions t = 0 � tand qt = 0 � q, Eq. (1) may be rearranged for linearized dataplotting as shown by Eq. (2):

logðqe � qtÞ ¼ log qt � k1=2303 � t ð2Þ

where k1 is the rate constant for first order sorption (1/min), qe – is the amount of copper ions sorbed at equilib-rium (mg/g), qt the amount of copper ions sorbed on thesurface of poly(1,8-DAN) at any time t (mg/g). A plot oflog(qe–qt) versus time will give a straight line and fromthe gradient k1 can be obtained.

The kinetic rate equation for the pseudo-second orderrate sorption can be written as follows:

dqt=dt ¼ k2ðqe � qtÞ2 ð3Þ

where k2 is the rate constant of sorption (g/mg min). Inte-grating Eq. (3) for the boundary conditions and rearranginggives:

t=q ¼ 1=k2q2e þ 1=qe � t ð4Þ

Thus, a plot of t/qt against t of Eq. (4) should give a linearrelationship with a slope of 1/ge and an intercept of 1=k2q2

e .The parameters obtained from the slopes and intercepts

for both the models of sorption are presented in Table 1.The theoretical qe estimated from pseudo-first order ki-netic model is much closer to the experimental value andthe obtained correlation coefficients for this mechanismare >0.992, not significantly depending on pH. The correla-tion coefficients for the linear plots of t/qe against timefrom the pseudo-second order rate law are lower. These re-sults suggest that the first order mechanism is predomi-nant and that diffusion might be the rate-limiting stepthat controls the sorption process. The rate-controllingmechanism may vary during the course of the sorptionmechanism [25]. There is an external surface mass transferor film diffusion that controls the early stages of the sorp-tion process, followed by a reaction between ions andfunctional groups of the sorbent and finally by a diffusionstage where the sorption process slows down considerably.

3.4. Dynamic sorption and desorption of copper ions

In order to show the applicability of PDAN for precon-centration of Cu(II), its sorption was investigated using adynamic approach. When the polymer was packed in themicrocolumn prepared from conventional pipette tips ora polyethylene syringe tube as well as from a filter disc,back pressure problems affected its performance. Thus,the enrichment unit was prepared from PTFE tubing

3.0 3.5 4.0 4.5 5.0 5.5 6.00

20

40

60

80

100S

orpt

ion.

%

pH3.0 3.5 4.0 4.5 5.0 5.5 6.0

0

20

40

60

80

Sor

ptio

n. %

pH

3.0 3.5 4.0 4.5 5.0 5.5 6.00

20

40

60

80

100

Sor

ptio

n. %

pH

3.0 3.5 4.0 4.5 5.0 5.5 6.00

20

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100

Sor

ptio

n. %

pH

3.0 3.5 4.0 4.5 5.0 5.5 6.00

20

40

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100

Sor

ptio

n. %

pH3.0 3.5 4.0 4.5 5.0 5.5 6.0

0

20

40

60

80

100

Sor

ptio

n. %

pH

Mn(II)Zn(II)

Cu(II)

Ni(II)

Pb(II)

Cd(II)

Fig. 4. Sorption profiles of metal ions on (s) PDAN and (j) Chelex 100 in the function of pH. Initial metal concentration 1 lg/mL, mass of sorbent 15 mg.

2112 J. Rutkowska et al. / European Polymer Journal 44 (2008) 2108–2114

(1.5 m long, 0.5 mm i.d.) by typing 36 interlaced knots ofapproximately 10 mm loops. Such knotted reactors havebeen used for sorption of neutral hydrophobic metal com-plexes, mostly with dithiocarbamates and diethyldithio-phosphate [26,27]. They produce significantly lower backpressures than packed columns at similar flow rates, sothat higher sample loading rates could be applied. Detailsof the preparation of the used knotted reactor with PDANare given in Section 2.

The on-line preconcentration system was optimised bythe univariate method with the purpose of determining thechemical conditions and the optimum flow rates for sorp-tion and desorption of Cu(II). A time-based system (Fig. 3)was applied for used FI configuration because it is moreflexible as time can be changed in order to load the desiredamount of analyte onto the microcolumn. The experimentsperformed in the dynamic conditions confirmed that theoptimum pH equals 3.5 for a maximum binding capacity

Table 2Determination of Cu(II) in natural water samples (lg/L)

Sample Added Founda Recovery, %

Tap water – 2.4 ± 0.9 –10.0 12.3 ± 0.7 101.0 ± 2.5

Underground water 9.6 ± 0.6 –10.0 19.4 ± 0.4 105.6 ± 0.8

a Mean value ± SD (n = 3).

5 10 15 20 25 30

0.0

0.2

0.4

0.6

0.8

C/C

0

Time. min

pH 3pH 4pH 5

Fig. 5. Sorption rate curves of Cu(II) onto PDAN at different pH; co = 1 mg/L.

Table 1Kinetic parameters for sorption of Cu(II) on PDAN

pH First-order kinetic Second-order kinetic

k1 qe R2 k2 qe R2

3 0.107 16.5 0.9923 20.8 0.078 0.98804 0.109 15.6 0.9959 15.7 0.095 0.96265 0.110 15.4 0.9986 17.0 0.097 0.9346

J. Rutkowska et al. / European Polymer Journal 44 (2008) 2108–2114 2113

of PDAN towards Cu(II) as well as separation purposes. Insolid phase extraction system, the flow rate of the samplesolution is one of the most important parameters, whichnot only affects the recovery of the analyte, but also con-trols the time of analysis. The studies showed that Cu(II)can be retained quantitatively on the inner walls of theused knotted reactor with PDAN at a flow rate up to1.4 mL/min. At higher flow rates, the sorption of metal ionswas lower owing to short residence time of the sample. Forthe elution of Cu(II) ions from the knotted reactor, nitricacid was assayed at different concentrations and volumes.A concentration of 2 mol/L was required to obtain quanti-tative elution if HNO3 volume was set to 0.5 mL with a flowrate of 14.3 mL/min.

Under the stated conditions a linear correlation be-tween the absorbance and the copper concentration wasobtained up to 50 lg/L of Cu(II) with a correlation coeffi-cient of 0.9895 using 1.5 m long knotted reactor withPDAN and a 5 min sample loading time. The linear rangecould be significantly improved by increasing the micro-column length (amount of PDAN particles), but simulta-neously with the increase in the treatment time. Theefficiency of preconcentration essentially also depends onthe time taken for the sample solution to pass through amicrocolumn. The application of longer loading time im-proves the enrichment, but simultaneously leads to a de-crease in the sample rate. The obtained limit of detection(2.9 lg/L) was based on three times the standard deviationof the blank solution measurements. The precision of themethod assessed as relative standard deviation (RSD) of10 independent preconcentration cycles using samplesolution containing 50 lg/L of Cu(II) was 3.2%.

To study the accuracy of the method and the possibleeffects from the real matrix, the recovery tests were ap-plied to natural water samples. The aliquots of waterswere adjusted to pH 3.5, spiked with 10 lg/L of Cu(II)solution and submitted to the preconcentration proce-dure. The results presented in Table 2 demonstrate theapplicability of the method to water analysis. The valid-ity of the proposed procedure was checked for coppercontent in standard reference material NIST 1640e. Itwas found that there is no significant difference (confi-dence interval at 95% using t-test) between the achievedresults (22.9 ± 0.6 lg/L) and the certified content(22.2 ± 0.3 lg/L). Thus, our methodology was shown tobe an effective approach for improving the sensitivityof flame AAS copper determination in natural water sam-ples. Moreover, the addition of chelating agent and or-ganic solvent, which are most commonly used in SPEpreconcentration systems with an activated carbon[28,29], is not necessary.

Acknowledgement

This research was carried out in the framework of the501/68-BW-172107 project.

References

[1] Hansen EH, Miró M. How flow-injection analysis (FIA) over the past25 years has changed our way of performing chemical analysis.Trends Anal Chem 2007;26:18.

[2] Camel V. Solid phase extraction of trace elements. Spectrochim ActaPart B 2003;58:1177.

[3] Cerutti S, Martinez LD, Wuilloud RG. Knotted reactors and their rolein flow-injection on-line preconcentration systems coupled toatomic spectrometry-based detectors. App Spectrosc Rev2005;40:71.

[4] Garrido L, Soto RM, Carlosena A, Lopez-Mahia P, Munategui S, PradaD. Flame atomic absorption spectrometry with flow-injection on-line adsorption preconcentration using a knotted reactor forcadmium determination in aqueous samples. Anal Lett2001;34:1763.

[5] Yan XP, Li Y, Jiang Y. Selective measurement of ultratracemethylmercury in fish by flow injection on-line microcolumndisplacement sorption preconcentration and separation coupledwith electrothermal atomic absorption spectrometry. Anal Chem2003;75:2251.

[6] Liawruangrath S, Som-aum W, Thowshend A. A comparison ofenrichment factor of knotted and serpentine reactors using flowinjection sorption and preconcentration for the off-linedetermination of some trace elements by inductively coupledplasma mass spectrometry. Talanta 2002;58:1177.

[7] Herbello-Hermelo P, Barciela-Alonso MC, Bermejo-Barrera A,Bermejo-Barrera P. Flow on-line sorption preconcentration in aknotted reactor coupled with electrothermal atomic absorptionspectrometry for selective As(III) determination in sea-watersamples. J Anal Atom Spectrom 2005;20:662.

[8] Anthemidis AN, Ioannou KIG. Evaluation of polychlorotri-fluoroethylene as sorbent material for on-line solid phase

2114 J. Rutkowska et al. / European Polymer Journal 44 (2008) 2108–2114

extraction systems: determination of copper and lead by flameatomic absorption spectrometry in water samples. Anal Chim Acta2006;575:126.

[9] Rao PT, Praveen RS, Daniel S. Styrene-divinyl benzene copolymers:synthesis, characterization and their role in inorganic trace analysis.Crit Rev Anal Chem 2004;34:177.

[10] Bagheri H, Mohammadi A. Pyrrole-based conductive polymer as thesolid-phase extraction medium for the preconcentration ofenvironmental pollutants in water samples followed by gaschromatography with flame ionization and mass spectrometrydetection. J Chromatogr A 2003;1015:23.

[11] Tagowska M, Pałys B, Mazur M, Skompska M, Jackowska K. In situdeposition of poly(1,8-diaminonapthalene): from thin films tonanometer-sized structures. Electrochim Acta 2005;50:2263.

[12] Rohwerder M, Michalik A. Conducting polymers for corrosionprotection: what makes the difference between failure andsuccess? Electrochim Acta 2007;53:1300.

[13] Lai CZ, Fierke MA, Stein A, Buhlmann P. Ion-selective electrodes withthree-dimensionally ordered macroporous carbon as the solidcontact. Anal Chem 2007;79:4621.

[14] Huang MR, Peng QY, Li XG. Rapid and effective adsorption of leadions on fine poly(phenylenediamine) microparticles. Chem Eur J2006;12:4341.

[15] Nasalska A, Skompska M. Removal of toxic chromate ions by the filmof poly(1,8-diaminonapthalene). J Appl Electrochem 2003;33:113.

[16] Pałys B, Skompska M, Jackowska K. Sensitivity of poly 1,8-diaminonapthalene to heavy metal ions – electrochemical andvibrational spectra studies. J Electroanal Chem 1997;433:41.

[17] Li XG, Huang MR, Li SX. Facile synthesis of poly(1,8-diaminonapthalene) microparticles with a very high silver-ionadsorbability by a chemical oxidative polymerization. Acta Mater2004;52:5363.

[18] Li XG, Liu R, Huang MR. Facile synthesis and highly reactivesilver ion adsorption of novel microparticles ofsulfodiphenylamine and diaminonapthhalene copolymers. ChemMater 2005;17:5411.

[19] Huang MR, Lu HJ, Li XG. Efficient multicyclic sorption and desorptionof lead ions on facilely prepared poly(m-phenylenediamine)

particles with extremely strong chemoresistance. J. ColloidInterface Sci 2007;313:72.

[20] Rahmi D, Zhu Y, Fuimori E, Umemura T, Haraguchi H. Multielementdetermination of trace metals in seawater by ICP-MS with aid ofdown-sized chelating resin-packed minicolumn for preconcentration.Talanta 2007;72:601.

[21] Seyhan S, Çolak M, Demirel N. Solid phase extractivepreconcentration of trace metals using p-tert-butylcalix[4]arene-1,2-crown-4-anchored chloromethylated polymeric resin beads.Anal Chim Acta 2007;584:462.

[22] Afzali D, Mostafavi A, Taher MA, Moradian A. Flame atomicabsorption spectrometry determination of trace amounts of copperafter separation and preconcentration onto TDMBAC-treatedanalcime pyrocatechol-immobilized. Talanta 2007;71:971.

[23] Dakova I, Karadjova L, Ivanov L, Georgieva V, Evtimova B, Georgiev G.Solid phase selective separation and preconcentration of Cu(II) byCu(II)-imprinted polymethacrylic microbeads. Anal Chim Acta2007;584:196.

[24] Ho YS, McKay G. Pseudo-second order model for sorption processes.Process Biochem 1999;34:451.

[25] Pyrzynska K, Kilian K. Kinetic study of metal sorption on a resinmodified with terakis(carboxyphenyl)porphyrin. Microchim Acta2002;142:67.

[26] Benkhedda K, Infante HG, Adams FC. Inductively coupled plasmamass spectrometry for trace analysis using flow injection on-linepreconcentration and time-of-flight mass analyser. Trends AnalChem 2002;21:332.

[27] Yan XP, Jiang Y. Flow injection on-line preconcentration andseparation coupled with atomic (mass) spectrometry for traceelement (speciation) analysis based on sorption of organo-metalliccomplexes in a knotted reactor. Trends Anal Chem 2001;20:552.

[28] Soylak M, Narin I, Dogan M. Trace enrichment and atomic absorptionspectrometric determination of lead, copper, cadmium and nickel indrinking water samples, by use of an activated carbon column. AnalLett 1997;30:2801.

[29] Soylak M. Determination of trace amounts of copper in high-purityaluminium samples after preconcentration on an activated carboncolumn. Fresenius Environ Bull 1998;7:383.