научная статья по теме LEAD(II) ION SELECTIVE POLY(ANILINE) SOLID CONTACT ELECTRODE BASED ON 1,2-BIS(N-BENZOYLTHIOUREIDO)ETHANE, -PROPANE AND -BUTANE IONOPHORESK Химия

Текст научной статьи на тему «LEAD(II) ION SELECTIVE POLY(ANILINE) SOLID CONTACT ELECTRODE BASED ON 1,2-BIS(N-BENZOYLTHIOUREIDO)ETHANE, -PROPANE AND -BUTANE IONOPHORESK»

ЖУРНАЛ АНАЛИТИЧЕСКОЙ ХИМИИ, 2015, том 70, № 5, с. 537-542

ОРИГИНАЛЬНЫЕ СТАТЬИ

УДК 543

LEAD(II) ION SELECTIVE POLY(ANILINE) SOLID CONTACT ELECTRODE BASED ON 1,2-BIS(N'-BENZOYLTHIOUREIDO)ETHANE,

-PROPANE AND -BUTANE IONOPHORESK © 2015 Young-Hoon Lee*, Won-Sik Han*, Hak-Joo Lee*, Sung-Min Ahn**, Tae-Kee Hong*, 1

*Department of Chemistry, Hanseo University Seosan, Choong-Nam, Korea 1E-mail: tkhong1@hanseo.ac.kr **Department of Radiological Science, Gachon University Incheon, Korea Received 29.01.2013; in final form 20.11.2014

The lead ion selective electrodes were manufactured by synthesizing a benzoyl thioureido group ionophores having two sulfur groups on the both ends of ethane, propane and butane molecules. The ionophore containing propane moiety showed the best responsivity to lead ion. With the 1,3-bis(N,N'-benzoylthioureido)pro-pane (BTP) ionophore, the best result was found when it included with the o-nitrophenyloctylether (o-NPOE) plasticizer with the highest permittivity and the oleic acid (OA) additive. The ratio of BTP : polyvinyl chloride : : o-NPOE : potassium tetrakis(4-chlorophenyl)borate : OA was 2.5 : 16.5 : 30.5 : 1.5 : 0.5, the response range was 1.0 x 10-64-1.0 x 10-10 M, and the response slope was 30.4 mV/decade. Addition of OA led to an excellent result for the responsivity, cation interference effect, correlation coefficient, response time and reproducibility. The electrode represented constant characteristics irrelevant to variation of pH between 2—7, the stabilization time was 30 s, the response time was about 30 s, and the reproducibility represented ±0.81 and ±1.40 mV for 1.0 x 10-20 and 1.0 x 10-30 M lead, respectively.

Keywords: lead ion, sensor, ion selective electrode, solid contact electrode, bis-thiourea, ionophore.

DOI: 10.7868/S0044450215050199

Lead is discharged into the atmosphere and rivers etc., and thus it has given rise to serious environmental problems [1]. Lead has polluted air, land and water etc. heavily by the atmospheric circulation [2]. Most of lead exists as divalent Pb2+ ions in the living environment, that causes a disorder of the nervous system or act as kidney's carcinogens when entering the human's body. In particular, lead poisoning is known to cause many diseases [3]. For this reason, measurement of lead concentration became a very important factor, and a diversity of methods have been exploited for that purpose [4—6], including atomic absorption spectroscopy, ion chromatography, X-ray fluorescence spec-troscopy, inductively coupled plasma spectroscopy etc. [7, 8]. Most of these spectroscopic methods could have lower detection limits, relatively high accuracy and good reproducibility to give reliable results; they need expensive equipment, are costly for use, experimental process is complicated and difficult, skilled technicians are required, and the place and time is limited. A variety of methods have been studied to complement these shortcomings, of them, ion selective electrodes (ISEs) have been studied actively [9— 11]. A mixture of lead tetraphenyl borate and poly-

alkoxylate could be successfully used as ion-selective material in the heterogeneous membranes of lead ISEs [12]. Lead chelates of naphthalene-1-dithiocarboxy-late [13], inorganic exchanger bismuth tungstate [14] were used as membrane active components. Crown ethers and calixarenes have been found selective for lead ions and used to prepare highly selective electrodes for lead ions: 1,10-dibenzyl-1,10-diaza-18-crown-6 [15], 4'-vinylbenzo-15-crown-5 homopolymer [16], calix[4]arene derivative [17, 18], calixarene carboxyphenyl azo derivative [19], phosphorylated calix[4]arene derivative [20], phosphorate functional-ized caly[4]arenas [21], ^-tert-buthylcalix[4]arene derivative [22], a substituted azacrown [23] have also been successfully used as electroactive materials to develop ISEs for lead. 2,2'-Dithiodibenzoic acid [24], 5,5'-dithiobis(2-nitrobenzoic acid) [25], polyaminoan-thraquinone [26], 1-furoil-3,3-diethylthiourea [27], 2-(((E)-2-((E)-1-(2-hydroxyphenyl)methyliden)hydrazo-no)methyl) phenol [28], N,N'-bisthiophen-2-ylmethyl-ene-pyridine-2,6-diamine [29], N,N'-bisthiophene-2-ylmethylene-ethane-1,2-diamine [30], N,N-dibenzyl-1,4,10,13-tetraoxa-7,16-diaza cyclooctadecane [31], dimethylene bis(4-methylpiperidine dithiocarbamate)

[32] have also been used as electroactive materials in lead ISEs. However, these sensors exhibit narrow working concentration ranges, high response time and suffer interference from some metal ions.

This paper examines the lead ion selective solid contact electrodes (SCEs) which uses three iono-phores; 1,2-bis(N'-benzoylthioureido)ethane (BTE), 1,3-bis(N'-benzoylthioureido)propane, and 1,3-bis(N'-benzoylthioureido)butane (BTB) by introducing a benzoylthioureido group that has two sulfur groups on the both edges of ethane, propane and butane. We would like to find a structure most suitable to the lead ion response by adjusting the space between two sulfur atoms in the ionophore, to manufacture SCEs with this ionophore and study the response characteristics resulting from Pb2+ in solution such as response slope, range, cation interference effect, stabilization and response time, reproducibility, and stability for pH.

EXPERIMENTAL

Reagents. Aniline and tetrahydrofuran (THF) were purified by vacuum distillation. For all experiments, analytical grade chemicals and doubly distilled and dem-ineralized water were used. The membrane matrix high molecular weight polyvinyl chloride (PVC) (n = 1100), ammonium thiocyanate, benzoyl chloride, the anionic additive potassium tetrakis(4-chlorophenyl)borate (KTpClPB), the plasticizers 2-nitrophenyloctylether, tris(ethylhexyl) phosphate (TEHP), bis(2-ethylhexyl)ad-ipate (DOA), dioctylphthalate (DOP), and bis(2-ethyl-hexyl)sebacate (DOS), dibutylphthalate (DBP), oleic acid, aniline, and THF were from Sigma-Aldich Co.

Polymerization [33]. Electrochemical experiments were performed in a conventional cell with three electrodes. A saturated calomel electrode was used as the reference electrode and all potentials were recorded and reported with respect to this electrode. Platinum wires (1 mm in diameter, 50 mm in length) were used as the working and counter electrodes. Electro-polymerization was carried out at the one end of a platinum wire by cyclic voltammetry in 3.0 x 10-2 M aniline and 6.0 x 10-2 M HCl solution. Cyclic voltam-mograms were recorded using a potentiostat (EG&G 273A). For electrochemical polymerization of aniline, the potential was swept between 0.0 and 1.0 V at scan rate of 100 mV/s. The potential cycling was repeated up to 30 cycles and stopped at 1.0 V. After electrodepo-sition, the poly(aniline) was washed out with distilled water and the electrode was dried for 24 h in an 80°C oven. Then the platinum part of Pt-poly(aniline) electrode was covered with a thermo-contractive insulation tube.

Synthesis of ionophore [34]. To a mixture of 25 mmol of ammonium thiocyanate and 25 mL of acetone, a solution formed by 25 mmol benzoyl chloride in 13 mL of acetone was added dropwise. The resulting

mixture was stirred under reflux for 1 h and cooled to room temperature. A solution of 12.5 mmol of1,2-di-aminoethane (1,3-diaminopropane or 1,4-diaminob-utane) in 5 mL of acetone was added. The solution obtained was stirred at room temperature during 2 h. After the reaction, the mixture was slowly poured into 600 mL of iced water with strong stirring. The bis-thiourea precipitated was filtered and washed with 3 x x 50 mL of water and vacuum dried. For the recrystal-lization, a mixture of methanol : chloroform (1 : 1) was employed.

Preparation of cocktail solutions and fabrication of solid contact electrodes. Typical cocktail solution consisted of ionophore 2.5 mg : PVC 16.5 mg : plasticizer 30.5 mg : KTpClPB 1.5-2.0 mg or OA 0-0.5 mg. All components were dissolved in THF. The SCEs were produced by dipping the Pt-poly(aniline) electrode directly into the cocktail solution to coat it with a thin film. The resulting solid contact electrode contained three layers of Pt/electro-conductive polymer/PVC film with an ionophore with a thickness of2.5 ± 0.1 mm.

EMF measurements. The EMF values were measured at 20 ± 0.2°C using a model 355 Ion-analyzer (Mettler-Toledo Ltd., England). In all experiments, the pH measurements of the sample solutions were determined with a Mettler-Toledo InLab 412 glass electrode. The external reference electrode was a double-junction calomel electrode Orion 90-20-00 (Orion Research, USA). The standard deviation arising from this equipment was <0.1 mV for a single determination. Before use, the electrodes were conditioned in distilled water for at least 2 h.

Lead standard sample solution. A stock solution (0.10 M) of lead nitrate was prepared by pH 5.5 Tris buffer solution. Dilute solutions (1.0 x 10-2 to 1.0 x x 10-7 M) of lead nitrate were freshly prepared by diluting the stock solution with doubly distilled water and Tris buffer of pH 5.5.

Measurements of stabilization time and response time [35]. The stabilization time was obtained as follows. First, the dry electrode was deposited in a 1.0 x x 10-3 M (pH 5.5) Tris buffer lead nitrate solution. Then the time until the potential stabilized to lower than ±0.1 mV/min was measured. The response time was obtained as follows. After the response potential of the electrode had stabilized, 10.00 mL of1.0 x 10-2 M lead nitrate (pH 5.5) Tris buffer solution was added to the 1.0 x 10-3 M pH 5.5 Tris buffer lead nitrate solution while vigorous stirring. Then the time until the potential stabilized to lower than ±0.1 mV/min was measured.

Selectivity of the developed sensors. The lead sensor was immersed in the 1.0 x 10-3 M lead nitrate solution that was adjusted to pH 5.5 with Tris buffer, and the potential was measured. The potentials of1.0 x 10-3 M solution of the interferent adjusted to pH 5.5 were measured. The selectivity coefficients ^Pb.M were deter

Для дальнейшего прочтения статьи необходимо приобрести полный текст. Статьи высылаются в формате PDF на указанную при оплате почту. Время доставки составляет менее 10 минут. Стоимость одной статьи — 150 рублей.

Показать целиком