Talanta 86 (2011) 121 127

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Talanta

j ourna l ho me page: www.elsev ier .com

Novel m poon phe

Nishith R hanDepartment of ujara

a r t i c l

Article history:Received 10 JuReceived in reAccepted 24 AAvailable onlin

Keywords:Phenylurea suIon selective eMonohydrogeAnion recogniSensor

memonohV deetectery s

of sh aniondrogt dete

1. Introdu

Supramolecular chemistry of anions has been a eld of growinginterest during the last few years and there has been a large numberof appealing reviews on the chemistry of anion recognition as wellas on the development of host receptors for anions [13]. The inter-est in ion-seare easy-todeterminatwith a reastion of minspecial attebased on sohave shownand anions.

A great nextensive aption of respewhich are eriers in memembrane MacrocyclicN, S, O, etc.possess thedimensions

CorresponE-mail add

etalsdesign of sensors. Calixarenes are fascinating objects for the studyof host guest interactions with pronounced binding afnities to var-ious metals. The ease of chemical modication is one of the mainattractive features of calixarenes as it enables alterations in theion-complexing selectivity by simply switching from one ligating

0039-9140/$ doi:10.1016/j.lective electrodes has grown over recent years as they-use devices that allow rapid and accurate analyticalion of chemical species at relatively low concentrations,onable selectivity and low cost. The rapid determina-ute quantities of ionic species by simple methods is ofntion in analytical chemistry. Ion selective electrodeslvent polymeric membrane incorporating ion carriers

to be very useful tools for the analysis of many cations

umber of ionophores have been developed and foundplications in potentiometric sensors for the determina-ctive ions in real samples. The macrocyclic compounds,xcellent ionophores, are being employed as the car-tal selective extraction, phase transfer catalysis andtransport as they bind the metal ions selectively [47].

compounds are cyclic, organic molecules containing capable of forming electron rich interior cavities and

ability to complex with metal ions of compatible. Complexation studies between macrocyclic ligands

ding author. Tel.: +91 79 26302286; fax: +91 79 26308545.ress: shobhanamenon07@gmail.com (S.K. Menon).

functional group to another. The uses of calixarenes as the basis forion-recognition in cation sensor systems is well established [812].A few calixarene derivatives for anion binding have been reported[1316].

The signicance of monitoring phosphate concentration lev-els spans all areas of science and technology. A system that cancontinuously and selectively detect phosphates levels in aque-ous solutions will nd numerous applications in elds, such asenvironmental monitoring, biomedical research, clinical chemistryand pharmacology because phosphorus is an essential mineral forthe human body and all other living organisms [1721]. Mea-surement of phosphate levels in environmental water samples isusually achieved using laboratory-based automated ow appara-tus. A number of investigations, into the development of severalphosphate-selective electrodes, have been reported in the lit-erature [2225]. Organotin complexes have been ourishing inthe past as phosphate-selective ionophores in PVC-based ISEs[2628], along with thiourea compounds [29,30], uranyl salophenederivatives [31,32], molybdenum-based compound [24], cyclicpolyamine compounds [33,34], modied calix[6]arene deriva-tive [35] and also an organoborane complex [36]. Still manyproblems like interference of other anions, lower detectionlimit, lifetime and longer response time have been encountered.

see front matter 2011 Elsevier B.V. All rights reserved.talanta.2011.08.042onohydrogenphosphate ion-selective nyl urea substituted calix[4]arene

. Modi, Bhargav Patel, Manishkumar B. Patel, ShobChemistry, School of Sciences, Gujarat University, Navrangpura, Ahmedabad 380009, G

e i n f o

ne 2011vised form 23 August 2011ugust 2011e 30 August 2011

bstituted calix[4]arenelectroden phosphatetion

a b s t r a c t

A highly selective and sensitive PVC found to be a suitable ionophore for mresponse (with a slope of 29.4 0.3 m6.0 1081.0 101 mol L1 with a din the whole concentration range is vThe sensor possesses the advantagestowards a large number of inorganicin potentiometric titration of monohywas successfully applied for the direc

ction and m/ locate / ta lanta

lymeric membrane sensor based

a K. Menon

t, India

brane, containing phenylurea substituted calix[4]arene wasydrogen phosphate (HPO42) ions that exhibited a Nernstiancade1). The working concentration range of the electrode wasion limit of 2.0 108 mol L1. The response time of the sensorhort (

122 N.R. Modi et al. / Talanta 86 (2011) 121 127

Calixarene derivatives, whose lower rim has been modied withanion-complexing functional groups, such as esters and amides,make excellent ionophores for use in ion-selective electrodes. Wehave explored the sensing properties of the macrocyclic com-pounds, and have recently reported the mercury selective [37],thiocyanate selective [38], dihydrogen phosphate selective [39],glucose selective [40] and neodymium selective [41] membraneelectrodes. These ndings motivated us to synthesize phenylureasubstituted calix[4]arene, which may allow selective and efciention sensing of anions.

Herein, we report extremely selective and responsive mono-hydrogenphosphate membrane electrode by phenylurea modiedcalix[4]arene as an exceptional ion carrier for quick and precisedetermination of monohydrogenphosphate in real sample.

2. Experim

2.1. Reagen

All the rSodium tet(O-NPOE) wwas obtainefrom Merckany furtherQ water waDilutions of

2.2. Synthe

2.2.1. SynthScheme

thesis (16)calix(4)arento the literaillustrated a

2.2.2. Synthurea)-26,28

The cbis(chloroc(1.66 g; 1.8in dry THFand the solwere madewith continmixture waof the solvdiluted withmaterial wadistilled waethanolTHcalc. C46H45.03; N: 16.(NHCO),

1. Synthesis of phenyl urea substituted calix[4]arene (iv). (i) AlCl3, (ii) dry acetone, ethyl bromoacetate, K2CO3; (iii) KOH:EtOH; (iv) SOCl2,; (v) phenyl urea, dry THF.

), 8.50 (s, 4H, NH), 4.25 (s, 12H, ArCH2Ar (bridge) and), 6.707.30 (s, 22H, ArH). 13C NMR (CDCl3) 165,162,41, 128, 123, 121, 115 and 113 (ArC), 23, 17.18, 12.0). FAB MS (m/z) 778 (M+2).

ectrode preparation

examination was carried out on a number of membranesed by varying the concentration of ionophore, plasticizerifferent additives and are summarized in Table 1. Theo prepare the best PVC membrane was to mix thoroughlyof powdered poly vinyl chloride, 60 mg of plasticizer o-

henyloctylether (NPOE), 4 mg of sodium tetraphenyl borateg of ionophore. Then the mixture was dissolved in 5 mL of

F. The suspension was stirred until all the PVC was dissolved.sulting solution was carefully cast into a slide glass and leftg for 24 h in a Petri dish to allow THF to evaporate slowly,

n oily concentrated mixture was obtained.

Table 1Composition (

No. Slope (mV decade1) Linear range (mol L1)

1 31.1 0.3 2.4 1051.0 1022 21.9 0.4 3.2 1051.0 1013 24.0 0.3 1.8 1061.0 1014 32.8 0.2 4.0 1061.0 1025 29.4 0.3 6.0 1081.0 1016 27.3 0.4 3.9 1051.0 101ental

ts and materials

eagents and chemicals used were of analytical grade.raphenyl borate (NaTPB) and o-nitrophenyloctyletherere purchased from Merck. Poly vinyl chloride (PVC)d from MCC, India. Potassium salts of all anions used (all) were of the highest purity available and used without

purication except for vacuum drying over P2O5. Milli-s used for preparing the stock solution of metal salts.

the stock solution were also done by Milli-Q water.

sis of ionophore

esis of phenyl urea substituted calix[4]arene1 illustrates the successive steps of the ionophore syn-. 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrahydroxye (1) and compounds 15 were synthesized accordingture methods [42,43]. The synthesis of compounds 6 iss follows:

esis of 5,11,17,23-tetra-tert-butyl-25,27-bis(phenyl-dihydroxy calix[4]arene (6)ompound 5 (5,11,17,23-tetra-tert-butyl-25,27-

arbonyl-methoxy)-26,28 dihidroxy calix[4]arene)9 mmol), obtained in the previous step was dissolved

(75 mL). The addition of pyridine (2 mL; 12.4 mmol)ution of phenyl urea (1.3 g; 9.5 mmol) in THF (15 mL)

sequentially and added drop wise in a period of 30 minuous stirring at room temperature (30 C). The reactions then stirred and reuxed for 4 h, after which mostent was distilled off under vacuum. The residue was

water (100 mL) and neutralized by 0.1 M HCl. The solids then ltered and washed with 1 N HCl, NaHCO3 andter sequentially. Recrystallization of the residue fromF furnished 6. Yield 1.5 g (81%), m.p. 203205 C. Anal.0N4O8: C: 71.13; H: 5.15; N: 16.49% found: C: 71; H:26%. FT-IR (KBr) : 3390 cm1 (NH), 16701650 cm1

1145 cm1 (COC). 1H NMR (CDCl3) 9.80 (s, 2H,

Schemetoluene;dry THF

ArOHCH2O145, 1(CH2

2.3. El

Thepreparand droute t30 mg nitropand 6 mdry THThe restandinuntil a

%) of membranes and response characteristics of the electrode.

Ionophore PVC O-NPOE NaTPB

5 25 65 5 6 28 60 6 7 30 55 8 5 32 58 5 6 30 60 4 7 25 65 3

N.R. Modi et al. / Talanta 86 (2011) 121 127 123

A nal transparent membrane of about 0.5 mm thickness wasobtained. In order to avoid drastic variation in the thickness andmorphology of the membrane, the viscosity of the solution andsolvent evaporation was carefully controlled. The membrane wasthen cut to with araldi(1.0 10324 h by soathat gave reselected forused as an i

2.4. Conditi

The prepferent concwith side b(1.0 101measured bphate in tesThe standarthe gradualtion. The binner electr

All the Eassembly:

Ag/AgCl/membrane/Model PHMat 25 1 C

The actaccording tequation [4

log = 0.

where is

3. Results

Literaturity patternsthe series, hydrogenphnon-Hofmeapproachesis the use ohydrophilicrelaying ininteractionsexperimentthe construThe potentthe membraions over otto be the rand HPO42

positive ionphosphoricnium hydrono signicaear range. HNa+ were nosenses only

F

vis

he pres wV/visinguochrract

2). Ae, brvestotedcy to the MHP ions compared to other common anions.

fect of the membrane composition

known that the sensitivity, linear dynamic range, and selec-f the ISEs depend not only on the nature of the carrier used,o signicantly on the membrane composition and the prop-of the additives employed [5153]. Moreover, the effect ofsence of a lipophilic anion salt such as NaTPB into the mem-composition prepared with high molecular weight PVC wassted.ently, Umezawa et al. demonstrated that anionic sitesing the sodium tetraphenylborate, NaTPB, employed in thet study) within the membrane phase can play an important

modulating receptor protonation and thus their interactionargeted anionic analytes. As such, they serve not only toe receptor protonation, they also help suppress unfavor-argecharge repulsions between the resulting protonated

or molecules and protons present at the interface. An excessed anionic sites (i.e., sodium tetraphenylborate) couldte with the protonated receptor and actually reverse theiometric response of a membrane such that it displays ac response rather than the expected anionic response. Bysing the concentration of anionic sites in the membrane

the anionic potentiometric response resulting from thedesired size and glued to one end of a Pyrex glass tubete. The assembly was lled with an internal solutionM K2HPO4). The electrode was nally conditioned forking in a 1.0 103 M K2HPO4 solution. Membranesproducible results as well as fast response time were

further studies. A silver/silver chloride electrode wasnternal reference electrode.

oning of membranes and EMF measurements

ared membranes were equilibrated for 2 days in dif-entrations of outer solution (1.0 1014.0 104 M)y side inner solution of different concentration range1.0 103 M) of K2HPO4 solution. The potentials werey varying the concentration of monohydrogenphos-t solution in the range of 1.0 1061.0 101 mol L1.d monohydrogenphosphate solutions were obtained by

dilution of 0.1 M monohydrogenphosphate stock solu-est results were obtained when the concentration ofolyte was 103 M.MF measurements were carried out with the following

internal solution (1.0 103 mol L1 K2HPO4)/PVCsample solution/Hg/Hg2Cl2, KCl (satd.). A Meterlab

95 pH/ION Meter was used for potential measurements.ivities of monohydrogenphosphate were calculatedo the DebyeHuckel procedure, using the following4]:

511z2[

1/2

1 + 1.51/2 0.2]

the ionic strength and z the valency.

and discussion

e revealed that in the present Hofmeister selectiv- monohydrogenphosphate stands towards the end ofwhich has necessitated the development of mono-osphate selective polymeric membranes that exhibitister selectivity patterns. Among several possible

to invert the Hofmeister behavior, the most commonf ionnophores suitable to form strong complexes with

anions. Among these ionophores relevant examples metal-anion and hydrogen bonding or electrostatic

have been reported [35,4550]. In the preliminarys, the ionophore was used as a potential ion carrier inction of ion-selective sensors for some common anions.ial responses of these electrodes are shown in Fig. 1,ne sensor displayed outstanding selectivity for HPO42

her anions. Such anti-Hofmeister selectivity is believedesult of a specic interaction between the ionophore

ions. On the contrary, to check the interaction of the with the ionophore, membrane has been tested with

acid and two different phosphate salts like diammo-genphosphate and disodium hydrogenphosphate butnt changes were found in the slope as well as in the lin-ence we can conclude that positive ions like NH4+ ort responding to the electrode in analysis; the electrode

HPO42 ions.

3.1. UV

In tixarenwith Uto distA bathof inte(HPO4chloridwere inwere ntenden

3.2. Ef

It istivity obut alserties the prebrane also te

Rec(includpresenrole inwith tenhancable chreceptof addcompepotentcationidecreaphase,ig. 1. Potential response of different anions on sensor.

Fig. 2. UVvis spectra of ionophore.

study

eliminary experiments, the phenylurea substituted cal-as tested for its selectivity towards different anions

spectral analysis, as illustrated in Fig. 2. It was likelyish the interactions between the ionophore and MHP.omic shift of 32 nm in the spectra gave the evidenceion between the ionophore with the analyte aniont the same time, the effects of other anions such as

omide, sulfate, perclorate on the spectrum of the carrierigated and no detectable changes in the UV/vis spectra. These results revealed that the ionophore has especial

124 N.R. Modi et al. / Talanta 86 (2011) 121 127

Table 2Performance of MHP selective electrode in partially non aqueous medium.

Non aqueous content% (v/v)

Working concentrationrange (M)

Slope(mV decade1)

0

Ethanol10 20 25 30

Methanol1020 25 30

Acetone102025 30

receptor prwhat is seeexpected toferents in abonds that

The natusitivity andlipophilicitycapacity tothe polymedue to theirIn additionthey are soity and woraffected by is due to thethe membrthe state oftion, naturethe potentimembranesmized membest responfollowing inresulted in very wide c

3.3. Effect o

The perfther assesseethanolwaare compilecontent, notion range omedium thecan only becontent.

3.4. ISE resp

In aque(H3PO4 Hdepends onthe pH of t

ig. 3.

ffect o

is mh forf thctrod[26,3

potde wis pere introduced to the cell, and the corresponding poten-ere determined. The potential readings were plotted

t log of the MHP concentration. Over the concentra-ange 1.0 1091.0 101 M of MHP in the calibrationn, the electrode potential response was linear with thetration of MHP (Fig. 3). The calibration curve slope was

0.3 mV decade1 and the detection limit, calculated as rec-nded by the IUPAC, was 2.0 108 M [18]. The inuence ofcentration of the internal solution on the potential responseonohydrogenphosphate electrode was studied in the range6.0 1081.0 101 29.40 0.4

6.0 1081.0 101 29.40 0.36.0 1081.0 101 29.25 0.44.2 1081.0 101 28.45 0.32.5 1071.0 102 25.81 0.2

6.0 1081.0 101 29.40 0.46.0 1081.0 101 29.15 0.25.0 1081.0 101 27.89 0.31.5 1071.0 101 26.60 0.3

6.0 1081.0 101 29.30 0.46.0 1081.0 101 29.10 0.24.5 1081.0 101 28.25 0.41.0 1071.0 102 25.20 0.3

otonation is expected to become stronger. In contrast ton with anionic sites, the presence of cationic sites was

enhance the discrimination between anionic inter-ccord with the number of receptoranalyte hydrogencould be stabilized.re of plasticizer has been found to improve the sen-

stability of sensors due to characteristics such as, high molecular weight, low vapor pressure and high

dissolve the substrate and other additives present inric membrane. PVC membranes are the ideal material

low electrical resistance and easiness of construction., with the membrane supported by a tough material,lid and not breakable. It is well known that selectiv-king concentration range of the membrane sensors arethe nature and the amount of the plasticizer used. This

inuence of the plasticizer on the dielectric constant ofane phase, the mobility of the ionophore molecules and

ligands. Thus, the inuence of the membrane composi-, and amount of plasticizer, and lipophilic additives onal response of the membrane was investigated. Several

were prepared with different compositions. The opti-brane compositions are summarized in Table 1. These was observed with the membrane composed of thegredients: 30% PVC, 60% NPOE, 6% ionophore, 4% NaTPBa Nernstian behavior of the membrane electrode over aoncentration range.

f non-aqueous solvent

F

Fig. 4. E

HPO42

pH botslope othe eleanion

TheelectroFor thMHP wtials wagainstion rsolutioconcen29.4 ommethe conof the mormance of the proposed membrane sensor was fur-d in partial non-aqueous media, i.e., methanolwater,ter and acetonewater mixture. The results obtainedd in Table 2 and indicate that up to 25% of non-aqueous

signicant change in the slope and working concentra-f the sensor is observed. At more than 30% non-aqueous

working range is signicantly reduced, thus the sensor utilized in mixtures containing up to 30% non-aqueous

onse to phosphate

ous solution phosphates exist in various forms2PO4 HPO42 PO43), the prevalence of which

the medium, which can be distinguished by varyinghe solution. H2PO4 prevails in acidic conditions and

1.0 101concentraticant differefor an expeplots. A 1.0suitable for

A slope tion curve monohydrovalue. To inwas responRiggan [16the functiodo this, thephosphate from the pHphosphate)Calibration curve of MHP ion-selective membrane electrode.

f pH on the potential response of the MHP ion selective electrode.

ore predominant under basic conditions; at a neutralms are present. Therefore, under neutral conditions thee ISE response curve can be used to indicate whethere is responding to the mono or dihydrogen phosphate5].entiometric response of the prepared ion selectiveas investigated against the MHP ion concentration.

urpose, appropriate aliquots of a stock solution of1.0 104 M of HPO42. The results showed that theon of the internal solution does not cause any signi-nce in the potential response of the electrodes, exceptcted change in the intercept of the resulting Nernstian

103 M concentration of the internal solution is quite smooth functioning of the electrode system.of 29.4 0.3 mV decade1 obtained from the calibra-(Fig. 3) proposed that calixarene ISE respond to thegen phosphate (HPO42) species with a Nernstian slopevestigate which phosphate species the ISE membraneding, we adopted the procedure proposed by Carey and], a procedure mainly focused on the effect of pH onn of the electrode in phosphate solutions. In order to

solution pH was varied while maintaining the totalconcentration constant, at 4 103 M. As can be seen

study (Fig. 4), the sensor at pH 8.4 (monohydrogen- shows a Nernstian response. At other values lower than

N.R. Modi et al. / Talanta 86 (2011) 121 127 125

Fig. 5. Dynamic response time of the electrode for step changes in the concentrationof the HPO42 ion solution: (A) 1.0 106 M; (B) 1.0 105 M; (C) 1.0 104 M; (D)1.0 103 M; (E) 1.0 102 M; (F) 1.0 101 M.

8.4 pH, theinto considand the rescontaining

3.5. Respon

The resp95% steadysolutions, eaverage timpotential wsured. In thchanging wtions (1.0 sequence wmeasuremerequired nein Fig. 5 andrium resporeversibilitythe oppositsequence odisplayed treversible, aues was lonprocedure (

3.6. Life tim

The invebrane sensodaily use ovwas no devin Table 3. detection li

Table 3Lifetime behav

Week

1 2 5 7 9

11 1315 17

Table 4Selectivity coefcients of various interfering ions.

Interfering ions log KMPMHPO4

2,BInterfering ions log KMPM

HPO42,B

F

Cl

Br

I

SCN

Citrate

3.7. Sensor

The seleacteristics oin the term potential m

metheratu]. In tted u02 Mtion.easuand n ion

obtamaryplot tenti

aAaB

peci ion ionnterto antche

nseq. Th

s of t. Thice o

the the doefelect

nion

xarelic hy response of the sensor is not linear. Therefore, takingeration of both the factors, a Nernstian response slopeponse to pH, it can be concluded that these electrodeionophore respond to the dibasic HPO42 anions.

se time of the electrode

onse time is the time required for the sensors to reach potentials after successive immersion in a series ofach having a 10-fold difference in concentration. Thee that was required for the HPO42 sensor to reach aithin 1 mV of the nal equilibrium value was mea-is study, the practical response time was recorded byith different monohydrogenphosphate ion concentra-

1061.0 101 M). In the rst case the measurementas from the lower to higher concentrations. After eachnt, the solution was rapidly changed. Such a changearly 8 s. The actual potential versus time curve is shown

it can be seen that the electrode reached the equilib-nse in a very short time of about 8 s. To evaluate the

of the electrode, a similar procedure was adopted ine direction. The measurements were performed in thef high-to-low sample concentrations and the resultshat the potentiometric response of the sensor waslthough the time needed to reach the equilibrium val-ger than that for the low-to-high sample concentration25 s).

e of the ion selective electrode

stigational result shows that the lifetime of MHP mem-r is 15 weeks. During this period, the electrode was iner an extended period of the time (1 h per day), thereiation in electrode features and the results are givenAfter 15 weeks, a gradual decrease in the slope and

ferent the lit[57,58evalua1.0 1mendawere mion, aBing of avaluesthe priof the the po

KpotA,B =

A sHPO42

HPO42

ment, iadded tial maThe coTable 4cientanionsformanamongions intivity cMHP s

3.8. Io

Caliphenomit was observed.

ior of MHP ion selective electrode.

Slope (mV decade1) Linear range (M)

29.4 0.3 6.0 1081.0 10129.4 0.2 6.0 1081.0 10129.4 0.3 6.0 1081.0 10129.4 0.4 5.0 1081.0 10129.4 0.2 5.0 1081.0 10129.2 0.4 4.0 1081.0 10129.2 0.4 3.0 1081.0 10129.0 0.2 1.0 1081.0 10127.5 0.3 3.0 1071.0 102

afnity to athe shape oand shape. consideringthe bindingthe target amolecule thof these grospherical geand therefobonding (Fet al. [59] aalised calix3.65 SO42 2.92.8 H2PO4 3.53.5 CO32 2.861.2 Oxalate 1.54.25 NO3 4.13.1 ClO4 3.7

selectivity

ctivity behavior is apparently one of the most vital char-f an ion-selective electrode, which is usually expressedof selectivity coefcient, which is evaluated using matchethod (MPM) recommended by IUPAC [5456]. Dif-ods of selectivity determination have been found inre, after the narrative work done by Umezawa et al.he present study, the selectivity coefcients have beensing modied form of xed interference method at

concentration of interfering ions as per IUPAC recom- In this method, the electromotive force (EMF) valuesred for solutions of constant activity of the interfering

varying activity of the primary ion, aA in a cell compris--selective electrode and a reference electrode. The EMFined were plotted versus the logarithm of the activity of

ion. The intersection of the extrapolated linear portionsindicates the value of aA that is to be used to calculateal from the following equation:

= aA aAaB

ed activity of the primary ions (A: 1.0 103 M ofs) is added to a reference solution (1.0 106 M ofs) and the potential is measured. In a separate experi-fering ions (B: 1.0 1051.0 101 M) are successively

identical reference solution, until the measured poten-s the one obtained before the primary ion addition.uential selectivity coefcient values are summarized ine data given in this table present the selectivity coef-he proposed MHP membrane sensor for all the testeds seems to indicate negligible interferences in the per-f the electrode assembly. As can be seen from Table 4,anions, iodide and oxalate were the major interferingetermination of HPO42 ions. For the other lower selec-cient values, it was considered that the function of theive membrane sensor would not be greatly disturbed.

ophore binding mode

nes can be chemically modied by substitution of thedrogens with various functionalities known for theirnions of interest. Anion recognition is associated withf anion, and anion requires a receptor with specic sizeCalixarene based anion receptors are important when

their binding interactions with anions. With regard to mode of the HPO42 anion to these calixarene molecule,nions coordinate to the urea moiety of the calixarene

rough hydrogen-bonding interactions to the protonsups, and perhaps favour anions with a tetrahedral orometry to some extent. HPO42 is tetrahedral in shapere is likely to bind with calixarene through hydrogenig. 6). This was supported by the ndings of Lhotaknd Evans et al. [60]. In the case of ferrocene function-[4]arene molecule [59] and ureido-thiacalix[4]arene

126 N.R. Modi et al. / Talanta 86 (2011) 121 127

Fig. 6. Ionionophore binding mode.

Fig. 7. Potent102 mol L1 B

[60] functiogen bondinthe interactfullerobisp

3.9. Analyti

The monunder labotrode in the(1.0 104results is shstoichiomeof barium ioaccuracy.

To evalusamples, an

Table 5Determination of MHP in various fertilizer samples using proposed sensor.

Sample no. Sample name ISE (%) Colorimetric (%)

1NPK

10.42 0.15 10.18 0.062 10.15 0.22 10.04 0.153 10.85 0.18 10.80 0.101

TSP42.20 0.35 42.10 0.15

2 43.00 0.20 42.45 0.303 42.70 0.17 42.52 0.351

SSP18.50 0.40 18.30 0.35

2 18.72 0.65 18.50 0.093 18.35 0.30 18.10 0.20

Table 6Determination of MHP in various detergent samples using proposed sensor.

Detergent sample ISE (%) Colorimetry (%)

A 19.50 0.40 19.35 0.08B 12.95 0.25 12.45 0.20C 15. 21 0.30 15.80 0.40

nation

e

ater ria lakrial wG.I.D.C

ate rtilizate

f eachetric

Table 8Comparison o

Sr. no.

1 2

3

4

Proposed se

a N.R: not reiometric titration curve of 25.0 mL HPO42 (1.0 103 mol L1) witha2+ using the membrane as an indicator electrode in pH 9.

nality, the molecule binds to phosphate through hydro-g. The same was observed during our investigation onion of dihydrogen phosphate with crown ether basedyrrolidine [39].

Table 7Determi

Sampl

Tape wKankaIndustVatva

phosphsium fephosph0.1 g ovolumcal application

ohydrogenphosphate sensor was found to work wellratory conditions. It was used as an indicator elec-

successful titration of a 25 mL phosphate ion solutionM) with the Ba2+ ion (1.0 102 M), at pH 9.0, and theown in Fig. 7, the sharp break point corresponds to thetry of the MHPBa precipitate (BaHPO4). So, the amountn can be determined with the sensor within acceptable

ate the practical applicability of the sensor in real attempt was made to determine MHP in the three

and dilutedcarried outter. The phothe proposeobtained byTable 5. As both metho

The propdirect potetion in threpowder waask, and 1and the reswater. Befo

f proposed electrode with previous reported electrode.

Name of Sensor Working concentration range Detection limit

5.0 1051.0 101 1.0 105Vanadyl salophen(VNSP)

1.0 1061.0 101 5.0 107

Molybdenumbis(2-hydroxyanil)acetylacetonatecomplex (MAA)

1.0 1071.0 101 6.0 108

Vanadyl salencomplex (VS)

5.0 1061 101 3.0 106

nsor Phenyl ureasubstitutedcalix[4]arene

6.0 1081.0 101 2.0 108

ported. of MHP in spiked water samples using proposed sensor.

Added(g L1)

Found byproposed sensor(g L1)

Found bycolorimetric(g L1)

20.00 20.35 19.86e water 75.00 74.80 74.75aste water 50.00 51.15 50.92. waste water 120.00 121.36 121.43

fertilizer samples, like mixed nitrogen phosphate potas-er (NPK), triple super phosphate (TSP), and single super

(SSP), and the results are given in Table 5. An amount of fertilizer was taken and dissolved in water in a 100 mL

ask, and 10.0 mL of 0.01 M EDTA (pH of 10.0) was added to the mark with Milli-Q water. Before the analysis was

all the samples have been ltered through 0.45 m l-

sphate content of the nal solution was determined byd sensor using the calibration curve method. The results

the MHP sensor and colorimetric method are given incan be seen, there is a satisfactory agreement betweends.osed membrane sensor was also applied for the fast and

ntiometric determination of phosphate ion concentra-e different kinds of detergents. 0.1 g of each detergents dissolved in distilled water in a 100 mL volumetric0.0 mL of 0.1 M EDTA (pH of 10.0) was added to the askulted solution was diluted to the mark with distilledre the analysis was carried out all the samples were

Slope Life time (Days) Response time Reference

28.0 N.Ra N.Ra [22]30.1 0.6 98

N.R. Modi et al. / Talanta 86 (2011) 121 127 127

ltered through 0.45 m lter. The monohydrogen phosphate con-centration of the nal solutions, were determined by the proposedsensor, using the calibration method. The results that obtained bythe sensor and spectrophotometric methods are given in Table 6.As seen, there is a satisfactory agreement between both methods.

The present membrane sensor was successfully used in thepotentiometric determination of MHP in spiked water samples.The water samples which have been collected from the differentareas of Ahmedabad city like vatva G.I.D.C., Naroda industrial estateand Kankaria Lake were prepared by the addition of 120, 50 and75 g L1 MHP in a 100 mL volumetric ask. To this solution 10.0 mLof 0.1 M EDTA (pH of 10.0) was added to the ask and diluted to themark with distilled water. Before the analysis was carried out all thesamples weeach samplsor, using thpotentiomecan be seenods. Thus, tMHP selectdetection licoefcients

4. Conclus

In summdevelop iondrogenphosresponded ion. The elelimit, respoously reporThe electrodto determinions and als(industrial w

Acknowled

Financiafor spectral

References

[1] S.E. Matth[2] E. Bakker[3] P. Buhlma[4] H. Tsukub[5] V.K. Gupt[6] A.K. Jain, V[7] V.K. Gupt

153158.[8] D. Diamo

(1988) 22[9] K.M. OCo

[10] K. Cunnin341344.

[11] D. Diamo[12] R. Ludwig[13] M.M.G. A

[14] A. Blazejczyk, M. Szczwpak, W. Wieczovek, P. Cmoch, G.B. Appetecchi, B.Scrosati, R. Kovarsky, D. Golodnitsky, E. Peled, Chem. Mater. 17 (2005)15351547.

[15] M. Staflani, K.S.B. Hancock, J.W. Steed, K.T. Holman, J.L. Atwood, R.K. Juneja,R.S. Burkhalter, J. Am. Chem. Soc. 119 (1997) 63246335.

[16] K.C. Nam, D.S. Kim, Y.S. Yang, Bull. Korean Chem. Soc. 19 (1998) 11331137.[17] K. Robards, I.D. McKelvie, R.L. Benson, P.J. Worsfold, N.J. Blundell, H. Casey, Anal.

Chim. Acta 287 (1994) 147190.[18] P. Worsfold, E. Achterberg, A. Bowie, P. Gardolinsk, M. Gledhill, G. Hanrahan, I.

McKelvie, S. Ussher, Chiang Mai J. Sci. 30 (2003) 153164.[19] P.L. Buldini, J. Sharma, D. Ferri, J. Chromatogr. A 654 (1) (1993) 129134.[20] O. Minareci, M. ztrk, . Egemen, E. Minareci, Afr. J. Biotechnol. 8 (15) (2009)

35683575.[21] Y. Kumar, M.S.A. Galil, M.S. Suresha, M.A. Sathish, G. Nagendrappa, E-J. Chem.

4 (4) (2007) 467473.[22] F. Kivlehan, W.J. Mace, H.A. Moynihan, D.W.M. Arrigan, Anal. Chim. Acta 585

(2007) 154160.. Gan. Gan201. Gan

anbak. Glazi. Glaziiu, W214. Nishi44.ishiza

128 (.G. A

uatorsWrob. Rein. Care. Care. GuptFibbio160atel, A108atel, A247umarumar

ct. 18 . Menoutsch

Collinris, J. amata. Jain,721. Jain, . Gupt. Gupt. Singh. Guptesch,mmaa 171 osatz208. Zam155. Zam. Zam07) 85ezawts, CRmezahotak

Evan446re ltered through 0.45 m lter. The concentration ofe was measured by the monohydrogenphosphate sen-e calibration method. The results obtained by the directtry and spectrophotometry are depicted in Table 7. As, there is a good correlation between the both meth-he proposed sensor is better than previously reportedive membrane sensor (Table 8), not only in the terms ofmit and dynamic range but also in terms of selectivity.

ion

ary, a simple construction procedure was used to selective electrodes for the detection of monohy-phate (MHP) ions at low concentration. The electrodeto monohydrogenphosphate ion in a Nernstian fash-ctrode characteristics such as pH range, lower detectionnse time and selectivity were comparable to the previ-ted monohydrogenphosphate ion-selective electrodes.e can be successfully applied as the indicator electrodee the end point in the potentiometric titration of Ba2+

o for the estimation of MHP ions in real environmentalaste, tap and lake water) samples.

gements

l assistance from UGC, New Delhi and CDRI, Lucknow analysis is gratefully acknowledged.

ews, P.D. Beer, Supramol. Chem. 17 (6) (2005) 411435., P. Buhlmann, E. Pretsch, Chem. Rev. 97 (1997) 30833132.nn, E. Pretsch, E. Bakker, Chem. Rev. 98 (1998) 15931688.e, K. Yamashita, T. Iwachiso, M. Zenki, J. Org. Chem. 56 (1991) 268.a, R. Prasad, P. Kumar, R. Mangla, Anal. Chim. Acta 420 (2000) 1927..K. Gupta, P. Kumar, R. Mangla, Electroanalysis 13 (2001) 10361040.

a, M. Al Khayat, A.K. Minocha, P. Kumar, Anal. Chim. Acta 532 (2005)

nd, G. Svehla, E.M. Seward, M.A. McKervey, Anal. Chim. Acta 2043231.nnor, D.W.M. Arrigan, G. Svehla, Electroanalysis 7 (1995) 205215.gham, G. Svelha, S.J. Harris, M.A. McKervey, Analyst 118 (1993)

nd, M.A. McKervey, Chem. Soc. Rev. 25 (1996) 1524., J. Fresenius, Fresenius J. Anal. Chem. 367 (2000) 103128.ntonisse, D.N. Reinhoudt, Chem. Commun. (1998) 443448.

[23] M.R[24] M.R

196[25] M.R

Jav[26] S.A[27] S.A[28] D. L

209[29] S.B

35[30] S. N

lyst[31] M.M

Act[32] W.

D.N[33] C.M[34] C.M[35] V.K[36] M.

156[37] B. P

101[38] B. P

239[39] A. K[40] A. K

tru[41] S.K[42] D. G[43] M.

Har[44] S. K[45] A.K

716[46] A.K[47] V.K[48] V.K[49] A.K[50] V.K[51] U. O[52] D. A

Act[53] T. R

197[54] H.A

149[55] H.A[56] H.A

(20[57] Um

cien[58] Y. U[59] P. L[60] A.J.

464jali, F. Mizani, M.S. Niasari, Anal. Chim. Acta 481 (2003) 8590.jali, P. Norouzi, M. Ghomi, M.S. Niasari, Anal. Chim. Acta 567 (2006).jali, F. Mizani, M. Emami, M.S. Niasari, M. Shamsipur, M. Youse, M.ht, Electroanalysis 15 (2) (2003) 139144.er, M.A. Arnold, Anal. Chem. 60 (1988) 25402542.er, M.A. Arnold, Anal. Chem. 63 (1991) 754759..-C. Chen, R.-H. Yang, G.-L. Shen, R.-Q. Yu, Anal. Chim. Acta 338 (1997).zawa, P. Buhlmann, K.P. Xiao, Y. Umezawa, Anal. Chim. Acta 358 (1998)

wa, T. Yokobori, R. Kato, K. Yoshimoto, T. Kamaishi, N. Teramae, Ana-2003) 663669.ntonisse, B.H.M. Snellink-Ruel, J.F.J. Engbersen, D.N. Reinhoudt, Sens.

B 47 (1998) 912.lewski, K. Wojciechowski, A. Dybko, Z. Brzozka, R.J.M. Snellink-Ruel,houdt, Anal. Chim. Acta 432 (2001) 7988.y, W.B. Riggan Jr., Anal. Chem. 66 (1994) 35873591.y, U.S. Patent 5,180,481, January 19, 1993.a, R. Ludwig, S. Agarwal, Anal. Chim. Acta 538 (2005) 213218.li, M. Berger, F.P. Schmidtchen, E. Pretsch, Anal. Chem. 72 (2000)

.. Kumar, S.K. Menon, J. Inclusion Phenom. Macrocycl. Chem. 64 (2009).. Kumar, S.K. Menon, J. Inclusion Phenom. Macrocycl. Chem. 64 (2009)., S.K. Menon, Supramol. Chem. 22 (2010) 4656., B. Patel, G. Patel, S.K. Menon, Fullerenes Nanotubes Carbon Nanos-(2010) 186197.n, N.R. Modi, B. Patel, M.B. Patel, Talanta 83 (2011) 13291334.e, M. Iqbal, D. Stewart, J. Org. Chem. 51 (1986) 742.s, M.A. McKervey, E. Madigan, M.B. Moran, M. Owens, G. Ferguson, S.J.Chem. Soc. Perkin Trans. 1 (1991) 3137., A. Bhale, Y. Fukunage, A. Murata, Anal. Chem. 60 (1988) 24642467.

V.K. Gupta, L.P. Singh, P. Srivastava, J.R. Raisoni, Talanta 65 (2005).V.K. Gupta, J.R. Raisoni, Electrochim. Acta 52 (2006) 951957.a, R.N. Goyal, R.A. Sharma, Talanta 76 (2008) 859864.a, R.N. Goyal, R.A. Sharma, Electrochim. Acta 54 (2009) 42164222., V.K. Gupta, B. Gupta, Anal. Chim. Acta 585 (2007) 171178.a, S. Agarwal, Talanta 65 (2005) 730734.

W. Simon, Anal. Chem. 52 (1980) 692700.nn, E. Pretsch, W. Simon, E. Lindner, A. Bezegh, E. Pungor, Anal. Chim.(1985) 119129.in, E. Bakker, W. Simon, K. Suzuki, Anal. Chim. Acta 280 (1993).ani, M.R. Ganjali, M.J. Pooyamanesh, J. Braz. Chem. Soc. 17 (2006).ania, G. Rajabzadeh, M.R. Ganjali, Sens. Actuators B 119 (2006) 4146.ani, M.R. Ganjali, P. Norouzi, S. Meghdadi, J. Appl. Electrochem. 373859.

aF Y. (Ed.), Handbook of Ion-Selective Electrodes: Selectivity Coef-C Press, Boca Raton, FL, 1990.wa, K. Umezawa, H. Sato, Pure Appl. Chem. 67 (1995) 508518., J. Svoboda, I. Stibor, Tetrahedron 62 (2006) 12531527.s, S.E. Matthews, A.R. Cowley, P.D. Beer, Dalton Trans. (2003)50.

Novel monohydrogenphosphate ion-selective polymeric membrane sensor based on phenyl urea substituted calix[4]arene1 Introduction2 Experimental2.1 Reagents and materials2.2 Synthesis of ionophore2.2.1 Synthesis of phenyl urea substituted calix[4]arene2.2.2 Synthesis of 5,11,17,23-tetra-tert-butyl-25,27-bis(phenyl urea)-26,28-dihydroxy calix[4]arene (6)

2.3 Electrode preparation2.4 Conditioning of membranes and EMF measurements

3 Results and discussion3.1 UVvis study3.2 Effect of the membrane composition3.3 Effect of non-aqueous solvent3.4 ISE response to phosphate3.5 Response time of the electrode3.6 Life time of the ion selective electrode3.7 Sensor selectivity3.8 Ionionophore binding mode3.9 Analytical application

4 ConclusionAcknowledgementsReferences