Accepted Manuscript Review article Membrane Sensors based on Schiff Bases as Chelating ionophores (A Review) Wail Al Zoubi, NaDeem Al Mohanna PII: DOI: Reference:
S1386-1425(14)00749-5 http://dx.doi.org/10.1016/j.saa.2014.04.176 SAA 12140
To appear in:
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy
Received Date: Revised Date: Accepted Date:
27 January 2014 24 April 2014 30 April 2014
Please cite this article as: W. Al Zoubi, N. Al Mohanna, Membrane Sensors based on Schiff Bases as Chelating ionophores (A Review), Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy (2014), doi: http:// dx.doi.org/10.1016/j.saa.2014.04.176
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Membrane Sensors based on Schiff Bases as Chelating ionophores (A Review) Wail Al Zoubi(*), NaDeem Al Mohanna Department of Chemistry, Faculty of Science, University of Damascus, Syria, Email: [email protected], [email protected]
Abstract The development of chemical sensors has received widespread attention during the past two decades because of their extensive use in environmental monitoring and clinical analysis via rapid, accurate, reproducible, and low-cost methods. Chemically modified CPEs have frequently been employed as potentiometric sensors in trace analysis for metal ions, organic pollutants and biological substances. Most of these electrodes are operated via the ion-exchange process of the active component incorporated into the carbon paste matrix. This review article concentrates on such achievements in the context of the general development across the field. An overview of potentiometric sensors that are capable of detecting metal ions in environmental samples is presented and discussed. A survey on important advances in potentiometric sensors with regard to high selectivity, lower detection limit, and fast response time is presented in this review article.
Keyword: Schiff base, Ion-selective electrodes, Sensors, Chemical Sensors.
Introduction Schiff bases, with a general formula ‘RCH=NR’ are compounds that are prepared by facile condensation between equivalent amounts of aldehyde and amine with high yields. Schiff base is known to be a sort of ligands with strong coordinative ability, and almost all SBs can form 1:1 complexes with transition metal ions. Some complexes of Schiff bases are used as liquid crystals. In organic synthesis, Schiff base reactions are useful in making carbon-nitrogen bonds. For several reasons, Schiff bases have been found to be among the most convenient and attractive ligands for quantification of several metal ions [1-3]. 1
In general, electrochemical methods are based on the transformation of chemical information into an analytical and electrochemically measurable signal. Any sensor used in such determinations contains two basic functional units; one receptor part, which transforms the chemical information into a form of energy and one transducer part which transforms the chemical information into a form of energy and one transducer part which transforms the energy, bearing chemical information, into a useful signal. A broad range of electrochemical techniques can be used for this purpose. Some of the most commonly used voltammetry, amperometry, impedometry, conductimetry and potentiometry, when the last named is based on the measurement of a potential under zero-current flow. The signal is measured as the potential difference between the indicator (electrode of the first kind, ion-selective electrode, metal-metal oxide electrode) and the reference electrode (e.g. SCE) with known and constant potential. The majority of ion-selective electrodes (ISEs) employ polymeric membranes as the material of choice for construction of the sensing proper. The direct rapid determination of minute quantities of ionic species by simple methods has a great importance in analytical chemistry. Construction and then application of ionselective electrodes (ISEs) as a potentiometric senor offers interesting advantages including simplicity, fast response, wide linear dynamic range, low detection limit, good selectivity. In view of the important of ion-selective electrode that based on the Schiff bases, we report review of recently works about synthesis of Schiff bases and their application in the ion-selective electrodes. Gupta et al have reported the preparation a polyvinyl chloride (PVC) based membrane sensor for cerium ions by employing N.N’-bis [2-(salicylideneamino) ethyl] ethane-1.2diamine (figure. 1) as an ionophore, oleic acid (OA) as anion excluder and onitrophenyloctyl ether (o-NPOE) as plasticizer. The sensor revealed a very good selectivity with respect to common alkali, alkaline earth and heavy metal ions. The response of the proposed sensor is independent of pH between 3.0 and 8.0. It was used as an indicator electrode in potentiometric titration of fluoride, carbonate and oxalate anions and determination of cerium in simulated mixtures [4].
2
NH
HN
N
N
CH
HC
OH
HO
Figure. 1. Structure of N.N’-bis [2-(salicylideneamino) ethyl] ethane-1.2-diamine Highly selective poly (vinyl chloride) (PVC) membrane electrode based on N-salicylidene-benzy-lamineato copper (II) complexes [Cu (SBA) 2] (figure 2) as new carriers towards thiocyanate-selective electrode was reported. The proposed electrode has a fast response time of about 5–10 s and can be used for at least 3 months without any considerable divergence in potential. The electrode was successfully applied to the determination of thiocyanate in waste water and human urine and saliva samples [5]. H C
CH2N
O
HC
M
O
NH2C
Figure 2. Structure of ionophore M (SBA)2 (M= Cu(II), Zn(II), Cd(II)) Nazife and coworkers have reported new iodide-, thiocyanate- and perchlorateselective liquid membrane electrodes based on the tris(2.2’.2’’-salicylidene-imino) triethylamine-iron (III) complexes (figure. 3). The effects of the pH and liquid membrane composition were also investigated. The proposed electrodes have a fast response time and nearly micro molar detection. The lifetimes of the electrodes are at least one month.
3
The potentiometric selectivity coefficients for some monovalent ion were evaluated by the mixed interference method [6]. N
H C
N Fe
N
O CH
N HC
O O
Figure. 3. Structure of tris (2,2’,2’’-salisiliden-imino) triethyl amine iron (III) (TrensalFe(III))
Recently works have used various ionophores in construction of PVC-based membrane sensors based on Schiff base for different trivalent cations, such as Cr(III), La(III), Gd(III), Yb(III), Ce(III), Sm(III), Tb(III), Dy(III), Tm(III), Eu(III), Pr(III) and Y(III). Also novel potentiometric membrane Eu(II) ion sensor is described based on a new
S-N
hexadentates
Schiff’s
base,
bis(thiophenol)butane-2,3-
dihydrazone(SNSB)(figure 4). The best performance was achieved with a membrane composition of 30% PVC, 63% o-nitrophenyloctyl ether (NPOE), 5% SNSB, and 5% (0.010 mmol) potassium tetrakis(p-chlorophenyl) borate (KTpClPB). It was found that in the pH range of 3.0-8.5, the potential response of the sensor was not affected by the pH. Furthermore, the electrode presented satisfactory reproducibility, very fast response time (< 5 s), and relatively good discriminating ability for Eu(III) ions with respect to many common cations and lanthanide ions, including sodium, potassium, magnesium, calcium, copper, nickel, cobalt, zinc, lead, lanthanum, cerium, gadolinium, samarium, ytterbium, presidium, terbium, neodymium, iron and chromium metal ions. The sensor was applied
4
to the determination of fluoride ions in two mouth wash preparations and binary mixtures [7-14]. H3 C
N
CH3
N
N
N
H
H S
S
Figure 4. Structure of bis (thiophenol) butane-2,3-dihydrazone Skuner et al have reported the preparation sensing membrane by immobilization of a novel
fluorescent
Schiff
base
ligand
4-(1-phenyl-1-methylcyclobutane-3-yl)-2-(2-
hydroxy-5-romobenzylidene) aminothiazole (figure 5), on polyvinyl chloride. The optode membrane formulations contained 120 mg of PVC, 240 mg of plasticizer (DOP), 1.12 mg of PCT dye (w2.5 mmol dye kg-1 polymer), 1.30 mg of potassium tetrakis(4chlorophenyl) borate and 1.5 mL of THF. The accuracy of the proposed sensor was confirmed by analyzing standard reference materials of natural water and peach leaves. The sensor was successfully applied for the determination of copper in tap and tea samples [15].
H3C
N N
CH
Br
S HO
Figure 5. Chemical structure of 4-(1-phenyl-1-methylcyclobutane-3-yl)-2-(2-hydroxy-5bromobenzylidene) aminothiazole (PCT) dye
5
Mashhadizadeh and coworkers were prepared a new PVC membrane electrode that is highly selective to Ni (II) ions by using N.N’-bis-(4-dimethylamino-benzylidene)benzene-1.2-diamine (figure 6) as a suitable neutral carrier. It has a response time of < 10s and can be used for at least 2 months without any measurable divergence in potential. The electrode can be used in the pH range from 4.5 to 9.0. The proposed sensor shows fairly a good discriminating ability towards Ni (II) ion in comparison to some hard and soft metals. The electrode was used in the direct determination of Ni (II) in aqueous solution and as an indicator electrode in potentiometric titration of nickel ions [16].
H
H N
N
N
N
Figure 6. Structure of N.N’-bis-(4-dimethylamino-benzylidene)-benzene-1.2-diamine (NDBBD) Vinod et al have reported the fabrication a new PVC membrane electrode for Co (II) based
on
N.N’-bis
(salicylidene)-3.4-diaminotoulene
(figure.
7)
using
sodium
tetraphenylborate(NaTPB) as an anionic excluder and dioctylphthalte (DOP) as a solvent mediator. This electrode was successfully applied for the determination of Co (II) in real samples and an indicator electrode in potentiometric titration of Co (II) [17].
6
N
N
OH
HO
Figure 7. Structure of N.N’-bis (salicylidene)-3.4-diaminotoluene Singh and coworkers have been synthesized and explored two chromium chelates of Schiff bases, N-(acetoacetanilide)-1.2-daiminoethane(L1) and N.N’-bis(acetoacetanilide)triethyl enetetraammine(L2)(figure 8), as neutral ionophores for preparing poly (vinylchloride) (PVC) based membrane sensors selective to Cr(III). The best performance was obtained for the membrane sensor having a composition of L1:PVC:DBP:NaTPB in the ratio 5:150:250:3 (w/w). The proposed sensor manifest advantages of relatively fast response (10 s) and good selectivity over some alkali, alkaline earth, transition and heavy metal ions. The selectivity behavior of the proposed electrode revealed a considerable improvement as compared to the best previously PVC-membrane electrode for chromium (III) ion. The potentiometric response of the proposed sensor was independent of pH of the test solution in the range of 2.0–7.0. The sensor has found to work satisfactorily in partially non-aqueous media up to 20% (v/v) content of methanol, ethanol and acetonitrile and could be used for a period of 3 months( The main factor responsible for the limited lifetime of a sensor is to be the loss of one or more of its components while contacting with aqueous solutions). The proposed electrode was used as an indicator electrode in potentiometric titration of chromium ion with EDTA and in direct determination in different water and food samples [18].
7
H N N
HN
O
NH N
NH2
N H
N H
O
N
O (L2)
(L1)
Figure 8. Structures of N-(acetoacetanilide)-1.2-diaminothane (L1) and N.N’-bis (acetoacet anilide)-triethyl enetetraammine (L2) A terbium–selective solvent polymeric membrane sensor based on N.N’-bis (pyrrolidene) benzene-1.2-diamine (PBD) (figure 9), poly (vinyl chloride) (PVC), benzylacetate (BA) plasticizer, and an anionic additive is described. It has a fast response time of < 20 s in the whole concentration range, and can be used for at least 2 months without any considerable divergences in the potentials. The proposed sensor revealed comparatively good selectivity with respect to common alkali, alkaline earth, transition and heavy metal ions. It was used as an indicator electrode in potentiometric titration of fluoride ions, and in determination of F− ion in some mouth washing solutions preparations [19]. Also in previously works have reported a number of sensors based Schiff bases for ions of the lanthanide group elements, such as Ce(III) [19,20], Yb(III) [21], La(III) [22,23], Sm(III) [24,25],Gd(III) [26].
H
H N
N
N
N
Figure 9. Structure of the N.N’-bis (pyrrolidene) benzene-1.2-diamine PBD 8
Mohammad and coworkers are described a new modified carbon paste electrode (CPE) and a coated wire PVC membrane (CWE) based on a recently synthesized Schiff base(figure 10) of [bis 5-(4-nitrophenyl azo) salisylaldimine] 1.8-diamine ,3.6-dioxo octan(BNSAO)(figure 10) as a suitable carrier for Ag(I) ion. Their electrodes have a fast response time (~5 s), a satisfactory reproducibility and relatively long life time. The proposed sensors show a fairly good selectivity toward Ag (I) ion in comparison to other common cations. The potentiometric responses are independent of the pH of the test solution in the pH range 3.5–7.0 for CPE and 2.5–7.0 for CWE. The proposed electrodes were used as indicator electrodes in potentiometric titration of silver ion with standard solution of potassium iodide. The direct determination of silver in spiked wastewater and radiology film gave results that compare favorably with those obtained by the atomic absorption spectrometric method [27].
H
N
O
O
H HO
OH
N
N
N
N
NO2
NO2
Figure 10. Structure of [bis 5-(4-nitrophenyl azo) salisylaldimine] 1.8-diamine Gupta and coworkers have reported the synthesis and exploration the six Schiff bases (figure 11) lariat ether chelates based on 4.13-diaza-18-crown ether as a neutral ionphores for poly (vinyl chloride) based membrane sensors selective to silver (I). The best 9
performance was obtained with membrane composition (w/w) chelate (2.8%):PVC (45.7%):o-NPOE (48.6%):KTpClPB (2.8%). The sensor was also found to work satisfactorily in partially non-aqueous media up to 25% (V/V) content of acetonitrile, methanol, or ethanol. The response of the sensor was highly selective to Ag (I) over a large number of cations and it could therefore be used for Ag (I) estimation in blood of occupationally exposed persons [28]. R
O O
N
N
O O
R
Figure 11. Structure of [N.N’-bis-(p-methylbenzaldehyde)-4.13-diaza-18-crown-6] A new PVC membrane electrode for manganese (II) ion based on a recently synthesized Schiff base of 5-[(4-nitrophenylazo)-N-hexylamine] salicylaldimine (figure. 12) is reported. The electrode has a fast response time (~10 s), a satisfactory reproducibility and relatively long life time. The proposed sensor revealed good selectivities over a wide variety of other cations include hard and soft metals. This electrode could be used in a pH range of 4.5-7.5. It was used as an indicator electrode in potentiometric titration of manganese (II) ions with EDTA solution [29]. HC
O2N
N2
N
(CH2)5 CH3
OH
Figure 12. Structure of 5-[(4-nitrophenylazo)-N-hexylamine] salicylaldimine 10
Reza Ganjali et al have reported in previously work the presentation a novel gadolinium membrane
sensor
based
on
new
S-N
sulfanylphenyl)imino)-1-methylbutylidene}amino]phenyl
Schiff’s hydrosulfide
base
(2-[{3-[(2-
(figure
13)
(SMPH). The best performance was obtained with a membrane composition of 33% poly (vinyl chloride), 61% benzyl acetate, 2% sodium tetraphenyl borate and 5% SMPH. The potentiometric response of the sensor is independent of the pH of the solution in the pH range of 4.0–8.0. The sensor possesses the advantages of short conditioning time, very fast response time, and especially, very good selectivity towards a large number of cations, such as Sm(III), Ce(III), La(III), Cu(II), Pb(II) and Hg(II). The electrode can be used for at least 9 weeks without any considerable divergence in the potentials. The electrode was used as an indicator electrode in potentiometric titration of Gd (III) ions with EDTA, and recovery of Gd(III) from various binary mixtures. It was also applied to the determination of Gd (III) in a urine sample [30].
H3C
CH3 N
N
S
S
H
H
Figure 13. Structure S-N Shiff base (2-[{3-[(2-sulfanylphenyl) imino)-1methylbutylidene}amino]phenyl hydrosulfide (SMPH). V.K. et al were described the construction and performance characteristics of polymeric membrane electrodes based on two neutral ionophores, N.N’-[bis(pyridi-2yl)formylidene]butane-1.4-diamine
(S1)
and
N-(2-pyridinylmethylene)-1.2-benzene
diamine (S2) (figure. 14) for quantification of cadmium ions. The best performance was obtained with the electrode having a membrane composition (w/w) of (S1) (2.15%): PVC (32.2%):o-NPOE (64.5%):KTpClPB (1.07%). The sensor has been found to work satisfactorily in partially non-aqueous media up to 30% (v/v) content of methanol,
11
ethanol and acetonitrile and could be used for a period of 2 months. The analytical usefulness of the proposed electrode has been evaluated by its application in the determination of cadmium in real samples [31]. N
N
N
N
N
N
(S1)
NH2
(S2 )
Figure 14. N.N’-[bis(pyridi-2-yl)formylidene]butane-1.4-diamine (S1) and N-(2 pyridinylmethyl ene)-1.2-benzenediamine (S2) Reza Ganjali et al have reported the study of the tendency of N-(thein-2-ylethylidene) benzene-1.2-diamine (SNS) (figure 15), towards chromium and some other metals ions, theoretical calculations and conductance studies. It has a fast response time of
S1386-1425(14)00749-5 http://dx.doi.org/10.1016/j.saa.2014.04.176 SAA 12140
To appear in:
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy
Received Date: Revised Date: Accepted Date:
27 January 2014 24 April 2014 30 April 2014
Please cite this article as: W. Al Zoubi, N. Al Mohanna, Membrane Sensors based on Schiff Bases as Chelating ionophores (A Review), Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy (2014), doi: http:// dx.doi.org/10.1016/j.saa.2014.04.176
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Membrane Sensors based on Schiff Bases as Chelating ionophores (A Review) Wail Al Zoubi(*), NaDeem Al Mohanna Department of Chemistry, Faculty of Science, University of Damascus, Syria, Email: [email protected], [email protected]
Abstract The development of chemical sensors has received widespread attention during the past two decades because of their extensive use in environmental monitoring and clinical analysis via rapid, accurate, reproducible, and low-cost methods. Chemically modified CPEs have frequently been employed as potentiometric sensors in trace analysis for metal ions, organic pollutants and biological substances. Most of these electrodes are operated via the ion-exchange process of the active component incorporated into the carbon paste matrix. This review article concentrates on such achievements in the context of the general development across the field. An overview of potentiometric sensors that are capable of detecting metal ions in environmental samples is presented and discussed. A survey on important advances in potentiometric sensors with regard to high selectivity, lower detection limit, and fast response time is presented in this review article.
Keyword: Schiff base, Ion-selective electrodes, Sensors, Chemical Sensors.
Introduction Schiff bases, with a general formula ‘RCH=NR’ are compounds that are prepared by facile condensation between equivalent amounts of aldehyde and amine with high yields. Schiff base is known to be a sort of ligands with strong coordinative ability, and almost all SBs can form 1:1 complexes with transition metal ions. Some complexes of Schiff bases are used as liquid crystals. In organic synthesis, Schiff base reactions are useful in making carbon-nitrogen bonds. For several reasons, Schiff bases have been found to be among the most convenient and attractive ligands for quantification of several metal ions [1-3]. 1
In general, electrochemical methods are based on the transformation of chemical information into an analytical and electrochemically measurable signal. Any sensor used in such determinations contains two basic functional units; one receptor part, which transforms the chemical information into a form of energy and one transducer part which transforms the chemical information into a form of energy and one transducer part which transforms the energy, bearing chemical information, into a useful signal. A broad range of electrochemical techniques can be used for this purpose. Some of the most commonly used voltammetry, amperometry, impedometry, conductimetry and potentiometry, when the last named is based on the measurement of a potential under zero-current flow. The signal is measured as the potential difference between the indicator (electrode of the first kind, ion-selective electrode, metal-metal oxide electrode) and the reference electrode (e.g. SCE) with known and constant potential. The majority of ion-selective electrodes (ISEs) employ polymeric membranes as the material of choice for construction of the sensing proper. The direct rapid determination of minute quantities of ionic species by simple methods has a great importance in analytical chemistry. Construction and then application of ionselective electrodes (ISEs) as a potentiometric senor offers interesting advantages including simplicity, fast response, wide linear dynamic range, low detection limit, good selectivity. In view of the important of ion-selective electrode that based on the Schiff bases, we report review of recently works about synthesis of Schiff bases and their application in the ion-selective electrodes. Gupta et al have reported the preparation a polyvinyl chloride (PVC) based membrane sensor for cerium ions by employing N.N’-bis [2-(salicylideneamino) ethyl] ethane-1.2diamine (figure. 1) as an ionophore, oleic acid (OA) as anion excluder and onitrophenyloctyl ether (o-NPOE) as plasticizer. The sensor revealed a very good selectivity with respect to common alkali, alkaline earth and heavy metal ions. The response of the proposed sensor is independent of pH between 3.0 and 8.0. It was used as an indicator electrode in potentiometric titration of fluoride, carbonate and oxalate anions and determination of cerium in simulated mixtures [4].
2
NH
HN
N
N
CH
HC
OH
HO
Figure. 1. Structure of N.N’-bis [2-(salicylideneamino) ethyl] ethane-1.2-diamine Highly selective poly (vinyl chloride) (PVC) membrane electrode based on N-salicylidene-benzy-lamineato copper (II) complexes [Cu (SBA) 2] (figure 2) as new carriers towards thiocyanate-selective electrode was reported. The proposed electrode has a fast response time of about 5–10 s and can be used for at least 3 months without any considerable divergence in potential. The electrode was successfully applied to the determination of thiocyanate in waste water and human urine and saliva samples [5]. H C
CH2N
O
HC
M
O
NH2C
Figure 2. Structure of ionophore M (SBA)2 (M= Cu(II), Zn(II), Cd(II)) Nazife and coworkers have reported new iodide-, thiocyanate- and perchlorateselective liquid membrane electrodes based on the tris(2.2’.2’’-salicylidene-imino) triethylamine-iron (III) complexes (figure. 3). The effects of the pH and liquid membrane composition were also investigated. The proposed electrodes have a fast response time and nearly micro molar detection. The lifetimes of the electrodes are at least one month.
3
The potentiometric selectivity coefficients for some monovalent ion were evaluated by the mixed interference method [6]. N
H C
N Fe
N
O CH
N HC
O O
Figure. 3. Structure of tris (2,2’,2’’-salisiliden-imino) triethyl amine iron (III) (TrensalFe(III))
Recently works have used various ionophores in construction of PVC-based membrane sensors based on Schiff base for different trivalent cations, such as Cr(III), La(III), Gd(III), Yb(III), Ce(III), Sm(III), Tb(III), Dy(III), Tm(III), Eu(III), Pr(III) and Y(III). Also novel potentiometric membrane Eu(II) ion sensor is described based on a new
S-N
hexadentates
Schiff’s
base,
bis(thiophenol)butane-2,3-
dihydrazone(SNSB)(figure 4). The best performance was achieved with a membrane composition of 30% PVC, 63% o-nitrophenyloctyl ether (NPOE), 5% SNSB, and 5% (0.010 mmol) potassium tetrakis(p-chlorophenyl) borate (KTpClPB). It was found that in the pH range of 3.0-8.5, the potential response of the sensor was not affected by the pH. Furthermore, the electrode presented satisfactory reproducibility, very fast response time (< 5 s), and relatively good discriminating ability for Eu(III) ions with respect to many common cations and lanthanide ions, including sodium, potassium, magnesium, calcium, copper, nickel, cobalt, zinc, lead, lanthanum, cerium, gadolinium, samarium, ytterbium, presidium, terbium, neodymium, iron and chromium metal ions. The sensor was applied
4
to the determination of fluoride ions in two mouth wash preparations and binary mixtures [7-14]. H3 C
N
CH3
N
N
N
H
H S
S
Figure 4. Structure of bis (thiophenol) butane-2,3-dihydrazone Skuner et al have reported the preparation sensing membrane by immobilization of a novel
fluorescent
Schiff
base
ligand
4-(1-phenyl-1-methylcyclobutane-3-yl)-2-(2-
hydroxy-5-romobenzylidene) aminothiazole (figure 5), on polyvinyl chloride. The optode membrane formulations contained 120 mg of PVC, 240 mg of plasticizer (DOP), 1.12 mg of PCT dye (w2.5 mmol dye kg-1 polymer), 1.30 mg of potassium tetrakis(4chlorophenyl) borate and 1.5 mL of THF. The accuracy of the proposed sensor was confirmed by analyzing standard reference materials of natural water and peach leaves. The sensor was successfully applied for the determination of copper in tap and tea samples [15].
H3C
N N
CH
Br
S HO
Figure 5. Chemical structure of 4-(1-phenyl-1-methylcyclobutane-3-yl)-2-(2-hydroxy-5bromobenzylidene) aminothiazole (PCT) dye
5
Mashhadizadeh and coworkers were prepared a new PVC membrane electrode that is highly selective to Ni (II) ions by using N.N’-bis-(4-dimethylamino-benzylidene)benzene-1.2-diamine (figure 6) as a suitable neutral carrier. It has a response time of < 10s and can be used for at least 2 months without any measurable divergence in potential. The electrode can be used in the pH range from 4.5 to 9.0. The proposed sensor shows fairly a good discriminating ability towards Ni (II) ion in comparison to some hard and soft metals. The electrode was used in the direct determination of Ni (II) in aqueous solution and as an indicator electrode in potentiometric titration of nickel ions [16].
H
H N
N
N
N
Figure 6. Structure of N.N’-bis-(4-dimethylamino-benzylidene)-benzene-1.2-diamine (NDBBD) Vinod et al have reported the fabrication a new PVC membrane electrode for Co (II) based
on
N.N’-bis
(salicylidene)-3.4-diaminotoulene
(figure.
7)
using
sodium
tetraphenylborate(NaTPB) as an anionic excluder and dioctylphthalte (DOP) as a solvent mediator. This electrode was successfully applied for the determination of Co (II) in real samples and an indicator electrode in potentiometric titration of Co (II) [17].
6
N
N
OH
HO
Figure 7. Structure of N.N’-bis (salicylidene)-3.4-diaminotoluene Singh and coworkers have been synthesized and explored two chromium chelates of Schiff bases, N-(acetoacetanilide)-1.2-daiminoethane(L1) and N.N’-bis(acetoacetanilide)triethyl enetetraammine(L2)(figure 8), as neutral ionophores for preparing poly (vinylchloride) (PVC) based membrane sensors selective to Cr(III). The best performance was obtained for the membrane sensor having a composition of L1:PVC:DBP:NaTPB in the ratio 5:150:250:3 (w/w). The proposed sensor manifest advantages of relatively fast response (10 s) and good selectivity over some alkali, alkaline earth, transition and heavy metal ions. The selectivity behavior of the proposed electrode revealed a considerable improvement as compared to the best previously PVC-membrane electrode for chromium (III) ion. The potentiometric response of the proposed sensor was independent of pH of the test solution in the range of 2.0–7.0. The sensor has found to work satisfactorily in partially non-aqueous media up to 20% (v/v) content of methanol, ethanol and acetonitrile and could be used for a period of 3 months( The main factor responsible for the limited lifetime of a sensor is to be the loss of one or more of its components while contacting with aqueous solutions). The proposed electrode was used as an indicator electrode in potentiometric titration of chromium ion with EDTA and in direct determination in different water and food samples [18].
7
H N N
HN
O
NH N
NH2
N H
N H
O
N
O (L2)
(L1)
Figure 8. Structures of N-(acetoacetanilide)-1.2-diaminothane (L1) and N.N’-bis (acetoacet anilide)-triethyl enetetraammine (L2) A terbium–selective solvent polymeric membrane sensor based on N.N’-bis (pyrrolidene) benzene-1.2-diamine (PBD) (figure 9), poly (vinyl chloride) (PVC), benzylacetate (BA) plasticizer, and an anionic additive is described. It has a fast response time of < 20 s in the whole concentration range, and can be used for at least 2 months without any considerable divergences in the potentials. The proposed sensor revealed comparatively good selectivity with respect to common alkali, alkaline earth, transition and heavy metal ions. It was used as an indicator electrode in potentiometric titration of fluoride ions, and in determination of F− ion in some mouth washing solutions preparations [19]. Also in previously works have reported a number of sensors based Schiff bases for ions of the lanthanide group elements, such as Ce(III) [19,20], Yb(III) [21], La(III) [22,23], Sm(III) [24,25],Gd(III) [26].
H
H N
N
N
N
Figure 9. Structure of the N.N’-bis (pyrrolidene) benzene-1.2-diamine PBD 8
Mohammad and coworkers are described a new modified carbon paste electrode (CPE) and a coated wire PVC membrane (CWE) based on a recently synthesized Schiff base(figure 10) of [bis 5-(4-nitrophenyl azo) salisylaldimine] 1.8-diamine ,3.6-dioxo octan(BNSAO)(figure 10) as a suitable carrier for Ag(I) ion. Their electrodes have a fast response time (~5 s), a satisfactory reproducibility and relatively long life time. The proposed sensors show a fairly good selectivity toward Ag (I) ion in comparison to other common cations. The potentiometric responses are independent of the pH of the test solution in the pH range 3.5–7.0 for CPE and 2.5–7.0 for CWE. The proposed electrodes were used as indicator electrodes in potentiometric titration of silver ion with standard solution of potassium iodide. The direct determination of silver in spiked wastewater and radiology film gave results that compare favorably with those obtained by the atomic absorption spectrometric method [27].
H
N
O
O
H HO
OH
N
N
N
N
NO2
NO2
Figure 10. Structure of [bis 5-(4-nitrophenyl azo) salisylaldimine] 1.8-diamine Gupta and coworkers have reported the synthesis and exploration the six Schiff bases (figure 11) lariat ether chelates based on 4.13-diaza-18-crown ether as a neutral ionphores for poly (vinyl chloride) based membrane sensors selective to silver (I). The best 9
performance was obtained with membrane composition (w/w) chelate (2.8%):PVC (45.7%):o-NPOE (48.6%):KTpClPB (2.8%). The sensor was also found to work satisfactorily in partially non-aqueous media up to 25% (V/V) content of acetonitrile, methanol, or ethanol. The response of the sensor was highly selective to Ag (I) over a large number of cations and it could therefore be used for Ag (I) estimation in blood of occupationally exposed persons [28]. R
O O
N
N
O O
R
Figure 11. Structure of [N.N’-bis-(p-methylbenzaldehyde)-4.13-diaza-18-crown-6] A new PVC membrane electrode for manganese (II) ion based on a recently synthesized Schiff base of 5-[(4-nitrophenylazo)-N-hexylamine] salicylaldimine (figure. 12) is reported. The electrode has a fast response time (~10 s), a satisfactory reproducibility and relatively long life time. The proposed sensor revealed good selectivities over a wide variety of other cations include hard and soft metals. This electrode could be used in a pH range of 4.5-7.5. It was used as an indicator electrode in potentiometric titration of manganese (II) ions with EDTA solution [29]. HC
O2N
N2
N
(CH2)5 CH3
OH
Figure 12. Structure of 5-[(4-nitrophenylazo)-N-hexylamine] salicylaldimine 10
Reza Ganjali et al have reported in previously work the presentation a novel gadolinium membrane
sensor
based
on
new
S-N
sulfanylphenyl)imino)-1-methylbutylidene}amino]phenyl
Schiff’s hydrosulfide
base
(2-[{3-[(2-
(figure
13)
(SMPH). The best performance was obtained with a membrane composition of 33% poly (vinyl chloride), 61% benzyl acetate, 2% sodium tetraphenyl borate and 5% SMPH. The potentiometric response of the sensor is independent of the pH of the solution in the pH range of 4.0–8.0. The sensor possesses the advantages of short conditioning time, very fast response time, and especially, very good selectivity towards a large number of cations, such as Sm(III), Ce(III), La(III), Cu(II), Pb(II) and Hg(II). The electrode can be used for at least 9 weeks without any considerable divergence in the potentials. The electrode was used as an indicator electrode in potentiometric titration of Gd (III) ions with EDTA, and recovery of Gd(III) from various binary mixtures. It was also applied to the determination of Gd (III) in a urine sample [30].
H3C
CH3 N
N
S
S
H
H
Figure 13. Structure S-N Shiff base (2-[{3-[(2-sulfanylphenyl) imino)-1methylbutylidene}amino]phenyl hydrosulfide (SMPH). V.K. et al were described the construction and performance characteristics of polymeric membrane electrodes based on two neutral ionophores, N.N’-[bis(pyridi-2yl)formylidene]butane-1.4-diamine
(S1)
and
N-(2-pyridinylmethylene)-1.2-benzene
diamine (S2) (figure. 14) for quantification of cadmium ions. The best performance was obtained with the electrode having a membrane composition (w/w) of (S1) (2.15%): PVC (32.2%):o-NPOE (64.5%):KTpClPB (1.07%). The sensor has been found to work satisfactorily in partially non-aqueous media up to 30% (v/v) content of methanol,
11
ethanol and acetonitrile and could be used for a period of 2 months. The analytical usefulness of the proposed electrode has been evaluated by its application in the determination of cadmium in real samples [31]. N
N
N
N
N
N
(S1)
NH2
(S2 )
Figure 14. N.N’-[bis(pyridi-2-yl)formylidene]butane-1.4-diamine (S1) and N-(2 pyridinylmethyl ene)-1.2-benzenediamine (S2) Reza Ganjali et al have reported the study of the tendency of N-(thein-2-ylethylidene) benzene-1.2-diamine (SNS) (figure 15), towards chromium and some other metals ions, theoretical calculations and conductance studies. It has a fast response time of
