Next Article in Journal
Quartz Crystal Microbalance Coated with Sol-gel-derived Thin Films as Gas Sensor for NO Detection
Previous Article in Journal
Chemical Sensors – from Molecules, Complex Mixtures to Cells – Supramolecular Imprinting Strategies
 
 
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

PVC Based Selective Sensors for Ni2+ Ions Using Carboxylated and Methylated Porphine

Central Building Research Institute Roorkee – 247 667 (Uttranchal) India
*
Author to whom correspondence should be addressed.
Sensors 2003, 3(9), 393-403; https://doi.org/10.3390/s30900393
Submission received: 10 August 2003 / Accepted: 24 August 2003 / Published: 11 September 2003

Abstract

:
Poly vinylchloride (PVC) based membranes of 4,4',4'',4'''-21H,23H-porphine– 5,10,15,20 –tetrayl) tetrakis (benzoic acid) (TBAP)  and 2,3,7,8,12,13,17,18-octamethyl - 21H, 23H-porphine (OMP) were prepared using dibutyl phthalate (DBP), dioctylphthalate (DOP), dibutyl(butyl)phosphonate (DBBP) and 1-chloronaphthalene (CN) as plastcizing solvent mediators and sodium  tetraphenylborate (NaTPB) as an anion excluder for Ni2+ selective sensors. TBAP based membrane exhibits linearity over a wide concentration range 2.0x10-6–1.0x10-1M (0.12 – 5.8x103ppm) with a slope of 29.6 mV/decade of activity while OMP based membrane showed linear potential response in the concentration range 1.0x10-5 –1.0x 10-1M (0.60 – 5.8x103ppm) with a Nernstian slope of 29.0 mV/decade of activity. The electrode assembly works between pH 2.0 – 7.0, exhibits a fast response time of 10-15s and performed satisfactorily over a period of six months with good reproducibility. Excellent selectivity of the order of 10-3 over a number of cations and quantitative determination of Ni2+ in effluents discharged from electroplating industry demonstrates the utility of the proposed sensor. The electrode  assembly was also used as an indicator electrode in the potentiometric titration of Ni2+  with EDTA.

Introduction

Utility of chemical sensors responding selectively to a specific ion in diverse samples viz. soils, industrial effluents, pharmaceutical compounds, clinical analyses etc. is well established. The technique is fast, accurate, low-cost and the sample used for analysis is small and non-destructive. Extensive efforts made during the last 4-5 decades resulted the availability of sensors for alkali, alkaline earth metals and few anions, however, success with regard to heavy metals is still limited and lacks in commercial availability. Efforts are therefore, continued to develop sensors for heavy metals exhibiting better performance with regard to selectivity, sensitivity and reproducibility. Determination of nickel assumes importance due to its toxic nature, widespread use in catalytic processes and its presence in various effluents. The toxicity of nickel can cause dermatitis, asthma and disorder of central nervous system. A survey of literature reveals that the first nickel-selective electrode was reported by Pungor and co-workers using a nickel-dimethylglyoxime complex [1]. Later heterogeneous membranes of nickel phosphate in paraffin and silicone rubber [2], nickel bis-(2-ethylhexyl) phosphate in PVC [3] and a nickel complex of 1,4,8,11–tetraazacyclotetradecane in Araldite [4] were used for preparing electrodes. In addition to these solid membrane ion selective electrodes (ISEs), liquid membrane electrodes for nickel using O,O'-diisobutyldithiophosphatonickel(II) in chlorobenzene [5], bis (tetraethyl ammonium) bis (dithiobenzophenazine) nickelate in nitrobenzene [6] and nickel diethyl dithiocarbamate in chloroform [7] have also been reported. Apart from these, few other sensors have also been reported using inorganic and organic ion-exchangers as sensor materials [8,9,10].
The use of Porphines as sensor material for membrane has been reported recently [11,12,13]. Porphines are aza, cyclic molecules capable of forming electron rich interior cavities in which metal cation is encapsulated through ion-dipole interactions as two pyrrolenine nitrogens are capable of accepting two protons and two -NH groups capable of losing equal number of protons. In continuation of our work on the development of selective nickel-sensor [14,15,16], the use of carboxylated and methylated porphines as active constituents for the membranes has been investigated and the results are presented herein.

Experimental

Reagents

All regents were of analytical– reagent grade. Porphine, (4,4',4'',4'''-21H,23H-porphine–5,10,15,20– tetrayl)tetrakis(benzoic acid)(TBAP) and 2,3,7,8,12,13,17,18-octamthyl-21H, 23H-porphine (OMP) were procured from Aldrich (Milkwaukee, USA) and high molecular mass poly vinylchloride (PVC) was obtained from (GSC, India). Sodium tetraphenylborate (NaTPB) from BDH (Poole, Dorset, UK), dibutylphthalate (DBP) and dioctylphthalate (DOP) from Reidel (India), dibutyl(butyl)phosphonate (DBBP) from Mobil, (Richmond, USA) and 1-chloronaphthalene (CN) from Merck (Darmstadt, Germany) were used without further purification. Organic solvents were purified by distillation and solutions of metal salts (nitrates) were prepared in double distilled water.
Sensors 03 00393 i001

Preparation of membranes

The PVC-based membranes were prepared by the method of Craggs et al. [17]. Varying amounts of the ion-active phase (porphine) and an appropriate amount of PVC were dissolved in 20 ml THF. The anion excluder, NaTPB and solvent mediators, DBP, DOP, DBBP and CN were also added in some cases to get membranes of different compositions. The solution thus obtained, after complete dissolution of the various components, was poured into acrylic rings placed on a smooth glass plate and allowed to evaporate at room temperature. After 48h, transparent membranes of 0.5mm thickness were obtained. The ratio of membrane ingredients, time of contact and concentration of equilibrating solution were optimized so that the membranes produce reproducible, noiseless and stable potentials. Membrane to membrane reproducibility was assured by carefully following the optimum conditions of fabrication. Composition of the membranes, which gave best performance, is listed in Table 1 and Table 2 along with other characteristics.

Potential measurements

The membranes were equilibrated for 3-5 days in 0.5 M Ni2+ solution. The potential measurements were carried out at 25 ± 0.1°C with a Mettler Toledo pH/ion analyzer (model MA235) by setting up the following cell assembly. Sensors 03 00393 i002 Saturated calomel electrodes (SCE) were used as reference electrodes. The response time of the membrane sensors is the time in which stable and constant potentials are obtained.
Table 1:. Composition and response characteristics of PVC based TBAP membranes selective for Ni2+ ions
Table 1:. Composition and response characteristics of PVC based TBAP membranes selective for Ni2+ ions
Electrode/
Membrane
No.
%(w/w) of various componentsWorking concn.
range, M
Slope,
mV/decade
of activity
Response
time, sec
TBAPDBPDOPDBBPCNNaTPBPVC
110----5855.5 x 10-5 – 1.0 x 10-126.060
21030---5552.0 x 10-5 – 1.0 x 10-128.515
310-30--5555.5 x 10-5 – 1.0 x 10-134.020
410--30-5552.0 x 10-6 – 1.0 x 10-129.615
510---305555.6 x 10-5 – 1.0 x 10-135.310
Table 2:. Composition and response characteristics of PVC based OMP membranes selective for Ni2+ ions
Table 2:. Composition and response characteristics of PVC based OMP membranes selective for Ni2+ ions
Electrode/
Membrane No.
%(w/w) of various componentsWorking concen.
Range, M
Slope,
mV/decade
of activity
Response
time, sec
OMPDBPDOPDBBPCNNaTPBPVC
610----5851.0 x 10-4 – 1.0 x 10-132.460
71030---5555.0 x 10-5 – 1.0 x 10-137.720
810-30--5553.6 x 10-5 – 1.0 x 10-138.815
910--30-5555.6 x 10-5 – 1.0 x 10-130.115
1010---305551.0 x 10-5 – 1.0 x 10-129.010

Results and Discussion

Working concentration range

The potential response of all the membrane sensors was studied in the concentration range 1.0x10-6–1.0x10-1M Ni2+ (Fig.1 & Fig.2). TBAP based membrane electrode No.1 (without solvent mediator) exhibited linearity in the concentration range 5.0x10-5–1.0x10-1M with a slope of 26.0 mV/decade of activity while the membrane consisting of OMP as electroactive ingredient showed a linearity in the concentration range 1.0 x 10-4 – 1.0 x 10-1 M with a slope of 32.4 mV/decede of activity. The potentials generated across these membranes are ascribed to the uptake of nickel ions on porphine. Plasticizers are frequently used to enhance the response characteristics, i.e. working concentration range, slope etc. The effect of addition of plasticizers to the membrane was, therefore, studied and significant improvement with regard to working concentration range and slope was observed. Addition of solvent mediators DBP and DBBP improved the performance of TBAP based membrane, exhibiting a working concentration range of 2.0x10-5–1.0x10-1 and 2.0x10-6–1.0x10-1M with slopes of 28.5 and 29.6 mV/ decade of activity, respectively. The addition of solvent mediators DOP and CN had no significant improvement in the performance of the electrode.
Figure 1:. Variation of cell potential with Ni2+ concentration; PVC based membranes of TBAP without plasticizer (1), with plasticizers, DBP(2), DOP(3), DBBP(4) and CN(5).
Figure 1:. Variation of cell potential with Ni2+ concentration; PVC based membranes of TBAP without plasticizer (1), with plasticizers, DBP(2), DOP(3), DBBP(4) and CN(5).
Sensors 03 00393 g001
Figure 2:. Variation of cell potential with Ni2+ concentration; PVC based membranes of OMP without plasticizer (6), with plasticizers, DBP(7), DOP(8), DBBP(9) and CN(10).
Figure 2:. Variation of cell potential with Ni2+ concentration; PVC based membranes of OMP without plasticizer (6), with plasticizers, DBP(7), DOP(8), DBBP(9) and CN(10).
Sensors 03 00393 g002
For OMP based membrane, addition of solvent mediators CN improved the electrode characteristic with a wide working concentration range of 1.0x10-5–1.0x10-1M and a Nernstian slope value i.e., 29.0 mV/decade of activity while addition of other solvent mediators, DBP, DOP and DBBP slightly improved the performance of the electrode. Similar behaviour has been observed by us as well as other workers [18,19,20]. Repeated monitoring of potentials on the same portions of the sample gave a standard deviation of ±0.3 mV. The standard deviation of the slope was ±0.8 mV, which shows good reproducibility of the electrode assembly.

Response and lifetime

The response time of the membranes without solvent mediators was found to be approximately 1 min. The addition of solvent mediators improved the response time significantly with the best results shown by electrode nos. 4(15s) and 10(10s) (Fig.3) over the entire concentration range, the potentials remain constant for more than 5 min. Membrane electrode nos. 4 and 10 were henceforth selected for further studies. The membranes could be used over a period of six months without observing significant change in slope and response time and this could be corrected by re-equilibrating the membrane with 0.5 M Ni2+ solution for 2-3 days. During usage, they were stored in 0.1M Ni2+ solution.
Figure 3:. Response time of membrane electrode (Nos. 4 and 10) at 1.0x10-3M Ni2+ concentration.
Figure 3:. Response time of membrane electrode (Nos. 4 and 10) at 1.0x10-3M Ni2+ concentration.
Sensors 03 00393 g003

pH and non-aqueous effect

The pH dependence of the electrodes potential for 1.0 x 10-3 and 1.0 x 10-4 M Ni2+ ions was tested over the pH range 1.0-8.0 (adjusted with HNO3 or NaOH). It can be seen from Fig. 4 that the potentials
Figure 4:. Effect of pH on cell potential of electrode Nos. 4 and 10 at 1.0x10-3M (a, b) and 1.0x10-4M (c, d) Ni2+ concentration
Figure 4:. Effect of pH on cell potential of electrode Nos. 4 and 10 at 1.0x10-3M (a, b) and 1.0x10-4M (c, d) Ni2+ concentration
Sensors 03 00393 g004
are independent of pH in the range 2.0 to 7.0 and the same can be taken as the working pH range of the electrodes. Above and below these pH values, the sharp change in potentials may be due to the hydrolysis of Ni2+ and H+ ions co-transport, respectively.
The utility of the membrane sensors was also investigated in partially non-aqueous media using methanol-water and ethanol-water mixtures. The membranes work satisfactorily in mixtures having up to 25% (v/v) non-aqueous content without showing any appreciable change in working concentration range or slope. However, above 25% non-aqueous content, potentials show drift with time.

Potentiometric selectivity

The usefulness of a sensor depends on its selectivity over other ions. It is the most important characteristic, which defines the extent to which the device may be successfully employed. Potentiometric selectivity was investigated by using IUPAC recommended Match Potential Method (MPM). The selectivity coefficient values of the order of 10-3 (Table 3) clearly indicate that the electrodes are selective to Ni2+ over a number of other cations (except for Co2+). The electrode based on TBAP (electrode no. 4) is more selective to Ni2+ ions in comparison to that based on OMP (electrode no. 10).
Table 3:. Selectivity coefficient values Sensors 03 00393 i003 for Ni2+ -selective sensors (electrode nos. 4 and 10) as calculated by Match Potential Method
Table 3:. Selectivity coefficient values Sensors 03 00393 i003 for Ni2+ -selective sensors (electrode nos. 4 and 10) as calculated by Match Potential Method
Interfering ion, BSelectivity coefficients, Sensors 03 00393 i003
Electrode No. 4Electrode No. 10
NH4+1.4 x 10-22.0 x 10-2
Na+9.0 x 10-28.2 x 10-2
K+5.3 x 10-22.0 x 10-2
Tl+3.2 x 10-21.9 x 10-2
Cs+4.7 x 10-21.4 x 10-2
Cu2+1.2 x 10-31.8 x 10-3
Ca2+1.4 x 10-31.2 x 10-3
Sr2+1.9 x 10-32.5 x 10-3
Ba2+2.0 x 10-32.0 x 10-3
Mg2+1.4 x 10-32.8 x 10-3
Co2+2.3 x 10-14.8 x 10-1
Cd2+2.6 x 10-32.4 x 10-3
Zn2+2.2 x 10-32.6 x 10-3
Hg2+1.4 x 10-31.4 x 10-3
Pb2+1.4 x 10-31.6 x 10-3
Fe3+1.8 x 10-31.4 x 10-3
Al3+2.0 x 10-31.9 x 10-3
Ce3+2.8 x 10-31.8 x 10-3
Co2+ ions are likely to cause some interference, as the selectivity coefficient values are high (0.23 and 0.48), however, if Co2+ is present in lower concentration these will not interfere, as selectivity is concentration dependent [21]. Thus, to determine the concentration of Co2+ ions, which can be tolerated in the determination of Ni2+, some mixed runs studies were carried out [22,23,24,25,26]. It is seen from Fig. 5 that Co2+ ions at ≤5.0 x 10-4M cause no deviation in the original working concentration plot (as obtained in pure Ni2+ solution for electrode no. 4). Thus, the electrode can tolerate Co2+ ions up to the concentration 5.0x10-4M over the entire working concentrations range i.e., the presence of Co2+ ions does effect in the working of the electrode assembly. However, when Co2+ is present at higher concentrations, the electrode can be used to determine Ni2+ over reduced concentration range only. Fig. 5 shows that at 1.0x10-3 and 1.0x 10-2M Co2+ ions, the electrode assembly can be used to determine Ni2+ in the concentration ranges 5.0 x 10-5- 1.0 x 10-1M and 1.0 x 10-3 – 1.0 x 10-1M, respectively.

Analytical applications

Estimation of Ni2+ in effluents

The sensor has been successfully used to determine the nickel in effluent discharged from local electroplating works. Four samples of plating waste were collected, filtered and stored. After adjusting the pH, the nickel in each sample was determined from potential measurement data using the calibration graph. The data presented in Table 4, indicates that the amount of nickel determined in
Figure 5:. Variation of cell potential with Ni2+ concentration at different concentration levels of Co2+ ions (electrode no. 4).
Figure 5:. Variation of cell potential with Ni2+ concentration at different concentration levels of Co2+ ions (electrode no. 4).
Sensors 03 00393 g005
Table 4:. Nickel concentration in effluents from electroplating industry as determined with AAS and membrane sensor
Table 4:. Nickel concentration in effluents from electroplating industry as determined with AAS and membrane sensor
SamplesPHNi2+ as determined byAAS, mg l-1Ni2+ as determined by sensor 4, mg l-1
Foundafter Adjustment
16.803.7044.047.0
26.65.3.8043.547.0
36.703.6543.046.0
46.903.7542.045.0
effluent by sensor is in close agreement with that determined by use of atomic absorption spectrophotometer (AAS).

Potentiometric titration

The analytical application of the electrode was tested by using it as an indicator electrode in the potentiometric titration of Ni2+ with EDTA. A 10 ml of 1.0 x 10-3M Ni2+ solution was titrated against 1.0 x 10-2M EDTA solution at pH 7.0 (Fig. 6). A sharp break point was observed which corresponds to the stoichiometry of Ni(II)-EDTA complex, therefore, Ni2+ can be determined potentiometrically using the proposed electrode assembly.
Figure 6:. : Potentiometric titration plot of Ni2+ ions (1.0x10-3 M) with EDTA (1.0x10-2 M), electrode no. 4 and electrode no. 10
Figure 6:. : Potentiometric titration plot of Ni2+ ions (1.0x10-3 M) with EDTA (1.0x10-2 M), electrode no. 4 and electrode no. 10
Sensors 03 00393 g006

Conclusion

The membrane assembly prepared using TBAP as membrane ingredient with plasticizers (DBBP) and anion excluder (NaTPB) exhibited linearity over a wide concentration range (2.0x10-6–1.0x10-1M) with Nernstian slope (29.6 mV/ decade of activity), fast response time (15s), long lifetime (6 months) and selectivity (of the order of 10-3) over a number of cations. The results presented in this paper show that the PVC matrix membrane of TBAP is superior sensor than those reported earlier [1,2,3,4,5,6,7,8,9,10,14,15,16]. The results obtained during the investigation are indicative of the applicability of the sensor for evaluation of Ni2+ in effluents, wastewater and industrial wastes for subsequent use in building products.

Acknowledgements

The paper is being published with the permission of Director, Central Building Research Institute (CBRI), Roorkee. Author (LPS) is thankful to Department of Science & Technology (DST), New Delhi for financial assistance under Fast Track Young Scientist Scheme.

References

  1. Pungor, E.; Toth, K.; Havas, J. Acta. Chim. Acad. Sci. Hung. 1966, 48, 17.
  2. Buchanan, E.B.; Scago, J.L. Acta. Chim. 1968, 40, 517.
  3. Awasthi, S.P.; Kulkarni, V.T.; Sundaresan, M. J. Electrochem. Soc. India 1988, 37, 309.
  4. Lal, U.S.; Chattopadhyaya, M.C.; Dey, A.K. J. Ind. Chem. Soc. 1982, 49, 493.
  5. Materova, E.A.; Muchovikov, V.V.; Grigorieva, M.G. Anal. Lett. 1975, 8, 167.
  6. Luca, C.; Maria, P.; Nicolae, M. Rev. Chim. 1976, 27, 1088.
  7. Smirnova, E.V.; Petrukhin, O.M.; Rogatinskaya, S.L. Zh. Anal. Khim. 1982, 37, 2137.
  8. Hampton, M.D.; Peters, C.A.; Wellington, L.A. Acta. Chim. Acta. 1987, 194, 171. [CrossRef]
  9. Lebedera, O.A.; Jansons, E. Latv. PSR Zinat. Akad. Vestis. Kim. Ser. 1986, 4, 423.
  10. Rao, G.N.; Srivastava, S.K.; Singh, M. Talanta 1996, 43, 1821.
  11. Chaniotakis, N.A.; Chasser, A.M.; Meyerhoff, M.E. Anal. Chem. 1988, 60, 88.
  12. Jyo, A.; Minakami, R.; Kanda, Y.; Egawa, H. Sens. & Actuators B 1993, 13–14, 200.
  13. Gao, D.; Jun, G.; Yu, R.; Zheny, G. Analyst 1995, 120, 499.
  14. Singh, L.P.; Vardhan, H. Anal. Proc. 1995, 32, 193.
  15. Jain, A.K.; Gupta, V.K.; Singh, R.D.; Khurana, U.; Singh, L.P. Sens & Actuators B 1997, 40, 15.
  16. Gupta, V.K.; Jain, A.K.; Singh, L.P.; Khurana, U. Anal. Chim. Acta 1997, 335, 33. [CrossRef]
  17. Craggs, A; Moody, G.J.; Thomas, J.D.R. J. Chem. Edu. 1974, 51, 541.
  18. Assubai, F.N.; Moody, G.J.; Thomas, J.D.R. Analyst 1988, 113, 61.
  19. Chan, W.H.; Shiu, K.K.; Gu, X.H. Analyst 1993, 118, 863.
  20. Jain, A.K.; Gupta, V.K.; Singh, L.P.; Khurana, U. Analyst 1997, 122, 583.
  21. Saez de Viteri, F.J.; Diamond, D. Analyst 1994, 119, 749.
  22. Srivastava, S.K.; Gupta, V.K.; Jain, S. Analyst 1995, 120, 495.
  23. Srivastava, S.K.; Gupta, V.K.; Jain, S. Anal. Chem. 1996, 68, 1272.
  24. Jain, A.K.; Singh, L.P.; Jain, P.K. Sens & Actuators B 1995, 25, 729.
  25. Jain, A.K.; Gupta, V.K.; Sahoo, B.B.; Singh, L.P. Anal. Proc. 1995, 32, 99.
  26. Jain, A.K.; Gupta, V.K.; Singh, L.P. Anal. Proc. 1995, 32, 263.
  • Sample Availability: Available from the authors.

Share and Cite

MDPI and ACS Style

Singh, L.P.; Bhatnagar, J.M. PVC Based Selective Sensors for Ni2+ Ions Using Carboxylated and Methylated Porphine. Sensors 2003, 3, 393-403. https://doi.org/10.3390/s30900393

AMA Style

Singh LP, Bhatnagar JM. PVC Based Selective Sensors for Ni2+ Ions Using Carboxylated and Methylated Porphine. Sensors. 2003; 3(9):393-403. https://doi.org/10.3390/s30900393

Chicago/Turabian Style

Singh, L. P., and J. M. Bhatnagar. 2003. "PVC Based Selective Sensors for Ni2+ Ions Using Carboxylated and Methylated Porphine" Sensors 3, no. 9: 393-403. https://doi.org/10.3390/s30900393

Article Metrics

Back to TopTop