PVC membrane electrodes

Another aspect of tin as a constituent of electrode material is shown by tin(IV)TPP complexes incorporated into PVC membrane electrodes. These increase the selectivity to salicylate over anions such as Cl-, Br- I-, I()4, Cl()4, citrate, lactate and acetate. The specificity is attributed to the oxophilic character of the Sn ion in TPP at the axial coordination sites. Indeed, carboxyl groups incorporated into the membrane polymer compete for these binding sites. The complete complex structure is important. Substitution of TPP with octaethylporphirine results in loss of salicylate selectivity231. Preparation and analytical evaluation of a lead-selective membrane electrode, containing lead diethyldithiocarbamate chelate, has also been described232. 

Although not strictly relevant to amperometric sensor technology, various metalloporphyrins [Co(III), Mn(III), Fe(III) Fig. 45] have been shown to sense anions potentiometrically with selectivity sequences dependent on the centrally bound metal (Amman et al., 1986 De et al., 1994). For example the anti-Hofmeister selectivity sequence SCN" > I" > CIO4 > N02 > Br > Cl- > NOJ was exhibited by PVC membrane electrodes containing [87]. 

The PVC membrane electrode based on new Schiff base complexes of 2,2-[(l,3,dimethyl-l,3-propanediylidene)dini-trilojbis-benzenethiolato with Cd(II) [381] and cadmium-salen N, Ai -bis-salicyli-dene-l,2-ethylenediamine) complex [382] were used as the selective electrodes for tiocyanate ions. 

PVC membrane electrodes allowed measurement of potentiometric selectivity coefficients. These showed the Eu(III) complex to be more selective for chloride than the Pr(III), Dy(III) or Yb(III) analogues. 

The anions derived from 277-thiopyran 1,1-dioxides behave as ligands for various transition metal single site catalysts 591 that are employed for the polymerization of olefins <2002USP2002156211>. A nickel(ll) ion selective PVC-membrane electrode based on the 2,6-diphenyl-277-thiopyran 592 has been described. The electrode exhibits a Nernstian response over a wide concentration range of Niz+ with a lower detection limit of 9 X 10-6M and a response time of ca. 10 s <2000ELA1138>. 

Shono, T., Okahara, M., Ikeda, I., Kimura, K., andTamura, H., Sodium-selective PVC membrane electrodes based on bis(12-crown-4)S. /. Electroanal. Chem. 132, 99-105 (1982). 

Yan, Z.N., Lu, YQ. and Li, X. (2006) The preparation of silver ion selective PVC membrane electrode based on neutral ionophore tetramethylene bis(N-ethyl-N-phenyldithiolcarbamate). 

The same group most recently reported the use of neutral lanthanide(III) tris-diketonates of type 121 for the determination of chloride [84]. The response in luminescence of the Eu(III) complex for chloride in acetonitrile solution was large enough to be seen by the naked eye. Incorporation of the complexes in PVC membrane electrodes allowed measvuement of potentiometric selectivity coefficients. These showed the Eu(III) complex to be the more selective for chloride than the Pr(III), Dy(III) or Yb(III) analogues. 

Figure 6. Typical calibration curve toward sulfite for Hg(DDC)2 PVC membrane electrode (solid line is theroetical Nernstian slope line).

Figure 7. Flow-through gas sensing arrangement used to evaluate Hg(DDC)2-PVC membrane electrodes for selective detection of sulfites as S02 ...

Liquid-membrane electrodes (including PVC-membrane electrodes)... 

MT = Membrane type G = Glass-membrane electrode P = PVC-membrane electrode S = Solid-state membrane electrode ... 

M = gas-permeable membrane electrode. Glass and solid-state membranes are more resistant to certain organic solvents (acetone, methanol, benzene, dioxane. etc.). PVC-membrane electrodes must not be allowed to come into contact with any organic solvent. becau.se this dramatically reduces the lifetime of the electrode. 

A Nafion film-coated micro-electrode is very advantageous for in vivo detection of neurotransmitter-related species such as dopamine and catecholamine . The partition and diffusion of the substance in the coating film are generally important factors that influence the response characteristics of the coated electrode. A quinonoid polymer electrode, prepared by the electrochemical oxidation of mercaptohydro-quinone and modified with mercaptide, functioned as a selective ion sensor for heavy metal ions such as Ag", Hg , Cd , and Cu in solution A PVC membrane electrode containing macrocyclic polyethers with sulfur atoms (id) exhibited appreciable selectivity for Ca " " relative to Mg ", alkali metal ions and... 

Gao D, Li J-Z, Yu R-Q, Zheng G-D (1994) Metalloporphyrin derivatives as neutral carriers for PVC membrane electrodes. Anal Chem 66 2245-2249... 

Using PVC-membrane electrodes a wide variety of alternative exchanger systems have been investigated and the results show that a solution of calcium bis[di-4-(l,1,3,3-tetramethylbutyl)phenyl phosphate] in dioctyl phenylphosphonate is preferred at present. However, calcivun ISE based upon a neutral carrier, N,N -dir(il-ethoxycarbonyl)-undecylJ-N,N -4,5-tetramethyl-3,6-dioxaoctane diamide, are gaining acceptance, particularly in the clinical field. 

When dioctyl phenylphosphonate (DOPP) was introduced into a membrane containing 5% w/w DAPH, this markedly improved its selectivity compared to other CBS systems (Table 1). A response comparable to a PVC-membrane electrode was obtained when 25% w/w DOPP was present. However, because the DOPP present was merely physically entangled within the matrix and not covalently-bound, the lifetime of this system was not good and the selectivity gradually deteriorated indicating that loss of DOPP was occurring. 

PVC-membrane electrode. Thus, a calcium ISE sensor unit from a TAP electrode (which exhibited a Nernstian response to Ca " ) was filled with 1 cm of 2.5 x 10" M CaCl2 solution (0.2 mCi activity) and suspended in 10 cm of unlabelled 10"5 m CaCl2. A PVC-membrane was similarly treated. Aliquots (25 yl) of the outer solutions were taken at frequent intervals, dried and counted. With the PVC-membrane,... 

H.M. Abu Shawish, S.M. Saadeh, A.R. Al-Dalou, N.A. Ghalwa, A.A.A. Assi, Optimization of tramadol-PVC membrane electrodes using miscellaneous plasticizers and ion-pair complexes, Materials Science and Engineering C, 31 (2), 300-306,2011. 

Potentiometry HPO42- 16 0.5 Novel PVC membrane electrode containing vanadyl salophen, high selectivity, operational life of 14 weeks [113]... 

Initial studies on the performance of mini-PVC membrane electrodes for blood analysis were encouraging [9]. In this study, 44 plasma samples were analysed for sodium with the calixarene methyl tetraester-based PVC electrodes, and the results compared with those obtained with a SMAC-Technion Analyser. Good correlation was found (r = 0.95), but a systematic bias was apparent due to the calibration regime used in the study. A more detailed report of these investigations published the following year confirmed the utility of applying the sensors based on 2 to the analysis of sodium in blood [10]. 

In parallel with these studies, other ligands were assessed for use in sodium-selective electrodes, including the methyl, butyl, and adamantyl ketone tetramers of p-f-butylcalix[4]arene. However, only the methyl ketone derivative produced satisfactory PVC membrane electrodes [6]. These were subsequently applied to the analysis of sodium in plasma samples [11]. Excellent correlations (r = 0.979, r = 0.987 and r = 0.951, n = 10) were found in comparative tests with three reference... 

Fig. 3. Plasma sodium analysis results obtained with a PVC membrane electrode based on 1 compared with a SMAC analyser. The electrode was part of an array of ISEs which were carefully calibrated before use. Bias in the results was eliminated through the use of a flow-injection analysis (FIA) approach which enabled the entire sample handling and analysis to be automated. These results demonstrate clearly the successful application of calix[4]arene-based ISEs to this important assay (from reference [15] with permission).

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