Journal of Nuclear and Radiochemical Sciences, Vol. 6, No. 3, pp. 217-219, 2005

Quaternary Alkylammonium and Alkylphosphonium Pertechnetates: Application toPertechnetate Ion-Selective Electrodes
K. E. German,*, a A. V. Dorokhov,a A. V. Kopytin,b Yu. Politov,b E. N. Pyatova,b A. V. Tarasov,aV. E. Baulin,a V. Peretroukhine,a and A. Yu. Tsivadzea
aInstitute of Physical Chemistry RAS; Russia, Moscow
Kurnakov Institute of General and Inorganic chemistry of RAS; Russiab

Received: July 31, 2005; In Final Form: September 30, 2005
Pertechnetate ion-selective PVC membrane electrodes based on quaternary alkylammonium and phosphonium
salts (bromides and pertechnetates) were examined. The most favorable ionophore was tetradecyltrimethylammonium bromide. The response function was linear within the concentration range 10 −2 –10−6 mol/L and the slope
was 52 mV/pTcO4. The detection limit remained at 5⋅10−7 mol/L. The selectivity and response time of the electrodes was studied and it was found that the electrodes exhibited high selectivity to TcO4 − -anion against the main
inorganic components of radioactive waste solutions and environmental waters (nitrate, sulfate, chloride and others). The electrodes response was stable over a wide pH range.

1. Introduction
Quaternary alkylammonium and phosphonium salts arewidely used for preparation of the membranes giving a response
to different ions. The selectivity of ion determination depends
on hydratation energy of ion and on the nature of membrane
solvent.1 With this approach to a creation of new ion-sensitive
sensors some electrode membranes for different anions andacidocomplexes determination have been developed.2−5 But
only one pertechnetate selective electrode was described earlier.6 However, this liquid membrane electrode has not enoughhigh selectivity and contains concentrated radioactive solution(10−1 M KTcO4). Thus, it can not be widely used in the analysisof the pertecnetate solutions.
The object of present work is a development and an investigation of new ion-selective electrodes for TcO4 − determination.

bodies. Electrode structure is shown in Figure 1. Table 1 summarizes the compositions of the membranes and the internalsolutions of the pertechnetate-selective electrodes employed inthis study.
The external reference electrode was a double-junction Ag/AgCl reference electrode OP-8020 P (Radelkis). The electrochemical potential was measured using pH/ion analyzer OP300 (Radelkis, Hungary) and Ionix-Alpha ionometric combine.
Potassium pertechnetate solutions in 1 mol/L Li 2SO4 wereused for the electrode response function determination. The
selectivity coefficients were determined by the separate solution method (SSM) using 0.01 mol/L potassium or sodium salts
to pH/ion analyser

internal solution(mixture of KCl and KTcO4)

2. Experimental
Te t r a d e c y l t r i m e t h y l a m m o n i u m p e r t e c h n e t a t e[CH3(CH2)13N(CH3)3]TcO4, tetradecylphosphonium pertechnetate [(C10H21) 4P]TcO4, and ethyldiphenyldodecylphosphonium
pertechnetate [(C2H5)P(Ph)2 (C12H25)]TcO4 were synthesized byliquid-liquid extraction of Tc-99 from 0.1 mol/L aqueous solution of NaTcO4 into solution of quaternary ammonium/phosphonium bromide in CH2Cl2. Properties of these compounds werestudied by DTA, IR, Raman spectroscopy and X-ray diffraction.
Membranes preparation. The ionophore{[CH3 (CH2)13N(CH3)3]Br (I), [CH3 (CH2)13N(CH3)3]TcO4 (II),[(C 2 H 5 )P(Ph) 2 (C12 H 25 )]Br (III), [(C10 H 21) 4 P]TcO 4 (IV) or[(C10 H 21) 4 P]Br (V)}, plasticizer (o-nitrophenyloctyl ether,Fluka) and high molecular weight polyvinylchloride (Aldrich)were dissolved in the appropriate volume of cyclohexanone andmechanically stirred. All membrane cocktails were cast in glassrings placed on glass plates. Solvent from PVC membrane wasallowed to evaporate for a week at room temperature. The
thickness of the resulting membranes was about 0.2–0.3 mm.
The electrochemical properties of the electrodes were investigated in the conventional configuration. Small disks were
punched from the cast membranes and mounted in electrode*Corresponding author. E-mail: guerman@ipc.rssi.ru. FAX:
+7-495-335-1778.

Ag/AgCl - wire

PVC tube (electrode body)membrane
Figure 1. Electrode structure.

TABLE 1: ISEs Composition
No of electrode
12
3
4
56
78
9

Activecomponent(ionophore)
IIIIIIIIVIVVV© 2005 The Japan Society of Nuclear and Radiochemical Sciences
Published on Web 12/28/2005

Internal solution composition
KCL, M−51010−410−310−210−310−310−310−310−3KTcO4, M
10−610−510−410−310−510−310−510−310−5

218 J. Nucl. Radiochem. Sci., Vol. 6, No. 3, 2005

Guermannary alkylphosphonium salts is also linear in the range 10−6 –10 −2 mol/L KTcO4 −, with the slope equal to 63 ± 2 mV/pTc at25 ˚C (Figure 5). Electrodes electroanalytical characteristics
remain stable in the range of pH from 1 to 13 (Figure 6). The
electrodes response time is almost the same as for alkylammonium based ISEs.
High potentiometric selectivity to TcO 4 − of the new ISEs
against several important anions was found for all the ISEs
developed (selectivity coefficients are in the range 10 −4 – 10 −7(see Figure 3). It means that TcO4 − can be determined in thepresence of interfering anions with the concentrations of 10 4 –107 times higher than one of TcO4 −). The ISEs have the highest
selectivity of Tc-determination in the phosphates, sulfates andchlorides solutions. These results are of importance: phosphates are the main component of solutions proposed to Tcstripping from anion-exchange resins used in REPA process.
Sulfates are the salt base of Tc-electrodeposition solutions forTc-electroplating. And large amount of chlorides is containedin the radioactive wastes of pyrochemical reprocessing of spentof the anions in accordance with the equationpotlg KTcO4− /anion = (EA–ETcO4−)/S + (1–ZA/ZTcO4)*lg[A][7],were K pot TcO4 /anion is the selectivity coefficient, E TcO4 is thepotential measured in 0.01 mol/L solution of KTcO4, EA is thepotential measured in 0.01 mol/L solution of the interfering
anion, S is the slope of the response function, ZTcO4 and ZA are
the charges of the pertechnetate anion and the interfering anion
respectively, [A] is the concentration of the interfering anion.
The influence of pH on the electrode response was examined by adjusting the pH of the measured solution with 1 mol/L
sodium hydroxide and hydrochloric acid. Potassium chloride
aqueous solution (1 mol/L) was used as a background electrolyte.
3. Results and Discussion
The only pertechnetate selective electrode was described earlier.7 It is the liquid membrane electrode based on IV. However,this electrode has not enough high selectivity and contains concentrated radioactive solution (10−1 M KTcO4). Therefore, it can
not be widely used in the analysis of the pertecnetate solutions.
We have developed new TcO 4 − ISEs based on quaternaryammonia and phosphonia ionites with low radioactive internalsolution. The response functions for electrodes based on I withdifferent solution composition are shown in Figure 2. For allthese electrodes response function is linear in the range 10−6 –10−2 mol/L KTcO4 with the slope equal to 59 ± 2 mV/pTc at 25
˚C. The concentration of KTcO4 in the internal solution has nomarked influence on response function as well as on selectivity[Figure 2 (electrodes No 1– 4); Figure 3 (electrodes No 1, 2)]
but addition of pertechnetate into the internal solution is necessary in order that TcO4 -ISEs work stable. Thus, low radioactive diluted pertechnetate solutions (10 −5 – 10 −6 mol/L) can beused in the TcO4 − ISEs.
The electrodes 1– 4 are workable in the wide range of pH –from 0.5 to 13 (see Figure 4). The electrodes response time is3– 5 min for diluted pertechnetate solutions and less then 1 minfor concentrated solutions. Almost the same results have beenobtained with tetradecyltrimethylammonium pertechnetate (II)and, therefore, it is possible to apply non-radioactive membranes in the TcO4-ISEs.
The response function for the electrodes based on quater-

350
300

E, mV

250
200
150
100
50
0-7-6-5-4-3-2lgC(KTcO4)
Figure 2. Electrode response function for ISEs 1–4. l – 1; × – 2; –3; t – 4. The numbers of electrodes follow the corresponding numbers in table 1.

Electrode numberlg K TpcoOt − / anion
42-8

1795Ref.6

ClO4-ReO4--7-6-5-4-3-2-1
0
1

anion

2NO3-Cl -B r-SO42-

CO32-

PO43-

J-

Figure 3. Potentiometric selectivity coefficients for some of TcO4 − -ISEs developed to compare with the electrode described in [7].

F-J. Nucl. Radiochem. Sci., Vol. 6, No. 3, 2005 219

Quaternary Alkylammonium and Alkylphosphonium Pertechnetates20040086300

150E, m VE, mV350

25020010014150

Figure 4. Influence of pH on the electrode response function (ISENo 1). (10 −4 mol/L KTcO4 in HCl/KCl/KOH solutions, backgroundelectrolyte – 1 mol/L KCl).

1000246pH

1081212345678910 11 12 13 14pHFigure 6. Influence of pH on the electrode response function (ISENo 6, 8). (10−4 mol/L KTcO4 in HCl/KCl/KOH solutions, backgroundelectrolyte – 1 mol/L KCl).

4003002006E,m V

0100

main inorganic components of radioactive waste solutions andenvironmental waters (nitrate, sulfate, chloride and others) and,
therefore, they can be applied to the analyses of Tc in somekinds of technological solutions formed in the reprocessing ofthe spent nuclear fuel.

8Acknowledgements. The authors are much thankful to theRFBR, the RFASIE and “Ionix-Alfa” assistance for the supplied ionometric equipment.

07-1009References5(1) N. Lakshminarayanaiah, Membrane electrodes. Academic
Press. New York, San Francisco, London 1976.-360 p.
(2) B. Fu, E. Bakker, J. H. Yun, V. C. Yang, and M. E. Meyerhoff,Analytical Chem. 66, 2550 (1994).
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Odasima, and Y. Umezawa, J. Am. Chem. Soc. 120, No13,3049 (1998).
(4) A. Schwake, K. Cammann, A. L. Smirnova, S. S. Levitchev,V. L. Khitrova, A. L. Grekov, and Yu. G. Vlasov, Anal. Chim.
Acta 393, 19 (1999).
(5) E. M. Rakhimenko, I. Prilutskaya, T. M. Yakimenko, andO. V. Yakimenko, Proceedings of the National Academy ofSciences of Belarus. Series of Chemical sciences, No1(2000), 18-23.
(6) G. A. Akopov, M. K. Abdulahatov, and A. P. Krinitsyn,Radiochem. 28, No 3, 434 (1986).
(7) G. G. Guilbault, R. A. Drust, M. S. Frant, H. Freiser, E. H.
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J. Rohm, W. Simon, and J. D. R. Thomas, Pure Appl. Chem.
48, 127 (1976).

-200-7-6-5-4-3-2lgC(KTcO4 )Figure 5. Electrode response function for ISEs 5–9.

nuclear fuel. The ISEs selectivity against NO3− anions is lower
but with the electrodes 1 and 2 it is possible to determine Tc insome back extraction and wasting nitric acid solutions ofimproved PUREX.
The selectivity of alkylammonium ISEs is slightly better
than those of alkylphosphonium but all the new Tc-ISEs havebetter characteristics compared to earlier proposed ISE withliquid membrane6 (see Figure 3). Studies of some new Tc-ISE
are in progress.
4. Conclusion
The electrodes proposed do not contain high radioactive
solutions and possess high selectivity to TcO 4 − against to the