1224
Anal. Chem. 1982, 5 4 , 1224-1227
aromatic aldehydes. While additional studies are under way in our laboratory for a number of other carbonyls including ketones, dicarbonyls, and hydroxycarbonyls, the method is now suitable for measurement of parts per billion levels of aldehydes in air.
ACKNOWLEDGMENT R. Atkinson operated the dynamic dilution apparatus. LITERATURE CITED (1) Board on Toxicology and Environmental Health Hazards, National Research Council "Formaldehyde and Other Aldehydes"; National Academy Press: Washington, DC, 1981. (2) Fung, K.; Grosjean, D. Anal. Chem. 1981, 5 3 , 188-171. (3) Grosjean, D.; Fung, K.; Atklnson, R. Paper No. 80-50-4, 73rd Annual Meeting of the Air Pollution Control Association, Montreal, Canada, June 23-27, 1980.
(4) Kuwata, K.; Ureobl, M.; Yamasaki, Y. J . Chromatogr. Scl. 1979, 17, 264-268. (5) Lowe, D. C.; Schmidt, U.; Ehhalt, D. H.; Frischkown, C. G. 0.; Nurnberg, H. W. Environ. Scl. Technoi. 1981, 15, 819-823. (6) Beasley, R. K.; Hoffman, C. E.; Rueppel, M. L.; Woriey, J. W. Anal. Chem. 1980, 52, 1110-1114. (7) Kuntz, R.; Lonneman, W.; Namle, G.; Hull, L. A. Anal. Lett. 1980, 13, 1409-1415. (8) Grosjean, D. Environ. Sci. Techno/.,In press. (9) Fung, K.; Swanson, R. D.; Grosjean, D. Paper No. 81-47-1, 74th Annual Meeting of the Air Pollution Control Association, Philadelphia, PA, June 21-26, 1981. (10) Andersson, G.; Andersson, K.; Nlesson, C. A,; Levln, J. 0. Chemosphere 1979, 8 , 823-827. (11) Nltzert, V.; Seiler, W. Geophys. Res. Lett. 1981, 8 , 79-82.
RECEIVED for review December 21,1981. Accepted March 2, 1982.
Coated Wlre Sodium- and Potassium-Selective Electrodes Based on Bis(crown ether) Compounds Hlroshl Tamura, Kellchl Klmura, and Toshiyukl Shono * Department of Applied Chemistry, Faculty of Engineering, Osaka University, Yamada-oka, Suita, Osaka 565, Japan
We have so far noted that some bis(crown ether) compounds work well as a neutral carrier of Na-, K-, Tl(1)-, and Cs-PVC membrane ion-selective electrodes (PVCMISEs), which have reflected the high selectivity of the bis(crown ether) compounds for the respective metal ions (1-5). The Na- and K-PVCMISEs which we had reported are based on bis(l2crown-4) with lipophilic aliphatic substituents and bis(benzo-15-crown-5) connecting with the pentyl chain, respectively. They are found to show excellent electrode properties, i.e., near-Nernstian response in a wide concentration range of calibration plots and stable emf in a wide p H range. The selectivity coefficients, kN& for Na-PVCMISE and kKNafor K-PVCMISE, are comparable to those of the glass and valinomycin-based ISEs, respectively. There are a lot of commercially available analytical instruments combined with ISEs such as Na- and K-ISEs (6), which are generally based on glass and valinomycin, respectively. In the clinical analysis of inorganic ions, flame photometric analysis (7) has been employed, by which one can measure the concentration of ion very accurately. However, ISE method has recently begun to be used in this field (8,9) because it is a rapid method for the analysis of inorganic ions and also because it needs no dangerous materials like highpressure propane gas in the flame photometric analysis. Although the PVCMISEs are very useful, they have many disadvantages, some of which are complex construction, high cost, and the necessity of a big sample solution volume. A most exciting advance in this area was made by Freiser et al., who has developed coated wire ion-selective electrodes (CWISEs) (IO). The electrodes were prepared by dipping the tip of metal wire in a solution of PVC and active substance, and allowing the resulting thin film to air-dry. The main advantages of CWISEs are simple construction and inexpensiveness compared to the conventional ISEs. They also have the big interesting advantage that they do not need any internal solution. The CWISEs which are responsive to Ca2+ (IO), K+ (11, 12),NO3- (13, 14), and quaternary ammonium ions (15) have been developed so far. In the present work, high-performance Na- and K-CWISEs were prepared with those bis(crown ether) compounds and compared with the conventional PVCMISEs. These CWISEs are also applied for simultaneous determination of Na+ and K+ in the artificial sample by means of Gran's plot method. 0003-2700/82/0354-1224$01.25/0
Table I. Preparation of Coating Solution A
B
coating solution C D E
F
G
I, mg 1 9 Q 20b 5c 11, mg 20d 10e 111, mg IV, mg 10f NPOE,mg 819 410 824 819 200 200 819 PVC,mg 402 200 400 403 101 101 401 3 3 6 THF,mL 6 3 6 6 a-f Content of the crown ether to the total weight of the coating solution (wt %): a, 1.5; b, 3.2; c, 0.41; d, 1.6; e, 3.1; f , 3.2.
EXPERIMENTAL SECTION Chemicals. Crown ether derivatives I-IV shown in Figure 1 were synthesized according to the methods which have been described elsewhere (1,2). The plasticizer, o-nitrophenyl octyl ether (NPOE),was prepared according to the procedure reported earlier (16). PVC (1100 of average polymerization degree) was purified by reprecipitation from tetrahydrofuran to methanol. The metal chloride employed was of analytical grade. Water was deionized and distilled. Construction of CWISE. CWISE constructed here is shown schematically in Figure 2. A silver wire of 0.4 mm 0.d. was carefully soldered to a shielded cable, and then it was incorporated with epoxy resin in a 8 mm 0.d. glass tube. The junction was covered with sealing tape in order to prevent its being wetted by the sample solution. The length of the exposed silver wire is about 5 mm. The exposed silver wire was rinsed with diluted "OB, carefully washed with distilled water, and then dried with acetone. It was immersed in the coating solution 10 times and the solvent was evaporated with a heat gun in each case. The coating solution was prepared by dissolving an appropriate amount of crown ether, plasticizer, and PVC in THF, as shown in Table I. The optimal content of crown ether to the total weight of the coating solution is about 1.5-3.2 wt %. Moreover, the junction of the coated region and taped area was also covered with the poly(cyanoacry1ate)resin so as to keep the exposure length of the coated region constant. Measurements. All measurements of emf were made at 25 f 0.1 "C using a Corning pH meter 130. Standard metal chloride solutions for calibration plots were obtained by gradual dilution of 1 M metal chloride solution. Selectivity coefficients for interfering ions, kMN, were determined by the mixed solution method (17). Response time and 0 1982 American Chemical Society
ANALYTICAL CHEMISTRY, VOL. 54, NO. 7, JUNE 1982
r-y h
CH2
CH2
1225
C5HllC02CH2~07
0
0
II
I
Flgure 3. Dependence of coating number (A) and composition of coating solution (B) on the emf of K-CWISE based on I. 111
IV
Flgure 1. Neutral carriers employed in this study.
centrations of Na+ and K+ in the artificial sample are given simply by
RESULTS AND DISCUSSION The electrode properties of crown ether-based ISE are in-
Figure 2. Construction of coated wire electrode: (A) epoxy resln, (6) shielded cable, (C) 8 m m a d . glass tube, (D) solderlng, (E) seal tape, (F) 0.4 m m 0.d. sillver wlre, (G) cyanoacrylate resin, (H) PVC matrix.
reproducibility wlere determined by the incremental method (18). Dependence of pH on the electrode response was examined by adjusting the pH of the measured solution with 1 M metal hydroxide and hydrochloric acid. Simultaneous determination of Na+ and K+ by means of Gran's plot method (19) was achieved by the measurement system, in which two CWISEs were immersed in the sample solution, which were connected to pH meters, respectively. The slopes for caland SK)were determined simultaneously by ibration plots (SNa a multiple standard addition method in which a standard solution (Na+ and K+ mixed solution) is added to the sample solution of lower concentration of the artificial sample three to five times, until the calibration curve covers the approximate concentration M; K+, (2-5) X range of the vital sample (Na+, (1-3) X M for urine; Na+, (1.3-1.5) X M; K+, (3-5) X lo4 M for serum, respectively). The emfs (ENaand EK) of the sample solution (V,) were recorded afkr each of several additions of a standard solution (CNa* and CK*). The standard solution should contain a hundredfold higher concentration of Na+ and K+ than the sample solution. The products (Vo + V*)lpN~/~N.and (Vo + V * ) l p K / S K are plotted against the total volume of added standard solution V*, and then the initial Concentration values of CN,, and CK are calculated from the intercepts ( VNa* and VK*) of the abscissa. They are obtained by applying Gran's plot method to the binary component system (NaS and K+), which are as follows CNa = [kNaKVK*(CK* + kKNaCNa*) - VNa*(CNa* + kNaKCK*)I/(l - kKNakNaK) VO CK
kKNaVNa*((:Na*
+ ~N&K*)
-
V K * ( ~ K+* kKNaCNa*)/(l - kKNakNaK)VO (A) The equations can be given in an abbreviated form because the selectivity coefficients ( k N G = lo-' and KKNa = l o 4 ) are so small that the term except C*V* can be neglected. Then initial con-
fluenced very much by the complexing ability of the crown ether with the ion, which were dependent considerably on the relative size of cavity of crown ether and ion (20). The ion extractability of crown ether is also affected by the structure of them in which poly- and bis(crown ether) are favorable for formation of 2:l (crown ether unit/ion) sandwich-type complexes with particular ions (21). Irrespective of higher extractability of poly(crown ether) than bis(crown ether), the electrode based on poly(crown ether) has been impractical so far due to the poor response to activity change of the ion and long response time (2). Therefore, two types of bistcrown ether) compounds were used as a neutral carrier of CWISEs, one is bis(l2-crown-4) with aliphatic substituents for NaCWISE and the other is bis(benzo-15-crown-5) with pentyl chain for K-CWISE:. The properties of' CWISEs were evaluated mainly by the slope and the linear range of the calibration plots and were dependent on the coating number and the composition of the coating solution. Figure 3 shows the dependence of the electrode response on the coating number (A) and the composition of the coating solution (B)in the K-CWISE system. The slope and the linear range of the calibration plots are increased with increasing coating number. In the case of the coating number 10, the slope and linear range of the calibration plots are 57 mV/decade and 1 f i l O - l M, respectively. Crown ether content in the coating solution also influences the electrode response. The calibration plots do not change in a crown ether content of the coating solution over 1.5 w t % . The optimal coating number and the crown ether content in the case of the Na-CWISE system were 10 and 3.2 wt %, respectively, which were examined in a similar manner to the K-CWISE system. The electrode properties and selectively coefficients of K-CWISEs in optimal conditions are given in Table 11,which are compared with the data for the previous K-PVCMISE based on I. The K-CWISE based on I shows a linear response with a near-Nernstian slope in the activity range of 10-4-10-1 M at 25 "C. The selectivity coefficient decreases in the order Cs+ Rb+ > NH4+> Na+, which may be anticipated from the solvent extraction data (22). The selectivity coefficient for sodium ion, kKNa, is close to that of the valinomycin-based electrode. The electrode of the monocyclic analogue I1 also showed a linear response with a slope of 50 mV/decade in the activity range 10-4--10-1M. However, in the selectivity
-
1226
ANALYTICAL CHEMISTRY, VOL. 54, NO. 7,JUNE 1982
Table 11. Electrode Properties of K-CWISEs I-NPOEa
11-NPOE
I-DPP
51 4-1 3 x 10-4 3 x lo-' 4 x 10-1 8 X 1O-j
50 4-2 2x 9x 1 1x
54 3-1 1 x 10-3 I x 10-1
maximal slope, mV decade-' pK range kKN
Kat
Rb' c s+ NH,' a o-Nitrophenyl octyl ether. brane based on I.
Dipentyl phthalate.
lo-$ lo-'
6X
1x
PVCMISE 58 5-1 3 x 10-4 2 x 10-1 1 x lo-' 1x
lo-'
Electrode body of Orion Model 92 was used with the PVC mem-
Table 111. Electrode Properties of Na-CWISEs 111-NPOE IV-NPOE PVCMISEa maximal slope, mVdecade-' pNa range kNaN
Li' Kt
Rb+
cs
+
NH,' Mgzt Caz+ Sr2+ Ba2+
53
55
53
4-1 1 x 10-3 1 x 10-2 1X 3X 6X 1 x 10-4 1 x 10-4 1 x 10-4 2 x 10-4
4-1
4-1 1 x 10-3 9 x 10-3 4X 1X 1X 1 x 10-4 1 x 10-4 2 x 10-4 2 x 10-4
4 x 10-1 8 X lo-' 8 X lo-' 5 X 10''
Electrode body of Orion Model 92 was used with the PVC membrane based on 111. a
coefficient for the sodium ion, kKNa,the electrode based on I is about 1order of magnitude smaller than that of 11, though the other selectivity coefficients are almost the same. This reflects our previous observation that I has high extractability for K+ compared to I1 because of the easy complexation of stable 2:l (crown ether unit/ion) sandwich-type complex, which is derived from the cooperative effect of two adjacent crown ether rings (21). The Na-CWISE based on bis(l2-crown-4) with an aliphatic substituent attached to the main chain I11 has excellent electrode properties, the selectivity coefficients being summarized in Table 111. The Na-CWISE based on I11 shows a linear response with a slope of 53 mV/decade in the activity range 10-4-10-1 M, which is also comparable to the NaPVCMISE. The selectivity coefficient decreases in the following order: Cs+ > Rb+ K+ > Li+ > M2+(alkaline earth metal ions). The selectivity coefficients of IV-based electrode are 1 to 2 orders of magnitude larger than those of the IIIbased electrode, although they are not very different in the electrode sensitivity. It may be due to the favorable structure of I11 for forming the stable 2:l complex with sodium ion in the PVC membrane phase. The selectivity coefficients for alkaline earth metal ions were also measured because these ions, especially Ca2+and Mg2+,generally coexist with sodium ion in the vital sample. These values are below 2 X so no interference would be observed on the determination of sodium ion in the vital sample. Response time was also investigated, which is a very important factor for practical use of the Na- and K-CWISEs based on I and 111, respectively. Response times (tQ5)of these electrodes were within 10 s by means of the incremental method (I@, such as Gran's plot or standard addition method. The emf of the Na- and K-CWISEs is influenced by pH of sample solutions more than those of PVCMISEs, which is remarkably at a higher p H region (1). The emf remains constant in the pH range 2 or 3 to 8 or 9 in the concentration range 10-1-10-6 M NaCl and KC1, respectively, which are illustrated in Figure 4. Though the measurements by these
0
2
8
6
4
1 0 1 2 1 4
PH
Flgure 4. Dependence of pH on emf of Na- and K-CWISEs. 140
r
4
120
-
>
-. E w
I
100
EK
80
I 0
?
f
t 1
2
4
6
t / rnin
Flgure 5. Emf-time proflle of Na- and K-CWISEs for the artificial urine: M; Ca2+,7.2 X lo-, M; Mg2+, Na', 1.29 X IO-* M; K+, 4.25 X 5.0 X lo-, M; (NH,),HPO,, 3.0 X lo-' M; urea, 2.0 X M; V , = 10 mL. Arrows Indicate the injection of standard solution whose cornpositlon Is as follows: Na', 1.30 M; K+, 4.30 X lo-' M; V' =
0.1 mL.
CWISEs may be subject to some error in a higher pH region than 8 or 9, the emf of CWISEs is not influenced on measurements of acidic or neutral sample solutions. Simultaneous determination of Na+ and K+ was carried out by means of Gran's plot method for the artificial urine and serum. Such concentration of Na+ and K+ as contained in
Anal. Chem. 1902, 5 4 , 1227-1229
illustrated in Figures 5 and 6. Dynamic responses of both CWISEs by the injection of additional solution are very fast. The emf can be read to a precision of 0.1 mV in both CWISEs because of their stable emf, which is important for Gran’s plot method as the term of (V, V*)1WS is exponentially proportional to the emf. The initial concentration of Na+ and K+ in the artificial sample can be obtained, if the intercepts (VN,* and V,*) are substituted in eq B. These results obtained by several measurements are given in Table IV, together with the standard deviation. The standard deviation values are very small, and the values of the relative error are within 4% for urine and 1%for serum in these measurements. Thus, it is safe to say that the CWISE system in this study allows one to determine the Na+ and K+ in the vital urine and serum samples, simultaneously and precisely.
P 3000
+
z
v1 \
m
2000
Za
--
*> +
9
1000
__
0
0.1
v*/
0.2
LITERATURE CITED
0.3
rnl
Figure 6. Gran’s plot in the simultaneous determination of Na+ and K+ for the artificial urine: S, = S, = 56 m V decade-’; 0, Na+; A, K+.
Table IV. Simultaneous Determination of Na+ and K’ in Artificial Samples Using Gran’s Plot Method arti eicial sample, Md urinee serumf
mean
* std dev,c Md
Na+ K+
1.29 X 4.25 x 10-3
1.35 X 10.’ ?r 4 X 4.33 x 10-3f 2 x
Na’
1.43 X lo-’ 5.10 x 1 0 - 4
1.42 X lo-’? 7 X BO-4b 5.14 x 1 0 - *~ 2 x 1 0 - ~ b
K+
1227
10-4a
a , b Mean of four and five replicate analyses, respectively. Standard deviation. M = mol L-’. e Ca’+, 7.2 X M; Mg2+,5.0 X M; (NH,),HPO,, 3.0 X M; urea, 2.0 x M. f Ca’+, 5.1 X M; Mg*+,1.6 x M; (NH,),HPO,, 4.7 X M ; urea, 3.0 X M; glucose, 1.0 X lO-’M. C
the samples do not interfere the K- and Na-CWISEs, respectively, because the selectivity coefficients, kKNa for the K-CWISE and k~~ for the Na-CWISE, are small enough. The sample solutions containing CaC12,MgCl,, (NH4)2HP04, urea, and glucose other than NaCl and KC1 were prepared by adjusting the concentration of them to one-tenth of that of vital urine and serum, because the calibration curve tends to level off over 10-1 M NaC1. A typical example of the emf-time profile and Gran’s plot for the artificial urine ar’e
(1) Shono, T.; Okahara, M.; Ikeda, I.; Kirnura, K.; Tamura, H. J . Electroanal. Chem. 1982, 132, 99-105. (2) Kimura, K.; Maeda, T.; Tamura, H.; Shono, T. J. Electroanal. Chern. 1979,95, 91-101. (3) Tamura, H.; Kirnura, K.; Shono, T. Bull. Chem. Soc. Jpn. 1980,53, 547-548. (4) Tamura, H.; Kimura K.; Shono, T. J. Nectroanal. Chem. 1980, 775, 115-121. (5) Kimura, K.; Tarnura, H.; Shono, T. J. Electroanal. Chem. W78, 705, 335-340. (6) Ladenson, J. H. J. Cab. Clln. Med. 1977, 90, 645-665. (7) Mayer, K. D. F.; Strarkey, B. J. Clin. Chem. (Wlnston-Salem, N.C.) 1977,23, 275-278. (8) Jenny, H.-B.; Riess, C.; Ammann, D.; Magyar, B.; Asper, R. R.; Simon, W. Mlkrochlm. Acta 1080,309-315. (9) Mangubat, E. A.; Hlnds, T. R.; Vincenzi, F. F. Clln. Chem. (WnstonSalem, N . C . ) 1978,2 4 , 635-639. (10) Cattrall, R. W.; Freleer, H. Anal. Chem. 1971,43, 1905-1906. (11) Cattrall, R. W.; Frelser, H. Anal. Chem. 1974,46, 2223-2224. (12) Carmack, G.; Freisur, H. Anal. Chem. 1977,49, 1577-1579. (13) Kneebone, B. M.; Freiser, H. Anal. Chem. 1973,45, 449-452. (14) Martln, C. R.; Freiser, H. J. Chem. Educ. lg80,57, 512-514. (15) Martln, C. R.; Freiser, H. Anal. Chem. 1980,5 2 , 562-564. (16) Hornlng, E. C. “Organic Syntheses”; Wiley: New York, 1955; Vol. 111, p 140. (17) Pungor, E.; Toth, K.; Pall, A. H. Pure Appl. Chem. 1977, 5 7 , 1913-1980. (18)Philips, Ion-Selective Electrodes“; Pye Unican Ltd.: Cambridge, 1981; p 18. (19) Gran, G. Analyst (London) 1952,7 7 , 661-671. (20) Truter, M. R. “Structure and Bonding”; Springer-Verlag: New York, 1973; Vol. XVI, p 71. (21) Kimura, K.; Tsuchida, T.; Shono, T. Talanta 1980,2 7 , 801-805. (22) Klmura, K.; Maeda, T.; Shono, T. Talanta 1979,2 6 , 945-949.
RECEIVEDfor review December 21,1981. Accepted March 2, 1982. The present work was partially supported by a Grant-in-Aid for Developmental Scientific Research from the Ministry of Education.
Reflectance Studies of the Tin( I I ) Diphenylcarbazide Solid Monitoring Reagent for Atmospheric: Oxidants Jack L. Lambert,” Mohammed H. Beyad, Joseph V. Baukstells, and Mlchael JI. Chejlava Department of Chefmishy,Kansas State University, Manhattan, Kansas 66506
Yuan C. Chlang Department of Chemistty, Kansas Wesleyan Universi@, Salina, Kansas 6740 I
Tin(I1) cliphenylcarbazide was recently reported as a sensitive, solid, dry reagent for ozone and nitrogen dioxide ( I ) , the atmospheric oxidants of greatest interest. We now report results obtained with a Perkin-Elmer Model 124 spectro0003-2700/82/0354-1227$01.25/0
photometer modified1 for reflectance measurements. Colorless bis(diphenylcarbazide)tin(II) is stable to oxidation by triplet oxygen when supported on cellulose or starch. On other supports, the reagent has limited shelf life. Exposure 0 1982 American Chemical doclety
