Kinetic Study of the Periodate-a-Amino Alcohol Reactions with a Perchlorate Ion Selective Electrode: Catalytic Effect and Determination of Manganese C. E. Efstathiou and T. P. Hadjiioannou* Laboratory of Analytical Chemistry, University of Athens, Athens, Greece
The reactions between periodate and a-amino alcohols are easily monitored using a perchlorate ion Selective electrode as a periodate sensor. Several periodate-a-amino alcohol reactions have been studied and rate proportionalityconstants have been determined. It was found that manganese(l1) ions catalyze strongly the periodate-triethanolamine reaction, especially in the presence of trinitriiotriacetic acid (NTA) acting as an activator. A method is described for the determination of manganese based on its aforementioned catalytic effect. Determination is accomplished by means of a variable-time kinetic procedure using potentiometric monitoring with the perchlorate ion selective electrode and measuring automatically the time required for the potentialto change by a preselected amount (10.0 mV). Microamountsof manganese in the range 0.2-2 pg were determined with relative errors of about 1 % and measurement times of about 15 to 100 s. The method has been successfully used to determine manganese in nonferrous alloys.
Periodate oxidation has been used to determine a-amino alcohols ( I , 2 ) . Hitherto, the kinetics of these periodate reactions has received scant attention in the literature (3, 4 ) . Recently it was reported that a perchlorate ion selective electrode responds quantitatively to periodate and the application of the electrode to the potentiometric determination of vicinal glycols was described ( 5 ) .This work has further been extended to include the application of the perchlorate electrode to monitor other periodate reactions (6, 7). In this paper, it is demonstrated that periodate oxidation of a-amino alcohols can be easily monitored using the perchlorate ion selective electrode as a periodate sensor and rate proportionality constants for the reaction of periodate with several a-amino alcohols are reported. Also, a kinetic potentiometric method for the determination of microgram amounts of manganese is presented. It was found that manganese(I1) catalyzes the periodate-triethanolamine reaction, especially in the presence of trinitrilotriacetic acid (NTA) which acts as an activator, and the method is based on this reaction. The periodate-triethanolamine reaction is monitored with a perchlorate ion selective electrode, and the time required for the potential to change by a preselected amount (10.0 mV) is measured automatically with a solid state “double switching” network and related directly to the manganese concentration. Microamounts of manganese in the range 0.2-2 pg were determined with relative errors of about 1%and measurement times of about 15 to 100 s. The method has been applied successfully to the determination of manganese in nonferrous alloys.
GENERAL CONSIDERATIONS Basic considerations concerning electrode storage, conditioning, and deterioration symptoms are similar to those previously reported (5, 6). a-Amino Alcohols-Periodate Reaction Kinetics. The 414
ANALYTICAL CHEMISTRY, VOL. 49, NO. 3, MARCH 1977
perchlorate ion selective electrode (Orion Model 92-81) employed in this study exhibits Nernst potential behavior for periodate at concentrations 10-1 to M in accordance with Equation 1: = E’
E
RT F
- a -In [I04-]
(1)
where E is the measured total potential of the system, E’ is the portion of the total potential due to choice of reference electrodes and internal solution, R and F are the ideal gas and Faraday constants, respectively, T is the absolute temperature, and a is an experimentally determined parameter, the Slope Normalization Factor, dependent on electrode age and p H ( 6 ) ,which in the pH range of 4 to 7.5 is usually equal to 1 f 0.05. When dilute periodate solutions (-loT4 M NaI04) react with an excess (at least tenfold) of an a-amino alcohol, there is a good approach to an overall reaction according to the following scheme:
104-
+B
k
103-
+ product
(2)
where B is the free (nonprotonated) a-amino alcohol and h is the rate proportionality constant. Under controlled experimental conditions (at least tenfold excess of a-amino alcohol over periodate, p H constant in the range 5-7), the kinetics of the reaction is expressed by Equation 3:
-d[104-1 - - k [IO4-] [B] dt For the acid-base equilibrium BH+
K,
+
‘B1 = [H+] K,
K,,
B
(3)
+ H + we have:
CB
(4)
where CB is the analytical concentration of a-amino alcohol. Differentiating Equation 1,combining the resulting equation with the one obtained substituting B (Equation 4) in Equation 3, substituting the term d E l d t with the term AElAt, rearranging, and solving for k , gives:
k=-
F [H+] + K,, AE aRTCB K, At
(5)
Catalytic Effect of Manganese(I1) on the PeriodateTriethanolamine Reaction. Trace amounts of manganese(I1) catalyze the periodate-triethanolamine (TEA) reaction. Overall kinetics of the catalyzed reaction is described by Equation 6:
-d[104-1 dt
- - k [I04-][TEA] - k,[I04-] [TEA][Mn]
(6)
where [TEA] is the concentration of the free (nonprotonated) triethanolamine and k , is the rate proportionality constant of manganese. We have
[TEA] =
K, CTEA [ H + I +K ,
I
(7)
where CTEAis the analytical concentration of triethanolamine. Differentiating Equation 1,combining the resulting equation with the one obtained substituting TEA (Equation 7) in Equation 6, substituting the term dE/dt with the term AE/At, rearranging and solving for k c , gives:
,142ppm
Mn
114ppm Mn
I
,
085ppmMn
i
rr
w ‘
-x)sect-
where (AE/At), and (AE/At), are the measured slopes of the reaction curves of the catalyzed and uncatalyzed reaction, respectively. Figure 1 shows typical recorded curves for the periodatetriethanolamine reaction in the presence of various amounts of manganese. The rate proportionality constant k , can be calculated from the slopes of these curves using Equation 8. Effect of Ligands on the Manganese Catalytic Action on the Periodate-Triethanolamine Reaction. The action of catalysts can often be modified in the presence of ligands (8). Several ligands were tested’and some of them appeared to activate the catalytic effect of manganese on the periodate-triethanolamine reaction. On the other hand, several ligands mask completely the manganese, thus decreasing or eliminating completely its catalytic effect. Catalytic Determination of Manganese. The increase of the catalytic action of manganese on the periodatetriethanolamine reaction in the presence of NTA was utilized in the developed kinetic method for the determination of manganese, In this method, the reaction of periodate with a large excess of triethanolamine (more than 10 times) in the presence of NTA is monitored with a perchlorate ion selective electrode and the time required for the potential to cross two preset threshold values in a solid state “double switching” network is measured automatically and related directly to the manganese concentration.
EXPERIMENTAL Instrumentation. Electrodes and Reaction Cell. The same as previously reported ( 5 ) . Recording S y s t e m . A Heath-Schlumberger EU-205B Recording System is used which consists of the EU-205-11 multispeed recorder mainframe, the EU-200-01 Potentiometric Amplifier Module, and the EU-200-02 Offset Module. The EU-200-30 pH/pIon electrometer is inserted between the electrodes and the recorder for impedance matching. Measurement and Control System. A solid state double switching network (7), an improved version of the one used previously ( 5 ) ,in conjunction with the recording system was used for automatic time measurements. For the present work, this system is adjusted to be activated after a premeasurement period needed for a potential change of about 25-30 mV and then to measure accurately ( f O . O 1 s) the time required for the cell voltage to change by 10.0 mV. Reagents. All solutions were prepare‘d with deionized doubledistilled water from reagent-grade materials. S o d i u m Sulfate was 0.20 M. Acetate Buffers, p H 4.0 and 5,0, were prepared by appropriate mixing of 5 M NaOH solution and 0.2 M and 0.5 M CH:jCOOH, respectively. Sodium Metaperiodate. (a) Stock solution I, 0.050 M. Dissolve 10.7 g of NaI04 (G. F. Smith Co., Columbus, Ohio) in water and dilute to 11. (b) Mixed solution II,3.0 X M NaI04-3.68 X lo-’ M NaZS04. Mix 3.00 ml of solution I and 92 ml of sodium sulfate 0.20 M and dilute to 500 ml. Prepare fresh daily. (c) Working solutions I11 and IV, 1.00 X M and 3.0 X M. Prepare fresh daily from solution I by dilution. All periodate solutions are kept in amber bottles. a-Amino Alcohols. (a) Stock solutions I, 1.000 M of ethanolamine, diethanolamine, and triethanolamine (Fluka, puriss, 99%).The exact titer was determined potentiometrically by titrating with HCl 1.000 M. (b) Working solutions 11,O.lOOOM, pH 3.6. Dilute 10.00 ml of solution I with 50 ml of water, adjust the pH to 3.6 with 1 M H3P04 and
Flgure 1. Recot‘ded curves of cell voltage vs. time for periodatetriethanolamine reaction in the presence of Mn(ll)
Initial concentrations:Na104, 2.7 X M; triethanolamine, 9.05 X M; Mn, 5.17 X 10-6-2.59 X M (0.28-1.42 ppm Mn), pH 6.84. Ionic strength adjusted with Na2S04at 0.1. Temperature 25 O C (l:(a)triethanolamine addition; (b) manganese injection) dilute to 100.0 ml. (c) Triethanolamine solution 111, 0.1000 M, pH 6.80. Dilute 10.00 ml of solution I with 4.00 ml of 1 M H3P04 and 60 ml of water, adjust the pH to 6.80 with 5 M NaOH and dilute to 100.0 ml. (d) Composite 0.150 M triethanolamine-0.020 M NTA-0.20 M phosphate buffer solution IV, pH 6.80. (e) Solutions V, 0.100 M, pH 6.00. Fourteen a-amino alcohols were used (Figure 4). Dissolve the required amount of a-amino alcohol in 10 ml of 1M H3P04and 60 ml of water, adiust the pH to 6.00 with 5 M NaOH (about 0.2-0.3 ml) and dilute to 100ml. M.The ligands used were: 1)NiLigands Solutions, 1.00 X trilotriacetic acid (NTA) 2) ethvlenediaminetetraacetic acid (EDTA), 3) ethyleneglycol-bis(2-aminoethy1ether)tetraaceticacid (EGTA), 4) 1,2-diaminocyclohexanetetraaceticacid (DCTA), 5) diethylenetriaminepentaacetic acid (DTPA), 6) triethylenetetraminehexaacetic acid (TTHA), 7) 1,lO-phenanthroline, 8) 3,4,7,8-tetramethyl-1,10phenanthroline, and 9) 2,2’-bipyridyl. Dissolve the required amount of ligand in the minimum amount of 0.1 M NaOH (ligands 1-6) or 0.1 M HC1 (ligands 7-9), adjust the pH to 5.0 with 1 M CHsCOOH or 1 M CH3COONa and dilute to 100 ml. Nitrilotriacetic Acid. Stock Solution 0.100 M . Add 1.914 g of NTA doubly recrystallized from hot water in 60 ml of water, stir vigorously, add slowly 5 M NaOH to keep the pH in the range of 6-7 till NTA is dissolved and dilute to 100 ml. Prepare 0.0100 M and 0.00100 M solutions from the stock solution by dilution. Manganese Stock Solution, 2,000 p p m . Prepare by dissolving reagent grade manganese (>99.9%) in dilute HC1 or from any manganese(I1) salt of known purity. Prepare standards containing 50,250, and 550 ppm of manganese and working standards containing 0.1-1 ppm of manganese from the stock solution by dilution. Procedure. Determination of Rate Proportionality Constants. Into the thermostated cell kept a t 25 O C , pipet 15.00 ml of mixed soM, and 2.00 ml of lution 11, NaI04 3.0 X M-Na2S04 3.58 X 0.1000 M a-amino alcohol working solution 11. Set the recorder span a t 50 mV, start the recorder and initiate the reaction by raising the pH from about 3.8 (the pH of the mixture in the cell) to 5.5-6.9 by instantaneously injecting small volumes (2-20 pl) of 5 N NaOH solution into the cell. Record a large portion of the linear part of the reaction curve or until the recording becomes noisy, and measure the final pH of the solution with an accuracy of f O . O 1 pH unit. Preparation of Nonferrous Alloys Samples. Dissolve an accurately weighed sample of about 0.04 g of nonferrous alloy with 10 ml of 1:l HC1 or HNO:j. Heat on a waterbath to expel the excess acid and dilute to 500 ml. Catalytic Determination ofMunganese(Z1). Pipet 15.00 ml of 3.00 X loT4M sodium metaperiodate solution and 3.00 ml of the composite triethanolamine-NTA-buffer solution into the reaction cell thermostated a t 25 “C. Start the stirrer, quickly adjust the recorder pen on the right side of the chart, and after about 20 s (during this time interval the potential increases by about 2.5 mV because of the uncatalyzed reaction) press the Start button of the Universal Digital Instrument (at the “events counter” mode) and quickly pipet 2.00 ml of standard or sample manganese(I1) solution into the reaction cell. When the potential crosses the first preset potential value, time counting starts automatically and stops when the potential crosses the second preset value. Record the number on the digital readout (time in hundredths of a second), press the Reset button, empty the cell with suction, rinse the electrodes, and the cell with water and dry them with suction. Repeat the procedure for each analysis. ANALYTICAL CHEMISTRY, VOL. 49, NO. 3, MARCH 1977
415
Table I. Rate Proportionality Constants for the Reaction of Periodate with a-Amino Alcohols (at 25 " C ,/L = 0.1) a-Amino alcohol
Kfl a
HzNCHzCHzOH
1.82 x
HN(CHzCHzOH)2
7.59 x
N(CHzCHzOH)3
pH f 0.01
Ub
5.60 5.94 6.23 6.38 6.75 6.83 5.58 5.86 6.16 6.41 6.60 6.81 6.49 6.68 6.84
1.021 1.016 1.014 1.012 1.007
10-10
8.32 x 10-9
1.005
1.022 1.018 1.015
1.012 1.010 1.005 1.011
1.008 1:005
AElAt, mV/s
kc (M-k-l)
0.038 0.094 0.182 0.261 0.535 0.800 0.055 0.099 0.190 0.351 0.534 0.875 0.010
2210 2510 2490 2530 2220 2770 795 755 730 760 750 760 1.70
0.014 0.016
1.25
1.55
a K , values have been determined at the same temperature and ionic strength (12). a values were determined from an a vs. pH plot, constructed on the basis of the following experimentally determined a values, obtained the same day of the kinetic study,_atthe same temperature and ionic strength: pH 5.65, a = 1.021; pH 6.30, a = 1.013; pH 6.65, a 1.009; pH 6.90, a = 1.004. Average, h f S k (M-h-l): a) (2.5 f 0.2) X lo3for HzNCHzCHzOH; reported value ( 4 ) for k is (4.6 f 0.2) X lo3, at 25 "C, but at p = 0.2 and for K , = 3.20 X 10-10. b) (7.6 f 0.2) X lo2 for "(CH~CHZOH)~,and c) 1.5 f 0.2 for N(CHzCH20H)3.
Table 11. Results for the Determination of Mn(I1) in Aqueous Solutions
'' 1
Manganese, pg12 ml
'T ?
Reciprocal time, s-l x 103
Taken
Founda
12.90 18.42 23.35 32.44 43.50 52.99
0.300 0.500 0.700 1.000 1.400 1.800
0.301
+0.3
0.505
+LO
0.686 1.021 1.428 1.777
-2.0 +2.1 +2.0 -1.3 Av 1.4
1 --MsOC-
t-
Figure 2. Effect of various ligands o n the catalytic effect of manganese on the periodate-triethanolamine reaction Initial concentrations: Na104, 3.6 X M; triethanolamine, 1.07 X M; ligand, 3.6 X M; manganese, 3.56 X IO+ M (1.96 pprn), except for curve 1 where no manganese is added, pH 5.0, total acetate 0.084 M. (1) Uncatalyzed reaction and catalyzed reaction in presence of EDTA or DCTA or DTPA or TTHA. (2) Catalyzed reaction. (3-7) Catalyzed reaction in the presence of (3) a , d dipyridyi; (4) 3,4,7,8-tetramethyl-l,IO-phenanthroline; (5) NTA; (6) 1,10-phenanthroline, and (7)EGTA. Temperature 25 "C (1:(a), triethanolamine addition; (b) manganese injection)
RESULTS AND DISCUSSION Rate proportionality constants for the reaction of periodate with ethanolamine, diethanolamine, and triethanolamine calculated using Equation 5, from the slopes of recorded reaction curves obtained at various pH values, are given in Table I, together with all measured parameters. For the determination of the rate proportionality constant of manganese, k,, the periodate-triethanolamine reaction was initiated by injecting various amounts (25-150 pl) of 250 ppm standard manganese solution. From the slopes of recorded curves (Figure 1) using Equation 8, the value of k , was found equal to (3.5 f 0.2) X lo5 M-2 s-l. T o investigate the effect of various ligands on the catalytic. effect of manganese(I1) on the periodate-triethanolamine reaction, the following procedure was used: 10.00 ml of 1.00 X loW3 M NaI04, 10.00 ml of 1.00 X M ligand and 5.00 ml of acetate buffer pH 5.0 were pipetted into the reaction cell, 416
ANALYTICAL CHEMISTRY, VOL. 49, NO. 3, MARCH 1977
Error, %
Single measurements. Calculated using equation: 10001At + 54.34 [Mn],,,. Correlation coefficient was 0.9999.
= 4.71
the recorder was started, 3.00 ml of 0.1000 M triethanolamine solution pH 3.6 were pipetted into the cell and the reaction was initiated by instantaneously injecting 0.100 ml of 550 ppm standard manganese solution. Recorded curves are shown in Figure 2. I t can be seen from Figure 2 that EDTA, DCTA, DTPA, and TTHA act as inhibitors, masking completely the catalyst, whereas NTA, the phenanthrolines, and EGTA activate strongly the catalytic effect of manganese. I t is of interest to note that of all ligands tested NTA, the phenanthrolines, and EGTA are the only ones which enhance the catalytic effect of manganese. These findings parallel earlier observations of Mottola with the Malachite green-periodate reaction (9,lO). NTA was chosen for the kinetic method for the determination of manganese, because it gave the most reproducible results and because of its lower cost. T o study the effect of NTA concentration on the manganese catalytic action on the periodate-triethanolamine reaction, the procedure for the determination of rate proportionality constants was modified as follows. After pipetting the mixed NaI04-NazS04 solution I1 into the reaction cell, 30 or 100 pl of NTA solution were injected into the cell, triethanolamine solution I11 was added, and the reaction was initiated by instantaneously injecting 25 pl of 250 ppm standard manganese solution. Recorded curves are shown in Figure 3. The reaction
[NTA]
I
'
452$104M lj5x:04M
//
21 8 M 4
ut
NTA
t-
Flgure 3. Effect of variation of concentration of NTA on rate of the manganese catalyzed periodate-triethanolamine reaction Initial concentrations: Na104, 2.7 X addition: (b) manganese injection)
I
M; triethanolamine, 9.07 X
HNCHCHW 2 2 2
H2NCH2CH(DH)CH3
M;NTA, 1.35 X 10-6-4.52 X
CHCH(NH)CI(W 2 5 2 2
M, pH 6.80. Temperature 25 O C
HNaCH 1 C H W 2 32 2
(4:(a),triethanolamine
C"3NHCH2CH20"
U
-3'
3
t-
Figure 4. Catalytic action of manganese alone and in the presence of NTA on the rate of the reaction of periodate with various a-amino
alcohols Initial concentrations: NaO l ., 2.5 X M;a-amino alcohol, 8.3 X M (0.21 ppm); NTA, 8.3 X M (if present), pH 6.20 rt 0.05, M; Mn, 3.8 X total phosphate 0.0083 M. Temperature 25 O C . Symbols: (-) uncatalyzed reaction; (- - - -) catalyzed reaction: (. . . . . .) catalyzed reaction in presence of NTA (a) a-amino alcohol addition; (b) manganese injection)
(4:
rate shows a dependence on NTA concentration for which the order is about 0.4. To investigate comparatively the effect of manganese(I1) ions on the reaction of periodate with various a-amino alcohols in the absence and the presence of NTA, the procedure for the determination of rate proportionality constants was modified as follows. After pipetting the mixed NaI04-Na~S04solution I1 into the reaction cell, 2.00 ml of water were added into the cell, the recorder was started, 2.00 ml of a-amino alcohol solution V were added and after 30 s the reaction was initiated by instantaneously injecting 0.100 ml of 50 ppm standard manganese solution. The same procedure but without adding manganese was used to study the uncatalyzed reaction. For the study of the effect of NTA, 2.00 ml of 0.100 M NTA solution were used instead of water. Recorded curves are shown in Figure 4. The slopes of the curves refer to a pH of 6.20 f 0.05. Differences in slopes for the reactions of periodate with
various a-amino alcohols do not indicate similar differences in rate proportionality constants because of the different basicity of the various a-amino alcohols and consequently of the different concentration of free (nonprotonated) base present in each case at the pH used. There is an induction period for some of the a-amino alcohols tested. A similar effect has been observed on the manganese-catalyzed periodate-Malachite Green cation reaction (11).The combined action of Mn(I1) ion and NTA on these periodate-a-amino alcohols reactions may be of practical importance for the iodometric determination of certain aamino alcohols, for which the periodata-a-amino alcohol reaction step in the iodometric procedure fails because of a very slow and incomplete reaction, especially for a-amino alcohols containing tertiary amine groups. Recorded curves for the periodate-triethanolamine reaction in the presence of manganese(I1) and NTA are shown in FigANALYTICAL CHEMISTRY, VOL. 49, NO. 3, MARCH 1977
*
417
t-
Figure 5. Recorded curves of cell voltage vs. time for periodatetriethanolamine reaction in presence of Mn and NTA. Initial manganese
concentration, 0-1 ppm; other conditions as under procedure (4:sample addition) ure 5. Working curves (reciprocal time vs. concentration) were determined by least-squares fit. Usually three manganese standards (0.1, 0.5, and 1.0 ppm) are run in duplicate. The regression equation of such a calibration plot (lOOO/At,s-l X lo3vs. manganese(I1) concentration in ppm) was lOOO/At = 4.71 54.34 [Mn]. Analysis of aqueous manganese solutions of known concentrations gave the results shown in Table 11. The data indicate that microgram amounts of manganese in the range of 0.3 to 1.8 yg in a total volume of 25 ml can be determined with relative errors of 1 to 2%. Nine replicate determinations were made with a 0.5 ppm Mn sample. The average measurement time was 31.79 s (range = 0.49 s) and the relative standard deviation was 0.63%. The following cations in the stated within parentheses ratio
+
of added cation concentration to manganese concentration caused a relative error of less than 5% in the manganese determination: Co2+ and Cr3+ (8);Fe3+ (40); Mg2+,A13+,Zn2+, Cu2+, Ni2+,and Pb2+ (loo), and Ca2+ (200). The kinetic method was tested for the determination of manganese in nonferrous alloys. Satisfactory results were obtained in the analysis of National Bureau of Standards bronze 62 (Mn%: found 1.57, 1.58; reported 1.59) and Thorn Smith Dow metal 4 (Mn%: found 0.54,0.51; reported 0.52). Although the application reported here deals with the catalytic determination only of manganese, the scope of the method is intended to be more general. The rapid response of the perchlorate electrode to changes in periodate concentrations makes i t a valuable sensor for following the rate of periodate redox reactions. There are probably other applications in the field of catalytic analysis, where many normally slow reactions involving periodate can be catalyzed by trace amounts of various metal ions.
ACKNOWLEDGMENT The authors are grateful to G. Tsoutsoura for valuable assistance.
LITERATURE CITED (1) G. Dryhurst, "Periodate Oxidation of Diol and Other Functional Groups", Pergamon Press, London, 1970, p 116. (2) A. Besada and Y. A. Gawargious, Talanfa, 21, 1247 (1974). (3) G. E. McCasland and D. A . Smith, J. Am. Chern. Soc., 73, 5164 (1951). (4) G. Dahlgren and J. M. Hedsdon, J. Phys. Chem., 68, 416 (1964). (5) C. Efstathiou and T. P. Hadjiioannou, Anal. Chem., 47, 864 (1975). (6) C. Efstathiou and T. P. Hadjiioannou, Anal. Chem., 49, 410 (1977). (7) C.E. Efstathiou and T. P. Hadjiioannou, Anal. Chim. Acta, in press. (8) H. A. Mottola and G. L. Heath, Anal. Chem., 44, 2322 (1972). (9) H. A. Mottola, Anal. Chem., 42, 630 (1970). (10) H. A. Mottola, Anal. Chim. Acta, 71, 443 (1974). (11) H. A. Mottola and C. R. Harrison, Talanta, 18, 683 (1971). (12) G. Douheret, Bull. SOC.Chirn. Ff., 2915 (1965).
RECEIVEDfor review August 13, 1976. Accepted November 17, 1976. This research was supported in part by a research grant from the Greek National Institute of Research.
Preparation and Analytical Applications of a Propylenediaminetetraacetic Acid Resin Elizabeth M. Moyers and James S. Fritz* Ames Laboratory-ERDA and Department of Chemistry, Iowa State University, Ames, Iowa 500 1 1
A new chelating resin has been synthesized that contains a propylenediaminetetraacetic acid functional group which is attached to a carboxyllc acid divinylbenzeneresin via an esterification reaction. The new resin retains polyvalent metal cations at pH 3 or higher. It retains copper(ll), uranium(Vl), thorium(lV), and zirconium(1V) from more acidic solutions. A scheme is given for clean, rapid chromatographicseparatlon of the last three elements from each other. The resin is also able to retain quantitatively a number of trace elements from simulated sea water.
The Dow A-1 chelating resin (also sold as Chelex 100) contains an iminodiacetic acid functional group. I t has a number of analytical applications but its use in columns is often difficult because of extreme swelling or shrinking as the resin is converted from one form to another. Hirsch et al. ( 1 ) 418
ANALYTICAL CHEMISTRY, VOL. 49, NO. 3, MARCH 1977
prepared a macroporous resin containing a n iminodiacetic acid group that undergoes very little swelling. Rohm and Haas markets an iminodiacetic acid resin (XE-384) that undergoes only moderate swelling. Diaminetetraacetic acids form stronger complexes with metal ions than does iminodiacetic acid; also the former reacts with metal ions in a 1 to 1mol ratio. Thus a resin containing a diaminepolyacetic acid functional group should chelate and retain metal ions more strongly than a resin containing a n iminodiacetic acid function. Blasius and Olbrich (2) condensed m -phenylenedinitrilotetraacetic acid with resorcinol and formaldehyde to make a resin containing two iminodiacetic acid functional groups per benzene ring. They used the resin to separate cobalt(I1) and nickel(I1) on a gravity flow column. Blasius and Bock ( 3 ) synthesized a resin containing a N,N,N'- ethylenediaminetriacetic acid group. The resin was made by reacting ethylenediamine with a chloromethylated resin and then carbox-
