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Anal. Chem. 1985, 57, 2965-2971
63Niin CRUD, showing that the present method can safely be applied to the analysis of 55Fe. The method has been further applied (19) to determine specific activity of 55Fe existing as hematite and magnetite in CRUD collected from JMTR (Japan Materials Testing Reactor) OWL-1 loop. The hematite and magnetite in the sample were separated by fractional dissolution (20) with 0.1% of oxalic acid (80 “C) and with concentrated hydrochloric acid. The results show that the specific activity of the 55Fewas 39.6 f 0.2 MBq/g Fe for the hematite fraction and 22.0 f 0.4 for magnetite; the former was about 1.8 times higher than that of the latter, indicating hematite having a longer residence time in the reactor core than magnetite. This is attached to a preferable conversion of magnetite to hematite under an oxidative circumstances in the core (21). Since the extract consists of perchlorate ion and organic compounds such as BPT and xylene, care must be taken in discarding the waste extract. Combustion under frame can be one of the safest processings.
ACKNOWLEDGMENT The authors wish to acknowledge K. Sekine and €3. Amano for their assistance in measurement of X-ray spectra and liquid scintillation of 55Fe. LITERATURE CITED (1) Wellnsky, I.H. “Corrosion, Transport and Fouling in Water Cooled Reactors”; WAPD-C-200, 1955. (2) Robertson, R. F. S. “Chalk River Experience in CRUD Deposition Problems”; AECL-1328, 1961. (3) Brodsky, A. B., Ed. “CRC Handbook of Radiation Measurement and Protection”: CRC Press: Boca Ratan, FL, 1978; Sec. A, Vol. I,p 281.
(4) Wagner, A. Int. J . Appl. Radiat. Isof. 1973, 24, 548-550. (5) Sutton, G. A.; Harvey, B. R. “Liquid Scintillation Counting”; Crook, M. A,, Johnson, P., Ed.; Heyden: London, 1973; Vol. 3, pp 279-286. (6) Kojima, S.;Furukawa, M. Radioisotopes 1985, 34, 72-77. (7) Eakins, J. D.; Brown, D. A. Int. J . Appl. Radiat. Isot. 1966, 17, 39 1-397. (8) Cosolito, F. J.; Cohen, N.; Petrow, H. G. Anal. Chern. 1968, 4 0 ,
- .- - .- . 3 13-31s
(9) Yonezawa, C.; Sagawa, C.; Hoshl, M.; Tachlkawa, E. J . Radioanal. Chem. 1983. 78. 7-14. (IO) SAth, G.F.; McCurdy, W. H., Jr.; Diehl, H. Analyst (London) 1952, 77, 418-422. (11) Kraus, K. A,; Moore, G. E. J . A m . Chem. SOC. 1953, 75, 1460- 1462. (12) Fukasawa, T.; Yamane, T.; Shimada, S.Kobunshi Kagaku 1972, 29, 435-438 (in Japanese). (13) Toita, Y.; Onishi, H. Bunseki Kagaku 1975, 201-203 (in Japanese). (14) Ishikawa, H. “Measurement Method for Liquid Scintillation”; Nanzando Co.: Tokyo, 1981; pp 16-19 (in Japanese). (15) Nakashima, F.; Sakai, K. EunsekiKagaku 1961, 10, 94-98 (in Japanese). (18) Ishikawa, H. “Measurement Method for Liquid Scintillation”; Nanzando Co.: Tokyo, 1981; pp 13-14 (in Japanese). (17) Packard, “Operation Manual”; Packard Instrument Co., Inc., 1982. (18) SillBn, L. G. “Stability Constqnts”; The Chemical Society: London, 1971; Supplement No.1, Special Publication 25, p 625. (19) Yonezawa, C.; Hoshi, M.; Tachikawa. E., unpublished work, Japan Atomic Energy Research Institute, 1984. (20) Henmi, Y.; Yamatsugi, H.; Suganuma, T. Presented at the 18th Annual Meeting of the Atomic Energy Society of Japan, Nagoya, Japan, Mar 27-29, 1980; p 97. (21) Hoshi, M.; Tachlkawa, E.; Suwa, T.; Sagawa, C.; Yonezawa, C.; AoyaYamamoto, K., unpublished work, Japan Atomic Energy Rema, I.; search Institute, 1983.
RECEIVED for review May 28, 1985. Accepted July 18, 1985. This work was presented at the 27th Symposium on Radiochemistry, Nagoya, Oct 1983, and at the 28th Symposium on Radiochemistry, Kobe, Oct 1984.
Karl Fischer Titrations of Aldehydes and Ketones Eugen Scholz
Riedel-de Haen AG, 0-3016 Seelze, West Germany
Aldehydes and ketones react with the Karl Fischer reagent formlng acetals or ketals and water. The rate of water formation depends on both the reagent used and the carbonyl compound to be analyzed. Pyridine-based one-component reagents, whlch are commonly used, react most rapidly. Water formation rates have been determined for 44 lndlvldual aldehydes and ketones. The addillon of bisulfite Is a second side reaction that binds water. Therefore the results found are too low, especlally when nonalcoholic solvents are used. Some alcohols have been tested and halogenated alcohols are recommended as suitable solvents.
On the basis of recent studies ( I ) , the Karl Fischer reaction has to be expressed by new reaction equations (eq 1 and 2). The Karl Fischer reagent contains the salt of the alkyl sulfurous acid (eq l),which is oxidized during the titration step (eq 2) by the iodine. This reaction consumes water. Thus the presence of a suitable alcohol is a prerequisite for the K F titration.
ROH
+ SO2 + R’N + [R’NH]SO3R 0003-2700/85/0357-2965$01.50/0
H2O + 1 2 + [R’NH]S03R + 2R’N [R’NHISOIR -+
+ 2[R’NH]I
(2)
When water is determined in aldehydes and ketones, the presence of an alcohol is a disadvantage as it can react with the sample to form acetals and ketals according to eq 3 and 4. The water formed by these side reactions is titrated simultaneously, thus producing vanishing end points and erroneously high results. In some cases no end point is reached and a water determination is not possible. There are a
number of empirical methods to reduce the interferences caused by carbonyl compounds. Preferably methanol is replaced by other solvents in order to eliminate one reactive component from the system given by eq 3 and 4. Eberius (2) recommends pyridine as the working medium (sample solvent) and a KF reagent based on methanol, so that the actual KF 0 1985 American Chemical Society
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ANALYTICAL CHEMISTRY, VOL. 57, NO. 14, DECEMBER 1985
titration is carried out in a mixture of pyridine and methanol whose composition is continually changing during the titration. Fischer and Schiene (3) used 2-methoxyethanol in the K F reagent. A commercially available reagent employs 2-methoxyethanol in the K F reagent and as the sample solvent. In a similar manner, Klimova, Sherman, and L’vov tried to use dimethylformamide ( 4 ) . Mitsubishi (5)uses propylene carbonate as the solvent component in their KF reagent. These methods are not fully described and their practical application does not appear to be without its problems. The choice of the solvent very often appears to be arbitrary, as the reason for doing so is not mentioned. The suitability of the solvent is very rarely tested. Achieving a stable end point is often the sole criterion for the choice of the solvent. Recovery rates for water have never been published. Therefore it seemed useful to investigate the influence of the solvent more closely. The K F titration can be carried out using different types of reagents: one-component reagents or two-component reagents that can contain different amines. It is thus to be expected that different reagents behave differently. We therefore prepared five reagents, which we chose as being representative of the complete range of KF solutions. Water content in acetone and benzaldehyde was then determined using these reagents. Only generalized information covering the behavior of ketones and aldehydes is to be found in the literature (6). Aldehydes are more reactive than ketones, and several ketones, for example, dibutyl ketone or benzophenone, are designated as being stable. It therefore appeared appropriate to us to investigate the behavior of a few aldehydes and ketones more closely and to determine their rate of water formation during a K F titration. The bisulfite addition is a second source of error in the determination of water. It is rather underestimated and only seldom mentioned in the literature (1). It is also difficult to acertain because it is mostly masked by a strong acetal or ketal formation with the methanol. If however the working technique is changed and the methanol is completely replaced by other organic solvents, the bisulfite addition can be more clearly recognized.
41 la
2
L Lkl+L- L5
5
5
5 m g H,O
Figure 1. Titration of 5 mg of water using reagents 1 to 5. Curves a to e are for reagents 1 to 5.
5
5
5
5
rng HzO
Figure 2. Titration of 5 mg of water in the presence of 1 mL of acetone using reagents 1 to 5.
EXPERIMENTAL SECTION Reagent 1. A one-component reagent representing the standard KF reagent containing pyridine (3.2 mol/L), sulfur dioxide (1.5 mol/L), and iodine (0.35 mol/L) dissolved in 2methoxyethanol (available from Riedel-de Haen, catalog no. 36115). Reagent 2. A similar one-component reagent which, in compliance with U.S. Patent 4 378 972, contains imidazole instead of pyridine (available from Riedel-de Haen, catalog no. 34805). Reagent 3. A two-component reagent based on pyridine. The solvent component contains pyridine (3 mol/L) and sulfur dioxide (0.7 mol/L) dissolved in methanol. The titrant component is a solution of iodine in xylene with a water equivalent of 10 mg/mL. (We decided to use xylene as it is compatible with all solvent components and does not affect the KF reaction at low concentrations.) Reagent 4. A two-component reagent based on diethanolamine. The concentrations of the solvent component are analogous to reagent 3. Reagent 5. A two-component reagent based on imidazole according to U.S. Patent 4 378 972. The concentrations are analogous to reagent 3. Reagent 6. The solvent component consists of a solution of sulfur dioxide (0.7 mol/L) in pyridine. The titrant component is the same as that in reagent 3. Reagent 7. The same composition as reagent 3 except that methanol is replaced by 2-methoxyethanol. Reagent 8. As reagent 3 except that methanol is replaced by propylene carbonate. Reagent 9. As reagent 3 except that methanol is replaced by dimethylformamide.
5
rng H,O
-
Figure 3. Titration of 5 mg of water in the presence of 1 mL of benzaldehyde using reagents 1 to 5.
Reagents 10-19. Two-component reagents based on imidazole, the solvent component of which contains the alcohols given in Table I. The concentrations correspond to the concentration of reagent 5. The titrant component is identical with that of reagent 3 (iodine in xylene, water equivalent 10 mg/mL). To carry out the water determinations, we used the Metrohm KF titrator E 547 with a plunger buret, E 655/4, which was connected to a recorder. The course of the titration was recorded graphically (titration time vs. reagent volume). To compare the behavior of different KF reagents, we have selected the reagents 1 to 5. With the one-component reagents 1 and 2, for each titration 50 mL of methanol was put into the titration vessel and titrated to dryness using the KF reagent (20 s end point). The respective samples (water, acetone, or benzaldehyde) were then added and titrated. With the two-component reagents 3,4, and 5,50 mL of the respective solvent component was taken into the titration vessel and titrated t o dryness using the titrant component 3. The samples were then added and titrated. The course of each titration is depicted in the Figures 1t o 3. In order to determine the rate of water formation for various ketones and aldehydes, 50 mL of the solvent component 3 or 5 was added to the titration vessel and titrated t o dryness, after which the sample was added and the titration was immediately started. The titration was allowed to run for a total of 10 min
ANALYTICAL CHEMISTRY, VOL. 57, NO. 14, DECEMBER 1985
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Table I. Reagents Containing Different Alcohols for Determination of Water in Carbonyl Compounds
no.
water recov rate, %
alcohol
methanol 1-propanol 11 1-butanol 12 2-propanol 13 2-butanol 14 ethylene glycol 15 propylene glycol 16 2-methoxyethanol 17 benzyl alcohol 18 2-chloroethanol 19 trifluoroethanol 5 10
butyraldehyde benzaldehyde cyclohexanone free avail free avail free avail WFR, pg water, % water, % WFR, pg water, % water, % WFR, pg water, % water, %
100
250
100 100 100 100 100 100 100 100
250 250
100 96
72 25 19 10 12 38 40 46
250 230
250 400
120
25
150 120 90
25 54
83 59 56 36
160 100 80
42
140 100 200 75 35 60 15
75 75 53 73 86
62
62 10
97 97 95 89 95 96 94 59 99 99 91
0 0 0
260
84 84 17 50 88 91
10
54 40 30 50 40
560
8
22
1000
20
300 350
30 10
300
10
55 45 61 54
80
10
92
990 780 570 1600
40
1000
6 5 6
E P 4.6
~‘
EP
4-l5
10
6.6
5
10
rng H,OFigure 4. Titration of 10 mg of water with reagent 5 in the presence of 1 mL of cyclohexanone (graph a), or 1 mL of benzaklehyde (graph b). Curves 1 depict the immediate tltratlon; curves 2 depict the titration after a delay time of 5 min.
5
5
10
m g H,O
10
Flgure 5. As glven in Flgure 4 but with reagent 3.
and the amount of reagent consumed between the fifth and the tenth minute was recorded. From this the rate of water formation was calculated and is given in Table 11. The sample size varied. With stable ketones, up to 20 mL (or 20 g) was used. When more reactive compounds were investigated, smaller samples were used, in some cases as little as 1mL (1g). With benzophenone and other compounds whose solubility is limited, even smaller samples had to be used. For these compounds only, threshold values for the rate of water formation are given in Table 11. To detect the bisulfite reaction, 50 mL of solvent component 5 was added to the titration vessel and titrated to dryness. One milliliter of cyclohexanone containing 10 mg of water was then added and immediately titrated (Figure 4, graph al). The titration was repeated in the same way except that the titration was started 5 min after the sample had been added (Figure 4, graph a2). The same procedure was employed for the investigation of benzaldehyde (Figure 4, graphs b l and b2). All of these titrations were then repeated using reagent 3 (Figure 5). To investigate the influence of the solvent, reagents 6 to 9 were used to determine water in cyclohexanone and benzaldehyde. For
mg
H,O
-
Figure 6. Titrations of 10 mg of water using pyridine reagent 6: (a) in absence of aldehydes and ketones: (b) in presence of 5 mL of cyclohexanone; (c) in presence of 5 mL of benzaldehyde; (d) in presence of 5 mL of butyraldehyde.
-
4 1, mg H,O
Figure 7. Titrations of 10 mg of water using the 2-methoxyethanol reagent 7. Graphs a-d are under the same conditions as those in Figure 6.
1
EP94
EP95
71 5 10
5
mg H,O
-
10
Figure 8. Titrations of 10 mg of water using the propylene carbonate reagent 8. Graphs a-d are under the same conditions as those in Figure 6.
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Table 11. Rates of Water Formation for Various Ketones and Aldehydes with Reagents 3 and 5 (pg of water/g)/min reagent 3 reagent 5
substance
Aliphatic Ketones acetone methyl n-propyl ketone methyl isobutyl ketone ethyl isobutyl ketone allylacetone 3-octanone 2-decanone cyclohexanone l,l,l-trifluoracetone hexachloracetone
400 110 30
20
4
2
60 20 50 450
20 6 15 250 10 6
14 2
70
I
Aromatic Ketones acetophenone 4-fluoroacetophenone 2-aminoacetophenone benzyl methyl ketone benzylacetone benzophenone benzoin
15 6 110 50
