Carbohydrazide as a Solid Reducing Agent for Reaction Gas Chromatography Determination of Azo, Nitro, and Sulfonate Compounds Peter C. R a h n and Sidney Siggia Department of Chemistry, University of Massachusetts, Amherst, Mass. 01002
Azo and nitro compounds have been reduced to their corresponding amines using carbohydrazide as a reducing agent. Sulfonates have been reduced to the corresponding hydrocarbons. The amines and hydrocarbons are measured gas chromatographically. Carbohydrazide is effective since hydrogen and hydrazine are both released on decomposition and these bring about the desired reduction. Most of the decomposition products of the carbohydrazide are gaseous at low temperatures and pass through the gas chromatographic column rapidly well before the amines and hydrocarbons. The fact that the reducing agent is used neat at a high temperature results in fast reductions.
Ordinarily the determination of azo compounds is achieved by their reduction with titanous salts. The method was devised by E . Knecht ( 1 ) and consisted of boiling a n aqueous acid solution of the azo compound with a n excess of titanous sulfate or chloride in the absence of oxygen. The excess titanous salt is back titrated with a ferric salt. The method is widely used, but fails occasionally when the hydrazo intermediate undergoes a benzidine, diphenylene, or semidine rearrangement ( 2 ) . This method is also time consuming and requires a high level of manipulative technique. Electrochemical methods have been employed primarily to determine the azo compounds through electrometric titration ( 3 ) and to characterize the 0 - and p-isomers of hydroxyazo compounds through the potentiometric titration of azo compounds with chromous sulfate ( 4 ) . Cabral and Turner e t al. have submitted a series of azo compounds to polarographic study to evaluate the possibility of identifying various azo compounds, but the half-wave potentials were found not to bear a simple relationship to structure. Hence, the Cabral and Turner method can be employed for quantitative estimations but not for identification of the azo compounds (5-10). A series of reducing agents, lithium aluminum hydride in ether ( I I ) , lithium aluminum hydride activated by E. Knecht and E. Hibbert, "New Reduction Methods in Volumetric Analysis," Longmans, Green and Co., New York, N.Y., 1925, p 33. (2) G. S. Hammond and H. J. Shine, J. Amer. Chem. SOC., 72, 220 (15;jO). (3) J. S. Parsonsand W. Seaman, Anal. Chem., 27, 210 (1955) (4) S. Wawzonek and J. D. Friedrickson, J. Amer. Chem. SOC.. 77, 3985 (1955). (5) J. Cabral and H. A. Turner, J. SOC. Dyers Colour.. 7 2 , 158-67 (1956) (6) C. R. Castos and J. H. Sayor, J. Amer. Chem. SOC.. 75, 1427 (1953). (7) L. Holleck. A. M . Shams. R. M . Saleh, and G. Holleck, Z. Naturforsch. 8.19, 162 (1964). (8) J. P. Hillson and P. P. Birnbaum, Trans. Faraday SOC., 48, 478 (1952). (9) A. L. Markman and E. V. Zinkova. J. Gen. Chem. USSR, 29, 3058 (1959). (10) B. Nyard.Ark. Kemi. 20, 163 (1962) (11) F. Anet and J. Muchowski, Can. J . Chem., 38, 2526 (1960). (1)
2336
metal chlorides (IZ),and catalytic hydrogenation (13-16) have been used in the reduction of azobenzene and its analogs, but in few cases have these reactions been applicable to quantitative analysis. The well-known Wolff-Kishner reduction is one of the numerous reduction methods employing solutions of hydrazine hydrate with or without catalysts ( 17). The trend has been to use glycols as high boiling solvents to raise the reaction temperature and increase the yield of the free amine (14). Hydrogenation via the gas chromatographic pathway by using hydrogen as the carrier gas and including a precolumn containing a hydrogenation catalyst has been used to effect reductions and is reviewed by Ettre ( 1 8 ) . Nitro compounds usually can be determined by the same reduction methods employed for measuring azo compounds (11, 19, 20). However, many azo and nitro compounds have a low volatility and/or decompose on heating, so direct gas chromatography cannot be applied. Reduction to the respective amines would be useful gas chromatographically since the amine reaction products generally are volatile. The amines produced are characteristic of the azo or nitro compound, and the amount of amines is a function of the original amount of azo or nitro compound. In carbohydrazide reduction gas chromatography, a highly concentrated reducing agent which is solvent-free is employed. This reduces the time of reaction and drives the reaction t o completion as well. Carbohydrazide reduction gas chromatography for azo and nitro compounds has advantages in addition to rapid analysis. It enables mixtures of azo compounds and nitro compounds to be resolved. No interference due to rearrangement to benzidine or biphenyl is encountered upon reducing the azo compounds, nor is there any interference due to the saturation of the aromatic rings. Also, the use of hydrogen as a gas chromatographic carrier gas is avoided and the sample does not have to be volatilized into the reactor. In the method described below, the sample is fused with the reductant and the volatile primary amines liberated are monitored gas chromatographically. The resulting primary amines help define the nature of the azo compound. Another advantage of the carbohydrazide reduction method is the use of micro samples; 0.1-0.2 milligrams usually suffice. The quantitation is achieved by measurement of the primary amine. (12) M. Busch and K. Shulz, Ber. Deuf. Chem. Ges. B , 62, 1458 (1929). (13) T. F. Stepanova. 0. F. Ginzburg, and E. V . Levina, Zh. Prikl. Khim. (Leningrad), 42, 2390 (1969) (14) S. Pietra, Ann. Chim. fRome), 47,410 (1957). (15) S. Pietra, Ann. Chim. fRomel, 52, 727 (1962) (16) S. Kubota, T. Akita, and T. Yokoshima, J. Pharm. SOC. (Japan), 78, 1 194 (1958). (17) D. Todd, Org. React.. 4, 378 (1948). (18) L. S. Ettre and W. McFadden, "Ancillary Techniques of Gas Chromatography," Wiley Interscience, New York, N . Y . , 1969. (19) L. Kuhn. J. Amer Chem. SOC..7 3 , 1510 (1951). (20) M. J. S. Dewar and T. Mole, J . Chem. SOC..1956, 2556.
ANALYTICAL CHEMISTRY, VOL. 45, NO. 14, DECEMBER 1973
Table I. Columns and Conditions Used to Monitor Products of Carbohydrazide Reductiona Column Flow rate Isothermal Programmed Molecular Sieve 5A, 12-ft X in. SS SE 30-12%, 10-ft X %-in. SS DC 200-9%, 5-ft x '/*-in. SS Versam ide-5.5%, 6-ft X in. SS Chromosorb 103, 2.5-ft X '/&. SS a
Injector 200
OC,
1 2 m l / m i n 60°C
None
36 ml/min
80 "C for
26"/min to 210 "C
65ml/min
4 min 230°C
None
57 ml/min 47 ml/min
G
70 "C for lO"/min to 200 "C 10 min 130 "C for 24"/min to 240 "C 6 min
manifold 250 "C, hot wire detector 250 "C at 225
mA.
EXPERIMENTAL Apparatus. T h e reaction chamber consists of a modified pyrolysis apparatus commercially available from Perkin-Elmer Corporation, Norwalk, Conn. (Pyrolysis Assembly 154-0925). T h e exact modifications of the pyrolysis assembly can he found in t h e earlier work by Siggia. Whitlock, a n d T a o ( 2 1 ) .T h e pyrolysis apparatus (Figure 1) was connected t o a 10-inch by 0.125-inch 0.d. stainless steel tubing which was shaped in a loop (L, Figure 1) t o act a s a trap for t h e reaction effluent. T h e trap-loop was packed with silanized glass wool (Analabs, Inc., North Haven. Conn.) to reduce t h e dead volume before the injector of the gas chromatograph, From the trap-loop, the sample traveled through the inlet assembly ( P . - E . 009-0276) into the gas chromatograph (both P . - E . Model 900 and P.-E. Model 990 were used in this study). T h e inlet assembly consisted of a 3-inch X 0.062-inch stainless steel tube wrapped in asbestos a n d heated by means of nichrome wire; the heat was controlled by means of a Variac. Both gas chromatographs were operated using thermal conductivity detectors and programmed temperature. During t h e reduction reaction, t h e trap-loop was submerged in liquid nitrogen contained in a 70-mm o.d. Dewar flask. Upon completion of the reaction, t h e liquid nitrogen was replaced by a 50-mm 0.d. heating collar. T h e collar was made from asbestos wrapped around a wire mesh and this was then wrapped with nichrome wire, covered with asbestos, and connected to a Variac to provide temperature control. T h e heating collar was maintained a t 270-280 "C t o provide a quick temperature increase t o flash the reaction products out of t h e trap into the gas chromatograph with a minimum of peak broadening. The initial experimental conditions were determined using a P.-E. 990 GC equipped with a flame ionization detector. b u t all t h e quantitative results were obtained using a P . - E . 900 GC which was equipped with a hot wire detector. All t h e columns and the experimental conditions used in this investigation are shown in Table I. All these columns were suitable for the required analysis, although as a general procedure for the measurement of t h e primary amines, Chromosorb 103 (Johns Manville) was best. Similar to the Porapak phases, Chromosorb 103 must be conditioned daily with t h e amines of interest by injecting t h e known amines before any samples are run (22). At 130 "C, t h e Chromosorb 103 column quickly elutes the gases Ha, CO, NP, and "3, a n d then H20. On temperature programming, t h e aromatic amines are eluted according t o their boiling points and basicity. Reagents. T h e carbohydrazide reagent was obtained from Olin-Mathieson a n d Eastman Organic Chemicals (7387) and purified by repeated recrystallizations from ethanol a n d water. T h e purified reagent was ground t o a fine powder, dried a t 110 "C, and then stored in sample vials until used. Isonicotinic hydrazide and adipic dihydrazide were obtained from Olin-Mathieson and recrystallized from alcohol. 4,4'-Azodiphenetole was obtained from Eastman Organic Chemicals (9857) and recrystallized from hot acetic acid. 5-(pNitropheny1azo)salicylic acid-sodium salt (784) and Methyl Orange ((2-432) were obtained from Eastman Organic Chemicals (21) S. Siggia, L. R . Whitlock. and J . Tao, Anal. Chem.. 41, 1387 (1969). (22) J. M. Hogan, R. A. Engel, and H . F. Stevenson, A n a / . Chem., 42, 249 (1970).
Y
I
I
-
Figure 1. Modified pyrolysis chamber a n d recrystallized from E t O H and dried in a drying pistol to remove t h e solvent a n d volatile impurities. p-Nitroaniline (1791, sulfanilic acid (238), 4,4'-azodianiline (9439), and p-phenylazoaniline (P-1375) were purchased from Eastman Organic Chemicals and recrystallized from EtOH and water. I n general t h e other azo compounds, S u d a n Yellow, Para Red. rn-(nitropheny1azo)salicylic acid-Na salt, were prepared by first forming the diazonium salt from t h e proper amine by reaction with nitrous acid:
/
R
N=N+CI-
w
+
2H10
+
NaCl
(1)
/
R = NO?. H.SO$"
This salt was then reacted with the coupling compound a t a controlled rate a n d temperature (23).
R
o
N R'
= =
K
e
R
1
+
HCI
(2)
OH."1, SHR". SR,"
p-Phenylazophenol (417) was obtained from Eastman Organic Chemicals and recrystallized from E t O H . This was then utilized t o prepare p-ethoxyazobenzene by reacting it with ethyl iodide (24). After crystallization, all the azo compounds were further purified by vacuum sublimation and the purity was checked by elemental analysis. T h e analytical standards, aniline. p-anisidine, p-phenylenediamine, and "V,N-dimethylphenylenediamine. were obtained from Eastman Organic Chemicals and purified by recrystallization from EtOH and HzO and then vacuum distilled or vacuum sublimed, respectively. Procedure. Solid samples of the azo compounds, ranging trom 0.05-0.2 mg, are weighed into the 11-mm micro size platinum boats (Fisher Scientific Company 20-086) using a MicroGramAtic balance (Mettler Instrument Corporation). An alternative sampling method is to prepare a standard solution of the azo compound in a suitable solvent and inject 1 0 - ~ 1aliquots onto the 8 mg of carbohydrazide reagent contained in each boat. The sample is placed in the pyrolysis storage tube (Figure 1, A ) and the desired temperatures for the reactor oven ( I ) , heating loop (L), and injector precolumn ( G ) , are selected. After purging the syst e m for 15 minutes with helium, the thermal conductivity detector is activated and allowed to stabilize. T h e samples are manipulated by use of a magnet and pusher bar ( F ) into t h e reactor oven, which is maintained a t 220 "C. (23) A. Vogel, "Practical Organic Chemistry." Longmans, Green, and Co., New York, N.Y., 1957. (24) W. F. Jacobson, Ber. Deut. Chem. Ges. E, 25, 944 ( 1 8 9 2 ) .
ANALYTICAL CHEMISTRY, VOL. 45, NO. 14, DECEMBER 1973
2337
TEMPERATURE
'C
Figure 2. TGA of carbohydrazide
Upon completion of the reaction, the boat is withdrawn from t h e oven a n d deposited in the lower storage area (D). T h e recorder is then started and t h e trap-loop is heated to drive off the condensed products directly into the gas chromatograph. T h e calibration curve is obtained under identical conditions by injecting known quantities of t h e known amine into t h e platinum boat which is placed beneath the rubber septum (B). After the injection, the boat is pushed into t h e reactor oven, t h e amine is subsequently trapped into the loop, a n d then swept into the gas chromatograph by heating the loop. For this work, quantitation of all peaks was accomplished by the method of "cut and weigh."
RESULTS AND DISCUSSION Development of a Suitable Reducing Agent. Hydrazine could be used as the reducing agent since it is a very strong reductant ( 1 4 ) . However, it is a volatile liquid and was considered unsuitable for reaction gas chromatography since it would evaporate before the reduction reaction was completed. Also, pure hydrazine is unstable in air. A solid reducing agent was more desirable so the reaction could be contained in a boat while the temperature of the reaction was controlled. The hydrazides were chosen since these compounds are solids and quite stable a t room temperature in the anhydrous state. Isonicotinic hydrazide and adipic dihydrazide provided some reduction of azobenzene. but. as evidenced by their thermogravimetric analysis, no reaction occurred until the temperature exceeded 250 "C. Although these hydroazides could be suitable, the limitation of 250 "C was too restricting and carbohydrazide was chosen. From the thermogram of carbohydrazide (Figure 2), it can be seen that a weight loss began to occur a t 150 "C. A t 225 "C, a break in the curve was evident with a corresponding weight loss between 42-45%, and as the temperature was programmed up to 450 "C, only 8% remained. In conjunction with the TGA, a Differential Scanning Calorigram showed a transition occurring a t 432 "K (melting point 431 OK) with further calorimetric changes occurring continually. The empirical formula for the residue from the TGA was C ~ Z H Z ~ N ZIt ~isObelieved ~ ~ . t h a t the resultant material is a condensation product resulting from the high temperatures; this is supported in the literature ( 2 5 ) . To elucidate the reactive species which is responsible for the reduction properties of carbohydrazide, the decomposition products of carbohydrazide were determined. A t 225 "C, carbohydrazide decomposes yielding Hz, 0 2 , Nz, CO, and "3. When the sample boat was kept in the reactor oven, these gases continued to be evolved for over one hour. This indicates t h a t carbohydrazide continues to decompose for one hour and is capable of reducing nonvolatile azo compounds for the same time period. (25) Belgium Patent, Phrix-Arbeittsgemeinshaft No. 443,952
2338
The hydrogen evolved is probably the source of much of carbohydrazide's reducing ability. However, a large unidentified peak was also seen on the gas chromatogram. This peak was collected and its Raman spectrum was determined using a Model 82 Cary Raman Spectrometer. A Raman spectrum of 64% hydrazine hydrate was also obtained. The results conclusively show that hydrazine is also produced when carbohydrazide decomposes. The possibility that hydrazine could also be acting as a reducing agent in the reaction was proved through the reaction of hydrazine and p-nitroaniline. By employing a 4-rl aliquot of 64% hydrazine hydrate on 0.1 mg p-nitroaniline, a 92% conversion to p-phenylenediamine was accomplished. However, because of its instability in the anhydrous state a t moderate temperature and its volatility, hydrazine is unsatisfactory as a reducing reagent for general use. In all the experiments with azo and nitro compounds, carbohydrazide was found to be the better choice due to three factors: 1) the samples could be coated directly on the reducing reagent providing maximum coverage and interaction, 2) the reaction can be extended beyond the time that hydrazine vaporizes from the sample boat, and 3) the quantity of reduction product formed while using carbohydrazide was equal to or greater than that obtained from hydrazine. In conclusion, this work showed that both Hz and hydrazine are formed during the decomposition of carbohydrazide and that both play a part in the reduction reaction. In addition, this work supports the theory that not all hydrazine reactions involve the diimide intermediate since we apparently do not have any dehydrogenation conditions to first produce the diimide (26, 27). Catalysts Study. Although the azo compounds appeared to be readily reduced in the platinum sample boats, some of the azo compounds are difficult to reduce completely. An attempt was made t o examine the possibility of using a catalyst to increase the yield of primary amines in these cases. Into each of several porcelain boats containing 4.6 mg of carbohydrazide was added 0.091-0.155 mg of 5-(pnitropheny1)azosalicylic acid-sodium salt and various palladium and platinum catalysts. The results are summarized in Table 11. Yone of the conversions obtained exceeded that which was achieved when using platinum boats as sample holders. This indicated that the platinum boat acted as a reduction catalyst and was equal to or superior to the palladium catalysts investigated. Further study on the use of platinum as a catalyst was made using a Chemalytics Thermal Analysis Unit (MP-3) which employs a glass tube reactor. Platinum on asbestos (Fisher Laboratory Chemicals P-152) was inserted as a catalyst. For the reaction of p-phenylazoaniline with 8.6 mg of carbohydrazide, the conversion to aniline and pphenylenediamine was equal to that obtained while using a platinum boat. This was confirmed using the PerkinElmer Pyrolysis unit with only a platinum boat and a platinum boat containing platinum on asbestis. The results (Table 11) show that there is negligible additional benefit obtained from using the platinum on asbestos over using just the platinum boat. In summary, this investigation has indicated t h a t there appears to be little need to employ high surface area catalysts in this reaction. Determination of Azo, Nitro, and Sulfonate Compounds. The results using the carbohydrazide reduction (26) E. J. Corey, W. L. Molk, and D. J. Pasto. Tetrahedron Lett.. 1961, 350. (27) S.Hunig, M . Mueller, and W. Thier, Tetrahedron Lett., 1961, 353.
ANALYTICAL CHEMISTRY, VOL. 45, NO. 14, DECEMBER 1973
Table II. Catalyst Study Using Porcelain Boats Compounda
204 pg A 427 pg A 232 pg A
504 pg A 391 p g A 280pg 0 l0OpgC l0Opg
a
c
Product
Actual, pg
Found, pg
p-Phenylenediamine p-Phenylenediamine
71.2 149.
11.9 104.
Converted, % 16.8 70.0
p-Phenylenediamine
81 .O
77.7
96.1
Catalyst
None 1.111 mg Pd-CaCO3 2.040 mg Pd-CaCO3 1.158 mg Pd-C 0.0954 mg Pd-C 2.14 mg Pd-CaC03 Pt-boat
+
Pt-boat 928 pg Pt on asbestos
p-Phenylenediamine
176.
5.5
3.1
p-Phenylenediamine
137.
3.98
2.9
p-Phenylenediamine
219.
201.
46.2 53.8 46.2 53.8
Aniline p-Phenylenediamine Aniline
p-Phenylenediamine
91.7
38.5 44.1 38.9 43.9
83.4 82.0 84.3 81.5
Compounds: ( A ) 5-(p-nitrophenylazo)salicyclic acid-sodium salt, ( B ) p-nitroanlline, (C) phenylazoaniline
Table 1 1 1 . Determination of Azo Compounds by Carbohydrazide Reduction and Measurement of Liberated Amines by Gas Chromatography Compound
p-Phenylazophenol
Product determined Aniline
p-Hydroxyaniline p- Phenylazophenetole 4,4'-Azodiphenetole Sudan Yellow p-Phenylazoaniline 4,4'-Azodianiline Methyl Orange
Aniline
p-Ethoxyaniline p-Ethoxyaniline Aniline Aniline
p-Phenylenediamine p-Phenylenediamine N,N-Dimethylphenylenediamine
reaction gas chromatography method for the determination of azo compounds are given in Table 111. A typical chromatogram of an azo compound (p-phenylazoaniline) is given in Figure 3. Generally, the chromatogram of a single azo compound shows only the primary amines resulting from the saturation of the azo bond and the decomposition products of carbohydrazide. The low conversion obtained for p-phenylazophenetole was attributed t o its high volatility since the sample was vaporized into the gas chromatograph before complete reduction had occurred. T o decrease the rate of volatilization, the reactor temperature and flow rate were dropped to 210 "C and 47 ml/min, respectively. The result for the products aniline and p-ethoxyaniline was a n increase from 39 t o 75.69'0 with a relative standard deviation of 1.93. Similarly for other highly volatile azo compounds-phenylazoaniline. 4,4'-azodiphenetole, and phenylazophenolthe conversion was only 83.0, 86.6, and 90.8%, respectively, yet the precision was excellent. By employing pure azo compounds as standards and constructing a working calibration curve for all the experimental conditions, the peak areas obtained are directly related t o the quantity of azo compound in the sample. The results for the analysis of nitro compounds and azo compounds containing reducible nitro groups are shown in Table IV. With carbohydrazide, the nitro compounds react in 2-15 minutes with a 90-97% conversion. The method is rapid and provides a micromethod for the determination of nitro compounds. As the volatility of the analyte decreased, the reduction reaction became more
Actual, pg
% Converted f RSD
Found, pg
55.6 65.3 54.6 80.6 104. 59.8 42.0 49.0 155. 68.9
No. of
detns
90.8 f 1.8 90.7 f 1.5 75.6 f 1.9 75.5 f 1.9 86.6 f 1.5 97.7 f 2.2 83.0 f. 0.8 81.7 f 1.0 97.0 f.2.1 98.5 f 1.5
50.5
59.2 41.3
60.9 90.1 58.5 35.0 40.0
150 67.9
13 10 8
6
6 11
16
2 W
0
2
6
8
10
12
14
TIME, minutes
Figure 3. Chromatogram of p-phenylazoaniline
quantitative since the reductant and analyte remained in contact. The carbohydrazide reduction of sulfonate compounds provides a method of analysis for a class of compounds which are completely nonvolatile. Table V and Figure 4 show data for the determination of some of these compounds. The total reaction time was 2-4 minutes at 220 "C. The analysis time is shorter and the reaction conditions are much milder than the 30 minutes a t 760 "C re-
ANALYTICAL C H E M I S T R Y , VOL. 45, NO. 1 4 , DECEMBER 1973 * 2339
Table I V . Determination of Nitro Compounds by Carbohydrazide Reduction Actual, PQ
Found, PLl
% Converted f RSD
No. of
Product Determined
p-Phenylenediamine
109.6
106.0
97.8 f 2.1
9
p-Phenylenediamine p-Phenylenediamine rn- Phenylenediamine
86.5 102.3 105.4
79.3 99.9 103.1
91.7 f 1.5 97.7 f 1.8 97.7 f 1.4
6 6 6
p- Phenylenediamine Aniline
69.8 49.2
67.3 47.4
97.1 f 1.2 97.3 f 1.1
6
Compound
5-(p-N itrophenyl) azosalicyclic acidsodium salt p- Nitroaniline Para Red 5- (m-N itrophenyl) azosalicylic acidsodium salt p-Nitroazobenzene
detns
Table V. Determination of Sulfanilic Acid and Sulfonates by Carbohydrazide Reduction Reaction Gas Chromatography Found, Actual, % Converted No. of Compound
Sulfanilic acid Methyl Orange
Sulfanilanilide Sulfanilamide Benzene sulfonate p-Toluene sulfonate
Product Determined
Pg
PQ
f RSD
Aniline Aniline N, N-Dimethylphenylenediamine N, Methylphenylenediamine Aniline Aniline Benzene Toluene
40.7 39.4 57.7
26.8 25.7 56.0
65.7 f 0.2 65.7 f 1.5 98.5 f 1.6
0.87 56.9 62.1 61.1 55.4
detns
6 6
0.87 39.8 43.7
69.6 70.3 68.0 69.1
41.5 38.3
f 0.4 f 1.2 f 0.9 f 0.6
12 6 6 6
A
I 0
I 2
I 4
B
I I 6 8 TIME, minutes
12
10
14
Figure 4. Chromatogram of sulfanilic acid
Table V I . Analysis of Azo Compound Mixtures by Carbohydrazide Reduction Reaction Gas Chromatography Compound
+
Methyl Orange sodium 4'-methylaminoazobenzene4-sulfonate p- Phenylazophenetole NaCl Azodianiline p-phenylazoaniline p-phenylazoaniiine i- azodianiline
+
+
2340
Actual, Fg
Found, PQ
% Detected No. of
f RSD
detns
57.7
56.0
98.5 f 1.6
6
0.87
0.87
I
I
I
8
10
12
14
TIME. minutes
2.69
71'0 19.6 98.2 14.2
2.68
70'3 19.5 97.6 14.2
99.7 f .9
99'0
6
Figure 5. Chromatogram of azo mixture
6
quired in the sulfonate method developed by Siggia, Whitlock, and Tao (21). The quantity of aniline obtained was about two thirds of the theoretical amount and was independent of the amount of carbohydrazide present.
* ''O
99.6 f .58
ANALYTICAL CHEMISTRY, VOL. 45, NO. 14, DECEMBER 1973
The exact mechanism of this reaction has not yet been determined and this work is being further pursued. Analysis of Mixtures. Various mixtures of Methyl Orange, 4,4'-azodianiline, were prepared and analyzed. A typical chromatogram of the mixture 4,4'-azodianiline and p-phenylazoaniline is shown in Figure 5. The pure sample, p-phenylazoaniline, is reduced to p-phenylenediamine and aniline, and by comparing the peak areas for the pure compound to those from the mixture, the difference in peak areas is due to the quantity of 4,4'-azodianiline in the mixture. The results of this study are given in Table VI. Thus, not only can the total azo compound be determined for a mixture, but also the qualitative and quantitative analysis can be ascertained.
CONCLUSIONS
A method is presented in which within one piece of apparatus, nonvolatile azo, nitro, and sulfonate compounds can be determined. By use of the carbohydrazide reduction and gas chromatographic analysis, one can handle a variety of compounds from the easily reactive azo bond to the stubborn reduction of p-nitroanilines. The analysis is not limited to conditions of the solution reduction using hydrazine. The analysis is rapid and specific, and it enables resolution of mixtures of azo and nitro compounds. Received for review April 13, 1973. Accepted June 29, 1973. This work was supported by National Science Foundation Grant No. G P 28054.
Determination of Bis(chloromethy1) Ether in Air by Gas Chromatography-Mass Spectrometry L. A. Shadoff, G. J. Kallos, and J. S. Woods Analytical Laboratories, The Dow Chemical Company, Midland, Mich.
Bis(chloromethy1) ether (bisCME) may be determined at the one part per billion level in air by concentrating the organics on a retentive substrate (Chromosorb 101) with subsequent analysis by gas chromatography-mass spectrometery. By monitoring CzH40CI+, the most intense ion in the mass spectrum of bisCME, during elution of the trapped organics, an extremely specific analysis is performed. For the signal to be assigned to bisCME three things must occur simultaneously: the mass must be correct, the retention time must be correct, and the observed chlorine isotope ratio must be correct. It has also been shown that bisCME may be quantitatively trapped and retained for extended periods of time and determined within 10Y0 accuracy.
Bis(chloromethy1) ether (bisCME), a possible impurity in the chloromethylating reagent chloromethyl-methyl ether, has recently been reported to be a carcinogen when present a t low concentration in the air (1-5). To ensure that the environment in production facilities utilizing this reagent contains no hazard from bisCME, a n analytical procedure was needed to monitor the atmosphere a t the 1-vppb (volume part per billion) level. A recent report by Collier (6) employs trapping the organics from air onto Porapak Q with analysis of the organics by high resolution mass spectrometry. We present here recovery data for this trapping method and use a method (1) B. L. Van Duuren, B. M . Goldschrnidt, L. Langseth, et ai., Arch. Environ Health, 16, 472 (1968). ( 2 ) J . L . Gargus. W. H. Reese. J r . , and H. A . Rutter, Toxicoi. Appi. Pharrnacol.. 1 5 , 9 2 (1969). (3) K. J . Leong, H. N. MacFarland, and W. H . Reese, J r . , Arch. Environ. Health. 22, 663 ( 1971 ) (4) B. L. Van Duuren, A . Sinak, B. M . Goldschrnidt, C. Katz. and S. Melchionne. J. Nat. Cancer lnst.. 43, 481 (1969) (5) B. L . Van Duuren, Ann, N. Y . Acad. Sci.. 163, 633 (1969). (6) L . Collier, Environ. Sci. Technoi. 6 , 930 (1972).
of analysis not subject to the possible interference encountered using mass spectrometry alone. The analytical method chosen is gas chromatographymass spectrometry (GC-MS). This technique has extremely high specificity for bisCME, high sensitivity, and rapidity of analysis. Specificity is needed because of the diverse substances encountered a t the part-per-billion level in air. Positive identification of bisCME is required to avoid unnecessary evacuation of personnel and possible production shut-down. High sensitivity is required since 1 vppb corresponds to 4.7 ng/l. of air as calculated from the Ideal Gas Law. Rapidity of analysis generates immediate knowledge of hazards.
EXPERIMENTAL Sampling Tubes. These are prepared by packing y,-in. 0.d. X 2-in. long stainless steel tubing with 1Yz inches of SO/lOO mesh Chromosorb 101 (Johns-Manville) using silanized glass wool plugs in the ends. These are conditioned a t 200 "C and 10 cm3/min Nz (or He) flow overnight. They are then cooled under flow and capped immediately upon removal. An identification number is scribed on one of the Swagelok (Crawford Fitting Co.) nuts. S o preliminary extraction is necessary as reported for Porapak Q ( 6 ) . Sampling Method. Spot samples may be obtained by attaching the sampling tube to a manual syringe pump made from a 100 cm3 glass tip hypodermic syringe. Continuous sampling a t fixed points is accomplished by attaching a rotary vacuum p u m p to a throttling valve and manometer. Each sampling tube is calibrated such t h a t the pressure drop corresponding to 1 1. per hour is determined. The pressure drop is then adjusted with the throttling valve to establish the flow. We have established the convention t h a t the sample is drawn onto the end of the sampling tube with the numbered Swagelok nut. Gas Chromatography Column. Four feet of Yd-in. or Yg-in. 0.d. stainless steel tubing is rinsed internally with water, acetone, and methylene chloride and air dried. The cleaned tubing is then packed with SO/lOO mesh Chromosorb 101 (Johns-Manville) and conditioned overnight a t 200 "C and 10-30 cm3/min Nz (or He) flow. Gas Standards of bisCME in nitrogen may be prepared by partially filling a 5-1. Saran brand (Trademark of The n o w Chemical Company abroad) plastic film gas bag with nitrogen
ANALYTICAL CHEMISTRY, VOL. 45, NO. 1 4 , DECEMBER 1973
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