Table 11. Analysis of Known Arylhydroxylamine Mixtures for Arylhydroxylamine
Table I. Calibration Data for Various Arylhydroxylamines
Compound
N-Phenylhydroxylamine
Final concn, M X 10-5
1.5 3.0 6.0
p-Chlorophenylhydroxylamine
1.5
p-Tolylhydroxylamine
3.0 6.0 1.5 3.0 6.0
Arylhydroxylamine“ Mixture
Absorbancea
0.163 i O.OISb 0.320 j= 0.011 0.605 0.008 0.096 ?L 0.014 0.196 =k 0.008 0.403 + 0.008 0.096 + 0.014 0.196 i 0.008 0.396 i O . 0 0 2
a Measured a t 450 nm and based upon 5 replicate determinations of each solution. Confidence limits a t p = 0.05
droxylamine and p-tolylhydroxylamine produce color which absorbs a t the same wavelength maximum as N phenylhydroxylamine but with diminished intensity. The absorbance data are shown in Table I. The reduced absorption for the substituted derivatives of phenylhydroxylamine may be the result of a less-than-quantitative yield of the colored product under the conditions of the analytical determination. It was suggested that heating the hydroxylamine and acridine on a steam bath might ensure a more complete reaction. However, maximum color development could be obtained upon shaking the solution and allowing it to stand at room temperature for 5 minutes. Repeated readings on a series of different samples indicated good color stability for periods u p to 24 hr. Although stability of‘ the 9-chloroacridine reagent solution has been discussed previously (12, 13), our present work has further revealed that refrigeration of the acridine solution after preparation allows use of the solution for approximately 8 hours before decomposition occurs. The analysis method is a micro procedure, and sensitivity is in the 0.8-3 pg/ml range (10-5M) of arylhydroxylamine. Reagent preparation is simple and rapid since 9chloroacridine is commercially available and can be used without further purification or modification procedures. The time involved in the actual analysis procedure is less than 30 minutes compared to the colorimetric method by complex formation which takes from 2 to 14 hours depending upon the reagent used ( 3 ) . Standard curves can be prepared by plotting absorbance readings us. the volumes taken of equimolar concentrations of various arylhydroxylamines. In all cases, Beer’s law holds for this system. Data from several systems shown in Table I1 indicate that this procedure permits the determination of arylhydroxylamines in the presence of primary aromatic amines (whose colorimetric determination with 9-chloroacridine has been previously reported, vide injra), primary aliphatic amines, phenols, aromatic nitro compounds, aliphatic and aromatic amides, and aliphatic hydroxylamines. It has been shown previously that secondary and tertiary aromatic, heterocyclic, and aliphatic amines and carbonylcontaining compounds did not interfere with colorimetric determinations utilizing 9-chloroacridine. Although one cannot exclude the possibility that these other functional (13) J. T. Stewart, A . B. Ray, and W. B. Fackler, J. Pharm. 1261 (1969).
so ,
50.
Found, Componentsb
1 N-Phenylhydroxylamine
Aniline 2 N-Phenylhydroxylamine Phenol Acetamide n-Butylamine 3 N-Phenylhydroxylamine Nitrobenzene Acetanilid 4 N-Phenylhydroxylamine C yclohexylhydroxylamine
M X 10-&
yo of Theory
1.496
99.75
=k 3 , 62c
1.489
99.27 i 1 . 5 9
1.485
98.97 f 2.50
1.514 100.90 i 1.81
Final concena Based upon 3 replicate determinations of each solution. tration of phenylhydroxylamine and all other components in mixtures was 1.500 X 10-5M;except aniline which was present in a final concentration of 1.500 X 10-3M. Confidencelimitsatp = 0.05.
groups react with 9-chloroacridine in typical nucleophilic displacement reactions, only primary arylamines produce any colored product under the conditions of the analytical reaction. Measurements reveal that arylhydroxylamines can be quantitated in the presence of a hundredfold excess of primary aromatic amine. Specificity permitting the determination of arylhydroxylamines with 9-chloroacridine in the presence of primary arylamines is obtained by measuring absorbance a t 450 nm, where the absorption characteristics of any 9-chloroacridine-arylamine adduct show minimal interference. Received for review September 10, 1973. Accepted November 20, 1973. This investigation was supported in part by NIH Grant CA-14158-01 from the National Cancer Institute.
CORRECT1ON Application of a Piezoelectric Quartz Crystal as a Partition Detector. Development of a Digital Sensor In a paper by Morteza Janghorbani and Harry Freund,
Anal. Chem., 45, 325 (1973), piezoelectric crystals for assay of SOz in air were described using carbowax as coating. This paper did not refer to the previously described, successful, studies on piezoelectric crystals for SOz, by G. G . Guilbault “Use of Tetrachlormercurate as a Coating for Son,’’ Enuiron. Lett., 2, 35 (1971), and the “Use of Piezoelectric Crystals as Sensitive and Specific Detectors for Son,’’ Anal. Lett., 5 , 255 (1972). The latter paper describes the use of carbowax as a coating for SOz, the same as discussed by Janghorbani and Freund.
A N A L Y T I C A L CHEMISTRY, VOL. 46, N O . 4, APRIL 1974
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