ANALYTICAL CHEMISTRY
1178 Table I.
Nonaqueous versus Aqueous Methods Known W t . 70 0 0020
Acetic acid in purified acrylonitrile
0 0035
C oniniercial acrylonitrile I
6
Found W t . % Nonaqueous” Aqueousb 0.0020
0.0040
0 OD60 0.0070
0.0030
0.0110 0.0120 0.0140
DATA AND DISCUSSION
Indiestor titration, bromotl.ytii~d :.:,I?.. l:iLiirator titrstion. phenol~.l.rhalcin.
Table 11. Indicatora litrations Known Acetic acid in acrylonitrile
.-1 rrylic arid in acrylonitrile
0.0020 0 0032 0.0071 0 0120
0.0013 0.0028 0.0066 0.0085
Clloline in acrylonitrile
Basic choline salt in acrylonitrile
0.0020
0.0041 0.0069 0.0114 0.0015 0 . on35
0.0008 0.0010
0,0020 0,0040 0 . no80 0.0047
0.0040
0.0089
0.0083 0.0083 0.0078
on05
0.009i
0.0132 0.020,i a
V-eight % Found
0.0062 0.0080 0.0003 0.0008 0.0011 0.0016 0.0031 0.0072
o
0.0036
0,0119 0 0203
Abs. error 0.0000 0.0009
0.0002 0.0006 0.0002 0.0007 0.0004 0.0005 0.0002
0.0000 0.0001 0.0004 0.0009 0.0008
0.0007
0.0011 0.0006 0.0006
0.0017 0.0013 0.0002
Bromothymol blur indicator.
Table 111. Statistical Data Range Found, Wt. % Acetic Acid
KO.of Detn.
Std. Del..?, Wt. %
Commercial acrylonitrile
0 0004-0 0009b
8
0.00014
Acrylonitri!e plus 0.0044% of acetic acid
0 0047-0 0030b
3
0.00015
0 0094-0 0099; 0 0079-0 0083
7
0.00020 0 00019
Acrylonitrile plus 0.0088% acetic acid a
b
the p H is returned to the original value. The titrant equivalent required for this operation is then calculated. I n the titration of weaker bases than choline, such as carboxylic acid salts of choline, the preferred potentiometric solvent is C.P. acetic acid with standard perchloric acid in acetic acid or dioxane as the titrant. For weak bases, plot the readings from the electromotive force scale, rather than pH, against titrant volume and determine the end point as the increment of titrant causing the largest potential change.
The usual aqueous methods of titrimetry were applied to the first samples studied. This was done by diluting acrylonitrile with 15 volumes of distilled water, followed by blank correct,ions for carbon dioxide present in the water. Although carbon dioxidefree water was used, and care was t,aken to minimize carbon dioxide absorption during the titrations, the blanks were high compared to the acid and base concentrations expected. The simpler nonaqueous procedures gave more reasonable values when applied t o purified (redistilled) acrylonitrile to which small amount,s of choline or acrylic acid had been added. Table I indicates the recoveries of acetic acid by both aqueous and nonaqueous methods. The procedures described gave very satisfactory recoveries. Table I1 relates experimentally determined values to calculated amounts of acetic and acrylic acids and choline as well as choline salts. The variations found were generally less than 0.001 n-eight yo and exhibit’ed no const,ant bias in the cases of acids and strong bases. However, in the case of weak bases, the results were frequently low., occasionally by as much as 0.0015 weight %, which was within the precision required for routine determinations during this study. The precision, defined as the standard deviation a t the 1-u level, of several samples is shown in Table 111. These show the precision to be 0.0002 weight yofor this series of samples. LITERATURE CITED
7
Standard deviation a t 1-u level. Indicator (bromothymol blue) titrations. Potentiometer (G-H solvent) titrations
Dyer, W. J., J . Fisheries Research Board of Can., 6, 351 (1945). (2) Jacobs, M. B., and Scheflan, L., “Chemical Analysis of Industrial Solvents,” pp. 209, 299, Interscience, New York, 1953. (3) Keen, R. T., and Fritz, J. S., ANAL.CHEM., 24, 564 (1952). (4) AIarkunas, P. C . , and Riddick, J. -4., Ibid., 24,312 (1952). (5) Palit, S. R., ISD. E N G .CHEY.,ANAL.ED.,18, 246 (1946). (6) Pifer, C. TV., and Wollish, E. G., ANAL.CHEM.,24, 300 (1952). (7) Seaman, W., and Allen, E., Ibid., 23, 592 (1951). (1)
RECEIVED for review December 11, 1934. Accepted January 31. 1935. Presented a t the Southwestern Regional AIeeting of the SOCIETY. Fort Worth, T e r . , Decemher 2 , 19.j4.
. ~ M E R I C ~C SHE~IICAL
Circular Paper Chromatographic Method for Estimation of Thiamine and Riboflavin in Multivitamin Preparations K. V. GlRl and S . BALAKRISHNAN Department o f Biochemistry, lndian lnstitote of Science, Bangalore 3, lndia
A simple circular paper chromatographic method has been developed for the separation and simultaneous estimation of vitamins Bi and B2in niultivitamin preparations.
T
HE separation, identification, and quantitative estimation of B-complex vitamins bv paper chromatography has been drawing the attention of inany workers in recent years. Beran and Sicho ( 2 ) reported the conversion of thiamine into thiochrome on paper by treatment with alkaline ferricyanide and detected it by its blue fluorescence under ultraviolet light. Miyaki and
others ( 1 2 ) described a procedure by which the thiamine in 95% ethyl alcohol containing logo sodium hydroxide was chromatographed and identified by spraying with diazotized p-aminoacetophenone and alkali, and applied this procedure for the quantitative estimation of thiamine by an area method. Fried ( 5 ) suggested a paper electrophoretic separation of thiamine from other fluorescent substances. ,4paper partition chromatographic method was described by Crammer ( 4 ) for the eeparation and identification of riboflavin and other flavine compounds. Hais and Pecakova (9) used this method for following the photolpsis products of riboflavin and applied it for the analysis of commercial injection solutions.
V O L U M E 27. NO. 7, J U L Y 1 9 5 5
1179
A method for the paper chromatographic repamtion and determination of Some water eoluble vitamins suitable for the analysis of multivitamin preparations was reported by Brown and Marsh ($1, who measured the areas of discrete zones of total ultraviolet absorption with the help of a Cary spectrophotometer. Radhakrishnamurty and Sarma (14) reported the separation of various members of the B-complex vitamins by ascending paper chromatography and identified the individual vitamins on the paper by specific spot tests. Recently, Gin (7) described briefly a simple method for the estimation of thiamine and riboflavin by circular paper chromatography.
powder was first digested with 30 ml. of water containing a few drops of gh&I acetic acid (to facilitate the dissolution of rib* flavin) bv heatine on a water bath for 0.5 hour. The extract was allo
