is slightly acid. An aliquot of this solution can be quantitatively analyzed for hydrazine by the above procedure provided that it does not contain more than 440 pg. of hydrazine. The results become increasingly negat'ively biased as the amount of hydrazine increases above this level. This probably is caused by the dimerimtion, a t higher hydrazine concentrations, of the electrode product diimide to tetrazine followed by the deeom2osition of tetrazine to ammonia and hydrazoic acid. This second-order tliinwization reaction has been shown by Karp and LIeites ( 2 ) to explain i-ariat,ions in t'he n value. K i t h 1 to 2 mg. of hydrazine in the cell, the bias was approx.mately -0.5%, even when the initial current \vas limited, by controlling i;he stirring speed, betn-cen 80 and 100 ma. to prevent spattering of solution by the copious nit rogcn evolution Measured coulombs were liucar with conc2ntration for the range of 55 to 440 pg. (0.31 t'o 2.15,-11 in a 5.5-inl. cell 1-olune) of hydrazine. LeI.els le..: than 55 p g , of hydrazine were not inr,e>tigated, The relative dant1:wl deviat,ion of the method is 0.09%, independent of concentration lei-el, bahed on 24 analyse; over the linear range of concentration and the method is not biased compared
to electrical calibration of the coulometer. Conditioning the platinum analytical electrode prior to analysis of each sample and adding the sample to the cell after the potentiostat was connected to form a n oxide coating on the anode were found to be very important factors governing the bias and precision. K i t h no surface renewal treatment, the oxide coating apparently changes from sample to sample, introducing an increasingly negative bias and imprecision. Changing the oxidation potential from +0.2 to 0.6 did not change the analysia value. Varying the sulfuric acid electrolyte concentration from 0.5 to 1.531 did not significantly change the results. .Immonium sulfate equal to 1.OX in the original sample solution (O.lJ1 ammonium sulfate in the cell) had no effect. I n testing for possible catalytic effects, the f i 4 o n gase., iodine and bromine, in trace quantities ( 5 X 1 O - * X in the cell) gave no detectable biah. Uranium dioxide, being filtered from the qample, was not considered to be a problem and was not inieitigated. If any carried through the filtration step, it would di+ solve as uranium(1V) which would coulometrically oxidize to gib e a quantitatire interference. S o other >ample component would b t e.rpected to interfere.
-1mercury pool analytical electrode with sodium hydroxide electrolyte was investigated. A negative bias of 2% with 1.8 mg. of hydrazine in the cell was observed. Because this negative bias increased with lesser amounts of hydrazine, it is believed due to the reaction of hydrazine with atmospheric oxygen in the baiic electrolyte. Because air-free sample5 are difficult to obtain. this approach was abandoned in favor of the platinum electrode procedure with the sulfuric acid electrolyte
+
LITERATURE CITED
(1) Booman, G. I,.> Holbrook, W. B., A 4 S CHEW ~ ~ ~ .35, 1793 (1963). ( 2 ) Karp, S., Meites, L., J . ;Ins. Chem. SOC.
84,906 (1962j.
(3) Pearson. R. L.. Standerfer. F. R.. Snvder. 'H. J.. Watanabe. ' H. T.. Carpenter, L. G., Miller, R.' I., U. S; Air Force Rept. ASD-TR-7-840 A ( V I ) . 1962. Available from Defense, Docu1
,
ment Center, Alexandria, Va. GLEVYL ROOKAS
WAYYEB. HOLBROOK
Phillips Petroleum Co. -4tomic Energy Division Idaho Falls, Idaho Work done under Contract S T ( 10-1)-205 to Idaho Operations Office, U. 9. Atomic Energy Commission. Work sponsored by the Aeronautical Systems Division, Airforce Systems Command, U. S.-4ir Force.
Determination of Acetaldehyde by Colorimetry SIR: A spot te*t for qualitative determination of acetz ldehyde has been knonn for many years ( 2 , s ) . It is based upon the reaction of s cetaldehyde with sodium nitroprusside and a secondary aliphatic amine, yielding a blue. watersoluble product. The chemistry of the reaction is not known. This communication reports a q iantitative colorimetric method ba.etl 3n a modification of the reaction. Tlii., modification, in which acetic acid 1. added t o the system, give< a pink color insi ead of blue, n ith a maximum ab.orptiori at 575 mp. The method detects acetaldehyde in concentration> as lon as 1 p.p.m.
a Lumetron Photoelectric Colorimeter, Model 402E (Photovolt Corp.) n i t h a 5-em. cell and 550-mp g1n.s filter. Distilled water was used to set 100%
Table I.
Interfering aldehyde Formaldehyde
EXPERIMENTAL
Calibration. Standards n-ere prepared in 100-1111. volumetric flasks so t h a t on dilution to vclume they would contain from 0 to 40 p.p.m. of acetaldehyde. I n addition, each flask contained 3.0 nil. of 2OY0 (v./v.) morpholine solution, 2 5 ml. of 10% (v./v.) acetic acid sol Ition, and 1.5 ml. of freshly prepared 2'7, (w./v.) sodium nitroprusside solution. After dilution to volume, the standrtrds mere allowed to stand 3 hours for c d o r development. At the end of this period, per cent transmittance data were obtained using
Propionaldehyde
transmittance. Khen the logarithm of the per cent transmittance mas plotted as a function of the acetaldehyde concentration. n qtraight line
Interference in Acetaldehyde Analysis
Reniarls Interferes by enhancing color formation, yielding high results when its concentration is above 10 p.p.m. Present in quantities over 500 p.p.m., color inhibition and low results occur. Interferes by enhancing color formation, giving high results. At 10-p.p.m. propionaldehyde, 30 p .p.m. acetaldehyde is analyzed as 33 p.p.m. while at 500 p.p.m. propionaldehyde, the analysis would be 40 p.p.m.
Interfering aldehyde Crotonaldehyde
Tiglaldehyde Acrolein
Glyoxal
Remarks enhancement and high results becomeserious between 100 and 500 p.p.m. crotonaldehyde. S o interference up to 500 p.p.m. Serious color enhancenient, leading to high results if present in greater than 500p.p.m. concentration. Color inhibition, giving low results, begins between 10 and 50 p.p.m. At 500 p.p.m., serious color enhancement is noted. Color
VOL. 35, NO. 12, NOVEMBER 1963
1987
calibration curve obeying Beer's law was obtained. Processing Aqueous Samples. An aliquot of the neutral aqueous sample is introduced into a 100-ml. volumetric flask. Samples which are acidic or basic must be neutralized. The size of the aliquot depends upon the amount of acetaldehyde present. Trial and error may be necessary to find a volume of sample which will give a result falling on the calibration curve. To the flask are added 3.0 ml. of 20% (v./v.) morpholine solution, 2.5 ml. of 10% (v./v.) acetic acid solution, and 1.5 ml. of 2% (w./v.) freshly prepared sodium nitroprusside solution. The
sample is diluted to volume, mixed thoroughly, and allowed to stand for 3 hours. Per cent transmittance is determined as for the calibration standards. The concentration of acetaldehyde is then read from the calibration curve. Concentration in the sample can be determined by multiplying the parts per million of acetaldehyde in the diluted aliquot by lOO/V, where V is the volume of sample in the aliquot,. Interferences. Several other aldehydes have been reported as interfering in the spot test for acetaldehyde ( I ) . To check their interferences in the quantitative colorimetric procedure, various concentrations of these aldehydes were
added to samples containing 30 p.p.ni. acetaldehyde, and per cent transmittance data n-ere obtained. The results are shown in Table I. LITERATURE CITED
(1) Doeuvre, J., Bull. Soc. Chim. (France.) 39, 1102 (1926). (2) Feigl, F., "Spot Tests in Organic Analysis," 6th ed. p. 352, Elsevier, 1960.
(3) Lexin, L., Chem. Be?. 32,388 (1899). DONALD J. CLAXCY DAVIDE. KRAMM
Research Division V.R. Grace & Co. Clarlisvjlle, hld.
Adaptation of a Gas Chromatograph for Analysis of Radioactive Gas Samples A. D. Horton, A. S. Meyer, Jr., and J. L. Botts, Analytical Chemistry Division, Oak Ridge National Laboratory, Oak Ridge, Tenn.
gas chromaA tographicfour-column assembly which operates COMPACT
by remote control was constructed for the analysis of radioactive gas samples. The assembly consists of a heated castaluminum cubicle with a hIicarta faceplate, a detector oven with a thermal conductivity (TC) cell, a sheet-metal cabinet that supports the cubicle and four chromatographic columns, and a gas-sampling apparatus. The assembly was designed specifically for the anaIysis of the hydrolysis products of neutronirradiated thorium carbides and uranium carbides. These samples contain high levels of beta and gamma activity emitted from Krs5 and XeX33and cannot be analyzed safely without escellent ventilation and moderate shielding. The assembly may be used to analyze any sample that can be introduced in the vapor state. Operation of any column in the assembly requires the positioning of only two valves and one selector snitch. The assembly (Figure 1) is located in a shielded area and is operated primarily by means of the control section of a Burrell Kromo-Tog gas chromatograph. Cables of convenient lengths connect the assembly to the control section. The assembly may be placed a t any desired angle without loss of operating efficiency. This flexibility makes possible the more efficient utilization of an available shielded area. The overall dimensions, including the column guards but excluding the sampling manifold, are 11 x 11 x 60 inches. The remotely controlled assembly is equivalent to the corresponding components of the Kromo-Tog in every way except that sampling is slower and the component parts are less accessible.
1988
ANALYTICAL CHEMISTRY
The following items, available from Burrell Corp., Pittsburgh, Pa., were used in the construction of this assembly: columns, 2.5 ft. long by 0.5-em. i.d., wire-wound U-tubes, Cat. KO., 347-01-25; packing (used to obtain the
results shown in Table I), mediuniactivity silica gel, 30- to 60-mesh, modified n-ith 3 wt. % squalane; detector oven for RIodel K-2 Kromo-Tog; gas sampler, Cat. KO.347-3-0; column guards for Model K-2 Kromo-Tog;
,9
, , %.
"
/
THERMOCOUPLE I AND COLUMN H E A T E R SELECTOR)'
i,' \ ~ . w ~ yV
'
O ~ ~TOE D E T E ~ T C R
'THEFMCCCIIPLE
Figure 1.
CPBLE
Four-column gas chromatographic assembly
