Aut om ated Determination of Trace Carbonyl s S. A. Bartkiewicz and L. C. Kenyon, Jr., Esso Research Laboratories, Humble Oil & Refining Company, Baton Rouge, La.
the analytical demands of research and developmental vhich i t serves, the routine analysis laboratory a t times must carry out large numbers of repetitive analyses. These analyses are, on occasion, both time-consuming and tedious. One such determination is that of trace carbonyl compounds in organic and aqueous solvents. Automation of analyses of this nature should result in reduced operating costs and in faster analyses. Analytical precision and accuracy would probably improve since automation should eliminate inaccuracies due to personal errors. Becauie of its simplicity, we investigated the method of Lappin and Clark (1) for automation using the Technicon Autohnalyzer. A successful method has been developed which is simple, rapid, and accurate and requires little operator attention. Y MEETIXG
I-the groups
EXPERIMENTAL
Apparatus. A standard Technicon AutoAnslyzer. manufactured by Technicon Controls, Inc., was used in carrying out all developmental studies. T h e equipment consists of a sampling module, disposable sample containers, proportioning pump, organic solventresistant Tygon tubing, caustic-resista n t silicone rubber tubing, glass mixing coils, constant temperature heating bath, time delay coil, dual beam filter photometer, and a ratio recorder. Both types of tubing are supplied by Technicon under the names of Solvafles and Silastic, respectively. Photometric measurements were made using a matched set of Corning 535 mp
Table
interference filters and a 3-mm. flowthrough cell. Reagents. Carbonyl-free ethanol, purified as described b "v Latmin . I and Clark (1). Alcoholic potassium hydroxide. One gram of potassium hydroxide was dissolved in 30 ml. of distilled water and the solution was made u p to 100 ml. with methanol. This solution will keep indefinitely. 2.4 - Dinitroohenvlhvdrazine - hvdrochloride ( D N P H . HCT). A solhion was prepared by dissolving 0.1 gram of reagent grade 2,4-dinitrophenylhydrazine in 50 ml. of carbonyl-free ethanol. T o this was added 1 ml. of concentrated HC1 and the solution was made up to 100 ml. with purified ethanol. This solution is stable for several days. Procedure. Calibration standards, covering t h e range from 0 t o 0.6 carbonyl number, were prepared from Eastman highest purity heptaldehyde and carbonyl-free ethanol. A manifold consisting of t h e proper flow capacities, Figure 1, was prepared from Solvaflex for metering of sample, ethanol diluent, and D K P H . HCl. T h e lines for metering alcoholic potassium hydroxide were made of Silastic. I n preparing the automatic analyzer for operation, the sampler module is bypassed and the sample line is placed into the ethanol diluent container with the ethanol line. The lines for alcoholic potassium hydroxide and D N P H ' H C I are placed into their respective flasks. The instrument is turned on and is permitted to come to equilibrium-Le., the instrument is warmed up and all lines are filled with sample and reagents. This takes approximately 15 minutes. While the instrument is equilibrating, the sampling module is alternately filled with stand-
Carbonyl Procedure
Av. Std. dev.
Carbonyl number Extraction Automethods ( 8 ) Analyzer
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Sample A" Sample B5 See Table I.
0.23 0.28 0.24 0.27 0.29 0.27 0.70 0.35 1.78 1.30 0.74 0.10 0.99 0.82 3.23 0.47 0.60 2.80
0.23 0.26 0.25 0.27 0.24 0.20 0.60 0.36 1.62 1.31 0.67 0.07 1.oo 0.81 3.60 0.38 0.62 2.82
( 0 32 ML. /MIS.
MIXING
0.62 10.06
2.81 2.86 3.09 2.92 2.87 2 61 2.64 2 71 2 78 2.87 -
I+
t
2.82 zt0.16
DISCARD
Figure 1 .
422
Sample no.
Carbonyl number Sample A Sample B
0.58 0.57 0.61 0.59 0.59 0.63 0.56 0.59 0.72 0.69 -
6 7 8 9 10 11 12 13 14 15
Table 11. Accuracy of Automated Trace Carbonyl Procedure
r; 7 SAMPLE
I. Precision of Automated Trace
Replicate
ards and purified ethanol. After the instrument has equilibrated, the sample line is connected to the sampling module, the colorimeter and recorder are standardized, and automatic operation is begun. Samples are fed to the instrument a t the rate of 1 every 3 minutes. A calibration curve is obtained by plotting absorbance us. concentration. Samples of unknowns are run as described in the above procedure. Carbonyl-free alcohol blanks are placed between samples to prevent possible contamination between analyses because of the high wetting properties of the organic system. Occasional standards are run to check the calibration of the instrument. Concentrations of the
ANALYTICAL CHEMISTRY
Flow diagram of automated trace carbonyl procedure
unknowns are determined from the previously prepared calibration curve. RESULTS AND DISCUSSION
Precision of the method at two carbonyl levels is shown in Table I. D a t a for this study, accumulated over a period of several weeks, can be compared with those of the manual method concurrently used in our laboratory. Long term precision, 20, for the manual method, 40 analyses, is 1 0 . 0 1 4 a t a carbonyl number of 0.026. Samples A and B which were used in establishing the precision of the automated procedure were prepared from crude oxo alcohols which had been dissolved in pure decyl alcohol.
Table I1 shows the results of a crosscheck program using the extractive method of Lohman ( 2 ) as referee. The samples used in the study were actual plant samples of oxo alcohols. Agreement between the two methods is excellent. Because the samples used in these studies all had specific gravities which varied within a few per cent of one another, no correction for changes in specific gravity was made in the analytical calculations. Where large changes in specific gravity of the samples are encountered, corrective measures should be taken. The automated procedure is being used in our analytical laboratories for routine analyses. On a single sample, elapsed time per analysis is less than
1 hour. For samples in groups of 10 or more, time per sample is about 0.1 hour. The system can handle as many as 70 to 80 samples per 8-hour day Ivith a minimum of operator attention. ACKNOWLEDGMENT
The authors thank Boyd D. Crum for his cooperation and suggestions in carrying out these studies. LITERATURE CITED
( I ) Lappin, G. R., Clark, L. C., AKAL. CHEW.23,541 (1941). (2) Lohman, F. H., lbid., 30,972 (1958).
Southeastern Regional Meeting, .4CS, Gatlinburg, Tenn., Sovember 1962.
Apparatus for the Determination of Particle Density of Porous Solids Fred 0. Cartan and George J. Curtis, Atomic Energy Division, Phillips Petroleum Co., Idaho Falls, Idaho
a nonporous particle T is, in general, a function only of its composition. The density of a porous HE DEXSITY OF
particle, however, may be a function of its porosity as well. Porous particles can be considered to have two densities depending on the value used for the particle volume. One can define two volumes for an individual particle. The porous value is the total volume of the particle, including the volume of the pores on and within the particle, while the nonporous value is only the solid volume. The density calculated using the porous value can be called the particle density. This particle density is needed to calculate particle porosity and is a useful parameter for studies of the behavior of fluidized beds. The usual pycnometric liquids cannot be used to measure the particle density. They penetrate the particle pores, resulting in a measured volume approaching the nonporous value. Because most porous particles are not wet b y mercury, this penetration can be eliminated by using it as the immersion liquid (1-8). A convenient apparatus for the mercury displacement measurement has been built. It consists of a pycnometer, a pressure chamber, and a filling device. The pycnometer is a simple modification of a commercially available mercury penetrometer cell. The pressure chamber and filling device are easily constructed. The measurement is based on conventional pycnometry. The pycnometer volume is calculated from the
weight of mercury needed to fill it. The sample volume is obtained from the difference between this weight and the weight of mercury needed t o fill the pycnometer with the sample present. Since mercury will be forced from the calibrated stem of the pycnometer into the solids when pressure is applied, a correction, equal to the unoccupied stem volume, is subtracted from the apparent solids volume.
SUPPORT
fYLLrn
EXPERIMENTAL
Apparatus. pycnometer (Figure 1) : T h e penetrometer cell (American Instrument Co., Catalog No. 5-7147) is a ready made pycnometer. It is sturdy, easily cleaned, and assembled, but, a s purchased, is too long for convenient weighing on a n analytical balance. T o correct this, a section of t h e capillary just below t h e sample chamber was removed and t h e reniaining portion was sealed back into position. 4 wire support loop was added so that the pycnometer could be hung from the balance pan hooks. The over-all length, assembled, is about 8 inches. When the pycnometer is sealed, matching marks are scribed on the inner and outer seal fittings. A reproducible volume is obtained by rotating these marks into alignment each time the iivcnometer is reassembled. Pressure Chamber (Figure 2) : This easily constructed deviFe alldws observation of the position of the mercury meniscus inside the pycnometer stem at pressures as high as 100 p.s.i. The basis of the chamber is a n inexpensive vacuum coupling (Cenco 94235-6) which provides a tight demountable seal. l
y
Figure 1.
Pycnometer
The upper and loiT-er blocks were turned from 1.5-inch diameter brass rod stock and were silver soldered into the coupling. The glass pressure tubing is held between gaskets and a n O-ring inside a slotted brass guard tube. This allows a direct view of the calibrated stem of the pycnometer. The guard tube is silver soldered to the upper block. A needle valve provides the necessary vent. Cylinder nitrogen has been used as the pressure source, however, any controlled source of conipressed air or inert gas is suitable. Filling Device (Figure 3) : This device VOL. 35, NO. 3, MARCH 1963
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