mounted in the other position. Even there a brief pre-spark brought the magnesium response down to its intrinsic level. Analytical Results. Tables I, 11, and I11 show data obtained on three different sample types using the dual electrode pair arrangement. Integrations were taken in the order shown under each element. Analyte integrations were alternated with those of the standard for repetitive comparison. The data are from consecutive analyses of the three materials and represent truly typical obtained data. Precision difficulties may appear more often in the compacted samples if extreme care is not taken in the preparation. The small amount of sample consumed puts severe demands on sample homogeneity. Because no other standard biological sample was available to compare to the NBS orchard leaves, duplicate electrode pairs were prepared from the orchard leaves with one pair assigned as the standard and the other as the analyte pair. Advantages of Dual Electrode Pairs. The quantitative analysis difficulties with SSMS in the past are well known. Electrical detection and integration now allow quantitative respectability for SSMS, but our experience has been that extremely close parameter control is necessary. It is not at all unusual to see integration changes of 30-50 with slight changes in electrode alignment and shielding. Changes in magnet current, acceleration-€SA voltages, or vacuum conditions may also produce time dependent differences. With dual electrode holders, the time between sampling of the standard and analyte is quite $mall and rechecks of any particular element us. the standard can be made at any time before the total analysis is completed. In our laboratory,
this has resulted in more precise and accurate data than using a standard pair to take integrations for a series of elements, followed by breaking vacuum, replacement with the analyte pair, and then obtaining integration values for each element in the analytical sample. This is not to suggest that accurate and precise data cannot be obtained by the conventional single electrode pair approach (3, but data can be obtained more rapidly with the dual-electrode holders and, of greater significance, more frequent cross checks can be made between sample and standard. F o r applications which d o not involve peak switch integrations, the dual holders are also useful. In photographic readout using an internal standard, overall turn around time for a series of samples can be cut in half by mounting two sets of analyte electrodes in each loading. The same would be true for the magnetic scanning survey mode (8). With respect to the latter, we have used the dual holders to mount a standard and analyte pair and scanned each set, thus using external standards rather than one internal standard. Specifically, the recently issued NBS orchard leaves standard has many elements at reasonable concentrations to compare t o drug samples, such as marihuana and opium, which are of interest in our laboratory. RECEIVED for review March 24, 1972. Accepted June 29, 1972. Thii study was supported by EPA Grant 16020 HGI and LEAA Grant 154. (8) R. Brown and P. G. T. Vossen, ANAL.CHEM.: 42,1820 (1970).
Economical Fluidized Drier for Gas Chromatography Packing Material P. C. Goodley and Marshall Gordon Department of Chemistry, Murray State Unicersitjq, Murray, K J . 42071
THEEFFICIENCY of gas chromatographic columns is a n important concern to the gas chromatographer who runs routine analysis. After many sample injections (especially where trace harmful materials might be included in the samples), the columns tend to lose resolution and become less efficient. Responding to this situation, the GC analyst can either purchase new columns o r resort to their construction, which is more economical. For a n institution such as the authors’ laboratory, the more economical way is often the better. Also, it offers more versatility when one is choosing a column for a specific analysis (any length or diameter can be readily available in a short time). The construction and preparation of the column often presents t o the chromatographer the problem of being able to duplicate the previous column giving its exact analysis and retention times for specific compounds. This problem is present often, even though all steps involved in the preparation of the column were duplicated from past records. From past experience in our laboratory, this difficulty can be eliminated by the use of the fluidized drier ( I ) . (1) R. F. Kruppa, R. S. Henly, and D. L. Smead, ANAL.~ H E M . , 39, 851 (19h7).
FLUIDIZER BASE PLATE
A
MATERIAL AL
DRILL 8 TAP FOR PIPE
g
$DRILL
L
a
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SEC. AA
Figure 1. Fluidizer base plate
ANALYTICAL CHEMISTRY, VOL. 44, NO. 14, DECEMBER 1972
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Part A
B C
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Table I. List of Materials and Parts for Fluidized Drier (Figure 2) No. 1 Bathroom sink drain pipe (chromium plated brass or SA) 11/4-in.0.d. except at base which is expanded to 13/~-in.0.d. with ll/z UNF thread. Mfgd by Sterling Tube Co. 1 Kimax fritted disk, 40-mm 0.d. medium porosity, Cat. No. 28280. 1 Pc. alum. tube-ll/$ inch long by 3/~-in.0.d. (for t hermowell). 1 Pc. aluminum round stock or flat plate, 41/2 inch in diameter or square by 3 / 4 inch thick. Bore out to ll/>inch and thread to 12 UNF inside to fit drain tube. 1 Brass fitting male pipe to l/s-in. tube (any appropriate connector to dry nitrogen or air supply).
Parcher and Urone ( 2 ) used a special glass coating and drying type of fluidizer to show that uniform and reproducible coating of the support material could be obtained. The information shown by Kruppa, Henly, and Smead ( I ) , which gave the column efficiencies of the tray-dried packing cs. the fluidized bed-dried packing material, demonstrated the superior performance of the fluidized drying technique. The materials are listed in Table I, and most of them can be obtained from local hardware stores or welding shops. The base plate shown in Figure 1 is the item of major cost. I t can be made from any aluminum plate having at least a L/8-inchthickness ( 3/r-inch is recommended). The base plate has to be machined to fit the bathroom sink drain tube which is l1i2inches UNF thread. Figure 2 shows a pictorial view, and the remainder of the parts can be assembled accordingly.
The exact version of the fluidizer described herein has been used consistently in our laboratory for the past three years with much success in duplicating and reproducing G C packing materials, and all for a very modest cost. The use of the fluidizer is as follows. The fluidizer is placed o n a hot plate and a source of dry nitrogen or helium is connected to the gas inlet. The fluidizer is heated on a hot plate from 45 to 55 “ C ; the temperature is measured by a thermometer inserted into the thermowell in the base plate of the fluidizer. The high mass of the base plate allows a sufficient heat transfer to warm the incoming gas which helps dry the packing material. Freshly coated packing material is placed into the fluidizer and the gas flow adjusted to give a low fluidizing effect. As the packing material approaches dryness, the gas flow should be decreased to avoid a high rate of attrition of the particles. The drying time will depend on the solvent used; for dichloromethane, about five minutes is adequate. The packing material after drying, may be used a t once.
(2) J. F. Parcher and P. Urone, J. Gas C/zvomatogr., 2, 184 (1964).
RECEIVED for review June 5, 1972. Accepted July 27, 1972.
Figure 2. Exploded pictorial of fluidized drier
Thin-Film Sorbents for Obtaining Acridine Dye Spectra J. J. Sjoblom 6303 Lake Road West, Ashtabula, Ohio 44004 chloroform and one of 96% ethanol ( I ) . The dipped cover FORTHE PURPOSE of obtaining absorption and luminescence glasses were drained for 2 hours, in a covered jar full of chlorospectra of acridine dyes sorbed by cellulose acetate or silica form vapor, then allowed t o dry in a crystallizing dish out of gel, methods were worked out for preparing thin films of these which chloroform had just been poured. After 6 hours of sorbents on glass. A minimum of light scattering was evacuation of these plates at room temperature (elevated temachieved by these matrices. The acridine dye sorbed by and peratures apparently shrink the films so that sorption of dye tested on these films was trypaflavine ( C I I H ~ ~ N I . C H ~ C ~ . H C ~does ) . not take place), they were immersed for 30 minutes in 4 Thin-film preparations and sorption conditions are specified 10-4M trypaflavine solution and rinsed in water. The below. The spectral results in the absence and presence Of cellophane skin was wrinkled while wet, but smooth after oxygen will be indicated briefly. drying. CELLULOSE ACETATE FILMS ON GLASS Dry, clean rectangular cover glasses for microscopic slides were dipped in a 3 % solution of E K cellulose triacetate (tetrachloroethane-soluble) in a solvent made u p of 9 volumes of 2416
a
(1) H. N. Holmes, “Laboratory Manual of Colloid Chemistry,” 3rd ed., John Wiley & Sons, New York, N.Y., 1934, p 21.
ANALYTICAL CHEMISTRY, VOL. 44, NO. 14, DECEMBER 1972
