Alternate Techniques for Performing Extractions Daniel A. McLean California Water Service Company, I720 North First Street, San Jose, Calif. 951 72
EXTRACTIONS ARE USUALLY performed in separatory funnels. When a large number of samples are extracted, shaking the separatory funnels becomes a time-consuming, tiring job. Also, sample handling becomes cumbersome if multiple extractions are to be performed with solvents that are less dense than water. Mechanical shakers are available but are expensive and are not suited for large samples. To overcome these disadvantages, the author has investigated several other techniques for performing extractions. Morgan ( I ) has suggested the use of Babcock bottles as extraction vessels. These bottles are useful if the sample volume does not exceed 50 ml and they can be used in mechanical shakers. However, the small sample size severely limits their usefulness. In addition, centrifugation of the extract is often necessary and Babcock bottles cannot be used in a small centrifuge. One scheme that works well uses an ordinary filtering flask for the extraction vessel. The sample and the extractant are placed in the flask and the sample is extracted by stirring on a magnetic stirrer. The stirrer is run at a speed that will form vortex deep enough that the organic phase is drawn down to the stirring bar. The stirring action will then disperse the organic throughout the aqueous phase. Two minutes stirring in this fashion is fully as effective as two minutes shaking in a separatory funnel. After the phases have separated, the organic layer may be discharged through the side tube of the flask into a suitable container (centrifuge tube, cuvette, etc.) by adding water to the flask below the interface of the two phases. This may be done with a pipet or a wash bottle. With careful manipulation, virtually all of the organic phase can be recovered with very little carryover of water. Several extractions may be (1) M . E . Morgan, A t . Absorption Newslert., 3,43 (1964).
Figure 1. Apparatus for extraction of solvents more dense than water performed simultaneously using a magnetic stirrer with the capability of stirring several flasks at once. With solvents that are more dense than water, the extraction can be performed as described above using a polyethylene bottle as the extraction vessel. The organic phase is discharged through a glass or polyethylene tube by squeezing the bottle. The apparatus is shown in Figure 1. If it is desired to use a glass vessel for the extraction, a rubber bulb may be used to supply air pressure to force the organic phase up the outlet tube. RECEIVED for review November 23, 1970. Accepted December 15, 1970.
Concentrating Flask for introduction of Micro Samples to a Mass Spectrometer via the Solids insertion Probe D. R. A. Wharton and M. L. Bazinet Pioneering Research Laboratory, U. S . A r m y Natick Laboratories, Natick, Mass. 01760
WHENONLY TRACE QUANTITIES of material are available for mass spectrometry and it is necessary to apply the total sample for an analysis, it may be difficult to collect the sample without the use of a solvent and its attendant risk of contamination. This article describes a device that enables the concentration, without contamination or loss, of even minute amounts of material and its direct introduction to the mass spectrometer by means of the solids insertion probe. Nanogram quantities of ethyl myristate have been determined routinely with the Consolidated 21-110 mass spectrometer, and the device is applicable to the Perkin-Elmer 270 mass spectrometer and instruments with similar probes. The device (Figure 1)
consists of a pear-shaped glass flask which has the distinctive characteristic of tapering to a closed tube of such diameter (about 2 mm 0.d.) as to fit within the probe which applies the sample to the spectrometer. The length of the tube is not crucial, but preferably it should be longer than the receptacle of the probe. When drying the sample, repeated refluxing or washing do,wn of the material adherent to the wall of the flask is essential to secure its total concentration in the tube. After the sample has been concentrated to dryness in the tube by appropriate means, the outside of the tube is cleaned and the tube then cut to a length no longer than the receptacle of the probe, placed in the probe, and introduced into the ANALYTICAL CHEMISTRY, VOL. 43, NO. 4, APRIL 1971
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