Extraction conical vial

Three types of apparatus are used for extractions conical vials, centrifuge tubes, and separatory funnels. These are shown in Figure 12.4. Conical vials may be used with volumes of less than 4 mL volumes of up to 10 mL may be handled in centrifuge tubes. A centrifuge tube equipped with a screw cap is particularly useful for extractions. The separatory funnel is used in large-scale reactions. Each type of equipment is discussed in a separate section. 

Evaporate the toluene fraction from Paragraph 9.10.5 to approximately 1.0 mL in a rotary evaporator (see Section 9.8). Transfer the extract to a 2.0 mL conical vial using a toluene rinse. 

Dilutions are performed using an aliquot of the original extract, of which approximately 50 pL remain from Paragraph 9.11.2. Remove an appropriate size aliquot from the vial and add it to a sufficient volume of tridecane (or nonane) in a clean 0.3 mL conical vial. Add sufficient recovery standard... 

Instead of a sep funnel, you use a conical vial and some Pasteur pipets. First you mix your extraction solvent with your product then you separate the two liquids. 

Get the material to be extracted into an appropriately sized conical vial. This vial should be at minimum twice the volume of the liquid you want to extract. Usually, this conical vial is the reaction vial for the experiment, so the choice is easily made (forced on you). 

LEE results in the extraction of the analyte into a relatively large volume of solvent which can be concentrated using a rotary evaporator to a few milliliters. Further concentration to a few himdred microliters can be carried out by passing a gentle stream of pure gas (usually dry Nj) over the surface of the extract contained in a small conical vial. The solvent-evaporation method is slow and has a risk of contamination. Micro-extractors have been described, and have the advantage of avoiding the further concentration of organic solvents [ 179, 180,190,192]. 

Allow the undissolved portion of the powder to settle in the vial. A cloudy suspension may remain even after 5 minutes or more. You should wait only until it is obvious that the larger particles have settled completely. Using a filter-tip pipette (Technique 8, Figure 8.9), transfer the liquid phase to a centrifuge tube. Add a second 2-mL portion of methanol to the conical vial and repeat the shaking process described previously. After the solid has settled, transfer the liquid phase to the centrifuge tube containing the first extract. 

Collect all the distillate in a 15-mL screw-cap centrifuge tube. Using a calibrated Pasteur pipette (see Experiment 1), add 2.0 mL of methylene chloride (dichlo-romethane) to extract the distillate. Cap the tube securely and shake it vigorously with frequent venting. Allow the layers to separate. Using a Pasteur pipette, transfer fhe lower mefhylene chloride layer to a clean, dry, 5-mL conical vial. Repeat this extraction procedure two more times with fresh 1.0-mL portions of methylene chloride and combine all the methylene chloride extracts in the same 5-mL conical vial that you used for the first extraction. If there are drops of water in the vial, it will be necessary to transfer the methylene chloride solution with a dry Pasteur pipette to another dry conical vial. 

After the mixture has cooled, extract it with three 1-mL portions of methylene chloride (Technique 12, Section 12.4). Add the methylene chloride, cap the vial, shake it, and then loosen the cap. When the layers separate, transfer the lower layer with a filter-tip pipette to another container. After completing the three extractions, discard the aqueous layer and return the three methylene chloride extracts to the vial. Extract the methylene chloride layers with a 1-mL portion of 5% aqueous sodium bicarbonate. Transfer the lower organic layer to a clean, dry conical vial. Discard the aqueous layer. Dry the organic layer over anhydrous sodium sulfate (see Technique 12, Section 12.9). When the solution is dry, transfer it to a clean, dry, 3-mL, conical vial with a filter-tip pipette. Evaporate the methylene chloride using a warm water bath (40-50°C) in the hood. A stream of nitrogen or air will accelerate the evaporation (Technique 7, Figure 7.17A). The product may be stored in the capped vial and saved for the next period, or it may be distilled under vacuum during the same period. 

A generalized extraction process that uses a conical vial is illustrated in Figure 12.1. The first solvent contains a mixture of black and white molecules (Figure 12.1 A). A second solvent that is not miscible with the first is added. 

Before using a conical vial for an extraction, make sure that the capped conical vial does not leak when shaken. To do this, place some water in the conical vial, place the Teflon liner in the cap, and screw the cap securely onto the conical vial. Shake the vial vigorously and check for leaks. Conical vials that are used for extractions must not be chipped on the edge of the vial or they will not seal adequately. If there is a leak, try tightening the cap or replacing the Teflon liner with another one. Sometimes it helps to use the silicone rubber side of the liner to seal the conical vial. Some laboratories are supplied with Teflon stoppers that fit into the 5-mL conical vials. You may find that this stopper eliminates leakage. 

In some cases, adequate mixing can be achieved by spinning your microspatula for at least 10 minutes in the conical vial. Another technique of mixing involves drawing up the mixture into a Pasteur pipette and squirting it rapidly back into the vial. Repeat this process for at least 5 minutes to obtain an adequate extraction. 

The 5-mL conical vial is the most useful piece of equipment for carrying out extractions on a microscale level. In this section, we consider the method for removing the lower layer. A concrete example would be the extraction of a desired product from an aqueous layer using methylene chloride d = 1.33 g/mL) as the extraction solvent. Methods for removal of the upper layer are discussed in the next section. 

Transfer the withdrawn organic phase into a dry test tube or another dry conical vial if one is available. It is best to have the test tube or vial located next to the extraction vial. Hold the vials in the same hand between your index finger and thumb, as shown in Figure 12.6. This avoids messy and disastrous transfers. The aqueous layer (upper layer) is left in the original conical vial (Figure 12.5E). 

Removing the Upper Layer. Suppose we extract an aqueous solution with diethyl ether (ether). This solvent is less dense than water and will rise to the top of the conical vial. Use the following procedure, which is illustrated in Figure 12.7, to remove the upper layer. 

D. The aqueous layer is transferred to a test tube or conical vial. The ether layer remains in the original extraction vial. 

Solvents other than those in Table 12.1 may be used for extractions. Etetermine the relative positions of the organic layer and the aqueous layer in a conical vial or separatory funnel after shaking each of the following solvents with an aqueous phase. Find the densities for each of these solvents in a handbook (see Technique 4). 

A common technique for isolating and purifying the product of a chemical reaction involves liquid-liquid extraction, or simply extraction the theory and applications are discussed in Chapter 5. This process involves transferring a solute from one solvent into another, because of its greater solubility in the second. The two solvents must be immiscible and form two distinct layers, and in general one layer is aqueous and the other is an organic solvent such as diethyl ether, hexane, or dichloromethane. Depending upon the amounts of material, the physical separation of the two immiscible phases will be performed in separatory fuimels or conical vials. 

The volumes of solvent are too small to use separatory funnels for extractions when reactions are conducted on a microscale level. In these instances, conical vials may be employed for volumes up to about 4 mL, and screw-cap centrifuge tubes may be used for volumes up to approximately 10 mL (Fig. 2.63). To avoid accidental spills, place the conical vial or centrifuge tube in a small beaker when you are not handhng it. 

Before using either a conical vial or a centrifuge tube for an extraction, ensure that it does not leak when shaken. This may be done easily by placing about 1 mL of water in the vial or tube and screwing the cap on securely. Shake the vial or tube vigorously and check for leaks. 

Extracting an aqueous solution using an organic solvent such as diethyl ether that is less dense than water (a) the desired product is in the aqueous solution (h) the aqueous phase is extracted with diethyl ether (c) the lower (aqueous) phase is withdrawn (d) the aqueous phase is transferred to a test tube the ether layer remains in the conical vial (e) the ether phase is transferred to a test tube, and the aqueous phase is returned to the extraction vial. 

Place an empty test tube or conical vial adjacent to the extraction vial. You will need a beaker or test tube rack to hold a test tube. Attach a rubber bulb to a Pasteur filter-tip pipet (Fig. 2.9a), squeeze the bulb, and insert the tip of the pipet into the vial until it touches the bottom. Slowly withdraw the lower aqueous layer into the pipet while keeping the tip of the pipet on the bottom of the conical vial (Fig. 2.64c). Be sure to avoid transferring any of the organic layer or any emulsion that may remain at the interface of the two phases. Although a regular Pasteur pipet may also be used for this transfer, a filter-tip pipet is sometimes easier to control when removing small volumes of aqueous phase from the vial. 

Transfer the aqueous phase you have drawn into the pipet into the empty test tube or conical vial, leaving the ether layer behind in the extraction vial (Fig. 2.64d). It is best to position the second container as close as possible to the extraction vial to avoid messy transfers and loss of your product. 

Decant about one-half of the ethereal solution into a 5-mL conical vial equipped for simple distillation and concentrate the solution to about half its original volume, removing the distillate from the Hickman stillhead as necessary. Allow the solution to cool below the boiling point, add the remainder of the dried ethereal extracts, and again concentrate the solution to about one-half its original volume. Alternatively, use rotary evaporation or other techniques to concentrate the solution. Cool the concentrated solution to room temperature. Once crystallization has begun, further cool the solution in an ice-water bath, and then collect the product 15 by vacuum filtration. Recrystallize it from 50% aqueous ethanol and air-dry the purified product. 

Optional Measures If some solid material remains after the addition of aqueous acid is complete, the entire mixture may be transferred to a screw-cap centrifuge tube. Sequentially add solvent-grade diethyl ether and water in 0.5-mL portions to the centrifuge tube. After each addition, cap the tube and shake it to dissolve the solids. Continue the extraction as described, using appropriately sized conical vials or screw-cap centrifuge tubes. 

---