Liquids conical vials

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). 

Amino acids were derlvatlzed with 1-dlmethylamlnonaphthalene-5-sulfonyl chloride (dansyl chloride) according to the procedure of Tapuhl and coworkers (48-50). A 10 M stock solution of twenty common -amlno acids (Sigma Chemical Co., St. Louis, MO) was prepared by dissolving the carefully weighed standards in 0.1 M aqueous hydrochloric acid. Aliquots of this solution were transferred to conical vials, evaporated to dryness, and redlssolved In 500 pL aqueous buffer (0.04 M lithium carbonate, pH 9.5). A 500 jL volume of dansyl chloride solution (5 x 10 3 m in acetonitrile) was added, and the derlvatlzatlon was allowed to proceed In the dark at 35"C for one hour. The reaction was terminated by the addition of 2% methylamlne hydrochloride, and the derlvatlzed sample was analyzed Immediately by mlcrocolumn liquid chromatography with UV-absorbance and LIF detection. 

On a balance, weigh 0.5 grams (0.5 mL) of water into a 3-mL conical vial. Select a short (5%-inch) Pasteur pipette and attach a rubber bulb. Squeeze the rubber bulb before inserting the tip of the pipette into the water. Try to control how much you depress the bulb, so that when the pipette is placed into the water and the bulb is completely released, only the desired amount of liquid is drawn into the pipette. (This skill may take some time to acquire, but it will facilitate your use of a Pasteur pipette.) When the water has been drawn up, place a mark with an indelible marking pen at the position of the meniscus. A more durable mark can be made by scoring the pipette with a file. Repeat this procedure with 1.0 gram of water, and make a 1-mL mark on the same pipette. 

Separation of immiscible liquid layers in a conical vial. 

The two liquid layers are separated by withdrawing the lower layer using a disposable Pasteur pipette. This separation technique is illustrated in Figure 9. Take care not to disturb the liquid layers by allowing bubbles to issue from the pipette. Squeeze the pipette bulb to the required amount before introducing the pipette into the vial. Also take care not to allow any of the upper liquid layer to enter the pipette. The pointed shape of the interior of the conical vial makes it easy to remove all the lower layer without allowing it be contaminated by some of the upper liquid layer. More precise control in the separation can be achieved by using a filter-tip pipette (see Technique 8, Section 8.6). 

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. 

When the level of the methanol reaches the surface of the alumina, transfer fhe solution containing the drug from the beaker or test tube to the column using a Pasteur pipette. Collect the liquid that passes through the column into a 5-mL conical vial. When all the liquid from the beaker has been added to the column and has penetrated the alumina, add an additional 1 mL of methanol to the column and allow it to drain. This ensures that all the analgesic drug has been eluted from the column. 

If you are isolating aspirin, it is essential that the following evaporation procedure be completed in 10-15 minutes. Otherwise, the aspirin may partially decompose. Using a Pasteur pipette, transfer about half the liquid in the 5-mL conical vial to another small container. Evaporate the methanol in the 5-mL conical vial using a water bath at about 50°C (Technique 7, Section 7.10). To speed evaporation, direct a gentle stream of dry air or nitrogen into the vial containing the liquid. Evaporate the solvent until the volume is less than about 1 mL. Then add the remainder of the liquid and continue evaporation. 

Caffeine can be purified by sublimation (Technique 17, Section 17.5). Assemble a sublimation apparatus as shown in Figure 17.2A. Add approximately 0.5 mL of methylene chloride to the Erlenmeyer flask and transfer the solution to a clean, 5-mL, thin-walled, conical vial, using a clean and dry Pasteur pipette. Add a few more drops of methylene chloride to the flask in order to rinse the caffeine out completely. Transfer this liquid to the conical vial. Evaporate the methylene chloride from the conical vial by gentle heating in a warm water bath imder a stream of dry air or nitrogen. 

Infrared Spectroscopy Obtain the infrared spectrum of the (—)-carvone sample from spearmint or of the (+)-carvone sample from caraway (see Technique 25, Section 25.2). Compare your result with that of a person working with the other isomer. At the option of the instructor, obtain the infrared spectrum of the (+)-limonene, which is found in both oils. If possible, determine all spectra using neat samples. If you isolated the samples by preparative gas chromatography, it may be necessary to add one to two drops of carbon tetrachloride to the sample. Thoroughly mix the liquids by drawing the mixture into a Pasteur pipette and expelling several times. It may be helpful to draw the end of the pipette to a narrow tip in order to withdraw all the liquid in the conical vial. As an alternative, use a microsyringe. Obtain a spectrum on this solution, as described in Technique 25, Section 25.2. 

As distillate condenses in the Hickman head, transfer the liquid from the reservoir to a preweighed 3-mL conical vial. If your Hickman head does not have a side port, it will be necessary to use a 9-inch Pasteur pipette. In the latter case, it is helpful to bend the tip of the pipette slightly by heating it in a flame. The distillate can then be removed without removing the thermometer. Be sure to cap the conical vial used for storage each time after you transfer the distillate. Continue to distill the mixture, and transfer the distillate to the vial until the temperature in the Hickman head increases above 78°C or until the temperature in the Hickman head drops several degrees below 78°C and remains at this lower temperature for 10 minutes or more. You should collect about 0.4 mL of distillate. The distillation should then be interrupted by removing the apparatus from the heat source. 

NOTE Before shaking the conical vial vigorously in the next step, be sure that the capped vial does not leak. If it does leak, use a Pasteur pipette to mix the two layers. Draw up as much liquid as possible into the Pasteur pipette and then expel the liquid rapidly back into the conical vial. Continue this mixing for 3-4 minutes. 

When distillation is complete, remove as much distillate as possible from the Hickman head and transfer it to the 3-mL conical vial. Then, using a Pasteur pipette with the tip slightly bent, rinse the sides of the inside wall of the Hickman head with 1.0 mL of saturated sodium chloride. Do this thoroughly so that as much liquid as possible is washed down into the well of the Hickman head. Transfer this liquid to the 3-mL conical vial. 

Choose one of three aldehydes for this experiment piperonaldehyde (solid), 3-nitrobenzaldehyde (solid), or p-anisaldehyde (liquid). Place 0.150 g of piperonaldehyde (3,4-methylenedioxybenzaldehyde, MW = 150.1) or 0.151 g of 3-nitrobenzaldehyde (MW = 151.1) into a 5-mL conical vial. Alternatively, transfer 0.13 mL of p-anisaldehyde (4-methoxybenzaldehyde, MW = 136.2) to a fared conical vial and reweigh the vial to determine the weight of material transferred. 

The stream of air or nitrogen must be very gentle or you will blast your solution out of the conical vial. In addition, do not overheat the sample. Do not continue the evaporation beyond the point where all the methylene chloride has evaporated. Your product is a volatile oil (i.e., liquid). If you continue to heat and evaporate, you will lose it. It is better to leave some methylene chloride than to lose your sample. 

Transfer the organic layer to a dry 3-mL conical vial (5-mL if necessary) and add 3 to 4 microspatulafuls of anhydrous sodium sulfate (use the V-grooved end). Cap the vial and set it aside for 10-15 minutes while the liquid is dried. If the liquid appears cloudy, shake the vial several times during the drying period or add more sodium sulfate. 

Microscale Methods. A simple means of evaporating a solvent is to place a conical vial in a warm water bath or a warm sand bath. The heat from the water bath or sand bath will warm the solvent to a temperature where it can evaporate within a short time. The heat from the water bath or sand bath can be adjusted to provide the best rate of evaporation, but the liquid should not be allowed to boil vigorously. The evaporation rate can be increased by allowing a stream of dry air or nitrogen to be directed into the vial (Figure 7.17A). The moving gas stream will sweep the vapors from the vial and accelerate the evaporation. As an alternative, a vacuum can be applied above the vial to draw away solvent vapors (Figure 7.17B and 7.17C). 

To dry a large amount of organic liquid (greater than about 5 mL), follow the same four steps just described for the "Microscale Drying Procedure." The main differences are that an Erlenmeyer flask is used rather than a test tube or conical vial and more drying agent will be required. The size of the Erlenmeyer flask is not critical, but it s best that the flask not be filled more than half full with the solution being dried. 

What is the approximate difference between the temperature of a boiling liquid in a conical vial and the temperature read on an external thermometer when both are placed on an aluminum block ... 

If you are using an FT-NMR spectrometer, add 30 mg (0.030 g) of your liquid or solid sample to a tared conical vial or test tube. Use a Pasteur pipette to transfer a liquid or a spatula to transfer a solid. Non-FT instruments usually require a more concentrated solution in order to obtain an adequate spectrum. Typically, a 10-30% sample concentration (weight/weight) is used. 

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. 

It is important to ascertain which of the two layers in a conical vial is the aqueous layer and which is the organic. Because the layers will usually separate so that the denser solvent is on the bottom, knowledge of the densities of the liquids being separated provides an important clue as to the identity of each layer. This generalization is not foolproof, however, because a high concentration of a solute in one layer may reverse the relative densities of the two liquids. You must not confuse the identity of the two layers in the conical vial or test tube and then discard the layer containing your product. Both layers should always be saved until there is no doubt about the identity of each and the desired product has been isolated. 

Setting Up Place a spinvane in the conical vial. Using a calibrated Pasteur pipet, add 1 mL of cyclohexanol and 0.5 mL of 9 AT sulfuric acid to the vial. Thoroughly mix the contents by briefly stirring or swirling the liquid for a few seconds. Equip the vial for microscale distillation and circulate cold water through the condenser. 

Work with liquids in conical vials, and work in a vial whose capacity is approximately twice the volume of the material it needs to hold. The trick here is to reduce the surface area of the flask in contact with the sample to an absolute rninimum. A conical vial is thus better than the spherical surface of the conventional round-bottom flask. 

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