Liquid-Liquid Extraction of a Two Drug unknown in Sugar
 

 

Objective and Summary:

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The purpose of this experiment was to separate a two drug and sugar white powder mixture into three pure components. This was done by liquid-liquid extraction. Once they were separated both drug samples of acetaminophen and aspirin were recovered and tested for purity using TLC and IR.

 

Procedure:

 

Materials and Methods:

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An Ohaus Voyager Pro Model: VP214CN was used for weight measurements. A separatory funnel on a ring stand was used in the extraction. Stock solutions of Ethyl acetate, saturated NaHCO3, 6.0 M HCl, 0.5% Acetic acid in Ethyl acetate, solid caffeine, solid Acetaminophen, and solid Acetylsalicylic acid were provided by the California State University East Bay chemistry stockroom. Acros Organics Ibuprofen Lot # A0167136 was used as a TLC standard. A TLC chamber, TLC plates, Pyrex capillary tubes No. 9530-2, and a UV lamp were used in TLC. A Perkin Elmer UATR Spectrum two FT-IR spectrophotometer was used.

 

Extraction Scheme:

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2.5054g of the white powder unknown were measured out in a beaker. The unknown was dissolved in 20 mL of ethyl acetate and 10 mL of deionized water. The solution was transferred to a separatory funnel where it was mixed by inverting, then allowed to vent. The inversion and venting process was repeated until gas was no longer produced. The bottom layer of water and sugar was allowed to run out of the funnel and discarded. 10 mL of sodium bicarbonate was added to the 20 mL of ethyl acetate containing the acetaminophen and aspirin. The new bottom layer of sodium bicarbonate containing aspirin was allowed to run out of the funnel. 6.0 M HCl was added to this solution dropwise until solid aspirin precipitated out of solution. The precipitate was filtered out using a long stem funnel and filter paper, then left to dry. The solution of ethyl acetate containing acetaminophen was allowed to run out of the separatory funnel into an erlenmeyer flask and was dried using a stream of air in the chemical hood. A solid residue was left behind for TLC and IR.

 

TLC and FT-IR:

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A TLC was run for both recovered drug samples and for four drug standards of aspirin, ibuprofen, caffeine, and acetaminophen. A microspatula tip full of each solid was dissolved separately in 0.5 mL of dichloromethane. Capillary tubes were used to spot each sample onto TLC plates. The plates were placed in a TLC chamber containing 0.5% Acetic acid in Ethyl acetate as the solvent. Rf values were observed under UV light and recorded for each standard and recovered drug sample. FT-IR results of the recovered drug samples were recorded. 

 

Results:

The results of the TLC and FT-IR are as follows:

 

Solid sample:                                                              TLC Rf value:                         Major functional group peaks observed in IR:

 

~Acetaminophen                                                           0.55187                                Amide, Phenol, Hydroxyl - peaks are                                                                                                                                                    formed but were never labeled on the IR                                                                                                                                            print out. All these points are in the 3700-                                                                                                                                            3200 range. Amide C=O Stretch - 1649

 

~Aspirin                                                                           0.6875                                    Aromatic C=C Bending- 1679, 1604                                                                                                                                                   Aromatic C-H Bending - 839, 803, 753, 703

                                                                                                                                           Ester C=O Stretch- 1749

                                                                                                                                     Carboxylic Acid O-H Stretch was not labeled

 

~Ibuprofen                                                                      0.85714                                                        Not found

 

~Caffeine                                                                        0.17857                                                        Not found

 

~Extracted drug solid 1 (aspirin)                                   0.78125                                     Aromatic C=C Bending- 1679, 1604                                                                                                                                                   Aromatic C-H Bending - 839, 803, 753, 703

                                                                                                                                                    Ester C=O Stretch- 1749

                                                                                                                                     Carboxylic Acid O-H Stretch was not labeled

 

~Extracted drug solid 2 (Acetaminophen)                    0.41391                                   Amide, Phenol, Hydroxyl - peaks are                                                                                                                                                 formed but were never labeled on the IR                                                                                                                                               print out. All these points are in the 3700-                                                                                                                                           3200 range. Amide C=O Stretch - 1649

 

Conclusion:

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The Aspirin, Acetaminophen, and sugar unknown was first dissolved in a mixture of ethyl acetate as the organic solvent and deionized water as the aqueous solvent. This should have dissolved aspirin and acetaminophen in the ethyl acetate but not the sugar. This should have left the sugar in the water. Allowing the water to run out of the separatory funnel the sugar was separated from the 3 part unknown. By adding Sodium bicarbonate to the ethyl acetate layer, sodium bicarbonate should have only reacted with the stronger acid in Aspirin not the weaker acid in acetaminophen. This would separate out aspirin in the sodium bicarbonate leaving the acetaminophen behind in the ethyl acetate. A strong 6.0 M HCl was then added to reprotonate the aspirin causing it to fall out of solution as a precipitate. The ethyl acetate is a volatile liquid and only needed to be dried by airflow to leave behind solid acetaminophen. When both extracted drugs were analyzed by TLC they resulted in Rf values that differed from their drug standards showing that they are not entirely pure. When they were analyzed by FT-IR they appeared to be close in purity in comparison to the standards.