Parts of slideshow courtesy of Adam Hall, Instructor of Forensic Sciences, Boston University

 Separation of analytes from a liquid matrix by the use of another liquid (solvent) based upon selective partitioning  aka. Solvent Extraction  Suitable solvents are selected based on their abilities to partition target analytes within a liquid matrix  Consider:  Miscibility of solvents: EtOH and Water vs. Pentane  Immiscible solvents are employed for liquid-liquid extractions

 Remember: like-dissolves-like     Consider: Ionic, non-ionic, polar, and non-polar analytes Acid / Base / Amphoteric Nature of Analytes Solubility of Salts … i.e. Cocaine Hydrochloride (HCl)    General Comments: Neutral molecules are soluble in organic solvents Charged species are water soluble

 Manipulation and control of pH maximizes separation efficiency with LLE’s and SPE’s  Ionization of a compound alters its physical behavior and properties such as solubility and lipophilicity ▪ ▪ Ionization will increase a compounds solubility in water However, ionization will decrease a compounds lipophilicity

 Ionizable groups: carboxylic acid O  Carboxylic Acids  Phenolic Protons  Amines R OH pK a approx. 5 will deprotonate with NaOH and moderately strong bases phenol OH pK a approx. 10 harder to deprot. than carboxylic acids - will deprot. with NaOH amine R N R R pK b approx. 5 phenoxide O ammonium ion H will protonate with strong and moderately strong acids R N R R R carboxylate O O

 Acidic drugs O aspirin OH O CH 3 O NaOH O O O CH 3 O

 Phenolic containing drugs OH NaOH O THC Would require much stronger base to do this.

O O

  Many drugs are alkaloids (Nitrogen containing bases).

Often these drugs are available as an acid salt (such as the hydrochloride or sulfate), but the "free base" can be obtained by deprotonation.

CH 3 O N H Cl CH 3 O N OCH 3 HCl OCH 3 O NaOH O cocaine O (free base = crack) cocaine HCl O common alternative way of writing

pseudoephedrine diphenhydramine HCl LSD mescaline morphine sulfate

 Water solubility of molecules is pH dependent  A series of extractions and separations is performed to effectively separate compounds from a mixture: ▪ ▪ ▪ ▪ ▪ ▪ Strong Acids Weak Acids Strong Bases Weak Bases Amphoteric Molecules Neutral Molecules http://orgchem.colorado.edu/hndbksupport/ext/extprocedure.html

 White powder (caffeine + procaine) is added to methylene chloride (CH2Cl2) in a separatory funnel. Aqueous acid (such as 0.1 M H2SO4) is added. ▪ The caffeine molecule (neutral) is partitioned into the methylene chloride (bottom, organic) layer. The sulfate salt of procaine is partitioned into the aqueous (top) layer. stays soluble in CH 2 Cl 2 2 H 2 N O O N + H 2 SO 4 2 H 2 N O O water soluble N H SO 4 2-

 The bottom layer is drained  the methylene chloride can be evaporated to obtain nearly pure caffeine.  Another portion of methylene chloride is added to the separatory funnel, which still contains the aqueous acid and dissolved procaine.   Solid or aqueous base is added to the aqueous phase until that phase is basic.  The procaine, converted to free base, is partitioned into the methylene chloride (bottom) layer. O O N N O + 2NaOH O 2 H 2 H 2 N H 2 N soluble in CH 2 Cl 2 The bottom layer is drained  the methylene chloride can be evaporated to obtain nearly pure procaine.

Quinine Bisulfate is an Antimalarial Drug Qunine is also found in tonic water Quinine is fluorescent CH 3 O HO H N H HSO 4 HO H N 2NaOH CH 3 O + SO 4 2 + 2H 2 O N N If we titrate a known volume of quinine bisulfate solution with a standardized (known molarity) NaOH solution, we can determine the molarity of the quinine bisulfate solution.

     Learn how to standardize a solution by titration Learn how to perform multiple titrations with good precision Review stoichiometry Determine the concentration of a solution of quinine bisulfate of unknown molarity Observe the differences in solubility between an acidic and basic form of a drug

 Standardize NaOH against KHP O NaOH O K OH O O K O Na  O O Use standardized NaOH to titrate quinine sulfate and calculate its molarity + H 2 O HO H N H HSO 4 HO H N 2NaOH CH 3 O CH 3 O + SO 4 2 + 2H 2 O N N