W3 L3 - Intro to pharmaceutical analysis techniques Flashcards
Pharmaceutical Applications of pharmaceutical analysis
- Drug discovery & development
- Formulation stability testing
- Drug metabolism
- Pharmacokinetics & Pharmacodynamics
- Quality control & Quality assurance
Why is sample preparation important in pharmaceutical analysis?
To isolate drugs from complex matrices, concentrate analytes, derivatize (chemical modification of a drug to improve its stability, solubility, detection, or pharmacokinetics) them, and stabilize them from degradation.
What are the main extraction and purification methods in pharmaceutical analysis?
- Solid-phase extraction (SPE)
Stationary + Mobile phases (technique):
SPE/SPME
Filtration
Chromatography - liquid-liquid extraction (LLE)
Mobile Phases solvent –Solvent (technique):
immiscible
Separating funnel
Counter current distribution
Miscible
Crystallisation
Fractional distillation
- acid-base extraction
What is solid-phase extraction (SPE) used for?
Removing interferences from samples, improving reliability, concentrating analytes, and improving sensitivity.
What are the advantages of solid-phase extraction (SPE) over liquid-liquid extraction (LLE)?
Faster, less labor-intensive, lower solvent usage, better recovery, easier automation, and more selectivity.
How does liquid-liquid extraction (LLE) work?
It separates substances based on their distribution coefficients in two immiscible solvents (e.g., water & organic solvent).
Capture
Sample is filtered through a sorbent particles
Analytes captured from the liquid matrix
Elute (remove an adsorbed substance by washing with a solvent)
Concentrated analytes eluted with solvent.
Eluted sample collected
How can pH be used to selectively extract weak acids or weak bases?
Lowering pH increases solubility of acidic drugs in organic solvents, while raising pH increases solubility of basic drugs.
What is an example of an acidic drug and a basic drug affected by pH in extraction?
Aspirin (acidic, requires lower pH); Procaine (basic, requires higher pH).
What are common methods for separating drugs from miscible phases?
Rotary evaporation, fractional distillation, crystallization, and sublimation (lyophilization)
What are the main analytical techniques used for quantitative pharmaceutical analysis?
Volumetric (titrimetric), spectroscopic, and chromatographic methods.
What is volumetric analysis (titration) used for?
Determining drug concentration through chemical reactions (e.g., acid-base, redox, complexation titrations).
How does back titration work, and when is it useful?
Excess reagent is added to the analyte and then titrated. It is useful when the direct titration reaction is slow or hard to detect.
What is the complexation reaction for magnesium titration with EDTA?
Mg 2+ +EDTA 4− →MgEDTA 2− (1:1 ratio)
How is metal ion concentration determined if the exact formula of ingredients is unknown?
Indirect methods such as ignition, converting the metal into its oxide form and calculating its content.
