DDS-Drug Analysis I

How are manufactured drug expiration dates derived?

1. Pharmacokinetic data

2. Therapeutic drug monitoring

3. Dosing intervals

Define high performance liquid chromatography

The placement of a volume of liquid sample (analytes) onto a column containing a stationary phase of small particles

Two phases of chromatography

mobile phase and stationary phase

Beer-Lambert Law

A=ebc where

A=absorbance

e (epsilon)=molar absorptivity

b=length of light path

c=concentration

Greater retention time in HPLC prefers which phase?

stationary phase

Common mobile phase solvents

1. Water

2. Acetonitrile

3. Methanol

4. Ethanol

5. Tetrahydrofuran

How is separation of analytes achieved?

By flowing the mobile phase over the stationary phase which allows the analytes to partition between the two

Isocratic profile in mobile phase

Mobile phase solvent remains constant with time and is best for simple separations or single analyte assays

Gradient profile in mobile phase

Mobile phase solvent(s) change with time and are best for analyzing complex samples, especially those involving unknown compounds

Three examples of modes of separation in HPLC

1. Reverse phase (RP)

2. Size-exclusion (SEC)

3. Chiral

Describe reverse phase in HPLC

A non-polar stationary phase with a polar mobile phase

Describe size exclusion chromatography

This method leverages differences in size of molecules to separate them. The pathway for smaller molecules is longer than for larger molecules. This results in increased time for small molecules to exit the column and reach the detector.

Describe chiral separation in HPLC

The use of certain chemicals such as cyclodextrin or xylene to separate certain isomers of compounds through surface interaction or inclusion complexing

Which positional isomer(s) of xylene is considered bulky and prevents full inclusion?

meta and ortho (para is linear and allows for greater inclusion)

How are enantiomers differentiated?

By the direction that they rotate plane polarized light (polarimeter)

Two primary categories of detectors in HPLC

1. Bulk property detectors- measure changes in mobile phase property: refractive index and conductivity detectors

2. Solute property detectors-measure physical or chemical solute property spectrophotometric, fluorescence, and electrochemical

Examples of detectors in HPLC

UV-Vis, fluorescence, refractive index, electrochemical, light scattering, radiochemical

Qualitative analysis tells us what two things?

1. Something is present

2. What the drug is

relative retention time

the ratio of the retention time of the substance to the retention time of a known component (IS)

Define quantitative analysis

Method that tells us how much of a substance is present

Define lower limit of detection (LLOD)

The lowest level of an analyte that can be reliably detected above the background or signal to noise ratio.

Put the following detection limits in order from lowest to highest:

1. LLOQ

2. Not detectable

3. ULOQ

4. BQL

Not detectable

Define accuracy

The extent to which a given measurement agrees with the known value (closeness)

Define precision

The variance in individual values of a repeated measure