HPLC Coupled with Quadrupole Mass Spectrometry and

Forensic Analysis of Cocaine

Analysis of Cocaine

C17H21NO4

Molecular weight: 303.353 g/mol

• Important for forensics• Samples• An unknown powder• Could contain other

components• A human specimen• Fluids (urine, blood

saliva)• Hair

HPLC: High performance liquid chromatography

• Sample injected using pressurized system

• Compounds travel through column at different rate– Interact with stationary phase

• Detection – Traditionally by UV absorption– More recently Mass

spectrometry• Better identification of unknowns

Typical Silica bead with C18 chains projecting off

Reverse Phase HPLC• Stationary Phase: small silica particles with long

hydrocarbons chains attached (non polar)• Mobile Phase: solvent, typically a water/alcohol

solution (polar)

Red compound is less polar than Blue compoundRed compound is present in a lower quantity

Example HPLC ChromatogramsRetention time differences for cocaine and some of its metabolites

Mass spectrometry

• Ion Source – Compound vaporized into gas phase – Energy added to ionize the compound• Excess energy may also fragment compound

– Most Common Method for cocaine: electrospray• Mass Analyzer – Fragments sorted based on mass/charge ratios– Ions detected

Quadrupole Mass Spectrometry• Apply voltages to 4 parallel rods• Create an electric field • Can change voltages to scan through m/z ratios

Resonant ions will make it through to the detector

Non-resonant ions will be neutralized by hitting rod

Mass Spectrometric identification of unknowns

•Quadrupole MS allows distinction of compounds with similar m/z•Compounds can also be distinguished by fragmentation patterns

Parent compound

Daughter ionsafter fragmentation

Example Mass Spectra ResultsCocaine and its

metabolites have different mass spectra

and fragmentation patterns

Oral Samples (Subject’s Saliva)

Applications

• Blood Gas Analysis• Allows for in vivo testing of gases present in the

blood• Analysis of stomach contents of overdose victims• Drug Profiling• Hair testing• Identification of unknown crime scene

specimens

Recent Studies

• Detection in Human Specimens– Optimize separation and codetection of several

different drugs in urine

• Detection in Unknown Powder– Cocaine was identified in presence of metabolites

and other drugs from benzoylecgonine