Jace James & Lauren Erland. Separation based on charge & frictional force Capillary...

Jace James & Lauren Erland

Separation based on charge & frictional force

Capillary Electrophoresis (CE)

CE Capillary zone electrophoresis (CZE)

Separation of charged molecules based on electrophoretic mobilities & migration velocities

Detection INORGANIC compounds Micellar electrokinetic chromatography

(MEKC)Combines electrophoresis and chromatographySimultaneous separation of neutral and charged

moleculesDetection ORGANIC compounds

Microchip CEPortable Presence explosive-compound residues

Detection of Separated Compounds CE can be coupled with diverse

detection devices depending on the analyte of interestUV-VisLaser induced fluorescence (LIF)Electrospray Ionization (ESI)

○ Allows coupling with MSNMRChemiluminescence

Advantages Simple instrumentation Exceptional power & resolution Rapid analysis time Highly versatile

Same instrument, often same capillary can be used to run diverse samples (change only running buffer)

Can be coupled with many different detection devices Separation of charged, neutral and volatile molecules Low mass limits of detection

Nanograms or picograms of sample Minimal damage to sample

Inexpensive reagents Waste is mostly aqueous, environmentally friendly

Minimal sample requirements Direct sample injection

In many cases no sample prep required

Gunshot Residue (GSR) & Explosives Produced when a firearm is discharged

Deposited on hands of the perpetrator Components include:

Unburned powderHeavy metals from the barrel of the gun, primer

and cartridge Determination if firearm has been fired

identify bullet holes estimate firing distance

Detection military, industrial and home-made explosives

Current Methods for Detection Most common: Scanning Electron

Microscopy with Energy Dispersive X-ray Analysis (SEM-EDX)

moderate sensitivity, requires expensive instrumentation, is highly demanding in terms of professional skills, and is a very time consuming process.

Identification INORGANIC compounds ONLYPush towards ORGANIC primersFalse Negatives!!!

SEM-EDX: A case study 2001 Identification of a single, partially burnt

gunpowder grain on a suspect’s clothing SEM unsuccessful CE was able to identify and individualize

the gunpowder grainMEKC can be used to detect ORGANIC

compounds CZE for INORGANIC compounds

Ink Analysis Separation is a vital step in ink analysis

Ink components vary widely with manufacturer, colour

Possibility of contamination from writing surface

Chemical changes as ink ages Results can be stored electronically

Development reference libraries Difficult to find a single method for

separation of such diverse mixtures

Current Techniques TLC

Low resolutionLow power of differentiation

GC & HPLC commonly used Greater technical skill requiredLarge sample sizeCostly Extensive sample prepDifficult for complex samplesDestructiveTime consuming

CE & Ink Analysis CE appropriate for many different types of analyte

Organic, inorganic, volatile Need only change running buffer Quick, easy and inexpensive!

Extraordinarily small quantities required Pico or nanolitersVirtually non-destructive

Detection generally by UV-Vis Has been applied to many types of pens and

inksFountain-pen, ballpoint, water-soluble, red, blue and

black inks

CE readily differentiates inks originating from different manufacturers

Reproducible migration times and relative peak areas

Capillary Electrophoresis

Simple Low Cost Short analysis time Non-destructive High power resolution and separation Potential to expand to many other

applications Eco-Friendly!