Jace James & Lauren Erland
Capillary Electrophoresis (CE)

Separation based on charge & frictional
force
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 chromatography
 Simultaneous separation of neutral and charged
molecules
 Detection ORGANIC compounds

Microchip CE
 Portable
 Presence explosive-compound residues
Detection of Separated
Compounds

CE can be coupled with diverse
detection devices depending on the
analyte of interest
 UV-Vis
 Laser induced fluorescence (LIF)
 Electrospray Ionization (ESI)
○ Allows coupling with MS
 NMR
 Chemiluminescence
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 powder
 Heavy 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 homemade explosives
Current Methods for Detection
Most common: Scanning Electron
Microscopy with Energy Dispersive Xray 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
ONLY

 Push towards ORGANIC primers
 False 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 grain

 MEKC 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 resolution
 Low power of differentiation

GC & HPLC commonly used







Greater technical skill required
Large sample size
Costly
Extensive sample prep
Difficult for complex samples
Destructive
Time 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 nanoliters
 Virtually non-destructive


Detection generally by UV-Vis
Has been applied to many types of pens and
inks
 Fountain-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!
