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Jace James & Lauren Erland. Separation based on charge & frictional force Capillary Electrophoresis...
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Transcript of Jace James & Lauren Erland. Separation based on charge & frictional force Capillary Electrophoresis...
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!