Analytical Toxicology

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Analytical Toxicology
Instrumentation and Methodologies
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Sampling from liquid phases

• Liquid extractions
• Batch liquid-liquid extraction

• Solid phase extractions
• SPE Solid Phase Extraction (transfer to
  another solvent)
• SPME Solid Phase Micro-Extraction (solventless)

• Headspace sampling
• Static headspace (high concentrations)
• Dynamic headspace (low-moderate concentrations)
• Purge-and Trap (low concentrations)

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Solvent Extraction
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Add immisible extracting solvent
Repeat these steps 1 to 3 times
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Solvent Extraction
Distribution coefficient Fraction remaining
after n extractions
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Miscibility of solvents
Miscible if the two solvents can be mixed in all
proportions without forming two phases
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Solid Phase Extraction - SPE
Conditioning The sorbent is wetted and rinsed by
the eluting solvent
Acetonitrile Water Water samples Methanol/ w
ater Acetonitrile
The sorbent is conditioned by a pure solvent like
the matrix
Retention A liquid sample passed through a short
column of solid sorbent, where the desired
compounds are sorbed
Rinse Unwanted compounds are rinsed by elution
with a suitable solvent
Elution The analytes are eluted by a suitable
eluent
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Solid Phase Extraction - SPE
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Solid phases for SPE
Most materials are bonded phases attached
covalently to big porous silica particles (o.d. ?
50 ?m surface 50 m2g-1)

• Non-polar sorbents (reversed phase)
• C18 C8 C6 C4 C2
• Cyclohexyl
• Phenyl
• Cyanoprolyl

• Polar sorbents (normal phase)
• Cyanopropyl
• Bare Silica
• Diol
• Aminoalkyl

• Ion exchange sorbents
• Strong Anion eXchanger
• Strong Cation eXchanger
• Weak anion- and cation exchangers

• Endcapped sorbents
• accessible SiOH are reacted with trimethyl
  silane

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SPE Modes and eluents

• Change of sample polarity
• dilute with appropriate solvent
• exchange solvent by SPE

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Solid Phase Micro-Extraction - SPME
Metal rod

• Sorption of analytes
• In situ extraction from headspace or liquid
  samples
• 1-60 min
• NO SOLVENTS USED !

Protecting metal tube

• Thermal desorption
• Splitless injection in GC
• (Interface for HPLC are known)

Silica fiber
Solid sorbent coating
1 cm
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Solid Phase Micro-Extraction - SPME
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UV-Vis Absorption Spectroscopy

• A ebc

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Measure at lmax
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Single beam spectrophotometer
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Double beam Spectrophotometer
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Which drugs can be determined using UV-Vis?
Energy
s p
n
p s
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Luminescence Spectroscopy
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F KP0ebc
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Fluorometers
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Spectrofluorometers
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Luminometers
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Atomic Absorption Spectrometers
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Sample introduction
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AAS Spectrometers
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Atomic Emission Spectroscopy
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DCP
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ICP Spectrometer
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Mutichannel ICP Spectrometer
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ICP-MS
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Injector
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Thermal Conductivity detector
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Flame Ionization Detector
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Packed Columns

• These columns are fabricated from glass,
  stainless steel, copper, or other suitable tubes.
  Stainless steel is the most common tubing used
  with internal diameters from 1-4 mm. The column
  is packed with finely divided particles (lt100-300
  mm diameter) which is coated with stationary
  phase. However, glass tubes are also used for
  large scale separations. Several types of tubing
  were used ranging from copper, stainless steel,
  aluminum and glass. Stainless steel is the most
  widely used because it is most inert and easy to
  work with. The column diameters currently in use
  are ordinarily 1/16" to 1/4" 0.D.

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Capillary/Open Tubular

• Open tubular or capillary columns are finding
  broad applications. These are used for fast and
  efficient separations but are good only for small
  samples. The most frequently used capillary
  column, nowadays, is the fused silica open
  tubular column (FSOT) which is a WCOT column. The
  external surface of the fused silica columns is
  coated with a polyimide film to increase their
  strength. The most frequently used internal
  diameters occur in the range from 260-320
  micrometer.

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Liquid Stationary Phases

• In general, the polarity of the stationary phase
  should match that of the sample constituents
  ("like" dissolves "like"). Most stationary phases
  are based on polydimethylsiloxane or polyethylene
  glycol (PEG) backbones

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Stationary phases
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Typical Separation
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TPGC versus Isothermal
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Head Space GC