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Determination of Drugs of Abuse in Urine by SPMEGC

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3)Desorb analytes from fiber in Gas Chromatograph (GC), detect and quantify. ... Provost Larkin and the Grants Office for acquisition of the Gas Chromatograph. ... – PowerPoint PPT presentation

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Title: Determination of Drugs of Abuse in Urine by SPMEGC


1
Determination of Drugs of Abuse in Urine by
SPME-GC
  • By Luci Johnson and Stacey Mooney

2
What is SPME?
  • Solid Phase Microextraction
  • Developed by Janusz Pawliszyn (University of
    Waterloo) in the early 90s.
  • An extraction technique used in quantitative
    analysis of analytes in a aqueous and gaseous
    phases.
  • Utilized in many different fields such as
    environmental, medical, culinary, and forensics.

3
Microsyringe Fiber
  • Organic-phase coated fused silica fiber.
  • Different types of coatings for different analyte
    detection.
  • Fiber is attached to a microsyringe as shown in
    the figure on the right.

4
Types of Exposure
  • Headspace
  • Used to analyze volatile compounds.
  • Fiber is exposed directly above the surface of
    the sample.
  • Direct
  • - Used to analyze compounds that are
    non-volatile.
  • - Fiber is submerged into the sample.

Our project involves simultaneous
headspace/direct exposure SPME, a process never
previously reported in the literature.
5
Why SPME?
  • Concentration effect
  • Solvent Free
  • Reusable
  • Simple
  • Faster than current techniques
  • Environmentally friendly

6
Our SPME Procedure
1) Prepare solutions for extraction. 2)Heat and
expose the fiber to the solutions. Insert
fiber ½ way into sample for simultaneous
direct/headspace exposure. 3)Desorb analytes
from fiber in Gas Chromatograph (GC), detect
and quantify.
7
1) Preparation of Solutions
  • MAS- Liquid Urinalysis Control
  • - Clean, sterilized urine
  • Internal Standards
  • - Ovex, Dyfonate, 1,5Dimethylnaphthalene,
  • Naphthalene were evaluated
  • Calibration Standards
  • - Prepared with drug analogues, procaine and
  • chloroamphetamine.
  • -Potassium carbonate and sodium fluoride
  • utilized to control solution conditions (pH
    and
  • ionic strength)
  • Sample Solutions (including alcohol and glucose)

8
2) Heating and Exposure
  • Solution is pre-heated and stirred on a hotplate
    for 10 minutes.
  • After ten minutes fiber is exposed to the
    solution at 80 C for 20 minutes while
    continuously being heated and stirred.

9
3) GC Analysis
  • Fiber is inserted into the GC injector _at_ 250 C
  • Fiber is exposed for 3 minutes.
  • GC has flame ionization detector (FID) which
    responds to carbon-containing compounds.
  • HP Chemstation software reports peak areas for
    each analyte.

10
Temperature Parameters of GC
11
Internal Standards
  • Analyte peak areas adjusted to that of internal
    standards for calibration and quantitation.
  • Internal standards are used through the
    extraction and analysis step
  • Internal standards are used to increase the
    accuracy and precision of the analysis by
    allowing the analyst to correct for
  • Instrumental fluctuations
  • Variations in solution composition
  • Variations in extraction efficiency
  • 1,5-Dimethylnaphthalene was found to be the best
    internal standard of the compounds evaluated.

12
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13
Use of an Internal Standard in the Analysis of
2.5 ppm Solutions
Conclusion The internal standard improves the
accuracy of the analysis, although additional
work on improving accuracy and precision is
required.
14
Do Foreign Substances Alter the Analysis?
  • Spiked some solutions with glucose and some with
    alcohol to determine if SPME could still detect
    and reliably quantify analytes in urine.
  • Alcohol was chosen to represent one urine
    constituent of an anebriated subject while
    glucose was chosen to represent one urine
    component possibly in excess in diabetic subjects

15
Replicate Analysis of 2.5 ppm Solutions w/
Contaminants
All Procaine analyses this
day were high.
16
Conclusions
  • The use of an internal standard improved
    analytical accuracy compared to not using an
    internal standard.
  • The presence of alcohol did not appear to alter
    the analytical results. This can be attributed to
    the use of the internal standard.
  • The presence of glucose greatly reduced the
    accuracy and precision of the analysis.
  • Additional work on optimizing the analytical
    procedure, with goals of getting accuracy down to
    10 and precision down to 10 RSD for Summer
    2002.
  • The useful lifetime of the fiber in this
    procedure appears to be 30 extractions,
    partially demonstrated by the apparent
    accumulation of procaine on the fiber during
    later runs.

17
Acknowledgements
  • Research Committee for financial support.
  • Dr. Hugh Gallagher for arranging the symposium.
  • Provost Larkin and the Grants Office for
    acquisition of the Gas Chromatograph.
  • Kimberly White for her earlier work.

18
Additional Slides and Results
  • Typical Calibration Curve (one curve)
  • Results for alcohol spiked urine with and without
    the internal standard in a table
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