Title: Determination of Drugs of Abuse in Urine by SPMEGC
1Determination of Drugs of Abuse in Urine by
SPME-GC
- By Luci Johnson and Stacey Mooney
2What 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.
3Microsyringe 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.
4Types 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.
5Why SPME?
- Concentration effect
- Solvent Free
- Reusable
- Simple
- Faster than current techniques
- Environmentally friendly
6Our 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.
71) 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)
82) 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.
93) 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.
10Temperature Parameters of GC
11Internal 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.
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13Use 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.
14Do 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
15Replicate Analysis of 2.5 ppm Solutions w/
Contaminants
All Procaine analyses this
day were high.
16Conclusions
- 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.
17Acknowledgements
- 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.
18Additional Slides and Results
- Typical Calibration Curve (one curve)
- Results for alcohol spiked urine with and without
the internal standard in a table