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Chemistry LibreTexts

Drugs (Blood)

Analysis of a Simulated Blood Sample for Drugs

Objective

To determine if a blood sample contains illicit drugs (from a short list of possibilities).

Sample

Simulated blood plasma with added illicit drug at a concentration of about 0.30 µg/mL. Prepare a fresh sample the day of the testing; the sample is not stable for more than a couple of days, even when stored in the refrigerator. The drug is chosen from a short list, provided to the students. Drug standards may be purchased without a DEA license (e.g. from Sigma-Aldrich).

Reagents

Drug standard (Sigma-Aldrich); methanol; 0.050 M, pH 6.0 phosphate buffer; 0.10 M HCl; 80:18:2 mixture of ethyl acetate:methanol:ammonium hydroxide

Standard Reference Material

None

Method

Solid phase extraction; gas chromatography - mass spectrometry

Special equipment

Capillary gas chromatograph-mass spectrometer with mid-polar column (e.g. DB-5, phenyl methyl silane, 30 m x 0.25 mm x 0.25 µm); 10-µL syringe; 2-mL chromatography vials with screw caps; 3-mL, mixed-mode (C8 & strong cation exchanger) solid phase extraction (SPE) cartridges (e.g. Strata Screen C from Phenomenex); vacuum manifold; aluminum heating block and supply of nitrogen gas for evaporating solvents

Procedure

For instructor (detailed); For student (brief)

Typical results

Total ion chromatogram of 0.50 µg/mL drug sample (cocaine) processed by SPE; 5µL injection of SPE eluate at 20:1 split; 1 mL/min helium flow; temperature programmed separation; ion trap mass analyzer.

Total ion chromatogram of the eluate from the solid phase extraction of cocaine in water. The cocaine peak has a retention time of 10.55 min.

Results of some quantitative experiments

The peak area of the cocaine peak arising from injection of a standard cocaine solution (10 ug/mL) was 1.90 million counts. The peak area of the cocaine peak arising from injection of the eluate (0.50 mL) from the solid phase extraction of 5.0 mL of an aqueous solution of cocaine (0.5 ug/mL) was 0.75 million counts. The extraction efficiency for cocaine was ~80% based on these numbers.

Mass spectrum of suspected drug (cocaine) from chromatogram above. Result of library search of suspected cocaine spectrum.

Mass spectrum associated with the chromatographic peak at retention time 10.55 min. Substance: Cocaine

Result of a library search of the mass spectrum above.
Best match: Cocaine; probability = 63