Solid Phase Microextraction/Capillary GC Analysis of Drugs, Alcohols, and Organic Solvents in Biological Fluids

Importance of the Topic

Solid phase microextraction (SPME) has emerged as a powerful, solvent-free sampling technique for trace analysis of drugs, alcohols and organic solvents in biological fluids. Its minimal sample preparation, high sensitivity and rapid analysis make it especially valuable in forensic toxicology, clinical testing and industrial quality control, where clean extracts and low limits of detection are essential.

Objectives and Study Overview

This bulletin reviews a series of SPME methods applied to urine, blood and headspace analysis of amphetamines, cocaine, tricyclic antidepressants, local anesthetics, alcohols and industrial solvents. The aim is to illustrate method protocols, key parameters and performance characteristics, demonstrating the broad applicability of SPME coupled to capillary GC and GC-MS or HPLC.

Methodology and Instrumentation

SPME relies on equilibration of analytes among the sample matrix, the headspace and a polymeric coating on a fused-silica fiber. Key variables include:

• Fiber chemistry and thickness (polydimethylsiloxane, Carbowax/divinylbenzene, etc.)
• Sampling mode: immersion or headspace
• Sample pH and salt addition to modulate analyte partitioning
• Temperature, extraction time and agitation
• Desorption conditions in the GC inlet (temperature, liner geometry, split ratio)

Instrumentation commonly comprises Supelco SPME holders and fibers, heated block or stir-plate incubators, capillary GC columns (PDMS or PEG phases), detectors (FID, NPD, MS/CI with SIM), and SPME-to-HPLC interfaces.

Main Results and Discussion

• Amphetamines in urine: Heated headspace SPME with PDMS fiber coupled to GC-MS/CI-SIM provided linear quantification from 0.2–100 mg/L, LODs <0.2 mg/L and precision CV <7%
• Cocaine in urine: Immersion SPME with PDMS fiber and GC-NPD yielded recoveries of 20–30%, a detection limit ~6 ng/0.5 mL and linear response up to 250 ng
• Tricyclic antidepressants: Headspace SPME of four drugs at basic pH and GC-FID achieved LODs of 24–38 ng/mL, linearity to 2 µg/mL
• Local anesthetics in blood: Post-acid deproteinization, HS-SPME and GC-FID enabled quantitation of ten compounds with LODs of 60–830 ng/mL and CVs <23%
• Alcohols in blood: HS-SPME with Carbowax/DVB fiber and SUPELCOWAX 10 column measured ethanol and other common alcohols in the range 50–300 mg/dL with CV ~2%
• Industrial solvents: HS-SPME of benzene, toluene, butyl acetate, etc., via PDMS fiber and GC-FID delivered 50–70% recovery, LODs ~1–2 ng/0.5 mL

Benefits and Practical Applications

SPME streamlines sample preparation by eliminating solvents and extensive cleanup steps. It concentrates analytes on the fiber for improved detection limits, reduces matrix interferences and is readily automated. These advantages enable rapid forensic screening, clinical drug monitoring and industrial safety testing.

Future Trends and Applications

Emerging developments include novel fiber coatings incorporating adsorbent polymers or nanoparticles, expanded coupling of SPME to HPLC and LC-MS, advanced autosampling systems, and miniaturized in-field devices. These innovations will extend SPME’s applicability to broader analyte classes and real-time monitoring.

Conclusion

SPME offers a versatile, efficient alternative to classical liquid-liquid and solid-phase extractions for volatile and semi-volatile compounds in biological fluids. By optimizing fiber chemistry, sampling conditions and instrumentation, analysts can achieve high sensitivity, precision and throughput in forensic, clinical and industrial laboratories.

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