Thin-Layer Chromatography, Drug Identifications

TLC Chromatography Identification of Biochemicals, Medicines, Drugs

Nov 4, 2009

Patulin Mycotoxin Detected by TLC, Analtech

TLC, thin-layer chromatography, is a procedure of chemistry that can identify over 700 types of biochemicals, including significant medical drugs of legal importance.

The accident scene was chaotic — 2 cars, 7 injured, 2 dead, and 5 rushed to the emergency room. Blood samples obtained from the drivers of each car soon revealed that the surviving driver would be charged with vehicular homicide and dangerous and reckless driving — there was clear evidence of drugs within his blood. This "Scientific Inquiry" evaluates thin-layer chromatography for criminal, health, medical and industrial studies.

Crime Scene Investigation (CSI) Relies on Critical Biological and Chemical Evidence

Reconstructions of crime or accident scenes, and the gathering of evidence, are all attempts by legal authorities to establish facts and reveal the true story of a case so that guilt, or innocence, may be established. The value of chemical analyses is most critical in cases of impairment of brain function, toxicity and poisonings. Murder by intent, or murder by accident, are two different stories that have the same end result. Today's modern societies, with high dependency on both prescribed and illegally used drugs, present a challenge that often can only be solved by the use of sophisticated chemical analyses. One such instrument and device is thin-layer chromatography (TLC).

Thin-Layer Chromatography (TLC) Equipment and Procedures

State and Federal Crime Labs often use thin-layer chromatography. TLC is:

reliable, rapid, and easy procedure.
relatively inexpensive.
able to detect upward of 700 different types of drugs and medications.
validated as a diagnostic tool that holds up under the scrutiny of legal challenges, inside and outside the courtroom.

Thin-Layer Chromatography (TLC) Detects Many Compounds

TLC can detect accurately, a large number of medically-significant, legally-important compounds as listed following:

Anticonvulsants/antispasmodics: phenytoin, carbamazepine, trihexyphenidyl
Antidepressants: amitriptyline, nortriptyline, sertraline, fluoxetine, trimipramine, desipramine
Antihistamines: chlorpheniramine, diphenhydramine, orphenadrine, doxylamine, hydroxyzine
Anti-inflammatories: naproxen, ketoprofen, ibuprofen
Anaesthetics (local): lidocaine, procaine
Decongestants/broncodilators: ephedrine, pseudoephedrine, phenylpropanolamine, theophylline
Muscle relaxants: carisoprodol, meprobamate, methacarbamol
Narcotic analgesics: propoxyphene, meperidine, methadone, tramadol, pentazocine
Sedatives: glutethimide, methaqualone, ketamine, imipramine, doxepin, trazodone, amoxapine
Stimulants: methylphenidate, phentermine, methylenedioxymethamphetamine (MDMA), methylenedioxyamphetamine (MDA)
Miscellaneous: strychnine, verapamil, acetaminophen, quinine, quinidine, psilocin, haloperidol, dextromethorphan. (Drug List Here Adapted from the Toxicology Missouri Highway Patrol Laboratory)

Thin-Layer Chromatography (TLC) Techniques, Material and Methods

The principles and practice of TLC are similar to paper chromatography in a number of ways with: a stationary phase (gel versus paper), a solvent, standard reference chemicals and unknowns, Rf values and simple visual verification of the chromatography end results.

Gel chemical compound medium is applied in a slurry onto the top surface of a glass or plastic slide, and allowed to dry. (Gel sorbents, also termed stationary phase compounds, include: silica gel, starch, aluminum oxide, or even powdered chalk)
Samples (known standards and unknowns) are applied at the base of the TLC slide.
Solvent facilitates sample movement through the gel on the slide.
Rf (Retardation factor) values are determined, and aspects of fluorescence, native coloration, or reaction with chemical detectors, (e.g. Duquenois reagent, for marijuana detection) also are evaluated.

The value of TLC is indisputable. In industry and manufacturing TLC can used to evaluate: purity of certain raw materials, chemical processes during manufacture, and even final product purity.

Many career opportunities exist for those with an interest in chemistry. Consider chemistry and chemical technology education as a career path.

Sources

Bioinstrumentation, Tools for Understanding Life. 1996. Wandersee, J.H., et al., eds. National Assoc. Biol. Teachers, Reston, Va. 329 pp

Toxicology Laboratory, Missouri Highway Patrol

The copyright of the article Thin-Layer Chromatography, Drug Identifications in Scientific Research Methods is owned by Donald Reinhardt. Permission to republish Thin-Layer Chromatography, Drug Identifications in print or online must be granted by the author in writing.