Liquid Chromatography


Definition - What does Liquid Chromatography mean?

Liquid chromatography (LC) refers to a laboratory procedure used in conjunction with mass spectrometry (MS) in analyzing drug compounds exclusively to isolate constituent metabolites serving as biomarkers for confirmatory test findings. A urine specimen is used to identify the presence of illicit or prescription drug(s) including amphetamines, barbiturates, benzodiazepines, cocaine, marijuana, opioids, and phencyclidine (PCP), bolstered by LC-MS parameters that help quantify existing substance(s) in the body.

WorkplaceTesting explains Liquid Chromatography

In the workplace, urine drug screens are the mandatory criteria for detecting drug metabolites in the body with the corresponding time windows that support the frequency of consumption of alcohol or drug(s) in question. An immunoassay (IA) test serves as the preliminary measure for collecting a urine sample that aims to target a class of drugs, undermining its integrity from conflicting variables. For instance, urine drug screens can pose challenges with false negatives and false positives, neutralizing the base test findings in gaining official clearance.

A cut-off threshold serves as an index against the possibility of false positives that may be attributed to prescribed medication or inadvertent exposure to a prohibited substance (i.e., secondhand smoke) from an otherwise sober individual. Conversely, false negatives are problematic, as they tend to reflect deliberate tampering, for example, diluting a urine specimen by a test subject hoping to conceal a regular drug habit. Although immunoassay testing is cost-effective and easy to administer, its lax protocol gives way to potential loopholes along with potential failures to identify drugs within a designated class.

The LC modality provides an ample window for identifying a majority of drug compounds up to several days following their absorption into the body. It is advisable to employ LC-MS confirmatory testing as a means to level any discrepancies that play into erratic test findings that are consistent with immunoassay screening procedures. As drug and alcohol abuse remains a mounting concern to employers, confirmatory testing is beneficial in minimizing or preventing the appointment of individuals with substance abuse issues to safety-sensitive positions.

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