Posted October 18th, 2012
There are two types of nicotine tests: (1) those collected in a lab, where the persona being tested urinates into a cup with a tamper evident seal and gives the sample to the lab personnel, or doctor (2) on-site pee screens using an inexpensive kit. While a lab-style test is more accurate and private, an on-site test gives those being tested less notice and is lee expensive. On-site testing provides quick results, and can be legally binding if backed up later by a lab report.
Substances Being Screened For
Methods of Screening
There are three main procedures for screening urine: immunoassay, gas chromatography, and gas chromatography/ mass spectrometry. Immunoassay uses interactions between antigens and antibodies to detect substances. Certain antibodies bind to certain components of nicotine, and immunoassays screens for the antibodies instead of the metabolites themselves. This method is quite accurate, although it can sometimes not differentiate between types of drugs. False negatives are more common than false positives.
Gas chromatography uses techniques that separate particles in the urine. An inert gas pushed the urine through chromatographic columns, which separates aspects of the urine by affinity for different parts of the device. Different compounds are identified by the time it takes them to separate; this is called retention time. Each nicotine metabolite has a unique retention time.
Gas chromatography with mass spectrometry (GC-MS) is a two-step process. First, the urine sample is separated using the gas chromatography method outlined above. Then, mass spectrometry identifies the exact molecular structure of compounds of interest. When a sample enters the spectrometry machine, electrons surround the sample. This causes the compound to separate even further, “fragmenting” in a way where compounds can be conclusively identified. GC-MS is the most accurate method of screening and is considered the definitive test in a court of law.
Abstinence (not using a substance) and substitution (using another person’s urine or synthetic urine) are the only ways to circumvent a GC-MS screening. Common rumors for circumvention (drinking water, drinking vinegar, herbal supplements) are unreliable, and most labs actively look for the intentional alteration of urine composition.