Mass spectrometer testing is the other test used to verify a positive reading from an immunoassay test. This test is based on the behavior of light, and how light reacts to a sample. In order to fully understand of a mass spectrometer reads a sample, it is important to understand the basic concepts of how visible light works. What most people consider to be white light is actually the combination of all light on the color spectrum, from red to violet. When white light hits and object, most of the light is absorbed, but certain wavelengths are reflected or transmitted through the object. For example, white light coming in contact with a blue ball will absorb all the colors except for blue, which gets reflected back to our eyes, which is why the ball appears blue. Another example is when light passes through a blue lens, all of the other colors are absorbed, some is reflected, and the rest is transmitted, passing through the lens. The mass spectrometer is designed to measure these levels of absorption.
The spectrometer is first calibrated by setting the frequency of light being shone through a sample, and then creating a blank to set an absorbance reading to compare the sample to. The blank is used to calibrate a neutral reading. So let’s say, for example, you are testing for oxygen levels in blood using mass spectrometry. The blank would contain non-oxygenated blood as the blank, since the other components of the blood sample would remain constant. The frequency would then be set to correspond to the color you are testing for (in this case 450-500 Hz range, the frequency of red light which would not be absorbed by the oxidized blood, or 650-750Hz range, to correspond with the blue spectrum on non-oxygenated blood). Depending on what color light is being shone on the sample, the absorption level would react accordingly. If you are using red light, the absorption value would be lower as more red light is being reflected as the blood is more oxygenated. If you are using blue light, absorption would increase with oxygenation as more blue light is being absorbed by the sample.
This method would be used to test urine samples for compounds that either absorb or reflect light frequencies other than what normal urine would. This would provide an absorption spectrum showing how the sample reacts to each frequency of visible light. This could then be compared to the absorption spectrum of a normal sample of urine to find any anomalies within the tested sample, with some room for error as the translucency of urine is highly affected by the level of hydration in the body. If there is a much higher or lower absorption level of a certain frequency, it can be reasoned the sample has been tampered with.
While this type of test is less common than urine tests, blood tests are virtually impossible to beat. That isn’t to say they aren’t without their own drawbacks though. The first and biggest problem with blood tests is that while dugs and alcohol can remain in the body for extended periods of time, they leave the bloodstream relatively quickly by comparison. Some substances can leave the blood stream in as little as six hours time (for example, LSD on average leaves the blood stream anywhere from 0-3 hours from use). This, combined with the higher cost and longer processing times before getting a result makes this type of test much less common than urine testing. The results can take upwards of one week to process, and requires specialized equipment. Blood tests are most commonly used by insurance companies when determining rates for certain kinds of policies, as well as by potential employers. Most commonly though, blood tests are used in court orders. Due to the short window of time the substances can remain in a person’s bloodstream, the best way to pass this kind of tests is to simply stop taking the substance and wait for your body to purge it from the bloodstream naturally. This process can be sped up by drinking water and eating a healthy diet to speed up the metabolic process. Using other substances to adulterate the sample is not recommended, as the tests run on blood samples can easily pick up adulterating substances and would immediately call the validity of the sample into question.
The use of saliva for drug testing is starting to become more prevalent recently, though like the other methods above, it isn’t perfect either. The biggest benefit of saliva testing is it provides one of the fastest and most non-invasive methods to collect a sample. A cotton swab is simply rubbed up against one of the salivary glands in the mouth (usually one of the glands near the cheek in line with the top molars, or the ones in the area under the tongue). The other form of collection is to have a person spit into the collection basin, but this runs the risk of the sample being contaminated by food or other residue in the person’s mouth. Unfortunately, the actual collection of enough sample for ample testing can be a problem for many physiological reasons. One reason, ironically enough, is that one of the side effects of drug use is dry mouth and the reduction of a salivary response. Due to the small sample sizes, the types of testing done on these salivary samples are also very limited, and salivary drug testing is usually done as an alternative when adulteration or replacement of samples is suspected.