Breathalyzer Methods and Facts http://www.craigmedical.com/Breathalyzer_FAQ.htm[5/8/2012 7:07:56 AM] Click to Enlarge. Quality Medical & Forensic Diagnostics Since 1984 ... May 8, 2012 Electronic Alcohol Breath Analyzers (Breathalyzers) • Scientific Method and Technology • Specificity and Accuracy Expectations SCIENTIFIC METHOD AND TECHNOLOGY When consumed, alcohol is immediately absorbed into the blood capillary structure of each successive body tissue and organ it is directly exposed to. Alcohol's rapid rate of absorption begins in the soft tissues of the mouth, continues through the esophagus, into the stomach and finally, the small intestine. Alcohol is somewhat unique in that as it enters the blood stream, it's chemical structure is not metabolized but remains unaltered and intact. Consequently, alcohol becomes a separate and definable component of blood flow. As blood flows into and through the alveoli (air sacs) in the membranes of the lungs, carbon dioxide molecules are exchanged for oxygen molecules. Because alcohol will readily evaporate from a solution and is highly volatile, alcohol molecules are released w ith t he carbon dioxide molecules during this gas exchange. Therefore the concentration of alcohol molecules in the alveolar air of expelled breath is related to the concentration of the alcohol in the blood. As the alcohol in the alveolar air is exhaled, it can be detected by a breath alcohol testing device. Because of this m olecular exchange in the lung tissue, the correlation between alcohol concentrations in the blood stream and the expelled breath can be established by measuring the exchange rate, or evaporation rate of alcohol in solution. This rate is then expressed as a constant ratio of blood alcohol concentration (BAC) to breath alcohol concentration. Using this constant or fixed ratio wit h a measured breath alcohol content, equivalent blood alcohol content can readily be calculated. The ratio of breath alcohol to blood alcohol is 2,100:1. Thi s means that by volume, 2,100 milliliters (ml) of alveolar air will contain the same am ount of alcohol as 1 ml of blood. If a person's BAC measures 0.08, it means that there are 0.08 grams of alcohol per 100 m l of blood. Electronic m easuring devices have been developed to measure breath alcohol concentration using a fu el cell gas sensor that is specifi c to alcohol molecules. The fuel cell sensor has t wo platinum electrodes wit h a porous acid-electrolyte material sandwiched between them. As exhaled air flows past one side of the fuel cell, the platinum oxidizes any alcohol molecules in the air to produce acetic acid, protons and electrons. The formula for reactive oxidation of the alcohol (ethanol) molecule can be chemically stated. If hydrogen atoms are caused to be stripped by reaction from the right carbon of ethanol in the presence of oxygen, t he end product is acetic acid, the m ain component in vinegar. The molecular structure of acetic acid is then expressed as O = H3C - C - O - H where C is carbon, H is hydrogen, O is oxygen, the hyphen is a single c hemical bond between the atom s and t he = symbol i s a double bond between the atoms. When ethanol is oxidized to acetic acid, two free protons and two free electrons are released from the ethanol molecule. Thes e tw o electrons flow through a wire fr om the platinum electrode in the fuel cell sensor to an electrical- current meter and then to the platinum electrode on the other side of the cell. The two protons move through the lower portion of the fuel cell and combine with oxygen and the electrons on the other side to form water. The more alcohol from the breath sample that is oxidized, the greater is the number of free electrons that are produced resulting in the greater amount of the electrical current that is produced. A microprocessor measures this electrical current to extrapolate total breath alcohol content then calc ulates the equivalent BAC using the constant ratio discussed previously. SPEC I FICI TY AND ACCURACY E XPEC TATI ONS As stated above, t he basic t echnology of these type devices is essentially similar. A gas specific microchip sensor is used to m easure the amount of a specific target gas (or hydrocarbon) contained in a specific volume of air (exhaled breath) by determining the electrical charge produced by the chem ical reaction converting eth anol to acetic acid. Model qual ity and cost are differentiated by the sensor technology employed, processor type, internal circuit board, features, options and other structural components. ...Wholesale Direct Prices on Home Health Diagnostic Test Kits... Alcohol and Drug of Abuse Screening, Pregnancy and Fertility Testing,