What is alcotester (alcometer)?
Alcometer is the mean of measuring technique, intended for measuring or concentration of alcohol in a man expirate or concentration of alcohol in blood of man (on an expirate). If the error of alcometer is rationed, it is subject a metrology check and can be used for official procedures of examination on the state of alcoholic intoxication.
First alcotesters appeared at the beginning of 1930th in the USA, and could show the fact of alcohol only. To determine the amount of alcohol in blood alkotesters of that time were yet unable. Alcotesters began to be regularly used a police only from 1939, however much their possibilities began to approach modern only in a few decades (the first «respiratory tube» was patented the German firm Drager only in 1953).
Classification of alcometers on the type of sensor
A sensor of alcohol in alcometer is the structurally isolated primary measuring transformer, perceiving external influence (being of molecules of alcohol is in the air blown through a sensor) and transforming it in the signal of measuring information, comfortable for a transmission, treatment or registration. On the type of built-in in a device sensor select three groups of alcometers: with semiconductor, electrochemical or infra-red sensors.
Alcometers with semiconductor sensors. This group of alkometers is small in numbers because of instability of technical and metrology descriptions of devices.
A semiconductor sensor is a matter with a porous crystalline structure, which is neat so, that at blowing through of expirate through the sensor of molecule of alcohol sorbs the volume of sensor and change conductivity of this matter. An electric current changes through a sensor, and outwardly it looks as a change of number on the display of device or rejection of pointer, or luminescence of certain indicator. A problem of these sensors is in that except for the molecules of alcohol other littlemolecular connections of organic matters, alike on a structure and sizes on the molecules of alcohol, can sorbs in their volume (for example: ammonia, sulphuretted hydrogen, ketonic bodies).
Basic properties of semiconductor sensor:
1. Low selectivity in
relation to an ethanol;
Alcometers with electrochemical sensors. Swingeing majority of professional alcometers today behaves exactly to this group.
An electrochemical sensor is an electrochemical cell with two platinum electrodes, on the anode of which a catalyst, specific in relation to an ethanol, is besieged. In presence this catalyst exactly an alcohol enters into a redoxreaction with the selection of lone electrons. In regard to these sensors there is the known error, that they require replacement with regularity in one year. It not so. Actually, they regularly serve 5 - 7 years, because a catalyst at a reaction is present, but not expended.
Basic properties of electrochemical sensor:
1. High selectivity in
relation to an ethanol, high sensitiveness and exactness;
Alcometers with infra-red sensors. It is stationary devices, used mainly in laboratory terms or in the movable points of medical examination.
Devices use principle of absorption of infrared the pair of alcohol. It is spectrophotometers, adjusted on a certain wave-length absorption. The modern devices of this type analyse absorption of infra-red spectrum at once on two waves, that provides high exactness of measurings and good selectivity of analysis.
Basic properties of infra-red sensor:
selectivity in relation to an ethanol;
Units concentration of alcohol in blood
Under concentration of alcohol in blood the concentration of ethanol is understood, shown in ‰ - promille (thousandth stakes of volume). For example, expression «concentration of alcohol in blood 1,5 promille», that there is a 1,5 milliliter of pure ethanol in one litre of blood (more precisely speaking, in one litre of mixture of blood with a pure ethanol).
The found out the concentration of ethanol in blood is estimated on a simple chart - the degree of alcoholic intoxication corresponds every interval of concentrations. For determination of degree of expressed alcoholic intoxication at dissection, in obedience to the Methodical pointing of Minzdrav the USSR from 03.07.1974, a next reference chart is used:
- absence of influence
of alcohol - äî 0,5 promille;
A calculation of concentration of alcohol is in blood
The Swedish chemist Erik M. P. Vidmark developed a formula for determination of maximal in theory possible concentration of ethanol in blood (published in 1932) which is used now:
where: c - is a concentration of alcohol in blood in ‰, A -is mass of the had a drink clean alcohol in grammes, m - is mass of body in kilograms, r - is a coefficient of distributing of Vidmarka (0,70 - for men, 0,60 - for women).
For the obtain of the real concentration of ethanol in blood from expected on the above-mentioned formula it is needed to subtract from mass of the had a drink pure alcohol A a from 10% (use of alcohol on an empty stomach) to 30% (use of alcohol on a full stomach) so-called deficit of resorption, as part of alcohol does not come to peripheral blood.
For the calculation of amount of the had a drink alcohol a next formula is used:
It should be noted that these formulas are not taken into account by a few factors, influencing on the concentration of alcohol in blood of man. In particular, the period of time which an alcohol was used during is not taken into account. The type of swizzle is not taken into account (speed of suction in blood of alcohol, contained in different swizzles, different). Also not taken into account whether there was an alcohol used on a hungry stomach or accompanied eating. Not taken into account and that, what food was used to, in time, and after the use of alcohol. Therefore these formulas rather express general conformity to law - than less than mass of body, the higher concentration of alcohol in blood at an identical amount had a drink, what is give the real quantitative estimation of concentration of alcohol.
Excretion of alcohol from an organism
Phase of suction or resorption. Usually an alcohol gets in an organism at the use of drinks and sucked in through the mucous membranes of gastroenteric highway. Suction begins in an oral cavity, gullet and stomach. From the of short duration contact of mucous membranes of oral cavity and gullet with an alcohol the stake of rezorbirovannogo alcohol is uttery small. In a stomach sucked in about 20% from the general volume of the had a drink alcohol. Practically all other alcohol is sucked in in a thin intestine. Practically all other alcohol is sucked in in a thin intestine. At an empty stomach resorption is closed approximately in 30-60 minutes. After suction in a bloodstream, insignificant part of alcohol in the unchanged kind begins to be emited through lights, part is again return in a stomach. Part of alcohol, on unknown to date reasons, is lost and does not come to the peripheral bloodstream. At an empty stomach approximately 10% is lost, and at complete 30% the had a drink alcohol (so-called "deficit of resorption"). The deficit of resorption depends also and from the concentration of alcohol in drink.
Phase of diffusion or distributing of alcohol on an organism. In the beginning concentration of alcohol in arterial blood higher what in venous, smoothing of concentrations goes after. Organs with more high maintenance of water arrive at more high concentrations, than organs with low maintenance. Especially quickly concentrations become level in an organ and in a bloodstream in a cerebrum and in kidneys.
Phase of excration or elimination. The decline of concentration of alcohol in blood goes in course of time, mainly, due to a chemical reaction with transformation of ethanol through the hepatic enzyme of alcohol dehydrogenase in acetaldehyde. 90-95% is by it by a way utilized from all resorpded alcohol. Numerous independent researches rotined in many countries, that middle physiological index of leadingout of ethanol for a hour (so-called middle speed of excration of ethanol from an organism) 0,15 promille. This value depends neither on a floor nor from mass of body and, even, does not change in the cases of the far gone stages of diseases of liver. It is in practice possible to use knowledge of this parameter for timing achievement of the state of «sobriety». For example, for elimination (excration) 1,5 ‰ alcohol from blood required about 10 hours.