Chemistry: analytical and immunological testing – Oxygen containing – Hydroxyl containing
Patent
1994-03-02
1996-03-05
Snay, Jeffrey R.
Chemistry: analytical and immunological testing
Oxygen containing
Hydroxyl containing
436900, 422 84, 422 98, 128719, G01N 3348
Patent
active
054967406
DESCRIPTION:
BRIEF SUMMARY
This invention relates to methods and apparatus for determining the concentration of volatile oxidisable components of liquid systems and in particular, but not exclusively, for the detection of body alcohol concentration.
Throughout much of the World the penalties for driving whilst under the influence of alcohol are steadily increasing and this has lead to a need for apparatus which will enable individuals to determine their body alcohol concentration with accuracy. A wide range of "self testers" have accordingly come on to the market, but in general those which are relatively cheap are dangerously inaccurate and it is difficult to find any viable apparatus; below 100.
In addition there are other circumstances where alcohol content is of interest to ordinary members of the public, for example in home brewing and home wine making.
From one aspect of the invention there is provided apparatus for measuring volatile oxidisable or reducible components of a liquid system, comprising a body having an inlet insertable in a head space over the liquid system, an electrical sensor, means for drawing a sample from the head space through the inlet into the sensor and means for displaying the component concentration in the liquid system detected by the sensor.
It will be appreciated that the body can contain all of the elements of this apparatus and conveniently the body may be made generally in the form of a pen or syringe so that it can be readily carried in the user's pocket. In that case the inlet is preferably formed at or adjacent one end.
Such a construction is particularly convenient if the apparatus is to be used for self-testing for body alcohol concentration because it enables an entirely novel procedure for testing. This is based on the fact that alcohol disperses equally throughout all the body fluids including saliva. The Applicant has realised that when closed a person's mouth is the equivalent of a head space vessel and that a known concentration of the alcohol in the saliva will evaporate into the air contained within a closed mouth until equilibrium is achieved. Tests have shown that this is in around 20 seconds dependent on the ambient and mouth temperature. Measurements may be made either above or below the tongue.
Thus if the user places the inlet into his mouth and closes his lips around the body he can draw off a sample of the air, after a 20 second wait, into the sensor and thus achieve a reading of his body alcohol concentration.
In the light of this, the sample drawing means may comprise a spring-loaded or motor driven/piston or diaphragm disposed within a cylinder in the body which is in communication with the inlet and the sensor. Detent means may be provided for retaining the piston or diaphragm in a set or pre-sampling position and the detent may either be manually releasable or it may be automatically released. In the latter case the detent release may occur in response to some detection of the ambient conditions in the mouth. Thus it is preferred that the apparatus also includes a thermistor, or other temperature detecting device, which will detect when the air in the user's mouth reaches a predetermined temperature, for example normal body temperature. This will not only be an indication that the mouth has been closed for a sufficient period but will also overcome problems that arise due to the temperature dependence of the alcohol content of the air. Additionally or alternatively the body may be provided with a photoelectric cell, or other light detection device, which will detect when the mouth is fully closed. Additionally or alternatively it may set a timer. In order to keep the apparatus as cheap as possible it may be desirable to cause the thermistor and/or for the photo-electric cell to light an indicating light or activate an audible warning such as a buzzer or beeper on the body rather than cause automatic releasing of the piston or the like. In this case the user will manually release the detent or operate the switch when the light is illuminated or the beeper sounds. Conveni
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Lion Laboratories Plc
Snay Jeffrey R.
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