Determination of Blood Alcohol Level

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Determination of Blood Alcohol Level

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Introduction

Determination of the Blood Alcohol Level is a procedure performed to measure the amount of alcohol present in an individual 's blood . It is usually calculated as weight of alcohol present per volume of blood The blood alcohol content can be determined in a number of methods However , the most commonly used method is by using a machine that actually determines the exact amount of alcohol expelled by the lungs when the individual breathes out . This machine is generally known as

a `Breathalyzer (trademark name . The breathalyzer was originally invented by R .F . Borkenstein , for which he was granted a Patent by the US Patent and Trademark Office in 1958 . The machine uses a chemical reaction involving potassium dichromate and alcohol . Potassium dichromate is initially distinct yellow in color . When it reacts with ethanol (a form of alcohol , it becomes more transparent in color directly proportional to the level of alcohol present in the breath . A specialized instrument known as `spectrophotometer ' is used to screen the color of the potassium dichromate solution for transmission and absorbance of light , and provides the reading of the level of alcohol in the breath (which in turn is a measure of the alcohol level present in the blood . In this manner , the blood alcohol level can be determined

Procedure

The blood alcohol content is to be determined after creating a calibration curve . This curve can be prepared by using samples containing known concentrations of alcohol . A spectrophotometer can be used to monitor the color of potassium dichromate to get certain values These values can be plotted or marked on a graph against the alcohol concentrations to get the calibration curve . Using this calibration curve , the level of alcohol in a sample (containing unknown amount of alcohol ) can be determined after screening it with the spectrophotometer (so as to monitor its color and get a value of the amount of light transmitted or absorbed

Four solutions containing varying concentrations of alcohol (such as 0 .2 , 0 .4 , 0 .6 and 0 .8 ) should be prepared . Using the formula : M1V1 M2V2 (where M1 is the initial concentration of alcohol , M2 is the final concentration of the solution , V1 is the initial volume of the concentrated solution and V2 is the final volume of the solution respectively . Solutions containing 100mL of each concentration should be prepared , and labeled according to their respective concentrations in 100mL volumetric flasks

Take 5 tests tube and put 5mL of dichromate solution using a 5mL volumetric pipette . Add 1mL of the alcohol solutions of different concentrations prepared (such as 0 , 0 .2 , 0 .4 , 0 .6 , and 0 .8 ) to each of the test tube . To the test where 0 alcohol solution is to be added put distilled water (instead of any alcohol solution . Each test tube should be labeled clearly according to the alcohol concentrations added Each of these solutions should be mixed thoroughly using a clean and dry stirring rod . Separate...