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Determination of Lidocaine in Urine Samples Using GC Analysis
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To purpose of this experiment is to quantify lidocaine present in a urine sample. This is achieved by running gas chromatography. There are a number of standards made from a stock solution.
 Lidocaine is a local anaesthetic. It is typically combined with other medications to treat soreness and irritation on skins such as eczema and is used to numb haemorrhoids around the anal area. Lidocaine is also used to relieve post-shingle patients. It helps sooth the nerve pain felt. Lidocaine is also used for controlling contractions in the heart (cardiac arrhythmias).  It works as it blocks the nerve signal pathways.  When pain occurs in the body, it happens in the pain nerve endings. It prevents sodium from entering the nerve ending. This stops the pain. Lidocaine has a molecular weight of 232.343g/mol and a molecular formula of C14H22N2O.
To analyse the amount of lidocaine, standards must be made. Lidocaine is a liquid and must undergo ‘liquid/liquid’ extraction.  Liquid/liquid extraction is the separation of one solute in one solvent to another. It is also known as ‘’partitioning’’. The solvents must be immiscible. This means they should not mix and if they do, only a small amount should mix. The liquid/liquid extraction depends on the polarity of the solute. For example, water and oil. Water is more polar and is also denser than oil. The oil remains at the top of the solute in the organic layer. The reason they don’t mix is due to the repulsion between the polar and non-polar molecules. There is poor attraction between polar and non-polar molecules due to the lack of dipoles present. Dipoles are intermolecular forces that are formed. They happen due to an unequal sharing of electrons. Due to the lack of dipoles, the polar compound cannot form bonds with the non-polar. This causes the polar compound to form intermolecular forces and repel the non-polar compounds. Non-polar compounds are known as ‘organic layers’ and polar compounds are known as ‘aqueous layers’. These layers separating/partitioning is achieved by shaking the solute.  The distribution coefficient can be measured when equilibrium has happened in the solute. It is calculated by
C2= 10mg/ml (highest concentration)
V2= 10ml (total volume of volumetric flask)
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