(GC Instrument Experiment) Determination of Ethanol Concentration in Lab Report

(GC Instrument Experiment) Determination of Ethanol Concentration in Biological Fluids using Gas Chromatography - Lab Report Example The BAC level in all 50 states of the US is set by law at 0.08% w/v a value, which is much higher in comparison to other countries. Other countries have BAC limits of 0.03% w/v or even less (International Center for Alcohol Policies). The use of gas-liquid chromatography in the modern science has eliminated the complex nature of the matrix affecting the analysis of ethanol in blood previously (Jones and Pounder 12). The sample size employed in gas-liquid chromatography is also small hence making the method convenient for analysis of small samples. In gas chromatography, the gaseous mobile phase, which is referred to as the carrier gas, conveys the analyte in the column (Harris 528). Mostly, inert gas such as helium and nitrogen are used as mobile phase while non-polar liquids such as polyethylene glycol can be used as stationary liquid phase (Harris 528). Separation is founded on the dispersal of the analytes between the mobile and stationary phases. The analyte concentration in the gas phase affects its elution since high analyte concentration means more time is spent in the mobile phase as well as the stationary phase (Colin 19). Short analysis time and high precision make it a method of choice. A comparison between flame ionization detectors (FID) and electron capture detectors (ECD) shows that FIDs are highly sensitive to almost all organic compounds, have a wide linear response range that surpasses 107, have low maintenance requirements and are less expensive to acquire and operate compared to ECDs (Harris 543). Five ethanol standards were prepared in a 20 mL gas-tight vial by mixing ca. 0.5% w/w ethanol and ca. 0.5% w/w of tert-butanol in water. The table below summarizes the preparation. tert-Butanol was used as the internal standard. A Shimadzu 14A GC with a flame ionization detector was used. Polyethylene glycol was used as the stationary phase, and the column temperature