Gas chromatography GC is a widely used analytical technique for separating and analyzing volatile compounds in a mixture. It can be used to determine the percentage composition of a mixture of two or more compounds by measuring the area under the peaks corresponding to each compound in the chromatogram. Here's a step-by-step process on how to use GC for this purpose:1. Sample preparation: Prepare the sample by dissolving it in a suitable solvent, if necessary, and injecting it into the GC instrument.2. Separation: The sample is vaporized and carried through a column by an inert gas carrier gas , such as helium or nitrogen. The column is typically packed with a stationary phase, which can be a solid or a liquid coated on a solid support. The compounds in the mixture interact with the stationary phase and are separated based on their volatility and affinity for the stationary phase.3. Detection: As the separated compounds exit the column, they are detected by a suitable detector, such as a flame ionization detector FID or a mass spectrometer MS . The detector generates a signal proportional to the concentration of each compound, which is then plotted as a function of time or column retention time, resulting in a chromatogram.4. Data analysis: The area under each peak in the chromatogram is proportional to the amount of the corresponding compound in the mixture. By comparing the peak areas to those of known standards, the percentage composition of the mixture can be determined.Several factors can affect the accuracy of the results obtained using GC:1. Sample preparation: Inaccurate sample preparation, such as improper weighing, incomplete dissolution, or contamination, can lead to errors in the results.2. Instrument calibration: The GC instrument must be properly calibrated to ensure accurate retention times and peak areas. This includes the proper selection of the column, carrier gas flow rate, and temperature program.3. Peak resolution: If the peaks of the compounds are not well-resolved, it can be challenging to accurately determine the area under each peak. This can be addressed by optimizing the column and temperature program or using a more selective stationary phase.4. Detector sensitivity and linearity: The detector must be sensitive enough to detect the compounds of interest and have a linear response over the concentration range of interest. Non-linearity can lead to inaccurate quantification.5. Internal or external standards: The use of internal or external standards can help improve the accuracy of the results by accounting for variations in the sample preparation, injection, and instrument response.In summary, gas chromatography can be used to determine the percentage composition of a mixture of two or more compounds by measuring the area under the peaks in the chromatogram. The accuracy of the results depends on several factors, including sample preparation, instrument calibration, peak resolution, detector sensitivity and linearity, and the use of internal or external standards.