This video demonstrates how to calculate the areas of the peaks that you obtain when you perform a gas chromatography experiment. Gas chromatography is a technique that allows the separation of volatile organic compounds based on their polarity. While the sample is running, a basic strip chart recorder prints the gas chromatogram. The areas of the peaks are calculated manually. To do this calculation, we assume that each peak in a chromatogram is a triangle. Although the peaks might not be perfect triangles, this is a close enough approximation. In this chromatogram, we have two peaks corresponding to two products. We will use the ratio of the areas to determine the ratio of the two products. The larger peak corresponds to the major product, the smaller peak corresponds to the minor product. Begin by drawing the baseline. Let's work on the larger peak, the major product first. To calculate the area, measure the height of the peak from the baseline, and measure the width of the peak at the half height. The area of the triangle is equal to the product of the height times the width at half height. Now let's do the same thing for the smaller peak. To calculate the area, measure the height of the peak from the baseline, and measure the width of the peak at half height. The area of the triangle is equal to the product of the height times the width at half height. Let's review the calculations we have performed. Peak A is the minor product. It has a height of 40 millimeters, and a width at half height of 17 millimeters. The area of peak A is 680 millimeters squared. Peak B is the major product. It has a height of 122 millimeters, and a width at half height of 19 millimeters. The area of peak B is 2,320 millimeters squared. The total area is the sum of the area of peak A plus the area of peak B. 680 plus 2,320 equals 3,000 millimeters squared. The percentage of compound A in the mixture is 680 divided by 3,000 times 100 percent, which comes out to 22.7 percent. The percentage of compound B in the mixture is 2,320 divided by 3,000 times 100 percent, which comes out to 77.3 percent. If we add the two percentages, we get 100 percent, since we had only two products, it's fair to assume that their area should add up to 100 percent.