The percent water in methyl alcohol can be determined by gas chromatography using
a capillary column coated with a non-polar stationary phase and a thermal
conductivity detector. A series of calibration standards yielded the following results:
Water content (% w/w) Peak height (arbitrary units)
0.00 1.15
0.0145 2.74
0.0472 6.33
0.0951 11.58
0.1757 20.43
0.2901 32.97
Why are chromatographic peaks broader than would be expected solely on
the basis of the random nature of solute migration through a chromatographic
column?
To determine the percent water in methyl alcohol using gas chromatography, you will need to analyze the calibration standards and their corresponding peak heights. The peak height is a quantitative measure of the amount of water present in each standard.
First, plot a graph with the water content (% w/w) on the x-axis and the peak height (arbitrary units) on the y-axis. This will help visualize the relationship between the two variables.
Next, determine the equation for the trendline that best fits the data points on the graph. This equation will allow you to calculate the percent water based on the peak height.
Once you have the equation, you can substitute the observed peak height of an unknown sample into the equation to calculate its corresponding percent water content.
Let's go through the process step by step using the provided data:
Step 1: Plot the calibration standards on a graph:
In this case, the x-axis represents the water content (% w/w) and the y-axis represents the peak height (arbitrary units).
Water content (% w/w) | Peak height (arbitrary units)
0.00 | 1.15
0.0145 | 2.74
0.0472 | 6.33
0.0951 | 11.58
0.1757 | 20.43
0.2901 | 32.97
Step 2: Draw a best-fit line or curve through the data points to represent the trendline. The type of trendline will depend on the shape of the data points.
Step 3: Determine the equation for the trendline. This equation will be used to calculate the percent water for an unknown sample.
Step 4: Substitute the observed peak height of an unknown sample into the equation to calculate its percent water content.
If you provide the equation of the trendline or a plot of the calibration standards, I can help you further in calculating the percent water for an unknown sample.