Chromatographic situations are created for varying peak resolution and relative peak size. In this case, the peak size of the smaller peak is always at least 5% of the larger peak, and resolution is varied from 4.0 to 1.0. All separations are then integrated, using both area and height, by four different baseline methods: drop, valley, exponential skim, and Gaussian skim. Integration errors are calculated using reference calibration injections. The results demonstrate that the drop and Gaussian skim methods produce the least error in all situations. The valley method consistently produces negative errors for both peaks, and the skim method generates a significant negative error for the shoulder peak. Peak height is also shown to be more accurate than peak area. As the relative peak size increases, resolution below 1.0 will generate unacceptable errors, and resolution greater than 1.5 is necessary to minimize integration errors.

Integration of chromatographic peaks (determination of height, area, and retention time) is the first and most important step in the data analysis part of all chromatography-based analytical methods. This information is used for all subsequent calculations, including construction of calibration curves and calculation of unknown concentrations. Clearly, any error in measurement of peak size will produce a subsequent error in the reported result.

Figure 1

For any of these methods, analysts must also choose between measuring peak size by either area or height. It is clear that these integration options are likely to generate significantly different analytical results, and analysts must decide which approach provides better accuracy.