Tangent skim modes

When tangent skimming is enabled, four models are available to calculate suitable peak areas:

• Exponential curve

• New exponential skim

• Straight line skim

• Combined exponential and straight line calculations for the best fit (standard skims)

Exponential Curve

This skim model draws a curve using an exponential equation through the start and end of the child peak. The curve passes under each child peak that follows the parent peak; the area under the skim curve is subtracted from the child peaks and added to the parent peak.

 

Exponential skim

New exponential curve

This skim model draws a curve using an exponential equation to approximate the leading or trailing edge of the parent peak. The curve passes under one or more peaks that follow the parent peak (child peaks). The area under the skim curve is subtracted from the child peaks and added to the main peak. More than one child peak can be skimmed using the same exponential model; all peaks after the first child peak are separated by drop lines, beginning at the end of the first child peak, and are dropped only to the skim curve.

 

New exponential skim

Straight Line Skim

This skim model draws a straight line through the start and end of a child peak. The height of the start of the child peak is corrected for the parent peak slope. The area under the straight line is subtracted from the child peak and added to the parent peak.

 

Straight line skim

Standard Skims

This default method is a combination of exponential and straight line calculations for the best fit.

The switch from an exponential to a linear calculation is performed in a way that eliminates abrupt discontinuities of heights or areas.

• When the signal is well above the baseline, the tail-fitting calculation is exponential.

• When the signal is within the baseline envelope, the tail fitting calculation is a straight line.

The combination calculations are reported as exponential or straight tangent skim.