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Waters

USP signal-to-noise ratio is not being calculated in Empower 3 - WKB20162

Article number: 20162

SYMPTOMS

  • USP signal-to-noise ratio is not calculated for the highest-concentration injection
  • Other, smaller-concentration injections do have the USP signal-to-noise value calculated
  • Gel Phase Chromatography (GPC)
  • Apex track integration
  • Peak Code S49

ENVIRONMENT

  • Empower 3
  • System Suitability
  • "Use noise centered on peak region in blank injection" is selected
  • In the Integrity tab of the processing method, the Apex Detection start is 6 minutes and the stop is 10 minutes
  • The peak width for this component is about 2 minutes

CAUSE

The "Half Height Multiplier for USP s/n Noise Region" is set too high on the system suitability tab.

FIX or WORKAROUND

In the System Suitability tab in the processing method, change the half height multiplier to a smaller number until the USP s/n is calculated.  See below for an explanation. 

ADDITIONAL INFORMATION

By default, the half height multiplier for USP s/n is 5 in the System Suitability tab. This means that the width of the peak at half of its height is multiplied times 5. The product of that calculation will represent the size of the region of baseline in the blank injection that is used to determine the signal to noise. This section of baseline in the blank injection will be centered around the retention time of the component. Because this one peak is so large, the product of the half height multiplier and the peak width at half height was larger than the Apex Detection time frame that was specified in the Integration tab. Because of this, Empower gave the S49 peak code and could not calculate a signal-to-noise ratio. 

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