Statistically sound calibration curves for chromatographic methods involving negative response data

Area of Science:

• Analytical Chemistry
• Chromatography

Background:

• Negative chromatographic peaks present calibration challenges in quantitative analysis.
• Accurate quantification of ions like ammonium is crucial in various chemical solutions.

Purpose of the Study:

• To present a statistical procedure for calibrating chromatographic methods that produce negative peaks.
• To demonstrate the technique's application in ion-chromatographic analysis of ammonium ions.

Main Methods:

• Development of a statistical calibration procedure for negative chromatographic peaks.
• Application of the procedure to ion-chromatography of ammonium ions in methanesulfonic acid solutions.
• Utilizing a peak-integration protocol and ordinary least squares regression analysis.

Main Results:

• A quadratic model successfully fitted calibration data for ammonium ions in the 1 to 5 ppb concentration range.
• The developed method achieved a precision of approximately ± 0.5 ppb at a 95% confidence level.

Conclusions:

• The presented statistical procedure effectively calibrates chromatographic methods with negative peaks.
• The technique provides accurate and precise quantification of ammonium ions at low concentrations (ppb levels).