Minimum required signal-to-noise ratio for optimal precision in HPLC and CE

• Published in: Electrophoresis 2012-06, Vol.33 (11), p.1509-1516
• Main Authors: Meyer, Christoph, Seiler, Patricia, Bies, Celine, Cianciulli, Claudia, Wätzig, Hermann, Meyer, Veronika R.
• Format: Article
• Language: English
• Subjects: Capillary electrophoresis; Chromatography, High Pressure Liquid - methods; Chromatography, High Pressure Liquid - standards; Electrophoresis, Capillary - methods; Electrophoresis, Capillary - standards; High-performance liquid chromatography; Pharmaceutical Preparations - analysis; Proteins - analysis; Regression Analysis; Repeatability of chromatographic analyses; Reproducibility of Results; Signal-To-Noise Ratio
• ISSN: 0173-0835; 1522-2683
• DOI: 10.1002/elps.201100694

In a survey, results of more than 100 assay determinations of various analytes (active pharmaceutical ingredients, methylparabene, chlorthalidone, and proteins) at different concentration levels were collected with signal‐to‐noise ratio (S/N) levels between 2 and higher than 10 000. It must be concluded that without having a S/N of at least 50, repeatabilities (combination of injection, separation process, and integration) of 2% cannot be achieved, in contrast to the general assumption that a S/N of 10 is sufficient for analytical HPLC. These data now confirm an earlier assumption with a much broader fundamental of measurements. The empirical functions %RSD = 58/(S/N) + 0.30 (for HPLC data) and %RSD = 73/(S/N) + 1.07 (for CE data) could be derived. It was shown that a S/N of greater than 100 is necessary for optimal precision. Before optimizing HPLC or CE methods, for example, for sample pretreatment, S/N > 100 should be the prerequisite, else optimal precision will not be achieved. Only after the detection‐related scatter is sufficiently reduced, other sources of variation can be successfully tackled.