Achieving Lowest Detection Limits in ICP-MS to Calibrate at ppq Levels Application Note · PlasmaQuant MS Elite S

Introduction

ICP-MS, mass spectrometry with inductively coupled plasma is a powerful multi-element technique to quantify elements at lowest concentrations. ICPMS is capable to analyze almost the entire periodic table of elements in various matrices. In the determination of trace and ultratrace concentrations, not only the instrument performance but also the laboratory environment and correct sample handling are crucial factors. This application note highlights the capabilities of the PlasmaQuant MS Elite family in the accurate and precise determination of lowest quantities of analytes.

The limit of detection (LOD) is defined as the lowest quantity that can be distinguished from a blank with a certain confidence level. The instrument detection limit is typically defined as the concentration of an analyte, which gives a signal equal to measurement above the blank solution. This equals a probability of about 1% for a false positive error (α) meaning 1% chance of assigning a signal originating from the blank to an analyte. However, at this concentration there is a 50% chance of assigning an analyte signal to the noise (false negative error (β) = 50%). For that reason and to minimize the false negative errors, the limit of quantification (LOQ) is often estimated as the concentration which leads to a signal as high as 10x noise of the blank solution measurement above the blank intensity. Hereby the factor 10 is historically established and commonly chosen in analytical chemistry. At this concentration the relative imprecision of the method is 5%. However, different factors may be used depending on statistical demands. The relationship between noise, limit of detection and limit of quantification is schematically.