How is selectivity defined in analytical methods?

Selectivity in analytical methods refers to the ability of an analytical technique to distinguish the analyte of interest from other components present in the sample. This characteristic is crucial because in real-world samples, the target analyte often exists alongside a matrix of various other substances that may interfere with the measurement. High selectivity means that the method can accurately identify and quantify the analyte without significant interference from these other substances, thereby ensuring the reliability and accuracy of the results.

In contrast, the other options focus on different aspects of analytical chemistry. Measuring the total quantity of all components pertains to quantitation or total analysis rather than selectivity. Consistency of results across multiple tests relates to precision and reproducibility rather than the ability to differentiate between components. Lastly, separating substances based on their weight is more aligned with separation techniques like centrifugation or chromatography, which may contribute to selectivity but do not define it on their own. Therefore, the definition of selectivity as the ability to discriminate between the analyte and other components is fundamental in analytical chemistry for accurate and meaningful interpretations of results.