1. Scope

Keywords

Rationale

Modern industrial systems increasingly rely on analytical measurements made at concentrations near the lower limit of quantitation to control operations, protect assets, and ensure product quality. In many cases, these measurements are used to predict catalyst life, prevent equipment damage, maintain product performance, or manage safety-related risks. However, current standard practices focus primarily on method validation at the time of development and on ongoing statistical quality control (SQC) in regions well above the LOQ. While SQC practices such as ASTM D6299 are essential for monitoring stability, precision, and bias of analytical systems, they are not designed to demonstrate ongoing capability at the lowest concentrations where uncertainty is greatest and consequences are highest. As a result, laboratories may demonstrate excellent statistical control while unknowingly operating closer to the edge of reliable quantitation than intended. The lower limit of quantitation is not a fixed property of a method. It varies with instrument condition, laboratory environment, maintenance practices, matrix effects, and operator proficiency. Without a standardized practice for validating performance near the LOQ, laboratories and operating organizations rely on assumptions of stability rather than evidence of capability. This can lead to the gradual introduction of higher contaminant levels into processes without detection, reducing operational reliability and increasing economic risk. This practice fills a recognized gap by providing a standardized, method-agnostic framework for validating measurement capability near the LOQ and for documenting the uncertainty associated with low-level results. The practice will support laboratories, operators, and standards developers by improving confidence in critical low-level measurements while complementing existing SQC and validation practices.