The document provides the physical principles and specifies instrumental requirements for total reflection X‑ray fluorescence analysis (TXRF) spectrometers. This document specifies general procedures for calibration, method development and verification of TXRF measurements and quality control. The document describes measurements with TXRF conditions having a fixed glancing angle below the critical angle of total reflection and considerably enhanced excitation radiation intensity. Although certain definitions of grazing incidence geometry are shown for clarification, this document is not applicable to measurement setups working under such conditions.