Worldwide proficiency test for routine analysis of <i>δ</i> ² H and <i>δ</i> ¹⁸ O in water by isotope‐ratio mass spectrometry and laser absorption spectroscopy

Abstract

The leading cause of outliers appeared to be improper calibration or compromised storage of laboratory standard and primary reference waters; hence the importance of judicious storage of lab standards cannot be understated. The deprecated practice of single standard normalization was identified as a problem for some laboratories. We further recommend that laboratories strive to report parsimonious long-term precisions based upon control standards, and to improve quantification and correction for LAS instrumental drift and inter-sample carryover effects.