Some recent developments in reference methodology within the United Kingdom

The UK Valid Analytical Measurement Programme has pump-primed developments in chemical metrology, through a major project on reference methodology and reference materials. This paper provides an overview of developments durin g 1994-1997 and covers work on primary methods for trace inorganic and trac e organic analysis, including the use of isotope dilution mass spectrometry : studies of sample pre-treatment including digestion, extraction, and sepa ration aimed at improving this weak link in the traceability chain; priorit isation, production and marketing of both pure substance and matrix referen ce materials; and international collaboration concerned with interlaborator y comparisons and the development of concepts terminology and systems to un derpin the international chemical measurement system. References are given to a number of papers covering specific parts of the programme.