Method validation is one of the measures universally recognized as a necessary part of a comprehensive system of quality assurance in analytical chemistry. In the past, ISO, IUPAC, and AOAC International have cooperated to produce agreed protocols or guidelines on the "Design, conduct and interpretation of method performance studies" [1], on the "Proficiency testing of (chemical) analytical laboratories" [2], on "Internal quality control in analytical chemistry laboratories" [3], and on "The use of recovery information in analytical measurement" [4]. The Working Group that produced these protocols/guidelines has now been mandated by IUPAC to prepare guidelines on the single-laboratory validation of methods of analysis. These guidelines provide minimum recommendations on procedures that should be employed to ensure adequate validation of analytical methods. A draft of the guidelines has been discussed at an International Symposium on the Harmonization of Quality Assurance Systems in Chemical Laboratory, the proceedings from which have been published by the UK Royal Society of Chemistry.

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The ' H and I9F n.m.r. spectra of several monofluoro-olefins are reported. Coupling of vinylic fluorine t o hydrogen bound to sp3-hybridised carbon has been observed over three, four, and five bonds. The fourbond 'allylic' F-H coupling has been examined in detail, with FPT-INDO calculations for several cases. The trans-CH0C:CF coupling changes sign as the HC-C:C torsion angle varies, as predicted, but the cis-

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