The Nonmethane Hydrocarbon Intercomparison Experiment (NOMHICE): Tasks 1 and 2

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Abstract
The NOMHICE program has been designed to evaluate current methods being used to determine the ambient levels of various atmospheric nonmethane hydrocarbons, to identify existing problems in these analyses, to correct these problems, and to help ensure quality control of hydrocarbon analyses made by atmospheric scientists throughout the world. To accomplish this, a series of planned experiments (tasks) is now under way which involves all the common classes of the atmospheric hydrocarbons: alkanes, alkenes, alkynes, aromatic hydrocarbons, and the terpenes. The various tasks of the study have been scheduled in order of increasing complexity so that problems can be addressed as they arise. Preliminary results are presented for task 1 and task 2 of a multitask program. Each laboratory used its own analysis and calibration procedures. The first task of NOMHICE involved the circulation of a two‐component, gravimetrically prepared, hydrocarbon mixture of known composition and unknown concentration to 36 participating scientific groups from laboratories throughout the world. This experiment was planned to check on the reliability of the standards employed by each of the participating groups. Task 2 involved the circulation, to participant laboratories, of a more complex, gravimetrically prepared, 16‐component hydrocarbon mixture (unknown composition and concentration) to determine whether suitable separation, identification, and quantification can be made of the individual hydrocarbons present in the mixture. Further tasks are described which will be carried out in the future.