A method, based on high-performance liquid chromatography, is described for the determination of chlorogenic acid isomers in instant coffee. Identification of the individual components was assisted by the preparation of isomeric mixtures by the isomerisation of available compounds and quantification based on published ultraviolet molar absorptivities. A number of extraction and clearing techniques were studied to determine the optimum conditions for the recovery of all the isomers present. The developed method was applied to a wide range of commercially available instant coffees.

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The reactions γp → ηp and γp → η 0 p are measured from their thresholds up to the center-of-mass energy W ¼ 1.96 GeV with the tagged-photon facilities at the Mainz Microtron, MAMI. Differential cross sections are obtained with unprecedented statistical accuracy, providing fine energy binning and full production-angle coverage. A strong cusp is observed in the total cross section for η photoproduction at the energies in the vicinity of the η 0 threshold, W ¼ 1896 MeV (E γ ¼ 1447 MeV). Within the framework of a revised ηMAID isobar model, the cusp, in connection with a steep rise of the η 0 total cross section from its threshold, can only be explained by a strong coupling of the poorly known Nð1895Þ1=2 − state to both ηp and η 0 p. Including the new high-accuracy results in the ηMAID fit to available η and η 0 photoproduction data allows the determination of the Nð1895Þ1=2 − properties.

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