Analytical investigation of plasma-treated carbon fibres.

As-grown and heat-treated vapour grown carbon fibres (VGCF) in the as-prepared state, washed in HCl/H(2)O, and treated in O(2) plasma for different periods have been investigated by means of XPS and scanning electron microscopy (SEM). The surface energy of the carbon fibres before and after plasma treatment was determined from the wetting contact angle. Washing introduced hydroxyl, carbonyl and carboxyl groups onto the fibre surfaces and oxygen plasma treatment increases the total atomic concentration of oxygen up to 17%. This is in good agreement with the value of the polar component of the surface energy. Plasma treatment also enhanced the fibre surface porosity (by etching).

[Occurrence of chlorogenic acids in potatoes]. / Uber das Vorkommen der Chlorogensäuren in der Kartoffel.

Ten varieties of potato cultivated under the same conditions were analyzed for the occurrence of chlorogenic acids by high performance liquid chromatography. 3-O-caffeoylquinic acid (n-chlorogenic acid) is the predominant compound with 22-71 ppm, (on average of 41 ppm) depending on variety. 4-O-caffeoylquinic acid (phi 11 ppm), 5-O-caffeoylquinic acid (phi 7 ppm), 3,4-dicaffeoylquine acid (phi 3 ppm), and at times 3,5-dicaffeoylquinic acid (in traces) were also demonstrated. Caffeic acid compounds are not distributed uniformly in the potato tuber. They occur in strongly decreasing concentration from the outer sections to the inner ones. About 50% of these compounds are located in the potato peel and the adjoining tissue.

[Hydroxycinnamic acid esters in brassicaceous vegetables and garden cress]. / Hydroxyzimtsäureester der Kohlarten und der Gartenkresse.

The esters of caffeic, p-coumaric and ferulic acid with glucose or quinic acid and sinapoylglucose were determined in cauliflower, kale, Brussel sprouts, red, white, Savoy and Chinese cabbage and in garden cress by two different HPLC methods with gradient elution. In addition the occurrence of sinapin (sinapoylcholin) was checked. The pattern of hydroxycinamic acid esters in the Brassica species varied appreciably. In garden cress besides sinapin only sinapoylglucose was found. Sinapoylglucose is dominating in the group of glucose esters besides minor amounts of feruloylglucose. The 5-isomers of quinic acid esters, with neochlorogenic acid (5-caffeoylquinic acid) as the main compound, are dominating among the quinic acid esters. Considering the 3- and 4-isomers of quinic acid esters only 3- and 4-caffeoylquinic acids were determined in lower concentrations. Sinapoylquinic acid could never be recognized. Sinapin was determined in the Brassica species only in few cases in traces.