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The hydrochlorides from tetracycline and six tetracycline derivatives *-7-dimethylamino-6-des-methyl-6-desoxytetracycline [minocycline], 7-chlorotetracycline [chlorotetracycline], 7-chloro-anhy-drotetracycline [anhydrochlorotetracycline, 7-chloro-6-desmethyltetracycline [demethylchlorotetra- cycline], 5-hydroxytetracycline [oxytetracycline] and 6-desoxy-5-hydroxytetracycline [doxycycline] - were reacted with different amounts of sodium nitrite at 37 °C for two hours in aqueous buffer solutions at pH 2 and 4. Dimethylnitrosamine formation was confirmed by gas-liquid chromatography and by combined gas-liquid chromatography/mass-spectrometry from minocycline, doxycycline, oxytetracycline and an- hydrochlorotetracycline. Dimethylnitrosamine formation from minocycline and doxycycline was blocked by ascorbic acid. The catalytic effect of sodium thiocyanate for the dimethylnitrosamine formation from minocycline and nitrite was investigated. The different reactivity of the investigated tetracycline derivatives towards nitrite in acidic solutions is discussed by stereochemical considerations in connection with the formation of hydrogen bridge linkages. This hypothesis was confirmed by dimethylnitrosamine formation from anhydro-chlorotetracycline and sodium nitrite at pH 2.

Substituted p-benzoquinones (= quinones) and substituted hydroquinones [bis-trimethylsilyl- ethers or bis-trifluoroacetates] can be separated by gas-liquid chromatography using 50 meter long thinfilm capillaries (inner diameter: 0.25 mm) coated with silicone OV 17 (50% phenyl, methyl) or silicone DC 550 (25% phenyl, methyl). Total retention times of various derivatives of p-benzoquinone and hydroquinone were deter­mined. Complex model mixtures of these derivatives can be separated by gas-liquid chromatography with temperature programs and the individual components can be clearly identified by their mass spectra in the sub microgram range by using combined gas-liquid chromatography/mass-spectrometry. This microanalytical technique was applied to identify the defensive secretion components from members of the diplopod order Julida (Arthropods). Julus nitidus produces a defensive secretion that consists exclusively of 2-methyl-3-methoxyquinone. The expelled defensive secretions of Unciger foetidus, Cylindroiulus coeruleocinctus (Iondinensis), Cylindroiulus punctatus, Cylindroiulus luridus and Ophyiulus psilosus consist of a 2-methylquinone and 2-methyl-3-methoxyquinone mixture. The presence of the corresponding hydroquinones-2-methyl-hydroquinone and 2-methyl-3-methoxyhydroquinone-was also determined in all cases.

The defensive secretion of Peripatopsis moseleyi (Onychophora) consists of 84% water and 16% protein and free amino acids. The secretion’s defensive effectiveness is an anti-predator “sticking” action. The secretion is flung out of the oral papillae in liquid state. It is then denaturized by the air and develops increasingly sticky white threads, probably through the devel­opment of disulfide bridges from the protein content. The elastic properties of the secretion threads indicate a micellar structure. The defensive secretion contains no volatile organic components or carbohydrates. This was confirmed by gas- liquid chromatography and thin-layer chromatography. After acidic hydrolysis of the secretion the following amino acids were determined quantita­tively: aspartic acid, threonine, serine, proline, glutamic acid, glycine, alanine, valine, cysteine, methionine, isoleucine, leucine, tyrosine, phenylalanine, lysine, histidine and arginine. A “rare” amino acid was not identified. Tryptophane was not present (basic secretion hydrolysis). The quantita­tive determination of free amino acids, based on the total content, showed the following results: glycine (40.9%), glutamic acid (10.8%), aspartic acid (2.65%), lysine (1.3%). This result shows, that the secretion is stored in a watery glycine/glutaminic acid buffer in the oral papillae of Peripatopsis moseleyi. High voltage paper electrophoreses and gel filtration experiments with dextran and agarose gels showed, that the secretion protein consists of, at least, two fractions with different molecular weight.