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Recently, 9,10-anthraquinone (AQ) contamination in Chinese Liupao tea has attracted much attention because the tea for export must meet the EU limit (10 µg kg−1). In this study, a method was developed in which the sample was extracted with n-hexane-acetone solution, then purified with Florisil adsorbent, detected by GC-MS/MS and contamination levels of AQ determined using an internal standard. This method was found to be more suitable for Liupao tea and other dark tea complex substrates than the QuEChERS procedure. The sample pre-treatment method was optimized with respect to extraction reagent and clean-up column adsorbent and n-hexane-acetone selected as the optimal extraction solvent. When the content of Florisil in the column was 1.0 g, the optimum clean-up was achieved. The new method reduced the limit of quantification (LOQ) of AQ to 10 μg kg−1, and accuracy was also further improved. The recovery of AQ-fortified tea samples containing 20–100 µg·kg−1 was 94.5–100.4%, and the relative standard deviation (RSD) was less than 1.3%. In a small survey, 98 Liupao tea samples on the market were tested by the new method. It was found that 61 samples were positive (occurrence rate 63.3%), and thus exceeded the EU limit (10 µg kg−1). This study also found that the contamination of AQ in Liupao tea increased with the length of ageing. The source of AQ in the Liupao tea ageing process will be the focus of further research. [ABSTRACT FROM AUTHOR]

The photoresponsive J-aggregation behaviors of a novel azobenzene-substituted zinc phthalocyanine (azo-ZnPc dyad) were studied by UV/vis, fluorescence, and (1)H NMR spectroscopy. Upon illumination with 365 nm UV light, the trans-cis isomerization of azobenzene can efficiently reduce the steric hindrance around the peripheral oxygen atom of azo-ZnPc, shortening the possible distance between two phthalocyanine molecules and, consequently, greatly improving the tendency of J-aggregation of azo-ZnPc dyad. The third-order optical nonlinearities of the photoresponsive J-aggregates (before and after illumination) were measured by a Z-scan technique at 532 nm with a pulse duration of 25 ps. The Z-scan spectra revealed that all the samples possessed large positive nonlinear refraction and positive nonlinear absorption, exhibiting a self-focusing effect and reverse saturable absorption, respectively. The second molecular hyperpolarizabilities of the dyad in two conditions were measured to be 3.87 x 10(-30) and 4.82 x 10(-30) esu, respectively. All the results suggest that the azo-ZnPc dyad has potential in the field of nonlinear optics applications.

The title compound, C(22)H(22)N(2)O(10), was prepared by the glycosidation method through nitrite displacement on substituted nitro-phthalonitrile. The mol-ecule contains a benzene ring, two nitrile groups and an acetyl-protected d-glucose fragment which adopts a chair conformation. The absolute configuration was determined by the use of d-glucose as starting material. All substituents of the protected sugar are in equatorial positions, with the exclusive presence of the α-anomer. The crystal packing is stabilized by C-H⋯O and C-H⋯N hydrogen-bonding inter-actions.