RESUMEN
An ultra-high performance liquid chromatography-mass spectrometry ( UPLC-MS/MS) method was developed for the determination of 8 kinds of cephalosporins, cefoperazone, cefquinome, cefalonium, cefazolin, cefapirin, Ceftiofur, cefpirome and cefalexin, in edible parts of aquatic products. The samples were extracted with acetonitrile-water and cleaned up by multi-walled carbon nanotubes ( MwCNTs) SPE cartridge. All the target compounds were separated on an Acquity Xselect CSH C18 column with gradient elution by using acetonitrile and 0. 1% formic acid aqueous as eluent, and detected by UPLC-MS/MS under ESI+ ionization and MRM mode. Under optimized conditions, this method had a good linearity (R2≥0. 995) and the limits of quantification were in the range of 2-10 μg/kg ( S/N=10 ) . The recoveries of the method for the target compounds spiked at three different levels were 67. 3%-94. 2% with the relative standard deviations (RSDs) of 3. 3%-14%. The method had the characteristics of low cost, high accuracy and good precision, and could meet the requirements of cephalosporins determination.
RESUMEN
Exopolysaccharide La0.1-1 was extracted from the broth of a marine bacterium Lentibacter algarum ZXM100T isolated from the seawater in the coastal region of Qingdao and purified by Q Sepharose Fast Flow ion-exchange chromatography and Superdex 75 gel-permeation chromatography. Its physiochemical properties and primary structural characters were investigated by chemical analysis together with high performance liquid chromatography (HPLC), high performance gel permeation chromatography (HPGPC) and gas chromatography and mass spectrometry (GC-MS). The results show that the total sugar content of the exoploysaccharide La0.1-1 was about 66% with an average molecular weight at 12.0 kDa. La0.1-1 is mainly composed of Gal, Man, GlcN at the ratio of 1.35:1.1:1.0. Results of GC-MS and NMR demonstrate that the exopolysaccharide La0.1-1 mainly exists with the beta configuration. The primary linkage styles are --> 2)-Manp(1 --> and --> 3)-Galp(1 --> with a small amount of --> 4)-Galp(--> 1 and --> 4)-Manp(1 --> linkages. The linkage mode of GlcN is --> 4)GlcN(1 --> and terminal linkage. The exopolysaccharide has mainly a linear sructure with a few branches linked to 0-6 of --> 2)-Manp(1 --> and 0-4 or 0-6 of --> 3)-Galp(1 -->. 1D-NMR data also revealed that La0.1-1 is substituted by certain acetyl; the acetyl is mainly linked to N-2 of GlcN. The exopolysaccharides of the bacterium of Lentibacter genus is reported for the first time, and an exopolysaccharide with novel structure was obtained, which enriched marine polysaccharide resources.