[Determination of diflubenzuron and triflumuron residues in greasy wool by accelerated solvent extraction technique and high performance liquid chromatography].

A method for the determination of diflubenzuron and triflumuron residues in greasy wool was developed by high performance liquid chromatography (HPLC) coupled with accelerated solvent extraction (ASE). The diflubenzuron and triflumuron residues were extracted with acetonitrile saturated with n-hexane at 80 degrees C and 10.34 MPa. The extract was pretreated by a series of procedures such as freezing-lipid filtration, concentration and purification by solid-phase extraction prior to the determination with HPLC. The target analytes were separated on a Waters Atlants dC18 column (250 mm x 4.6 mm, 5 microm), gradiently eluted with acetonitrile and water as the mobile phases and detected by a photodiode array detector (DAD) at 254 nm. The linear ranges were 0.1 - 10.0 mg/L. There were good linearity between the peak areas and concentrations in the linear range for the analytes, and the correlation coefficients of diflubenzuron and triflumuron were higher than 0.9999. The limits of quantification for diflubenzuron and triflumuron were 0.05 and 0.04 mg/kg (S/N > or = 10), respectively. The method is simple, rapid, sensitive and suitable for preliminary screening of diflubenzuron and triflumuron residues in greasy wool.

[Molecular epidemiology of Listeria monocytogenes isolates from imported fishery products to China].

OBJECTIVE: We examined the prevalence, molecular characteristics and virulence potential of Listeria monocytogenes isolates from imported fishery products to gain further insights on the public health risk caused by this important food borne pathogen. METHODS: L. monocytogenes isolates, screened from 1275 batches of fishery products imported from July 2007 to November 2008, were studied by lineage classification, serotyping, in vivo virulence assessment in ICR mouse model and multilocus sequence typing (MLST). RESULTS: Thirty-three batches were contaminated by L. monocytogenes (33/1275, 2.6%), in which serovar 4b dominated (65.2%), followed by serovars 1/2b (17.4%), 1/2a (13.0%) and 1/2c (4.4%). These isolates were all as virulent as L. monocytogenes reference strains. Of 23 selected L. monocytogenes isolates and 9 reference strains, 23 sequence types (STs) were recognized with discrimination index (D.I.) of 0.97, based on the concatenated gene cluster covering one virulent gene actA, two housekeeping genes hisJ and ribC, and one stress-response gene sigB. Remarkably, 3 isolates from American salmon, Argentina squid and Peru squid respectively belonged to ST9 which represented epidemic clone I (ECI). The isolation rate of L. monocytogenes in imported fishery products (2.6%) was similar to that in domestic fishery products (2.7%). Serovar 4b, which was more virulent than other serovars in humans, was dominant in imported fishery products, and even ECI was recognized. CONCLUSION: All of these isolates were as virulent as L. monocytogenes reference strains, suggesting inspection and quarantine strategies of imported fishery products should be strengthened effectively.

[Determination of 28 organochlorine and synthetic pyrethroid pesticides in greasy wool using accelerated solvent extraction technique and gas chromatography].

A method for the simultaneous determination of 28 organochlorine and synthetic pyrethroid pesticides in greasy wool was developed by accelerated solvent extraction (ASE) coupled with gas chromatography-electron capture detection (GC-ECD). The organochlorine and synthetic pyrethroid pesticides in greasy wool were extracted with acetonitrile saturated with n-hexane at 80 degrees C, 10.34 MPa by ASE. The extract was pretreated by a series of procedures such as freezing-lipid filtration, concentration and purification by solid-phase extraction prior to the determination with GC-ECD. The linear ranges were 0.005-1.0 mg/L for 16 organochlorines, 0.02-4.0 mg/L for flumethrin and 0.01-2.0 mg/L for the others. There were good linear relationships between the peak area and concentration in the linear ranges. The average recoveries of 28 organochlorine and synthetic pyrethroid pesticides were 67.2%-107.7%, and the relative standard deviations were 2.6%-29.0%. The method is simple, sensitive and suitable for preliminary screening of organochlorine and synthetic pyrethroid pesticides in greasy wool.