RESUMEN
Objective: To establish a method using gas chromatography for the determination of the residual chloroform in the medical polylactic acid membrane. Methods: The direct aqueous injection gas chromatographic method was established for the determination using RESTEK RTX capillary-column chromatography with the electron capture detector(ECD) at 270 ℃ and with the column at 85 ℃,maintained for 3 min. The split ratio of sampling was 10∶1. The injector temperature was 200 ℃. The high purity nitrogen was used as the carrier gas with the flow of 1. 0 ml /min. The injection volume was 1 μl. Results: The calibration curve showed a good linearity within the range of 25-2 000 ng /ml (r = 0. 999 9). The limit of detection was 1. 50 ng /ml,and the limit of quantitation was 4. 62 ng /ml. The average recovery rate was 98. 35％,RSD = 1. 98％. Conclusion: Gas chromatography is sensitive and accurate for the determination of the residual chloroform in the medical polylactic acid membrane.
RESUMEN
Between 2006 and 2009, seven strains of infectious bronchitis (IB) virus (IBV) were isolated from vaccinated chicken flocks on different chicken farms in China. The pathogenic characters of seven IBV strains were assessed. Each of the seven strains was infective to the test chickens and could induce an immune response. The results from chicken embryo cross-neutralization assays showed that these strains were antigenically distinct from classic IBV strains of H120, M41, Conn, and Gray. Compared to H120 vaccine strain, point mutation, short insertion, and deletion occurred at many positions in the S1 protein of the seven strains. Five of the seven strains had the motif (HRRRR), which was identical to that of the epidemic IBV strains in China. Two new motifs (HRLRR and RRIRR) emerged in the isolated strains. The homology of the nucleotide and amino acid sequences of the S1 gene among the seven isolates was 81.7%-99.7% and 79.0%-99.4%, respectively. These seven strains were also genetically different from the vaccine strains and non-China IBV strains but closely related to large numbers of Chinese strains. The seven isolates and 36 reference IBV strains were clustered into six distinct groups (I-VI). The seven strains were categorized into groups I, II, and III, forming a big phylogenetic branch, which is closely related to Chinese IBVs, whereas the vaccine strains belonging to group VI are genetically distant from groups I, II, and III. The results from this study indicate that different IBV strains cocirculate in the chicken population in China.