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A method was developed to determine 20 illegal residual -agonists in pork tissues, including muscle and liver simultaneously. The samples were hydrolyzed by -glucuronidase, purified by PCX SPE cartridges, and detected by HPLC coupled with electrospray ionization MS/MS operating in the positive ion mode. Matrix-fortified calibration was performed to compensate for the matrix effect and loss in sample preparation. Decision limit ranged from 0.05 to 0.23 g/kg in muscle and 0.05 to 0.57 g/kg in liver. Decision capacity ranged from 0.11 to 0.4 g/kg in muscle and 0.16 to 0.79 g/kg in liver. In Food Analysis Performance Assessment Scheme proficiency test 0287, a pig liver test material containing 13 -agonists was analyzed using the method developed, and clenbuterol and ractopaime were confirmed as being present. Z-scores for clenbuterol and ractopaime were 0.2 and 0.6, respectively.

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We theoretically investigate the single-photon transport properties in an optical waveguide embedded with a V-type three-level atom (VTLA) based on symmetric and asymmetric couplings between the photon and the VTLA. Our numerical results show that the transmission spectrum of the incident photon can be well controlled by virtue of both symmetric and asymmetric coupling interactions. A multifrequency photon attenuator is realized by controlling the asymmetric coupling interactions. Furthermore, the influences of dissipation of the VTLA for the realistic physical system on single-photon transport properties are also analyzed.