The applicability of hollow fiber liquid-phase microextraction (HF-LPME) combined with high-performance liquid chromatography-ultraviolet detection (HPLC-UV) was evaluated for the extraction and determination of tamox...The applicability of hollow fiber liquid-phase microextraction (HF-LPME) combined with high-performance liquid chromatography-ultraviolet detection (HPLC-UV) was evaluated for the extraction and determination of tamoxifen (TAM) in biological fluids including human urine and plasma. The drug was extracted from a 15 mL aqueous sample (source phase;SP) into an organic phase impregnated in the pores of the hollow fiber (membrane phase;MP) followed by the back-extraction into a second aqueous solution (receiving phase;RP) located in the lumen of the hollow fiber. The effects of several factors such as the nature of organic solvent, compositions of SP and RP solutions, extraction time, ionic strength and stirring rate on the extraction efficiency were examined and optimized. An enrichment factor of 360 along with substantial sample clean up was obtained under the optimized conditions. The calibration curve showed linearity in the range of 1 - 500 ng?mL–1 and the limit of detection was found to be 0.5 ng?mL–1 in aqueous medium. A reasonable relative recovery (≥89%) and satisfactory intra-assay (3.7% - 4.2%, n = 3) and inter-assay (7.5% - 7.8%, n = 3) precision illustrated good performance of the analytical procedure in spiked human urine and plasma samples.展开更多
Amantadine （AMA） is an anti-viral drug used in apiculture to protect honeybee against the sacbrood virus （Morator aetatulae）. This study described a reliable high-performance liquid chromatographic （HPLC） method...Amantadine （AMA） is an anti-viral drug used in apiculture to protect honeybee against the sacbrood virus （Morator aetatulae）. This study described a reliable high-performance liquid chromatographic （HPLC） method for analyzing AMA in honey using a solid-phase extraction （SPE） cartridge （Plexa PCX） for purification, 4-fluoro-7- nitro-2,1,3-benzoxadiazole （NBD-F） as a pre-column derivatization agent, and fluorometric detection （λex =470 nm, λem=530 nm）. The chromatographic separation was performed on an XDB C18 column （150×4.6 mm i.d.） using 0.1% trifluoroacetic acid/acetonitrile （35 ; 65, V/V） as the mobile phase at a flow rate of 1.0 mLomin 1 with a run time of 20 min. Under these optimal conditions, a linear relationship was observed in the range of 0.025--1.0μg·mL-1 with a good correlation coefficient （0.998） and low limit of detection （0.0080 μg·g-1）, the recoveries were all above 90%, and the intra-day and inter-day precision （RSD） ranged from 3.4%--5.1%.展开更多
A portable analog lock-in amplifier capable of accurate phase detection is proposed in this paper. The proposed lock-in amplifier, which uses the dual-channel orthometric signals as the references to build the xy coor...A portable analog lock-in amplifier capable of accurate phase detection is proposed in this paper. The proposed lock-in amplifier, which uses the dual-channel orthometric signals as the references to build the xy coordinate system, can detect the relative phase between the input and x-axis based on trigonometric function. The sensitivity of the phase measurement reaches 0.014degree, and a detection precision of 0.1 degree is achieved. At the same time, the performance of the lock-in amplifier is verified in the high precision optical oxygen concentration detection. Experimental results reveal that the portable analog lock-in amplifier is accurate for phase detection applications. In the oxygen sensing experiments, 0.058% oxygen concentration resulted in 0.1 degree phase shift detected by the lock-in amplifier precisely. In addition, the lock-in amplifier is small and economical compared with the commercial lock-in equipments, so it can be easily integrated in many portable devices for industrial applications.展开更多
文摘The applicability of hollow fiber liquid-phase microextraction (HF-LPME) combined with high-performance liquid chromatography-ultraviolet detection (HPLC-UV) was evaluated for the extraction and determination of tamoxifen (TAM) in biological fluids including human urine and plasma. The drug was extracted from a 15 mL aqueous sample (source phase;SP) into an organic phase impregnated in the pores of the hollow fiber (membrane phase;MP) followed by the back-extraction into a second aqueous solution (receiving phase;RP) located in the lumen of the hollow fiber. The effects of several factors such as the nature of organic solvent, compositions of SP and RP solutions, extraction time, ionic strength and stirring rate on the extraction efficiency were examined and optimized. An enrichment factor of 360 along with substantial sample clean up was obtained under the optimized conditions. The calibration curve showed linearity in the range of 1 - 500 ng?mL–1 and the limit of detection was found to be 0.5 ng?mL–1 in aqueous medium. A reasonable relative recovery (≥89%) and satisfactory intra-assay (3.7% - 4.2%, n = 3) and inter-assay (7.5% - 7.8%, n = 3) precision illustrated good performance of the analytical procedure in spiked human urine and plasma samples.
文摘Amantadine （AMA） is an anti-viral drug used in apiculture to protect honeybee against the sacbrood virus （Morator aetatulae）. This study described a reliable high-performance liquid chromatographic （HPLC） method for analyzing AMA in honey using a solid-phase extraction （SPE） cartridge （Plexa PCX） for purification, 4-fluoro-7- nitro-2,1,3-benzoxadiazole （NBD-F） as a pre-column derivatization agent, and fluorometric detection （λex =470 nm, λem=530 nm）. The chromatographic separation was performed on an XDB C18 column （150×4.6 mm i.d.） using 0.1% trifluoroacetic acid/acetonitrile （35 ; 65, V/V） as the mobile phase at a flow rate of 1.0 mLomin 1 with a run time of 20 min. Under these optimal conditions, a linear relationship was observed in the range of 0.025--1.0μg·mL-1 with a good correlation coefficient （0.998） and low limit of detection （0.0080 μg·g-1）, the recoveries were all above 90%, and the intra-day and inter-day precision （RSD） ranged from 3.4%--5.1%.
文摘A portable analog lock-in amplifier capable of accurate phase detection is proposed in this paper. The proposed lock-in amplifier, which uses the dual-channel orthometric signals as the references to build the xy coordinate system, can detect the relative phase between the input and x-axis based on trigonometric function. The sensitivity of the phase measurement reaches 0.014degree, and a detection precision of 0.1 degree is achieved. At the same time, the performance of the lock-in amplifier is verified in the high precision optical oxygen concentration detection. Experimental results reveal that the portable analog lock-in amplifier is accurate for phase detection applications. In the oxygen sensing experiments, 0.058% oxygen concentration resulted in 0.1 degree phase shift detected by the lock-in amplifier precisely. In addition, the lock-in amplifier is small and economical compared with the commercial lock-in equipments, so it can be easily integrated in many portable devices for industrial applications.
