Biomedical subjects

Kang Dai

Publications and source records attributed to Kang Dai.

9 recordsLinked to original sources

PubMed2006

Selective solid-phase extraction of tebuconazole in biological and environmental samples using molecularly imprinted polymers.

Molecularly imprinted polymers (MIPs) were prepared by precipitation polymerization using tebuconazole (TBZ) as a template. Frontal chromatography and selectivity experiments were used to determine the binding capabilities and binding specificities of different MIPs. The polymer that had the highest binding selectivity and capability was used as the solid-phase extraction (SPE) sorbent for the direct extraction of TBZ from different biological and environmental samples (cabbage, pannage, shrimp, orange juice and tap water). The extraction protocol was optimized and the optimum conditions were: conditioning with 5 mL methanol:acetic acid (9:1), 5 mL methanol and 5 mL water respectively, loading with 5 mL aqueous samples, washing with 1.2 mL acetonitrile (ACN):phosphate buffer (5:5, pH3), and eluting with 3 mL methanol. The MIPs were able to selectively recognize, effectively trap and preconcentrate TBZ over a concentration range of 0.5-15 micromol/L. The intraday and interday RSDs were less than 9.7% and 8.6%, respectively. The limit of quantification was 0.1 micromol/L. Under optimum conditions, the MISPE recoveries of spiked cabbage, pannage, shrimp, orange juice and tap water were 62.3%, 75.8%, 71.6%, 89% and 93.9%, respectively. MISPE gave better HPLC separation efficiencies and higher recoveries than C18 SPE and strong cation exchange (SCX) SPE.

Acetic Acid↗

PubMed2006

Selective solid-phase extraction of cholesterol using molecularly imprinted polymers and its application in different biological samples.

Non-covalent molecularly imprinted polymers (MIPs) of cholesterol were prepared by UV initiated polymerization. A polymer that had the highest binding selectivity and capability was used as solid-phase extraction (SPE) sorbents for direct extraction of cholesterol from different biological samples (human serum, cow milk, yolk, shrimp, pork and beef). The extraction conditions of molecularly imprinted SPE (MISPE) were optimized and the optimum protocol was: conditioning MISPE cartridges with n-hexane, loading with n-hexane, washing with n-hexane and n-hexane:toluene=9:1, respectively, then eluting with chloroform:ethanol:acetic acid=3:1:1. Cholesterol MISPE selectively recognized, effectively trapped and pre-concentrated cholesterol over a concentration range of 10-80 microg/mL. Recoveries ranged from 80.6% to 92.7%, with R.S.D. lower than 9.8%. Under the optimal condition, MISPE recoveries of spiked human serum, yolk, cow milk, shrimp, pork and beef were 91.1%, 80.4%, 86.6%, 78.2%, 81.4% and 80.1%, respectively. Compared with C18 SPE, almost all of the matrix interferences were removed after MISPE, and better baselines and higher selectivity were achieved.

Animals↗

PubMed2006

Selective solid-phase extraction of bisphenol A using molecularly imprinted polymers and its application to biological and environmental samples.

Molecularly imprinted polymers (MIPs) were prepared using bisphenol A (BPA) as a template by precipitation polymerization. The polymer that had the highest binding selectivity and ability was used as solid-phase extraction (SPE) sorbents for direct extraction of BPA from different biological and environmental samples (human serum, pig urine, tap water and shrimp). The extraction protocol was optimized and the optimum conditions were as follows: conditioning with 5 mL methanol-acetic acid (3:1), 5 mL methanol, 5 mL acetonitrile and 5 mL water, respectively, loading with 5 mL aqueous samples, washing with 1 mL acetonitrile, and eluting with 3 mL methanol. MIPs can selectively recognize, effectively trap and preconcentrate BPA over a concentration range of 2-20 microM. Recoveries ranged from 94.03 to 105.3%, with a relative standard deviation lower than 7.9%. Under the optimal condition, molecularly imprinted SPE recoveries of spiked human serum, pig urine, tap water and shrimp were 65.80, 82.32, 76.00 and 75.97%, respectively, when aqueous samples were applied directly. Compared with C18 SPE, a better baseline, better high-performance liquid chromatography separation efficiency and higher recoveries were achieved after molecularly imprinted SPE.

Animals↗

PubMed2006

Direct enrichment and high performance liquid chromatography analysis of ultra-trace Bisphenol A in water samples with narrowly dispersible Bisphenol A imprinted polymeric microspheres column.

Direct injection, enrichment and high performance liquid chromatography (HPLC) analysis of ultra-trace Bisphenol A (BPA) in water samples using one narrowly dispersible BPA imprinted polymeric microspheres (MIPM) column in one analysis process was developed. One BPA imprinted MIPM that had the best globular morphology and imprinted efficiency was used as HPLC stationary phase and applied to direct analysis of ultra-trace BPA in water. The optimum direct analysis conditions were: conditioning the MIPM column with water for 10min, injecting 40mL water sample directly, eluting with 70% methanol for 13min and then 100% methanol for 7min. Under the optimum conditions, the MIPM column can simultaneously extract, enrich, separate and determine ultra-trace BPA in one analysis process with UV detector by injection of large volume water samples (40mL). The calibration graph was linear with R(2)>0.998 in the ranges from 0.1-100nmol/L BPA standard solution. The intra- and inter-day RSD are less than 9.5 and 9.6%, respectively. The limit of quantification was 0.1nmol/L. RSD for spiked tap and lake water was less than 8.9% and the recoveries were 96-101.8%. The enrichment factor for BPA was 10,000 as 40mL water sample was directly injected and analyzed.

Benzhydryl Compounds↗

PubMed2006

[Energy-pooling collisions of rubidium atoms: Rb (5P(J)) + Rb (5P(J))--> Rb (5S) + Rb (nl = 5D,7S)].

An experimental study of rubidium energy pooling collisions, Rb(5P(J)) + Rb(5P(J))-->Rb(nlJ') + Rb(5S), at thermal energies, was carried out in a cell. Atoms were excited to either the 5P 1/2 or 5P 3/2 state using a single-mode diode laser. The excited atom density and spatial distribution were mapped by monitoring the absorption of a counter-propagating single-mode diode laser beam, tuned to either 5P 1/2-->5D 3/2 or 5P 3/2-->7S 1/2 transition, which could be translated parallel to the pump beam. The excited atom densities were combined with the measured fluorescence ratios to determine cross sections for the rubidium energy pooling process. For 5P 3/2 excitation the cross sections for nlJ' being 5D 5/2, 5D 3/2, and 7S 1/2 are (1.32+/-0.59) x 10(-14), (1.18+/-0.53) x 10(-14) and (3. 21+/-1. 44) x 10(-15) cm2, respectively. For 5P 1/2 excitation the cross sections for nlJ' being 5D 5/2 and 5D 3/2 are (6.57+/-2.96) x 10(-15), and (5.90+/-2.66) x 10(-15) cm2, respectively. The results were compared with those of other experiments.

English Abstract↗

PubMed2006

[Fluorescence spectrum of cesium vapor resonantly excited by the 852.3 nm laser line].

The fluorescence spectrum of cesium vapor was studied in a cell irradiated with the light of 852.3 nm resonance line from a single mode laser diode. From the intensities and spectra of the Cs and Cs2 fluorescence we identified several collisional and radiative processes in the excited cesium atom-dimer system. The atomic lines of the highly excited states were the result of collisional energy transfer from Cs(6P 3/2) + Cs(6P 3/2) to Cs(6D, 8S) atoms. The Cs2 (B 1 IIu) band formed in Cs (6P) + Cs2 (X1sigmag+) collisions. The fine-structure mixing in 6 2P atoms was studied through excitation transfer, energy-pooling collision, and collisional excitation transfer between Cs2 and Cs. The authors estimated the value of rate coefficient for the collisional energy transfer from 6P3/2 to 6P1/2 to be (5.2+/-2.1) x 10(-11) cm3 x s(-1). For the excitation transfer process Cs2 (B 1 IIu)+ Cs(6S)--> Cs2 (X 1sigmag+) + Cs(6P1/2 ), a rate coefficient of (1.0+/-0.4) x 10(-9) cm3 x s(-1) was yielded.

Algorithms↗

PubMed2005

[Collisional excitation transfer between Na2(B 1pi(u)) and Na2(2 1sigma(g)+)].

The B 1pi(u) electronic state of Na2 was excited by the 441.6 nm He-Cd laser line. The Na atomic transitions and the A 1sigma(u)+ --> X 1sigma(g)+ band of Na2 were recorded. From the intensities and spectra of the Na and Na2 fluorescence several collisional processes in the excited sodium atom-dimer system were identified. The Na atomic lines are the result of collisional energy transfer from Na2 (B 1pi(u)) to Na(3P). Predissociation process may also contribute to atomic fluorescence. The A 1sigma(u)+ --> X 1sigma(g)+ band is interpreted through a populating mechanism involving collisional transfer from B 1pi(u) to 2 1sigma(g)+ followed by a radiative transfer to the A 1sigma(u)+ state. From the decay constants and fluorescence intensities, the rate coefficient at 360 degrees C for collisional energy transfer from Na2 (B 1pi(u)) to Na2 (2 1sigma(g)+) was found to be 5.7 x 10(-10) cm3 x s(-1). The predissociation rate of the B 1pi(u) is 2.7 x 10(6) s(-1).

Algorithms↗

PubMed2005

[Energy pooling collisions for K(4P) + Cs(5D) in a K-Cs mixture].

The rate coefficients for energy-pooling collisions K(4P) + Cs(5D) --> Cs(6S) + K(4D, 6S) in the K-Cs vapor mixture were measured relative to a known energy-pooling rate coefficient of a homonuclear reaction [i. e., Cs(6P) + Cs(5D) --> Cs(6S) + Cs (7D(J))]. Populations of the Cs(6P, 5D) and K(4P) states were produced by photodissociation of K2 and Cs2 molecules through the use of a dye laser radiation. The resulting fluorescence included the direct components emitted in the decay of the excited states produced by photodissociation and the induced components arising from the collisionally populated states. By combining relative intensities of the components with the effective lifetimes of Cs(6P) and K(4P) states, the rate coefficients (in units of 10(-9) cm3 x s(-1)) for the heteronuclear energy-pooling were found to be 2.6 and 3.6, respectively. The contribution to the rate coefficients from other processes are discussed.

English Abstract↗

PubMed2004

[Photolytic spectroscopy of Cs2 molecules].

Populations of the n2 L (nL = 7P, 6D) states of Cs atoms by photodissociation of Cs2 molecules through the use of the fixed frequence line 441.6 nm of a He-Cd laser radiation are produced. Combining ratios of atomic to molecular fluorescence at the Cs density range between 1 and 9 x 10(15) cm(-3), the ratios of collisional rate coefficient to predissociation rates are estimated to be 2.9 x 10(-17) cm3 and 7.4 x 10(-18) cm3, respectively. The branching ratios are defined as the ratios of nL(J) to nL(J) fluorescence. The ratios of the dissociation rates produced in n2 L fine-structure states are 0.53 and 0.43, respectively. Fine-structure changing cross section has been measured for far wing excitation, the result is consistent with cross section obtained from other excitation of the n2 L states. The cross section for excitation transfer out of the 6D doublet [i.e., Cs(6D) + Cs(6S) --> states other than Cs(6D)] is 1.9 x 10(-14) cm2.

Cesium↗