Biomedical subjects

Qingxiang Zhou

Publications and source records attributed to Qingxiang Zhou.

9 recordsLinked to original sources

PubMed2006

Improved single-drop microextraction for high sensitive analysis.

This paper described a simple approach to prepare a small bell-mouthed extraction device for single-drop microextraction (SDME). Analytical sensitivity was improved by increasing the suspended acceptor volume. Because of the increased contact area and the rough inner surface of the extraction device, the stability of drop was markedly increased. The merits of the proposed method were demonstrated by using 1-octanol as extractant and with cyanazine, simazine and atrazine as model compounds. The related parameters and the effect of humic acid were systematically investigated. Under the optimized extraction conditions, the linear range, detection limit (S/N=3) and precision (RSD, n=6) were 0.2-50, 0.06microgL-1, 5.7% for cyanazine, 0.1-25, 0.03microgL-1, 6.7% for simazine, and 0.15-37.5, 0.04microgL-1, 5.0% for atrazine, respectively. The established method was applied to determine the target compounds in four real water samples, and the satisfactory spiked recoveries at two concentration levels were obtained. Moreover, the comparison of the proposed SDME with the traditional SDME was performed. These results indicated that the proposed improvement made SDME be a competitive analytical tool and an alternative of the traditional methods for the analysis of organic pollutants at trace level.

Analytic Sample Preparation Methods↗

PubMed2006

Sensitive determination of thiamethoxam, imidacloprid and acetamiprid in environmental water samples with solid-phase extraction packed with multiwalled carbon nanotubes prior to high-performance liquid chromatography.

This paper describes a novel method for sensitive determination of thiamethoxam, imidacloprid and acetamiprid based on solid-phase extraction with multiwalled carbon nanotubes as the packed materials. Factors that maybe influence the enrichment efficiency, such as sample flow rate, sample pH, and sample volume, were investigated in detail. Under the optimized conditions, the detection limits of thiamethoxam, imidacloprid and acetamiprid were 6.1, 5.4 and 6.7 ng L(-1), respectively. The experimental results indicated that there was good linearity (R2>0.9993) over the range of 0.08 approximately 100 ng mL(-1) and good reproducibility with the relative standard deviations over the range of 0.7 approximately 1.1% (n=6). The proposed method has been applied to the analysis of real-world water samples, and satisfactory achievements were obtained. The average spiked recoveries were in the range of 87.5 approximately 109.8%. All the results indicated that the proposed method could be used for the simultaneous determination of the three pesticides in environmental water samples at trace levels.

Chromatography, High Pressure Liquid↗

PubMed2006

Using multi-walled carbon nanotubes as solid phase extraction adsorbents to determine dichlorodiphenyltrichloroethane and its metabolites at trace level in water samples by high performance liquid chromatography with UV detection.

Carbon nanotubes (CNTs) are a kind of new carbon-based nano-materials which have drawn great attention in many application fields. The potential of multi-walled carbon nanotubes (MWNTs) as solid-phase extraction (SPE) adsorbents for the preconcentration of environmental pollutants has been investigated in recent years. The goal of this work was to investigate the feasibility of MWNTs used as SPE adsorbents to enrich dichlorodiphenyltrichloroethane (DDT) and its metabolites including 1,1-dichloro-2,2-bis-(4'-chlorophenyl)ethane (DDD) and 1,1-dichloro-2,2-bis-(4'-chlorophenyl)ethane (DDE) at trace level which are typical persistent organic pollutants in environment. Parameters that maybe influence the extraction efficiency such as the eluent volume, sample flow rate, sample pH and the sample volume were optimized in detail. The experimental results showed the excellent linear relationship between peak area and the concentration of DDT and its metabolites over the range of 0.2-60 microg L(-1), and the precisions (RSD) were 2.3-2.5% under the optimal conditions. The detection limits of proposed method could reach 4-13 ng L(-1) based on the ratio of chromatographic signal to base line noise (S/N = 3). Satisfied results were achieved when the proposed method was applied to determine the four target compounds in realworld water samples with spiked recoveries over the range of 89.7-115.5%. All these facts indicated that MWCNTs as SPE packing materials coupled to HPLC was an excellent alternative for the routine analysis of DDT and its metabolites at trace level in environment.

Adsorption↗

PubMed2005

Determination of 3-chloropropane-1,2-diol in liquid hydrolyzed vegetable proteins and soy sauce by solid-phase microextraction and gas chromatography/mass spectrometry.

Headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography/mass spectrometry (GC/MS) method was developed to determine 3-chloropropane-1,2-diol (3-MCPD) in hydrolyzed vegetable protein and Chinese soy sauce. The 3-MCPD was firstly derivativized with phenylboronic acid in aqueous solution at 90 degrees C for 10 min, then extracted by HS-SPME and finally detected with GC/MS, parameters related to both the derivative reaction and the HS-SPME process were optimized. The proposed method has a linear range of 0.0194-394 microg g(-1), a detection limit of 3.87 ng g(-1) (S/N = 3), and a precision of RSD = 7.5% (n = 5). Seventeen real samples, including four HVPs and thirteen soy sauce samples, were analyzed to examine the feasibility of the proposed procedure; with a concentration of 3-MCPD and acceptable recoveries at 0.71 microg g(-1) spiked levels were obtained. Being simpler, faster and more environmentally benign than the existing methods, this method is accurate and suitable for routine analysis.

Boronic Acids↗

PubMed2004

Calculation of the peak concentration of 2-chlorobenzamide generated in the hydrolysis of the benzoylphenylurea insecticide 1-(2-chlorobenzoyl)-3-(4-chlorophenyl)urea.

1-(2-chlorobenzoyl)-3-(4-chlorophenyl)urea (CCU), a new analogue of diflubenuron and PH-6038, has been widely used in agriculture and forestry as a molt-inhibiting hormone insecticide which was developed in China. 2-Chlorobenzamide, a main degradation product of CCU in the environment, has been identified as a potential carcinogen, so the content of 2-chlorobenzamide from the breakup of CCU will directly affect the environmental safety of CCU. In this paper we describe a simple, rapid, and convenient prediction model for predicting the level and time of occurrence of the peak concentration of 2-chlorobenzamide in the hydrolysis of CCU verified by experimental data. The time for reaching the peak concentration of 2-chlorobenzamide (tm) at 25 degrees C and pH 6 is 13.5 d, and the maximum concentration of 2-chlorobenzamide (ym) is 3.2% of the initial concentration of CCU according to the results from the prediction model. These results are similar to the real values from the experiments, which are 22 d and 1.6% of the initial concentration of CCU, respectively. The difference between the values of the prediction and experiment is discussed, and it is demonstrated that the predicting model is highly credible.

Benzamides↗

PubMed2004

Sensitivity enhancement of chlorinated phenols by continuous flow liquid membrane extraction followed by capillary electrophoresis.

This paper describes a new analytical system, based on the combination of continuous flow liquid membrane extraction (CFLME) enrichment and capillary electrophoresis (CE) separation, for analysis of chlorinated phenols in water samples. Five chlorinated phenols including 3-chlorophenol (3CP), 4-chlorophenol (4CP) 2,4-dichlorophenol (DCP), 2,4,6-trichlorophenol (TCP), and pentachlorophenol (PCP) were separated by CE with Tris/sodium dihydrogen phosphate solution containing methanol 1% (v/v) as the run buffer. CFLME related parameters were investigated and optimal enrichment was obtained by using 0.3 mol L(-1) Tris as acceptor and with a sample pH 5.0, a sample flow rate of 4.0 mL min(-1), and an enrichment sample volume of 150 mL. The detection limit (S/N= 3) was 6.9, 1.0, and 1.7 ng mL(-1) for DCP, PCP, and TCP, respectively. The reproducibility (RSD%, n = 6) was 5.7 for DCP, 2.5 for PCP, and 2.8% for TCP (n = 6). The proposed method was applied to the determination of chlorinated phenols in spiked water samples with relatively satisfactory recoveries.

Calibration↗

PubMed2004

A scaleless wings mutant associated with tracheal system developmental deficiency in wing discs in the silkworm, Bombyx mori.

A mutant of Bombyx mori has wings with few scales and is named scaleless. We investigated the morphology of this mutant and found that it had many fewer wing scales than the corresponding wild type (WT) silkworm and that the remaining scales were smaller in shape with fewer furcations. Reciprocal transplantation of wing discs between scaleless and WT revealed that the WT wing disc could develop into a small wing with scales after transplantation into a scaleless larva; however, the scaleless wing disc developed into a small wing without scales in a WT larva. Upon dissection of WT and scaleless wing discs at different stages from the fifth instar larva to adulthood, no obvious differences were found before pupation. However, after pupation, tracheae produced from WT wing veins extended to the lacunae between the veins and formed a network on the second day after pupation, whereas this did not happen in scaleless. At the same time, no marked difference in adult body tracheal development was found between the mutant and wild type. Furthermore, if the surface of a wing disc was cut and its veins injured, the resulting wing also had fewer scales than the corresponding WT. Also, we found that higher partial pressure of O2 could rescue the loss of scales in scaleless. These data suggest that the factors affecting the growth of scales were not produced in the hemolymph, but in the wing disc itself. It is also implied that wing scale development is dependent on the correct organization of the tracheal system in the wing disc.

Animals↗

PubMed2004

Determination of glyphosate in water samples by alternating-current oscillopolarographic titration.

This paper describes a novel, simple and sensitive method for the determination of glyphosate in water samples by alternating-current oscillopolarographic titration. Under an acidic condition, glyphosate can be transferred into a nitrosocompound by reacting with NaNO2. The titration end-point was obtained by the formation of a sharp cut in the oscillopolarographic with infinitesimal NaNO2 on double platinum electrodes. The results showed that glyphosate had an excellent linear relationship over the range of 7.16 x 10(-6) - 4.14 x 10(-3) mol L(-1), the RSD of the proposed method was lower than 3%, and the spiked recoveries of three real water samples were in the range of 97.7 - 100.2%.

Glycine↗

PubMed2003

Multiwalled carbon nanotubes as a solid-phase extraction adsorbent for the determination of bisphenol A, 4-n-nonylphenol, and 4-tert-octylphenol.

The adsorptive potential of multiwalled carbon nanotubes (MWNTs) for solid-phase extraction of bisphenol A, 4-n-nonylphenol, and 4-tert-octylphenol was investigated for the first time. The three analytes are quantitatively adsorbed on a MWNTs-packed cartridge, then the analytes retained on the cartridge are quantitatively desorbed with suitable amounts of methanol. Finally, the analytes in the methanol eluate are determined by high performance liquid chromatography-fluorometric detection. Parameters influencing the extraction efficiency, such as volume of the sample solutions, pH of the sample, and the eluent volume, were examined. Comparative studies showed that MWNTs were superior to C18 for the extraction of the more polar analyte bisphenol A and at least as effective as C18 for the extraction of 4-n-nonylphenol and 4-tert-octylphenol. Compared to XAD-2 copolymer, MWNTs exhibited a better property for the extraction of all three analytes. The developed method has been applied to determine bisphenol A, 4-n-nonylphenol, and 4-tert-octylphenol in several environmental water samples. The accuracy of the proposed method was tested by recovery measurements on spiked samples, and good recovery results (89.8-104.2%) were obtained. Detection limits of 0.083, 0.024, and 0.018 ng mL(-1) for bisphenol A, 4-n-nonylphenol, and 4-tert-octylphenol, respectively, were achieved under the optimized conditions.

Adsorption↗