Papers by Keyword: Determination

Abstract: High performance capillary zone electrophoresis (HPCE) was used in this text to determine the content of ferulic acid in a ready-made Chinese herbal medicine called AI-FUNUAN-GONG (in pills). Electrophoretic separation conditions: Uncoated fused silica capillary column (75um×49/58cm), injection height 7.5cm, 30mmolL^-1 borax solution, separation voltage 20kV, injection time 10s, detection wavelength 315 nm, experimental temperature 20°C.Linearity was kept in the concentration ranging from 1~62.5 mg·L^-1 of ferulic acid with correlation coefficient of 0.970. The average recovery was 97.541% and RSD value was 6.57%. Sample content of ferulic acid was 0.0715mg/g. This method has the advantages of strong specificity, simpleness, speediness, accurate results and good repeatability in separation and it is useful for determination of ferulic Acid in AI-FU-NUAN-GONG Pills.

Abstract: Phthalic acid esters (PAEs) may be used as plasticizer and softener for the manufacturing of plastic products, especially in polyvinyl chloride (PVC). The residue of PAEs in food may affect human health. The method of qualitative analysis and quantitative analysis of 15 PAEs are established by total ion chromatogram (TIC) and select ion monitor (SIM) of gas chromatography-mass spectrometry (GC/MS). Combined with the solid phase extraction (SPE) method, PAEs residue of some fatty food in plastic packaging was detected, with the assessment of PAEs residual be discussed. The correlation coefficient was higher than 0.99. The limit of quantity was 2.93~105.23μg/kg and the limits of detection (LOD) for PAEs had values from 0.97μg/kg to 34.73μg/kg. This method was used for quantification of traces of PAEs in fatty food. The results showed that 9 PAEs residual in fatty food were at the range of <50~1160μg/kg and detection rates were between 16.67 %( 1:6) ~83.33 %( 5:6). None of them was out of national standard.

Abstract: A rapid determination method was builded about content of dioscin in Dioscorea zingiberensis C. H. Wright by near-infrared spectroscopy (NIRS) technology. The calibration model were builded through comparison of the content of dioscin in Dioscorea zingiberensis C. H. Wright and the near infrared spectroscopy of Dioscorea zingiberensis C. H. Wright with partial least squares. The internal correlation coefficient of cross-validation (R²) was 0.99208, root-mean-square error of cross-validation (RMSECV) was 0.0104, and external root mean square prediction deviation RMSEP was 0.0105, and the predictive value of the aversge relative error was 4.12%.

Abstract: In the present study, the Acetyl-coenzyme A carboxylase (ACCase) of Chlorella sp. USTB-01 purified and characterized. Molecular weight of ACCase was calculated to be about 456 kD and was comprised of two identical subunits of 229 kD. The enzymatic characteristics isoelectric point was 6.7. Moreover, a rapid and sensitive assay of High performance liquid chromatography (HPLC) was established to measure overall activity of ACCase in low protein content condition by detect the ACCase activity by measuring ADP production and Acetyl-coenzyme A (Acetyl-CoA).

Abstract: A method was developed for simultaneous determination of imidacloprid,acetamiprid, thiabendazole and carbendazim in lentinus edodes, straw mushroom and oyster mushroom by HPLC. Acetonitrile was edded in the sample for extraction solvent, the sample was purified by NH₂ solid phase extraction cartridge,then detected by HPLC.The results showed that a good linearity in the range of 0.05~5.0μg/mL with the linear correlation coefficients of 0.9991~0.9997, the detection limits of imidacloprid, acetamiprid, thiabendazole and carbendazim were respectively 0.002 mg/kg,0.005mg/kg, 0.003 mg/kg and 0.003 mg/kg.Tests for recovery were made by addition of four pesticidess standards at three different concentration levels (0.1, 0.5 and 1.0 mg/kg) to the blank sample.The mean recovery rates were 86.0%~105.0% , the relative standard deviations were less than 3.5%.The sensitivity, accuracy and precision of this method were able to meet the requirements for pesticide residue analysis.

Abstract: Poisson's ratio is one of the important physical parameters in the finite element calculation model of corn kernel. In this study, through the preparation of the test material and test program design, with the loading speed of the testing machine was 2mm/min, through applied different loading (30N, 90N, 120N and 150N) for Poisson's ratio determination about corn kernel with the experiment. The test results showed that the Poisson's ratio average value in 0.399-0.423 when the corn kernel moisture content was 13.2%, the greater loading was applied, and the smaller value in the fluctuation range of the Poisson's ratio was measured. When applied to the indenter loading of 150N, the corn kernel Poisson ratio fluctuation which was between the minimum and maximum value of 5.1%.

Abstract: A highly sensitive chemiluminescence enzyme immunoassay (CLEIA) method for the determination of bisphenol A (BPA) was developed, which used a secondary antibody labeled with horseradish peroxidase detected with a luminol-based substrate. Under the optimized conditions, the linear range was 0.01μg/mL~0.74μg/mL, and the detection limit was 0.008μg/mL. The average recovery for BPA in barreled water was 104%. This developed method could be applied for the selective, high-throughput, and rapid determination of BPA in barreled water.

Abstract: The paper presents a novel method for the flotation separation of Cu²⁺ using microcrystalline adsorption system loaded with CuI prior to the determination by spectrophotometry. The effects of different parameters,such as the dosages of KI, ascorbic acid and octadecyl trimethyl ammonium bromide (OTMAB),various salts and acidity etc. on the flotation yield of Cu²⁺ have been investigated. The possible flotation separation mechanism of Cu²⁺ was discussed.The results showed that under the optimum conditions,octadecyl trimethyl ammonium bromide cation (OTMAB⁺) reacted with I^- to produce the microcrystalline matter (Ms-M) of (OTMAB⁺·I^-), Cu²⁺ could be reduced to Cu⁺ by ascorbic acid,and then Cu⁺ reacted with I^- to form the precipitation of CuI.The precipitation of CuI was quantificationally adsorbed on the surface of Ms-M of (OTMAB⁺·I^-) and was floated above water phase, the liquid-solid phases were formed with clear interface. In this condition, K⁺,Na⁺,Ca²⁺,Mg²⁺, Zn²⁺,Co²⁺,Al³⁺,Mn²⁺,Ni²⁺ and Fe²⁺ could not be floated.Therefore, Cu²⁺ was separated completely from the above metal ions.A new spectrophotometric method of determination of trace copper by flotation separation using microcrystalline adsorption system loaded with CuI was established.The proposed method has been successfully applied to the determination of Cu²⁺ in various environmental water samples, and the results agreed well with those obtained by AAS method.

Abstract: This paper introduced a simple and rapid electrochemical method for determination of ascorbic acid (AA). A screen-printed carbon electrode modified by multilayer films containing multiwall carbon nanotubes (MWNTs) and redox polymer. The modified electrode exhibited good stability and high electrocatalytic activity towards AA in the presence of uric acid and dopamine even in the real samples. The response current revealed a good linear relationship with the concentration of AA in the range of 5×10^-7 M~7×10^-5 M and the detection limit was 3×10^-7 M.

Abstract: In this paper a novel and sensitive electrochemical sensor for the detection of formaldehyde was developed based on the platinum nanoparticles and L-alanine modified glassy carbon electrode. The sensor was fabricated by two steps. Platinum nanoparticles were immobilized on the electrode via electrodeposition method firstly, then the L-alanine was modified on the electrode by self-assembly method. The structure and morphologies of the Platinum nanoparticles were characterized by SEM and TEM. The electrocatalytic activity of the PtNP-L-alanine/GC electrode for formaldehyde detection in alkaline media was investigated via a series of electrochemical measurements. The PtNP-L-alanine/GC electrode show very high electrochemical activity toward formaldehyde. The oxidation peak current had a linear relationship with the formaldehyde concentration in the 0.3 µmol dm-3 to 4.0 mmol dm-3 range (R=0.9998), while the detection limit was estimated to be 34 nmol dm-3 (S/N=3). Such high sensitivity was attributed to the large surface area of the highly dispersed nanoparticles for electrocatalytic reaction and the fast electron transfer in the composite electrode. It demonstrated that glassy carbon electrode modified by platinum nanoparticles and L-alanine was suitable for the determination of formaldehyde.