Benli Huang

Determination of steroid sex hormones in urine matrix by stir bar sorptive extraction based on monolithic material and liquid chromatography with diode array detection

A simple, rapid and sensitive method for simultaneous determination of six steroid sex hormones in urine matrix was developed by the combination of stir bar sorptive extraction (SBSE) with high performance liquid chromatography (HPLC) and diode array detection (DAD). A poly (methacrylic acid stearyl ester-ethylene dimethacrylate) was synthesized and selected as SBSE extraction medium. To achieve the optimum extraction performance, several parameters, including agitation speed, desorption solvent, extraction and desorption time, pH value, inorganic salt and organic solvent content of the sample matrix were investigated. Under the optimized experimental conditions, low detection limits (S/N=3) and quantification limits (S/N=10) of the proposed method for the target compounds were achieved within the range of 0.062-0.38 and 0.20-1.20 ng/mL, respectively from spiked urine, respectively. The calibration curves of six steroid sex hormones showed good linearity ranging from 1.0 to 200 ng/mL with linear coefficient R2 values above 0.990. Good method reproducibilities presented as intra- and inter-day precisions were also found with the R.S.D.s less than 9.2 and 10.0%, respectively. Finally, the proposed method was successfully applied to the determination of the target compounds in a urine sample from a pregnant woman.

A novel stir bar sorptive extraction coating based on monolithic material for apolar, polar organic compounds and heavy metal ions

In this study, a novel stir bar sorptive extraction (SBSE) based on monolithic material (SBSEM) was prepared. The monolithic material was obtained by in situ copolymerization of vinylpyrrolidone and divinylbenzene in the presence of a porogen solvent containing cyclohexanol and 1-dodecanol with azobisisobutyronitrile as initiator. The influences of polymerization conditions on the extraction efficiencies were investigated, using phenol and p-nitrophenol as detected solutes. The monolithic material was characterized by various techniques, such as elemental analysis, scanning electron microscopy, mercury intrusion porosimetry, infrared spectroscopy. Polycyclic aromatic hydrocarbons were used to investigate the extraction efficiencies of SBSEM for apolar analytes. Hormones, aromatic amines and phenols were selected as test analytes to investigate the extraction efficiencies of SBSEM for weakly and strongly polar compounds. The results showed that the new SBSEM could enrich the above-mentioned organic compounds effectively. It is worthy to mention that the SBSEM can enrich some heavy metal ions, such as Cu(2+), Pb(2+), Cr(3+) and Cd(2+), through coordination adsorption. To our best knowledge, that is the first to use SBSE to enrich heavy metal ions.

Online pre-reduction of selenium(VI) with a newly designed UV/TiO2 photocatalysis reduction device

The online pre-reduction of selenium(VI) has been achieved on a newly designed UV/TiO2 photocatalysis reduction device; its vapor generation efficiency has been improved up to 53.3%.

Electrolytic hydride generation (EC-HG) - a sample introduction system with some special features

Fundamental aspects of electrolytic hydride generation (EC-HG) and the application of EC-HG as a sample introduction system in atomic spectrometry are presented. One of the aims of this review is to help the analyst to select the most suitable electrolytic hydride generator and diverse operating parameters, and especially the choice of the cathode material, in relation to the requirements of the analytical problem. The application of EC-HG in speciation analysis of hydride-forming elements is one of the topics of this review. Additionally, the use of EC-HG is critically evaluated as an alternative to wet chemical hydride generation.

Flow injection–electrochemical hydride generation technique for atomic absorption spectrometry. Invited lecture

A flow injection–electrochemical hydride generation technique for atomic absorption spectrometry has been developed in order to avoid the use of sodium tetrahydroborate, which is capable of introducing contamination. A specially designed thin-layer electrolytic flow cell for hydride generation was used in a normal flow injection system coupled to an electrically heated T-tube atomizer for the atomic absorption measurements. About 200 µl of sample were injected into the electrolyte carrier stream flowing to the electrolytic cell, where hydride-forming elements were reduced to gaseous hydrides. The effects of various factors, e.g., electrode material, electrolyte, current density and carrier stream flow rate, on rate of formation of the hydride and interferences have been studied. The technique has been applied to the determination of As, Se and Sb in various samples. The detection limits for these elements in aqueous solutions were 0.45, 0.62 and 0.92 ng ml–1, respectively, with precisions of 1.2–1.8%.

Preparation and evaluation of stable coating for capillary electrophoresis using coupled chitosan as coated modifier

A coated capillary modified with a coupled chitosan (COCH) was developed by using a simple and fast (60 min) process that could be easily automated in capillary electrophoresis instrument. The COCH coating was achieved by first attaching chitosan to the capillary inner wall, and then coupling with glutaraldehyde, and rinsing chitosan again to react with glutaraldehyde. The COCH coating was stable and showed amphoteric character over the pH range of 1.8-12.0. When the pH value was lower than 4.5, the capillary surface possessed positive charges, which caused a reversal in the direction of the electroosmotic flow (EOF). The normal EOF direction could be obtained when the pH value was higher than 4.5. The COCH coating showed strong stability against 0.1 mol/L HCl, 0.1 mol/L NaOH and other solvents compared with conventional chitosan coating. The relative standard deviation of the run-to-run, day-to-day and capillary-to-capillary coating was all below 2% for the determination of EOF. The COCH-modified capillary was applied to acidic and basic proteins analyses and high efficiency could be attained. The comparison between unmodified capillary, chitosan-modified and COCH-modified capillary for the separation of real sample, extract from Elaphglossum yoshinagae with water, was also studied. Better results could be obtained on COCH-modified capillary than the other two capillaries.

Subcellular distribution of rare earth elements and characterization of their binding species in a newly discovered hyperaccumulator Pronephrium simplex

Subcellular distribution of rare earth elements (REEs, including 14 lanthanides and yttrium) in a newly discovered REE hyperaccumulator, Pronephrium simplex (P. simplex), was determined by a chemical sequence extraction followed by ICP-MS analysis. Results showed that most REEs are associated with cell wall and proteins, and REEs concentration in the proteins, 2899.5mugg(-1), is much higher than those in the cell wall; in the chloroplast of P. simplex, REEs distribute almost equally in chloroplast membrane and thylakoid, while most REEs in the thylakoid are binding with photosystem II (PS II); a new REE-binding peptide in the lamina of P. simplex, which can accumulate REEs up to 3000mugg(-1) and has higher affinity with light REEs, was characterized, indicating that its molecular mass is 5073Da, and may have beta-sheet structure; isoelectrofocusing electrophoretic photograph indicated that it is acidic peptide with IP of 3.7. Such information should be useful for understanding of both the storage and physiological role of REEs in P. simplex and further studies on the phytoremediation of REEs contaminated environments.

Minimizing Matrix Effect by Femtosecond Laser Ablation and Ionization in Elemental Determination

Matrix effect is unavoidable in direct solid analysis, which usually is a leading cause of the nonstoichiometric effect in quantitative analysis. In this research, experiments were carried out to study the overall characteristics of atomization and ionization in laser-solid interaction. Both nanosecond (ns) and femtosecond (fs) lasers were applied in a buffer-gas-assisted ionization source coupled with an orthogonal time-of-flight mass spectrometer. Twenty-nine solid standards of ten different matrices, including six metals and four dielectrics, were analyzed. The results indicate that the fs-laser mode offers more stable relative sensitivity coefficients (RSCs) with irradiance higher than 7 × 10(13) W·cm(-2), which could be more reliable in the determination of element composition of solids. The matrix effect is reduced by half when the fs-laser is employed, owing to the fact that the fs-laser ablation and ionization (fs-LAI) incurs an almost heat-free ablation process and creates a dense plasma for the stable ionization.

Applicability of Standardless Semiquantitative Analysis of Solids by High-Irradiance Laser Ionization Orthogonal Time-of-Fight Mass Spectrometry

A compact high-irradiance laser ionization time-of-flight mass spectrometry system has been developed for the multielemental analysis of solids. Helium was introduced into the ion source as a buffer gas to cool high kinetic energy ions and suppress the interference of multicharged ions. A special pulse train repelling mode was used to achieve explicit spectra. Two quantitative methods are described for the laser ionization mass spectrometry in this paper. The first of these is the routine calibration curve quantitation, in which various matrix-matched standards are required; the second method, which is based on the uniform correlation between the signal and elemental concentration of different samples, is more convenient and covers a typical dynamic range of 6 orders. All the investigations and results indicate satisfactory performance of the newly developed instrument and its applicability for simultaneous multielemental analysis of solid samples.

Preliminary study on a vapor generation technique for nickel without using carbon monoxide by inductively coupled plasma atomic emission spectrometry

Abstract The authors found that volatile nickel species could be generated by reaction in an aqueous solution with sodium or potassium borohydride under appropriate conditions at room temperature without using carbon monoxide. After vapor generation and gas–liquid separation, the volatile species was carried into an inductively coupled plasma (ICP) by argon gas, and the quantity of nickel determined by atomic emission spectrometry. The intensities of the Ni lines were strongly affected by the acidity of samples, the flow rate of argon carrier gas and the length of the transfer tube between the gas–liquid separator and ICP. A detection limit of 0.5 ng/ml and a precision of