Yanfu Huan

Application of microwave techniques in analytical chemistry

Abstract The latest developments in the application of microwave techniques to analytical chemistry are reviewed. Some applications of microwave techniques to sample digestion, solvent extraction, sample drying, the measurement of moisture, analyte desorption and adsorption, sample clean-up, chromogenic reaction, speciation and nebulization of analytical samples are presented.

A highly sensitive and selective fluorescent Cu2+ sensor synthesized with silica nanoparticles.

A novel fluorescent nanosensor for the determination of Cu(2+) was synthesized with N-(quinoline-8-yl)-2-(3-triethoxysilyl-propylamino)-acetamide (QlOEt) grafted onto the surface of silica nanoparticles (SiNPs) using the reverse microemulsion method. Spherical SiNPs were used as substrate and QlOEt was used simultaneously as the binding and readout system for Cu(2+). This sensor has been realized as a highly sensitive and selective technique for the detection and quantification of trace amounts of Cu(2+). The probe exhibits a dynamic response range for Cu(2+) from 2.0 x 10(-6) to 2.0 x 10(-5) M, with a detection limit of 3.8 x 10(-7) M. Other alkali, alkaline earth, and transitional metal ions including Li(+), K(+), Mg(2+), Ca(2+), Sr(2+), Mn(2+), Zn(2+), Mo(6+), Pb(2+), Ag(+) had no significant interference on Cu(2+) determination. Poisonous and flammable reagents are avoided during the synthesis of this nanosensor. Therefore the strategy explored in this work can be extended to the synthesis of other chemo- and biosensors for direct detection of specific targets in an intracellular environment.

Carboxylate-modified squaraine dye doped silica fluorescent pH nanosensors

Novel carboxylate-modified fluorescent silica pH nanosensors were synthesized using a reverse microemulsion method with a pH sensitive squaraine dye used as pH indicator. This pH sensitive squaraine dye was simply doped inside SiNPs without any complicated procedures. To avoid aggregation among the particles and to increase the water solubility of the pH nanosensors, the SiNPs were surface modified with a carboxyl group. This pH probe exhibits a good linear dynamic response between pH 3.01 and 5.72. Many alkali, alkaline earth, and transitional metal ions including Li( + ), Na( + ), K( + ), Rb( + ), Cs( + ), Mg(2 + ), Ca(2 + ), Sr(2 + ), Al(3 + ), V(5 + ), Cr(3 + ), Cr(6 + ), Mn(2 + ), Fe(2 + ), Fe(3 + ), Co(2 + ), Ni(3 + ), Cu(2 + ), Zn(2 + ), As(3 + ), Se(4 + ), Mo(6 + ), Ag( + ), Cd(2 + ), La(3 + ), Er(3 + ), Ir(3 + ), Hg( + ), Hg(2 + ), and Pb(2 + ) had no significant interference on pH value determination. Artificial sample determination showed that the pH nanosensors developed in this work possess a very promising applicability in biological and biomedical fields.

A novel silica-coated multiwall carbon nanotube with CdTe quantum dots nanocomposite.

A novel silica-coated multiwall carbon nanotube (MWNTs) with CdTe quantum dots nanocomposite was synthesized in this paper. Here, we show the in situ growth of crystalline CdTe quantum dots on the surfaces of oxidized MWNTs. The approach proposed herein differs from previous attempts to synthesize nanotube assemblies in that we mix the oxidized MWNTs into CdCl(2) solution of CdTe nanocrystals synthesized in aqueous solution. Reinforced the QD-MWNTs heterostructures with silica coating, this method is not invasive and does not introduce defects to the structure of carbon nanotubes (CNTs), and it ensures high stability in a range of organic solvents. Furthermore, a narrow SiO(2) layer on the MWNT-CdTe heterostructures can eliminate the biological toxicity of quantum dots and carbon nanotubes. This is not only a breakthrough in the synthesis of one-dimensional nanostructures, but also taking new elements into bio-nanotechnology.

An inexpensive continuous-type ultrasonic nebulizer for atomic spectrometry

We developed an inexpensive continuous-type ultrasonic nebulizer for atomic spectrometry based on a domestic humidifier. With this nebulizer, the aerosol introduction rate is about 1.0 mL/min, much greater than that of pneumatic nebulizer. The long-term stability was also satisfactory because both the solution level and the coupling water temperature were held constant. The pumps controlled by a computer allow the nebulizer to work continuously. The results show that both the analytical performance and the cost were satisfactory.

Residue analysis of tetracyclines in milk by HPLC coupled with hollow fiber membranes-based dynamic liquid-liquid micro-extraction

A novel hollow fiber membranes-based dynamic liquid-liquid micro-extraction (HF-DLLME) coupled with HPLC-UV detection has been developed for the residue analysis of tetracyclines in milk samples without deproteinization and degreasing. The influences of experimental parameters were investigated and optimized. The method showed a good performance. The limits of detection (LOD) are in the range of 0.95-3.6μg/L. The recoveries in spiked samples range from 92.38 to 107.3%. The relative standard deviations (RSDs) are lower than 8.66%. The advantages of this method are simple operation, high efficiency, absence of sample carryover and low cost.

A novel UV-visible chemosensor based on the 8-hydroxyquinoline derivative for copper ion detection

A novel UV-visible chemosensor, 4-methyl-2-((quinolinyl-8-amino)methyl)phenol (MQAMP), was designed and synthesized. The spectral properties of its free and Cu2+-coordinated forms were characterized. Under the optimized conditions, MQAMP showed selective and sensitive sensing for copper ions in an ethanol solution. The binding of Cu2+ to MQAMP caused a marked enhancement of the absorbance, and an about 100 nm red-shift of the maximum absorption wavelength. Other ions including Mo6+, Li+, Cs+, As3+, Ca2+, Na+, Cd2+, K+, Mg2+, Pt2+, Sr2+, Ba2+, Al3+, Cr6+, Be2+, Fe3+, Ni2+, F−, CH3COO−, SO42−, NO3−, Cl−, CO32−, and SO32− displayed no significant interference in this detection of Cu2+. The chemosensor exhibited a dynamic response range for Cu2+ from 1.0 × 10−6 to 1.0 × 10−5 mol L−1 with a detection limit of 1.1 × 10−7 mol L−1 (3σ).

A novel 2-(2-Formyl-4-methyl-phenoxy)-N-phenyl-acetamide-based fluorescence turn-on chemosensor for selenium determination with high selectivity and sensitivity

A novel turn-on fluorescent chemosensor, 2-(2-Formyl-4-methyl-phenoxy)-N-phenyl-acetamide (FMPPA) was designed and synthesized, and its photophysical properties were characterized. Upon coordination with Se (IV), the chemosensor showed incredible fluorescence enhancement (turn-on), other alkali, alkaline earth, transitional metal ions, and common anions including Li(+), Na(+), K(+), Rb(+), Cs(+), Be(2+), Mg(2+), Ca(2+), Sr(2+), Ba(2+), Ni(2+), Cu(2+), Cd(2+), Zn(2+), Mn(2+), As(3+), Pt(4+), V(5+), Fe(3+), Mo(6+), Al(3+), CO3(2-), Cl(-), SCN(-), AC(-), NO3(-), F(-), SO4(2-) had no significant interference on Se (IV) determination. The chemosensor exhibits a dynamic response range for Se (IV) from 3.32 × 10(-7) to 2.63 × 10(-6)M, with a detection limit of 9.38 × 10(-9)M (3σ).

Water-soluble porphyrin as temperature sensor based on fluorescent enhancement

A novel water-soluble porphyrin[5,10,15,20-tetra(3-ethoxy-4-hydroxy-5-sulfonate)phenyl porphyrin, H2TEHPPS]_was designed and synthesized, which could be used as a potential fluorescence sensor to detect temperature changes. The studies were performed in solution phase and the concentration of H2TEHPPS was 2.0×10−5 mol/L. The optical properties of H2TEHPPS were investigated based on the UV and fluorescence spectra. The results show that the fluorescence intensity of H2TEHPPS is directly proportional to temperature in the range of 293–353 K. So H2TEHPPS can be used as a molecular temperature sensor in biomedical and other fields.

Quantitative analysis of cefalexin based on artificial neural networks combined with modified genetic algorithm using short near-infrared spectroscopy

In this paper, a novel chemometric method was developed for rapid, accurate, and quantitative analysis of cefalexin in samples. The experiments were carried out by using the short near-infrared spectroscopy coupled with artificial neural networks. In order to enhancing the predictive ability of artificial neural networks model, a modified genetic algorithm was used to select fixed number of wavelength.