Suo Yourui

Determination of Free Fatty Acids by High Performance Liquid Chromatography with Fluorescence Detection and Identification with Mass Spectrometry

Abstract On a reversed-phase Eclipse XDB-C8 column, 20 fatty acids were derivatized using 2-(2-(anthracen-10-yl)-1H-naphtho [2,3-d]imidazol-1-yl) ethyl-p-toluenesulfonate (ANITS) as the pre-column derivatization reagent and were separated by high performance liquid chromatography (HPLC) in conjunction with a gradient elution with fluorescence detection and mass spectrometric identification. The reagent was reacted with fatty acids in the presence of K2CO3 catalyst at 90°C min in N,N-dimethylformamide solvent. The fluorescence excitation and emission wavelength of the derivatives were λex = 250 nm and λem = 512 nm, respectively. The identification of fatty acid derivatives was performed by online MS/APCI (atmospheric pressure chemical ionization source) in positive model detection. All linear correlation coefficients for fatty acid derivatives are over 0.9999, and the detection limits, at a signal-to-noise rate of 3:1, are 24.8-98.8 fmol for labeled fatty acids. The established method is sensitive and reproducible for the determination of free fatty acids from real samples with satisfactory results.

Adsorption of organic dyes by TiO 2 @yeast-carbon composite microspheres and their in situ regeneration evaluation

TiO2@yeast-carbon microspheres with raspberry-like morphology were fabricated based on the pyrolysis method. The obtained products were characterized by field emission scanning electron microscopy (FE-SEM), energy dispersive spectrometry (EDS), and X-ray diffraction (XRD). Effects of initial dye concentration and contact time on adsorption capacity of TiO2@yeast-carbon for cationic dye methylene blue (MB) and anionic dye congo red (CR) were investigated. Experimental data were described by Langmuir, Freundlich, Temkin, and Koble-Corrigan isotherm models, respectively. It was found that the equilibrium data of MB adsorption were best represented by Koble-Corrigan, and CR adsorption was best described by both Freundlich and Koble-Corrigan isotherm models. The kinetic data of MB and CR adsorption fitted pseudo-second-order kinetic model well. The results demonstrated that TiO2@yeast-carbon microspheres achieved favorable removal for the cationic MB in comparison with that for the anionic CR. In addition, regeneration experimental results showed that TiO2@yeast-carbon exhibited good recycling stability, reusability, and in situ renewability, suggesting that the as-prepared TiO2@yeast-carbon might be used as the potential low cost alternative for recalcitrant dye removal from industrial wastewater. One possible mechanism for regenerating dye-loaded TiO2@yeast in situ was also proposed.

Mass Spectrometric Identification of Aliphatic Amines Using 2-(11H-benzo[a]carbazol-11-yl) Ethyl Chloroformate as Fluorescence Labeling Reagent

Abstract A simple and highly sensitive method based on the precolumn derivatization has been developed for the determination of aliphatic amines in food by using a nitrogen-containing 2-(11 H -benzo[a]carbazol-11-yl)ethyl chloroformate (BCEC-Cl) as a fluorescence labeling reagent followed by high-performance liquid chromatography (HPLC) with fluorescence detection, and online postcolumn MS identification. The stable derivatives can be obtained by the labeling reaction of BCEC-Cl with amines in the presence of a borate buffer (pH 9.0) within 3 min. The maximum excitation and emission wavelengths are at λ ex = 279 nm and λ em = 380 nm respectively. Separation of 12 amine-derivatives was achieved by a gradient elution on a reversed-phase Eclipse XDB C 8 (150 mm × 4.6 mm, 5 μm) column with a good baseline resolution. The identification of amine-derivatives is carried out by online postcolumn MS using atmospheric pressure chemical ionization (APCI) as an ion source in positive-ion detection mode. The established method exhibits excellent reproducibility and recovery. Excellent linear responses are observed with coefficients > 0.9996, detection limits (at signal-to-noise ratio of 3:1) are at 1.77–14.4 f mol levels.

4-(1-METHYL-1H-PHENANTHRO[9,10-d]IMIDAZOLE-2-) BENZOIC ACID (MPIBA) AND ITS APPLICATION FOR DETERMINATION OF AMINES BY HIGH PERFORMANCE LIQUID CHROMATOGRAPHY WITH FLUORESCENCE DETECTION AND IDENTIFICATION WITH MASS SPECTROSCOPY/ATMOSPHERIC PRESSURE CHEMICAL IONIZATION

A simple, sensitive, and mild method for the determination of amines based on a condensation reaction with 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (EDC · HCl) as the dehydrant with fluorescence detection has been developed. Amines were derivatized to their acid amides with labeling reagent 4-s(1-methyl-1H-phenanthro[9,10-d]imidazole-2-) benzoic acid (MPIBA). Studies on derivatization conditions indicated that the coupling reaction proceeded rapidly and smoothly in acetonitrile to give the corresponding sensitively fluorescent derivatives with a maximum excitation at λex 260 nm and a maximum emission at λem 446 nm. The labeled derivatives exhibited high stability and were enough to be efficiently analyzed by high-performance liquid chromatography. Identification of derivatives was carried out by online post-column mass spectrometry (LC/APCI–MS/MS) and showed an intense protonated molecular ion corresponding m/z [MH]+ under APCI in positive-ion mode. At the same time, the fluorescence properties of derivatives in various solvents were investigated. The method, in conjunction with a gradient elution, offered a baseline resolution of the common amine derivatives on a reversed-phase Eclipse XDB-C8 column. Liquid chromatography separation for the derivatized amines showed good reproducibility with acetonitrile–water as mobile phase. Detection limits calculated from 90.00 pmol to 88 fmol injection, at a signal-to-noise ratio of 3, were 10.5–53.4 fmol. Excellent linear responses were observed with coefficients of >0.9996. The established method for the determination of aliphatic amines from real wastewater was satisfactory.

Separation of Derivatized Carbohydrates by Capillary Zone Electrophoresis

Abstract A simple and rapid method was developed for the separation of the labeled carbohydrates using 1-naphthyl-3-methyl-5- pyrazolone (NMP) as the derivatization reagent by capillary zone electrophoresis. A 58.5 cm × 50 μm i.d. (50 cm effective length) untreated fused-silica capillary is used. To optimize the conditions, the buffer solution concentration, pH, column temperature, voltage and other factors are evaluated. The results indicate that the buffer concentration and pH value exhibit a significant impact on the separation, but no obvious influences of the temperature, voltage and additives on resolution are observed. On the basis of the optimization, the optimal separation conditions are as follows: 55 mM borate buffer (pH 9.46), voltage of 22 kV, column temperature of 20 °C and DAD detection of 254 nm. The samples are introduced atmospherically with an injection time of 10 s. The results indicate that nine NMP-labeled carbohydrates can be separated with a good baseline resolution within 18 min under the conditions proposed. The Tangutoium Nitratia sample is also analyzed under the optimum conditions. The separation is efficient and rapid with satisfactory results.