液液萃取-气相色谱-质谱法测定墨水中的16种多环芳烃

采用液液萃取-气相色谱-质谱法测定墨水中的16种多环芳烃。样品经二氯甲烷液液萃取后,使用固相萃取技术进行纯化。在气相色谱分离中用DB-5MS色谱柱为固定相,在质谱分析中采用选择离子监测模式。16种多环芳烃在一定的质量浓度范围内与其峰面积呈线性关系,方法的检出限(3S/N)在5.0~30μg·kg-1之间。以空白样品为基体进行加标回收试验,所得回收率在60.6%~116%之间,测定值的相对标准偏差(n=6)在1.5%~5.3%之间。     

Tubular and Microcylindrical Platinum Electrodes for Amperometric Detection of Aminobiphenyls and Aminonaphthalenes in HPLC

Platinum electrodes in microcylindrical and tubular arrangements were compared as working electrodes for amperometric detection of 2‐aminobiphenyl, 4‐aminobiphenyl, 1‐aminonaphthalene, and 2‐aminonaphthalene in HPLC. Factors influencing separation efficiency are favourable for microcylindrical arrangement while tubular arrangement exhibits higher sensitivities and lower limits of detection. These are in the range of 0.0078–0.027 µmol L^?1 for tubular, and 0.11–0.42 µmol L^?1 for microcylindrical arrangement. Further, a new method with nanomolar detection limits was proposed for determination of tested compounds in urine using solid phase extraction for preliminary separation and preconcentration of the analytes.     

Chemometric processing of second-order liquid chromatographic data with UV–vis and fluorescence detection. A comparison of multivariate curve resolution and parallel factor analysis 2

Second-order liquid chromatographic data with multivariate spectral (UV–vis or fluorescence) detection usually show changes in elution time profiles from sample to sample, causing a loss of trilinearity in the data. In order to analyze them with an appropriate model, the latter should permit a given component to have different time profiles in different samples. Two popular models in this regard are multivariate curve resolution-alternating least-squares (MCR-ALS) and parallel factor analysis 2 (PARAFAC2). The conditions to be fulfilled for successful application of the latter model are discussed on the basis of simple chromatographic concepts. An exhaustive analysis of the multivariate calibration models is carried out, employing both simulated and experimental chromatographic data sets. The latter involve the quantitation of benzimidazolic and carbamate pesticides in fruit and juice samples using liquid chromatography with diode array detection, and of polycyclic aromatic hydrocarbons in water samples, in both cases in the presence of potential interferents using liquid chromatography with fluorescence spectral detection, thereby achieving the second-order advantage. The overall results seem to favor MCR-ALS over PARAFAC2, especially in the presence of potential interferents.     

Achieving second order advantage with multi-way partial least squares and residual bi-linearization with total synchronous fluorescence data of monohydroxy–polycyclic aromatic hydrocarbons in urine samples

An attractive approach to handle matrix interference in samples of unknown composition is to generate second- or higher-order data formats and process them with appropriate chemometric algorithms. Several strategies exist to generate high-order data in fluorescence spectroscopy, including wavelength time matrices, excitation–emission matrices and time-resolved excitation–emission matrices. This article tackles a different aspect of generating high-order fluorescence data as it focuses on total synchronous fluorescence spectroscopy. This approach refers to recording synchronous fluorescence spectra at various wavelength offsets. Analogous to the concept of an excitation–emission data format, total synchronous data arrays fit into the category of second-order data. The main difference between them is the non-bilinear behavior of synchronous fluorescence data. Synchronous spectral profiles change with the wavelength offset used for sample excitation. The work presented here reports the first application of total synchronous fluorescence spectroscopy to the analysis of monohydroxy-polycyclic aromatic hydrocarbons in urine samples of unknown composition. Matrix interference is appropriately handled by processing the data either with unfolded-partial least squares and multi-way partial least squares, both followed by residual bi-linearization.     

Preparation and Application of Fullerene C60‐Polymers in Piezoelectric Quartz Crystal Sensors for Hemoglobin and Olefins

The C60—polycinnamaldehyde (C₆₀—PCA) and C60—polyphenylacetylene (C60—PPA) polymers were synthesized by the Friedel—Craft reaction and applied as piezoelectric (PZ) quartz crystal coating materials. A C60—polycinnamaldehyde (PCA) coated piezoelectric quartz crystal liquid sensor with a homemade computer interface was prepared and applied as a PZ hemoglobin sensor. The adsorption of hemoglobin onto the C60—PCA coated crystal resulted in a decreased oscillating frequency. The variations in crystal frequency were converted to voltage with a frequency to voltage converter, followed by amplification with OPA and data acquisition with an analog to digital converter. The PZ hemoglobin sensor exhibited good sensitivity of 6530 Hz/(mg/mL) with a detection limit at the ppm level for hemoglobin. Further, a C60—polyphenylacetylene (C60—PPA) coated piezoelectric quartz crystal gas sensor with an Intell‐8255 data processing system for various olefin vapors was also made. The aromatic hydrocarbons such as toluene seem to have greater adsorption onto C60—PPA membrane than alkynes, alkenes, and alkanes. The adsorption of polycyclic aromatic hydrocarbons (PAHs) onto the C60—PPA membrane was also examined. The C₆₀—PPA coated PZ crystal gas sensor showed much better sensitivity for PAHs than for other olefins such as toluene, 1‐hexyne and 1‐hexene, and a much larger frequency shift for naphthalene than other PAHs was also found.     

Cobalt oxide nanoparticles as a novel high-efficiency fiber coating for solid phase microextraction of benzene,toluene, ethylbenzene and xylene from aqueous solutions

In this work cobalt oxide nanoparticles were introduced for preparation of a novel solid phase microextraction (SPME) fiber coating. Chemical bath deposition (CBD) technique was used in order for synthesis and immobilization of the Co₃O₄ nanomaterials on a Pt wire for fabrication of SPME fiber. The prepared cobalt oxide coating was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The fiber was evaluated for the extraction of benzene, toluene, ethylbenzene and xylene (BTEX) in combination with GC–MS. A simplex optimization method was used to optimize the factors affecting the extraction efficiency. Under optimized conditions, the proposed fiber showed extraction efficiencies comparable to those of a commercial polydimethylsiloxane (PDMS) fiber toward the BTEX compounds. The repeatability of the fiber and its reproducibility, expressed as relative standard deviation (RSD), were lower than about 11%. No significant change was observed in the extraction efficiency of the new SPME fiber after over 50 extractions. The fiber was successfully applied to the determination of BTEX compounds in real samples. The proposed nanostructure cobalt oxide fiber is a promising alternative to the commercial fibers as it is robust, inexpensive and easily prepared.     

Electrochemical detection of benzo(a)pyrene and related DNA damage using DNA/hemin/nafion–graphene biosensor

A novel electrochemical biosensor, DNA/hemin/nafion–graphene/GCE, was constructed for the analysis of the benzo(a)pyrene PAH, which can produce DNA damage induced by a benzo(a)pyrene (BaP) enzyme-catalytic product. This biosensor was assembled layer-by-layer, and was characterized with the use of cyclic voltammetry, electrochemical impedance spectroscopy (EIS) and atomic force microscopy. Ultimately, it was demonstrated that the hemin/nafion–graphene/GCE was a viable platform for the immobilization of DNA. This DNA biosensor was treated separately in benzo(a)pyrene, hydrogen peroxide (H₂O₂) and in their mixture, respectively, and differential pulse voltammetry (DPV) analysis showed that an oxidation peak was apparent after the electrode was immersed in H₂O₂. Such experiments indicated that in the presence of H₂O₂, hemin could mimic cytochrome P450 to metabolize benzo(a)pyrene, and a voltammogram of its metabolite was recorded. The DNA damage induced by this metabolite was also detected by electrochemical impedance and ultraviolet spectroscopy. Finally, a novel, indirect DPV analytical method for BaP in aqueous solution was developed based on the linear metabolite versus BaP concentration plot; this method provided a new, indirect, quantitative estimate of DNA damage.     

A new interface for coupling solid phase microextraction with liquid chromatography

A modified Rheodyne 7520 microsample injector was used as a new solid phase microextraction (SPME)–liquid chromatography (LC) interface. The modification was focused on the construction of a new sample rotor, which was built by gluing two sample rotors together. The new sample rotor was further reinforced with 3 pieces of stainless steel tubing. The enlarged central flow passage in the new sample rotor was used as a desorption chamber. SPME fiber desorption occurred in static mode. But all desorption solvent in the desorption chamber was injected into LC system with the interface. The analytical performance of the interface was evaluated by SPME–LC analysis of PAHs in water. At least 90% polycyclic aromatic hydrocarbons (PAHs) were desorbed from a polyacrylonitrile (PAN)/C18 bonded fuse silica fiber in 30 s. And injection was completed in 20 s. About 10–20% total carryovers were found on the fiber and in the interface. The carryover in the interface was eliminated by flushing the desorption chamber with acetonitrile at 1 mL min⁻¹ for 2 min. The repeatability of the method was from 2% to 8%. The limit of detection (LOD) was in the mid pg mL⁻¹ range. The linear ranges were from 0.1 to 100 ng mL⁻¹. The new SPME–LC interface was reliable for coupling SPME with LC for both qualitative and quantitative analysis.     

Computational Study of van der Waals Complexes between Borylenes and Hydrocarbons

The addition of borylenes (RB) to prototypical carbon?carbon multiple bonds (ethyne, ethene) and the insertion into a C?H bond of methane involves weakly bound van der Waals complexes of the reaction partners according to computational chemistry methods. Geometries of all complexes were optimized using spin‐component scaled second‐order Møller–Plesset perturbation theory (SCS‐MP2) in combination with a quadruple‐ζ (def2‐QZVP) basis set. Energies were further refined using the coupled‐cluster (CCSD(T)) method in combination with basis sets up to quadruple‐ζ quality (def2‐QZVP and aug‐cc‐pVTZ). All of the complexes of borylenes studied correspond to shallow minima on their potential‐energy surfaces. Borylene complexes with ethyne are the most stable and those with methane are the least stable ones. Aminoborylene complexes BNHR with ethyne and ethene are stabilized mainly by NH ??? π interactions. Symmetry‐adapted perturbation theory (SAPT) was performed to analyze the nature of the interaction between borylene molecules and hydrocarbons. Most of the ethyne complexes are dominated by electrostatic interactions, whereas for most of the ethene and all of the methane complexes the interaction is mainly dispersive.     

Synthesis of Nitrogen‐Doped ZigZag‐Edge Peripheries: Dibenzo‐9a‐azaphenalene as Repeating Unit

A bottom‐up approach toward stable and monodisperse segments of graphenes with a nitrogen‐doped zigzag edge is introduced. Exemplified by the so far unprecedented dibenzo‐9a‐azaphenalene (DBAPhen) as the core unit, a versatile synthetic concept is introduced that leads to nitrogen‐doped zigzag nanographenes and graphene nanoribbons.