ABSTRACT
Five-way high performance liquid chromatography-diode array detection (HPLC-DAD)-kinetic-pH data were obtained by recording the kinetic evolution of HPLC-DAD signals of samples at different pH values and a new fourth-order calibration method, alternating quinquelinear decomposition (AQQLD) based on pseudo-fully stretched matrix forms of the quinquelinear model, was developed. Simulated data were analyzed to investigate the performance of AQQLD in comparison with five-way parallel factor analysis (PARAFAC). The tested results demonstrated that AQQLD has the advantage of faster convergence rate and being insensitive to the excess component number adopted in the model. Then, they have been successfully applied to investigate quantitatively the kinetics of naptalam (NAP) hydrolysis in two practical systems. Additionally, the serious chromatographic peak shifts were accurately corrected by means of chromatographic peak alignment method based on abstract subspace difference. The good recoveries of NAP were obtained in these samples by selecting the time region of chromatogram. The elution time, spectral, kinetic time and pH profiles resolved by the chemometric techniques were in good agreement with experimental observations. It demonstrates the potential for the utilization of fourth-order data for some complex systems, opening up a new approach to fourth-order data generation and subsequent fourth-order calibration.
ABSTRACT
Carbon dots capped with polyethyleneimine (CD-PEI) were synthesized and applied in selective separation and preconcentration of trace Cr(VI). Dispersed particle extraction (DPE) slurry sampling with flame atomic absorption spectrometry (FAAS) was used to selectively and sensitively determine Cr(VI) in water samples. The as-synthesized CD-PEI was confirmed by Fourier transform infrared spectroscopy, high-resolution transmission electron microscopy, elemental analysis, fluorescence and zeta potential measurement. The adsorption of Cr(VI) on CD-PEI was evaluated. Its isothermal adsorption was studied and fitted in the Langmuir model. Nearly 85% of Cr(VI) was adsorbed within 10 min showed that the CD-PEI exhibited fairly fast kinetics for the sorption of Cr(VI). Experimental conditions, including the content and size of CD-PEI, sample pH, adsorption time, sample volume, slurry volume and interfering ions, were further optimized to obtain efficient preconcentration and high-precision determination of Cr(VI). CD-PEI with small size turned to be a good candidate for the preparation of slurry. CD-PEI served not only as a promising adsorbent for separation and preconcentration of Cr, but also a signal-enhancing agent in FAAS. The method achieved an enhancement factor of 30 and a detection limit (S/N=3) of 0.21 µg L(-1) Cr(VI) with a consumption of 14.0 mL sample and an adsorption time of 5 min, which provided two times of signal enhancement. The RSD for 11 replicate measurements of 5.0 µg L(-1) Cr(VI) was 2.8%. The possible signal enhancement mechanism was proposed. The developed method has been applied to determine trace Cr(VI) in a variety of water samples.
ABSTRACT
Random composites with nickel networks hosted randomly in porous alumina are proposed to realize double negative materials. The random composite for DNMs (RC-DNMs) can be prepared by typical processing of material, which makes it possible to explore new DNMs and potential applications, and to feasibly tune their electromagnetic parameters by controlling their composition and microstructure. Hopefully, various new RC-DNMs with improved performance will be proposed in the future.
Subject(s)
Aluminum Oxide/chemistry , Nickel/chemistry , Magnetic Fields , Metal Nanoparticles/chemistry , Metal Nanoparticles/ultrastructure , PorosityABSTRACT
BACKGROUND: We previously showed that nano-hydroxyapatite/carboxymethyl chitosan (n-Ha/CMCS) displayed excellent mechanical properties, good degradation rates and exceptional biocompatibility, with negligible toxicity. The aim of this study was to determine the effect of the same composite with vascular endothelial growth factor (VEGF)- transfected bone marrow stromal cells (BMSCs) in a rabbit radial defect model. METHODS: The nano-hydroxyapatite was produced through co-precipitation. The n-HA/CMCS scaffold was produced by particle filtration and lyophilization followed by genipin crosslinking. Total RNA from rabbit bone was reverse-transcribed to synthesize VEGF165-pcDNA3.1 that was transfected into the BMSCs. The composite was implanted into a rabbit radial defect model, and the osteogenic activity examined by gross morphology, X-ray examination and hematoxylin and eosin (HE) staining. RESULTS: The microstructure and mechanical property of the n-HA/CMCS scaffold resembled natural cancellous bone. Compared with glutaric dialdehyde crosslinked scaffolds, the genipin crosslinked scaffold was less toxic, and displayed a higher capacity to promote cell adhesion and proliferation. Spontaneous fluorescence of the composite permitted visualization of the composite-bone interface and the adhesion behavior of cells on the scaffold under laser scanning confocal microscopy. The scaffold with VEGF-transfected BMSCs bridged the bony defect and promoted healing, with most of the implanted material being replaced by natural bone over time with little residual implant. Using X-ray, we noted obvious callus formation and recanalization of the bone marrow cavity. Furthermore, HE stained sections showed new cortical bone formation. CONCLUSIONS: The n-HA/CMCS scaffold composite with VEGF-trasnfected BMSCs is biocompatible, nontoxic, promotes the infiltration and formation of the microcirculation, and stimulates bone defect repair. Furthermore, the degradation rate of the composite matched that of growing bone. Overall, this composite material is potentially useful for bone defect repair.
