Trace elemental analysis of single yeast cells with time-resolved inductively coupled plasma mass spectrometry (ICP-MS) was successfully carried out, where a high efficiency cell introduction system (HECIS) consisting of the high performance concentric nebulizer (HPCN) and a low-volume (15 mL) on-axis spray chamber utilizing a sheath gas flow were used. Cell adsorption to the flow injector and sample tubing was reduced with the addition of a simple 4.3 mmol L−1 of NaCl solution to the cell suspension and cell flowing liquid, allowing consecutive measurements without fear of significant contamination from previous measurements. Initially using a quadrupole mass analyzer ICP-MS (ICP-QMS) at its lowest integration time (10 ms), current spikes corresponding to separate cell events were detected for several elements (Mg, P, Ca, Mn, Fe, Cu, and Zn) on the introduction of the cell suspension. On comparing the number of peaks in the spectrum for phosphorous with the cell count using a haemocytometer, a reproducible cell transport efficiency of 75.0 ± 4.7% was achieved. Preliminary experiments into using time of flight ICP-MS (ICP-TOFMS) for single-cell analysis were carried out, allowing quasi-simultaneous multielement detection. The spectra of Mg, P, Ca, Mn, Fe, Cu, and Zn, with a time resolution of 1 ms were simultaneously obtained in one measurement. A relatively strong correlation was observed for the spectra between P and Zn (correlation factor 0.69), P and Mg (0.63), and Mg and Zn (0.63). These results indicate that the time resolved quasi-simultaneous multielement measurement may be useful for the correlation analysis of multielements in cells.
Considering the crucial role played by microRNAs (miRNAs) in biological processes, we developed a novel strategy for simple and colorimetric detection of miRNA by combining target amplification with DNAzyme. Throughout the work, a 22-nt oligonucleotide sequence was used as a model analyte. A label-free hairpin probe (HP) was used as a simple platform for sensing the target. In the presence of the target, the HP was opened, and then the isothermal circular strand-displacement process occurred with the help of a primer, deoxynucleotide solution mixture (dNTPs), Klenow fragment exo− polymerase, and Nb.BbvCI nicking enzyme. As a result, the target was recycled and multicopies of target analogues were generated that function in the same manner as the target, accompanied by the accumulation of signal elements. In this work, as low as 0.5 fM nucleic acid target was detected by horseradish peroxidase-mimicking DNAzyme catalyzing the oxidation of ABTS2− to colored ABTS•−.
We studied the direct electron transfer (DET) of proteins on a carbon nanofiber (CNF) modified carbon film electrode by employing the one-step UV/ozone treatment of CNF. This treatment changed the CNF surface from hydrophobic to hydrophilic because a sufficient quantity of oxygen functional groups was introduced onto the CNF surface. Furthermore, this simple approach increased both the effective surface area and the number of edge-plane defect sites. As a result, the reversibility of redox species, such as ferrocyanide and dopamine, was greatly improved on the treated electrode surface. We obtained on efficient DET of bilirubin oxidase (BOD) and cytochrome c (cyt c) at the treated CNF electrode, which exhibited 38 (for BOD) and 6 (for cyt c) times higher than that at untreated CNF modified electrode. These results indicate that the combination of nanostructured carbon and this UV/ozone treatment process can efficiently create a functionalized surface for the electron transfer of proteins.
Novel Co-N-S/C catalysts supported on carbon were obtained using a two-step procedure. The procedure consisted of the synthesis of a carbon-supported Co-2-mercaptobenzothiazole (denoted as Co-MBT/C) complex using a solvent-milling method and the pyrolysis of the Co-MBT/C complex. 2-Mercaptobenzothiazole (MBT) was used as the nitrogen and sulfur ligand for Co-MBT complex formation. X-ray diffraction (XRD), TEM, EDS and elemental mappings were used to characterize the structure changes in these catalysts before and after the heat-treatment. Several catalysts were synthesized by varying the amount of cobalt salt and pyrolysis temperature. The results showed that the optimal cobalt salt content and pyrolysis temperature were around 25 wt% and 800°C. Under the optimal conditions, an onset potential of 0.20 V and a half-wave potential of 0.05 V were reached in an alkaline electrolyte, and the Co-N-S/C catalyst possessed high catalytic activity and catalytic stability towards an oxygen reduction reaction (ORR). These results indicated that Co-N-S/C is a promising catalyst for the ORR.
A simple, but highly sensitive, electrochemical sensor for the determination of salvianic acid A sodium (SAS) based on reduced graphene oxide (rGO) is reported. The sensor (rGO/GCE(ox)) was prepared by coating an rGO film on the surface of a pre–anodized glassy carbon electrode (GCE(ox)) through a dipping-drying method. The characteristic of the modified electrode was examined by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). Compared with bare GCE, GCE(ox) and rGO modified GCE, this sensor exhibited a superior ability for detecting SAS. Under the selected conditions, the reduction current had a good linear relationship with the SAS concentration in the range of 8.0 × 10−8 – 2.0 × 10−5 mol L−1, with a low detection limit of 2.0 × 10−8 mol L−1. Furthermore, the method was also successfully applied to detect SAS in medicinal tablets.
A monolithic capillary column prepared with glycidyl methacrylate (GMA) and poly(ethylene glycol) dimethacrylate (PEGDMA) was investigated and used in capillary liquid chromatography. The polymer monolith was synthesized in the presence of methanol and decanol as the biporogenic solvents by in situ polymerization of GMA and PEGDMA, and the optimum composition of monomer and porogen was investigated. After polymerization, glycidyl groups were hydrolyzed with sulfuric acid to produce diol groups at the surface of the porous monolith via epoxy-ring-opening. The GMA content in the polymerization mixture affected the hydrophilicity of the monolith. The separation capability was evaluated by separation of phenol compounds, phthalic acids, and polycyclic aromatic hydrocarbons. The poly(GMA-PEGDMA) monolithic capillary column exhibited satisfactory stability.
In this study, 6-azido-2,3-di(p-chlorophenylcarbamoylated) cellulose was synthesized and bonded onto aminized silica gel to obtain a new chiral stationary phase. Enantioselectivity of the chiral stationary phase and Chiralcel OF suggested promising chiral separation ability of the new cellulose chiral stationary phase. In addition, the effect of trifluoroacetic acid, diethylamine on enantioselectivity and retention factors on the chiral stationary phase in high performance liquid chromatography was investigated. Experimental results revealed that resolution increased as the trifluoroacetic acid concentration increased to 0.3% while resolution declined as the diethylamine concentration increased. Therefore, the optimal concentrations of trifluoroacetic acid and diethylamine were determined to be 0.3 and 0.1%, respectively. In most cases, trifluoroacetic acid shortened the retention of the first eluted enantiomer while it increased the retention of the other. For acidic compounds, with the existence of diethylamine in the mobile phase, the retention of both enantiomers decreased. But for basic compounds, the retention of both enantiomers increased.
This paper reports mass spectra and linear temperature programmed retention indices (I T) for 31 esters of mono- and sesquiterpene alcohols with hydroxycinnamic acids. In this study, 14 phenylpropenoids were synthesized by esterification of terpenols with p-coumaric, ferulic, caffeic and sinapinic acids. Other phenylpropenoids were semi-quantitatively isolated by column chromatography from exudates covering the buds of two birch species (Betula pubescens and B. litwinowii). Main diagnostic ions in phenylpropenoids mass spectra were determined by GC/MS analysis. The possibility of predicting I T values was demonstrated with standard error of prediction between 3 and 11 of retention index units.
An analytical method was developed for the extraction and determination of pyrethroid pesticide residues in tobacco. The modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) method was applied for preparing samples. In this study, methyl cyanide (MeCN)-saturated salt aqueous was used as the two-phase extraction solvent for the first time, and a vortex shaker was used for the simultaneous shaking and concentration of the analytes. The effects of experimental parameters on extraction and clean-up efficiency were investigated and optimized. The analytes were determined by gas chromatography–mass spectrometry–selected ion monitoring (GC-MS-SIM). The obtained recoveries of the analytes at three different fortification levels were 76.85 – 114.1% and relative standard deviations (RSDs) were lower than 15.7%. The limits of quantification (LOQs) were from 1.28 to 26.6 μg kg−1. This method was also applied to the analysis of actual commercial tobacco products and the analytical results were satisfactory.
The use of natural reagents from plant extracts for chemical analysis is one of the approaches in the development of low cost and environmentally friendly green analytical chemistry methodology. Here, crude extract from Indian Almond (Terminalia Catappa L.) leaves was used for colorimetric determination of aluminum by monitoring the absorbance of the Al3+-extract complex at 435 nm. Dry leaves and freeze-dried fresh leaf extract can be kept for extended use. A simple flow injection analysis (FIA) system was also employed for rapid analysis (approximately 180 injections/h). The linear working range up to 100 mg L−1 was established with a detection limit (blank + 3SD) of 0.8 mg L−1, a limit of quantitation (blank + 10SD) of 2.4 mg L−1, and a relative standard deviation of 3 – 5%. This simple green analytical chemistry methodology was applied for the determination of Al3+ in waste water samples from ceramic factories. The results agreed well with the results obtained from the ICP-OES technique.
A method is described using rapid and sensitive Fourier transform near-infrared spectroscopy (FT-NIRS) for the determination of rhein-L-arginine cocrystal (argirein). By mixing different values of argirein into different proportions with rhein and arginine, we obtained 41 batches of samples to deatermine. Partial least squares (PLS) regression was selected as the analysis type and standard normal variate (SNV) and original spectra were adopted for the spectral pretreatment. The correlation coefficient (R) of the calibration model was above 0.99 and the root mean square error of predictions (RMSEP) was under 0.012. The developed model was applied to 10 batches of known samples with satisfactory results. The established method is validated and can be applied to the intrinsic quality control of synthetic products and other cocrystals.
A ternary mixed-solvent solution of water–acetonitrile–ethyl acetate changes from a homogeneous (single-phase) to a heterogeneous (two-phase) system with temperature and/or pressure changes. In this study, we used this system in a batch vessel to extract metal ions. Water–acetonitrile–ethyl acetate at a volume ratio of 3:8:4 containing 8-hydroxyquinoline was used as a ternary mixed-solvent solution, changing from homogeneous at 25°C to heterogeneous after 30 min at 0°C. The two-phase system comprised an upper (organic solvent-rich) phase and a lower (water-rich) phase at a volume ratio of 6:1. Fe(III), Co(II), and Ni(II) were used as model metal ions dissolved in the homogeneous solution at 25°C. The distribution constants and the extraction percentages were determined by measuring the metal ion concentrations in the upper and lower phases with inductively coupled plasma atomic emission spectroscopy. The metal ions were extracted through complexation with 8-hydroxyquinoline in the organic-rich phase with distribution constants and extraction percentage values, respectively, of 0.47 and 74 for Fe(III), 0.15 and 47 for Co(II), and 0.08 and 32 for Ni(II).
A simple and sensitive spectrophotometric method, based on reaction between Ni(II) ion and D-penicillamine (PEN), was developed. The proposed SIA system enhanced the analytical applicability of the reaction of complexation, and allowed the determination of PEN in the concentration range of 3.0 × 10−6 – 2.0 × 10−4 mol L−1 with a sampling rate of 200 h−1. With the proposed SIA system, PEN could be accurately determinated up to 0.9 nmol quantity. The method was successfully applied to the determination of PEN in laboratory samples and pharmaceuticals.
Carbon monoxide (CO) and carbon dioxide (CO2) were determined in a conventional capillary gas chromatography–flame ionization detector (GC-FID) by introducing a packed-capillary column and a methanizer. Due to good compatibility with rapid temperature-programmed operation of the packed capillary column, several volatile compounds, including CO and CO2, were rapidly eluted along with satisfactory resolution and sample loading capacity. The limit of quantifications of CO and CO2 were 5 and 3 ppm, respectively, with an injection volume of 0.5 mL. The developed system was then successfully applied to evaluating the photocatalytic decomposition of volatile organic compounds on titanium dioxide (TiO2).
A new, simple and sensitive solid-phase spectrometry (SPS) that is easily applicable to the on-site analysis of targeted chemical components in water at μg dm−3 or sub-μg dm−3 levels is proposed in this study. The main features of the SPS are the simplicity of operation, high sensitivity and applicability to real samples without the need for any pretreatment procedures. A portable spectrophotometer, consisting of an LED light source, a grating and a CCD, was used for the solid-phase light measurements. The universal applicability of the proposed system to on-site analysis was evaluated by determining phosphate, chromium(VI) and iron(II) in natural water.