[Selenium speciation in watermelon by g-C3N4 enrichment combined with capillary electrophoresis-inductively coupled plasma-mass spectrometry].

Selenium is one of the essential trace elements in the human body, and it plays a critical role in human health. In this work, 2.0 g melamine was placed in an alumina crucible, which was heated in a box-type resistance furnace for 2 h at 600 ℃, at the heating rate of 3 ℃/min, and then cooled to room temperature. After cooling, yellow graphite phase carbon nitride (g-C3N4) nanosheets were obtained. Subsequently, 500 mg of the nanosheets was dispersed in 50 mL water with ultrasonication for 10 h in order to remove the residual un-exfoliated g-C3N4 nanoparticles and large-sized nanosheets. The obtained suspension was centrifuged at about 10000 r/min, followed by drying at 60 ℃ to produce g-C3N4. The prepared g-C3N4 was characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), and field emission-environmental scanning electron microscopy (SEM) analyses. Given that the selenium content in actual samples is very low, high sensitivity, and accuracy are imperative for selenium detection. The combination of capillary electrophoresis (CE) with inductively coupled plasma-mass spectrometry (ICP-MS) can greatly improve the sensitivity, accuracy, and speed of the analysis. A novel method based on CE-ICP-MS was established for the determination of selenourea (SeUr), L-selenocystine (SeCys2), DL-selenomethionine (SeMet), selenite (Se(Ⅳ)), selenate (Se(Ⅵ)), and selenoethionine (SeEt) in watermelon. The selenium species in watermelon were extracted by ultrasonication with pepsin as an extractant and g-C3N4 enrichment. The enrichment factor of g-C3N4 ranged from 12 to 29. Six selenium species were completely separated within 11 min in a 100-cm-long capillary with 100 µm internal diameter, at an applied voltage of 22 kV, using a buffer solution of 8 mmol/L NaH2PO4-12 mmol/L H3BO3-0.2 mmol/L cetyl trimethyl ammonium bromide (CTAB; pH 9.2). The interference in the selenium detection was eliminated using a dynamic reaction cell with CH4. The linear correlation coefficients of all the selenium species were greater than 0.9995. Under the optimal conditions, the limits of detection (3 σ, σ for standard deviation, as Se) for SeUr, SeCys2, SeMet, Se(Ⅳ), Se(Ⅵ), and SeEt were 6.2, 30, 11, 8.2, 48, and 5.5 ng/L, respectively. The linear range (as Se) for SeUr, SeCys2, SeMet, Se(Ⅳ), Se(Ⅵ), and SeEt were 0.017-20 µg/L, 0.091-50 µg/L, 0.032-40 µg/L, 0.023-60 µg/L, 0.015-75 µg/L, and 0.015-30 µg/L, respectively. The recoveries ranged from 96.0% to 106%, and the relative standard deviations (RSDs; n=5) were less than 3%. The developed method is simple, rapid, and sensitive, and it is also suitable for the detection of selenium species in other food and environmental samples.

A highly efficient introduction system for single cell- ICP-MS and its application to detection of copper in single human red blood cells.

A method of simultaneous cell counting and determination of metals in single cells using time-resolved inductively coupled plasma-mass spectrometry (ICP-MS) was reported. A facile, low cost and highly efficient single-cell introduction system of time-resolved ICP-MS consists of a flow cell, a visual contrast calibration device, a customized nebulizer and a fabricated spray chamber. The flow cell includes a cell sample tube, a sheath liquid tube and a flow chamber. The visual contrast calibration device was composed of a microscope with a 16 × microscope objective (160 × total magnification). The flow chamber was used to combine a flow of red blood cell suspension (0.800 µL/min) and a flow of PBS (4.40 µL/min) into the nebulizer. The intact cells were directly introduced with the single-cell introduction system into the plasma via nebulizing, and then ion plumes corresponding to single cells were individually detected with mass spectrometer. The frequency of the spikes directly reflects the number of cells, and the intensity of spikes is proportional to the concentration of copper within one cell. The single-cell introduction system can be transported into the ICP-MS via a customized transport system with 100% efficiency. A high cell introduction efficiency into the plasma supports for a reduction of cell consumption. The Cu signal frequency was about 120 cell events per minute. This single-cell introduction system simplifies the introduction of individual and intact cells. The copper content in single red blood cell was 0.20-0.40 fg.

Based on ZnSe quantum dots labeling and single particle mode ICP-MS coupled with sandwich magnetic immunoassay for the detection of carcinoembryonic antigen in human serum.

A highly sensitive sandwich-type magnetic immunoassay based on inductively coupled plasma mass spectrometry detection in single particle mode, with ZnSe Quantum dots (QDs) serving as model tags, was proposed. The transient signals induced by the flash of ions (64Zn+) in the plasma torch from the ionization of nanoparticles tagged on antibody were recorded in a single particle mode. The frequency of transient signals is directly related to the concentration of nanoparticle tags, and the concentration of nanoparticle tagged antibodies can be quantified by the frequency of transient signals. Amino-modified magnetic nanoparticles (AMNPs) were synthesized and conjugated with primary carcinoembryonic antigen (CEA) antibody to extract the target biomarker. ZnSe QDs were synthesized as a probe to determine CEA by ICP-MS. A detection limit of 0.006 ng mL-1 was obtained for CEA after immunoreactions, and a wide linear range of 0.02-100 ng mL-1 with the relative standard deviation (RSD) was 4.4%. The method was successfully applied to human serum samples.

A novel electrochemiluminescence sensor coupled with capillary electrophoresis for simultaneous determination of quinapril hydrochloride and its metabolite quinaprilat hydrochloride in human plasma.

A novel electrochemiluminescence (ECL) sensor with composite consisted of silica-sol, Zinc oxide nanoparticles (ZnO NPs), polyvinylpyrrolidone (PVP) and tris(2, 2'-bipyridine) ruthenium (II) was constructed. A new method for simultaneous determination of quinapril hydrochloride (QHCl) and its metabolite quinaprilat hydrochloride (QTHCl) in human plasma was developed using the ECL sensor coupled with capillary electrophoresis (CE). ECL intensities of QHCl and QTHCl increased dramatically when the ECL sensor was used as working electrode. The running buffer contains 14mmol/L phosphate (pH 8.0) and 20% n-propyl alcohol. Under optimized experimental conditions, the linearity ranges of the method are 0.007-8.0µg/mL for QHCl and 0.009-8.3µg/mL for QTHCl. The detection limits of QHCl and QTHCl (S/N=3) are 3.6ng/mL and 3.9ng/mL, respectively. The method was applied for the simultaneous determination of QHCl and QTHCl in human plasma with satisfactory results.

Simultaneous electrochemiluminescence determination of galanthamine, homolycorine, lycorenine, and tazettine in Lycoris radiata by capillary electrophoresis with ultrasonic-assisted extraction.

After ultrasonic-assisted extraction, four lycoris radiata alkaloids: galanthamine, homolycorine, lycorenine, and tazettine were determined by capillary electrophoresis electrochemiluminescence. Polyvinylpyrrolidone was added to the running buffer (RB) to obtain better resolution. Experimental conditions influencing the determination were examined, including the additives, detection potential, separation voltage, injection voltage and time, and RB pH and concentration. Under optimal experimental conditions, the baseline separation of the four alkaloids occurred within 16min. The proposed method displayed the following linear ranges (in ng/mL): galanthamine [60-5000], homolycorine [40-5000], lycorenine [5.0-1500], and tazettine [8.0-2500]. The detection limits in ng/mL, (S/N=3), were galanthamine [14], homolycorine [11], lycorenine [1.8], and tazettine [3.1]. Intra-day and inter-day RSDs for the four alkaloids of the six replicates were less than 2.7% and 3.1%, respectively. The recoveries in% were: tazettine [102.5], lycorenine [98.20], galanthamine [97.30], and homolycorine [98.33].

An environmentally-friendly, highly efficient, gas pressure-assisted sample introduction system for ICP-MS and its application to detection of cadmium and lead in human plasma.

An environmentally friendly and highly efficient gas pressure-assisted sample introduction system (GPASIS) was developed for inductively-coupled plasma mass spectrometry. A GPASIS consisting of a gas-pressure control device, a customized nebulizer, and a custom-made spray chamber was fabricated. The advantages of this GPASIS derive from its high nebulization efficiencies, small sample volume requirements, low memory effects, good precision, and zero waste emission. A GPASIS can continuously, and stably, nebulize 10% NaCl solution for more than an hour without clogging. Sensitivity, detection limits, precision, long-term stability, double charge and oxide ion levels, nebulization efficiencies, and matrix effects of the sample introduction system were evaluated. Experimental results indicated that the performance of this GPASIS, was equivalent to, or better than, those obtained by conventional sample introduction systems. This GPASIS was successfully used to determine Cd and Pb by ICP-MS in human plasma.

An ultrasensitive electrochemiluminescence sensor based on reduced graphene oxide-copper sulfide composite coupled with capillary electrophoresis for determination of amlodipine besylate in mice plasma.

A new electrochemiluminescence (ECL) sensor based on reduced graphene oxide-copper sulfide (rGO-CuS) composite coupled with capillary electrophoresis (CE) was constructed for the ultrasensitive detection of amlodipine besylate (AML) for the first time. In this work, rGO-CuS composite was synthesized by one-pot hydrothermal method and used for electrode modification. The electrochemical and ECL behaviors of the sensor were investigated. More than 5-fold enhance in ECL intensity was observed after modified with rGO-CuS composite. The results can be ascribed to the presence of rGO-CuS composite on the electrode surface that facilitates the electron transfer rate between the electroactive center of Ru(bpy)3(2+) and the electrode. The ECL sensor was coupled with CE to improve the selectivity and the CE-ECL parameters that affect separation and detection were optimized. Under the optimum conditions, the linear ranges for AML was 0.008-5.0µg/mL with a detection limit of 2.8ng/mL (S/N=3). The method displayed the advantages of high sensitivity, good selectivity, wide linear range, low detection limit and fine reproducibility, and was used to analyze AML in mice plasma with a satisfactory result, which holds a great potential in the field of pharmaceutical analysis.