Facile separation and determination of Aconitine alkaloids in traditional Chinese medicines by CE with tris(2,2 '-bipyridyl) ruthenium(II)-based electrochemi-luminescence detection

A facile CE method coupled with tris(2,2'-bipyridyl) ruthenium(ll)-based electrochem iluminescence [Ru(bpy)(3)(2+)] detection was developed for simultaneous determination of Aconitum alkaloids, i.e., hypaconitine (HA), aconitine (AC), and mesaconitine (MA) in baseline separation. The optimal separation of these Aconitum alkaloids was achieved in a fused-silica capillary column (50 cm x 25 mu m id) with 30 mM phosphate solution (pH 8.40) as running buffer at 12 kV applied voltage. The three alkaloids can be determined within 10 min by a single run. The calibration curves showed a linear range from 2.0 x 10(-7) to 2.0 x 10(-5) M for HA, 3.4 x 10(-7) to 1.7 x 10(-5) M for AC, and 3.8 x 10(-7) to 1.9 x 10(-5) M for MA. The RSDs; for all analytes were below 3.01%. Good linear relationships were found with correlation coefficients for all analytes exceeding 0.993. The detection limits were 2.0 x 10(-8) M for HA, 1.7 x 10(-7) M for AC, and 1.9 x 10(-7) M for MA under optimal conditions. This method was successfully applied to determine the three alkaloids in Aconitum plants.

Field-amplified sample stacking capillary electrophoresis with electrochemiluminescence applied to the determination of illicit drugs on banknotes

Capillary electrophoresis (CE) with Ru(bpy)(3)(2+) electrochemiluminescence. (ECL) detection system was established to the determination of contamination of banknotes with controlled drugs and a high efficiency on-column field-amplified sample stacking (FASS) technique was also optimized to increase the ECL intensity. The method was illustrated using heroin and cocaine, which are two typical and popular illicit drugs. Highest sample stacking was obtained when 0.01 mM acetic acid was chosen for sample dissolution with electrokinetical injection for 6 s at 17 kV. Under the optimized conditions: ECL detection at 1.2 V, separation voltage 10.0 kV, 20 mM phosphate-acetate (pH 7.2) as running buffer, 5 mM Ru(bpy)(3)(2+) with 50 mM phosphate-acetate (pH 7.2) in the detection cell, the standard curves were linear in the range of 7.50 x 10(-8) to 1.00 x 10(-5) M for heroin and 2.50 x 10(-7) to 1.00 x 10(-4) M for cocaine and detection limits of 50 nM for heroin and 60 nM for cocaine were achieved (S/N = 3), respectively. Relative standard derivations of the ECL intensity and the migration time were 3.50 and 0.51% for heroin and 4.44 and 0.12% for cocaine, respectively.The developed method was successfully applied to the determination of heroin and cocaine on illicit drug contaminated banknotes without any damage of the paper currency.

Determination of ranitidine in urine by capillary electrophoresis-electrochemiluminescent detection

The fast analysis of ranitidine is of clinical importance in understanding its efficiency and a patient's treatment history. In this paper, a novel determination method for ranitidine based on capillary electrophoresis-electrochemiluminescence detection is described. The conditions affecting separation and detection were investigated in detail. End-column detection of ranitidine in 5 mM Ru(bpy)(3)(2+) solution at applied voltage of 1.20 V was performed. Favorable ECL intensity with higher column efficiency was achieved by electrokinetic injection for 10 s at 10 kV. The R.S.D. values of ECL intensity and migration time were 6.38 and 1.84% for 10(-4) M and 6.01 and 0.60% for 10(-5) M, respectively. A detection limit of 7 x 10(-8) M (S/N = 3) was achieved. The proposed method was applied satisfactorily to the determination of ranitidine in urine in 6 min.

Determination of Hg(II) in waters by on-line preconcentration using Cyanex 923 as a sorbent - Cold vapor atomic absorption spectrometry

Using a solid phase extraction mini-column home-made from a neutral extractant Cyanex 923, inorganic Hg could be on-line preconcentrated and simultaneously separated from methyl mercury. The preconcentrated Hg (11) was then eluted with 10% HNO3 and subsequently reduced by NaBH4 to form Hg vapor before determination by cold vapor atomic absorption spectrometry (CVAAS). Optimal conditions for and interferences on the Hg preconcentration and measurement were at 1% HCl, for a 25 mL sample uptake volume and a 10 mL min(-1) sample loading rate. The detection limit was 0.2 ng L-1 and much lower than that of conventional method (around 15.8 ng L-1). The relative standard deviation (RSD) is 1.8% for measurements of 40 ng L-1 of Hg and the linear working curve is from 20 to 2000 ng L-1 (with a correlation coefficient of 0.9996). The method was applied in determination of inorganic Hg in city lake and deep well water (from Changchun, Jilin, China), and recovery test results for both samples were satisfactory.

Determination of total calcium in plasma by flow injection analysis with tris(2,2 '-bipyridyl)ruthenium(II) electrochemiluminescent detection

We described here a new method for the determination of total calcium in plasma. The method is based on the precipitation of calcium with excess oxalate and the measurement of residual oxalate by flow injection analysis with Ru(bpy)(3)(2+) electrochemiluminescent detection. It has the advantages of extremely stable reagent, user-friendly instrument, high selectivity, good analytical recovery, wide dynamic range, and nice correlation with atomic absorption spectroscopy. The calibration plot for calcium is linear over a concentration range from 0.5 mmol L-1 to 4.8 mmol L-1, which is wider than those obtained by most other methods. The analytical recoveries for plasma calcium are 98.4-101.2% with coefficients of variation (CVs) of 1.96-2.52%. The within-day CVs range from 0.76% to 0.95%, and between-day CVs were from 1.12% to 1.46%. The time for each injection is one minute. Because the proposed method can be readily carried out on increasingly popular instruments for Ru(bpy)(3)(2+) ECL immunoassays and DNA probe assays, Ru(bpy)32+ ECL method is suitable for routine clinical analysis of calcium.

Determination of Nb and Ta in Nb/Ta minerals by inductively coupled plasmas optical emission spectrometry using slurry sample introduction

The determination of Nb and Ta in Nb-Ta minerals was accomplished by slurry nebulization inductively coupled plasma optical emission spectrometry (ICP-OES), using a clog-free V-groove ceramic nebulizer. Samples were first wet-ground to appropriate particle sizes with narrow size distribution and 90% of the particles in the slurry were smaller than 2.32 mu m in diameter. Subsamples were then dispersed in pH 9 aqueous solutions, and agitated in an ultrasonic bath for 15 min prior to analysis. Due to the lack of slurry standards matching well with the samples, calibration was simply carried out using aqueous solution standards. Results were compared with those obtained from a conventional fusion decomposition procedure and acid digestion procedures and a good agreement between the measured and referred values was obtained. The technique provided a good alternative for the rapid determination of Nb and/or Ta in their corresponding minerals.

Determination of ethenzamide and acetoaminophen in quaternary powdered samples by near infrared spectroscopy and searching combination moving window partial least squares algorithm: effects of spectral resolution and signal-to-noise ratio

The present study reports an application of the searching combination moving window partial least squares (SCMWPLS) algorithm to the determination of ethenzamide and acetoaminophen in quaternary powdered samples by near infrared (NIR) spectroscopy. Another purpose of the study was to examine the instrumentation effects of spectral resolution and signal-to-noise ratio of the Buchi NIRLab N-200 FT-NIR spectrometer equipped with an InGaAs detector. The informative spectral intervals of NIR spectra of a series of quaternary powdered mixture samples were first located for ethenzamide and acetoaminophen by use of moving window partial least squares regression (MWPLSR). Then, these located spectral intervals were further optimised by SCMWPLS for subsequent partial least squares (PLS) model development. The improved results are attributed to both the less complex PLS models and to higher accuracy of predicted concentrations of ethenzamide and acetoaminophen in the optimised informative spectral intervals that are featured by NIR bands. At the same time, SCMWPLS is also demonstrated as a viable route for wavelength selection.

Determination of ultra-trace concentrations of elements in high purity tellurium by inductively coupled plasma mass spectrometry after Fe(OH)(3) coprecipitation

In this work, a method was established for the determination of impurities in high purity tellurium by inductively coupled plasma mass spectrometry (ICP-MS) after Fe(OH)(3) coprecipitation. After comparison of coprecipitation ability and separation efficiency between Fe(OH), and Al(OH)(3), Fe(OH)(3) was chosen as the precipitate. A separation factor of 160 for 200 mg tellurium was obtained under conditions of pH 9 and 2 mg of Fe3(+). The 13 elements, such as Bi, Sn, Pb, In, Tl, Cd, Cu, Co, Ni, Zn, Ti, Be and Zr, could be almost completely coprecipitated under these conditions. In addition, Te memory effect imposed on the ICP-MS instrument was assessed, as well as Te matrix effect that caused the low recovery of Ga, As, Sb and V in real sample was discussed. Finally, the method was evaluated through recovery test and was applied to practical sample analysis, with detection limits of most of the elements being below 0.15 mug g(-1) and R.S.D. below or at approximately 10%, which indicated that this method could fully satisfy the requirements for analysis of 99.999% similar to 99.9999% high purity Te.

Simultaneous determination of tramadol and lidocaine in urine by end-column capillary electrophoresis with electrochemiluminescence detection

Tramadol and lidocaine, used as analgesic and local anesthetic in surgery, are partly excreted by kidney. For the first time, we developed a simple and sensitive method, based on capillary electrophoresis with electrochemiluminescence (ECL) detection by end column mode without joint to monitor tramadol and lidocaine in urine. To eliminate the influence of ionic strength of urine sample, analytes were extracted by ether. Tripropylamine (TPA) was used as internal standard. ne recoveries of tramadol and lidocaine were between 94% and 97% at different levels. The method exhibited the linear range for the tramadol and lidocaine from 1.0 X 10(-7) to 1.0 X 10(-4) mol/L with correlation efficient of 0.998. The relative standard deviation (RSD) was 2.9% and 2.7% (n = 8) for tramadol and lidocaine, respectively. The limit of detection (LOD) was 6.0 x 10(-8) mol/L and 4.5 x 10(-8), mol/L (S/N = 3) for tramadol and lidocaine, respectively. The application for detecting tramadol and lidocaine in urine of patients showed that the method was valuable in clinical and biochemical laboratories for detecting tramadol, lidocaine and other tertiary amine pharmaceuticals for various purpose, such as metabolism investigation.

Lipid membrane immobilized horseradish peroxidase biosensor for amperometric determination of hydrogen peroxide

Stable films of didodecyldimethylammonium bromide (DDAB, a synthetic lipid) and horseradish peroxidase (HRP) were made by casting the mixture of the aqueous vesicle of DDAB and HRP onto the glassy carbon (GC) electrode. The direct electron transfer between electrode and HRP immobilized in lipid film has been demonstrated. The lipid films were used to supply a biological environment resembling biomembrane on the surface of the electrode. A pair of redox peaks attributed to the direct redox reaction of HRP were observed in the phosphate buffer solution (pH 5.5). The cathodic peak current increased dramatically while anodic peak decreased by addition of small amount H2O2. The pH effect on amperometric response to H2O2 was studied. The biosensor also exhibited fast response (5 s), good stability and reproducibility.

Determination of biogenic amines by capillary electrophoresis with pulsed amperometric detection

The biogenic amines, putrescine, cadaverine, spermidine and spermine were separated and quantified by capillary electrophoresis with pulsed amperometric detection. Detection potential of the pulsed amperometric detection was optimized as 0.6 V Optimal separation of the biogenic amines was achieved using a separation buffer of 30 mM citrate at pH 3.5, while keeping the buffer in the detection cell as 20 mM NaOH. Using these conditions, the four biogenic amines were baseline separated. Extrapolated limits of detection for putrescine, cadaverime, spermidine and spermine were 400, 200, 100 and 400 nM for the standard mixture (polyamines dissolved in running buffer), respectively. These are lower than ultraviolet detection and comparable or even lower than laser-induced fluorescence detection results as reported in the literature. The number of theoretical plates was maintained at the 105 level, which is absolutely higher than any reported method. When applying capillary electrophoresis-pulsed amperometric detection to milk analysis, only spermidine was found in amounts varying between 0.1 and 0.5 mg/kg.

Determination of diphenhydramine by capillary electrophoresis with tris(2,2 '-bipyridyl)ruthenium(II) electrochemiluminescence detection

Tris(2,2'-bipyridyl)ruthenium(II) electrochemiluminescence detection in a capillary electrophoresis separation system was used for the determination of diphenhydramine. In this study, platinum disk electrode (300 mum in diameter) was used as a working electrode and the influence of applied potential and buffer conditions were investigated. Under optimal conditions: 1.2 V applied potential, pH 8.50, 15 kV separation voltage and 10 mmol l(-1) running buffer, the calibration curve of diphenhydramine was linear over the range of 4 x 10(-8) to 1 x 10(-5) Mol l(-1). This technique gave satisfactory precision, and relative standard deviations of migration times and chemiluminescence peak intensities were less than 1 and 6%, respectively. The technique was applied to animal studies for determination of diphenhydramine extracted from rabbit plasma and urine samples, and the extraction efficiency were between 92 and 98.5%.

Determination of molecular weight and molecular sizes of polymers by high temperature gel permeation chromatography with a static and dynamic laser light scattering detector

Flow-mode static and dynamic laser light scattering (SLS/DLS) studies of polymers, including polystyrene, polyethylene, polypropylene and poly(dimethylsiloxane) (PDMS), in 1,2,4-trichlorobenzene (TCB) at 150 degreesC were performed on a high temperature gel permeation chromatography (GPC) coupled with a SLS/DLS detector. Both absolute molecular weight (M) and molecular sizes (radius of gyration, R-g and hydrodynamic radius, R-h) of polymers eluting from the GPC columns were obtained simultaneously. The conformation of different polymers in TCB at 150 degreesC were discussed according to the scaling relationships between R-g, R-h and M and the rho-ratio (p = R-g/R-h). Flow-mode DLS results of PDMS were verified by batch-mode DLS study of the same sample. The presented technique was proved to be a convenient and quick method to study the shape and conformation of polymers in solution at high temperature. However, the flow-mode DLS was only applicable for high molecular weight polymers with a higher refractive index increment such as PDMS.

Electrochemiluminescent determination of L-cysteine with a flow-injection analysis system

A flow-injection electrochemiluminescent method for L-cysteine determination has been developed based on its enhancement of the electrochemiluminecence of luminol at a glassy carbon electrode. This method is simple and sensitive for cysteine determination. Under the selected experimental parameters, the linear range for cysteine concentration was 1.0 x 10(-6) - 5.0 x 10(-5) mol/l, and the detection limit was 0.67 mumol/l (SIN = 3). The relative standard deviation for 11 measurements of 1.0 x 10(-5) mol/l cysteine was 4.5%. The proposed method has been applied to. the detection of cysteine in pharmaceutical injections with satisfactory results.

Determination of mercury with a flow injection quartz tube atomic absorption spectrometry

A method was developed for the determination of micro mercury in the soil, plants and the traditional Chinese medicine using flow injection quartz tube-atomic absorption spectrometry. The effect of the factors such as acidity,. the carrier solution, the flow rate of reductive solution and argon gas, etc. on the determination was studied. When vanadic oxide, nitric acid and sulfuric acid were used to decompose the sample reliable result could be obtained. The characteristic mass of the method is 59 pg, the detection limit is 0.028 mug/L, RSD is < 3.9% and the recovery is in the range of 94% &SIM; 102%.