Electroanalysis and simultaneous determination of dopamine and epinephrine at poly(isonicotinic acid)-modified carbon paste electrode in the presence of ascorbic acid

A carbon paste electrode modified with electropolymerized fills of isonicotinic acid was developed. The modified electrode shows excellent electrocatalytic activity toward the oxidation of both dopamine （DA） and epinephrine （EP）. Separation of the reduction peak potentials for dopamine and epinephrine was about 357 mV in pH 5.3 phosphate buffer solution （PBS） and the character was used for the detection DA and EP simultaneously. The peak currents increase linearly with DA and EP concentration over the range of 8.0×10^-5 to 7.0×10^-4 mol/L and 5.0×10^-6 to 1.0×10^-4 mol/L with detection limits of 2×10^-5 and 1×10^-6 mol/L, respectively. The interference studies showed that the modified electrode exhibits excellent selectivity in the presence of large excess of ascorbic acid （AA）.

Development of RP-HPLC method for simultaneous determination of docetaxel and curcumin in rat plasma: Validation and stability

The purpose of the present research was to develop a suitable, simple, precise, accurate,robust, and reproducible RP-HPLC method for a reliable simultaneous quantification of docetaxel(DTX) and curcumin(CCM) in rat plasma samples using paclitaxel(PTX) as an internal standard. The samples were assayed by the Agilent 1260 Infinity HPLC instrument using a Capcell Pak C8 column(4.6 mm × 150 mm, 5 μm) under isocratic conditions. The mobile phase consisted of acetonitrile and triple distilled water(40/60, v/v) with a flow rate of 1.0 ml/min. The eluent was monitored at 230 nm for simultaneous measurement of curcumin and docetaxel. The method was validated by determining system suitability, selectivity, sensitivity, linearity, inter-day and intra-day precision, accuracy, robustness, and stability in accordance with the guidelines of the United States Food and Drug Administration(FDA).The developed chromatographic method proved to be simple, precise, accurate, robust and reproducible. Moreover, the samples showed stability at room temperature over a period of 48 h. Thus, this method would be employed for routine simultaneous quantification of docetaxel and curcumin in rat plasma samples.

Highly sensitive simultaneous electrochemical determination of myricetin and rutin via solid phase extraction on a ternary Pt@r-GO@MWCNTs nanocomposite

The simultaneous electrochemical determination of myricetin and rutin remains a challenge due to their indistinguishable potentials.To solve this problem,we constructed a ternary platinum nanoparticle,reduced graphene oxide,multi-walled carbon nanotubes (Pt@r-GO@MWCNTs) nanocomposite via a facile one-pot synthetic method.Under the optimized conditions,the ternary Pt@r-GO@MWCNTs nanocomposite exhibited good electrocatalytic activity toward myricetin and rutin via solid phase extraction and excellent performance for the simultaneous determination of myricetin and rutin.The oxidation peak current of myricetin was proportional to its concentrations in the range of 0.05-50μM with a detection limit of 0.01μM (S/N=3).The linear range for rutin was 0.05-50μM with a detection limit of 0.005μM(S/N=3).The ternary nanocomposite sensor also exhibited good reproducibility and stability,and was successfully used for the simultaneous determination of myricetin and rutin in real orange juice samples with recoveries ranging between 100.57% and 108.46%.

Reagent optimization for on-line simultaneous polarographic determination of trace amounts of Cu^(2+), Cd^(2+) and Co^(2+) in the presence of anextremely large excess of Zn^(2+)

Reagents are optimized for the simultaneous determination of trace amounts of Cu^(2+), Cd^(2+) and Co^(2+) in zinc sulfate solution, which contains an extremely large excess of Zn^(2+). First, the reagents and their doses for the experiment are selected according to the characteristics of the zinc sulfate solution. Then, the reagent doses are optimized by analyzing the influence of reagent dose on the polarographic parameters(i.e. half-wave potential E_(1/2) and limiting diffusion current I_p). Finally, the optimization results are verified by simultaneously determining trace amounts of Cu^(2+), Cd^(2+) and Co^(2+) in the presence of an extremely large excess of Zn^(2+). The determination results indicate that the optimized reagents exhibit wide linearity, low detection limits, high accuracy and good precision for the simultaneous determination of trace amounts of Cu^(2+), Cd^(2+) and Co^(2+) in the presence of an extremely large excess of Zn^(2+).

Simultaneous Determination of Calcium and Magnesium in Water Using Artificial Neural Network Spectro-Photometric Method

A new analytical method using Back-Propagation （BP） artificial neural networks and spectrophotometry for simultaneous determination of calcium and magnesium in tap water, the Yellow River water and seawater is established. By condition experiment, the optimum analytical conditions for calcium, magnesium and Arsenazo （Ⅲ） color reactions are obtained. Levenberg- Marquart （L-M） algorithm is used for calculation in BP neural network. The topological structure of three-layer BP ANN network architecture is chosen as 11-10-2 （nodes）. The initial value of gradient coefficient μ is fixed at 0.001 and the increase factor and reduction factor of kt take the default values of the system. The data are processed by computers with our own programs written in MATLAB 7.0. The relative standard deviations of the calculated results for calcium and magnesium are 2.31% and 2.14%, respectively. The results of standard addition method show that the recoveries of calcium and magnesium are 103.6% and 100.8% in the tap water, 103.2% and 96.6% in the Yellow River water （Lijin district of Shandong Province）, and 98.8%-103.3% and 98.43%-103.4% in seawater from Jiaozhou Bay of Qingdao. It is found that 14 common cations and anions do not interfere with the determination of calcium and magnesium under the optimum experimental conditions. The comparative experiments do not show any obvious differ- ence between the results obtained by this new method and those obtained by the classical complexometric titration method in seawater medium. This method exhibits good reproducibility and high accuracy in the determination of calcium and magnesium and can be used for the simultaneous determination of Ca^2＋ and Mg^2＋ in tap water and natural water.

2,3-Dimercaptosuccinic acid self-assembled gold electrode for the simultaneous determination of epinephrine and dopamine

Simultaneous determination of epinephrine （EP） and dopamine （DA） at 2,3-dimercaptosuccinic acid （DMSA） modified electrode was studied. The oxidation peaks of the mixture of EP and DA appeared at the same potential, but the cathodic peak currents were only linear to the concentration of DA, whereas the anodic peak currents were equal to the sum of individual anodic peak currents of EP and DA. Therefore, a novel electrochemical method for the simultaneous determination of EP and DA at a DMSA modified electrode （DMSA/Au electrode） by cyclic voltammetry was established. The DMSA self-assembled electrode showed good sensitivity, selectivity and stability and could be used to determine DA and EP, simultaneously, in the real application with satisfactory results.

Simultaneous Determination of Iron and Manganese in Water Using Artificial Neural Network Catalytic Spectrophotometric Method

A new analytical method using Back-Propagation (BP) artificial neural network and kinetic spectrophotometry for simultaneous determination of iron and magnesium in tap water, the Yellow River water and seawater is established. By conditional experiments, the optimum analytical conditions and parameters are obtained. Levenberg-Marquart (L-M) algorithm is used for calculation in BP neural network. The topological structure of three-layer BP ANN network architecture is chosen as 15-16-2 (nodes). The initial value of gradient coefficient μ is fixed at 0.001 and the increase factor and reduction factor of μ take the default values of the system. The data are processed by computers with our own programs written in MATLAB 7.0. The relative standard deviation of the calculated results for iron and manganese is 2.30% and 2.67% respectively. The results of standard addition method show that for the tap water, the recoveries of iron and manganese are in the ranges of 98.0%-104.3% and 96.5%-104.5%, and the RSD is in the range of 0.23%-0.98%; for the Yellow River water (Lijin district of Shandong Province), the recoveries of iron and manganese are in the ranges of 96.0%-101.0% and 98.7%-104.2%, and the RSD is in the range of 0.13%-2.52%; for the seawater in Qingdao offshore, the recoveries of iron and manganese are in the ranges of 95.3%-104.8% and 95.3%-104.7%, and the RSD is in the range of 0.14%-2.66%. It is found that 21 common cations and anions do not interfere with the determination of iron and manganese under the optimum experimental conditions. This method exhibits good reproducibility and high accuracy in the determination of iron and manganese and can be used for the simultaneous determination of iron and manganese in tap water and natural water. By using the established ANN- catalytic spectrophotometric method, the iron and manganese concentrations of the surface seawater at 11 sites in Qingdao offshore are determined and the level distribution maps of iron and manganese are drawn.

Simultaneous Determination of Gold and Platinum by Double Artificial Neural Network Analysis with Flow-injection Chemiluminescence

A highly sensitive double artificial neural network （DANN） analysis with flow-injection chemiluminescence （FI-CL） has been developed to simultaneously determine the trace amounts of the gold and platinum in simulated mixed samples, without the boring process.

Application and verification of simultaneous determination of cellulose δ^(13)C and δ^(18)O in Picea shrenkiana tree rings from northwestern China using the high-temperature pyrolysis method

Stable isotopes in tree-ring cellulose provide important data in ecological,archaeological,and paleoenvironmental researches,thereby,the demand for stable isotope analyses is increasing rapidly.Simultaneous measurement of cellulose δC and δO values from tree rings would reduce the cost of isotopic commodities and improve the analytical efficiency compared with conventional separate measurement.In this study,we compared the δC and δO values of tree-ringα-cellulose from Tianshan spruce(Picea schrenkiana)in an arid site in the drainage basin of the Urumqi River in Xinjiang of northwestern China based on separate and simultaneous measurements,using the combustion method(at1050°C)and the high-temperature pyrolysis method(at 1350°C and 1400°C).We verified the results of simultaneous measurement using the outputs from separate measurement and found that both methods(separate and simultaneous)produced similar δC values.The two-point calibrated method improved the results(range and variation)of δC and δO values.The mean values,standard deviations,and trends of the tree-ring δC obtained by the combustion method were similar to those by the pyrolysis method followed by two-point calibration.The simultaneously measured δO from the pyrolysis method at 1400°C had a nearly constant offset with that the pyrolysis method at 1350°C due to isotopic-dependence on the reaction temperature.However,they showed similar variations in the time series.The climate responses inferred from simultaneously and separately measured δC and δO did not differ between the two methods.The tree-ring δC and δO values were negatively correlated with standardized precipitation evapotranspiration index from May to August.In addition,the δO was significantly correlated with temperature(positive),precipitation(negative),and relative humidity(negative)from May to August.The tree-ring δC and δO values determined simultaneously through the high-temperature pyrolysis method could produce acceptable and reliable stable isotope series.The simultaneous isotopic measurement can greatly reduce the cost and time requirement compared with the separate isotopic measurement.These results are consistent with the previous studies at humid sites,suggesting that the simultaneous determination of δC and δO in tree-ringα-cellulose can be used in wide regions.

Simultaneous Determination of Bisphenols and Alkylphenols in Water by Solid Phase Extraction and Ultra Performance Liquid Chromatography-tandem Mass Spectrometry

To establish an analytical method for determination of four bisphenols （BPA, BPB, BPF, and BPS） and two alkylphenols （4-n-OP, 4-n-NP） in water by ultra performance liquid chromatography- tandem mass spectrometry （UPLC/MS/MS）. The water samples were extracted and condensed with solid-phase extraction （SPE） using C18 cartridges and eluted by acetonitrile. Separation was carried out with Acquity BEH C8 column and detection were performed by UPLC/MS/MS. Quantification was calculated by using the internal standard BPA-d16 and 4-n-NP-d8. The linear correlation coefficients of these compounds in the range of 1.0-100.0μg/L were all over 0.999. The minimum detectable concentrations were 0.75-1.0 ng/L, and the recoveries ranged from 87.0% to 106.9%.

Simultaneous Spectrophotometric Determination of Three Components Including Deoxyschizandrin by Partial Least Squares Regression

The computer auxiliary partial least squares is introduced to simultaneously determine the contents of Deoxyschizandin, Schisandrin, r-Schisandrin in the extracted solution of wuweizi. Regression analysis of the experimental results shows that the average recovery of each component is all in the range from 98.9% to 110.3% , which means the partial least squares regression spectrophotometry can circumvent the overlappirtg of absorption spectrums of mlulti-components, so that sctisfactory results can be obtained without any scrapple pre-separation.

Simultaneous Determination of Six Constituents in Cangbaiqutong Capsule by HPLC Wavelength Switching Technique

[Objectives] To establish a high performance liquid chromatography (HPLC) wavelength switching method for the simultaneous determination of content of six constituents (phellodendrine chloride, gentiopicrin, paeoniflorin, tetrandrine, berberine hydrochloride and paeonol) in Cangbaiqutong capsules, and provide a scientific basis for the comprehensive evaluation of the quality of Cangbaiqutong capsule.[Methods] The chromatographic column of Waters XSELECT CSH-C 18 (4.6 mm × 150 mm, 5 μm), the mobile phase of acetonitrile-0.1% phosphate solution, gradient elution (0-15 min,10%-18% A;15-30 min,18%-50% A;30-35 min, 50%-10% A);the flow rate of 1.0 mL/min, wavelength switching of 284 (0-7 min, phellodendrine), 274 (7-10 min, gentiopicrin), 230 (10-14 min, paeoniflorin) and 274 nm (14-35 min, tetrandrine, berberine hydrochloride, paeonol), the injection volume of 10 μL.[Results] There was a good linear relationship between the area of chromatographic peak and the injection volume of phellodendrine chloride, gentiopicrin, paeoniflorin, tetrandrine, berberine hydrochloride and paeonol in the range of 0.150-1.504, 0.768-7.680, 1.096-10.960, 0.220-2.200, 0.296-2.956, 0.0345-0.345 μg, respectively;the average recovery rates ( n =6) were 98.3%, 99.2%, 98.8%, 98.8%, 99.1% and 98.2%, respectively;the RSD value was 1.32%, 1.46%, 1.08%, 1.31%, 1.26% and 1.21%, respectively.[Conclusions] The method can be used to determine many kinds of constituents at the same time, and the operation is simple, accurate and reproducible, and can be used for the quality control of compound Cangbaiqutong capsules.

Nitrogen-doped carbon@TiO_(2) double-shelled hollow spheres as an electrochemical sensor for simultaneous determination of dopamine and paracetamol in human serum and saliva

As the most commonly used antipyretic and analgesic drug,paracetamol(PA)coexists with neurotransmitter dopamine(DA)in real biological samples.Their simultaneous determination is extremely important for human health,but they also interfere with each other.In order to improve the conductivity,adsorption affinity,sensitivity,and selectivity of TiO_(2)-based electrochemical sensor,N-doped carbon@-TiO_(2) double-shelled hollow sphere(HeC/N@TiO_(2))is designed and synthesized by simple alcoholic and hydrothermal method,using polystyrene sphere(PS)as a template.Meanwhile,TiO_(2) hollow spheres(H eTiO_(2))or N-doped carbon hollow spheres(HeC/N)are also prepared by the same method.HeC/N@TiO_(2) has good conductivity,charge separation,and the highly enhanced and stable current responses for the detection of PA and DA.The detection limit and linear range are 50.0 nmol/L and 0.3-50 mmol/L for PA,40.0 nmol/L and 0.3e50 mmol/L for DA,respectively,which are better than those of carbon-based sensors.Moreover,this electrochemical sensor,with high selectivity,strong anti-interference,high reliability,and long time durability,can be used for the simultaneous detection of PA and DA in human blood serum and saliva.The high electrochemical performance of HeC/N@TiO_(2) is attributed to the multifunctional combination of different layers,because of good conductivity,absorption and electrons transfer ability from in-situ N-doped carbon and electrocatalytic activity from TiO_(2).

A Novel Sample Introduction Technique for the Simultaneous Determination of As,Se,Ge and Hg in Chinese Medicinal Material

A novel technique of Moveable Reduction Bed Hydride Generator（MRBHG）was applied tohe hydride generation or cold vapor generation of As，Se，Ge，and Hg existing In TraditionalChinese Medicinal Material（TCM）．The simultaneous determination of the multi－elements wasperformed with ICP－MS．A solid reduction system involving the use of potassiumtetraborohydride and tartaric acid was applied to generating metal hydride or cold vaporefficiently．The factors affecting the metal cold vapor generation were studied．The mainadvantage of the technique is that only a 4μL volume of sample was required for the cold vapor

Simultaneous determination of borneol and its metabolite in rat plasma by GC-MS and its application to pharmacokinetic study

A gas chromatography mass spectrometry （GC-MS） method has been developed and fully validated for the simultaneous determination of natural borneol （NB） and its metabolite, camphor, in rat plasma. Following a single liquid-liquid extraction, the analytes were separated using an HP-5MS capillary column （0.25 mm ？ 30 m ？ 0.25μm） and analyzed by MS in the selected ion monitoring mode. Selected ion monitor （m/z） of borneol, camphor and internal standard was 95, 95 and 128, respectively. Linearity, accuracy, precision and extraction recovery of the analytes were all satisfactory. The method was successfully applied to pharmacokinetic studies of NB after oral administration to Wistar rats.

Simultaneous colorimetric determination of morphine and ibuprofen based on the aggregation of gold nanoparticles using partial least square

In this work a new method is presented for simultaneous colorimetric determination of morphine （MOR） and ibuprofen （IBU） based on the aggregation of citrate-capped gold nanoparticles （AuNPs）. Citrate-capped AuNPs were aggregated in the presence of MOR and IBU. The difference in kinetics of AuNPs aggregation in the presence of MOR/IBU was used for simultaneous analysis of MOR and IBU. The formation and size of synthesized AuNPs and the aggregated forms were monitored by infra-red （IR） spectroscopy and transmission electron microscopy （TEM）, respectively. By adding MOR or IBU the absorbance was decreased at 520 nm and increased at 620 nm. The difference in kinetic profiles of aggregation was applied for simultaneous analysis of MOR and IBU using partial least square （PLS） regression as an efficient multivariate calibration method. The number of PLS latent variables was optimized by leave-one-out cross-validation method using predicted residual error sum of square. The proposed model exhibited a high capability in simultaneous prediction of MOR and IBU concentrations in real samples. The results showed linear ranges of 1.33-33.29 μg/mL （R2=0.9904） and 0.28-6.9 μg/mL （R2=0.9902） for MOR and IBU respectively with low detection limits of 0.15 and 0.03 μg/mL（S/N=5）.

SIMULTANEOUS DETERMINATION OF FLUORINE AND CHLORINE IN WATER WITH DOUBLE INDICATIVE ELECTRODES

The new method for simultaneous determination of the concentrations of fluorine and chlorine in river water with double indicative electrodes is developed, and the quantitative analysis formulas that the inputs of electrode were exchanged by using self-made joints were induced. With this method,the synthetic water samples and the water samples taken from Majiagou River were analyzed. The results of determinations are satisfactory. The relative errors were<10.0% for F and <3.0%for Cl. The recoveries werc 90-101% for F and 90-110% tbr Cl. The relative standard deviations were < 15.2% for F and < 10.1% for Cl-. The advantages of this method is accurate, rapid and simple.

Recent Development in Simultaneous Multi-Element Determination of the Platinum Group Elements and Gold in Geological and Environmental Samples

In recent years, the modern methods of multi-element analysis of precious metals have attracted wide attention in scientific research and industry. The application and development in the decomposition of samples, separation and enrichment, and modern instrumental analysis of the platinum-group elements (PGEs) and gold in geological and environmental samples have been reviewed. Finally, the tendency of analysis of precious metals is also prospected.

New Time-resolved-Tween 80 Chemiluminescent System for Simultaneous Determination of Trace Gold and Osmium

A time resolved chemiluminescent analysis for simultaneous determination of trace Au(Ⅲ) and Os(Ⅳ) was proposed. The method is based on the kinetic distinction of Au(Ⅲ) and Os(Ⅳ) in Tween 80 KOH chemilumescent system. The detection limits were 1.1×10 -9 g/ml for Au(Ⅲ) and 1.0×10 -8 g/ml for Os(Ⅳ), with the linear ranges of 1.0×10 -8 ～1.0×10 -5 g/ml for Au(Ⅲ) and 1.0×10 -7 ～1.0×10 -6 g/ml for Os(Ⅳ). The method was applied to the determination of Au(Ⅲ) and Os(Ⅳ) in the sample of metallurgical materials of noble metals with satisfactory results.

Simultaneous Spectrophotometric Determination of Four Components including Acetaminophen by Taget Factor Analysis

UV Spectrophotometric Target Factor Analysis （TFA） was used for the simultaneous determination of four components （acetaminophen, guuaifenesin, caffeine, Chlorphenamine maleate） in cough syrup. The computer Frogram of TFA is based on VC＋＋ language. The difficulty of overlapping of absorption spectra of four compounds was overcome by this procedure. The experimental results show that the average recovery of each component is all in the range from 98.9% to 106.8% and each component obtains satisfactory results without any pre-separation.