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）.

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%.

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 Determination of Uranium and Thorium with Standard Dual-addition Method

dual-standard addition method was proposed and the principle of simultaneous determination for a interfering binary mixtures was discussed. The proposed procedure was applied to spectroscopic analyses for the simultaneous determination of uranium and thorium without prior separation. Various molar ratios of uranium/thorium, from 0.5∶1 to 10∶1, can be determined with satisfactory precision and accuracy. Uranium and thorium content in a phosphate ore and simulated sample were determined, the recoveries were 98.4%～102.5% for uranium and 96.8%～102.3% for thorium, the relative standard deviations (R.S.D) were 1.5%～2.3% for uranium and 2.1%～3.1% for thorium.

Investigati on sonsimultaneous determination of silver and mercury in catalytic－ligandsub stitution reaction with stopped－flow technique calibrated by synergistic effect

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Kinetic Investigation of Ce,Y-CPAmA Systems and Simultaneous Determination of Sc,Y,Ce via Complementary Tristimulus Spectrophotometry

In the past ten years the eomplementary tristimulus speetrophotometryll],eTs,has seen its diverse appli-eations{2一61 though most researehes remain in relatively simpe systems,and less work has been involvinkinetie reaetions. An attemPt has been made on the investigation of some comPlieated systems eontainingrare earths and meta一acetylchloroPhosPhonaz

The Simultaneous Determination of Cu Ph Cd and Sb by Derivative Adsorption Chronopotentiometry

The behaviour of the complexes of copper,lead,cadmium and antimony with salicylfluorone (SAF) adsorbed on HMDE has been investigated by derivative chronopotentiometry in NH_3/NH_4C1. The dependence of the peak height on the dt/dE vs E curve on preconcentration time, the pH of solution and the constant reducing current are discussed. This method achieved the simultaneous determination of copper, lead, cadmium and antimony in human hair.

Simultaneous Determination of PIP and POP in Seawater

A method for simultaneous determination of particulate inorganic phosphorus (PIP) and particulate organic phosphorus (POP) in seawater was improved. After using cellulose acetate membrane to filter the seawater samples and washing the membrane with 1mol/L hydrochloric acid, PIP was extracted into hydrochloric acid phase and POP was left on the membrane. POP was oxygenated at 120℃, 0.12MPa with potassium persulphate. Phosphomolybdate blue spectrophotometry was used in the determination. The proper volume of seawater sample for simultaneously determining PIP and POP was 100-150ml, containing PIP≥0.27μg, POP≥0.69μg. Relative Standard Deviation (RSD) of the determination of PIP and POP was 5.8% and 4.3% respectively. This method was used to determine POP and PIP in the surface water of Huiquan Bay, Qingdao, China. PIP content there averaged at 69.0μg/L and POP at 3.3μg/L. PIP is the main form (>93%) of particulate phosphorus (PP). Maximum PIP coincided with flood tide, indicating that PIP mainly originated from disturbance of surface sediments. At the offshore area, maximum of PIP appeared at flood tide and minimum of PIP appeared at ebb-tide. The maximum of POP presented at about 10:00am, which suggests that POP is closely related to biological metabolism. The control factor of POP in seawater was concluded to be biological metabolization.

SIMULTANEOUS DETERMINATION OF VITAMIN B COMPLEX (THIAMINE, RIBOFLAVIN, NIACIN, PYRIDOXINE AND FOLIC ACID) IN FOODS BY HPLC

A high performance liquid chromatographic assay has been developed for the simultaneous determination of five water soluble vitamins:thimine, riboflavin, niacin, pyridoxine and folic acid in cereal products and fresh vegetables. Food samples were hydrolyzed in 0.4 mol/L HCl, autoclaved at 120℃ 15 psi for 20 minutes, using a μ-Bondapak column (3.9×300mm, Waters Co.), a mobile phase of methanol-water (30:70) (0.005 mol/L heptanesulfonic acid) and a flow rate of 1.0 ml/min gave the most satisfactory separation of the five water soluble vitamins. A double channel deteetion was used: four vitamins (B_5, folic acid, B_2, B_1) were detected hy UV spectrophotometry (254 nm) first, pyridoxine (B_6) was detected by fluoromelry (EX 290nm, EM 395 nm) afterwards. Detection limits were 2, 5, 5, 2and 5ng, linear ranges were 5-10ng, 5-50ng, 5-40ng, 5-50ng and 10-50ng for B_1, B_2, B_5, B_6 and folic acid respectively. Recoveries were 92-100%(B_5), 51-52% (folio acid), 103—105% (B_2), 99—100% (B_6) and 91.3—102% (B_1) respectively. In comparison with a reference method and checking with food composition tables, very satisfactory results were obtained by this method.

SIMULTANEOUS DETERMINATION OF EPHEDRINE AND ITS ANALOGUES IN URINE BY CAPILLARY GAS CHROMATOGRAPHY

A method is developed for the simultaneous determination of ephedrine,pseudoephedrine, norephedrine, norpseudoephedrine and methylephedrine in urine on a capillary column using nitrogen-phosphorus detector.Diphenylamine is used as the internal standard.Calibration graphs are linear down to 1.30ug/ml urine.

SIMULTANEOUS DETERMINATION OF MULTICOMPONENT IN MIXED ACIDS BY MATHEMATICAL METHOD

A new method for the determination of components in mixed acids has been developed.The mathematical model is obtained from samples of known composition and is then used to predict the concentrations of components in unknown sample.The practical utility of this method is demonstrated for simultaneous determination of two systems of ternary mixed acids and the results are satisfactory.

SIMULTANEOUS DETERMINATION OF FAT SOLUBLE VITAMINS A, D_3, E AND K_1 IN FORTIFIED MILK POWDERS BY HPLC

A high performance liquid chromatographic method for the simultaneous determination of four fat soluble vitamins: retinol (vitamin A), cholecalciferol(vitamin D), tocopherol(vitamin E) and phylloquinone(vitamin K_1) in fortified milk powders and egg yolk has been developed. The method requires enzymatic hydrolysis of lipid component of the sample as a pretreatment. Several factors which influence the enzymatic hydrolysis were studied-Separation was achieved using μ-Bondapak C-18 column(3.9×300mm), 98% methanol as mobile phase, a double channel detection was selected; vitamins D_3 E_1 K_1 were detected by UV spectrophotometry (265 nm) first, then vitamin A by fluorometry (EX 325nm, EM 480mm). The retention times of vitamin A_1 D_3, E and K_1 4.87, 9.00, 10.58 and 15.45 min respectively. Detection limit were 0.64, 0.25, 0.50 and 0.07 ng; and the recoveries were 90.5%～103.6% 90.0%～95.6%, 91.7%～98.8%, 91.5%～98.6%, respectively. The vitamins A, D_0, E, K_1 contents in foods were determined satisfactorily.

SIMULTANEOUS DETERMINATION OF NEODYMIUM AND PRASEODYMIUM BY ZERO-ORDER AND FOURTH-ORDER DFRIVATIVE SPECTROPHOTOMETRY

With derivative spectrophotometric method,the complexes of lanthanides with 2-(5-bromo-2-pyridylazo)-5-diethylaminophen- ol(5-Br-PADAP)in the presence of octylphenol poly(ethyleneg- lycol)ether(TX-100)were studied.It is found that the maximum absorption of fourth-order derivative spectra of the neodymium complex by 4f electron transitions is at 579(+)nm and 582(-)nm with molar derivative absorptivities of 5.2×10~3 1.mol^(-1).cm^(-1). The maximum absorption of the zero-order derivative spectra of the complexes for neodymium and praseodymium is at 580hm,the molar absorptivities are 1.47×10~5 l.mol^(-1).cm^(-1)for Nd and 1.26 ×10~5 l.mol^(-1).cm^(-1)for Pr.The component ratio of the complex is Nd:5-Br-PADAP=1:4.Beer's law is obeyed in the range of 0-3.75μg of Nd and Pr in 25ml of solution.The method has been used for the simultaneous determination of Nd and Pr in four synthetic samples and the results obtained are satisfactory.