Determination of Chromate Ion in Water Using High Performance Capillary Electrophoresis

ThereisarapidIyincreasingdemandforfastandreliableanalyticaImethodsforthedeterminationofchemicaIformsofelementSinenvironmentalsamples.IthaslongbeenknownthatCrfIII)isessentialformammals,however,CrfVI)isconsideredtobeatoxicagent[l].Theanalysisofchromateion(Vl)inenvironmentwaterisusuallyperformedbyusingspephotometryandatomicabsorption,p..tr...ny[2].TheformerneedsfairIylargeamountofsample,pretreatmenLandlonganalysistime.Thelaterequipmentismuchmoreexpensive.InpreviousreportS,chromateisnormaI1…     

Determination of the Deuterium Abundances in Water from 156 to 10,000 ppm by SIFT-MS

In response to a need for the measurement of the deuterium (D) abundance in water and aqueous liquids exceeding those previously recommended when using flowing afterglow mass spectrometry (FA-MS) and selected ion flow tube mass spectrometry (SIFT-MS) (i.e. 1000 parts per million, ppm), we have developed the theory of equilibrium isotopic composition of the product ions on which these analytical methods are based to encompass much higher abundances of D in water up to 10,000 ppm (equivalent to 1%). This has involved an understanding of the number density distributions of the H, D, (16)O, (17)O and (18)O isotopes in the isotopologues of H(3)O(+)(H(2)O)(3) hydrated ions (i.e. H(9)O (4) (+) cluster ions) at mass-to-charge ratios (m/z) of 73, 74 and 75, the relative ion number densities of which represent the basis of FA-MS and SIFT-MS analyses of D abundance. Specifically, an extended theory has been developed that accounts for the inclusion of D atoms in the m/z 75 ions, which increasingly occurs as D abundance in the water is increased, and which is used as a reference signal for the m/z 74 ions in the measurement of D abundance. In order to investigate the efficacy of this theory, experimental measurements of deuterium abundance in standard mixtures were made by the SIFT-MS technique using two similar instruments and the results compared with the theory. It is demonstrated that the parameterization of experimental data can be used to formulate a simple calculation algorithm for real-time SIFT-MS measurements of D abundance to an accuracy of 1% below 1000 ppm and degrades to about 2% at 10,000 ppm.     

Single‐well Potential Stochastic Resonance Applied to Quantitative Analysis for Weak Chromatographic Signals of Sudan IV

Abstract

The single‐well potential stochastic resonance algorithm is applied to enhance signal‐to‐noise ratio of chromatographic signals for trace analysis. Compared with the bistable well potential system, the single‐well simplifies the algorithm since only one system parameter is involved and optimized. Using the signals enhanced by single‐well potential stochastic resonance, the method extended the limit of detection and the limit of quantification of Sudan IV from 0.03 and 0.1 µg/ml to 0.008 and 0.02 µg/ml respectively, and exhibited good linearity, accuracy, and precision, which ensure an accurate determination of the analyte.     

Determination of Volatiles in Water Lily Flowers Using Gas Chromatography–Mass Spectrometry

Volatile organic compounds in the stamens, petals, and pistils of 56 water lily cultivars were determined by headspace solid-phase microextraction coupled with gas chromatography–mass spectrometry. The stamens released a majority of the volatiles. A total of 117 volatile organic compounds were determined. Alkanes and alkenes were the most abundant, followed by aldehydes and ketones. Cluster analysis was used to divide the cultivars into three subsets characterized by specific aromatic compounds and associated aromas. Discriminant analysis confirmed the results of the cluster analysis. Three tropical water lily cultivars Colorata, 34, and Ai Ji Bai and one hardy water lily cultivar Somptuosa had particularly high aromatic compound concentrations and are recommended to produce fragrant, colorful, and hardy specimens.     

Spectrophotometric Determination of Copper in Waste Water Using Liquid–Liquid Extraction in a Flow-Injection System

A flow-injection procedure for the determination of copper in waste water is described. The procedure is based on the formation of an ion-pair between tetrabutylammonium and the tetrathiocyanatocuprate(II) anion. This ion-pair is extracted with chloroform, and the absorbance of the organic phase is measured at 485nm. Concentrations of copper 0.4mg L^–1 can be detected with a linear application range of between 0.5 and 25mg L^–1, a relative standard deviation of 2.3% (0.8mg L^–1, n=10) and a sampling frequency of 30h^–1. Under the proposed working conditions, only Ni(II) and Pd(II) interfere at molar ratios Ni(II)/Cu(II) 50 and Pd(II)/Cu(II) 100.     

GC�CMS and GC�CNPD Determination of Formaldehyde Dimethylhydrazone in Water Using SPME

Formaldehyde dimethylhydrazone (FADMH) is one of the important transformation products of residual rocket fuel 1,1-dimethylhydrazine (1,1-DMH). Thus, recent studies show that FADMH toxicity is comparable to that of undecomposed 1,1-DMH. In this study, a new method for quantification of FADMH in water based on solid phase microextraction (SPME) in combination with gas chromatography (GC) with mass spectrometric (MS) and nitrogen-phosphorus detection (NPD) is presented. Effects of SPME fiber coating type, extraction and desorption temperatures, extraction time, and pH on analyte recovery were studied. The optimized method used 65 micron polydimethylsiloxane/divinylbenzene fiber coating for 1?min headspace extractions at 30?°C. Preferred pH and desorption temperature from the SPME fiber are >8.5 and 200?°C, respectively. Detection limits were estimated to be 1.5 and 0.5?μg?L(-1) for MS and NPD, respectively. The method was applied to laboratory-scale experiments to quantify FADMH. Results indicate applicability for in situ sampling and analysis and possible first-time detection of free FADMH in water.     

Determination of Iron in Tap and Waste Water Using Liquid–Liquid Extraction in a Flow-Injection System

A flow-injection procedure for the determination of iron(III) in water is described. The procedure is based on the formation of an ion pair between the tetraphenylarsonium (Ph₄As⁺) (TPA) or tetrabutylammonium (But₄N⁺) (TBA) cations and the tetrathiocyanatoferrate(III) complex (TTF). This ion pair is extracted with chloroform, and the absorbance of the organic phase is measured at 503nm (for Ph₄As⁺) or 475nm (for But₄N⁺). Iron concentrations higher than 0.9×10^–6molL^–1 (50µgL^–1) can be detected in the first case, with a relative standard deviation of 1.9% (n=12), a linear application rangeof between 1.34 and 54.0×10^–6molL^–1 (75–3015µgL^–1), and a sampling frequency of 30h^–1. For the ion pair with But₄N⁺, the detection limit is 0.52×10^–6molL^–1 (29µgL^–1), with a relative standard deviation of 1.6% and a linear application range between 0.73 and 54.0×10^–6molL^–1. Under the proposed working conditions, only Pd(IV), Cu(II) and Bi(III) interfere. With the application of the merging zones technique, considerable amounts of organic reagent can be saved. The TBA method was applied to the analysis of iron(III) in tap and industrial waste waters.     

Enhancement of Sensitivity for Determination of Phenols in Environmental Water Samples by Single-drop Liquid Phase Microextraction Using Ionic Liquid prior to HPLC

In recent years, single-drop liquid phase microextraction (LPME) has attracted great attentions, and provides some merits including rapidness, simplicity, and low cost. In general, there are two modes of LPME sampling: direct-immersed LPME (DI-LPME) and h…     

Determination of Tetracyclines in Honey Using Liquid Chromatography with Ultraviolet Absorbance Detection and Residue Confirmation by Mass Spectrometry

A determination method has been optimized and validated for the simultaneous analysis of tetracycline （TC）, oxytetracycline （OTC）, chlortetracycline （CTC） and doxycycline （DC） in honey. Tetracyclines （TCs） were removed from honey samples by chelation with metal ions bound to small Chelating Sepharose Fast Flow columns and eluted with Na2EDTA-Mcllvaine pH 4.0 buffers. Extracts were further cleaned up by Oasis HLB solid-phase extraction （SPE）, while other solid-phase extraction cartridges were compared. Chromatographic separation was achieved using a polar end-capped C 18 column with an isocratic mobile phase consisting of oxalic acid, acetonitrile and methanol. LC with ultraviolet absorbance at 355 nm resulted in the quantitation of all four tetracycline residues from honey samples fortified at 15, 50, and 100 ng/g, with liner ranges for tetracyclines of 0.05 to 2 μg/mL. Mean recoveries for tetracyclines were greater than 50% with R.S.D. values less than 10% （n= 18）. Detection limits of 5, 5, 10, 10 ng/g for oxytetracycline, tetracycline, chlortetracycline and doxycycline, respectively and quantitation limits of 15 ng/g for all the four tetracyclines were determined. Direct confirmation of the four residues in honey （2-50 ng/g） was realized by liquid chromatography-tandem mass spectrometry （LC/MS/MS）. The linear ranges of tetracyclines determined by LC/MS/MS were between 5 to 300 ng/mL, with the linear correlation coefficient r〉 0.995. The limits of detection of 1 to 2 ng/g were obtained for the analysis of the TCs in honey.     

Anodic Stripping Voltammetric Determination of Mercury in Water Using a Chitosan‐Modified Carbon Paste Electrode

Abstract

This paper describes the preparation and electrochemical application of a modified carbon paste electrode with chitosan for the determination of Hg(II) ions in water using anodic stripping voltammetry. Experimental parameters, including the pH of the supporting electrolyte, time and potential of accumulation and scan rate were investigated. The best voltammetric response was observed for a paste composition of 60% (m/m) of graphite powder, 20% (m/m) of chitosan and 20% (m/m) of mineral oil, with 0.1 mol/l NaNO₃ solution at pH 6.3 as supporting electrolyte, a preconcentration potential of ?0.2 V, preconcentration time of 270 s and a scan rate of 25 mV/s. Under these optimal experimental conditions, the voltammetric signals were linearly dependent on the Hg(II) concentration in the range of 9.99×10^?7 to 3.85×10^?5 mol/l with a detection limit of 6.28×10^?7 mol/l. Three “spiked” samples of water were evaluated using the proposed sensor, and results agreed with those obtained by a reference method at the 95% confidence level.     

Two-Parameter Stochastic Resonance in a Model of Electrodissolution of Fe in H_2SO_4

IntroductionStochastic resonance (SR) is a nonlinear effect which describes the optimal detection of a weak periodic signal by the action of external noise in nonlinear systems. SR was originally proposed to account for periodicity in the Earth's ice ages1, and it has been observed in a wide range of biological2-4 , physical5 and chemical6 systems. The systems mentioned above which may give rise to SR have a denominator despite many examples of SR in different scientific areas. It is noted…     

Solubility of Succinic Acid in Ethanol Plus Water Systems from 278.15 K to 333.15 K

In an equilibrium vessel, the solubilities of succinic acid in binary aqueous ethanol solvents were measured by the analytical stirred-flask method with the temperature ranging from 278.15 to 333.15 K at atmospheric pressure. Data on the corresponding solid–liquid equilibrium of succinic acid in binary aqueous ethanol solutions are essential for industrial design and further theoretical studies. The effect of solvent composition and temperature on the solubility is discussed. The solubility data were correlated with the Combined Nearly Ideal Binary Solvent/Redlich-Kister (CNIBS/R-K) model. The solubility measured in this study can be used for succinic acid purification or optical resolution by the preferential crystallization procedure.     

Interactions of Night Blue with Nucleic Acids and Determination of Nucleic Acids Using Resonance Light Scattering Technique

The noncovalent interactions of night blue (NB) with several nucleic acids in buffer medium of Britton‐Robinson at pH 4.1 have been studied by spectroscopic methods. It is shown that the binding of NB with nucleic acids involves the J‐aggregation of NB molecules on the surface of nucleic acids. The aggregation was encouraged by polyanions nucleic acids, in which nucleic acids served for acting templates. In this connection, a new method of nucleic acids with sensitivity at nanogram level is proposed based on the measurement of enhanced resonance light scattering (RLS). The linear range of ctDNA, fsDNA and yRNA is 0.01—2.5, 0.03—2.5 and 0.04—1.0 μg/mL, respectively, and the corresponding detection limits (3s?) are 9.4, 7.3 and 5.7 ng/mL at 2.5 × 10–⁵mol/L of NB. Synthetic and real samples were analyzed with satisfactory results.     

Low-Temperature Sorption–Luminescence Determination of Copper in Natural Water Using Silica Gel Chemically Modified with Mercapto Groups

Silica gel with mercaptopropyl groups chemically bonded to its surface extracts copper from solutions with pH 2–9 with a recovery of 99.9%; the sorption equilibration time is no longer than 5 min. Ultraviolet irradiation of wet sorbates cooled to the liquid nitrogen temperature (77 K) generates yellow–orange luminescence (_max = 585 nm), which was used as the analytical signal for the development of a procedure for the low-temperature sorption–luminescence determination of copper. The detection limit is 0.08 g per 0.1 g of the sorbent. The determination of copper is unaffected by the interference from 10⁴-fold amounts of Zn(II), Cd(II), Mn(II), Ni(II), Co(II), Ca(II), Mg(II), and Al(III); 10³-fold amounts of Fe(III); 30-fold amounts of Bi(III); tenfold amounts of Ag(I); and fivefold amounts of Cr(VI). The procedure was used for the determination of copper in natural water.     

Rapid—In—situ Determination of Chromium （VI） in Water Using Modified Diphenylcarbazine with Citrate

In recent years, the determination of Cr (VI) has attracted great attention because of its toxicity to human, plants and animals1-5. Usually, in the industrial waste water, the concentration of Cr (VI) is relatively high and should be determined frequently. So, an accurate, quick, and convenient method for the measurement of Cr (VI) in environmental water, as well as in river, lake, sea and tap water, is of great importance. The method for determination of Cr (VI) by diphenylcarbazine …     

Determination of Milnacipran in Human Plasma Using GC–MS

A new, simple, and fully validated gas chromatography–mass spectrometry (GC–MS) method was presented for quantitative analysis of milnacipran (MNP) in human plasma. MNP was efficiently derivatized with N-methyl-N-trimethylsilyltrifluoroacetamide (MSTFA) before analysis. The role of catalyst, temperature, time, solvent on the trimethylsilylation reaction were evaluated. The proposed method was fully validated by assessment of the following parameters: limits of detection and quantitation, precision, accuracy, linearity, specificity, stability, extraction recovery and robustness/ruggedness. The limit of quantitation (LOQ) was 30 ng mL^?1. The calibration curve was linear (r ² > 0.9988) in the range 30–500 ng mL^?1. The method was found specific, precise, accurate, selective and reliable according to validation data. This developed method was successfully applied to determine the steady state concentration of MNP in patients.     

Preconcentration and Determination of Trace Amounts of Heavy Metals in Water Samples Using Membrane Disk and Flame Atomic Absorption Spectrometry

A fast and simple method for preconcentration of Ni^2＋, Cd^2＋, Pb^2＋, Zn^2＋, Cu^2＋ and Co^2＋ from natural water samples was developed. The metal ions were complexed with sodium diethyldithiocarbamate （Na-DDTC）, then adsorbed onto octadecyl silica membrane disk, recovered and determined by FAAS. Extraction efficiency, influence of sample volume and eluent flow rates, effects of pH, amount of Na-DDTC, nature and amount of eluent for elution of metal ions from membrane disk, break through volume and limit of detection have been evaluated. The effect of foreign ions on the percent recovery of heavy metal ions has also been studied. The limit of detection of the proposed method for Ni^2＋, Cd^2＋, Pb^2＋, Zn^2＋, Cu^2＋ and Co^2＋was found to be 2.03, 0.47, 3.13, 0.44, 1.24 and 2.05 ng·mL^-1, respectively. The proposed （DDTC） method has been successfully applied to the recovery and determination of heavy metal ions in different water samples.     

Determination of Estrone and 17β-Estradiol in Water Samples Using Dispersive Liquid–Liquid Microextraction Followed by LC

A new method, termed dispersive liquid–liquid microextraction (DLLME), was developed for the extraction and pre-concentration of estrone (E1) and 17β-estradiol (E2) in water samples. The samples were extracted by 0.50 mL methanol (disperser solvent) containing 25.0 μL tetrachloroethane (extraction solvent). Important factors such as the volume and type of extraction and disperser solvent, extraction time and salt effect were studied. Under optimum conditions, the enrichment factors and the limits of detection were 347 and 0.2 ng mL^?1 for E1, and 203 and 0.1 ng mL^?1 for E2, respectively. The linear range was 0.5–5,000 ng mL^?1. Compared to other methods, DLLME–LC–VWD has advantages for E1 and E2 analysis in water: high enrichment factor, low cost, simplicity, quick and easy operation.     

Chemoselective Reduction of Azides to Amines Using Sm/TMSCl System in the Presence of Trace Amounts of Water

Samarium diiodide and organosamarium compounds have been widely employed as useful reagents in organic synthesis1. However, relatively few reports on the direct use of samarium metal in organic synthesis have been reported2, because the surface of samarium metal is inactive3. In order to improve the activity of samarium, some additives, such as HgCl24, NH4Cl (aq.)5, or TMSCl6 were added.The reduction of azides to the corresponding amines is an important reaction in organic synthesis7-16. A…     

Determination of Two Pyrethroids in Water Samples by Injection-Ultrasound-Assisted Emulsification Microextraction—High-Performance Thin-Layer Chromatography Using Digital Image Processing

JPC – Journal of Planar Chromatography – Modern TLC -