共查询到20条相似文献,搜索用时 31 毫秒
1.
A chromatographic technique is introduced based on single-walled carbon nanotubes (SWCNTs) as stationary phase for separation of Ar, CO2 and H2 at parts per million (ppm) levels. The efficiency of SWCNTs was compared with solid materials such as molecular sieve, charcoal, multi-walled carbon nanotubes and carbon nanofibers. The morphology of SWCNTs was optimized for maximum adsorption of H2, CO2 and Ar and minimum adsorption of gases such as N2, O2, CO and H2O vapour. To control temperature of the gas chromatography column, peltier cooler was used. Mixtures of Ar, CO2 and H2 were separated according to column temperature program. Relative standard deviation for nine replicate analyses of 0.2 mL H2 containing 10 μL of each Ar or CO2 was 2.5% for Ar, 2.8% for CO2 and 3.6% for H2. The interfering effects of CO, and O2 were investigated. Working ranges were evaluated as 40-600 ppm for Ar, 30-850 ppm for CO2 and 10-1200 ppm for H2. Significant sensitivity, small relative standard deviation (RSD) and acceptable limit of detection (LOD) were obtained for each analyte, showing capability of SWCNTs for gas separation and determination processes. Finally, the method was used to evaluate the contents of CO2 in air sample. 相似文献
2.
Orhan Acar 《Analytica chimica acta》2005,542(2):280-286
Molybdenum, Ir, Ru, Mo-Ir, Mo-Ru thermally coated on to platforms inserted in pyrolytic graphite tubes as permanent modifiers and Pd + Mg(NO3)2 conventional modifier mixture have been employed for the determination of cadmium and lead in dissolved sediments and soil samples by electrothermal atomic absorption spectrometry (ETAAS). Optimum masses and mass ratios of permanent modifiers for the analysis of Cd and Pb in sample solutions have been investigated. The 280 μg of Mo, 200 μg of Ir, 200 μg of Ru, 280 μg of Mo + 200 μg of Ir or 280 μg of Mo + 200 μg of Ru has been found as efficient as 5 μg of Pd + 3 μg of Mg(NO3)2 for increasing thermal stabilization of analytes and for decreasing the most serious interferences. Pyrolysis and atomization temperatures, atomization and background signal shapes, characteristic masses and detection limits of analytes in dissolved samples with or without permanent and conventional modifiers have been compared. The detection limits and characteristic masses obtained with Mo-Ir coated platform are 0.01 μg g−1 and 1.1 pg for Cd and 0.09 μg g−1 and 19 pg for Pb, respectively. Long-term stabilities for analytes in samples with Mo, Mo-Ir, Mo-Ru and Pd + Mg(NO3)2 have been studied. Cadmium and lead contents have been determined in certified and standard reference materials by using optimum conditions investigated and the results obtained with Mo-Ir or Mo-Ru were in agreement with the values of certified reference materials. 相似文献
3.
Orhan Acar 《Analytica chimica acta》2005,545(2):244-251
Permanent modifiers (V, Ir, Ru, V-Ir, V-Ru, and W-V) thermally coated on to platforms of pyrolytic graphite tubes were employed for the determination of Cd, Pb, and Zn in botanic and biological slurries by electrothermal atomic absorption spectrometry (ETAAS). Conventional Pd + Mg(NO3)2 modifier mixture was also used for the determination of analytes in slurries and digested samples. Optimum masses and mass ratios of permanent modifiers for Cd, Pb, and Zn in slurry sample solutions were investigated. The 280 μg of V, 280 μg of V + 200 μg of Ir, 280 μg of V + 200 μg of Ru or 240 μg of W + 280 μg of V in 0.2% (v/v) Triton X-100 plus 0.5% (v/v) HNO3 mixture was found as efficient as 5 μg of Pd + 3 μg of Mg(NO3)2 modifier mixture for obtaining thermal stabilization, and for obtaining best recoveries. Optimization conditions of analytes, such as pyrolysis and atomization temperature, characteristic masses and detection limits, and atomization and background peak profiles were studied with permanent and 5 μg of Pd + 3 μg of Mg(NO3)2 conventional modifiers and compared with each other. The permanent V-Ir, V-Ru, and W-V modifiers remained stable for approximately 250-300 firings when 20 μl of slurries and digested samples were delivered into the atomizer. In addition, the mixed permanent modifiers increase the tube lifetime by 50-95% when compared with untreated platforms. The characteristic masses and detection limits of analytes (dilution factor of 125 ml g−1) obtained with V-Ir based on integrated absorbance as example for 0.8% (m/v) slurries were 1.0 pg and 3 ng g−1 for Cd, 18 pg and 17 ng g−1 for Pb, and 0.7 pg and 4 ng g−1 for Zn, respectively. The results of analytes obtained by employing V-Ir, V-Ru, and W-V permanent modifier mixtures in botanic and biological certified and standard reference materials were in agreement with the certified values of reference materials. 相似文献
4.
Statistical evaluation of an analytical GC/MS method for the determination of long chain fatty acids
In-depth evaluation of an analytical method to detect and quantify long chain fatty acids (C8-C16) at trace level concentrations (25-1000 μg/l) is presented. The method requires derivatization of the acids with methanolic boron trifluoride, separation, and detection by gas chromatography-mass spectrometry. The calibration experiments passed all the tested performance criteria such as linearity, homoscedasticity, and ruggedness. The detection limits and related quantities were computed by applying the method detection limit, and the calibration line approximation. The values obtained by applying the latter approach were more reliable and consistent with the actual statistical theory of detection decisions and yielded the following concentrations: C8, 87.6 μg/l; C10, 45.2 μg/l; C11, 39.9 μg/l; C12, 37.7 μg/l; C14, 41.4 μg/l and C16, 40.6 μg/l. Two different gas-liquid chromatographic columns were tested and similar results achieved, which shows the ruggedness of the method. 相似文献
5.
Martin Schwell Yves BénilanNicolas Fray Marie-Claire GazeauEt. Es-Sebbar Gustavo A. GarciaLaurent Nahon Norbert ChampionSydney Leach 《Chemical physics》2012,393(1):107-116
A VUV photoionization study of acetamide was carried out over the 8-24 eV photon energy range using synchrotron radiation and photoelectron/photoion coincidence (PEPICO) spectroscopy. Threshold photoelectron photoion coincidence (TPEPICO) measurements were also made. Photoion yield curves and branching ratios were measured for the parent ion and six fragment ions. The adiabatic ionization energy of acetamide was determined as I.E. (12A′) = (9.71 ± 0.02) eV, in agreement with an earlier reported photoionization mass spectrometry (PIMS) value. The adiabatic energy of the first excited state of the ion, 12A″, was determined to be ≈10.1 eV. Assignments of the fragment ions and the pathways of their formation by dissociative photoionization were made. The neutral species lost in the principal dissociative photoionization processes are CH3, NH2, NH3, CO, HCCO and NH2CO. Heats of formation are derived for all ions detected and are compared with literature values. Some astrophysical implications of these results are discussed. 相似文献
6.
Mark G. Humphrey Brian W. Skelton Allan H. White Brian F. Yates 《Journal of organometallic chemistry》2005,690(6):1487-1497
Treatment of Ru3(CO)12 with Ph3PS affords the compounds [Ru3(μ3-S)2(CO)9 − n(PPh3)n] (n = 1 (1a), 2 (2a)) and [Ru3(μ3-S)(μ3-CO)(CO)7(PPh3)2] (3a) as the major products. Single crystal X-ray diffraction studies of [Ru3(μ3-S)2(CO)8(PPh3)] and [Ru3(μ3-S)(μ3-CO)(CO)7(PPh3)2] show these two classes of compounds to contain square pyramidal Ru3S2 and trigonal pyramidal Ru3S metal cores, respectively, with the latter being isostructural to the analogous selenide cluster compound. The clusters [Ru3(μ3-E)2(CO)9 − n(PPh3)n] (E = S, n = 1; E = Se, n = 2) readily undergo ligand displacement reactions with PPh3 to afford the compounds [Ru3(μ3-E)2(CO)6(PPh3)3] (E = S, 5a; E = Se 5b). The mixed chalcogenide cluster, [Ru3(μ3-S)(μ3-Se)(CO)7(PPh3)2] (6), was prepared from the reaction of [Ru3(μ3-S)(μ3-CO)(CO)7(PPh3)2] and SePPh3. The optical limiting properties of the complexes 1a,b, 2a,b, 5a,b have been measured by the Z-scan technique employing 40 ns pulses at 523 nm; power limiting was observed for all clusters under our experimental conditions. 相似文献
7.
M. Angeles Alvarez 《Journal of organometallic chemistry》2010,695(1):36-2066
The 30-electron binuclear anion [Mo2Cp2(μ-PCy2)(μ-CO)2]− reacts with the chlorophosphite ClP(OEt)2 or the organotin chlorides Cl2SnPh2 or ClSnPh3 to give compounds of the formula trans-[Mo2Cp2(μ-E)(μ-PCy2)(CO)2], (E = P(OEt)2, SnPh3, SnPh2Cl). In contrast, this anion reacts with the organosilicon chlorides ClSiR3 (R = Ph, Me) to give unstable silyloxycarbyne-bridged complexes [Mo2Cp2(μ-PCy2)(μ-COSiR3)(μ-CO)], which rapidly hydrolyze to give the known hydride [Mo2Cp2(μ-H)(μ-PCy2)(CO)2]. Two main types of products were also observed in the reactions of the title anion with different chlorocomplexes of the transition and post-transition metals. Thus, the reactions with [MCl2Cp2] (M = Ti, Zr) give moisture-sensitive isocarbonyl-bridged complexes of the type [Mo2Cp2(μ-COMClCp2)(μ-PCy2)(μ-CO)]. In contrast, softer metallic electrophiles such as [AuCl(PR3)] (R = iPr, ptol) react with the anion at the dimolybdenum site to form new trimetallic clusters of the formula [AuMo2Cp2(μ-PCy2)(CO)2(PR3)], also retaining a Mo−Mo triple bond. Subsequent reactions of the latter products with the solvate complexes [Au(PR3)(THF)][PF6] give the tetranuclear clusters [Au2Mo2Cp2(μ-PCy2)(CO)2(PR3)2][PF6] (Mo−Mo = 2.5674(3) Å and Au−Au = 2.7832(2) Å when R = iPr). Finally, the reaction of the title anion with HgI2 gives the pentanuclear cluster [Hg{Mo2Cp2(μ-PCy2)(CO)2}2] or the trinuclear cluster [Mo2Cp2(μ-HgI)(μ-PCy2)(CO)2] depending on the stoichiometry being actually used for the reaction. The trinuclear species is only stable in tetrahydrofuran (THF), and decomposes to give a mixture of the dimeric species [Mo2Cp2(μ-HgI)(μ-PCy2)(CO)2]2 along with variable amounts of the known iodide-bridged complex [Mo2Cp2(μ-I)(μ-PCy2)(CO)2]. 相似文献
8.
Poly(3,4-ethylenedioxythiophene) nanotubes (PEDOT NTs) flexible membrane was successfully fabricated by vapor deposition polymerization (VDP) mediated electrospinning for ammonia gas detection. PVA nanofibers (NFs) were electrospun as a core part and polyvinyl alcohol (PVA)/PEDOT coaxial nanocables (NCs) were prepared by VDP method via EDOT monomer adsorption onto the electrospun PVA NFs as templates. To obtain the PEDOT NTs membrane, the PVA NFs were removed from PVA/PEDOT coaxial NCs with distilled water. PVA/PEDOT coaxial NCs and PEDOT NTs had the conductivities of 71 and 61 S cm−1 and were applied as a transducer for ammonia gas detection in the range of 1-100 parts per million (ppm) of NH3 gas. They exhibited the minimum detectable level of ca. 5 parts per million (ppm) and fast response time (less than 1 s) towards ammonia gas. In a recovery time, the PEDOT NTs membrane sensor was ca. 30 s and shorter compared to that of the membrane sensor based on the PVA/PEDOT NCs (ca. 50 s). In addition, sensor performance of PEDOT NTs membrane was also undertaken as a function of membrane thickness. Thick membrane sensor (30 μm) had the enhanced sensitivity and the sensitivity on the membrane thickness was in the order of 30 μm > 20 μm > 10 μm at 60 ppm of NH3 gas. 相似文献
9.
A chemiluminescence one-shot sensor for hydrogen peroxide is described. It is prepared by immobilization of cobalt chloride and sodium lauryl sulphate in hydroxyethyl cellulose matrix cast on a microscope cover glass. Luminol, sodium phosphate and the sample are mixed before use and applied on the membrane by a micropipette. The calibration graph is linear in the range 20-1600 μg/L, and the detection limit of the method (3σ) is 9 μg/L. A relative standard deviation of 4.5% was obtained for 100 μg/L H2O2 (n = 11). The sensor has been applied successfully to the determination of hydrogen peroxide in rainwater. 相似文献
10.
A terminally coordinated CO ligand in the complexes [Fe2{μ-CN(Me)R}(μ-CO)(CO)2(Cp)2][SO3CF3] (R = Me, 1a; R = Xyl, 1b; Xyl = 2,6-Me2C6H3), is readily displaced by primary and secondary amines (L), in the presence of Me3NO, affording the complexes [Fe2{μ-CN(Me)R}(μ-CO)(CO)(L)(Cp)2][SO3CF3] (R = Me, L = NH2Et, 4a; R = Xyl, L = NH2Et, 4b; R = Me, L = NH2Pri, 5a; R = Xyl, L = NH2Pri, 5b; R = Xyl, L = NH2C6H11, 6; R = Xyl, L = NH2Ph, 7; R = Xyl, L = NH3, 8; R = Me, L = NHMe2, 9a; R = Xyl, L = NHMe2, 9b; R = Xyl, = NH(CH2)5, 10). In the absence of Me3NO, NH2Et gives addition at the CO ligand of 1b, yielding [Fe2{μ-CN(Me)(Xyl)}(μ-CO)(CO){C(O)NHEt}(Cp)2] (11). Carbonyl replacement is also observed in the reaction of 1a-b with pyridine and benzophenone imine, affording [Fe2{μ-CN(Me)R}(μ-CO)(CO)(L)(Cp)2][SO3CF3] (R = Me, L = Py, 12a; R = Xyl, L = Py, 12b; R = Me, L = HNCPh2, 13a; R = Xyl, L = HNCPh2, 13b). The imino complex 13b reacts with p-tolylacetylide leading to the formation of the μ-vinylidene-diaminocarbene compound [Fe2{μ-η1:η2- CC(Tol)C(Ph)2N(H)CN(Me)(Xyl){(μ-CO)(CO)(Cp2)] (15) which has been studied by X-ray diffraction. 相似文献
11.
Three platinum group elements (Pd, Ir and Rh) both in solution and in pre-reduced form, and also combined with Mg(NO3)2 or ascorbic acid, were assessed as possible chemical modifiers on the atomization of As in digest solutions of seafood matrices (clam and fish tissue) by tungsten coil electrothermal atomic absorption spectrometry (TCA-AAS) and compared without a modifier. Of 28 modifier alternatives in study including single form and binary mixtures, and based on maximum pyrolysis temperature without significant As loss and best As absorbance sensitivity during atomization, three modifiers: Rh (0.5 μg), Ir (1.0 μg) and Rh (0.5 μg) + ascorbic acid (0.5 μg), at optimum amounts were pre-selected and compared. The definitive modifier (rhodium (0.5 μg)) was selected by variance analysis. The mean within-day repeatability was 3% in consecutive measurements (25-300 μg l−1) (three cycles, each of n = 6) and showed good short-term stability of the absorbance measurements. The mean reproducibility was 4% (n = 18 in a 3-day period) and the detection limit (3σblank/slope) was 42 pg (n = 16). Quantitation was by standard additions to compensate for matrix effects not corrected by the modifier. Three sample digestion procedures were compared in fish and clam tissue samples: microwave acid digestion alone (A) or combined with the addition of 2% (m/v) K2S2O8 solution followed either by UV photo-oxidation (B) or re-digestion in a thermal block (C). The accuracy was established by determination of As in certified reference material of dogfish muscle (DORM-2). Procedures B and C showed good recoveries (102% (n = 4) and 103% (n = 7), respectively), whereas procedure A was not quantitative (85%). The methodology is simple, fast, reliable, of low cost and was applied to the determination of total As in lyophilized samples of clam and fish collected in the Chilean coast. 相似文献
12.
Luigi Busetto 《Journal of organometallic chemistry》2008,693(1):57-67
The bridging aminocarbyne complexes [Fe2{μ-CN(Me)(R)}(μ-CO)(CO)2(Cp)2][SO3CF3] (R = Me, 1a; Xyl, 1b; 4-C6H4OMe, 1c; Xyl = 2,6-Me2C6 H3) react with acrylonitrile or methyl acrylate, in the presence of Me3NO and NaH, to give the corresponding μ-allylidene complexes [Fe2{μ-η1:η3- Cα(N(Me)(R))Cβ(H)Cγ(H)(R′)}(μ-CO)(CO)(Cp)2] (R = Me, R′ = CN, 3a; R = Xyl, R′ = CN, 3b; R = 4-C6H4OMe, R′ = CN, 3c; R = Me, R′ = CO2Me, 3d; R = 4-C6H4OMe, R′ = CO2Me, 3e). Likewise, 1a reacts with styrene or diethyl maleate, under the same reaction conditions, affording the complexes [Fe2{μ-η1:η3-Cα(NMe2)Cβ(R′)Cγ(H)(R″)}(μ-CO)(CO)(Cp)2] (R′ = H, R″ = C6H5, 3f; R′ = R″ = CO2Et, 3g). The corresponding reactions of [Ru2{μ-CN(Me)(CH2Ph)}(μ-CO)(CO)2(Cp)2][SO3CF3] (1d) with acrylonitrile or methyl acrylate afford the complexes [Ru2{μ-η1:η3-Cα(N(Me)(CH2Ph))Cβ(H)Cγ(H)(R′)}(μ-CO)(CO)(Cp)2] (R′ = CN, 3h; CO2Me, 3i), respectively.The coupling reaction of olefin with the carbyne carbon is regio- and stereospecific, leading to the formation of only one isomer. C-C bond formation occurs selectively between the less substituted alkene carbon and the aminocarbyne, and the Cβ-H, Cγ-H hydrogen atoms are mutually trans.The reactions with acrylonitrile, leading to 3a-c and 3h involve, as intermediate species, the nitrile complexes [M2{μ-CN(Me)(R)}(μ-CO)(CO)(NC-CHCH2)(Cp)2][SO3CF3] (M = Fe, R = Me, 4a; M = Fe, R = Xyl, 4b; M = Fe, R = 4-C6H4OMe, 4c; M = Ru, R = CH2C6H5, 4d).Compounds 3a, 3d and 3f undergo methylation (by CH3SO3CF3) and protonation (by HSO3CF3) at the nitrogen atom, leading to the formation of the cationic complexes [Fe2{μ-η1:η3-Cα(N(Me)3)Cβ(H)Cγ(H)(R)}(μ-CO)(CO)(Cp)2][SO3CF3] (R = CN, 5a; R = CO2Me, 5b; R = C6H5, 5c) and [Fe2{μ-η1:η3-Cα(N(H)(Me)2)Cβ(H)Cγ(H)(R)}(μ-CO)(CO)(Cp)2][SO3CF3] (R = CN, 6a; R = CO2Me, 6b; R = C6H5, 6c), respectively.Complex 3a, adds the fragment [Fe(CO)2(THF)(Cp)]+, through the nitrile functionality of the bridging ligand, leading to the formation of the complex [Fe2{μ-η1:η3-Cα(NMe2)Cβ(H)Cγ(H)(CNFe(CO)2Cp)}(μ-CO)(CO)(Cp)2][SO3CF3] (9).In an analogous reaction, 3a and [Fe2{μ-CN(Me)(R)}(μ-CO)(CO)2(Cp)2][SO3CF3], in the presence of Me3NO, are assembled to give the tetrameric species [Fe2{μ-η1:η3-Cα(NMe2)Cβ(H)Cγ(H)(CN[Fe2{μ- CN(Me)(R)}(μ-CO)(CO)(Cp)2])}(μ-CO)(CO)(Cp)2][SO3CF3] (R = Me, 10a; R = Xyl, 10b; R = 4-C6H4OMe, 10c).The molecular structures of 3a and 3b have been determined by X-ray diffraction studies. 相似文献
13.
The sampling efficiency of C18 solid-phase extraction cartridges was investigated for methylamine, ethylamine, propylamine, butylamine and pentylamine, in air. Determination of these analytes was based on derivatization with o-phthaldialdehyde-N-acetylcysteine (OPA-NAC) on the solid support and fluorescence detection at λexcitation=330 nm and λemission=440 nm of the eluted derivatives. The calibration model derived from aqueous standards was statistically comparable with the calibration model for air standards. Aqueous amines can be used as standards. The method was useful for calculating short-term exposure limits (STEL). A sampling time of 15 min at 30 ml min−1 was employed. Good recoveries for amines alone and their mixtures were obtained from air and water samples, 98±14 and 97±12% (mean ), respectively. Recovery values were independent of amine concentration. The detection limits varied between 0.16 and 0.52 μg per sample (0.35 and 1.18 mg m−3, respectively) and the calibration graphs were linear in the range 0.5-2 μg per sample except for pentylamine, which was 1.5-5 μg per sample. The utility of the method was demonstrated for the estimation of methylamine in two generated air samples. 相似文献
14.
A new method was developed for simultaneous determination of cypermethrin and permethrin residues in pear juice with ultrasound-assisted dispersive liquid-liquid microextraction (UA-DLLME) and gas chromatography-flame ionization detection (GC-FID). 3.5 mL of methanol (dispersant) and 30 μL of C2Cl4 (extractant) were injected into 5.0 mL of pear juice sample and then emulsified by ultrasound for 2.0 min to forming the cloudy solution. Under the optimum condition, the enrichment factors for cypermethrin and permethrin were 344 and 351 fold respectively. Good linearity was observed in a range of 0.009-1.52 μg g−1 with the correlation coefficient (r2)≥0.9993. The limits of detection (LODs) were 3.1 and 2.2 μg kg−1 for cypermethrin and permethrin, respectively (S/N = 3). The recoveries of the method evaluated at three spiked levels were in the range of 92.1%-107.1%. The repeatability evaluated as intra-day and inter-day precision (RSDs) were less than 4.0% (n = 5). The developed method was successfully applied to determine the two pesticide residues in different pear juice samples. 相似文献
15.
The reaction of tricarbonylpentadienylmanganese with aryl mercaptans in the presence of phosphines or phosphites afforded dinuclear complexes, [Mn2(CO)4(μ-CO)(μ-SR)2(PR′3)2]; R = Ph for PR′3 = PPh3, PMe3, P(OMe)3, P(OEt)3, PMePh2 and R = m-, p-NH2C6H4S-, for PR′3 = PPh3 in one pot synthesis. Two reaction routes were proposed for the formation of the dinuclear complexes depending on the relative basicity of the sulfur vs. phosphine ligands. Characterization of the complexes was effected in solution and, for [Mn2(CO)4(μ-CO)(μ-SPh)2(PPh3)2], [Mn2(CO)4(μ-CO)(μ-SPh)2(P(OEt)3)2], and [Mn2(CO)4(μ-CO)(μ-SPh)2(PMe3)2], by X-ray crystallographic analysis. 相似文献
16.
Javier A. Cabeza Ignacio del Río Enrique Pérez-Carreño 《Journal of organometallic chemistry》2008,693(1):97-102
The cluster [Ru3(μ3-κ2-HNNMe2)(μ-κ2-PhCHCPh)(μ-CO)2(CO)6], which has a face-capping 1,1-dimethylhydrazido and an edge-bridging 1,2-diphenylethenyl ligand, reacts with diphenylbutadiyne or 2,4-hexadiyne to give the isomeric triruthenium carbonyl cluster complexes [Ru3(μ3-κ2-HNNMe2)(μ-κ2-PhCHCPh){μ3-κ4-RCCCC(R)C(R)CCCR}(CO)6] (3a, R = Ph; 3b, R = Me) and [Ru3(μ3-κ2-HNNMe2)(μ-κ2-PhCHCPh){μ3-κ4-RCCCC(R)C(CCR)CR}(CO)6] (4a, R = Ph; 4b, R = Me). These compounds contain a large unsaturated hydrocarbyl ligand that arises from a metal-cluster-mediated head-to-head (3) or head-to-tail (4) coupling of two diyne molecules and maintain the original hydrazido and ethenyl ligands. Metal clusters that contain a face-capping diyne coordinated through only one alkyne fragment, such as [Ru3(μ3-κ2-HNNMe2)(μ-κ2-PhCHCPh)(μ3-κ2-RCCCCR)(CO)7], have also been isolated (2a, R = Ph; 2b, R = Me). They are the intermediates that incorporate a second diyne reagent to give 3 and 4. The structural parameters of intermediate 2b have been obtained from DFT calculations. 相似文献
17.
Wenjing Qi Jianming Zhao Wei Zhang Zhongyuan Liu Min Xu Saima Anjum Saadat Majeed Guobao Xu 《Analytica chimica acta》2013
Owing to its high affinity with phosphate, Zr(IV) can induce the aggregation of adenosine 5′-triphosphate (ATP)-stabilized AuNPs, leading to the change of surface plasmon resonance (SPR) absorption spectra and color of ATP-stabilized AuNP solutions. Based on these phenomena, visual and SPR sensors for Zr(IV) have been developed for the first time. The A660 nm/A518 nm values of ATP-stabilized AuNPs in SPR absorption spectra increase linearly with the concentrations of Zr(IV) from 0.5 μM to 100 μM (r = 0.9971) with a detection limit of 95 nM. A visual Zr(IV) detection is achieved with a detection limit of 30 μM. The sensor shows excellent selectivity against other metal ions, such as Cu2+, Fe3+, Cd2+, and Pb2+. The recoveries for the detection of 5 μM, 10 μM, 25 μM and 75 μM Zr(IV) in lake water samples are 96.0%, 97.0%, 95.6% and 102.4%, respectively. The recoveries of the proposed SPR method are comparable with those of ICP-OES method. 相似文献
18.
In this paper, a new method for separation, identification and quantitation of iodotyrosines and iodothyronines [3-monoiodo-L-tyrosine (MIT), 3,5-diiodo-L-tyrosine (DIT), L-thyronine (T0), 3,5-diiodo-L-thyronine (T2), 3,5,3′-triiodo-L-thyronine (T3) and 3,3′,5,5′-tetraiodo-L-thyronine (T4)] was described by using capillary electrophoresis with photodiode-array ultraviolet-visible detection (CE-UV). The certain influence factors were systematically investigated, including the type, concentration and pH of buffer, and additive. We found that 10 mM sodium borate running buffer (pH 8.5) containing 0.10 mM β-CD as additive reagent allowed the best instrumental conditions for the optimum separation of the iodotyrosines and iodothyronines. Under optimized conditions, the analytical time was within 6 min, using an uncoated fused-silica capillary of 75 μm inner diameter with an effective length of 30 cm. The reproducibility of the migration time and peak area was less than 0.6% and 6.8%, respectively. A linear range from 10-1000 μg/mL and low limits of detection from 1.3-3.4 μg/mL were obtained at the detection wavelength of 280 nm. Our preliminary results show that the method is well suitable for determination of the hydrolysate of iodinated casein. 相似文献
19.
Feyime ?ahin 《Analytica chimica acta》2005,547(1):126-131
Determination of selenium by electrothermal atomic absorption spectrometry (ETAAS) is complicated by the presence of different species of this analyte. The presence of different oxidation states (−II, IV and VI) may result in different sensitivities obtained for each species rendering impossible the use of a single species for calibration. These species also exhibit different behaviours regarding thermal stabilities; the temperature program must be provided to conform to this problem. Chemical modifiers are commonly used for thermal stabilization of selenium species. In this study, experiments were carried out to demonstrate the effect of nitric acid in the presence of chemical modifiers. Nickel and palladium + magnesium were selected as the most commonly used chemical modifiers. Using both aqueous and human serum solutions it has been demonstrated that although chemical modifiers provide thermal stabilization of species so that higher ashing temperatures can be used, equal sensitivities cannot be achieved unless nitric acid is also present. Selenite, selenate, selenomethionine and selenocystine were used in experiments. When equal sensitivities for all these species are achieved, determination of total selenium by ETAAS can be performed by using a single species as the standard; selenite was used in this study. Precision was 5.0% or better using peak height signals. There was no significant difference in detection limits (3s) when Ni or Pd + Mg(NO3)2 was used as chemical modifier; 37 and 35 pg of selenium were found to be the detection limits for Ni and Pd + Mg(NO3)2 chemical modifiers, respectively. For chemical modifications, either 5 μg of Ni or 0.5 μg of Pd and 5 μg of Mg(NO3)2 were used; final solutions contained 2.5% HNO3. In serum analyses, 10 μg of Ni was used in presence of 2.5% HNO3. 相似文献
20.
A flow-based procedure was developed for the direct spectrophotometric determination of the iodine value (IV) in biodiesel. The procedure was based on the microextraction/reaction of unsaturated compounds with triiodide ions in an aqueous medium by inserting the reagent solution between the aliquots of biodiesel without any pretreatment. The interaction occurred through the biodiesel film formed on the inner walls of the hydrophobic tube used as the reactor and at the aqueous/biodiesel interfaces. The spectrophotometric detection was based on the discoloration of the I3− reagent in the aqueous phase by using a glass tube coupled to a fiber-optic spectrophotometer as the detection cell. Reference solutions were prepared by dilution of biodiesel samples with previously determined IV in hexane. The analytical response was linear for IV from 13 to 135 g I2/100 g with a detection limit of 5 g I2/100 g. A coefficient of variation of 1.7% (n = 10) and a sampling rate of 108 determinations per hour were achieved by consuming 224 μL of the sample and 200 μg of I2 per determination. The slopes of analytical curves obtained with three different biodiesel samples were in agreement (variations in slopes lower than 3.1%), thus indicating an absence of any matrix effects. Results for biodiesel samples from different sources agreed with the volumetric official procedure at the 95% confidence level. The proposed procedure is therefore a simple, fast, and reliable alternative for estimating the iodine value of biodiesel. 相似文献