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81.
In the present work, the cathodic stripping voltammetric methodology using a hanging mercury drop electrode was described for simultaneous determination of lead and zinc in different real samples. The method is based on adsorption of metal ions on mercury electrode using carbidopa as a suitable complexing agent. The potential was scanned to the negative direction and the differential pulse stripping voltammograms were recorded. Optimal conditions were found to be: accumulation time; 70 s, accumulation potential; 50 mV versus Ag/AgCl, scan rate; 40 mV s?1, supporting electrolyte; 0.01 M ammonia buffer at pH 8.5, and concentration of carbidopa; 8.0 μM. The relationship between the peak current versus concentration was linear over the range of 0.1–210 and 0.2–170 nM for lead and zinc, respectively. The detection limits are 0.09 and 0.15 nM for lead and zinc ions respectively. The relative standard deviations at a concentration level of 70 nM of both metal ions are found 1.08 and 1.24% for lead and zinc ions respectively. 相似文献
82.
In the present study a multi-residue analytical method was developed for monitoring some polar pesticides such as acephate,
methamidophos, carbofuran, isoproturon, dimethoate in water with SPE (solid-phase extraction) and LC–MS–MS. Acetochlor was
taken as surrogate, and alachlor as internal standard. SPE with different types of columns was compared with LLE (liquid-liquid
extraction). Further, the breakthrough volume for different pesticides was determined. The results showed that the selected
pesticides can be determined very sensitively with LC–MS–MS. The minimum detectable quantity (MDQ) for each pesticide was
about 1.0 ng. To date, SPE cartridge studies showed that the Oasis HLB cartridges were suitable for further studies. However,
for Oasis HLB cartridge, different pesticide showed different breakthrough volume. The results showed that for acephate and
methamidophos, the breakthrough volume was about 30 mL of water sample, much less than the breakthrough volume of other pesticides
studied. Because of the higher vapor pressure and higher Henry's constant of methamidophos, dimethoate and carbofuran, much
attention should be paid on their losses in the evaporation step of the experiment. This analytical method can be applied
to determine pesticide contamination in environmental water samples.
Revised: 12 September 2005 and 21 October 2005 相似文献
83.
An evaluation of the non-boiling evaporation technique for the preconcentration of Pb, Cd, Cu, Zn at the pg g?1 level in water samples is presented. Various improvements were made to allow efficient control of contamination problems at these extremely low concentrations. They include the choice of FEP Teflon for the evaporation containers and the use of sophisticated cleaning, ageing and pre-conditionning procedures. Detailed calibration graphs were obtained down to the sub-pg g?1 level by processing ultra-low concentration standards. This technique was then applied to the determination of these four metals in snow samples collected in Greenland and Antarctica. 相似文献
84.
An on-line coupled continuous flow liquid membrane extraction (CFLME) and C18 precolumn system was developed for sample preconcentration in liquid chromatography determination. After preconcentration by CFLME, which is based on the combination of continuous flow liquid–liquid extraction and supported liquid membrane, bisphenol A (BPA) was enriched in 960 μl of 1 mol l−1 NaOH used as acceptor. This acceptor was on-line neutralized and transported onto the C18 precolumn where analytes were absorbed and focused. Then the focused analytes were injected onto a C18 analytical column for separation and detected at 220 nm with a diode array detector. CFLME related parameters such as flow rates, pH of donor and acceptor, and enrichment time were optimized. The proposed method presents a detection limit of 0.03 μg l−1 (S/N=3) when 60 ml samples was enriched with an enrichment time of 30 min. Compared with C18 based column-switching procedure, this proposed procedure presents similar sample throughput and lower detection limits. The proposed method was successfully applied to determine BPA in tap water, river water, and municipal sewage effluent samples. 相似文献
85.
Anantha Iyengar Gopalan Kwang-Pill Lee Kalayil Manian Manesh Jun Heon Kim Jae Soo Kang 《Talanta》2007,71(4):1774-1781
A modified electrode is fabricated by embedding gold nanoparticles into a layer of electroactive polymer, poly(4-aminothiophenol) (PAT) on the surface of glassy carbon (GC) electrode. Cyclic voltammetry (CV) is performed to deposit PAT and concomitantly deposit Au nanoparticles. Field emission transmission electron microscopic image of the modified electrode, PAT-Aunano-ME, indicates the presence of uniformly distributed Au nanoparticles having the sizes of 8-10 nm. Electrochemical behavior of the PAT-Aunano-ME towards detection of ascorbic acid (AA) and dopamine (DA) is studied using CV. Electrocatalytic determination of DA in the presence of fixed concentration of AA and vice versa, are studied using differential pulse voltammetry (DPV). PAT-Aunano-ME exhibits two well defined anodic peaks at the potential of 75 and 400 mV for the oxidation of AA and DA, respectively with a potential difference of 325 mV. Further, the simultaneous determination of AA and DA is studied by varying the concentration of AA and DA. PAT-Aunano-ME exhibits selectivity and sensitivity for the simultaneous determination of AA and DA without fouling by the oxidation products of AA or DA. PAT and Au nanoparticles provide synergic influence on the accurate electrochemical determination of AA or DA from a mixture having any one of the component (AA or DA) in excess. The practical analytical utilities of the PAT-Aunano-ME are demonstrated by the determination of DA and AA in dopamine hydrochloride injection and human blood serum samples. 相似文献
86.
Sabry K. Mohamed 《Analytica chimica acta》2006,562(2):204-209
A poly(vinyl chloride)-based membrane of 2,9-dimethyl-4,11-diphenyl-1,5,8,12-tetraazacyclotetradeca-1,4,8,11-tetraene (DDTCT) with sodium tetraphenyl borate (STB) as an anion excluder and dibutyl phthalate (DBP), dibutyl butylphosphonate (DBBP), tris(2-ethylhexyl) phosphate (TEP) and tributyl phosphate (TBP) as plasticizing solvent mediators was prepared and investigated as a Ga(III)-selective electrode. The best performance was observed with the membrane having the ligand-PVC-DBP-STB composition 1:4:1:1, which worked well over a wide concentration range (1.45 × 10−6 to 0.1 mol L−1) with a Nernstian slope of 28.7 mV per decade of activity between pH 4.0 and 10.0. This electrode showed a fast response time of 12 s and was used over a period of 100 days with good reproducibility (s = 0.3 mV). The selectivity coefficients for monovalent, divalent and trivalent cations indicate excellent selectivity for Ga(III) ions over a large number of cations. Anions such as Cl− and SO42− do not interfere and the electrode also works satisfactorily in partially water-alcohol medium. The practical utility of the membrane sensor has also been observed in solutions contaminated with detergents, i.e., cetyltrimethylammonium bromide and sodium dodecyl sulfate and used for the determination of gallium in nickel alloy, fly-ash and biological samples. 相似文献
87.
微波增压溶样-石墨炉原子吸收光谱法同时测定植物性样品中微量铅镉 总被引:7,自引:2,他引:7
使用微波增压溶样法,将样品用HNO3—HClO4溶解后,用石墨炉原子吸收光谱法同时测定植物性样品中铅和镉。以磷酸二氢铵—硝酸镁作为基体改进剂,可使灰化温度大大提高,克服了基体的干扰。铅和镉的回收率分别为95.3%—104.8%和96.2%—105.5%,RSD分别为4.8%-7.2%和4.3%-7.6%。 相似文献
88.
A novel kinetic method for the determination of trace amounts of Co(II) has been developed. The proposed method based on the catalytic effect of Co(II) on the oxidation of xylenol orange tetra sodium salt by H2O2 in the presence of cationic surfactant (N‐dodecylpyridinium chloride). Co(II) at μg.mL?1 was determined spectrophotometrically by measuring the decrease in the absorbance of xylenol orange at 577 nm by the differential method. The method is precise, selective, and sensitive. The detection limit of the procedure was 0.058 μg.mL?1. The relative standard deviation for the replicate determination (n = 6) of 0.7 μg.mL?1 was 1.285%. The results compared satisfactorily with those of atomic absorption spectrometry. The method was successful for the analysis of Co(II) in veterinary and synthetic samples. 相似文献
89.
Kanchi Suvardhan Kailasa Suresh Kumar Dasari Rekha Pantrangam Subrahmanyam Kapuvedi Kiran Bellum Jayaraj Surasura Ramanaiah Kandhukuri Janardhanam Pattium Chiranjeevi 《Mikrochimica acta》2007,157(3-4):237-244
Cloud point extraction was applied as a method for preconcentration of rhodium after formation of a complex with 2-propylpiperidine-1-carbodithioate
(2-PPC), and later determined by flame atomic absorption spectrometry using TritonX-114 as surfactant. Rhodium was complexed
with 2-PPC in an aqueous phase and kept for 15 min in a thermostatted bath at 40 °C. Separation of the two phases was accomplished
by centrifugation for 15 min at 4000 rpm. The chemical variables affecting the cloud point extraction were optimized and successfully
applied to rhodium determination in various water samples. Under optimized conditions, the preconcentration system (100 mL
sample) permitted an enhancement factor of 50. The detection limits obtained under optimal conditions was 0.052 ng mL−1. The extraction efficiency was investigated at different rhodium concentrations (7.0–42.0 μg mL−1), and good recoveries (96.42–99.14%) were obtained using this method. It has been applied to the determination of rhodium
in water and was compared with reported methods in terms of Student’s ‘t’-test and variance ratio ‘f’-test. 相似文献
90.
β-Cyclodextrin-polyurethane polymer as solid phase extraction material for the analysis of carcinogenic aromatic amines 总被引:1,自引:0,他引:1
β-Cyclodextrin-polyurethane (β-CDPU) polymer was synthesized by the reaction of β-cyclodextrin with hexamethylene diisocyanate in dry dimethylformamide and used as a sorbent for the solid phase extraction (SPE) of carcinogenic aromatic amines from water. The polymers were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry and particle size analysis. The separation and quantification was performed by Liquid chromatography with RP-C18 column and diode array detection using standard arylamines for quantification. When compared with commercially available sorbents, β-CDPU gave better recovery for the aromatic amines. From the variation of pH of the extractant from 4.0 to 8.5 recovery was highest at pH 8.5. The breakthrough volume has been ascertained to be 100 ml for 200 mg of the resin. The new SPE material offers better recovery and estimation of banned arylamines. 相似文献