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1.
Valfredo Azevedo Lemos Moacy Selis Santos Márcio José Silva dos Santos Daniel Rodrigues Vieira Cleber Galvão Novaes 《Mikrochimica acta》2007,157(3-4):215-222
Cloud point extraction employing the new reagent 6-[2′-(6′-methyl-benzothiazolylazo)]-1,2-dihydroxy-3,5-benzenedisulfonic
acid as complexing agent and Triton X-114 as the surfactant is proposed for copper determination. A sample volume of 10 mL
was used. Dilution of the surfactant-rich phase with acidified methanol was performed after phase separation, and the copper
contents were measured by flame atomic absorption spectrometry. Variables affecting the system were optimized using factorial
design and Doehlert matrix. Signals were measured as peak height using an instrument software. Using the experimental conditions
defined in the optimization, the method allowed copper determination with a detection limit of 1.5 μg L−1. The calculated enrichment factor is 14. The effects of foreign ions are reported. The accuracy of the procedure was tested
by analyzing certified reference material. The method was successfully applied to copper determination in natural and drinking
water samples. 相似文献
2.
Two simple high-performance liquid chromatographic (HPLC) methods have been established for simultaneous determination of
mycophenolic acid (MPA) and its glucuronide metabolite (MPAG) in human urine, and of their total and unbound forms in human
plasma. For total MPA and MPAG analysis sample preparation entailed precipitation of protein with acetonitrile and isolation
of the free analytes from the plasma by ultrafiltration. For urine samples, fivefold dilution with water was used. MPAG was
determined by UV detection whereas MPA was quantified by fluorescence detection after post-column derivatization with 0.2
M sodium hydroxide solution. For plasma, response was found to be linearly dependent on concentration over the ranges 0.1–40
μg mL-1 and 0.01–1 μg mL-1 for total and free MPA, respectively, and 10–200 μg mL-1 and 2.5–100 μg mL-1 for total and free MPAG, respectively. For urine, linearity was observed from 0.1 to 50 μg mL-1 for MPA and 10 to 500 μg mL-1 MPAG in the urine before dilution. The methods reported were found to be accurate and reproducible for quantifying the level
of MPA and MPAG and can thus be used for clinical pharmacokinetic studies and for therapeutic drug monitoring.
Contributed equally to this work
An erratum to this article is available at . 相似文献
3.
E. Burestedt J. Emnéus L. Gorton G. Marko-Varga E. Domínguez F. Ortega A. Narváez H. Irth M. Lutz D. Puig D. Barceló 《Chromatographia》1995,41(5-6):207-215
Summary A fully integrated screening system for phenolic compounds was developed incorporating on-line solid phase extraction, fractionation
and biosensor detection. Two different types of biosensors, solid graphite and carbon paste electrodes incorporating the enzyme
tyrosinase, were compared and used in the screening system. Interfacing of the solid phase extraction and fractionation with
the biosensor detection was given special attention since the biosensors were not compatible with the organic modifier used
for desorption of phenols from the solid phase extraction step. The system was validated with conventional analytical techniques.
Surface water samples from the Ebro river were spiked with 1,10, and 25 μg L−1 of catechol, phenol,p-cresol, respectively. Three out of seven samples were spiked and the correct samples were identified, containing phenols
equivalent to the spiked concentrations. 相似文献
4.
Dirk Flottmann Juergen Hins Christian Rettenmaier Norbert Schnell Zyrafete Kuçi Gisela Merkel Gisela Seitz Gernot Bruchelt 《Mikrochimica acta》2006,154(1-2):49-53
Homovanillic acid (HVA) and vanillylmandelic acid (VMA) are routinely analyzed by HPLC with electrochemical detection after
solid phase extraction for the diagnosis of neuroblastoma and phaechromocytoma. The aim of our study was to investigate whether
these compounds can be determined without sample preparation using capillary isotachophoresis (ITP). For this purpose we used
a commercially available instrument with two coupled capillary columns. HVA and VMA could be easily separated by ITP–ITP analysis
at pH 3.4; the LODs were in the lower μmol · L−1 range using conductivity detection. ITP calibration curves in spiked urine samples showed good linear correlation. However,
although good correlation with HPLC analysis was also found, the ITP–ITP values were elevated compared to the HPLC values
due to underlying matrix compounds in the respective zones. 相似文献
5.
Yavuz Surme Ibrahim Narin Mustafa Soylak Huseyin Yuruk Mehmet Dogan 《Mikrochimica acta》2007,157(3-4):193-199
The conditions for cloud point extraction of lead(II) from aqueous solutions were investigated and optimized. The procedure
is based on the separation of Pb(II) – brillant cresyl blue (BCB) complexes into the micellar media by adding the surfactant
Triton X-114. After phase separation, the surfactant-rich phase was dissolved with 1 mol L−1 HNO3 in ethanol and diluted with 1 mol L−1 HNO3 solution before lead was determined by flame atomic absorption spectrometry. Optimization of the pH, ligand and surfactant
quantities, incubation time, temperature, viscosity, sample volume, and interfering ions was performed. The effects of the
matrix ions were also examined. The detection limits for three times the standard deviations of the blank for lead were 7.5 μg L−1 for water samples and 0.33 μg g−1 for sediment samples. The validity of cloud point extraction was checked by employing certified reference samples of Lake
Sediment IAEA-SL-1 and Sewage Sludge BCR-CRM 144R. The procedure was applied to natural waters and sediment samples with satisfactory
results (recoveries >95%, relative standard deviations <6.4%). 相似文献
6.
Summary Modifying the most common design for the on-line coupling of a precolumn to reversed phase LC with diode array detection has
resulted in reduction of the broadening of the peaks which results when the compounds of interest are strongly retained by
a highly hydrophobic sorbent. The modification consists of the desorption of the analytes trapped on the precolumn solely
by the organic solvent used to modify the solvent strength of the mobile phase.
Results obtained using this design were compared with those obtained with the conventional design, with C18 and PLRP-S precolumns. The performance of the system was also tested with a highly cross-linked styrene-divinylbenzene copolymer
(ENVI-chrom P) precolumn for the determination of phenolic compounds in real samples. The advantages and disadvantages are
discussed. Ion-pair solid phase extraction is used in order to increase the breakthrough volumes of more polar compounds,
mainly phenol. The use of the new design enables phenolic compounds to be determined at the low μg L−1 level with limits of detection ranging between 0.1 and 2 μg L−1 in tap water when a 10 mL sample was analyzed. 相似文献
7.
Cloud Point Preconcentration and Flame Atomic Absorption Spectrometric Determination of Cobalt and Nickel in Water Samples 总被引:2,自引:0,他引:2
Cloud point methodology was successfully used to preconcentrate trace amounts of Co and Ni as a prior step to their determination
by flame atomic absorption spectrometry. 1-Nitroso-2-naphthol and polyethylene glycol-p-nonylphenylether (PONPE 7.5) are used
as hydrophobic ligand and nonionic surfactant, respectively. Optimization was performed of the variables effecting complexation
and phase separation. Additionally, the influence of viscosity on the analytical signal was investigated. Under the experimental
conditions used, preconcentration of only 10 mL of sample in the presence of 0.075% (v/v) PONPE 7.5 permitted the detection
of 1.09 μg L−1 of Ni and 1.22 μg L−1 of Co with enhancement factors of 29 and 27 for Ni and Co, respectively. The relative standard deviations (n=5) at concentrations of 80 and 50 μg L−1 for Co and Ni were 2.53 and 2.89%, respectively. Good recoveries in the range of 96–105% were obtained for spiked samples.
The effect of different interferent species was studied. The proposed method was applied to the determination of Ni and Co
in different water samples.
Correspondence: Department of Analytical Chemistry, Faculty of Chemistry, Tabriz University, Tabriz, Iran. e-mail: manzoori@tabrizu.ac.ir
Received September 1, 2002; accepted November 8, 2002 相似文献
8.
Summary A semi-automatic reversed-phase HPLC system is described for the direct determination of conjugated and unconjugated bilirubin
in human plasma. An Advanced Automated Sample Processor (AASP) is used for sample preparation, and for controlling sample
injection and elution. The method is highly sensitive, requiring only 10–50 μl of plasma per assay. 相似文献
9.
Amauri A. Menegário Paulo S. Tonello Priscila A. Biscaro Ana L. Brossi-Garcia 《Mikrochimica acta》2007,159(3-4):247-254
The use of Saccharomyces cerevisiae as a sorbent material to separate Cd(II) and Cd-metallothionein complex (Cd-MT) has been explored. Solid–liquid phase extractions
were carried out in batch mode and the main parameters of the process (pH, temperature, time of incubation, amount of biomass
and analyte) were evaluated. Under optimized conditions, the yeast quantitatively retain (94 ± 5%) the Cd(II) while 97 ± 2%
of the Cd-MT remain in the supernatant. On base of the findings of this study, a simple method is proposed to determine Cd(II)
and Cd-MT in cytosols extracted from mouse kidney and crab hepatopancreas. Inductively coupled plasma optical emission spectrometry
was used to quantify the analytes in solid and liquid phase. Determination of Cd in the solid phase was carried out by introducing
a slurry of the yeast (0.0625 g/10 mL) directly to the inductively coupled plasma optical emission spectrometer. Mixed standards
solutions, which also have been submitted to the extraction procedure, were used to quantify the analytes in the samples.
Thus, matrix effects due to nebulization of the slurry were overcame. Limits of detection (3σ) for Cd(II) and Cd-MT were 1.5
and 1.2 μg L−1, respectively. Relative standard deviations of signals were 4.2% for measurements in the slurry of solid phase and 2.1% for
measurements in the liquid phase. Recoveries of the analytes in cytosol samples were between 76 and 114%. The concentrations
of Cd(II) (2.4 ± 0.5 μg L−1) and Cd-MT (3.0 ± 0.5 μg L−1) found by using the proposed approach were close to those found by tangential-flow ultrafiltration technique (2.6 ± 0.7 μg L−1 for Cd(II) and 3.7 ± 1.7 μg L−1 for Cd-MT). 相似文献
10.
Arsenic speciation is of increasing interest to the food industry, as concerns about high total arsenic concentrations in
food can often be alleviated to a great extent if the ratio of toxic, less toxic and non-toxic arsenic compounds in the sample
is known.
The lipid matrix of fish oil is a challenge in the determination of arsenic species, as current methods for this type of analysis
require the analyte to be water-soluble. In this study, two sample preparation techniques were applied. One the one hand water-soluble
species were extracted with methanol/water, on the other, acid digestion was applied to release lipid-soluble arsenic compounds
into the aqueous phase. Ion chromatography – inductively coupled plasma mass spectrometry (IC-ICP-MS) was used for separation
and sensitive element-specific detection of arsenic compounds. Additional experiments, including alkaline hydrolysis, were
carried out to find out more about the type of lipids arsenic is bound to in fish oil.
Up to eight different arsenic species were detected and quantified in fish oil with dimethylarsinate being the major compound
both in the aqueous extract and in the acid digest. No inorganic arsenic was detected in the aqueous extract, and the maximum
concentration of arsenate determined in the acid digest was 0.05 μg g−1.
The total arsenic concentration determined by ICP-MS ranged from <0.1 to 5 μg g−1. With regard to the mass balance, approximately 1% of the total arsenic content was extractable with methanol/water, whereas
the sum of arsenic species quantified after acid digestion yielded 85–100% of the total arsenic content. It was confirmed
that the large fraction of arsenic in fish oil not extractable on an aqueous basis consists of organoarsenic compounds.
This new approach in sample preparation makes the complete characterization of the arsenic content in the sample possible
with regard to the respective species, providing necessary information required for risk assessment. 相似文献
11.
用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%. 相似文献
12.
Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields. 相似文献
13.
Uroš Grošelj Mojca Žorž Amalija Golobič Branko Stanovnik Jurij Svete 《Tetrahedron》2013,69(52):11092-11108
A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives. 相似文献
14.
The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp3)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp2)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp2)?H and aliphatic 1,5- and 1,6-C(sp3)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp3)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp2)?H insertion. 相似文献
15.
A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL. 相似文献
16.
A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions. 相似文献
17.
Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction
Laurent Gavara Thomas Boisse Jean-Pierre Hénichart Adam Daïch Philippe Gautret 《Tetrahedron》2010,66(38):7544-5571
In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments. 相似文献
18.
N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%). 相似文献
19.
Shashikant U. Dighe Surya K. Samanta Shivalinga Kolle Sanjay Batra 《Tetrahedron》2017,73(17):2455-2467
An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y1 and Y2. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones. 相似文献
20.
In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates. 相似文献