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31.
A Pt electrode modified by a polypyrrole/poly(orthophenylenediamine) bilayer membrane able to entrap large molecules such as glucose oxidase was used to investigate (at 27°C and pH 7) the kinetics of ascorbic acid (AA) oxidation by hydrogen peroxide (H2O2 + AA → 2H2O + DAA) by following the H2O2 concentration as a function of time. The largely unmatched rejection characteristics of this device towards AA permitted it to operate even in the presence of high AA/H2O2 ratios, e.g. 1000: 1. Under these conditions, pseudo-first-order kinetic constant values ranging from 3.26 × 10−3 to 4.10 × 10−3 s−1 were obtained at [AA] = 2 mM and initial [H2O2] = 2 μM. The potential influence of the above reaction on sensitivity and reliability of H2O2-detecting biosensors in the presence of AA is discussed critically, taking into account also the recent, and sometimes conflicting, literature views on the problem. 相似文献
32.
Cosima D. Calvano Cristina De Ceglie Antonella Aresta Laura A. Facchini Carlo G. Zambonin 《Analytical and bioanalytical chemistry》2013,405(5):1641-1649
In the dairy industry one of the most common frauds is mixing high-value milk (sheep’s and goats’) with milk of lower value (cows’). This illegal practice has commercial, ethical, and serious sanitary consequences because consumers can be exposed to hidden allergens contained in the undeclared cows’ milk. Here, we investigated the possibility of using matrix-assisted laser-desorption/ionization (MALDI)-time of flight (TOF) mass spectrometry (MS) as a rapid, sensitive, and accurate technique for detection of milk adulteration by analysis of phospholipid profiles. Lipid extracts of pure raw milk, commercial milk, and binary mixtures of cows’ and goats’ milk and cows’ and sheep’s milk (the concentrations of each milk varied from 0 % to 50 %) were analyzed with α-cyano-4-chlorocinnamic acid as matrix. The abundance ratio of the ions at m/z 703 and m/z 706 was found to be species-correlated and was used as marker of cows’ milk in sheep’s and goats’ milk. Furthermore, the procedure could potentially be applied to cheese samples, because peaks at m/z 703 and 706 were also found in several commercial cheese samples. This approach proved to be an efficient, rapid, and inexpensive method of detecting milk fraud. Figure
MALDI-TOF MS analysis of intact phospholipid in milk mixtures 相似文献
33.
A new automated, high-throughput method for the determination of ochratoxin A (OTA) in human urine samples has been optimized and validated using solid-phase microextraction coupled to liquid chromatography-tandem mass spectrometry (SPME-LC-MS/MS). High-throughput was achieved by simultaneous preparation of up to 96 samples using multi-fiber SPME device and multi-well plates. A carbon-tape coating was chosen for the first time as the best extracting phase for this contaminant. The proposed method required only minimal sample pre-treatment to adjust sample pH to 3.0 using a dilution (1:1) with 0.5M phosphate-buffered saline. A simple gradient guaranteed a good chromatographic separation from matrix interferences in only 8min. Relative recovery (%), precision and linearity validation results met Food and Drug Administration acceptance criteria at three concentration levels (1, 10, and 50ng/mL), indicating excellent performance of the proposed method. Limits of detection and quantitation were 0.3 and 0.7ng/mL in urine, respectively. OTA determination in urine is a good marker for human exposure to this mycotoxin. It is also less invasive than blood analysis. This method is fully automated and the SPME technique is simpler, less time-consuming and cheaper compared with most widely adopted clean-up procedures for OTA extraction from urine. 相似文献
34.
The thermal quasi-adiabatic method and the non-adiabatic one are compared for the study of chemical kinetics. With thermistors as temperature-sensitive elements, and a very simple apparatus, moderately fast reactions (with t(1 2 ) down to 2 sec) and consecutive reactions can be followed, and mixtures analysed with good accuracy. The reproducibility is satisfactory over a wide range of experimental conditions. The calculation of the kinetic parameters, for both first-and second-order kinetics is very simple and requires no calibration of the system. Application of the technique to the study of the alkaline hydrolysis of some alkyl acetates is described. 相似文献
35.
36.
G. E. De Benedetto F. Catalano L. Sabbatini P. G. Zambonin 《Fresenius' Journal of Analytical Chemistry》1998,362(1):170-175
This paper is part of a systematic archaeometric investigation aimed at the characterisation of the pigments and related
materials (ligand, colour substrate) used in decoration of pottery excavated in the archaeological zone of Canosa (Puglia,
Italy). Shards found in thirteen different tombs have been analysed; in this paper samples exhibiting a white colouration
have been selected. Both surface (XPS) and bulk (FT-IR) spectroscopies were used which gave complementary information and
enabled white pigments to be divided into two groups. Moreover, X-ray diffraction was used in some cases to further support
some spectral assignments. The molecular specificity of FT-IR, when applied to the analysis of both pigments and ceramic body,
allowed the identification of the various constituents and, hence, provided indirect information on the end-use of the original
wares. The potential of the combined use of different spectroscopies to obtain valuable information on both painting materials
and technical aspects is shown.
Received: 5 December 1997 / Revised: 16 March 1998 / Accepted: 19 March 1998 相似文献
37.
Vergés JA Guinea F Galán J van Dongen PG Chiappe G Louis E 《Physical review. B, Condensed matter》1994,49(21):15400-15403
38.
D. Centonze A. Guerrieri C. Malitesta F. Palmisano P. G. Zambonin 《Fresenius' Journal of Analytical Chemistry》1992,342(9):729-733
Summary An amperometric glucose sensor is described; it is based on glucose oxidase immobilized in an overoxidized non-conducting polypyrrole membrane. The overoxidation process of polypyrrole produces a permselective, antifouling membrane capable of rejecting ascorbate, urate, acetaminophen and cysteine, as well as proteins and other surface active components typically present in serum. The amperometric assay of glucose in serum correlates well with an established routine procedure based on an enzymatic-colorimetric method. 相似文献
39.
Determination of triazines in soil leachates by solid-phase microextraction coupled to gas chromatography-mass spectrometry 总被引:1,自引:0,他引:1
A solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) method was developed for the evaluation of the leachability order of selected triazines (propazine, terbuthylazine, sebuthylazine, ametryn, prometryn and terbutryn) in soil/sediment samples (organic carbon content ranging from 0.19 to 0.42%), analysing fractions collected from a soil packed microcolumn elution experiments. The procedure is fast, simple, highly sensitive and solvent free. SPME-GC-MS was also employed for the quantitative determination of triazines in the soil leachate, since the method showed good recovery yield. Detection limits were always better than 1 ng ml(-1). The method was tested on a contaminated landfill top soil. Prometryn and ametryn were identified through their MS spectra and then quantified. Terbuthylazine was used to assess recovery. Results compared well with those obtained by solvent extraction followed by HPLC-UV detection. 相似文献
40.
An LC-ESI-MS (negative ions) method was developed for the determination of cyclopiazonic acid (CPA), a mycotoxin produced by many Aspergillus and Penicillium genuses, in milk samples. First, the acquisition parameters of the ESI mass spectrometer were optimised for deprotonated CPA and MS-MS measurements were performed, giving a fragmentation pattern. After this stage, LC separation was applied to milk extracts (with or without CPA spikes) by means of an aminic column, using the selective reaction monitoring (SRM) acquisition mode for MS detection. The CPA response was linear over three decades of concentration and an LOD of 5 ng mL(-1) was estimated; moreover, the extraction procedure produced almost quantitative recoveries of CPA from milk. Twenty different milk samples were analysed and three of them were found to be contaminated with CPA to various extents. 相似文献