1,721,014 research outputs found
Liquid chromatography/tandem mass spectrometric methodologies for the determination of aflatoxins as sensitive markers of food safety and quality
No full textHPLC-CHIP coupled to a triple quadrupole mass spectrometer for carbonic anhydrase II quantification in human serum
No full textA method for carbonic anhydrase II (CA II) absolute quantification in human serum is presented. This method is based on high-performance liquid chromatography (HPLC)-Chip microfluidic device incorporating a nanoelectrospray source interfaced to a triple quadrupole mass spectrometer. The fraction containing CA II was isolated by preparative reversed-phase HPLC, and peptides obtained from the tryptic digest of the protein mixture were separated by the HPLC-Chip system. The multiple-reaction monitoring acquisition mode of a selected suitable CA II peptide and peptide internal standard allowed the selective and sensitive determination of a CA II. Absolute recovery of the method was 52 +/- 12%, while analytical recovery was 81 +/- 10%. For the eight samples analyzed, the matrix effect was found to be only -14 +/- 6%. A comparison among three regression lines type which were obtained by external calibration, matrix-matched calibration, and standard addition method, respectively, demonstrated that the first one is adequate in obtaining good accuracy and precision. Method quantification limit for CA II in serum was estimated to be 2 fmol/mL. CA II mean concentration in sera from eight healthy subjects was found to be 56 pmol/mL (relative standard deviation 24%)
Liquid Chromatography/Tandem Mass Spectrometric Confirmatory Method for Determining Aflatoxin M1 in Cow Milk. Comparison Between Electrospray and Atmospheric Pressure Photoionization Sources
No full textA liquid chromatography/electrospray (ESI)–tandem mass spectrometric method for the measurement of aflatoxin M1 (AFM1) in milk is described. Milk sample after protein precipitation with acetone was cleaned-up with a Carbograph-4 cartridge. Performances of the ESI source were compared with those of the atmospheric pressure photoionization source (APPI). Although a method quantification limit (MQL) of 6 ng/kg could be achieved operating with APPI source with respect to an MQL of 12 ng/kg with ESI, all the other performances being similar, then ESI was preferred as being more robust and widespread at present
Determination of type-B fumonisin mycotoxins in maize and maize-based products by LC/MS/MS using a QqQlinear ion trap mass spectrometer.
No full textA sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for determining the type B fumonisin mycotoxins in corn-based foodstuffs is described. Fumonisins FB1 and FB2 were extracted from a 1 g sample by homogenization with acetonitrile/water (75:25, v/v, 50mmol/L formic acid, 25 mL final volume) and the extract was defatted on C-18 phase. Volumes of 5 mL of crude extracts were cleaned up on Carbograph-4 cartridges. The final solution was analyzed by HPLC with electrospray ionization mass spectrometry in positive ion mode using multiple reaction monitoring with a QqQ linear ion trap mass spectrometer. Recoveries for spiked corn-based foodstuffs ranged from 91-105% (RSD% less than or equal to 8%), and method detection limits were less than or equal to 2ng/g for FBI and less than or equal to 1 ng/g for FB2. Two different spiking levels were tested (5000 and 100 ng/g for FB1, 1000 and 20 ng/g for FB2). Quantitation was achieved by an external calibration procedure using matrix-matched standards, with diclofenac added post-cleanup as internal standard for the LC/MS/MS analyses. Calibration curves showed linearity in the concentration range 0.005-5ng/muL of final extract (0.992 less than or equal to R-2 less than or equal to 0.995). Two other fumonisins, FB3 and FB4, were identified in naturally contaminated samples of corn meal using an information-dependent acquisition protocol that looped three experiments, including neutral loss scan, enhanced resolution scan, and enhanced product ion scan. FB3 and FB4 quantitation was estimated as peak area ratios relative to the FB2 response in view of the lack of both standards. This work also includes an application of the present LC/MS/MS method to some maize and maize-based product samples (corn meal, cornflakes and popcorn) collected from Italian stores. FB1 and FB2 contamination levels exceeding the European Union recommendation were found in 8 out of 15 corn meal samples
Identification and mass spectrometric characterization of glycosilated flavonoids in young Triticum durum plants by LC-MS/MS
No full textIstruzione elementare e formazione dei maestri a Milano prima dell'Unità: permanenze e mutamenti
No full textIl saggio ripercorre il processo di professionalizzazione dei maestri e delle maestre nella Lombardia tra Sette e Ottocento, concentrando l'attenzione sulla realtà di Milano. In particolare, nell'età della Restaurazione si gettarono solide basi in tal ambito. Le riforme operate in questo periodo attecchirono grazie al lavoro già svolto dalla precedente politica scolastica teresio-giuseppina e napoleonica. Negli anni preunitari, nelle città lombarde, si portarono a compimento la laicizzazione e la professionalizzazione del corpo docente elementare e si verificò un incremento qualitativo dell'efficienza della scuola elementare, dovuto a una significativa innovazione didattica
Identification and Mass Spectrometric Characterization of Glycosilated Flavonoids in Triticum durum Plants by High Performance Liquid Chromatography with Tandem Mass Spectrometry
No full textA mass spectrometric method for extensive detection and semi-quantitative determination of flavonoid glycosides in stem and leaves of young Triticum durum plants is presented. About 100 g of sample were Iyophilized and ground, and the compounds of interest were then extracted, cleaned-up, and fractionated using high-performance liquid chromatography (HPLC). Tandem mass spectrometry analyses were performed using a quadrupole-linear ion trap instrument with an information-dependent data acquisition (IDA) protocol that looped two experiments, enhanced MS scan and enhanced product ion scan. Various glycoconjugates, which are all derivatives of only four flavones, apigenin, luteolin, chrysoeriol and tricin, were identified and belong to the following categories: 7 monoglycosides, 31 diglycosides, 15 triglycosides and 1 tetraglycoside. Among these some acylated glycosides were found. Tricin derivatives are present exclusively as O-glycosides, while apigenin and luteolin are present always as C-glycosides. Semi-quantitative estimation was performed by using the monoglycoside and diglycoside of quercetin as internal standard
Development of a multiresidue method for analysis of major Fusarium mycotoxins in corn meal using liquid chromatography – tandem mass spectrometry
No full textA sensitive and reliable liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) method has been developed to determine, in a single run, eight trichothecenes, three fumonisins, zearalenone and alpha-zearalenol, in corn meal samples. LC and MS conditions were varied to find the best compromise in terms of sensitivity and separation. An acceptable compromise was obtained using a C-18 column thermostatted at 45 degrees C and a mobile phase gradient of methanol/water with 10 mmol/L formate buffer (pH 3.8). A multiple reaction monitoring program, in which fumonisins and trichothecenes (except nivalenol and deoxynivalenol) are acquired in positive ESI as [M+H](+) or [M+NH4](+), and all other compounds in negative ESI, was developed to match appropriate retention time windows. Sample preparation used a simple homogenization of the corn meal sample with acetonitrile/water (75:25, v/v) followed by extraction on a C-18 cartridge and clean-up on a cartridge containing graphitized carbon black. Method detection limits were in the range 2-14 ng/g, with the exception of nivalenol (27 ng/g), deoxynivalenol (40 ng/g) and 15-acetyldeoxynivalenol (30 ng/g). Good accuracy (recoveries 81-104%) and precision (RSD 4-11%) were obtained by performing calibration using a spiked analyte-free extract
Do plasma proteins distinguish between liposomes of varying charge density?
No full textCationic liposomes (CLs) are one of the most employed nonviral nanovector systems in gene therapy. However, their transfection efficiency is strongly affected by interactions with plasma components, that lead to the formation of a "protein corona" onto CL surface. The interactions between nanoparticles entering the body and biomolecules have an essential role for their biodistribution. Because the knowledge of proteins adsorbed onto vector surface could be useful in the screening of new, more efficient and more biocompatible liposomal formulations, the behavior of three CLs with different membrane charge densities was investigated. The proteins of the three coronas were identified by nano-liquid chromatography-tandem mass spectrometry, and quantified with label-free spectral counting strategy. Fibrinogen displayed higher association with CLs with high membrane charge density, while apolipoproteins and C4b-binding protein with CLs with low membrane charge density. These results are discussed in terms of the different lipid compositions of CLs and may have a deep biological impact for in vivo applications. Surface charge of nanoparticles is emerging as a relevant factor determining the corona composition after interaction with plasma proteins. Remarkably, it is also shown that the charge of the protein corona formed around CLs is strongly related to their membrane charge density. (C) 2012 Elsevier B.V. All rights reserved
Ultra-high-performance liquid chromatography-tandem mass spectrometry for the analysis of free and conjugated natural estrogens in cow milk without deconjugation
No full textA sensitive liquid chromatography/electrospray ionization-tandem mass spectrometry method for the determination of free and conjugated estrogens in cow milk is described.
Milk samples were diluted with water, then extracted and cleaned-up by solid-phase extraction using graphitized carbon black as adsorbent material, without any enzymatic cleavage, derivatization and/or protein precipitation step. Two fractions were collected (free and conjugated estrogens) and analyzed separately. Mass spectrometry analysis was performed in negative ion mode using selected reaction monitoring acquisition mode.
For all compounds the coefficients of determination R2 ranged between 0.9892 and 0.9997. Analytical recoveries were in the range of 86-109% for free estrogens and 85-118% for conjugates, with relative standard deviations below 10%, and method detection limit ranged between 3 and 80 ng L-1. Finally, the developed method was used to determine the presence of free and conjugated estrogens in six retail milk samples (five cow milk samples and one goat milk sample) and one goat milk sample provided by a local shepherd. Estrone was found to be the major free estrogen present in commercial milk samples, and estrone 3-sulfate showed the highest concentration among the target conjugated estrogens. Estriol was also observed in some analyzed milk samples, but the concentrations were always below the limit of quantification
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