1,721,028 research outputs found
Solid-phase microextraction and on-fiber derivatization for assessment of mammalian and vegetable milks with emphasis on the content of major phytoestrogens
Full text linkA new solvent-free method for the simultaneous determination of some major phytoestrogens (equol, enterodiol, daidzein, genistein, glycitein) in different commercial milks (cow, goat and soy-rice) was developed. After solid phase microextraction, performed by direct immersion of a 65 mu m-polydimethylsiloxane-divinylbenzene fiber in diluted (1:100 with 0.2% formic acid - 30% sodium chloride) milk samples (18 degrees C for 20 min under stirring), a direct on-fiber silylation with N,O-bis (trimethylsilyl) trifluoroacetamide) containing 1% trimethylchlorosilane (70 degrees C for 20 min) was performed prior to gas chromatography-mass spectrometry analysis. Since the target compounds were determined as aglycones, the hydrolytic removal of the aglycone from the glycosides was performed. The method permitted the determination of the target analytes in all the considered milk samples as well as the detection of some major amphipathic fats indicating that the approach could potentially be applied in the future for further applications, such as milk profiling
Ultra-Trace Determination of Sudan I, II, III, and IV in Wastewater by Solid-Phase Microextraction (SPME) and on-Line Solid-Phase Extraction (SPE) with High-Performance Liquid Chromatography (HPLC)
Full text linkTwo extraction/preconcentration methods are reported for the high-performance liquid chromatography (HPLC) determination of Sudan I, II, III, and IV in wastewater at trace (μg/L) and ultra-trace (ng/L) levels for the first time. The first approach, based on solid-phase microextraction (SPME), allows sub-μg/L determination of Sudan I and II, while Sudan III and IV are not detectable at these levels due to strong binding to dissolved organic matter. For Sudan I and II, the linearity was tested in the range from 0.5 to 50 μg/L and limits of detection (based on a signal-to-noise ratio of 3) and quantification (based on a signal-to-noise ratio of 10) of 0.2 and 0.5 μg/L, respectively, were estimated for both dyes. The on-line solid-phase extraction (SPE) using a C18 based enrichment precolumn was employed in the second approach. The only sample pretreatment employed was a required centrifugation step to remove suspended solids. In this case, the linearity was verified in the range from 50 to 500 ng/L for Sudan I, II, and III and from 100 to 500 ng/L for Sudan IV. The detection limits for a sample volume of 20 mL were on the order of 20 ng/L for Sudan I, 25 ng/L for Sudan II and III, and 30 ng/L for Sudan IV
Determination of Polycyclic Aromatic Hydrocarbons (PAHs) in Coffee Samples by DI-SPME-GC/MS
Full text linkRoasting is a crucial and essential step to produce quality coffee. However, it could lead to the formation of toxic and
suspected carcinogenic or procancerogenic compounds, such as polycyclic aromatic hydrocarbons. In this work, a simple and
easily automatable green procedure based on solid-phase microextraction coupled with gas chromatography for the analysis
of acenaphthene, anthracene, benzo[ghi]perylene, benzo[a]pyrene, chrysene, fluoranthene, fluorene, naphthalene, and pyrene,
in dark roasted and decaffeinated commercial coffees, was developed. The method was optimized for the determination of
the analytes both in solid samples, such as ground coffee or coffee grounds, and liquids, such as espresso coffee, using a
polyacrylate-coated fused silica fiber (85 μm) by direct immersion. The performance of the analytical method, developed
in terms of sensitivity, reproducibility, and recoveries, proved to be suitable for the applications. Among the 9 polycyclic
aromatic hydrocarbons investigated in the selected coffees, chrysene and pyrene were the most representative congeners
with values ranging from undetectable to 95.6 ± 11 ng/g for chrysene and from undetectable to 404.7 ± 42.0 ng/g for pyrene.
Benzo[a]pyrene was detected in two samples of dark roasted coffee which therefore had the highest toxicity/carcinogenicity
in terms of toxic equivalent. The estimated limit of detection for benzo[a]pyrene in ground coffee and coffee grounds was
9.0 ng/g. About 30% of the PAHs were transferred to the infusion while the remaining part was retained by the coffee grounds
Bio-sourced polyolefins
No full textIn the last 5 years (2010–2015) the worldwide annual production of plastics surpassed the figure of 300 Mt; more than 80% of the plastic market deals with the production, transformation and end use of polyolefins. Plastics are a fundamental component of everyday life providing cost effective, light and disposable tools which find application in different fields. The increased concerns about the depletion of fossil reserves, the greenhouse gas emissions and feedstock costs cause bio-derived polyolefins are emerging rapidly as valid alternative to the fossil fuel based counterpart. In this review the drop-in synthesis of conventional olefins is reviewed and the properties of some novel bioderived polyolefins are presented and discusse
Effect of a Chitosan-Based Packaging Material on the Domestic Storage of “Ready-to-Cook” Meat Products: Evaluation of Biogenic Amines Production, Phthalates Migration, and In Vitro Antimicrobic Activity’s Impact on Aspergillus Niger
No full textThe consumption of "ready-to-cook" foods has been experiencing rapid expansion due to modern lifestyles, and they are often sold in economical multipacks. These foods necessitate packaging that maintains their quality for extended periods of time during home storage once the original packaging is opened. This study evaluates a chitosan-based film derived from low- and high-molecular-weight (MW) chitosan in acetic acid without synthetic additives as an alternative packaging material for "ready-to-cook" beef burgers. The burgers were stored at 8 degrees C after being removed from their sales packaging. A commercial polyethylene (PE) film designed for food use, devoid of polyvinylchloride (PVC) and additives, served as the reference material. The production of six biogenic amines (BAs), indicative of putrefactive processes, was monitored. Additionally, the release of four phthalates (PAEs), unintentionally present in the packaging films, was assessed using solid-phase microextraction coupled with gas chromatography/mass spectrometry (SPME-GC/MS). Microbiological tests were conducted to investigate the antimicrobial efficacy of the packaging against Aspergillus Niger NRR3112. The results showed that the chitosan-based films, particularly those with low MW (LMW), exhibited superior meat preservation compared to the PE films. Furthermore, they released PAEs below legal limits and demonstrated the complete inhibition of fungal growth. These findings highlight the potential of chitosan-based packaging as a viable and effective option for extending the shelf-life and maintaining the quality of "ready-to-cook" meat products during domestic storage
Simultaneous determination of free mycophenolic acid and its glucuronide in serum of patients under mycophenolate mophetil therapy by ion-pair reversed-phase liquid chromatography with diode array UV detection.
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Measurement of squalene in olive oil by fractional crystallization or headspace solid phase microextraction coupled with gas chromatography
Full text linkSqualene is the most abundant component in the unsaponifiable fraction of olive oil with strong antioxidant properties. Its concentration in olive oils varies between 0.2 and 16.2 g/kg depending on the cultivar(s) used. The propose of this work was to determine the effectiveness of two different extraction methods for squalene determination by gas chromatography (GC) coupled to a flame ionization detector (FID) or to mass spectrometry (MS). In a first approach, oil samples were dissolved in methanol/acetone mixture 7:3 (v/v) and triglycerides separated by fractional crystallization at −20°C. The organic layer was removed, reduced to dryness and the residue reconstituted in n-heptane (containing squalane as external standard) and analyzed by GC-FID. A headspace (HS) solid phase microextraction (SPME) GC-MS method has been also developed in order to have an environmentally friendly (i.e. solventless) extraction procedure. The linear range investigated with both methods was 1.0-10 g/kg. Within-day and between days precision values, expressed as RSD%, were 4 and 7% (GC-FID), and 3 and 6% (GC-MS), respectively. The limit of detection (LOD) at a signal-to-noise (S/N) ratio of 3 were 0.019 (GC-FID) and 0.003 (GC-MS) g/kg; the limit of quantification (LOQ) calculated at S/N = 10 were 0.063 (GC-FID) and 0.008 (GC-MS) g/kg, well below the typical squalene concentration levels found in olive oils. The obtained percentage recoveries were 70 ± 2 (GC-FID) and 98 ± 3 (GC-MS), and were not concentration dependent. The potential of the method has been demonstrated by the analysis of several different olive oil samples produced from different cultivars and different locations
Detection of hazelnut oil in extra-virgin olive oil by analysis of polar components by micro-solid phase extraction based on hydrophilic liquid chromatography and MALDI-ToF mass spectrometry
No full textThe oil polar fraction may have a great potential for the characterization of vegetable oils and for the individuation of
adulterations. In particular, adulteration of extra-virgin olive oil (EVOO) with hazelnut oil (HO) is one of the most difficult
ones to detect due to the similar composition as regards triacylglycerol, total sterol and fatty acid profile. A new micro-solid
phase extraction (μ-SPE) procedure based on hydrophilic liquid chromatography (HILIC) micro-columns was developed for the
selective extraction and enrichment of polar compounds from EVOO and HO beforematrix-assisted laser desorption ionization
time-of-flight mass spectrometry (MALDI-ToF-MS) analysis. The method permits a simple and fast qualitative analysis of the
polar fraction of the oils under study; furthermore, somepeaks (such as them/z ions 496.39, 520.46 and 522.47) were found tobe
present only inHO, indicating that they could be diagnostic for the presence ofHOin EVOO. In order to verify the potential of the
method for the individuation of this adulteration,EVOOwas progressively adulteratedwith variable quantities ofHO, subjected
to the HILIC enrichment and finally to MALDI-ToF-MS analysis; the detection of adulteration was possible up to the level of
5%. Eventually, diagnostic polar compoundswere identified as lysophosphatidylcholine (LPC) (16 : 0/0 : 0), LPC (18 : 2/0 : 0), LPC
(18 : 1/0 : 0) by means of capillary liquid chromatography-electrospray ionization-quadrupole-ToF-MS (CapLC-ESI-Q-ToF-MS)
analysis
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