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41.
Gas chromatography-mass spectrometry (GC-MS) and liquid chromatography with fluorescence detection (LC-FL) methods have been proposed for the determination of low level nitrite and nitrate in biological, food and environmental samples. The methods include derivatization of aqueous nitrite with 2,3-diaminonaphthalene (DAN), enzymatic reduction of nitrate to nitrite, extraction with toluene and chromatographic analyses of highly fluorescent 2,3-naphthotriazole (NAT) derivative of nitrite by using GC-MS in selected-ion-monitoring (SIM) mode and LC-FL. Nitrite and nitrate ions in solid samples were extracted with 0.5 M aqueous NaOH by sonication. The recoveries of nitrite and nitrate ions based on GC-MS and LC-FL results were 98.40% and 98.10% and the precision of these methods, as indicated by the relative standard deviations (RSDs) were 1.00% for nitrite and 1.20% for nitrate, respectively. The limits of detection of the GC-MS in SIM mode and LC-FL methods based on S/N = 3 were 0.02 and 0.29 pg/ml for nitrite and 0.03 and 0.30 pg/ml for nitrate, respectively. 相似文献
42.
H. Zhang Z. F. Chai W. Y. Qing H. C. Chen 《Journal of Radioanalytical and Nuclear Chemistry》2009,281(1):23-26
Cyclic neutron activation analysis method was conducted for determination of Se in food samples. High accuracy and good precision
were proved by analyzing certified reference materials (CRMs) of chicken (GBW10018), rice (GBW10010) and cabbage (GBW10014).
The detection limits for the three CRMs reached 0.16, 0.66 and 1.2 ng after 6 cycles at the 161.9 keV γ-peak from 77mSe, under a neutron flux of 9.0 × 1011 n cm−2 s−1 and the conditions of 30 s irradiation, 2 s decay, 30 s counting and 2 s waiting, significantly lower than those of conventional
neutron activation analysis without any cycles, which were 0.94, 3.6 and 4.3 ng, respectively. 相似文献
43.
Denise Huber Judith Rudolf Parisa Ansari Brigitte Galler Manuela Führer Christoph Hasenhindl Sabine Baumgartner 《Analytical and bioanalytical chemistry》2009,394(2):539-548
Blocking is an important step before an enzyme-linked immunosorbent assay (ELISA) can be performed. It reduces non-specific
binding to the microtiter plate to a minimum. For detecting food allergens by means of ELISA, the problem with protein blocking
solutions is obvious. The blocker might interfere with the antibodies of the assay and leads to false positive results. Therefore,
other blocking solutions are greatly needed. There are some alternatives like synthetic blockers or carbohydrates. Comparisons
of these different blocking agents, namely proteins, carbohydrates, and synthetic blockers, were made at different reaction
conditions. The incubation periods and temperatures were varied, as well as the pH. The best combinations were evaluated and
compared, in respect of their blocking efficiency. The two best non-proteinaceous blockers, i.e. polyvinylalcohol and Ficoll,
were subsequently applied to ELISA tests for the determination of α-casein and peanut. The study showed that Ficoll and PVA
did as well as BSA in buffer solution. Therefore, they can be considered as alternative blocking reagents for ELISA, especially
for the detection of food allergens. 相似文献
44.
《Operations Research Letters》2019,47(6):537-541
We investigate optimization models for meal delivery that do not involve routing. We focus on the simplest case, with a single restaurant and a single courier, and reduce it to the throughput maximization single machine scheduling problem, with release times and bounded slacks. In the meal delivery setting, slacks are small for QoS purposes and we indeed show that the scheduling problem can be solved in polynomial time when slacks are bounded. We discuss extensions to more couriers and restaurants. 相似文献
45.
Ma?gorzata Biniecka 《Trends in analytical chemistry : TRAC》2011,30(11):1756-1770
The investigation of odorants is not an easy task, which needs to be undertaken in the context of fit-for-purpose quality systems. To date, great attention has been paid to determination of the volatile fractions of odorants, since they are responsible for the attributes of global flavor [i.e. a combination of olfactory (aroma) and gustatory (taste) sensations produced by chemicals]. This kind of determination can be carried out by analytical techniques [e.g., gas chromatography (GC) combined with mass spectrometry and/or olfactometric GC]. Methods complementary to GC analysis are available, allowing assessment of the olfactory impact by an electronic nose (e-nose) or a panel of selected individuals. Also, we consider some innovative analytical techniques to study the effects of odorants in food during consumption. 相似文献
46.
L. Connolly 《Trends in analytical chemistry : TRAC》2011,30(2):227-238
Endocrine-disrupting chemicals (EDCs) are capable of interfering with normal hormone homeostasis by acting on several targets and through a wide variety of mechanisms. Unwanted exposure to EDCs can lead to a wide spectrum of adverse health effects, especially when exposure is during critical windows of development. Feed and food are considered to be among the main routes of inadvertent exposure to EDCs, so there is an important need for efficient detection of EDCs in these matrices.We describe in vitro bioassays that can complement current analytical chemistry in order to detect unwanted EDCs and describe their action, emphasizing assays that can measure effects on nuclear receptor signaling or hormone production. We outline both validated and unvalidated in vitro assays currently available in the scientific community for detecting and studying the effects of EDCs, and discuss their possible role in the food-safety context. We conclude by identifying gaps in the current battery of in vitro assays available for EDCs and suggest future possibilities for development and validation. 相似文献
47.
Isothermal calorimetry approach to evaluate shelf life of foods 总被引:7,自引:0,他引:7
48.
A. Baldan Adriaan M. H. van der Veen Daniela Prauß Angelika Recknagel N. Boley Steve Evans Derek Woods 《Accreditation and quality assurance》2001,6(4-5):164-167
Many proficiency tests are operated with a consensus value derived from the participants’ results. Apart from technical issues,
one of the reasons often mentioned is that proficiency tests operated with consensus values would be cheaper than those using
reference values obtained from a priori characterisation measurements. The economy of a proficiency test must of course be balanced by the need of the participants,
and the quality of the comparison in general. The proficiency tests selected in this study had both a reference value and
a consensus value, one of which was used for assessing the performance of the participating laboratories. In this work, both
a technical and an economical assessment of how the comparisons were operated is made. From the evaluation, it follows that
usually the use of consensus values does not necessarily reduce the costs of a proficiency test. However, frequently it may
be observed that the quality of the assessment of the laboratories is better with a reference value.
Received: 11 October 2000 Accepted: 3 January 2001 相似文献
49.
Recent advances in miniaturization of analytical systems and newly emerging technologies offer platforms with greater automation and multiplexing capabilities than traditional biological binding assays. Multiplexed bioanalytical techniques provide control agencies and food industries with new possibilities for improved, more efficient monitoring of food and environmental contaminants. This review deals with recent developments in planar-array and suspension-array technologies, and their applications in detecting pathogens, food allergens and adulterants, toxins, antibiotics and environmental contaminants. 相似文献
50.
E. Van Hoeck T. De Schaetzen C. Pacquet F. Bolle L. Boxus J. Van Loco 《Analytica chimica acta》2010,663(1):55-59
Benzophenone (BP) and 4-methylbenzophenone (4MBP) are photo-initiators that are generally used to cure ink on carton boards.In this contribution, a fast and reliable method for the determination of BP and 4MBP in breakfast cereals is described. The sample was extracted ultrasonically using a mixture of dichloromethane and acetonitrile (1:1), followed by a clean-up of the extract using solid phase extraction with a silica cartridge. Finally, the extract was analysed by GC-MSn. Benzophenone-d10 was used as internal standard. The presented method is validated in terms of linearity, recovery, repeatability and intra-laboratory reproducibility, specificity, limit of detection and limit of quantification. In conclusion, this method is able to detect both BP and 4MBP at very low concentrations (LOD = 2 μg kg−1) in breakfast cereals. 相似文献