千瓦级微波等离子体质谱仪研究水体中锰元素

为了使微波等离子体电离源更好地用于分析水溶液中金属元素,本研究基于改进型千瓦级微波等离子体（KMP）电离源耦合线性离子阱质谱仪（LTQ MS）,在新型进样系统（Nafion H2SO4）下,研究水体中锰元素的质谱行为。锰元素的千瓦级微波等离子体质谱（KMP MS）特征谱图不同于传统的电感耦合等离子体（ICP MS）获得的特征信号,这可能有助于金属元素分析。使用KMP LTQ MS法分析水体中锰的络合物阴离子,证实锰的络合物阴离子是由流经KMP源中心管的水溶液在等离子体火焰中电离产生的,如NO3-。此外,解释了主要离子在多步碰撞诱导解离过程中特征碎片的形式,并在优化的条件下,使用锰的络合物阴离子二级质谱特征离子评估锰的检测限（LOD）为033 μg/L,线性动态范围涵盖至少2个数量级,在0~100 μg/L之间。因KMP源无Ar背景干扰,未来可将其与四极杆质谱结合,能够为水质检测提供新方法。     

基于电喷雾电离源质谱仪系统的八电极线性离子阱性能研究

八电极线性离子阱在前期的理论模拟研究中取得了较好的质量分析性能,为验证理论模拟结果,选择其中最优的结构参数,设计、加工并组装了八电极线性离子阱实物,以此为基础搭建电喷雾电离源质谱测试系统。在传统射频电压施加模式下,测试八电极线性离子阱的分析性能。当扫描速度为765 u/s时,八电极线性离子阱获得离子峰的半峰宽可达0.3 u,对应利血平（m/z 609）的质量分辨率为2 030。当分析浓度为10 mg/m3的利血平样品时,对应的质谱峰信噪比可达45.8。本文进一步研究了扫描速度对质量分辨率和灵敏度的影响,实现了离子碰撞诱导解离,分析了不同浓度的25羟基维生素D2标准样品,线性动态范围可达4个数量级。结果表明,八电极线性离子阱具有良好的分析性能,可为结构简化线性离子阱的研究提供全新思路,推动小型化离子阱质谱仪的研究进展。     

WiMAX系统基于CID的压缩机制研究

分析了WiMAX系统分段MAC PDU报头及子头格式,提出了一种利用分段MAC PDU头保留位和子头保留位对CID进行编码的压缩算法,实现对分类之后冗余信息的有效压缩,给出了详细的算法流程,并对无线信道模型和CID映射表进行了量化分析。仿真结果表明,提出的压缩机制达到了满意的压缩效果。     

Rapid determination of organophosphorous pesticides in leeks by gas chromatography–triple quadrupole mass spectrometry

A rapid multi-residue method was developed for the determination of 20 organophosphorous pesticide residues in leeks by gas chromatography coupled to triple quadrupole mass spectrometry (GC–QqQ-MS/MS). The method was based on the modified QuEChERS sample preparation method. After microwave pre-treatment, leek samples were extracted with acetonitrile containing acetic acid 0.1% and cleaned by dispersive solid phase extraction. The QqQ analyser acquired data in selected reaction monitoring (SRM) mode. Recoveries of 20 organophosphorous pesticides ranged from 81.0% to 109.4% with the relative standard deviations (RSD) below 10.4%. The limits of detection (LODs) were 0.07–1.5 μg/kg. The limits of quantitation (LOQs) ranged from 0.25 to 5 μg/kg. Ten leek samples were analysed for method application.     

Co-occurrence of aflatoxins and ochratoxin A in cereal flours commercialised in Turkey

In this study, we aim to determine co-occurrence of aflatoxins (AFs) and ochratoxin A (OTA) in cereal flours commercialised in Corum, Turkey. One hundred cereal flours were checked for target fungal metabolites between the years 2011 and 2013. The samples were analysed by high-performance liquid chromatography with fluorescence detection (HPLC-FLD) after immunoaffinity column (IAC) clean-up procedure. The method was successfully validated in accordance to European Union guidelines acceptance criteria for specificity, linearity, sensitivity, trueness and repeatability. All the results are well below the maximum limits specified in the EU legislation. AFs were detected neither wheat flour nor rice flour samples, while 66.7% of maize flours contained AFs with maximum concentration of 1.12 μg kg⁻¹. OTA was present in 26.7% of wheat flour, 41.7% of maize flour and 18.8% of rice flour samples, with mean levels of 0.247, 0.218 and 0.154 μg kg⁻¹, respectively. The co-occurence of AFs and OTA was found in 9 maize flour samples.     

Moiety and linker site heterologies for highly sensitive immunoanalysis of cyprodinil in fermented alcoholic drinks

Cyprodinil is a new-generation anilinopyrimidine fungicide widely used in crop protection and frequently found in fruits. In this study, novel derivatives of cyprodinil with linker site heterologies were synthesized and employed in order to produce antibodies with enhanced affinity. Moreover, moiety-heterologous haptens were designed and prepared for assay sensitivity improvement. Two competitive enzyme-linked immunosorbent assays for the analysis of this active substance were developed using direct and indirect formats, achieving IC₅₀ values around 0.15 μg/L. Analytical figures of merit and usability of the optimized assays were evaluated with wine and cider as model food processed matrices. The obtained recoveries were from 90% to 120%, and the limit of quantification was in the 1–5 μg/L range. Finally, a monitoring study (n = 150) was performed to estimate the occurrence and the concentration of cyprodinil in commercial wine and cider products from different origins. We found that 28% of the analysed wine samples contained cyprodinil residues at levels higher than 5 μg/L.     

Antimicrobial activities of red wine-based formulations containing plant extracts against Escherichia coli O157:H7 and Salmonella enterica serovar Hadar

We evaluated the antimicrobial activities of three red wine based plant extract/plant essential oil (EO) formulations: olive extract powder/oregano EO, apple skin extract powder/lemongrass EO, and green tea extract powder/bitter almond EO, and their formula permutations against the foodborne pathogens Escherichia coli O157:H7 and Salmonella enterica serovar Hadar. The following parameters that were expected to affect antimicrobial activity were evaluated: pH (3.6 or 7.0), temperature (4, 22, and 37 °C), incubation time (0, 5, 30, and 60 min) and bacterial load (∼10⁴ or ∼10⁹ bacteria/ml). The formulations with oregano, lemongrass, or bitter almond EO inhibited the growth of both pathogens at acidic pH with bacterial loads of ∼10⁴ or ∼10⁹ bacteria/ml. At neutral pH, the formulations were less effective. Although all the 3-component formulations were fast acting; showing significant activity in less than 5 min, only the activity of the lemongrass-containing formulation markedly increased with longer incubation times from 0 to 60 min. Activity also increased for all 3-component formulations with increasing temperature from 4 °C to 37 °C, although the activity of the lemongrass formulation appeared to level off at 22 °C. Of the tested formulations, the lemongrass EO formulations, at pH 3.6, appeared to be the most effective against the tested pathogens, especially against Salmonella. The most active formulations merit evaluation for antimicrobial efficacy in liquid and solid food.     

Determination of heavy metals in selected black sea fish species

Heavy metals can be accumulated by marine organisms thought a variety of pathways, including respiration, adsorption and ingestion. The levels of heavy metals are known to increase drastically in marine environment through mainly anthropogenic activities. Fish are good indicators for the long term monitoring of metal accumulation in the marine environment. The aim of this study was to determine the levels of Cd, As, Hg, Pb, Zn and Cu in edible part and gill of seven most consumed Bulgarian fish species collected from north-east coast of Black Sea. These fish species are sprat (Sprattus sprattus sulinus), Mediterranean horse mackerel (Trachurus mediterraneus ponticus), Black sea gobies (Neogobius melanostromus), shad (Alosa pontica), Atlantic bonito (Sarda sarda), bluefish (Pomatomus saltatrix) and grey mullet (Mugil cephalus). The fish samples were collected during 2010. The analytical determination of As, Cd, Pb, Zn and Cu were performed by using flame and graphite furnace atomic absorption spectrometry after microwave digestion procedure. The total mercury determination was determined using a direct mercury analyzer (DMA-80). The metal concentration of analyzed elements was highest in the gill for all fish species. The maximum metal concentration was measured for Cu (1.40 mg kg⁻¹ w.w), Zn (11 mg kg⁻¹ w.w) and Pb (0.08 mg kg⁻¹ w.w) in muscle tissues of shad and sprat. The edible part of horse mackerel has the maximum value for Hg (0.12 mg kg⁻¹ w.w) while Atlantic bonito predominantly accumulates As (1.10 mg kg⁻¹ w.w). The analytical results obtained from this study were compared within acceptable limits for human consumption set by various health institutions.     

Biopreservation potential of lactic acid bacteria from Andean fermented food of vegetal origin

Microbial fermentations have long represented a way of natural biopreservation of raw materials, which frequently originated new food products. Among them, traditionally fermented products still manufactured by native populations all around the world are source of lactic acid bacteria (LAB) strains with high biotechnological potential. LAB are food grade microorganisms and therefore a good alternative to chemicals to be applied in food preservation. A total of 130 LAB isolates recovered from “chicha” and “tocosh”, traditional fermented Andean products of vegetal origin, were screened for antimicrobial activities against spoiler fungi Meyerozyma guilliermondii CECT 1021 (synonym Pichia guilliermondii), Penicillium roqueforti CECT 2905^NT, Aspergillus oryzae CECT 2094^NT and Aspergillus niger CECT 2807 as well as against foodborne pathogens Escherichia coli O157:H7 CECT 5947, Listeria innocua CECT 910^T and Salmonella enterica subsp. enterica serovar Typhi CECT 4138. LAB isolates represented nine species and four genera that exhibited a general inhibition of food pathogens and were also active against A. oryzae and M. guilliermondii while a poor inhibition of A. niger and P. roqueforti was produced. Antifungal activity of cell free supernatants (CFS) from seven selected strains grown in MRS was confirmed against toxigenic fungi Aspergillus parasiticus CECT 2681, Penicillium expansum CECT 2278 and Fusarium verticilloides CECT 2987 and also on the three foodborne bacteria included in the study. Phenyllactic and 3,5-Di-O-caffeoylquinic acids were identified as the predominant bioactive compounds in CFS by QuEChERS extraction with LC-MS-LIT detection approach. Four out of seven strains free of antibiotic resistances involving L. plantarum M5MA1 and M9MM1 from chicha and L. fermentum T3M3 and Lc. mesenteroides T1M3 from tocosh showed high potential to be used as biopreservatives in food applications.     

A preliminary study on a novel sea water disinfection process by a peroxy-acid compound to complement and improve the microbial depuration of clams (Ruditapes philippinarum)

A novel sea water disinfection process to complement and improve the microbial depuration of clams (Ruditapes philippinarum) was tested by employing a potassium peroxymonosulfate (MPS)-based product. A broad and multidisciplinary approach was used to achieve a quite complete pattern of the potential suitability of this innovative MPS-based disinfectant treatment to improve the microbiological quality of cultured Manila clams. The biocidal activity was evaluated against the Vibrio spp. population naturally associated with sea water and against viral nervous necrosis virus (VNNV), genus Betanodavirus, the most threatening among the viral pathogens of marine finfish.The novel depuration process by sea water potassium MPS-based disinfection set up and tested in the present study (1000 ppm disinfectant for 3 h) greatly reduced the tested bacteria and viruses in the sea water column, being able to counteract the restarting of microorganisms during the depuration process. Furthermore, the microbiological quality of harvested clams with respect to their Vibrio spp. load improved after the 1000 ppm disinfectant 3 h treatment. The potential use of this treatment was strengthened by the absence of effects on clam health and welfare. This issue was assessed by direct observation as indicated by Regulation EC 853/2004, and by the unaltered biochemical parameters, cortisol level and histological pattern. The absence of undesired side-effects and surfactant residues in the edible flesh was also ascertained. The whole of data suggests that the proposed treatment may potentially represent an innovative strategy to face, in a quite easy and feasible way, still unresolved matter of concern in clam commercialization. However, further studies are required to check if the 3 h treatment positive effect on clams is preserved during the subsequent out of water maintenance.