固相微萃取和GC/MS分析JOB炸药老化释放气氛

采用3种不同吸附性能萃取头的固相微萃取器对JOB炸药在自然密封存放和加热老化一定时间后所释放出来的微量气氛进行了萃取吸附研究，采用GC／MS测试技术对其进行了定性分析。研究结果表明，固相微萃取装置对该炸药老化过程中释放的微量无机气体和有机挥发性组分具有选择性吸附和萃取浓缩作用，峰强度显示不同老化条件下放出的气体组分和含量具有不同的结果。初步探讨了老化释放气体的机理，JOB炸药老化放出的主要是一些合成溶剂、杂质等。     

Iron‐mediated lipid oxidation in 70% fish oil‐in‐water emulsions: effect of emulsifier type and pH

The objective of this study was to investigate the protective effect of five different emulsifiers on iron‐mediated lipid oxidation in 70% fish oil‐in‐water emulsions. The emulsifiers were either based on protein (whey protein isolate and sodium caseinate) or based on phospholipid (soy lecithin and two milk phospholipids with different phospholipid contents, MPL20 and MPL75). Lipid oxidation was studied at pH 4.5 and 7.0, and results were compared to lipid oxidation in neat fish oil. Results showed that all emulsions oxidised more than neat oil. Furthermore, emulsions prepared with proteins oxidised more at low pH than at high pH, and casein emulsions oxidised the least (Peroxide value (PV) at day 7 was 0.5–0.7 meq kg^?1). Among emulsions prepared with phospholipids, emulsions with MPL75 were the most oxidised followed by emulsions prepared with lecithin and MPL20. Thus, PV in MPL75 emulsions was 5.0–5.5 meq kg^?1 at day 7 compared with 0.9–1.9 meq kg^?1 in MPL20 emulsions.     

Analysis of odour‐active compounds of black mangrove (Avicennia germinans L.) honey by solid‐phase microextraction combined with gas chromatography–mass spectrometry and gas chromatography–olfactometry

The volatile compounds of Cuban black mangrove (Avicennia germinans L.) honey were analysed by solid‐phase microextraction (SPME) followed by gas chromatography–mass spectrometry and gas chromatography–olfactometry. A total of 66 compounds were positively identified in this product for the first time. Application of the aroma extract dilution analysis in a novel approach, which consisted of carrying out successively dilutions of the honey sample with a synthetic honey before the SPME, revealed 17 odour‐active areas in the flavour dilution factor range of 32–1024. On the basis of the quantitative data and odour thresholds, odour activity values (OAV; ratio of concentration to odour threshold) were calculated. Sixteen compounds showed OAVs >1, among which dimethyl sulphide, 3‐methyl butanal, 2‐methylbutanal, heptanal, octanal, phenylacetaldehyde, (Z)‐linalool oxide, (E)‐linalool oxide, nonanal, hotrienol, isophorone, lilac aldehyde A, 1‐nonanol, decanal, 4‐vinyl‐2‐methoxyphenol and (E)‐β‐damascenone showed the highest values and should be considered as the most odour‐active compounds, particularly (E)‐β‐damascenone, nonanal and decanal.     

Characterisation of volatile compounds of farmed soft‐shelled turtle (Pelodiscus sinensis) by solid‐phase microextraction and the influence of matrix pH on the release of volatiles

Although farming and consuming of soft‐shelled turtle has been practised for centuries, the aroma‐impact compounds in the meat have not been determined. Furthermore, matrix pH, usually changing during processing and storage stage, was rarely investigated for the influence on volatile profiles. To these aims, soft‐shelled turtle meat was subjected to different pH conditions and the potential volatile compounds were analysed under different extraction conditions by headspace solid‐phase microextraction (HS‐SPME). A total of forty‐three volatiles were identified; in which, nonanal, (E, E)‐2, 4‐heptadienal, octanal, decanal, hexanal, (E)‐2‐nonenal, heptanal, 1‐octen‐3‐ol and o‐xylene were assigned as aroma‐impact compounds by high relative odour activity value (ROAV). Overly basic or acidic pH significantly (P < 0.05) facilitated the release of volatiles under moderate extraction conditions. The total volatilisation increased by 30.1% to 298% in pH‐shifted samples, while the highest one was found in pH 2 or pH 11. However, the results of principal components analysis (PCA) demonstrated that increased extraction time or temperature hindered the pH enhancement.     

Extraction and reliable determination of acrylamide from thermally processed foods using ionic liquid-based ultrasound-assisted selective microextraction combined with spectrophotometry

Acrylamide (AAm) is a carcinogenic chemical that can form in thermally processed foods by the Maillard reaction of glucose with asparagine. AAm can easily be formed especially in frequently consumed chips and cereal-based foods depending on processing conditions. Considering these properties of AAm, a new, simple and green method is proposed for the extraction of AAm from thermally processed food samples. In this study, an ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate, [Bmim][BF₄]) as extractant was used in the presence of a cationic phenazine group dye, 3,7-diamino-5-phenylphenazinium chloride (PSH⁺, phenosafranine) at pH 7.5 for the extraction of AAm as an ion-pair complex from selected samples. Under optimum conditions, the analytical features obtained for the proposed method were as follows; linear working range, the limits of detection (LOD, 3S_b/m) and quantification (LOQ, 10S_b/m), preconcentration factor, sensitivity enhancement factor, sample volume and recovery% were 2.2–350 µg kg^?1, 0.7 µg kg^?1, 2.3 µg kg^?1, 120, 95, 60 mL and 94.1–102.7%, respectively. The validity of the method was tested by analysis of two certified reference materials (CRMs) and intra-day and inter-day precision studies. Finally, the method was successfully applied to the determination of AAm levels in thermally processed foods using the standard addition method.     

Electronic nose and GC–MS analysis of volatile compounds in Tuber magnatum Pico: Evaluation of different storage conditions

The characteristic aromatic composition of white truffles (Tuber magnatum Pico) determines its culinary and commercial value. However modifications of truffle organoleptic proprieties occur during preservation. A study of headspace of white truffles by using Electronic nose (E-nose), gas chromatography–mass spectrometry (GC–MS) and sensory analyses was performed. Truffles were stored at different conditions for 7 days: +4 and +8 °C wrapped in blotting paper or covered by rice or none of the above. Headspace E-nose measurements and sensory analyses were performed each day. Statistical multivariate analysis of the data showed the capability of E-nose to predict sensorial analysis scores and to monitor aroma profile changes during storage. Truffle’s volatile molecules were also extracted by headspace solid phase microextraction technique and separated and identified by GC–MS. Partial Components Analysis of data was performed. E-nose and GC–MS results were in agreement and showed that truffle storage in paper at +8 °C seemed to be the best storage condition.     

Pseudo stir bar sorptive microextraction fiber using nanoparticles reinforcedsol–gel for the determination of Co(II) and Cd(II) ions in wastewaters

In this work a newly semi polar extraction phase of carboxylated multiwalled carbon nanotube (MWCNTs) reinforced sol-gel immobilized polypropylene hollow fiber was prepared by low temperature hydrothermal process. It is coupled with flame atomic absorption spectroscopy was employed in the extraction and determination of cobalt and cadmium ions in wastewaters. The main factors influencing the pre-concentration and extraction of the metal ions have been examined in detail. Detection limits obtained in this way for Co(II) and Cd(II) ions were 0.0186 and 0.024 ng mL^?1, respectively.     

HS-SPME结合GC-MS分析煎鸡蛋的挥发性风味成分

采用顶空固相微萃取与GC-MS联用方法对煎鸡蛋中挥发性成分进行提取与分析,考察萃取头、萃取温度和吸附时间对分析结果的影响,得到优化的顶空固相微萃取条件为:黑色萃取头(75μm Carboxen/PDMS),吸附温度75℃,吸附时间70 min。在优化的条件下分析,共鉴定出50种挥发性风味成分,其中,醛类16种(40.588%)、含氮化合物14种(23.639%)、醇类8种(7.156%)、烃类3种(4.800%)、酚类及杂环化合物3种(1.755%)、酮类3种(0.868%)及含硫化合物3种(0.563%)。鉴定出含量较高(相对质量分数大于2.5%)的物质有:2,5-二甲基吡嗪、3-甲基丁醛、2-甲基吡嗪、壬醛、苯甲醛、反,反-2,4-癸二烯醛、辛醛、2-甲基丁醛、反-2-癸烯醛、3,7-二甲基-1,6-辛二烯、1-辛烯-3-醇。     

Solid-Phase Microextraction (SPME) of Pyrazines in Model Reaction Systems

Headspace solid-phase microextraction (HS-SPME) combined with gas chromatography (GC) was used for isolating and analysing pyrazines formed in a model system. This system consisted of an aqueous mixture of glucose, glycine and sodium hydroxide. Pyrazine formation was accelerated by heating in a microwave oven. Results were compared with our earlier ones using conventional techniques for isolation of pyrazines. HS-SPME-GC showed several advantages over traditional methods. The method is rapid, sensitive, easy to use and reproducible. Headspace and liquid of the model reaction were extracted and the results obtained using headspace sampling showed good agreement with the methylene chloride extraction method. In all cases, coefficients of variation of 5% or lower were obtained when the SPME extraction time was consistent.