Capillary headspace - gas chromatography for the characterization of the flavour of fresh vegetables

Summary Static headspace sampling combined with gas chromatography using open-tubular (capillary) columns for the characterization of the flavour of raw vegetables and some vegetable products is described. In order to avoid alteration of the composition of the volatiles, the sample was thermostated for a short time only. Although equilibrium between vapour and sample was not established the reproducibility of such conditions is demonstrated. Typical chromatograms are given; the most characteristic compounds present were identified by mass spectrometry. Enlarged text of a poster presented at the Twelfth International symposium on Capillary Chromatography, September 11–14, 1990, Kobe, Japan     

A preliminary study of soft cheese degradation in different packaging conditions by 1H-NMR

This preliminary work deals with the influence of packaging on the degradation of an Italian soft cheese studied by NMR. The NMR profiles of aqueous cheese extracts were acquired as a function of time during storage of cheese inside and outside the original package. From the NMR spectra 15 metabolites are quantified and used in a kinetic degradation model and in a multivariate algorithm in order to evaluate the changes in the metabolic composition of cheese stored under different conditions.     

Microwave-assisted extraction and determination of cyanuric acid residue in pet food samples by liquid chromatography-tandem mass spectrometry

Cyanuric acid (CYA) is attracting more attention due to its potential toxicity. In the present work, microwave-assisted extraction method in combination with liquid chromatography-tandem mass spectrometry (LC-MS/MS) was proposed for the determination of CYA in pet food samples. Among different solvents, diethylamine-acetonitrile-water mixture (1:5:4, v/v) was found to be the best one as the extractant due to the strong polarity of CYA in the pet food. An internal standard, (13) C(3) -labeled CYA, was used in the extractions. The separation was performed on a MERCK ZIC HILIC column (150 mm × 2.1 mm id, 5 μm) with gradient elution of 20 mM ammonium acetate solution-acetonitrile. CYA was well retained (Rt = 5.10 min) and eluted with good peak shape. The method could respond linearly with CYA at concentrations from 1.0 to 50 ng/mL with a quantification limit of 0.25 mg/kg. The intra- and inter-day precision was less than 4.0% and the recovery of the assay was in the range of 90.4-108.1%. In the analysis of practical spiked pet food samples, the new method yielded satisfactory results. Due to its simplicity and accuracy the straightforward method is particularly suitable for routine CYA detection.     

Analysis of Phytoestrogens in Foods Using Sol-Gel Enzyme Columns for Sample Preparation

The paper describes the development and application of a new method in phytoestrogen analysis using sol-gel cellulase columns for sample preparation. Enzyme columns were produced by entrapping commercially available cellulase by slightly modifying a simple sol-gel procedure previously optimised for immobilising antibodies. Quantitative hydrolysis of both lignan and isoflavone glycosides was achieved within 5 min. Immobilisation of the enzyme enabled the elimination of enzyme-born impurities prior to analysis. Sol-gel cellulase columns could be used for at least 15 cleavage cycles over the investigated period of two months.     

Microcomputers and linear programming—Feedstock revisited

The paper describes the application of linear programming to the feedstock mix problem. The algorithm is programmed on a microcomputer. The study covers the formulation of the problem, its solution and successful implementation. System performance and cost are discussed and extensions to the work are suggested.     

肉制品中群勃龙、勃地酮和甲氧酪胺的检测方法

介绍肉制品中群勃龙、勃地酮的液相色谱-质谱联用检测方法和甲氧酪胺的气相色谱-质谱联用检测方法。样品经β-葡萄糖醛酸甙酶水解后,群勃龙、勃地酮用甲醇-乙酸铵缓冲液提取,C18和Silica固相萃取柱净化,用LC-MS-MS法分析。甲氧酪胺样品经高氯酸溶液提取,SCX固相萃取柱净化,MBTFA衍生化处理,GC-MS法分析。两种方法均采用选择离子模式进行测定,群勃龙、勃地酮、甲氧酪胺选择的子离子(m/z)分别为:253、228、197、159;269、173、135、121;205、233、246、359,外标法定量。群勃龙、勃地酮、甲氧酪胺的检出限分别为0.3、0.3、2μg/kg,方法回收率为72%~99%,线性范围为5~800μg/kg。     

Volatile polydimethylcyclosiloxanes in the ambient laboratory air identified as source of extreme background signals in nanoelectrospray mass spectrometry

Polydimethylcyclosiloxanes, an almost ubiquitous air contaminant, can interfere with nanoelectrospray analysis. The sensitivity of nanoelectrospray to these volatile air contaminants was demonstrated in this study. The intensity of the interfering ion signals caused by these compounds can be decreased by changing the position of the nanoESI needle and almost completely suppressed by applying a flow of pure nitrogen around the needle and the sample cone. The nitrogen flow causes a slight shift in charge distribution, but does not influence the sensitivity for peptide detection.     

Modelling and control of natural convection in canned foods

In this paper we study mathematically an industrial problemrelated to sterilization processes involving heat transfer bynatural convection. We give results of existence and regularityfor the solution of this problem. We recast the whole problemas an optimal control problem with pointwise constraints onthe state and the control in order to ensure the reduction ofmicroorganism concentration and the retention of nutrients,and to save energy. Finally, we give results on existence ofthe optimal solution and optimality conditions for its characterization.     

Application of liquid chromatography/quadrupole time-of-flight mass spectrometry (LC-QqTOF-MS) in the environmental analysis

This paper gives an overview of the potentials of liquid chromatography-hybrid quadrupole time-of-flight mass spectrometry (LC-QqTOF) in the environmental analysis. Examples of applications of QqTOF instruments for target analysis of pharmaceuticals and pesticides are presented and discussed, as well as applications aimed on the identification of unknown compounds present in environmental waters or on the elucidation of structures of biodegradation and photodegradation products. Specific issues such as uncertainty of mass measurement and quantitative performances are discussed in details.