Marilena Musci

Contribution of Dynamic Headspace GC-MS Analysis of Aroma Compounds to Authenticity Testing of Honey.

Abstract The volatile profiles of 43 authentic honey samples of different botanical and geographical origins were obtained by means of gas chromatography–mass spectrometry. A qualitative analysis of the volatile compounds identified was performed in order to assess the marker compounds (if/when existing) for both botanical and geographical origin. The results seem to indicate the existence of certain marker compounds for the floral origins assessed (e.g. acacia, chestnut, eucalyptus, heather, lavender, lime, rape, rosemary and sunflower). Also such compounds for two geographical origins (e.g. Denmark and England) seem to exist and possible marker compounds could also be found for the honeys from The Netherlands, Spain and Portugal.

Overview of the applications of liquid chromatography–mass spectrometry interfacing systems in food analysis: naturally occurring substances in food

Abstract This paper reviews applications of different LC–MS techniques for the analysis of natural compounds in foods. Specific examples of substances discussed are lipids, oligosaccharides, vitamins, flavonoids and related substances, phenolic compounds, glucosinolates, and other miscellaneous naturally occurring compounds in food products. LC–MS is a powerful technique in food analysis and especially for analysis of complex mixtures, where additional analytical information is required to confirm positively the identity of the separated compounds or few separations are obtained. Among the interfacing systems used to couple LC with MS, the newly developed electrospray/ionspray mass spectrometric liquid interface offers undoubted advantages in terms of sensitivity and capability to analyze large, thermally labile and highly polar compounds; in addition, tandem MS techniques are useful for structural elucidation studies.

Spectrophotometric and coulometric detection in the high-performance liquid chromatography of flavonoids and optimization of sample treatment for the determination of quercetin in orange juice.

The capabilities of spectrophotometric and electrochemical detection techniques were investigated for the high-performance liquid chromatographic determination of flavonoids. Liquid chromatographic analyses were performed on eleven compounds belonging to three different classes of flavonoids: flavanone glycosides, flavone and flavonol aglycones. Separation of all compounds examined was carried out under reversed-phase conditions on a C18 narrow-bore column for UV detection, whereas for electrochemical detection, a C18 standard-bore column was used. UV analyses were carried out at 280 nm for flavanones and at 265 nm for flavones and flavonols, whereas controlled-potential coulometric measurements were performed using a porous graphite electrode. Analytical performances of the methods were compared in terms of linearity, limits of detection (LODs) and precision. Linearity over two orders of magnitude and LODs at low-ppm levels (0.06-1 mg/l) were demonstrated for all techniques considered. Instrumental precision in terms of relative standard deviation was found to be between 0 and 5% for the liquid chromatography (LC)-UV system and between 0.6 and 10% for the LC-electrochemical detection (ED) system. The methods developed were applied to the analysis of flavanones and flavonols in a real sample, such as an extract of orange juice. Even though quercetin glycoside is mostly present in orange juice as rutin, other different glycosides of this flavonol could be present; on this basis, the hydrolysis of all glycosides to aglycone allows one to obtain more accurate data on the flavonol concentration in orange juice. To avoid sample degradation and to increase extraction efficiency, quercetin hydrolysis was optimized using a central composite design to investigate the effects of acid concentration and hydrolysis time on extraction recovery.

Applications of liquid chromatography-mass spectrometry interfacing systems in food analysis : pesticide, drug and toxic substance residues

This paper reviews applications of different LC-MS techniques for the determination of xenobiotic substances in foods. Specific examples of contaminants discussed are pesticides, herbicides, insecticides and drugs; concerning toxic substances, mycotoxins, phycotoxins, cyanobacterial toxins, mutagenic and heterocyclic amines and beta-carbolines, arsenic, tin and inorganic halogen compounds, packaging materials and various epoxy resins are considered. Advantages and limitations are outlined for the different LC-MS interfacing systems (particle beam, thermospray, atmospheric pressure ionization with electrospray, ionspray and heated pneumatic nebulizer). The impact of developments in instrumental analysis on methodology and the limitations of the various LC-MS methods are discussed. Further, the coupling of LC with element-selective detection systems such as inductively coupled plasma mass spectrometry is discussed, with emphasis on speciation of trace toxic elements in foods.

Rapid Fluorimetric Method to Detect Total Plasma Malondialdehyde with Mild Derivatization Conditions

Malondialdehyde (MDA), an oxidation product of polyunsaturated fatty acids, is used as an in vivo marker to assess lipid peroxidation in diseases such as atherosclerosis and diabetes (1)(2)(3)(4). In biological matrixes, MDA is measured after derivatization with thiobarbituric acid (TBA) (5). Because TBA reacts with many other aldehydes (6), results are expressed as TBA-reactive substances (TBARS). Several problems are associated with TBARS analysis, in particular, low reproducibility and a lack of specificity that leads to overestimations. To overcome these difficulties, more specific methods have been proposed that require sample pretreatment to precipitate proteins and extract MDA-reactant adducts (6)(7)(8)(9). This additional step is time-consuming and adversely affects precision. The aim of the present study was to develop a rapid and sensitive method to measure MDA in plasma, avoiding sample pretreatment. Tetraethoxypropane (TEP), TBA, and bilirubin were obtained from Fluka. Fatty acid-free bovine serum albumin (BSA), Total Protein Reagent, and Protein Standard were from Sigma, and 2,2′-azobis(2-amidinopropane) (ABAP) was from Wako. We prepared an aqueous stock solution of 1 mmol/L TEP. A 10 μmol/L MDA solution was obtained by diluting TEP in 0.1 mol/L HCl. A 0.025 mol/L TBA solution was prepared daily by dissolving TBA in water. BSA solutions were prepared in 0.1 mol/L HCl. To remove protein-bound MDA, BSA solutions were heated at 80 °C for 1 h and dialyzed for 3 days against 0.1 mol/L HCl in a 3500-Da cutoff dialysis membrane (Spectrapore; Spectrum Medical Industries). The actual protein concentration was verified using the Total Protein Reagent Kit. A 50 mmol/L ABAP solution was prepared in water. Six MDA solutions ranging from 0.05 to 0.5 μmol/L were prepared by diluting the 10 μmol/L stock solution with 0.1 mol/L HCl. Triplicate solutions were used to obtain a dose–response …

Innovative sol-gel coatings for solid-phase microextraction. Development of fibers for the determination of polycyclic aromatic hydrocarbons at trace level in water.

Innovative solid-phase microextraction coatings synthesized by sol-gel technology were developed for the determination of environmental pollutants, i.e. polycyclic aromatic hydrocarbons at trace level in water. The fibers obtained, based on the use of (3-aminopropyl)triethoxysilane and diethoxydiphenylsilane were characterised in terms of film thickness, porosity, thermal stability and pH resistance. An excellent thermal stability was obtained in the case of diethoxydiphenylsilane-based coating, with a negligible weight loss until 400 degrees C. A very good fiber-to-fiber and batch-to-batch repeatability was also obtained with RSD lower than 6% using a mixture of aromatic hydrocarbons in the low ng/l range. Finally, the capabilities of the developed coating for sampling polycyclic aromatic hydrocarbons in water at trace levels were proved obtaining limits of detection about twofold lower than those achieved by using the commercially available polydimethylsiloxane 7 microm fiber.

Improved determination of chlorophenols in water by solid-phase microextraction followed by benzoylation and gas chromatography with electron capture detection

SummaryA rapid method for the determination of chlorophenols in drinking water by solid-phase microextraction and gas chromatography with electron capture detection was developed and validated. A fused silica fiber coated with a 65 μm thick stationary phase of poly (dimethylsilox-ane)/divinylbenzene was used to extract chlorophenols after performingin situ derivatisation with pentafluorobenzoyl chloride in the polymeric coating. Validation was carried out in terms of limits of detection (LOD), limits of quantitation (LOQ), linearity and precision.In situ derivatisation and the choice of a fiber with more affinity towards the derivatised analytes gave LODs in the 0.005–0.8 μgL−1 range which are lower values than those reported in previous work using poly(dimethylsiloxane) or poly(acrylate) fibers. Linearity was statistically verified over one order of magnitude for each compound. The production of chlorophenols as disinfection by-products in the treatment of drinking water with chlorine was studied over a period of eight days: mono-, di-and trichlorophenols were detected and quantitated.

Use of experimental design for the purge-and-trap-gas chromatography–mass spectrometry determination of methyl tert.-butyl ether, tert.-butyl alcohol and BTEX in groundwater at trace level

An efficient method for the simultaneous determination of methyl tert.-butyl ether, tert.-butyl alcohol, benzene, toluene, ethylbenzene and xylene isomers in groundwater by purge-and-trap-gas chromatography-mass spectrometry was developed and validated. Experimental design was used to investigate the effects of temperature of extraction, time of extraction and percentage of salt added to the water samples. Regression models and desirability functions were applied to find the experimental conditions providing the highest global extraction yield. Validation was carried out in terms of limits of detection (LOD), limits of quantitation (LOQ), linearity and precision. LOD values ranging from 2.6 to 23 ng l(-1) were achieved, whereas linearity was statistically verified over two orders of magnitude for each compound. Precision was evaluated testing two concentration levels. Good results were obtained both in terms of intra-day repeatability and intermediate precision: RSD% lower than 4.5% at the highest concentration and lower than 13% at the lowest one were calculated for intra-day repeatability. A groundwater sample suspected of contamination by leaking underground petroleum storage tanks was analysed and some of the analytes were detected and quantitated.

Atmospheric pressure chemical ionization liquid chromatography/mass spectrometry in cholesterol oxide determination and characterization

An atmospheric pressure chemical ionization liquid chromatography/mass spectrometry (APCI-LC/MS) system was evaluated for the analysis of cholesterol oxidation products (COPs). High performance liquid chromatography separation of these compounds was performed under reversed-phase chromatographic conditions at 1 mL/min flow rate. Useful mass spectra for confirmation and quantitation purposes were obtained with positive-ion detection. The influence of several parameters, such as the temperature of the heated nebulizer interface, the voltage applied to the orifice and to the ring electrode on the mass spectra of the analytes, was studied and optimized in order to obtain the best sensitivity. Linearity, sensitivity and precision of the method were determined operating in the selected-ion monitoring mode. Detection limits were in the range 0.2–0.8 ng for all the compounds with linear calibration graphs in the 0.1–10 mg/L concentration range. The method was applied to the quantitative analysis of COPs in lyophilized beef preparations, and results were compared with those obtained using LC/UV and LC/MS with particle beam interface.

HPLC analysis of fat-soluble vitamins on standard and narrow bore columns with UV, electrochemical and particle beam MS detection

SummaryThe application of different detection techniques; UV, electrochemical (ED) and particle beam-mass spectrometry (PB-MS) for the high-performance liquid chromatography analysis of fat-soluble vitamins were studied. Separation of all compounds examined was performed using both C8 standard-bore and narrow-bore columns for UV and MS detection, whereas in the case of HPLC-ED, a C8 standard-bore column only was used. Detector responses were studied in terms of linear range, detection limit and precision. The HPLC methods with UV, PB-MS and electrochemical detection were applied to the assay of vitamins A and E in an infantformula, powdered-milk sample. Recovery studies showed good results both for vitamins A and E, within-run precision being 2–4% for LC-UV and LC-ED techniques. In addition, excellent aggrement between the results obtained with the detection systems explored was found.