Solid-phase microextraction for bioconcentration studies according to OECD TG 305

An important aim of the European Community Regulation on chemicals and their safe use is the identification of (very) persistent, (very) bioaccumulative, and toxic substances. In other regulatory chemical safety assessments (pharmaceuticals, biocides, pesticides), the identification of such (very) persistent, (very) bioaccumulative, and toxic substances is of increasing importance. Solid-phase microextraction is especially capable of extracting total water concentrations as well as the freely dissolved fraction of analytes in the water phase, which is available for bioconcentration in fish. However, although already well established in environmental analyses to determine and quantify analytes mainly in aqueous matrices, solid-phase microextraction is still a rather unusual method in regulatory ecotoxicological research. Here, the potential benefits and drawbacks of solid-phase microextraction are discussed as an analytical routine approach for aquatic bioconcentration studies according to OECD TG 305, with a special focus on the testing of hydrophobic organic compounds characterized by log KOW > 5

Microfibers for juice analysis by solid-phase microextraction.

In view of the interest in analyzing volatile compounds by SPME, the following five microfibers were tested, polydimethylsiloxane; polyacrylate; polydimethylsiloxane/divinylbenzene; carboxen/polydimethylsiloxane, and carbowax/divinylbenzene, to select the one which presents the best performance for the adsorption of the volatile compounds present in the headspace of acid lime juice samples. Sample stabilization time variations (30 and 60 minutes) were assessed as well the addition of NaCl to the samples. It was verified that the chromatogram with the most adsorbed volatile compounds was obtained with PDMS/DVB microfiber at 30 minutes and the addition of 0.2 g NaCl

Headspace analysis of natural yoghurt using headspace solid phase microextraction : a thesis presented in partial fulfilment of the requirements for the degree of Master of Philosophy in Food Technology at Massey University (Turitea Campus), Palmerston North, New Zealand

The Solid Phase Microextraction (SPME) method was originally developed to extract volatile and semivolatile compounds from wastewater samples but has since been applied to flavour compounds in foods and beverages. Research using the HS-SPME in related areas such as cheese and skim milk powder has been carried out but, to date, no work has been done on yoghurt flavours. The main objective of this study was to devise a methodology for the Headspace Solid Phase Microextraction (HS-SPME) technique to investigate and quantify six flavour analytes in natural, set yoghurts made from recombined milk. The relevant literature was reviewed and from it, a research proposal for this work on yoghurts was drawn. The first step in analysing and quantifying the yoghurt volatiles was to set up a working methodology for the HS-SPME method. The 100 μm polydimethylsiloxane (PDMS) fibre was chosen along with 20 minutes being the optimum fibre adsorption time. General equipment, materials and methods used throughout this thesis are also detailed. The external standard (ES) method was used to calibrate the GC and quantify the analyte concentrations in this study. The internal standard (IS) method was not used as a quantitative tool in this study. Once the HS-SPME methodology had been set up for the analysis of yoghurts, the classical Static Headspace (SH) method was compared with the HS-SPME method for extraction efficiency. The results suggested that the two methods were complementary in that the SH method extracted the more volatile compounds (acetaldehyde, acetone and 2-butanone) whereas, the HS-SPME method extracted the semi- to non-volatile compounds (ethanol, diacetyl and acetoin) more readily. However, the HS-SPME was found to be the more sensitive and effective method of the two techniques tested. The next step in the thesis was to investigate the presence of the six analytes in milk and cultured yoghurt. The effects of the sample matrix, fat levels and incubation on the volatile concentrations were also examined. The results suggested that the six analytes were inherently present in milks but at low concentrations. No conclusive effects were found for the sample matrix, fat levels and incubation. However, it was evident that fermentation of the milks using bacterial starter cultures resulted in a large increase in some of the volatiles being investigated. Following this, the effects of fat levels, storage time and storage temperature on the six volatiles in yoghurts were examined. The results indicated that significant fat level effects were only seen for diacetyl and acetoin, while temperature effects were only observed for ethanol. In both trials, only general trends for the analytes concentrations were drawn because the data varied from day to day. The results suggested that most of the compounds decreased with time except for diacetyl, which seemed to increase. The final part of this study looked at applying the devised HS-SPME methodology to a series of commercial yoghurts as a preliminary trial, with a view to investigating a potential application for the HS-SPME method. Fourteen commercial yoghurts were analysed and the six analytes quantified. The data obtained was analysed using Principle Component Analysis (PCA), which divided the yoghurts into groups based on their analyte concentrations. From these groupings, eight yoghurts were selected and fresh samples were analysed using HS-SPME and PCA. This was carried out parallel with an untrained consumer panel, which had to distinguish differences between the yoghurts in a series of triangle tests by smelling the headspace on opening the yoghurt containers. The conclusions drawn were that, unlike the HS-SPME method with PCA, the average consumer could not differentiate the yoghurts based on smell alone. PCA also showed that the HS-SPME results obtained were fairly reproducible. In conclusion, the HS-SPME method was shown to be a useful analytical technique, which can be used to analyse and quantify flavour compounds in natural, set yoghurts. This area of investigation has a lot of scope, with the results from this study providing a basis or starting point for further investigations in this area. Future studies may lead to potential applications for the HS-SPME method, one of which may be quality control where correlation of sensory data with HS-SPME analytical data is required

Application of direct bioautography and SPME-GC-MS for the study of antibacterial chamomile ingredients

The isolation and characterization of antibacterial chamomile components were performed by the use of direct bioautography and solid phase microextraction (SPME)-GC-MS. Four ingredients, active against Vibrio fischeri, were identified as the polyacetylene geometric isomers cis- and trans-spiroethers, the coumarin related herniarin, and the sesquiterpene alcohol (-)-alpha-bisabolol

Honey volatiles as a fingerprint for botanical origin: a review on their occurrence on monofloral honeys

Honeys have specific organoleptic characteristics, with nutritional and health benefits, being highly appreciated by consumers, not only in food but also in the pharmaceutical and cosmetic industries. Honey composition varies between regions according to the surrounding flora, enabling its characterization by source or type. Monofloral honeys may reach higher market values than multifloral ones. Honey's aroma is very specific, resulting from the combination of volatile compounds present in low concentrations. The authentication of honey's complex matrix, according to its botanical and/or geographical origin, represents a challenge nowadays, due to the different sorts of adulteration that may occur, leading to the search for reliable marker compounds for the different monofloral honeys. The existing information on the volatiles of monofloral honeys is scarce and disperse. In this review, twenty monofloral honeys and honeydews, from acacia, buckwheat, chestnut, clover, cotton, dandelion, eucalyptus, fir tree, heather, lavender, lime tree, orange, pine, rape, raspberry, rhododendron, rosemary, strawberry tree, sunflower and thyme, were selected for volatile comparison purposes. Taking into consideration the country of origin, the technique of isolation and analysis, the five main volatiles from each of the honeys are compared. Whereas some compounds were found in several types of monofloral honey, and thus not considered good volatile markers, some monofloral honeys revealed characteristic volatile compounds independently of their provenance.Funding: SFRH/BD/117013/2016, UID/AGR/00690/2019, UID/AMB/50017/2019, MED (UIDB/05183/2020), FEDER, PT2020 PACompete 2020info:eu-repo/semantics/publishedVersio

Speciation without chromatography: Part I. Determination of tributyltin in aqueous samples by chloride generation, headspace solid-phase microextraction and inductively coupled plasma time of flight mass spectrometry

An analytical procedure was developed for the determination of tributyltin in aqueous samples. The relatively high volatility of the organometal halide species confers suitability for their headspace sampling from the vapour phase above natural waters or leached solid samples. Tributyltin was collected from the sample headspace above various chloride-containing matrices, including HCl, sodium chloride solution and sea-water, by passive sampling using a polydimethylsiloxane/divinylbenzene (PDMS/DVB)-coated solid-phase microextraction (SPME) fiber. Inductively coupled plasma time-of-flight mass spectrometry (ICP-TOFMS) was used for detection following thermal desorption of analytes from the fiber. A detection limit of 5.8 pg ml–1(as tin) was realized in aqueous samples. Method validation was achieved using NRCC PACS-2 (Sediment) certified reference material, for which reasonable agreement between certified and measured values for tributyltin content was obtained

Determination of pesticides in fruit and fruit juices by chromatographic methods. An overview

In order to combat a variety of pests, pesticides are widely used in fruits. Several extraction procedures (liquid extraction, single drop microextraction, microwave-assisted extraction, pressurized liquid extraction, supercritical fluid extraction, solid-phase extraction, solid-phase microextraction, matrix solid-phase dispersion, and stir bar sorptive extraction) have been reported to determine pesticide residues in fruits and fruit juices. The significant change in recent years is the introduction of the Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) methods in these matrices analysis. A combination of techniques reported the use of new extraction methods and chromatography to provide better quantitative recoveries at low levels. The use of mass spectrometric detectors in combination with liquid and gas chromatography has played a vital role to solve many problems related to food safety. The main attention in this review is on the achievements that have been possible because of the progress in extraction methods and the latest advances and novelties in mass spectrometry, and how these progresses have influenced the best control of food, allowing for an increase in the food safety and quality standards

Chromatography of beer

The objectives of the review are the collection, concise description and evaluation of the various chromatographic techniques used for the separation and quantitative determination of macro- and microcomponents present in beers

A method validation for simultaneous determination of phthalates and bisphenol A released from plastic water containers

Phthalates (or phthalate esters, PAEs) and bisphenol A (BPA) are widely used in various industries, particularly in the fields of cosmetics and packaging, and they increase the malleability and workability of materials. As a result of their use, some international health organizations have begun to study them. In this study, the authors developed a methodology for the simultaneous determination of dimethyl phthalate (DMP), diethyl phthalate (DEP), diisobutyl phthalate (DiBP); dibutyl phthalate (DBP), bis(2-ethylhexyl) phthalate (DEHP); di-n-octyl-phthalate (DnOP) and bisphenol A (BPA) from drinking and non-potable waters. The extraction of PAEs and BPA was performed using a solvent-based dispersive liquid-liquid microextraction (SB-DLLME) method. The analytical determination was performed using a gas chromatography-ion trap mass spectrometry (GC-IT/MS) analysis. The entire procedure was validated as recoveries were studied according to the volume and the extraction solvent used, pH, and ionic strength. Dynamic linearity ranges and linear equations of all the compounds were experimentally determined as well as the limit of detection (LOD) (1-8 ng mL-1) and the limit of quantification (LOQ) (5-14 ng mL-1), reproducibility, and sensitivity. The method was applied to 15 water samples (mineral water and tap water) for determining PAEs and BPA released from the plastic container. After the release simulation, four PAEs (i.e., DiBP, DBP, DHEP, and DnOP) were determined at very low concentrations (below 1.2 ng mL-1) in two water samples from (sport) bottles