Occurrence of PCBr in Ambient Air and Surface Soil in an Urban Site of Madrid

This article describes the temperature dependence of sixteen PCBs in ambient air from the relationship ln(C) = m + (1000/T) + b and the Clausius-Clapeyron equation from data obtained at an open urban area of Madrid. The study was applied to predice long/short range transport influence as PCB sources in a typical semi-urban ambient without the influence of industrialised or contaminated sites around. The present study also relate surface soil/ambient air data to characterise soil/air cycled seasonal behaviour in the observation site. Regarding both compartments, a comparison was done calculating fugacity quotients from one full year data.     

Aluminium speciation: Variations caused by the choice of analytical method and by sample storage

We have compared a new FIA method (M1) for aluminium speciation in natural waters and a manual one based on one of Driscoll's proposals (M2). In synthetic solutions, aluminium's fluoro complexes were measured as ‘labile monomeric AP (Al _i ) by M2, but not as ‘quickly reacting Al’ (Al _qr ) by M1. Aluminium's complexes with Nordic Reference Humic Acid were measured neither as Al _i nor as Al _qr , and the same result was obtained for Al's citrato complexes. After excluding aluminium's fluoro complexes from Al _i , the results of the two methods agreed well for soil leaching samples and fairly well for natural water samples. Detection limits: 10μg L^?1 (ca. 0.4 μM) for both methods. Sample throughputs: M1∶66 injections h^?1; M2∶5 samples h^?1. Repeatabilities (RSD) on natural water samples: M1∶0.6–5.8% and M2 0.7–4.6%. Sample storage studies on soil solutions (FIA method) indicated that storage effects were ‘sample type specific’. A sample with a low level of Al _qr and a high DOC level (P2A) was more sensitive to storage than one with a high [Al] _qr and a low [DOC] (P2B^*). The decrease in [Al] _qr was statistically significant after 10 h (P2A) and 24 h (P2B^*), respectively. After 3 days' storage, [Al] _qr had decreased by some 40% in P2A, while the decrease in P2B^* was less than 10% after 8 days. The results of this part of the study also emphasize the importance of careful method standardization in sample storage studies.     

Multiresidue analysis of pesticides in soil by gas chromatography with nitrogen-phosphorus detection and gas chromatography mass spectrometry

A rapid multiresidue method for the simultaneous determination of 25 fungicides and insecticides in soil was developed. Soil samples are extracted by sonication with a water-acetonitrile mixture, and the pesticides are partitioned into dichloromethane. Final determination was made by gas chromatography (GC) with nitrogen-phosphorus detection (NPD). Confirmation analysis of pesticides was carried out by GC-MS in the selected ion monitoring (SIM) mode. The identification of compounds was based on retention time and on comparison of the primary and secondary ions. The average recovery by the GC-NPD method obtained for these compounds varied from 68.5% to 112.1% with a relative standard deviation between 1.8% and 6.2%. The GC-NPD method presents good linearity over the range assayed 50-2000 microg/L, and the detection limit for the pesticides studied varied from 0.1 to 10.4 microg/kg. The proposed method was used to determine pesticide levels in soil samples from experimental greenhouse pepper cultivation.     

Effect of the type of frying culinary fat on volatile compounds isolated in fried pork loin chops by using SPME-GC-MS

The effect of the type of frying culinary fat (olive oil, sunflower oil, butter, and pig lard) on volatile compounds isolated from fried pork loin chops (m. Longissimus dorsi) was measured by SPME-GC-MS. Frying modified the fatty acid composition of lipids from pork loin chops, which tended to be similar to that of the culinary fat used to fry. Volatile compounds formed from the oxidation of fatty acids increased, such as aldehydes, ketones, alcohols, and hydrocarbons. Besides, each culinary fat used modified the volatile profiles in fried meat differently. Sunflower oil-fried pork loin chops presented the highest aldehyde aliphatic content, probably due to their highest content of polyunsaturated acids. Hexanal, the most abundant aldehyde in fried samples, presented the most elevated content in sunflower oil-fried pork loin chops. In addition, these samples presented more heterocyclic compounds from the Maillard reaction than other fried samples. Volatiles detected in olive oil-fried pork loin chops were mainly lipid-derived compounds such as pentan-1-ol, hexanal, hept-2-enal, nonanal, decanal, benzaldehyde, and nonan-2-one. Butter-fried pork loins were abundant in ketones with a high number of carbons (heptan-2-one, nonan-2-one, undecan-2-one, tridecanone, and heptadecan-2-one). Pig lard-fried pork loin chops presented some Strecker aldehydes isolated in only these samples, such as 2-methylbutanal and 3-(methylthio)propanal, and a sulfur compound (dimethyl disulfide) related to Strecker aldehydes.     

Effect of cis/trans isomerism of beta-carotene on the ratios of volatile compounds produced during oxidative degradation

beta-Carotene is, when cleaved, an important source of flavor and aroma compounds in fruits and flowers. Among these aroma compounds, the main degradation products are beta-ionone, 5,6-epoxy-beta-ionone, and dihydroactinidiolide (DHA), which are associated by flavorists and perfumers with fruity, floral, and woody notes. These three species can be produced by degradation of beta-carotene through an attack by enzyme-generated free radicals and a cleavage at the C9-C10 bond. This study investigated the influence of cis/trans isomerism at the C9-C10 bond on the production of beta-carotene degradation compounds, first with a predictive approach and then experimentally with different isomer mixtures. beta-Carotene solutions containing high ratios of 9-cis-isomers produced more DHA, suggesting a different pathway than for the transformation of all-trans-beta-carotene to ionone and DHA. These results are important in the search for financially viable processes to produce natural carotene-derived aroma compounds.     

Direct and highly species-specific detection of pork meat and fat in meat products by PCR amplification of mitochondrial DNA

Highly species-specific primers for pork D-loop mtDNA have been designed. Use of these and restrictive PCR amplification conditions has improved a reliable and rapid method for detecting a PCR-amplified 531 bp band from pork. It has been proved useful for detecting both pork meat and fat in meat mixtures, including those dry-cured and heated by cooking. Absence of response in PCR-amplified samples or mixtures from bovine, ovine, chicken, and human was also demonstrated. Furthermore, wild boar and pork samples can be also easily distinguished by a simple AvaII restriction analysis.     

Stability study of a sulfadimidine-containing medicated premix and its mixture with farm feed

The objective of this paper was to study the stability of a medicated premix and a medicated farm feed containing sulfadimidine as the active ingredient. The medicated premix is supplied as powdered form and administered orally after mixing with animal feed. The sulfadimidine analytical method described in United States Pharmacopoeia 23 cannot be used to carry out the stability study because of its lack of specificity for different degradation products. Therefore, a high-performance liquid chromatography method was developed to assay sulfadimidine. This method was optimized and validated for the stability study. According to International Committee Harmonization (ICH) guidelines, the samples were stored under long-term testing and accelerated conditions for the stability study of the premix and the medicated farm feed. Sulfadimidine degradation was not detected in either form under any of the conditions studied.     

Aluminium and uptake of base cations by tree roots: A critique of the model proposed by Sverdrup et al.

Sverdrupet al. (1992) proposed a model intended to evaluate effects of soil solution (Ca²⁺+Mg²⁺/Al³⁺ ratios on the uptake of Ca²⁺ and Mg²⁺ (here called base cations=BC) by tree roots. They considered the adsorption of BC on exchange sites on root surfaces to be a major step, and the competition between Al³⁺ and BC for exchange sites on roots to be crucial. Although this may certainly affect the rates of uptake, it will not exclude base cations from entering the root cells through ion channels or by carriers. Above all, the model overlooks important gradients in the rhizosphere, e.g. pH-gradients and root exudates, which have profound influences on the speciation of Al. One should instead consider modifying existing models accounting for processes in a buffered soil medium and handling gradients in the rhizosphere (e.g. Nye and Tinker, 1977). This would also require considerations on mycorrhizas and possible changes in the capacity for uptake of certain ions, which could be induced by deficiencies.     

Free radical generation assays: new methodology for accelerated oxidation studies at low temperature in complex food matrices

A novel method for the rapid screening of antioxidant efficacy and oxidative stability in food and feed matrices has been developed. The analyses are described as free radical generation (FRG) assays. The new procedure combines the use of azo-initiators with analytical equipment that is widely used for antioxidant research such as the oxidative stability instrument and the oxygen bomb. The use of initiators instead of high temperatures as a driving force to increase the rate of oxidation improves the correlation between the accelerated screening of foodstuffs and real shelf life. The improved correlation can be mainly explained by the fact that food products are analyzed in their original status, maintaining all interfacial phenomena of the food matrix. Furthermore, the lower temperature of analysis reduces differences between the reaction kinetics of the assay and those of the oxidation during actual shelf life. Consequently, the correlation between the accelerated analysis and shelf life is improved, particularly when compared to accelerated oxidation at high temperatures. The FRG assays could be used successfully to evaluate the efficacy of natural antioxidants in heat-sensitive food products such as emulsions and meat products. A good correlation was observed between the accelerated tests and the oxidation parameters obtained from standard shelf-life evaluation. It was possible to successfully compare the efficacy of several antioxidants and to predict shelf life for these heat-sensitive food matrices.     

SPME-GC-pyrolysis-AFS determination of methylmercury in marine fish products by alkaline sample preparation and aqueous phase phenylation derivatization

Characterization of a cost-efficient analytical method based on alkaline sample digestion with KOH and NaOH, followed by aqueous phase phenylation derivatization with NaBPh4 and solid phase microextraction (SPME) for the determination of methylmercury in typical fish-containing food samples commercially available in Hungary, is reported. The sample preparation procedure along with the applied SPME-GC-pyrolysis-AFS system was validated by measuring certified reference materials (CRM) BCR-464, TORT-2, and a candidate CRM BCR 710. To carry out an estimation of average Hungarian methylmercury exposures via marine fish and/or fish-containing food consumption, 16 commercially available products and 3 pooled representative seafood samples of-according to a previous European survey--the three most consumed fish species in Hungary, herring, sardines, and hake, were analyzed. Methylmercury concentrations of the analyzed samples were in the range 0.016-0.137 microg of MeHg g(-1) dry weight as Hg.