A survey of patulin in 100 samples of commercial apple juice and 12 samples of apple food for children collected a t stores in Madrid (Spain) during 1992 was conducted. Patulin levels were determined by a dialysis diphasic membrane procedure using reversed-phase high-pressure liquid chromatography as analytical method. The results obtained in apple juice were as follows: patulin was detected in 82% of samples; 75% of the analyzed apple juice contained less than 10 p g L , and the maximum concentration found was 170 p a ; children's apple food samples were free of patulin. It is suggested that patulin should be used as a quality indicator of the apples employed in the elaboration of food and drink.

A simple and economical method has been developed for the determination of patulin in apple juice. The sample is extracted with ethyl acetate in a diphasic dialysis system, and the extract is cleaned up by elution from a Sep-Pak cartridge. Patulin is detected and determined by reversed-phase high-performance liquid chromatography using a Novapak C18 column and an ultraviolet detector. The lower detection limit is 1 microgram l-1 and the recovery is 85% at the 20 micrograms l-1 level.

A new membrane technique is described for the extraction of low molecular weight organic compounds from a wide range of substrates. With this system, the organic compounds of interest contained in the sample pass through the membrane toward the organic solvent, while other substances of higher molecular weight are excluded by the membrane. This procedure allows the extraction or the elimination of toxic substances with a yield of 90%.

An economical, fast, and simple method for the extraction and liquid chromatographic determination of chloramphenicol (CAP) in milk is described. CAP is extracted by using a recently developed membrane-based method named “diphasic dialysis.” CAP is detected and quantitated in the organic solvent used in dialysis without additional cleanup steps by reversed-phase liquid chromatography and UV detection (270 nm). The determination imit of CAP in milk was about 5 μg/L, although as little as 1 μg/L could be detected under optimal working conditions.

Partial migration is one of the most widespread migratory strategies among taxa. Investigating the tradeoff between environmental/social factors -tness and energetic consequences -is essential to understand the coexistence of migratory and resident behaviours. Here, we compiled eld monitoring data of wintering population size and telemetry data of 25 migrant and 14 resident Egyptian Vultures Neophron percnopterus to analyse how environmental and social factors modulate resident population size, compare tness components (i.e., survival and reproduction), and energetic consequences between migratory and resident individuals across wintering and non-wintering seasons. We observed that food availability positively correlated with the wintering population size and that subadult birds increased linearly with censused adult birds. Residents exhibited higher survival probabilities, but lower breeding activity and higher energy expenditure, less ight e ciency, and lower activity due to shorter winter-day lengths. On the contrary, migratory birds showed lower survival but more breeding attempts but spent less energy and ew more e ciently at longer distances, bene tting from longer days in African wintering quarters. These results suggest that anthropogenic food mediated social attraction could modulate population dynamics and promote residency. Food availability may bene t resident individuals enhancing their survival which may offset higher energy expenditure. Migrant birds, on the contrary, may compensate for the higher costs in terms of survival by a reduction in the energy cost, which may bene t future breeding. Our results offer new insights to understand how species bene t from one strategy or another and that the coexistence of both migratory forms is context-dependent.