Circadian preferences and sleep in 15- to 20-year old Finnish students.

PURPOSE: Despite progress in research concerning adolescent and young adult sleep and circadian preferences, several aspects have remained unexamined. This study explored gender and diurnal rhythms in relation to several sleep-related factors: sleep duration, bedtime, wake-up time, tiredness, sleepiness, and optimal subjective sleep duration. METHODS: Circadian preferences and sleep were investigated in 555 (Females N=247) Finnish students aged 15-20. The self-report measures included a shortened version of the Horne-Östberg Morningness-Eveningness Scale, the Epworth Sleepiness Scale as well as items probing feelings of tiredness, optimal subjective sleep durations, and bedtime and wake-up time on the most recent day and a typical weekend. Data were collected from Tuesday to Thursday during an ordinary school week. RESULTS AND CONCLUSION: The most frequent chronotype was the intermediate type (54%), and compared to previous studies, the prevalence of evening-oriented individuals was high (37%), whereas only 9% of the participants were classified as morning oriented. No gender-specific or chronotype-specific differences in sleep durations were observed, but girls/women and evening-orientated individuals reported suffering more from sleepiness, compared to boys/men and more morning-typed participants, respectively. About 20% of the total sample indicated that their subjective need for sleep was not satisfied during the weekdays nor the weekend, indicating chronic sleep deprivation. Among girls/women and evening-oriented individuals, the subjective sleep need was greater for weekday nights.

Determination of lycopene in food by on-line SFE coupled to HPLC using a single monolithic column for trapping and separation.

A method that would eliminate the degradation of lycopene during analysis was developed. Supercritical fluid extraction (SFE) with carbon dioxide as the extraction medium was connected on-line to high performance liquid chromatography (HPLC) where a single monolithic column was used for trapping and the subsequent separation of analytes. The method was linear over the studied range (0.1-2.5 microg), and it was repeatable (R.S.D. 3.9%), sensitive (LOD = 0.5 ng) and fast (35 min). Lycopene was determined in tomatoes, fruit and several food products. Because of the on-line construction, lycopene was not in contact with air or light during the whole procedure and the amount analysed should therefore correspond to the real amount in the sample.