Thermal degradation of cloudy apple juice phenolic constituents.

Although conventional thermal processing is still the most commonly used preservation technique in cloudy apple juice production, detailed knowledge on phenolic compound degradation during thermal treatment is still limited. To evaluate the extent of thermal degradation as a function of time and temperature, apple juice samples were isothermally treated during 7,200s over a temperature range of 80-145 °C. An untargeted metabolomics approach based on liquid chromatography-high resolution mass spectrometry was developed and applied with the aim to find out the most heat labile phenolic constituents in cloudy apple juice. By the use of a high resolution mass spectrometer, the high degree of in-source fragmentation, the quality of deconvolution and the employed custom-made database, it was possible to achieve a high degree of structural elucidation for the thermolabile phenolic constituents. Procyanidin subclass representatives were discovered as the most heat labile phenolic compounds of cloudy apple juice.

An improved mass spectrometric method for identification and quantification of phenolic compounds in apple fruits.

Thirty-nine phenolic compounds were analysed using ultra high performance liquid chromatography (UHPLC) coupled with diode array and accurate mass spectrometry detection using electrospray ionisation (DAD/ESI-am-MS). Instrumental parameters such as scan speed, resolution, and mass accuracy were optimised to establish accurate mass measurements. The method was fully validated in terms of model deviation (r(2)>0.9990), range (typically 10-3500 ngg(-1)), intra/inter-day precision (<6% and <8%, respectively) and accuracy (typically 100 ± 10%). The mass accuracy of each selected phenolic compound was below 1.5 ppm. The results confirmed that the UHPLC-DAD/ESI-am-MS method developed here was convenient and reliable for the determination of phenolic compounds in apple extracts.

Direct analysis of phthalate ester biomarkers in urine without preconcentration: method validation and monitoring.

Phthalates, which are ubiquitous in the environment, are readily metabolized in human bodies to their respective monoesters. These phthalate monoesters are non-persistent with short half-lives, which make them the ideal biomarkers of human exposure to phthalates. In this study a direct analysis method without preconcentration was developed and validated for the following phthalate ester metabolites in urine: mono-(2-ethylhexyl) phthalate, mono-(2-ethyl-5-hydroxyhexyl) phthalate, mono-(2-ethyl-5-oxohexyl)phthalate, monobenzyl phthalate, mono-isobutylphthalate, mono-n-butyl phthalate and monoethyl phthalate. The recovery of the phthalate ester metabolites varied between 97% and 104%. The intraday precision for the replicate analysis (n=10) of a urine sample did not exceed 5% for most of the compounds. The coefficient of variance amounted to 2-3%. The limit of quantification was set equal to 0.5µg/L for the majority of the compounds. A comparison between the direct analysis method and a foregoing solid phase extraction (SPE) of the urine sample was made. Finally, the applicability of the direct analysis method was tested in three interlaboratory comparisons.