Bitterness and pungency are important parameters for olive oil quality. Therefore, two instrumental methods for evaluation of these taste attributes were developed. The first one is based on the photometric measurement of total phenolic compounds content, whereas the second one is based on the semiquantitative evaluation of hydrophilic compounds by highperformance liquid chromatography−mass spectrometry (HPLC-MS). Evaluation of total phenolic compounds content was performed by a modified method for the determination of the K 225 value using a more specific detection based on the pH value dependency of absorbance coefficients of phenols at λ = 274 nm. The latter method was not suitable for correct prediction, because no significant correlation between bitterness/pungency and total phenolic compounds content could be found. For the second method, areas of 25 peaks detected in 54 olive oil samples by a HPLC-MS profiling method were correlated with the bitterness and pungency by partial least-squares regression. Six compounds (oleuropein aglycon, ligstroside aglycon, decarboxymethyl oleuropein aglycon, decarboxymethyl ligstroside aglycon, elenolic acid, and elenolic acid methyl ester) show high correlations to bitterness and pungency. The computed model using these six compounds was able to predict bitterness and pungency of olive oil in the error margin of the sensory evaluation (±0.5) for most of the samples.

Modified nucleosides derived from the RNA metabolism constitute an important chemical class, which are discussed as potential biomarkers in the detection of mammalian breast cancer. Not only the variability of modifications, but also the complexity of biological matrices such as urinary samples poses challenges in the analysis of modified nucleosides. In the present work, a comprehensive two-dimensional liquid chromatography mass spectrometry (2D-LC-MS) approach for the analysis of modified nucleosides in biological samples was established. For prepurification of urinary samples and cell culture supernatants, we performed a cis-diol specific affinity chromatography using boronate-derivatized polyacrylamide gel. In order to establish a 2D-LC method, we tested numerous column combinations and chromatographic conditions. In order to determine the target compounds, we coupled the 2D-LC setup to a triple quadrupole mass spectrometer performing full scans, neutral loss scans, and multiple reaction monitoring (MRM). The combination of a Zorbax Eclipse Plus C18 column with a Zorbax Bonus-RP column was found to deliver a high degree of orthogonality and adequate separation. By application of 2D-LC-MS approaches, we were able to detect 28 target compounds from RNA metabolism and crosslinked pathways in urinary samples and 26 target compounds in cell culture supernatants, respectively. This is the first demonstration of the applicability and benefit of 2D-LC-MS for the targeted metabolome analysis of modified nucleosides and compounds from crosslinked pathways in different biological matrices.

The use of the direct inlet probe-atmospheric-pressure chemical ionization (DIP-APCI) ion source developed in our laboratory coupled to a high resolution Q-TOF MS for the quantitative analysis of coumarin in different cinnamon samples was demonstrated in this study. Extraction of coumarin from various cinnamon samples was followed by DIP-APCI-mass spectrometry (MS) and liquid chromatography (LC)-MS analysis. For quantification, an external calibration with and without the use of stable isotope-labeled coumarin as internal standard was compared. The results obtained by DIP-APCI-MS and LC-MS were in good agreement. Even without the use of an internal standard satisfying linearity (R(2) > 0.997), recovery (94-104% for spiking levels between 100 and 5,000 mg/kg) and intra- and interday repeatability (2.2-13.8%RSD) was demonstrated using DIP-APCI-MS. To reduce the number of samples requiring quantitative analysis, the possibility of semi-quantitative screening of coumarin directly from powdered cinnamon using DIP-APCI-MS was shown. The analysis of woodruff-flavored beverages and cinnamon-flavored chewing gum by DIP-APCI-MS resulted in the formation of an artifact interfering with coumarin detection. As with other ambient ionization methods, special attention has to be paid to possible spectral interferences due to isobaric substances present in the sample matrix or formed from matrix components after ionization. The temperature-programmed vaporization in DIP-APCI-MS combined with the use of stable isotope-labeled coumarin as internal standard helped in recognizing this interference.

A trend is observed in mass spectrometry, in which solid samples without prior dissolution and chromatographic separation are brought directly into the ion source and are ionized, e.g., by corona discharge (Atmospheric Solids Analysis Probe) or plasma (Direct Analysis in Real Time). The Direct Inlet Probe-atmospheric-pressure chemical ionization (APCI) ion source presented here, which was coupled to a high-resolution quadrupole time-of-flight-mass spectrometer, differs from most of the other ion sources in having temperature-programmed heating of the sample. The resulting possibility to reduce ion suppression and ion-molecule reactions in the ion source was shown by the separation of two fatty acid methyl esters as a result of their boiling point difference. Using caffeine as sample, certain source parameters such as the auxiliary gas flow, the drying gas flow, and the position of the probe tip in the ion source were optimized. The ability to perform quantitative analyses was shown by the linear concentration response (R(2) = 0.9984) observed when analyzing different caffeine concentrations. An extract of a Chinese medicinal herb was used to examine the reproducibility (relative standard deviations of the most abundant m/z signals were ≤8.1 %). It was also possible to distinguish milled samples of Radix Angelicae sinensis and Radix Angelicae gigas from each other and to identify the coumarins they contain without sample preparation. Supplying synthetic air instead of nitrogen to the ion source makes APCI in the negative mode possible as well; this was proven by the analysis of n-nonyl-β-D-maltoside.