简介：

The analysis of beer represents a significant analytical challenge in several respects. For one, beer is a very complex sample containing a wide range of components including vitamins, amino acids, proteins and bitter acids, all imparting peculiar organoleptic properties to the drink. The presence and quantity of certain compounds are monitored to ensure a consistent product. In typical settings for process and quality control of beer production, the analysis of low molecular weight components would benefit from high resolution chromatographic separation, driving the laboratory throughput up and costs down.

Bitter acids are of particular interest in beer analysis due to their considerable impact on the taste of the final product. Being a large group of closely related compounds, bitter acids differ in the type and location of a side chain substituent. Acquisition of accurate mass data in both full scan and MSn mode should enable detailed and confident structural characterization.

Identifying statistically significant differences among multiple LC-MS traces is enhanced considerably by having high mass accuracy and reproducible retention times. For example, one could envision such ‘fingerprinting’ as a routine part of the production monitoring process. For this type of application, an extremely robust LC-MS system is absolutely critical. The system must cope with the potentially deleterious effect of build up of material in the ion source region. We tested this aspect of routine operation by running repetitive beer analyses over a 24-hour period.

仪器：

Accela超高效液相色谱(U-HPLC)

LTQ Orbitrap电场轨道阱回旋共振组合质谱仪

结论：

The LTQ Orbitrap mass spectrometer coupled to the Accela U-HPLC system enables sample analysis at both normal and ultra-high pressure.

• U-HPLC and small particle columns afford fast analysis times while maintaining very high chromatographic resolution (peak width 4 seconds at half height). These columns also proved to be extremely robust, allowing for an uninterrupted analysis of 50 untreated beer samples (continued analysis over a 24-hour period).

• The mass deviation of the LTQ Orbitrap measurements was always better than 1 ppm using internal calibration, and remained stable for considerable time (over 24 hours).

• Accurate mass measurements greatly increase the confidence in elemental composition assignment. The structure of unknown colupulone was derived using Mass Frontier software relying on accurately measured parent and fragment ions.

• Accurate mass measurements also significantly improve the precision of quantitation by eliminating nearly isobaric interferences. A dramatic enhancement in the performance and accuracy of the quantitation software is observed as well.

• SIEVE differential expression software enables largescale statistical evaluation of multiple complex LC-MS analyses. Such fast and powerful ‘fingerprinting’ analysis can be applied in process and/or quality control monitoring.