ABSTRACT
This publication describes a method for the quantification by high-performance liquid chromatography (HPLC) of resinous compounds known as α-acids found in freshly harvested, unprocessed hops. This method provides consistent, efficient, and accurate results as well as the theories and rationale involved in HPLC method development. A system of quality checks was utilized as well as the validation of numerous developmental variables. By starting with a theoretical approach in preparation, extraction, and instrumental techniques and then further developing these practices by experimentation, a reproducible method was developed. Following the validation, fresh cascade hops grown in Sonoma County were analyzed during the 2017 harvest season and found to be within the predicted range specific to this cultivar. This method encompasses the techniques necessary to analyze fresh or dried hops, considering variability between different laboratories.
ABSTRACT
The anionic fluorescent dye, aminopyrene trisulfonic acid (APTS), was synthesized and used in a solution-based two-component glucose-sensing system comprising the dye and a boronic acid-appended viologen. The fluorescence of the dye was quenched in the presence of the viologen and the fluorescence restored upon glucose addition. An important feature of this fluorophore is that it can be covalently bonded to a polymer through the amine group without a significant effect on optical properties. Two APTS derivatives, functionalized with polymerizable groups, were synthesized and immobilized in hydroxyethyl methacrylate (HEMA)-based hydrogels. The latter were used to continuously monitor glucose. The fluorescence signal modulation, signal stability, reversibility, reproducibility, and pH sensitivity of the hydrogels were evaluated. The APTS dyes described herein are insensitive to pH changes within the physiological range, both in solution and when immobilized in a hydrogel. When APTS is used in conjunction with boronic acid-appended viologens to sense glucose, the system displays some pH sensitivity because of the presence of the boronic acid.
