Optimization of an online post-column derivatization system for ultra high-performance liquid chromatography (UHPLC) and its applications to analysis of biogenic amines.

We investigated the efficacy and utility of a post-column derivatization method for the detection of amines with o-phthalaldehyde (OPA) in ultra high-performance liquid chromatography (UHPLC). Since it was anticipated that a derivatization reaction system placed downstream of the column would give considerable band broadening to narrow peaks generated by a UHPLC column, we examined the contributions of the dimensions of the reaction tube, the fluorescence (FL) detector flow cell, and the column to the extra-column peak broadening, and optimized the post-column derivatization system in UHPLC. We successfully separated amines within 6 min with gradient elution by using the post-column derivatization system connected to a UHPLC system. The analysis time was reduced by a factor of 7 compared with that by conventional HPLC. The detection limits were 18.0 - 105.7 fmol, depending on the compounds; the reproducibilities were 0.11 - 0.82% RSD for the retention times and 0.78 - 1.66% RSD for the peak areas (n = 10), respectively. The linear dynamic ranges were up to 12, 20, and 40 pmol/µL, depending on the compounds, respectively.

In vivo long-term durability of the bond to dentin using two adhesive systems.

PURPOSE: The objective of this work was to evaluate the in vivo long-term durability of bond strength and morphological appearance of interfaces between dentin and two adhesive systems. MATERIALS AND METHODS: Class V cavities were prepared on the facial surfaces of 6 intact teeth of a monkey, and restored with Unifil Bond/Unifil F and Fuji Bond LC/Clearfil AP-X. One year later, 10 other teeth were restored with the same materials and the monkey was sacrificed after 24 hours. For in vitro examination, 6 more teeth were extracted from the monkey, restored in a similar manner with the two materials, and stored in 37 degrees C water for 1 day. All specimens were subjected to the microtensile bond strength (microTBS) test. The debonded surfaces of specimens were morphologically observed with the FE-SEM. RESULTS: There were no statistically significant differences among the mean microTBS obtained for Unifil Bond/Unifil F under the three conditions (1 day and 1 year in vivo, and 1 day in vitro), and most specimens showed cohesive failure within resin composite (Unifil F). However, FE-SEM observations showed that resinous material within the hybrid layer made by Unifil Bond seemed to increase in porosity after 1 year. For Fuji Bond LC/Clearfil AP-X, pTBS at 1 day in vitro was significantly higher than that at 1 year in vivo, and bond strengths in vivo tended to decrease over time, although a statistically significant difference was not observed. From FE-SEM observations, most specimens showed cohesive failure within the adhesive (Fuji Bond LC). CONCLUSION: Bond strengths of the two adhesive systems tended to decrease for 1 year in vivo.