Abstract: Online detection of substances with an alcoholic or phenolic hydroxyl group using imidazole and peroxyoxalate chemiluminescence was investigated qualitatively using a flow injection method. The substances tested included six polyphenols, five monophenols and six sugars. After incubation at 80°C with an imidazole buffer (pH 9.5) the substances were detected by peroxyoxalate chemiluminescence. The polyphenols tested (e.g., pyrogallol, purpurogallin, and dopamine) showed the strongest light emission. The sugars with hydroxyl groups (e.g., fructose and lactose) and the monophenols (e.g., phenol, serotonin, and β-estradiol) produced only a weak light emission. Imidazole served two roles, it catalyzed the reaction with the hydroxyl compound and initiated peroxyoxalate chemiluminescence online. A novel reactor formed by packing glass beads into a flow cell (Teflon) of a chemiluminometer improved the sensitivity of light detection.

Abstract: HPSSW type, (horizontally polarized surface shear wave) surface acoustic wave (SAW) devices have been proven to be suitable for biosensing applications. They allow an easy and fast label free detection of molecules with biological relevance via direct detection of the adsorbed mass. However, SAW device structures are usually connected by bond wires. In consequence sampling chambers suffer from relatively big flow cell volumes /spl sim/ 50 /spl mu/l. We developed new resonator filter based HPSSW devices with gold transducers. They work at an operating frequency of 433.9 MHz on 36/spl deg/YX LiTaO/sub 3/ as substrate material. Bonding wires could be eliminated as the sensor is capacitively coupled with the driving electronics via large contact pads. The new coupling concept (originally developed for our gas sensing approach) enables the reduction of the sample volume in the flow cell down to 60 nl. This decreases sample consumption and reduces the length of the measurement cycles. Affinity assays were realized using this SAW biosensor. Measurements with the systems urease/anti-urease and estradiol/estrogen receptor are shown exemplarily. In the latter case it could be shown that reference SAW surfaces without binding partner have the potential to enable the quantification of binding reactions even in complex media. For automated sample handling, the SAW detection unit is integrated in a flow injection analysis (FIA) system. A cost-effective, compact demonstration instrument for SAW biosensing was developed.