SEVERAL FACTORS AFFECTING THE DETECTION SENSITIVITY OF THE REACTION HEAT-INDUCED OPTICAL BEAM DEFLECTION METHOD

In order to improve the detection sensitivity of the reaction heat-ind uced optical beam deflection method, the experimental factors that aff ect the detection sensitivity were investigated in detail. Firstly, di fferent types of deflection detectors were compared. The experimental results showed that the bi-cell photodiode detector is most sensitive to the deflection signal. Secondly, the effect of the size of the reac tion cell on the detection sensitivity was investigated. A small react ion cell gave a stable baseline and small noise in flow injection expe riments, and thus gave a high detection sensitivity. Thirdly, the effe cts of the optical arrangements on the detection sensitivity were inve stigated. Focusing the probe beam close to the gold film/CCl4 interfac e enhanced the detection sensitivity. Also, refocusing the deflected p robe beam improved the sensitivity. Under the selected experimental co nditions, the detection of the neutralization reaction between HCl and NaOH at sub-nanomol level became possible. Further improvements are a lso discussed.