Some commonly used SPR detection methods

One is to measure the reflection as a function of the incident angle with a photo detector by rotating both the prism and the photo detector. This method has a very limited angular resolution and time response because of the required mechanical movement in the setup. The mechanical movement can be avoided by fixing the photo detector at an angle near resonance and measuring the intensity change of the reflected beam due to a shift in the resonance angle. A drawback, however, is that the relationship between the intensity and the resonance angle is dependent on the angle at which the photo detector is fixed. The angular resolution is often limited by light fluctuations, thermal noise and mechanical drift. An alternative method to detect the resonance angle is to use a linear diode array (LDA) or charge coupled device (CCD). This method involves no mechanical movements, but the simultaneous detection of many channels (e.g., 1024 in a typical LDA) slows down the response time. The angular resolution is determined by the number of pixels, detector noises, light intensity fluctuations, and thermal and mechanical noises. Improved resolution can be achieved, but it requires numerically fitting the experimental data. A simpler and more accurate method to detect the resonance that has been successfully demonstrated for a variety of applications is to utilize a bi-cell photo detector, instead of the CCD or LDA. This approach is superior in terms of reduced noise, compactness, as well as time response to the CCD and LDA methods.


Unique optoelectronics for ultrahigh sensitivity and fast time response

BI-SPR uses innovative methods to detect the resonance angle, which is one of the keys for the high performance of the SPR instrument. One of the methods is noise cancellation, which removes common noises from sources such as light intensity fluctuations, thermal drift and mechanical instabilities. Another method is the use of a reference channel that shares nearly identical optics with the sample channel and symmetric arrangements of the sample and reference channels. Optimized and compact optical designs further improve the stability and performance of the instrument.


Creative Design for Maximum Versatility and Flexibility

SPR technology has already found diverse applications, and new applications are emerging rapidly. To meet the need of diverse applications and to assist innovative users to develop new applications, BI-SPR uses a patented creative design which offers flexibility and versatility for various applications by selecting the appropriate modules. For example, the flow module can be easily exchanged with an electrochemical cell assembly. The two flow channels can be used in conjunction with two valves for simultaneous measurements of two samples. Alternatively, one channel can be for the sample while the other used for background subtraction. Our instrument is also compatible and can be integrated with auto samplers and potentiostats from other vendors with little or minimal effort. Current application modules include:

• Basic SPR detection module
• Flow cell module
• Syringe pump module
• Gas phase detection module
• Electrochemistry module