For some time now our lab has used the Hitachi U-2000 Spectrophotometer for the routine quantification of samples as well as for observing the progress of enzymatic reactions over time. This spectrophotometer has a number of features that make it ideally suited for quantitative spectral analysis in both the ultraviolet and visible regions of the spectrum.
The wavelength range of the U-2000 is between 220 and 850 nm with a photometric range of 0 to 2 Abs. The temperature of the flow cell can be set to 25o, 30o, or 37o C, which is important when monitoring enzymatic reactions. There is also an “auto-sipper”, which uses a peristaltic pump to remove small amounts of sample for analysis. The amount of sample that is sipped depends on the rotating time of the pump which can be pre-set by the user (the sipping time can be pre-set for between 0 and 20 seconds). In addition, the sipping function can be controlled either manually, which sips one sample at a time, or automatically, which can sip up to 100 samples at once. The sampling function can also be pre-set for a delay, preventing the measurement of unstable liquid right after sample aspiration. The amount of time it takes to return the reaction sample back to the flow cell can also be pre-set by the user.
All of the functions mentioned are controlled by the operating keyboard and screen that are part of the machine itself. It is easy to change conditions, such as pre-set times or temperature, of the apparatus. The values are also displayed on the screen. One major advantage is that up to 20 standards can be stored and graphically displayed. A photometric value at a particular point on a curve can be measured by simply moving the cursor to that position. Hard copies of plots can be obtained using the built-in printer. Stats, such as the mean value, standard deviation and the coefficient of variation can all be automatically calculated.
It is important to note that this spectrophotometer does require proper maintenance. In particular the flow cell should be washed after each use to prevent contamination or deteriorated pump tubing. The flow cell can be flushed with water for about 5 minutes or so after each use. Periodically we wash the unit with water and a neutral detergent.
Overall, this spectrophotometer gets a lot of use in our lab because it works well. It has been a reliable piece of equipment that we depend on for our data.
Hee Chul Lee
Graduate Student
Dept. of Biochemistry
NYU School of Medicine