Fluorescent dye experiment illustrates ultra-micro cell benefits

To illustrate the benefits of the Starna Scientific’s new Type 19FL ultra-micro cell the company has devised an experiment that uses the 5uL cell to measure a solution of fluorescent dye from a yellow highlighter pen.

A dilute solution of the pen’s fluorescent dye was prepared and pipetted into a standard 1cm square fluorescence cell. Prescan was used to determine the optimal wavelengths for excitation and emission. The wavelengths were then selected for the study.

The Varian Cary Eclipse spectrofluorimeter was used to carry out the experiment because it is a versatile platform in a rugged design that provides very sensitive, fast performance. The typical Raman sensitivity (signal/noise) for water at 350 nm (ex) is approx 3500-4500.

The optical configuration of the cell is suitably matched to the beam profile of the Cary Eclipse instrument thereby optimising the available energy entering the sample being measured. The use of a collimation lens on the emission window, and mirror coating on opposed faces amplifies emission output to improve sensitivity.

For the experiment all measurements were made using the Varian Eclipse Fluorimeter that was equipped with a standard cell holder and a Starna 19.05F/L/Q/5/Z20 5ul microcell.

Conditions were adjusted to provide a reasonable scale readout. Comparative quantitation was established by keeping the instrument conditions constant.

To align the ultra-micro cell a moderately bright fluorophore was installed in the standard cell holder and the software’s Align module was used to seek an optimum signal by slowly adjusting the height and pitch of the cell.

The correlation between the experiment’s results shows that at the dilution levels used and with this specific cell alignment there is no qualitative difference between the result quality (all data collected at the same scan speed).

The scans show excellent correlation even though the absolute reading for the ultra-micro cell was less than 3 AFU. The cell was removed and re-aligned between these sets of readings and it was possible to achieve about five percent full volume sensitivity with more dilute samples.