The NanoDrop® ND-3300 Fluorospectrometer is a multi-source optical instrument for measuring fluorescence. This space-saving fluorometer offers exclusive features that allow investigators the flexibility to use fluorometry in valuable new ways.

The uniquely clean optics of the patented retention system, combined with virtual filtering (see below) for the white LED applications, enables measurements across a wide range of wavelengths using sample volumes of 1-2 ul without cuvettes and costly filter changes.

The excitation source comes from one of the three solid-state LEDs housed in a block adjacent to the measurement pedestal (see below for more details about the LEDs). Emitted light is collected using the traditional 90° angle from the respective excitation source. A 2048-element CCD array detector, covering 400-750nm, is connected by an optical fiber to the optical measurement surface. The spectrometer is configured with a cut filter to eliminate light transmission below 395 nm.

An added convenience is that no external power supply is required. All of the operating power is supplied by the USB port on the PC.

Virtual Filtering
The white LED is composed of a blue LED and a yellow-orange phosphor excited by the blue LED to give an approximately white spectrum (typically bluish in appearance). Virtual filtering (patents pending) involves taking a reference spectrum as a wavelength intensity map of the white LED yellow peak. The reference spectrum is then normalized to a non-fluorescence wavelength of the sample's signal spectrum. This normalized reference spectrum, when subtracted from the signal spectrum, will remove nearly all the stray excitation contribution to the fluorescence signal spectrum. The normalization or scaling is typically done at a wavelength within the stability envelope (the region of the white spectrum) on the short wavelength side of the sample's fluorescence peak where the fluorescence signal is less than 5% of its peak value.