Fluorimeters operation

For the reasons pointed out in (Banishev et al., 2008a), the same laser fluorimeter has been optimized for measuring the nanosecond fluorescence decay (the kinetic mode of the fluorimeter operation). The curve represents the dependence of the number NnfW of fluorescence photons in the detector gate (with wide tg) on the gate delay time tad with respect to a laser pulse. For the model (la) an expression for kinetic curve can be written as ... 

The simpler fluorimeters are manual instruments operating only at a single selected wavelength at any one time. Despite this they are perfectly suitable for quantitative measurements, as these are almost always carried out at a fixed wavelength. The experiments listed at the end of this chapter have all been carried out at single fixed wavelengths. 

There are another type of photocells known as barrier layer photocells which work on an entirely different principle. They are semiconductor devices in which impinging photons promote the electrons from the valence band to the conduction band across the energy gap. A photovoltagc is generated which can be measured by a voltmeter. Such photovoltaic devices can have a large surface area and are easy to operate. They are commonly used in many simple colorimeters and fluorimeters and as light Otters for cameras. 

The development of photodetectors enabled the human eye to be replaced by a much more sensitive detector of light intensity. The evolution of modem colorimeters and of spectrophotometers capable of operation in both the ultraviolet and visible regions of the spectrum has been discussed.217,218 The phenomenon of fluorescence was first employed for quantitative analysis in the 1930s, when the first filter fluorimeters were constructed. An article has outlined the development of fluorescence analysis up to 1980.219 Lasers have now been employed long enough in analytical chemistry for a historical account to be given.220... 

Luminescence affords a very sensitive means of detection in flowing systems such as HPLC, electrophoresis, flow injection, and flow cytometry. HPLC fluorescence detectors are similar in operation to conventional fluorimeters. Most fluorescence detectors use filters for crude monochromation. Filters pass light in a wider band than do monochromators. This favors spectral sensitivity because more light excites the sample and is collected by the detector. Grating monochromators, on the other hand, favor selectivity. The fluorimetric detector is susceptible to the usual interferences that hinder fluorescence measurements, namely, background fluorescence and quenching. 

To operate the Opus analyzer, the operator selects a test and provides other information through an interactive touch screen/LCD display. When prompted, the operator inserts one assay-specific test module per test into the loading port of the instrument. The loader transports the test module to a 20 position incubated rotor where the test module is equilibrated to 37 C. The analyzer prompts for sample cup and pipette tip trays. Once these trays are supplied, the analyzer automatically picks up a new pipette tip, aspirates the sample and dispenses the sample onto the test module. For certain assays the pipettor also transports conjugate, substrate or other reagents from the test module wells to the test module dispense port. After processing, the test module is rotated to the read position where the fluorimeter takes measurements. The rotor then moves the used test module to the loader/ ejector where it is... 

Fluorescence induction curves were obtained from DCMU infiltrated leaves (3) using a laboratory-made fluorimeter. The actinic light from an array of 30 light emitting diodes (HLMP 3850) operated at In order to provide an homogeneous illumination actinic light was processed by two lenses as... 

A block diagram of a basic fluorimeter is shown in Figure 2. Aside from the optical components shown, modern fluorimeters have dedicated computers, which may control instrumental operating parameters, the acquisition of spectral data and the postprocessing of the data. 

ISA s (Spex s) Fluorolog Tau-3 lifetime system and Spectronic Instruments SLM-AMINCO 48000 DSCF spectrofluorimeter both use xenon flash lamp excitation (t5 ically 150-450 W) and have modulation frequencies of up to 310 MHz. (Most systems can also be operated as steady-state fluorimeters). SLM also manufactures a multi-harmonic s3rstem based on a pulse- modulated continuous wave light source. 

The model LS-2B is a low-cost, easy to operate, filter fluorimeter that scans emission spectra over the wavelength range 390-700 nm (scanning) or 220-650 nm (individual... 

Polarization effects in monochromators and other optical components can present significant difficulties in the overall operation and calibration of fluorimeter systems. At the same time, the introduction of polarizing elements such as polarizing filters or Glan-Thompson or Glan-Taylor polarizing optics are essential to the measurement of fluorescence polarization or anisotropy. 

Photomultiplier tube detectors are still the detector of choice for fluorimeter application owing to their excellent sensitivity and operational gain. Figure 5.15 shows typical spectral responsivity of a selection of photomultiplier detectors. 

In many laboratories, the performance validation of a fluorimeter instrument is still in its infancy, and the influence of the many parameters involved in the instrument operation is often not considered principally because it is thought that the instrument manufacturers have taken care of this problem in their software. In reality instrument performance validation must also be the responsibihty of the users to ensure the instrument meets their needs and has not drifted with time. With this in mind, users might undertake a series of standard measurements using one or more of the following ... 

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