Fiber-Optic Quantum Counter Probe for Incident Excitation Energy Correction in Fluorescence Measurements

Abstract

Excitation-power correction of uorescence spectra is essential for meaningful interpretation of analytical data. In particular, uorescence m easurements obtained using optical bers require special consideration due to the possibility of variations in the light intensity delivered to the sample or the incident excitation energy. A quantum counting ber-optic probe has been developed to sim ultaneously and independently collect uorescence spectra of both analytes and a quantum counter. The probe consists of excitation and emission bers angled to maximize distal cone overlap and a third ber positioned at a greater angle to allow excitation of rhodamine B, which is af xed to its distal end with a polymer. The uorescence of the quantum counter af xed to the ber was linear with incident 266 nm excitation energy over the measured range 1.2 3 10 14 photons per exposure to 1.2 3 10 15 photons per exposure at 266 nm. The corrected uorescence signals were im mune to adverse condition experiments such as laser power reduction and launch berlaser beam misalignment, while the uncorrected signals suffered greatly. The concentration calibration generated using the beroptic quantum counter method showed an improvement in the correlation coef cient, r 2 5 0.950, compared with the calibration generated using uncorrected data, r 2 5 0.906. Different types of adverse conditions were tested including power attenuation, power increase, and ber launch misalignment; the prediction erro rs were between 287% and 366% for the uncorrected data compared with prediction errors between 29% and 15% when using the ber-optic quantum counter method.

Fluorescence standards: Classification, terminology, and recommendations on their selection, use, and production (IUPAC Technical Report)

“…As the use of neither quantum counters [1,48,51,[106][107][108] nor actinometers [109][110][111] is advisable [112] (see also ref. [76]), scope-relevant requirements on these materials were omitted.…”

Recommendations for Fluorescence Instrument Qualification: The New ASTM Standard Guide

“…A CD with certified values is the most reliable choice over the broadest wavelength range. Care has to be taken with the use of a quantum counter, ,− because of its limited wavelength range, dye concentration dependence, and polarization dependence in viscous solvents. Similar to a CD, the spectral range and accuracy of a quantum counter, when used for spectral correction, should be known and not assumed.…”