A dual-wavelength single particle aerosol fluorescence monitor

Abstract

Original article can be found at: http://spie.org/x306.xml Copyright SPIE DOI: 10.1117/12.629868 [Full text of this article is not available in the UHRA]Laser diodes and light-emitting diodes capable of continuous sub-300 nm radiation emission will ultimately represent optimal excitation sources for compact and fieldable bio-aerosol monitors. However, until such devices are routinely available and whilst solid-state UV lasers remain relatively expensive, other low-cost sources of UV can offer advantages. This paper describes one such prototype that employs compact xenon discharge UV sources to excite intrinsic fluorescence from individual particles within an ambient aerosol sample. The prototype monitor samples ambient air via a laminar sheathed-flow arrangement such that particles within the sample flow column are rendered in single file as they intersect the beam from a continuous-wave 660nm diode laser. Each individual particle produces a scattered light signal from which an estimate of particle size (down to ~1 um) may be derived. This same signal also initiates the sequential firing (~10 us apart) of two xenon sources which irradiate the particle with UV pulses centred upon ~280 nm and ~370 nm wavelength, optimal for excitation of bio-fluorophores tryptophan and NADH respectively. For each excitation wavelength, fluorescence is detected across two bands embracing the peak emissions of the same bio-fluorophores. Thus, for each particle, a 2-dimensional fluorescence excitation-emission matrix is recorded together with an estimate of particle size. Current measurement rates are up to ~125 particles/s (limited by the xenon recharge time), corresponding to all particles for concentrations up to ~2 x 10^4 particles/l. Developments to increase this to ~500 particles/s are in hand. Analysis of results from aerosols of E.coli, BG spores, and a variety of non-biological materials are given

Occupational Microbial Risk among Embalmers

“…To detect the biological particles, the WIBS-NEO excites the particles with two UV laser diodes (280 nm and 370 nm) and then measures the resulting ultraviolet and visible fluorescence between 310 and 400 nm and 420 and 650 nm [30]. This combination of excitation and detection wavelengths enables the measurement of fluorescence from common living molecules, including nicotinamide adenine di-nucleotide (NADH), tyrosine, phenylalanine, tryptophan, and flavin compounds (riboflavin, flavoproteins) [30][31][32][33]. In this way, the WIBS-NEO makes it possible to distinguish the biological (fluorescent) from the non-biological (non-fluorescent) fractions.…”

Continuous bioaerosol monitoring in a tropical environment using a UV fluorescence particle spectrometer

“…The spectrometer is the latest version of a series of real-time biological particle monitors developed by the authors (Kaye et al, 2005a(Kaye et al, , 2005b. It continuously samples ambient air at a rate of ∼2.35 l min −1 through a delivery system that filters ∼2.1 l min −1 of the air and re-introduces this as a sheath around the remaining ∼250 ml min −1 sample flow.…”