Viable particle counting system and viable particle counting method
Inventors
Assignees
Publication Number
US-11215551-B2
Publication Date
2022-01-04
Expiration Date
2034-01-20
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Abstract
A particle counting system includes a particle counting means and pre-stage irradiation means. The particle counting means counts particles existing in a fluid by irradiating the fluid containing target particles with light at a predetermined wavelength, separating selectively autofluorescence or phosphorescence emitted from the target particles by the radiated light, receiving the separated autofluorescence or phosphorescence, and determining that the target particles are the particles according to the received autofluorescence or phosphorescence. The pre-stage irradiation means irradiates the fluid with ultraviolet light in advance before the particle counting means irradiates the fluid with the light at the predetermined wavelength. The particle counting means includes a band-pass filter that allows light having a wavelength of 450 nm to 600 nm to pass therethrough.
Core Innovation
The invention relates to a viable particle counting system and method that detect viable particles in air or liquid by utilizing autofluorescence or phosphorescence emitted from the viable particles. The system comprises a particle counter that irradiates a fluid containing target particles with light at a predetermined wavelength to induce autofluorescence or phosphorescence, selectively separates and receives this emitted light, and determines the presence of viable particles based on the detected signals.
The main problem addressed arises from difficulties in detecting viable particles, especially those emitting feeble autofluorescence such as heterotrophic bacteria, due to interference by Raman-scattered light from water and generally low fluorescence intensity. Conventional methods struggle to accurately count such particles using autofluorescence detection alone, resulting in poor signal-to-noise ratios and inaccurate viable particle counts.
To solve this, the invention introduces a pre-stage irradiation means that irradiates the fluid with ultraviolet light before it undergoes excitation light irradiation by the particle counting means. This pre-irradiation with ultraviolet light increases the intensity of autofluorescence or phosphorescence emitted from the viable particles, thereby improving the signal-to-noise ratio and enabling high-accuracy counting, including of viable particles that emit weak autofluorescence.
The system further provides configurations such as using a band-pass filter allowing light of 450 nm to 600 nm to pass, flow passage means that may be spiral-shaped to compact the system, and both batch-type and continuous-type pre-stage irradiation units to irradiate stored or flowing fluids with ultraviolet light for predetermined periods. The particle counter utilizes laser diode excitation light typically at 405 nm targeting autofluorescent substances like riboflavin or NAD(P)H in viable particles to selectively detect autofluorescence separate from scattered light.
Claims Coverage
The patent contains 6 independent claims covering system and method aspects, detailing features of a particle counting system, method for particle counting, and related irradiating steps.
Particle counting system with pre-stage ultraviolet irradiation
A system comprising a particle counter that irradiates fluid containing target particles with light at a predetermined wavelength, separates autofluorescence by an autofluorescence selection optical device comprising a band-pass filter allowing 450 nm to 600 nm light, receives autofluorescence, and processes the signal to detect and count target particles. The system further comprises a pre-stage irradiation device that irradiates the fluid with ultraviolet light for a predetermined period to increase autofluorescence intensity before irradiation by the particle counter.
Ultraviolet light wavelength range for pre-stage irradiation
The ultraviolet light emitted from the pre-stage irradiation device has a wavelength range of 200 to 280 nm.
Batch-type configuration with storage reservoir
The system includes a reservoir configured to store the fluid, where the pre-stage irradiation device irradiates the fluid in the reservoir with ultraviolet light for a predetermined period.
Continuous-type configuration with flow passage unit
The system includes a flow passage unit in which the fluid flows, and the pre-stage irradiation device irradiates the fluid flowing in this flow passage unit with ultraviolet light for a predetermined period.
Flow passage unit configured as spiral hollow pipe
The flow passage unit is a hollow pipe formed in a spiral shape configured to allow fluid flow while being irradiated with ultraviolet light by the pre-stage irradiation device.
Particle counting system separating scattered light for size determination
The system further includes a scattered light selection optical device and scattered light-receiving device configured to receive scattered light separated from irradiated light. The data processing unit compares both autofluorescence and scattered light signals to thresholds to determine presence and size of target particles.
The claims cover a particle counting system and method that irradiates fluid with ultraviolet light before excitation by laser light at a predetermined wavelength to increase autofluorescence intensity, uses selective band-pass filtering of autofluorescence between 450-600 nm, optionally includes batch or continuous irradiation configurations, and determines particle presence and size by comparing autofluorescence and scattered light signals against thresholds.
Stated Advantages
The system enables extremely accurate counting of viable particles, even those emitting feeble autofluorescence, by increasing the emission intensity of autofluorescence or phosphorescence through pre-stage ultraviolet irradiation.
Improvement of the signal-to-noise ratio through ultraviolet pre-irradiation allows high-accuracy viable particle counting not achievable by conventional methods.
The configuration can perform real-time detection and size measurement of viable particles in fluids like liquid or air.
The use of a spiral-shaped hollow pipe for the flow passage allows the system to be compact and suitable for continuous irradiation and counting.
Documented Applications
Counting viable particles such as bacteria, yeasts, and molds contained in water fluids including tap water.
Continuous counting of viable particles in liquids flowing through water pipes or water treatment plants.
Counting viable particles in atmosphere such as air in clean rooms, using continuous-type pre-stage irradiation.
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