US 7,804,064 B2 · In-situ droplet monitoring for self-tuning spectrometers

Abstract

A laser scattering based imaging technique is utilized in order to visualize the aerosol droplets in an inductively coupled plasma (ICP) torch from an aerosol source to the site of analytical measurements. The resulting snapshots provide key information about the spatial distribution of the aerosol introduced by direct and indirect injection devices: 1) a direct injection high efficiency nebulizer (DIHEN); 2) a large-bore DIHEN (LB-DIHEN); and 3) a PFA microflow nebulizer with a PFA Scott-type spray chamber. Moreover, particle image velocimetry (PIV) is used to study the in-situ behavior of the aerosol before interaction with, for example, plasma, while the individual surviving droplets are explored by particle tracking velocimetry (PTV). Further, the velocity distribution of the surviving droplets demonstrates the importance of the initial droplet velocities in complete desolvation of the aerosol for optimum analytical performance in ICP spectrometries. These new observations are important in the design of the next-generation direct injection devices for lower sample consumption, higher sensitivity, lower noise levels, suppressed matrix effects, and for developing smart spectrometers. For example, a controller can be provided to control the output of the aerosol source by controlling the configuration of the source or the gas flow rate via feedback information concerning the aerosol.

Drawings

Drawings are temporarily unavailable. Open the PDF at USPTO

Drawings

Claims43

Dependent claims

A self-tuning spectrometer comprising a system for in-situ droplet monitoring, the system comprising:

a laser light delivery system for delivering at least two laser pulses to at least one of droplets, particles and aerosol;
a detector for capturing a scattering of the laser pulses from the at least one of droplets, particles and aerosol;
an image acquisition unit for receiving and processing data from the detector;
and
a system controller for synchronizing the laser delivery system and the detector, whereby the scattering of the laser pulses from the at least one of droplets, particles and aerosol is processed to monitor properties of the at least one of droplets, particles and aerosol;
wherein operating parameters of at least one of (1) the self-tuning spectrometer, (2) a source of the at least one of droplets, particles and aerosol and (3) a plasma source or a high temperature source are optimized based on the monitored properties of the at least one of droplets, particles and aerosol.

3 more elements

Dependencies are inferred from the claim text.

Description7,189 words

Summary1,517 words

#1. Field of the Invention

#This application relates generally to nebulizers for use in analytical spectrometry such as inductively coupled mass spectrometry, as well as to fuel injector systems, inhalers, and the like. More specifically, the present invention is directed to methods for monitoring and controlling droplets and their characteristics in order to, for example, optimize spectrometer operating parameters to improve stability of an analytical signal and/or enhance the signal. (Throughout the specification the terms “droplets”, “aerosol” and “particles” may be used interchangeably.)

#2. Description of the Related Art

Brief description of the drawings7 figures

#Certain exemplary aspects and features of the present invention will be more apparent by describing certain embodiments of the present invention with reference to the accompanying drawings, in which:

#FIG. 1 is a schematic diagram illustrating an experimental setup for in-situ visualization and characterization of aerosol droplets in an inductively coupled plasma in accordance with an embodiment of the present invention;

#FIG. 2 is a side-on snapshot illustrating droplets introduced by direct injection high efficiency nebulizer (LB-DIHEN) inside an Ar ICP where position 1 represents 1-mm above the intermediate tube, position 2 represents a last turn of the load coil, and position 3 represents a typical location of a sampler in an ICPMS e.g., 10 mm above the load coil;

Detailed description5,330 words

#The concepts and devices presented here can be used to monitor droplets and their characteristics as they undergo desolvation and evaporation in a plasma or a flame source. This information (e.g. droplet number density, droplet size and velocity) can then be used as a feedback signal to optimize the droplet generation and/or source and spectrometer operating parameters to obtain a stable analytical signal. Although in an embodiment of the present invention, the in-situ measurements described below are centered on an inductively coupled plasma source, it should be appreciated by those skilled in the art that the in-situ measurements are equally applicable to other sources.

#To illustrate the potentials of the proposed technique in creating data suitable for tunable spectrometer, the droplet size and velocity information is presented for three diverse nebulization systems. The nebulization systems include: 1) a direct injection high efficiency nebulizer (Model DIHEN-170-AA, manufactured by Meinhard Glass Products, Analytical Reference Materials International Corp., Golden, Colo.) as described by A. Montaser, J. A. McLean, J. M. Kacsir, A Novel Direct Injection High Efficiency Nebulizer for Atomic Spectroscopy, U.S. Pat. No. 6,166,379 (2000) and J. A. McLean, H. Zhang, A. Montaser, A Direct High Efficiency Nebulizer for Inductively Coupled Plasma Mass Spectrometry, Anal. Chem. 70, 1012-1020 (1998); 2) a large bore-DIHEN (Model LB-DIHEN-30-AA, Large Bore Direct Injection High Efficiency Nebulizer for Inductively Coupled Plasma Spectrometry, Anal. Chem. 72, 1885-1893 (2000); and 3) a fixed-capillary microflow nebulizer (Model PFA-100, Elemental Scientific, Inc., Omaha, Nebr.) with a Scott-type spray chamber (Model PureChamber, Elemental Scientific, Inc.) both made from PFA, all of which are incorporated herein in their entirety.

#The exemplary monitoring system 100 of FIG. 1 comprises a dual cavity frequency-doubled Nd: YAG pulsed laser 102 and a set of cylindrical lenses 104 comprising mirrors 104a and a cylindrical lens 104b in order to generate a laser sheet of about 1-mm thickness which slices the plasma at a desired position.

Facts

Application

11/240,642Filed 3 Oct 2005 · us provisional application

Priority

1 Oct 2004

Published

US 2006/0087651 A127 Apr 2006

Granted

28 Sep 2010

Term ends

9 Dec 2028

Estimated · how

20 years from earliest known nonprovisional domestic filing plus recorded patent term adjustment, including 1,163 days of adjustment. Maintenance-fee lapses, terminal disclaimers and statutory extensions have not been checked. The continuity chain may be incomplete; this is not an enforceability determination.

Classification6 codes

G01N 15/065
Investigating concentration of particle suspensions: using condensation nuclei counters
G01N 15/1433
Signal processing: using image recognition
G01N 2015/1027
Investigating individual particles: determining speed or velocity of a particle
G01N 2015/1486
Optical investigation techniques, e.g. flow cytometry: counting the particles

Timeline

1 Oct 2004Priority claimedParent application 60/615,542
3 Oct 2005Application filedUS 11/240,642
9 Jan 2006Assigned to George Washington University, theassignment of assignor's interest
27 Apr 2006PublishedUS 2006/0087651 A1
28 Sep 2010GrantedUS 7,804,064 B2
1 Jul 2020Assigned to United States Department of Energyconfirmatory license
12 Oct 2026TodayWithin its term
9 Dec 2028Term endsEstimated, includes 1,163 days of adjustment

In-situ droplet monitoring for self-tuning spectrometers

Life of this patent

In-situ droplet monitoring for self-tuning spectrometers

Life of this patent

Life of this patent

Abstract

Drawings

Drawings

Claims43

Description7,189 words

Drawings

Classification6 codes

Life of this patent

Description7,189 words