Method for measurement of impurities in liquids

• US 4,794,086 A
• Filed: 11/25/1985
• Issued: 12/27/1988
• Est. Priority Date: 11/25/1985
• Status: Expired due to Term

• Current Assignee: Liquid Air Corporation One Embarcadero Center San Francisco CA 94111
• Original Assignee: Liquid-Air Inc
• Inventors: Wen, Horng Y., Kasper, Gerhard
• Primary Examiner(s): Richman, Barry S.
• Assistant Examiner(s): Hill, Jr., Robert J.
• Application Number:
  US06/801,305
• Time in Patent Office: 1,128 Days
• Field of Search: 356/36, 356/37, 356/72, 356/73, 356/335-343, 73/29, 73/28.61 R, 436/181, 436/36, 436/164
• US Class Current: 436/36
• CPC Class Codes: G01N 15/0205 by optical means
• CPC Class Codes: G01N 15/06 Investigating concentration of particle suspensions by weighing G01N5/00; investigating sedimentation of particle suspensions G01N15/04; investigating individual particles G01N15/10
• CPC Class Codes: G01N 15/065 using condensation nuclei counters
• CPC Class Codes: G01N 2021/8564 Sample as drops
• CPC Class Codes: G01N 33/18 Water
• CPC Class Codes: Y10T 436/25875 Gaseous sample or with change of physical state

Abstract

Method and apparatus for the measurement of sub-ppm concentrations of impurities in liquids. The liquid to be measured for impurities is dispersed into uniform droplets of a precisely known diameter D in a gas stream, such as air, using for example, a vibratory orifice generator. The dispersed droplets evaporate in the gas stream to leave a residue particle having a diameter d, which can be measured for example by means of a laser light scattering spectrometer. The concentration by volume, C_v, of the impurities can then be calculated according to the equation; C_v =(d/D)³.

Claims

1. A method for the rapid measurement of the concentration by volume of sub-ppm levels of dissolved impurities in a liquid comprising:

providing a liquid containing dissolved impurities;

dispersing said liquid in a gas stream to generate uniform droplets of precisely known diameter D;

evaporating said droplets while they are carried in said gas stream so that each droplet leaves a residue particle having a diameter d;

measuring the diameter d of the residue particles; and

calculating the concentration by volume, C_v, of the dissolved impurities in the liquid according to the equation;

space="preserve" listing-type="equation">C.sub.v =(d/D).sup.3.

2. The method as claimed in claim 1 wherein:

the diameter D of said droplets is in the range of about 20 um to about 50 um.

3. The method as claimed in claim 1 wherein:

any static charges on the droplets and residue particles are neutralized before measuring the diameter d of the residue particles and wherein said liquid is dispersed in said gas stream using a monodisperse droplet generator wherein a jet of said liquid fed by a syringe pump is broken up in a controlled manner into highly uniform droplets of precisely known diameter D by a piezoelectric vibrating orifice which vibrates at a selectable frequency and said droplets are introduced into a turbulent gas stream of said gas, which gas is substantially non-reactive with the liquid or dissolved impurities to disperse and rapidly dry said droplets.

4. The method as claimed in claims 1 or 3 wherein:

the diameter D of said droplets is (one) in the range of about 1 um to about 200 um.

5. The method as claimed in claim 1 or 3 wherein the diameter d of said residue particles is measured with an aerodynamic particle sizer.

6. The method as claimed in claim 3 wherein:

said gas stream is filtered prior to its passage through said monodisperse droplet generator.

7. The method as claimed in claim 1 or 3 wherein:

the diameter d of said residue particles is measured using an electrostatic classifier and a particle detector.

8. The method as claimed in claim 7 wherein said particle detector is a condensation nuclei counter.

9. The method as claimed in claim 3 wherein:

any static charge on said droplets and said residue particles are neutralized electrically by a krypton-85 radioactive neutralizer to reduce the level of static charge on said droplets and said residue particles to near Boltzmann charge equilibrium.

10. The method as claimed in claim 9 further comprising:

periodically heating said gas stream carrying said residue particles to cause evaporation of dissolved organic impurities in said residue particles to enable a determination of whether organic or inorganic dissolved impurities are present in said liquid by comparing the diameter d of said particles before heating with the diameter d of said particles after heating.

11. The method as claimed in claim 3 or 9 wherein:

the diameter d of said residue particles is measured using a light scattering spectrometer.