In situ use of gelatin or an aminodextran in the preparation of uniform ferrite particles

• US 5,240,640 A
• Filed: 10/31/1991
• Issued: 08/31/1993
• Est. Priority Date: 06/04/1990
• Status: Expired due to Term

• Current Assignee: Coulter International Corp.
• Original Assignee: Coulter Corporation (Danaher Corporation)
• Inventors: Burshteyn, Alexander, Siiman, Olavi
• Primary Examiner(s): Lovering, Richard D.
• Application Number:
  US07/786,024
• Time in Patent Office: 670 Days
• Field of Search: 252/309, 252/313.1, 252/315.2, 252/62.51, 252/62.53, 252/62.54, 427/213.3, 428/402, 428/403
• US Class Current: 516/101
• CPC Class Codes: B01J 13/0008 Sols of inorganic materials in water
• CPC Class Codes: B01J 13/0013 from a precipitate
• CPC Class Codes: B03C 1/01 by addition of magnetic adjuvants
• CPC Class Codes: G01N 2446/20 the magnetic material being present in the particle core
• CPC Class Codes: G01N 2446/30 the magnetic material being dispersed in the polymer composition before their conversion into particulate form
• CPC Class Codes: G01N 2446/84 Polymer coating, e.g. gelatin
• CPC Class Codes: G01N 2446/86 the coating being pre-functionalised for attaching immunoreagents, e.g. aminodextran
• CPC Class Codes: G01N 33/5434 using magnetic particle immunoreagent carriers which constitute new materials per se
• CPC Class Codes: G11B 5/133 with cores composed of particles, e.g. with dust cores, with ferrite cores with cores composed of isolated magnetic particles in thin films G11B5/31
• CPC Class Codes: H01F 1/061 with a protective layer
• CPC Class Codes: H01F 1/112 with a skin H01F1/113 takes precedence
• CPC Class Codes: H01F 1/37 in a bonding agent
• CPC Class Codes: H01F 1/445 the magnetic component being a compound, e.g. Fe3O4 H01F1/447 takes precedence
• CPC Class Codes: Y10T 428/2982 Particulate matter [e.g., sphere, flake, etc.]
• CPC Class Codes: Y10T 428/2991 Coated

Abstract

A method is described for the preparation of uniform colloidal particles of ferrites, containing manganese(II), at a relatively low temperature in the presence of an aminodextran solution which acts as a support vehicle for the nucleation and growth of colloidal particles of metal oxide and for dispersion as separate single particles.

Claims

1. A method of making colloidal ferrite particles of uniform size and shape comprising:

A. mixing a first solution of potassium nitrate and potassium hydroxide or sodium nitrate and sodium hydroxide, respectively, which has been nitrogen gas purged and a

B. second solution of ferrous salt, divalent metal salt and an aminodextran solution which second solution has been nitrogen purged;

C. sweeping the aminodextran- metal hydroxide mixture of the two solutions with nitrogen gas and ripening same to form a ferrite hydrosol at a predetermined low temperature for a selected period of time;

D. washing the hydrosol with said aminodextran solution by magnetic separation and redispersion,

whereby to form separate single metal ferrite particles coated with an aminodextran.

4. The method of claim 1 in which the metal ion of said divalent metal salt is the Mn²⁺ ion.

5. The method of claim 1 in which said divalent metal salt is selected from the group consisting of a metal chloride, metal sulfate and metal nitrate salt, except that when barium is said divalent metal or is present in any of the steps A to C, said divalent metal salt is a metal chloride or a metal nitrate salt.

6. The method of claim 5 in which said divalent metal salt is selected from a mixture of metal chloride, metal sulfate and metal nitrate salts.

7. A colloidal ferrite particle produced by the method of claims 1 or 2.

2. The method of claim l in which the metal ion of said divalent metal salt is the Fe²⁺ ion.

3. The method of claim 2 in which said ferrous salt can be either a chloride or sulfate salt.

8. Colloidal particles which are monodispersed having a ferrite structure and a mean particle diameter of approximately 0.1 to 1.0 microns, said particles including the divalent metal ion manganese(II)) and characterized as being well-defined and of uniform size and shape.

9. The colloidal particles of claim 8 in which ferrite particles of manganese(II) display a ferrimagnetic response to a magnetic field.