Process and apparatus for testing for substances in liquids

• US 5,912,180 A
• Filed: 01/09/1997
• Issued: 06/15/1999
• Est. Priority Date: 08/13/1993
• Status: Expired due to Term

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: Hybrivet Systems, Inc. (3M Company)
• Inventors: Stone, Marcia J.
• Primary Examiner(s): Hutzell, Paula K.
• Assistant Examiner(s): BAKALYAR, HEATHER
• Application Number:
  US08/781,580
• Time in Patent Office: 887 Days
• Field of Search: 436/77, 436/76, 436/73, 436/80, 436/81, 436/84, 436/164, 436/174, 436/175, 436/177, 436/178
• US Class Current: 436/77
• CPC Class Codes: G01N 1/34 Purifying; Cleaning processes or apparatus for extracting or separating nucleic acids from biological samples C12N15/1003
• CPC Class Codes: G01N 1/4077 by other techniques involving separation of suspended solids
• CPC Class Codes: G01N 31/22 using chemical indicators G01N31/02 takes precedence
• CPC Class Codes: G01N 31/221 for investigating pH value
• CPC Class Codes: G01N 33/1813 specific cations in water, e.g. heavy metals electrochemical analysis G01N27/26; detection of ions by colorimetry G01N31/22
• CPC Class Codes: Y10T 436/25 including sample preparation
• CPC Class Codes: Y10T 436/25125 Digestion or removing interfering materials
• CPC Class Codes: Y10T 436/25375 Liberation or purification of sample or separation of material from a sample [e.g., filtering, centrifuging, etc.]
• CPC Class Codes: Y10T 436/255 including use of a solid sorbent, semipermeable membrane, or liquid extraction

Abstract

A method for detecting a substance in a liquid sample involves precipitating a substance from the liquid sample and filtering it from the liquid sample. The precipitate is then tested for the substance of interest by contacting the precipitate with a dye that forms a visible reaction when exposed to the substance. A releasing agent may be used after filtering the precipitate and prior to testing the precipitate with a dye. In another embodiment, the sample is filtered without the prior use of a precipitating agent.

Claims

1. A method for detecting lead in a liquid sample comprising:

mixing the liquid sample with a first reagent that comprises borate and causes the lead to precipitate;

filtering the precipitate from the liquid sample; and

testing the precipitate for lead by contacting the precipitate with a second reagent that forms a calorimetric reaction when exposed to lead.

2. The method of claim 1, further comprising pretreating the liquid sample with an oxidizing agent prior to mixing the liquid sample with the first reagent.

3. The method of claim 2, wherein the oxidizing agent comprises sodium hypochlorite.

4. The method of claim 1, wherein the first reagent further comprises a buffer and a carrier metal that has less affinity for the second reagent than lead.

5. The method of claim 4, wherein the carrier metal comprises zinc acetate.

6. The method of claim 1, wherein the second reagent comprises sodium rhodizonate.

7. A method for detecting a metal selected from the group consisting of lead, cadmium, bismuth, mercury, cobalt, iron, and copper in a liquid sample comprising:

mixing the liquid sample with borate to cause the metal to precipitate;

filtering the precipitate from the liquid sample; and

testing the precipitate for the metal by contacting the precipitate with a reagent that forms a calorimetric reaction when exposed to the metal.

8. The method of claim 7, further comprising pretreating the liquid sample with an oxidizing agent prior to mixing the liquid sample with the borate.

9. The method of claim 8, wherein the oxidizing agent comprises sodium hypochlorite.

10. The method of claim 7, wherein the sample is also mixed with a buffer and a carrier metal that has less affinity for the reagent than the metal to be detected.

11. The method of claim 10, wherein the carrier metal comprises zinc acetate.

12. The method of claim 7, wherein the metal is lead and the reagent comprises sodium rhodizonate.