Analytical method and apparatus

• US 8,513,022 B2
• Filed: 12/18/2008
• Issued: 08/20/2013
• Est. Priority Date: 12/20/2007
• Status: Expired due to Fees

• Current Assignee: Orica Australia Pty Limited (Orica Limited)
• Original Assignee: Cyantific Instruments Pty., Ltd.
• Inventors: Ross, Fraser John
• Primary Examiner(s): Soderquist, Arlen
• Application Number:
  US12/808,634
• Publication Number:
  US 20110039347A1
• Time in Patent Office: 1,706 Days
• Field of Search: 436/106, 436/109, 436/164, 436/167, 436/174, 436/181, 436109111-113, 436/129, 436177-178, 422/62, 422/68.1, 422 80- 81, 422/82.05, 422/82.09, 422/83, 422/88, 422/91
• US Class Current: 436/109
• CPC Class Codes: G01N 1/4055 by solubility techniques
• CPC Class Codes: G01N 2001/4066 using difference of solubility between liquid and gas, e.g. bubbling, scrubbing or sparging
• CPC Class Codes: G01N 31/16 using titration
• CPC Class Codes: Y10T 436/17 Nitrogen containing
• CPC Class Codes: Y10T 436/172307 Cyanide or isocyanide
• CPC Class Codes: Y10T 436/173845 Amine and quaternary ammonium
• CPC Class Codes: Y10T 436/174614 Tertiary amine
• CPC Class Codes: Y10T 436/175383 Ammonia
• CPC Class Codes: Y10T 436/201666 Carboxylic acid
• CPC Class Codes: Y10T 436/25 including sample preparation
• 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
• CPC Class Codes: Y10T 436/25875 Gaseous sample or with change of physical state

Abstract

A method for determining the amount of a chemical species in a sample, in particular the amount of weak acid dissociable cyanide or total cyanide in a sample, and an apparatus for performing said method. The method comprises the steps of: i) treating the sample to liberate the chemical species into a gaseous stream; ii) directing the gaseous stream to a scrubber; iii) absorbing the chemical species into a scrubber solution; and iv) determining the amount of chemical species absorbed into the scrubber solution, wherein any remaining chemical species not absorbed into the scrubber solution is directed or recirculated to the scrubber in the gaseous stream and step iii) is repeated to increase absorption of the chemical species prior to performing step iv).

Claims

1. A method for determining the amount of a chemical species in a known volume of sample solution, said method comprising the steps of:

i) treating the known volume of sample solution to liberate the chemical species into a gaseous stream within a closed system;

ii) directing the gaseous stream under positive pressure to a scrubber within the closed system;

iii) absorbing the chemical species into a scrubber solution; and

iv) determining the amount of chemical species absorbed into the scrubber solution, wherein any remaining chemical species not absorbed into the scrubber solution is directed or recirculated within the closed system under positive pressure to the scrubber in the gaseous stream and step iii) is repeated to increase absorption of the chemical species prior to performing step iv).

2. The method according to claim 1, wherein step iii) is repeated to an extent sufficient to maximise absorption of the chemical species prior to performing step iv).

3. The method according to claim 1, wherein treating the known volume of sample solution comprises mixing the known volume of sample solution with one or more reagents to facilitate liberation of the chemical species into the gaseous stream.

4. The method according to claim 3, wherein the mixing results in adjustment or control of the pH of the sample.

5. The method according to claim 4, wherein the chemical species is cyanide.

6. The method according to claim 5, wherein the cyanide is in the form of Weak Acid Dissociable (“

WAD”

) cyanide.

7. The method according to claim 6, wherein the mixed sample has a pH of from about pH 4 to about pH 5.

8. The method according to claim 5, wherein the cyanide is in the form of total cyanide.

9. The method according to claim 8, wherein the mixed sample has a pH<

1.

10. The method according to claim 5, wherein treating the known volume of sample solution comprises distilling the known volume of sample solution to liberate the cyanide into the gaseous stream.

11. The method according to claim 10, wherein the gaseous stream is recirculated continuously during distillation.

12. The method according to claim 10, wherein distillation converts the cyanide into HCN gas.

13. The method according to claim 12, wherein the HCN gas is absorbed into the scrubber solution by converting it to CN.

14. The method according to claim 1, wherein treating the known volume of sample solution comprises heating the sample to liberate the chemical species into the gaseous stream.

15. The method according to claim 1, wherein the scrubber solution comprises sodium hydroxide.

16. The method according to claim 1, wherein determining the amount of chemical species absorbed into the scrubber solution comprises performing a titration using the scrubber solution.

17. The method according to claim 1, wherein the gaseous stream is directed at a flow rate of from about 20 to 200 ml/min.

18. An apparatus for determining the amount of cyanide in a known volume of sample solution, said apparatus comprising:

i) a treatment unit for receiving the known volume of sample solution and liberating the cyanide into a gaseous stream within a closed system;

ii) a scrubber containing a cyanide absorbing scrubber solution for receiving the gaseous stream from the treatment unit and absorbing the cyanide into the cyanide absorbing scrubber solution within the closed system;

iii) a recirculation conduit for directing or recirculating within the closed system under positive pressure any cyanide not absorbed into the cyanide absorbing scrubber solution back to the scrubber in the gaseous stream to increase absorption of the cyanide;

iv) a measuring device for determining the amount of cyanide absorbed into the cyanide absorbing scrubber solution; and

v) a transfer pump for pumping the gaseous stream through the recirculation conduit.

19. An apparatus for determining the amount of a chemical species in a known volume of sample solution, said apparatus comprising:

i) a treatment unit for receiving the known volume of sample solution and liberating the chemical species into a gaseous stream within a closed system;

ii) a scrubber for receiving the gaseous stream from the treatment unit and absorbing the chemical species into a scrubber solution within the closed system;

iii) a recirculation conduit for directing or recirculating within the closed system under positive pressure any chemical species not absorbed into the scrubber solution back to the scrubber in the gaseous stream to increase absorption of the chemical species;

iv) a measuring device for determining the amount of chemical species absorbed into the scrubber solution; and

v) a transfer pump for pumping the gaseous stream through the recirculation conduit.

20. The apparatus according to claim 19, wherein the treatment unit comprises a mixing unit for mixing the known volume of sample solution with one or more reagents to facilitate liberation of the chemical species into the gaseous stream.

21. The apparatus according to claim 19, wherein the treatment unit comprises a heating unit for heating the known volume of sample solution to liberate the chemical species into the gaseous stream.

22. The apparatus according to claim 19, wherein the treatment unit comprises a distillation unit for distilling the known volume of sample solution to liberate the chemical species into the gaseous stream.

23. The apparatus according to claim 19, wherein the scrubber solution comprises sodium hydroxide.

24. The apparatus according to claim 19, wherein the measuring device is in contact with the scrubber solution in the scrubber such that the amount of chemical species is determined in situ.

25. The apparatus according to claim 19, wherein the recirculation conduit directs or recirculates any chemical species not absorbed into the scrubber solution back to the scrubber in the gaseous stream through at least one part of the treatment unit.

26. The apparatus according to claim 19, wherein the scrubber, the treatment unit, and the transfer pump are interconnected by the recirculation conduit, such that the transfer pump acts to pump the known volume of sample solution through the treatment unit to the scrubber and further acts to pump any chemical species not absorbed into the scrubber solution through the treatment unit back to the scrubber.