Analytical method and apparatus therefor involving continuous titration
The present invention relates to an improved analytical method and apparatus therefor, in particular to a method and apparatus for continuous titration in which at least one parameter of at least one compound in a test mixture may be monitored as the composition of the mixture is continuously varied. The method comprises the steps of continuously mixing at least two component fluid streams to form a test mixture stream and passing the test mixture stream through a spectrophotometric detection zone, with the volume to volume ratio of at least two of the component streams forming the test mixture stream continuously and linearly varied with time by alteration of the relative proportions of the component streams forming the test mixture, while the total volume of the test mixture stream remains constant.
1. A method of continuous titration in which at least one parameter of at least one compound in a test mixture may be monitored as the composition of the mixture is continuously varied by changing the concentration of one or more species in the mixture, the method comprising the steps of continuously mixing at least two component fluid streams to form a test mixture stream and passing the test mixture stream through a spectrophotometric detection zone, characterised in that the volume to volume ratio of at least two of the component streams forming the test mixture stream is continuously and linearly varied with time by alteration of the relative proportions of the component streams forming the test mixture, whilst the total volume of the test mixture stream remains constant.
2. A method according to claim 1 wherein the test mixture stream is formed from three component fluid streams, the proportion of one component fluid stream remaining constant, the proportions of the second and third component fluid streams being variable in inverse proportion to one another.
3. A method according to claim 2 wherein the variable component streams comprise buffer solutions, test reagents, aqueous or organic solvents.
4. A method according to claim 2 wherein the spectrophotometric detection zone comprises a multiwavelength spectrophotometric detector.
5. A method according to claim 4 wherein the spectrophotometric detector is an ultraviolet or visible range spectrophotometer, a fluorimeter, a polarimeter, a colourimeter, or a light scattering, optical rotation or circular dichrosim detector.
6. A method according to claim 5 , wherein the spectrophotometric detector is a scanning ultraviolet or visible range spectrophotometer.
7. A method according to claim 1 wherein the variable component streams comprise buffer solutions, test reagents, aqueous or organic solvents.
8. A method according to claim 7 wherein there are at least two variable components, comprising two linearising buffer solutions.
9. A method according to claim 8 wherein the linearising buffers are formed from acidic and basic components derived from the same compound such that the overall chemical composition of the test mixture stream remains constant during titration as the relative proportions of the two linearising buffers are changed.
10. A method according to claim 9 wherein the acidic and basic components include citric acid, potassium citrate, KH 2 PO 4 , K 2 HPO 4 , HCI and KOH.
11. A method according to claim 1 wherein the spectrophotometric detection zone comprises a multiwavelength spectrophotometric detector.
12. A method according to claim 11 wherein the spectrophotometric detector is an ultraviolet or visible range spectrophotometer, a fluorimeter, a polarimeter, a colourimeter, or a light scattering, optical rotation or circular dichrosim detector.
13. A method according to claim 12 , wherein the spectrophotometric detector is a scanning ultraviolet or visible range spectrophotometer.
14. A method of continuous titration comprising mixing a flowing fluid stream comprising a compound under test mixture stream and passing the test mixture stream to form a test mixture stream and passing the test mixture stream through a spectrophotometric detection zone at which readings relating to at least one physical or chemical parameter of the compound under test are taken, characterised in that the test mixture stream is passed through the spectrophotometric detection zone at a constant flow rate and that the flow rate of at least two of the flowing fluid streams forming the test mixture stream is continuously and linearly varied with time by alteration of the relative proportion of the component streams forming the test mixture, whilst the total volume of the test mixture stream remains constant.
15. A method according to claim 14 , wherein the spectrophotometric detection zone comprises a multiwavelength spectrophotometric detector.
16. A method according to claim 15 wherein the spectrophotometric detector is an ultraviolet or visible range spectrophotometer, a fluorimeter, a polarimeter, a colourimeter, or a light scattering, optical rotation or circular dichrosim detector.
17. A method according to claim 16 , wherein the spectrophotometric detector is a scanning ultraviolet or visible range spectrophotometer.