Combined titration and pH electrode for the preparation of liquid samples in particular for NMR spectroscopy

Abstract

An electrode rod (1;21) for a pH meter, comprising a measuring end (2; 22) for immersion into a liquid test sample (31), wherein the measuring end (2; 22) has a pH measuring element, and wherein electrical feed lines (5) in the electrode rod (1;21) extend towards the pH measuring element, is characterized in that at least one capillary (8, 9, 10; 23) for feeding a liquid into the test sample (31) extends in the electrode rod (1; 21), and the at least one capillary (8, 9, 10; 23) has an outlet opening (11, 12, 13; 24) in the area of the measuring end (2; 22). The inventive electrode rod facilitates and accelerates preparation of liquid test samples, in particular, adjustment of a pH value for small amounts of test samples or narrow sample containers.

Description

[0001] This application claims Paris Convention priority of DE 10 2005 060 866.3 filed Dec. 20, 2005 the complete disclosure of which is hereby incorporated by reference. BACKGROUND OF THE INVENTION [0002] The invention concerns an electrode rod for a pH meter with a measuring end for immersion into a liquid test sample, wherein the measuring end comprises a pH measuring element, and wherein electrical feed lines in the electrode rod extend towards the pH measuring element. [0003] An electrode rod of this type is disclosed e.g. in “IQ 240 Benchtop / Portable pH Meter” by I.Q. Scientific Instruments, Inc., San Diego, Calif., USA, 2001. [0004] When substances, e.g. proteins, are measured using modern methods of instrumental analytics, the measuring result is not only influenced by the substance itself but also by the measuring surroundings. In particular, in NMR spectroscopy of substances in aqueous solution, the pH value considerably affects the obtained spectra. [0005] A correlation b...

AI Technical Summary

Benefits of technology

[0015] The inventive electrode permits maintenance of the electrode rod immersed in a sample container in a test sample and at the same time direct supply of a fluid, in particular, acid or base to the test sample through the capillary of the electrode rod. Even when the test sample is kept in a narrow container, the electrode rod need not be removed in order to titrate the fluid. With the inventive electrode rod, the laboratory equipment need not be moved relative to the sample container during sample preparation between pH measurement and titration. This facilitates and accelerates iterative adjustment of the pH value of a test sample.

[0034] In another preferred embodiment, the titration unit also comprises a gas pump which may supply gas through a third, in particular, the lower capillary, and the control unit is designed to drive the gas pump, such that gas may also be supplied during and / or after supplying acid and / or base. This provides thorough mixing of the test sample and a balanced pH value is reached more quickly.

Problems solved by technology

In this case, iterative adjustment of the pH value in accordance with prior art is very difficult.

Due to the narrow sample container (e.g. a 2 ml glass vial with an opening width of approximately 5 mm), the electrode rod (smallest available outer diameter 3.8 mm) cannot remain in the sample container during titration of acid or base, since there is not enough space for pipettes.

For this reason, the laboratory equipment (electrode rod, mixer, acid pipette, base pipette) must be removed and reinserted from above the test sample a plurality of times during preparation of a small amount of liquid test sample, which renders preparation of such a test sample very time-consuming and therefore expensive.

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