Polarographic System for Measurement of Dissolved Oxygen

Polarographic System for Measurement of Dissolved Oxygen -...

Info icon This preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Polarographic System for Measurement of Dissolved Oxygen Studies in modern biological science frequently require instrumentation, for measurements such as changes in a quantity with time. A basic recording setup includes a measurement device, a processing or coupling device, and a recorder. In a polarographic system the measurement device (transducer) is a Clark oxygen electrode. The processing/ coupling device is an oxygen monitor. The recording device is a flatbed strip chart recorder, or perhaps a computer-assisted data acquisition system. The solution or suspension to be assayed is placed in a sealed chamber that is exposed to the surface of a Clark oxygen electrode. This dissolved oxygen (D.O.) chamber contains one or more access ports for adding/removing materials. The medium is stirred to ensure homogeneity and to ensure that oxygen can freely diffuse into the electrode. The presence of oxygen causes the electrode to deliver a current to the oxygen monitor, which amplifies the current and converts it to a voltage output that is directly proportional to the concentration of oxygen in the chamber. The recorder moves a paper chart at constant speed, so that when the recorder pen moves in response to voltage changes, oxygen content is recorded as a function of time. For mitochondria studies our medium of choice consists of 70 mM sucrose, 220 mM mannitol, 2 mM HEPES buffer, 5 mM magnesium chloride, 5 mM potassium phosphate, 1 mM EDTA, and 0.1% fatty acid free bovine serum albumin, pH 7.4. In our results we refer to the rate at which total chamber oxygen declines as the oxygen consumption rate. Recommended components For polarographic systems we use custom made glass Gilson type DO chambers that hold a nominal volume of 2 ml. Gilson type chambers are designed with water jackets, however we haven't found it necessary to regulate temperature in our studies. We use the smallest availble "flea sized" stirring bars (maximum 5/16" l x 1/16" dia) to maintain laminar flow in the chambers. For dissolved oxygen detection we use Yellow Springs Instruments (YSI) #5331 Clark electrodes withYSI Model 5300 two channel biological oxygen monitors. We record data on Kipp & Zonen BD single channel chart recorders. Principle of the Clark oxygen electrode A Clark oxygen electrode is composed of two half cells separated by a salt bridge. A platinum electrode is separated from a solid silver electrode by insulating material. A concentrated potassium chloride solution is held in place over the surfaces of the electrodes by a teflon membrane which is attached by an O-ring that surrounds the electrodes. The oxygen monitor holds a constant voltage difference across the two
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
electrodes so that the platinum electrode is negatively charged with respect to the silver electrode.
Image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern