YES Background Knowledge Quality Management Conductivity Temperature Coefficient pH Measurement YES Quality Management 100210

Conductivity - Temperature Coefficient This important topic is often unknown and often neglected in hemodialysis. A solution’s conductivity will change according to temperature. With increasing temperature, the measured solution’s conductivity will increase, too. To achieve meaningful measurement results, the conductivity value displayed is compensated to 25°C. In other words, the display is always converted to a solution temperature of 25°C. The temperature coefficient which the displayed value is compensated with is expressed as %/°C. Unfortunately however, different solutions also have different temperature coefficients. To achieve an exact measurement, the instrument will have to be adjusted to the temperature coefficient of the measured solution. The average temperature coefficient for dialysate is 2.07 %/°C.

Dialysis Machine Manufacturer Temperature Coefficient Temperature Coefficient – Values used in Dialysis To make technicians life interesting, different manufacturers of dialysing machines use different temperature coefficients. The following values are used:   Dialysis Machine Manufacturer Temperature Coefficient Baxter (European Machine) 2.20%/°C B.Braun 2.00%/°C Fresenius 2.10%/°C Gambro (not the US Phoenix Machine) 1.80%/°C Hospal 2.07%/°C Nikkiso Bicarbonate conductivity Total conductivity 2.02%/°C 2.05%/°C

Conductivity of Solution Temperature of Solution Temperature Coefficient - Differences Example calculation for an incorrect temperature coefficient, using a dialysate with a temperature coefficient of 2.07 %/°C: Conductivity of Solution Temperature of Solution Instrument Temp. Coefficient Display Difference in Values 14.00 mS/cm 37.0 °C 2.07 %/°C 0.00 % 1.97 %/°C 14.17 mS/cm 1.21 % Thus, this example illustrates that the user must set the temperature coefficient correctly in order to ensure accurate conductivity measurements.

Temperature Coefficient – Which value you should use If you have machines from one manufacturer Use the temperature coefficient that the dialysis machine uses for compensation. If you have different types of dialysis machines The best solution is to use a temperature coefficient of 2.07 %/°C for all machines. This avoid confusion with different readings of the conductivity on different machines.

No, measuring pH is easy if… pH Measurement pH, a mystery? No, measuring pH is easy if… things such as calibration and electrode handling are done correctly.

pH is one of the most common laboratory measurement pH Measurement - Fundamentals Why is pH Important? pH is one of the most common laboratory measurement because many chemical processes are dependent on pH. The speed or rate of chemical reactions can often be significantly altered by changing the pH of the solution. The solubility of many chemicals in solution, and their bio-availability is dependent on pH. The physiological chemistry of living organisms usually has very specific pH boundaries.

pH = -log10aH+ What is pH? pH is the negative log pH Measurement - Fundamentals What is pH? The term pH derives from a combination of p for the word power and H for the symbol of the element Hydrogen. pH is the negative log of the activity of hydrogen ions. pH = -log10aH+

pH Measurement - Fundamentals pH represents the 'activity' of hydrogen ions in a solution, at a given temperature. The term activity is used because pH reflects the amount of available hydrogen ions not the concentration of hydrogen ions.

pH is a Measure of Acidity pH Measurement - Fundamentals pH is a Measure of Acidity The pH scale for aqueous solutions ranges from 0 to 14 pH units, with pH 7 being neutral.

pH Measurement principal

pH Measurement Electrode Combination pH electrodes are combinations of one reference electrode and one measuring electrode in a glass tube. The glass body is often protected with a plastic coat and due to the gel-electrolyte-filling, it is maintenance-free. The electrode`s diaphragm must be stored in 3 mol/l KCl-solution. The protective cap must be refilled every three to four weeks to prevent the electrode from drying out. Crusts caused by leaking electrolyte can be removed easily by rinsing with RO water.

pH Measurement – What is important Before use the electrode must be checked for exterior damage or crushed glass. The sample volume should be 100 ml of dialysate or 1 liter of untreated water. The sample should be poured into a clean glass container with tube or hose, coming into as little contact with air as possible. The pH-value must be measured immediately in the same container. Make sure that the display stabilizes before the value is read. In stirred solutions the response rate is faster; the value, however, must be measured at resting fluid.

pH Measurement – What is important The pH-electrode must be dabbed only with a lint-free cloth and never rubbed dry. Rubbing destroys the jelly layer on the glass surface which results in a longer response time for the electrode. Before taking measurements, remove the rubber cap. If the mobility of the plastic part is restricted it can be released by rinsing with lukewarm water. Pressure and fluid currents have considerable influence on the pH measurements. Therefore, it is essential to take the pH measurement in a resting solution at environmental pressure.

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