It’s often very important to know the pH of the water you’re using in the lab, to ensure that thepH of the solutions you are using are within the optimal range for your experiments.
Due to the very nature of ultrapure water,you can’t simply assess the pH with a general lab electrode, that detects ions in the waterto determine the pH. Whenever making electrodereading unreliable -just one part per billion H+ or 150 ppb CO2 is all that is required in order to shiftthe pH, Pure water contains a low and unstable extent of ions. Ok, the title above isn’t exactly true… pH is a measure of acidity or alkalinity, determined bythe state of dissociation of numerous molecules. Whenever maintaining a stable and reproducible pH can be vital for accurate results, Carefullycontrolling pH is important across a huge swathe of laboratory work, from enzymatic assays,chemical reactions and analytical analyses to creating buffers, solutions and cell culture media, in nearly any case.
No ‘contaminants’, no pH?
The pH of ultrapure water may be easily influenced by CO2 presentin the air that diffuses into the solution. Conductivity and resistivity are measures of the flow of electrons through the fluid, and both canbe directly correlated to the concentration of ions in the solution. We need a replacement for measuring pH, with intention to get around this issue. Any trace amounts of acid or base in your samplingcontainer will also have an effect, as will any contamination in the pH electrode calibrationbuffers themselves. Determining the pH of ultrapure water provides no real practicalinsight, as such. Furthermore, the fact that pure water contains such low levels of ions was the answer to this problem. Usually, theresistivity decreases allowing us to predict the pHrange of the solution, as pH shifts beyond 0.
At a resistivity of 182 MΩ.
Making use of an alternative measure likeresistivity overcomes this inherent problem. MΩ. Remember, without risking contamination or generating inaccurate results fromusing traditional electrodes, now this means you canassess the pH of your water. Essentially, the use of conventional pH probes or litmus/pH test papers should not give you reliable resultswhen assessing the true pH of high purity water. Oftentimes this knowledge can be usedto estimate the pH range at any resistivity value, let’s say, a solution with a resistivity of 5MΩ.
The indirect solution.
You may use these HTML tags and attributes. Water is distilled to reduce CO2 before using it to dissolve test samples for pH measurements. Eventually, the practice in pharmaceutical laboratories is to add a few drops of KCl solution to the pure water sample before taking the pH reading with a pH electrode.
Resistivity is a measure of all ions, not simply H+ and OH-, while pH is a measure of the presence of hydrogen or hydroxide ions.
It’s a well-known fact that the concentration of these latter two will affect pH, in water. Carbon dioxide and alkalinity. We hope this answers your question! Nonetheless, other impurities have no effect on the pH of water. We hope this answers your question! Actually the concentration of these latter two will affect pH, in water. Carbon dioxide and alkalinity. Resistivity is a measure of all ions, not merely H+ and OH-, while pH is a measure of the presence of hydrogen or hydroxide ions. Besides, other impurities have no effect on the pH of water.