All You Need to Know About pH Calibration Solutions

Lab calibration services use pH calibration solutions in numerous processes. pH calibration solutions, also known as pH buffers, are aqueous solutions that have well defined pH values. They contain chemicals that will maintain a constant pH, regardless of additions of small quantities of acids or bases, which means they have a buffering capacity. pH calibration solutions are an important tool with which you can measure pH using an electrode and a pH meter.

Some people try to make their own pH calibration solutions in an attempt to save money, but it is a bad idea to do so as you won’t be assured of stability of the solution nor its accuracy. You will end up wasting time and money, plus there is a risk of compromising on the accuracy of the results.

Types of pH Buffer Solutions

Equipment calibration system comprises of three main pH buffer solutions.

  1. Standard solution – The standard pH calibration solution has an accuracy of +/- 0.01 pH at 25°C (77°F). They come in seven different pH values that range from 1.60 to 10.01. The most commonly used buffers are 4.01, 7.01, and 10.01, which are dyed in different colors so that it is easy to identify them quickly.The standard pH solutions that are mainly used for instrument calibration are made in accordance with ISO standards and are NIST traceable. You can choose from a variety of sizes that range from single-use sachets to one-gallon jugs. It is important to remember that even though all the standard solutions are certified, not all of them come with a certificate. However, you may request one if you need it.
  2. Technical solution – These have the same accuracy as the standard pH solutions and follow the same specifications. Unlike standard pH solutions, all technical solutions come with a certificate.They come in a wider range as compared to basic solutions which hits nearly every point on the pH scale. This allows you to bracket your calibrations around any desired measurement. Bracketing is also known as two-point calibration or multi-point calibration. It basically consists of calibrating two pH points, one which is above the desired pH range and one below it. For example, if you want to measure the pH of a solution whose pH value is 2, you could use technical buffers 1.00 and 4.01 for a two-point calibration. This enhances the quality assurance process.
  3. Millesimal solution – The millesimal solutions are available in a wide variety of pH ranges, which are more than the standard buffers but less than the technical solutions. You get all the millesimal solutions with certificates. One factor that makes millesimal solutions unique is their greater accuracy. They are accurate to +/- 0.002, unlike technical and standard solutions that have an accuracy of +/- 0.01.Generally, these calibration solutions are used when an accuracy down to three decimal places is critical. You must use millesimal solutions to calibrate bench top pH meters and high performing portable meters to measure accurately down to 0.001 pH resolution.

Maintaining the pH Calibration Solutions

Several pH buffer solutions are packed in FDA approved light block bottles, which help in maintaining their pH values. The millesimal solutions come in blue, opaque bottles to keep out the light.

Never submerge the electrodes right into the bottle to keep the buffer from contaminating. Just pour the required amount into a container with deionized (DI) water, and use that for your calibration. Never pour the used buffer back into the bottle.

Get in touch with reputed lab calibration services like RS Calibrations in order to understand more about the different types of pH meter calibration solutions, which one to use for specific functions and learn how to maintain the solutions.

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