WTW Technical Buffer Solution TEP 7, pH 7.00, 1,000 ml, 108702

Before a pH electrode can provide reliable readings, it must be calibrated, and this requires a stable technical buffer solution with a pH of 7. The WTW technical buffer solution pH 7.00 provides the neutral reference point for 2- or 3-point calibration, as routinely carried out in laboratories in the pharmaceutical, industrial, research and water analysis sectors. It is available in three container sizes ranging from 50 ml to 1,000 ml, depending on how frequently calibration is carried out and how many electrodes are in use.

Why calibrate regularly

The glass membrane of a pH electrode changes over time; ageing, deposits or temperature fluctuations cause the slope of the calibration curve to shift. Without regular calibration against a known buffer solution, measured values gradually drift without this being immediately apparent. A fresh technical buffer solution with a defined pH value and documented accuracy is therefore essential for reliable measurement results, regardless of the pH meter or electrode type used.

Phosphate buffer with documented accuracy

The technical buffer solution pH 7 is based on a phosphate buffer comprising disodium hydrogen phosphate and potassium dihydrogen phosphate. At 20 °C, the pH value is exactly 7.00, with an accuracy of ± 0.03 pH. This tight tolerance ensures reproducible calibration, regardless of the electrode or measuring instrument used. Particularly when several measuring points or sites require the same reference, documented, consistent accuracy forms the basis for comparable results.

The neutral reference point for 2- or 3-point calibration

In practice, pH 7 is usually the first point in a 2- or 3-point calibration, typically supplemented by pH 4 and pH 10. If you have all three buffer levels in stock, you will fully cover the measurement range relevant to most applications. A simple 1-point calibration at pH 7 only indicates whether the electrode’s zero point is correct, but says nothing about the slope of the calibration curve outside the neutral range. For measurements that must also be reliable in the acidic or alkaline ranges, at least a second calibration point is therefore advisable. We also offer the same technical buffer solution with pH 4.01 and, in trace quality, with pH 10.01.

WTW, a brand of Xylem

The buffer solution is supplied by WTW, an established brand in pH measurement technology and electrochemistry, which is now part of Xylem. Many laboratories already rely on WTW measuring instruments and electrodes; this technical buffer solution is suitable for them as a matched calibration solution. In principle, however, the buffer solution can be used with any pH electrode and any pH meter, regardless of the manufacturer; calibration is not tied to a specific measuring instrument.

Pack sizes for the technical buffer solution pH 7

Select the appropriate pack size above: STP 7 as a 50 ml bottle for economical use or as a supplement in an electrode case, TPL 7 with 250 ml for routine laboratory work, and TEP 7 with 1,000 ml for frequent calibration requirements or multiple measuring points.

Storage, shelf life and handling

At 20 °C, the buffer solution has a density of 1.01 g/cm³ and a melting point of -0.3 °C. Unopened, it has a shelf life of 3 years when stored at 15 to 25 °C. It is not classified under GHS/CLP and is not a dangerous good, which significantly simplifies storage, handling and dispatch in day-to-day laboratory work; there are no special dangerous goods requirements or labelling regulations to observe.

Avoid contamination

To ensure that the calibration remains reliable throughout the entire shelf life, buffer solution that has been removed should not be poured back into the bottle. Even minor contaminants from the measurement environment or the electrode can alter the pH value of the remaining solution and distort subsequent calibrations. For daily use, it is therefore advisable to use a small calibration vessel into which only as much buffer solution is poured as is required for the current calibration. The bottle itself should be kept tightly sealed and stored at a temperature between 15 and 25 °C to ensure that the documented accuracy of ± 0.03 pH is maintained until the end of the three-year shelf life.

Typical applications

The technical buffer solution pH 7 is used wherever pH electrodes need to be calibrated regularly:

• Routine calibration of pH electrodes in pharmaceutical quality assurance
• Water analysis, for example in drinking water and process water monitoring
• Process control in industry, wherever pH values in the neutral range are monitored
• Research and teaching, as a reliable reference point for measurement series
• Commissioning and functional testing of new pH electrodes prior to first use

Technical details

Scope of delivery

• 1 bottle of WTW technical buffer solution pH 7.00 in the selected container size (50 ml, 250 ml or 1,000 ml)

Individual requirements and procurement service

For complete 3-point calibration, we also offer the same technical buffer solution with pH 4.01 and, in trace quality, with pH 10.01, as well as suitable pH electrodes. If you have larger requirements, need custom container sizes or have any questions about the appropriate calibration solution, our procurement service will be happy to assist you.