AQ1059

Buffer 7.00 Standard

$7.49 – $13.99

Buffer solution lets you calibrate any pH tester to ensure accuracy. Choose from pH 4, 7 or 10.

Solution helps you achieve the accuracy that’s critical for measuring pH in wastewater, storm water and process liquids.
Makes calibration easy – just adjust your tester to the pH measurement of the solution in a clean container.
Choose from pH 4, 7 or 10 solution.
If unopened, shelf life is 2 years; once opened, use pH 4 and pH 7 within 90 days, pH 10 within 30 days.

Packing:

$7.49

pH calibration challenge

To calibrate pH measuring systems you must use a solution with a known pH value, also known as pH reference or buffer pH solution. The accuracy of your subsequent pH measurements is dependent on how accurately the pH measuring system is calibrated, so particular attention must be paid to this step. Because there are a great number of different buffer pH solutions available many people are uncertain about how many and what pH calibration solutions should be used.

What is a buffer pH solution and how many pH calibration points are reasonable?

A buffer pH solution is composed of either a weak acid and the conjugated base or a weak base and the conjugated acid. The main characteristic of a buffer pH calibration solution is that the pH value of the solution will not alter when a small amount of acid or a base is added. The components and their concentration can cause the pH value of the calibration solution to vary across a large range e.g. with HCl and sodium citrate (pH 1–5), citric acid and sodium citrate (2.5–5.6), acetic acid and sodium acetate (3.7–5.6), Na₂HPO₄ and NaH₂HPO₄ (6–9), or borax sodium hydroxide (9.2–11).

The pH value of a calibration solution does not only alter with its composition but with temperature changes. Please see the table below showing the temperature behavior of reference pH buffer. The thermal characteristics of these calibration solutions have been determined by metrological institutes.

Temperature (°C)	pH 4	pH 7	pH 10
10	3.997	6.923	9.332
20	4.001	6.881	9.225
25	4.005	6.865	9.180
40	4.027	6.838	9.068
50	4.050	6.833	9.011

In contrast to reference pH calibration solutions the composition of technical buffer pH solutions is not regulated. So it is important to note that the temperature reaction of these solutions can vary, even if the same nominal pH value is specified at 25°C. In particular, at a calibration temperature other than 25°C, considerable errors can occur with pH measurement results.

One-point calibration: A one-point calibration is accomplished using one reference pH solution. Here only the zero point is verified.

Two-point calibration: This method uses two pH solutions with at least a two-unit difference. Because electrodes have strong linearity, this is accurate for most applications.

Multipoint calibration: Uses three or more pH solutions. A calibration curve is generated using regression or segmental analysis. R² indicates stability and should be close to 1.

Three-point calibration with Dawn buffer solutions (4, 7 and 10) increases accuracy for most pH measurements.

Disclaimer: Any of the above statements have not been evaluated by the Food and Drug Administration (FDA). This product is not intended to diagnose, treat, cure, or prevent disease. The information provided is general and should not be taken as medical advice. This product is for research use only. We strongly advise you to perform a test batch before use. If you suffer any adverse reactions or symptoms, please discontinue use immediately.