APERA INSTRUMENTS / PH 4.00 BUFFER / AI1102 / AI1102-L

The everyday acid-side point.

Apera’s pH 4.00 buffer is the acid-side point used in nearly every two- and three-point pH calibration. It is standardized against NIST certified pH references to within 0.01 pH at 25°C (77°F), color-coded red, and works with any brand of pH meter, tester or controller.

It has a two-year shelf life with the expiration date printed on the bottle, and the label carries a pH-versus-temperature chart so you can read the true buffer value at your solution temperature. Apera lists it as non-hazardous and not subject to DOT shipping restrictions. Choose an 8 oz (AI1102) or 16 oz (AI1102-L) bottle from the size menu.

Where pH 4.00 fits
in your calibration.

Calibrate at pH 7.00 first, then pH 4.00. For samples that stay below pH 7, that two-point calibration covers your range; add pH 10.01 when samples run alkaline.

pH 4.00 belongs to the USA buffer series that Apera meters recognize automatically (1.68, 4.00, 7.00, 10.01, 12.45). Meters set to the NIST series expect pH 4.01 instead.

Pour it out.
Never dip into the bottle.

Pour only what you need into a clean cup or a CalPod organizer, close the bottle straight away, and never pour used buffer back. Rinse the electrode with distilled or deionized water before it goes into each buffer so one solution does not carry into the next.

Calibrate at your sample temperature when you can. Buffer pH shifts slightly with temperature; meters with automatic buffer recognition apply the correction, and the chart on the label gives the value if yours does not.

Both sizes carry the same pH 4.00 buffer and the same specification. The 8 oz bottle suits occasional calibration and field kits; the 16 oz bottle suits labs that calibrate daily or run several meters.