MACHEREY-NAGEL pH-Fix Test Strips

pH-Fix strips carry their indicator dyes chemically bonded to the cellulose rather than merely soaked into it. That single difference is what the whole product line is built on, and it matters in two ways at the bench.

Nothing bleeds into the sample

An ordinary impregnated strip leaches dye the moment it touches liquid. The sample is contaminated, which rules the strip out of anything that gets used afterwards — a culture, a batch, a reagent that has to stay clean. A bonded indicator leaves the sample exactly as it found it, so the strip can be dipped into product rather than into a decanted portion of it.

The reading does not wash out

Because the dye stays put, the colour holds for documentation and the strip can be rinsed without losing the result. On a bleeding strip a wet sample or a careless rinse takes the answer with it.

Choosing the range

The line covers pH 0 to 14 in seventeen ranges. Wide range (0–14) tells you where a sample sits when you do not know; narrow ranges resolve much more finely once you do.

Working rule: use the widest range once, then order the narrow range that brackets the answer. A strip reading 4.0–7.0 resolves a pH 5 sample several times better than a 0–14 strip does, and for process control that difference is the whole point of testing.

PT variants are supplied on a plastic backing strip rather than plain paper — stiffer to handle with gloves and wet fingers, and they do not curl.

All ranges read against the colour scale printed on the pack.