Macherey-Nagel test strips for fluoride in water, in one presentation.
90734
A semi-quantitative test strip for fluoride in water. Dip it, wait the stated time, and compare the pad against the colour scale on the tube.
Fluoride has a narrow useful window: enough protects teeth, more than that mottles them permanently, and natural groundwater in some areas carries far more than any water authority would add. The number matters in both directions.
A strip gives a range, not a figure. That is enough for the great majority of decisions — dose or do not dose, discharge or hold, keep running or stop — and it gives the answer where the sample is, in about a minute, with no instrument to calibrate and nothing to carry back to a laboratory.
When a number has to be defensible — a regulatory report, a dispute, a limit you are close to — a photometer or a laboratory method is the right tool. The strip's job is to tell you whether you need one.
Aluminium and iron bind fluoride and hide it; a water high in either can read low and still be over the limit.
Supplied in one presentation.