4001 Photometry Series0 pages

Measurement
and Control

4001 series
The photometric method
In recent decades, photometry has developed as an essential means of
analysis because it enables the “quantitative” determination of both organic
and inorganic compounds.
The technique uses the colorimetric methods characteristic of certain analytes,
i.e. the properties of certain chemical reagents to develop colour with an
intensity proportional to the concentration of a given substance, at a
particular wavelength of the spectrum visible between the UV and IR (from
400 to 800 nm).
Compared to UV or IR spectrophotometry, the colorimetric technique has the
tremendous advantage of relying on well-dened linear reactions with few
well-known interfering substances.

The Palin method employs the interactive DPD principle to determine the concentration of certain oxidants such as: free
chlorine, total chlorine, chlorine dioxide, ozone, peracetic acid, bromine, permanganate etc.
The DPD reacts with the oxidant present in the water, almost instantly producing a pink colour, making sure that all
those factors that may affect measurement (pH, μS, °C, organic matter etc.) have no inuence on the analytical
methodology.

The phases of the 4001 measuring cycle are:
• Entry of the sample in the measuring cell for
washing/priming
• First measurement on the sample as is
( photometric zero )
• Reagents introduced via peristaltic pump
• Development of the reaction through stirring
• Reading of the colour ( absorbance ):
The differential measurement between the zero
and the absorbance is processed by the
electronic processor and converted into a
concentration value, using specic correlation
tables developed in our laboratories.
The electronic controller displays the substance
measured in mg/l and decides whether or not to
activate the dosing components designed to
control or correct it.
The running and maintenance costs are very low
and, especially, system calibration takes place
automatically at each measuring cycle.
Industrial applications include the analysis of
drinking and waste water as well as the analysis
of food products, pharmaceuticals, chemicals etc.