Influence Of Foreign Substances; Dosing Of Reagents - wtw PhotoLab S12-A Operating Instructions Manual

photoLab ® Series
2 Photometric Test Kits

2.2.5 Influence of Foreign Substances

2.2.6 Dosing the Reagents
8
Foreign substances in the sample solution can
•
raise the measurement value as a result of an amplification of the
reaction
•
ower the measurement value as a result of a prevention of the reaction.
A quantification of this effects is stated in tabular form in the respective
package inserts for the most important foreign ions. The tolerance limits
have been deter mined for the indi vidual ions; they may not be evaluated
cumulatively.
Suitability for use in seawater
A tabular survey (see appendix 1) provides infor mation on the suitability of
the tests in connection with seawater and also on the tolerances for salt
concentrations.
Small amounts of liquids are dosed by counting the number of drops from
a leak proof bottle.
When using dropper bottles it is extremely important that the
bottle be held vertically and that the drops be added slowly
m
(approx. 1 drop per second). If this is not observed, the cor-
rect drop size and thus the correct amount of reagent are not
achieved.
A positive-displacement pipette should be used for larger quantities of
liquid or for the exact dosage of smaller reagent quantities. In these cases
the reagent bottles are not fitted with a dropper insert.
Solid substances are dosed either with the dose-metering cap or with
microspoons that are integrated into the screw cap of the respective rea-
gent bottle. The dose-metering cap is used for solid reagents or reagent
mixtures that are free-flowing.
In all other cases the substances are dosed with the microspoon.
In this case it is necessary to add only level microspoonfuls. To this end
the spoon must be drawn over the brim of the reagent bottle.
At the first use replace the black screw cap of the reagent bottle by the
dose-metering cap.
Hold the reagent bottle vertically and, at each dosage, press the slide all
the way into the dose-metering cap. Before each dosage ensure that the
slide is completely retracted.
Reclose the reagent bottle with the black screw cap at the
m
end of the measurement series, since the function of the rea-
gent is impaired by the absorption of atmospheric moisture.
Release 01/2009