Page 10 - Chem Service 2016 Catalogue

It is often necessary to make a dilution of your chemicals in order to analyze them. Dilutions can be made in one of three
manners: weight/weight, weight/volume and volume/volume. The most common of these is weight/volume. The units of
measurement used are commonly expressed in parts per million (ppm), or parts per billion (ppb). For weight/weight, it is
expressed as 1ppm = 1ug/g, for weight/volume, 1ppm = 1ug/mL, and for volume/volume, 1ppm = 1ul/L. Chem Service
supplies most of their solutions at a concentration of 0.1mg/mL (100ug/mL or 100ppm). In order to make a solution at
a concentration of 100ppm, starting with a pure chemical, you need to know your fi nal volume. Then if the material is a
solid, the calculations are: Making Dilutions

0.1mg/mL (fi nal concentration) x 100mL (fi nal volume) = weight of chemical needed (10mg)
FC x FV = W

If the material is a liquid, it is usually easier to convert to a liquid measurement (i.e. ul), for handling purposes. Therefore,
the density is needed and the calculations are:

0.1mg/mL (fi nal conc.) x 100mL (fi nal volume) (fi nal conc.) x 100mL (fi nal volume) = volume (number of ul) of chemical needed density (mg/ul)
0.1mg/mL
FC x FV = V

d

If you need to make a further dilution from a prepared solution, the calculations would be basically the same format. For
example, to dilute 100ppm to 1ppm, take a 1mL aliquot of 0.1mg/mL (100ppm) solution, and dilute to your fi nal volume
(100mL).

0.1mg/mL (initial concentration) x 1mL (volume injected) (initial concentration) x 1mL (volume injected) x 1000ug1000ug (conversion factor) = 1ug/mL (fi nal concentration)
0.1mg/mL
100mL (fi nal volume) 1mg
IC x VI x CF = FC
FV

The above formula gives the fi nal concentration for the solution. The formula to obtain the volume to inject in order to make
the dilution for this fi nal volume is:

FC x FV x CF = VI
IC

As one can see, these calculations can be manipulated to allow you to achieve any fi nal volume or concentration you need.
They can also be used to convert to other types of concentrations (weight/weight or volume/volume).

LEGEND
FC = fi nal concentration IC = initial concentration
FV = fi nal volume = fi nal volume = fi nal volume = fi nal volume VI = volume injected
FV
FV
W = weight needed = weight needed = weight needed = weight needed
W W CF = conversion factor
V V
d = density V = volume needed = volume needed = volume needed = volume needed

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