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avoid contamination of the stock standard solution.
3. Perform volumetric pipette solution transfer at room temperature. Aqueous standard solutions stored at ‘lower’ temperature
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or the concentrations units are in wt./wt. rather than wt./volume.
4. Never use glass pipettes or transfer devices with standard solutions containing HF. Free HF attacks glass but it is sometimes
considered safe to use glass when the HF is listed as trace and/or as a complex. However, many fluorinated compounds will
attack glass just as readily as free HF.
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calculated provided the density of the standard solution is known. There are too many possible pipetting errors to risk a
volumetric transfer without checking the accuracy by weighing the aliquot.
6. Uncap your stock standard solutions for the minimum time possible. This is to avoid transpiration concentration of the
analytes as well as possible environmental contamination.
7. Replace your stock standard solutions on a regular basis. Regulatory agencies recommend or require at least annual
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UIF possibility of an operator error through general usage (more info)*. A mistake may occur the first time you use the stock
standard solution or it may never occur with the probability increasing with use and time. In addition, the transpiration
concentration effect occurs whether the standard solution is opened / used or not and increases with use and increased vapor
space (transpiration rate is proportional to the ratio of the circumference of the bottle opening to vapor space).
Calculations
The concentration units for chemical standard solutions used for ICP applications are typically expressed in μg/mL
(micrograms per milliliter) or ng/mL (nanograms per milliliter). For example, a 1000 μg/mL solution of Ca+2 contains 1000
micrograms of Ca +2 per each mL of solution and a 1 μg/mL solution of Ca+2 contains 1000 ng of Ca+2 per milliliter of solution.
To convert between metric concentration units the following conversions apply:
The difference between ppm and μg/mL is often confused. A common mistake is to refer to the concentration units in ppm as
a short cut (parts per million) when we really mean μg/mL. One ppm is in reality equal to 1 μg/g. In similar fashion ppb (parts
per billion) is often equated with ng/mL. One ppb is in reality equal to 1 ng/g. To convert between ppm or ppb to μg/mL or
ng/mL the density of the solution must be known. The equation for conversion between wt./wt. and wt./vol. units is:
(μg/g) (density in g/mL) = μg/mL and/or (ng/g) (density in g/mL) = ng/mL
Suffix
kilo- (k)
milli- (m)
micro- (μ)
nano- (n)
pico- (p)
= 103
= 10-3
= 10-6
= 10-9
= 10-12
= 1000 g
= 0.001 g
= 0.000001 g
= 0.000000001 g
= 0.000000000001 g
kilogram (kg)
milligram (mg)
microgram (μg)
nanogram (ng)
picogram (pg)
Scientific Notation Decimal Equivalents Example Units
Table 3.1: Mass portion of concentration unit where g = gram
Suffix
milli- (m)
micro- (μ)
nano- (n)
pico- (p)
= 10-3
= 10-6
= 10-9
= 10-12
= 0.001 L
= 0.000001 L
= 0.000000001 L
= 0.000000000001 L
milliliter (mL)
microliter (μL)
nanoliter (nL)
picoliter (pL)
Scientific Notation Decimal Equivalents Example Units
Table 3.2: Volume portion of concentration unit where L = liter