Hardness, Total
Hardness, Total
Page 4 of 6
Hardness_MP_ULow_CPZ_Eng_2400.fm
Accuracy Check
Standard Additions Method (Sample Spike)
1. Touch
Options. Touch Standard Additions. A summary of the standard
additions procedure will appear.
2. Touch
Edit. Change the sample volume to read 25 mL. Change the Standard
Addition increments to 0.1 mL, 0.2 mL, and 0.3 mL. Touch
OK to accept these
values. After the values are accepted, the unspiked sample reading will
appear in the top row. See Standard Additions in the instrument manual for
more information.
3. Obtain a Calcium Chloride Standard Solution, 20-mg/L (20,000-µg/L) as
CaCO
3
.
4. Prepare three sample spikes. Use a TenSette
®
Pipet to add 0.1 mL, 0.2 mL, and
0.3 mL, of a 20-mg/L as CaCO
3
Calcium Chloride Standard to three 25-mL
samples, respectively.
5. Analyze each sample spike as described in the procedure above, starting with
the 0.1 mL sample spike. Accept each standard additions reading by touching
Read. Each addition should reflect approximately 100% recovery. Each 0.1 mL
addition of standard should cause an increase of 80 µg/L hardness as CaCO
3
.
6. After completing the sequence, touch
Graph to view the best-fit line through
the standard additions data points, accounting for matrix interferences. Touch
View: Fit, then select Ideal Line and touch OK to view the relationship between
the sample spikes and the “Ideal Line” of 100% recovery.
See Section 3.2.2 Standard Additions for more information.
Standard Solution Method
Using the 0.50-mg/L (500-µg/L as CaCO
3
) Calcium Chloride Standard Solution,
perform the procedure using the standard in place of the sample.
1. To adjust the calibration curve using the reading obtained with the 500-µg/L
as CaCO
3
Standard Solution, touch Options on the current program menu.
Touch
Standard Adjust.
2. Touch
On. Touch Adjust to accept the displayed concentration. If an
alternative concentration is used, touch the number in the box to enter the
actual concentration, then touch
OK. Touch Adjust.
See Section 3.2.3 Adjusting the Standard Curve for more information.
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