Hach DR2400 - Page 719

Silica
Silica
Silica_PT_ULow_HTB_Eng_Ody.fm Page 5 of 6
3. Touch OK to accept the default values for standard concentration, sample
volume, and spike volumes. Touch
Edit to change these values. After values
are accepted, the unspiked sample reading will appear in the top row. See
Standard Additions in the instrument manual for more information.
4. Prepare three samples as instructed in the procedure. Fill three 250-mL
Erlenmeyer flasks with 50 mL of sample. Use the TenSette
®
Pipet to add
0.1 mL, 0.2 mL, and 0.3 mL of 1 mg/L (1000 µg/L) Silica standard,
respectively, to each flask and mix thoroughly.
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.
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 on page 32 for more information.
Standard Solution Method
1. Use the 500 µg/L SiO
2
Standard Solution listed under Required Standards in
place of the sample. Perform the silica procedure as described above.
2. To adjust the calibration curve using the reading obtained with the
500-µg/L Standard Solution, touch
Options on the current program menu.
Touch
Standard Adjust.
3. Touch
On. Touch Adjust to accept the displayed concentration (the value
depends on the selected chemical form). If an alternate concentration is used,
touch the number in the box to enter the actual concentration, then touch
OK.
Touch
Adjust.
For more information, see Section 3.2.4 Adjusting the Standard Curve on page 40.
Method Performance
Precision
Standard: 500 µg/L silica
See Section 3.4.3 Precision on page 44 for more information, or if the standard
concentration did not fall within the specified range.
Sensitivity
See Section 3.4.5 Sensitivity on page 44 for more information.
Program 95% Confidence Limits of Distribution
645 497.6–502.4 µg/L silica
Portion of Curve ∆Abs ∆Concentration
Entire range 0.010 12 µg/L silica