Chromium, Hexavalent
Chromium, Hexavalent
Page 4 of 6
ChromiumHex_AVPP_Other_DCH_Eng_Ody.fm
5. For analysis using powder pillows, use the TenSette
®
Pipet to add 0.1 mL,
0.2 mL, and 0.3 mL of standard, respectively to three 25-mL samples and mix
thoroughly. Transfer 10 mL of each solution into a 10-mL sample cell and
analyze as described above.
Note: For AccuVac ampules, fill three mixing cylinders (Cat. No. 1896-41) with 50-mL of sample
and spike with 0.2 mL, 0.4 mL, and 0.6 mL of standard. Transfer 40 mL from each of the
three mixing cylinders to three 50-mL beakers. Analyze each standard addition sample as
described in the procedure above.
6. Accept each standard additions reading by touching Read. Each addition
should reflect approximately 100% recovery.
7. 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
Prepare a 0.25-mg/L Cr
6+
standard solution daily, as follows:
1. Using a 5.00 mL pipet (Cat. No. 14515-37) transfer 5.00 mL of Hexavalent
Chromium Standard Solution, 50 mg/L, into a Class A 1000-mL volumetric
flask (Cat. No. 14574-53).
2. Dilute to the mark with deionized water.
3. To adjust the calibration curve using the reading obtained with the
0.25-mg/L standard solution, touch
Options on the current program menu.
Touch
Standard Adjust.
4. 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.
Perform the hexavalent chromium procedure as described above. See Section
3.2.4 Adjusting the Standard Curve on page 40 for more information.
Method Performance
Precision
Standard: 0.25 mg/L Cr
6+
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
90 0.24–0.26 mg/L Cr
6+
95 0.24–0.26 mg/L Cr
6+
Program Portion of Curve ∆Abs ∆Concentration
90 Entire range 0.010 0.01 mg/L Cr
6+
95 Entire range 0.010 0.01 mg/L Cr
6+
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