Selenium
Selenium
Page 6 of 8
Selenium_None_Other_DAB_Eng_Ody.fm
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 0.5-mg/L Se standard solution as follows:
1. Pipet 1.00 mL of a Selenium Standard Solution, 100-mg/L, into a 200-mL
volumetric flask. Dilute to volume with deionized water. Transfer 100 mL of
the standard into a 500-mL Erlenmeyer flask. Perform the test as described
above.
2. To adjust the calibration curve using the reading obtained with the 0.5-mg/L
standard solution, touch
Options on the current program menu. Touch
Standard Adjust.
3. Touch
On. Touch Adjust to accept the displayed concentration. If an alternate
concentration is used, touch the number in the box to enter the actual
concentration, then touch
OK. Touch Adjust.
See Section 3.2.4 Adjusting the Standard Curve on page 40 for more information.
Method Performance
Precision
Standard: 0.500 mg/L Se
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.
Summary of Method
An EDTA masking agent is added to the sample to remove interferences such as
iron prior to the test. The addition of a sulfate buffer adjusts the sample to the
optimum pH of 1 to 2. Under these conditions, diaminobenzidine reacts with all
selenium present as selenite (Se
4+
) to give a yellow-colored piazselenol complex
which is extracted and the color intensity measured colorimetrically. Selenium
present as Se
2+
and Se
6+
is not detected unless the sample is distilled. Test results
are measured at 420 nm.
Program 95% Confidence Limits of Distribution
640 0.486–0.514 mg/L Se
Portion of Curve ∆Abs ∆Concentration
Entire range 0.010 0.01 mg/L Se
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