Hach DR2400 - Page 468

Nitrogen, Ammonia
Nitrogen, Ammonia
Page 4 of 6
NitrogenAmm_None_Other_NES_Eng_Ody.fm
7. After completing the sequence, the display will show the extrapolated
concentration value and the “best-fit” line through the standard additions
data points, accounting for matrix interferences.
See Section 3.2.2 Standard Additions on page 32 for more information.
Standard Solutions Method
1. To check accuracy, use a 1.0-mg/L Nitrogen Ammonia Standard Solution.
Or, prepare a 1.0-mg/L ammonia nitrogen standard solution by pipetting
1.00 mL of Nitrogen Ammonia Voluette
®
Ampule Standard, 50-mg/L, into a
50-mL volumetric flask. Dilute to the mark with deionized water. Prepare
this solution daily. Perform the Nessler procedure as described above.
2. To adjust the calibration curve using the reading obtained with the 1.0-mg/L
Nitrogen Ammonia 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: 1.00 mg/L NH
3
–N
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.
Distillation
1. Measure 250 mL of sample into a 250-mL graduated cylinder and pour into a
400-mL beaker. Destroy chlorine, if necessary, by adding 2 drops of Sodium
Arsenite Solution per mg/L Cl
2
.
2. Add 25 mL of Borate Buffer Solution and mix. Adjust the pH to about 9.5 with
1 N sodium hydroxide solution. Use a pH meter.
3. Set up the General Purpose Distillation Apparatus (Cat. No. 22653-00) as
shown in the Hach Distillation Apparatus Manual. Pour the solution into the
distillation flask. Add a stir bar.
4. Use a graduated cylinder to measure 25 mL of deionized water into a 250-mL
Erlenmeyer flask. Add the contents of one Boric Acid Powder Pillow. Mix
thoroughly. Place the flask under the still drip tube. Elevate so the end of the
tube is immersed in the solution.
Program 95% Confidence Limits of Distribution
380 0.93–1.07 mg/L NH
3
–N
Portion of Curve ∆Abs ∆Concentration
Entire range 0.010 0.02 mg/L NH
3
–N2