Quaternary Ammonium Compounds
Quaternary Ammonium Compounds
QuaternaryAmmCom_PP_Other_DBC_Eng_Ody.fm Page 3 of 4
Sample Collection, Storage, and Preservation
Collect samples in glass bottles that have been rinsed several times with sample
before final sample filling. Do not use plastic containers as plastic adsorbs QACs.
Acidify the sample to a pH of less than 2. Store at 4 ±2 °C.
Accuracy Check
Standard Additions Method (Sample Spike)
1. After reading test results, leave the sample cell (unspiked sample) in the
instrument.
2. Touch
Options. Touch Standard Additions. A summary of the standard
additions procedure will appear.
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. Open a QAC Standard Solution, 100-mg/L CTAB.
5. Prepare three sample spikes. Fill three sample cells with 25 mL of sample. Use
the TenSette
®
Pipet to add 0.1 mL, 0.2 mL, and 0.3 mL of standard,
respectively, to each sample and mix thoroughly.
6. 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
should increase the QAC reading by 0.4 mg/L CTAB.
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 5.0-mg/L CTAB standard solution as follows:
1. Pipet 5.0 mL of QAC Standard, 100-mg/L as CTAB, into a 100-mL
volumetric flask. Dilute to the mark with deionized water. Mix well. Prepare
this solution daily. Perform the quaternary ammonium compound procedure
as described above.
2. To adjust the calibration curve using the reading obtained with the 5.0-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.
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