Potassium – LaMotte DC1600 Colorimeter User Manual

Page 75

POTASSIUM

TETRAPHENYLBORON METHOD

CODE 3639

QUANTITY

CONTENTS

CODE

30 mL

*Sodium Hydroxide, 1.0N

*4004WT-G

5 g

*Tetraphenylboron Powder

*6364-C

Spoon, 0.05 g, plastic

0696

*WARNING: Reagents marked with a * are considered hazardous substances. Material Safety Data Sheets (MSDS) are supplied for

these reagents. For your safety, read label and accompanying MSDS before using.

Potassium, as the seventh most common element on the Earth’s surface and in the oceans, may be found in minor quantity

in most water supplies. It seldom exceeds 10 ppm in drinking water and usually is less than 2 ppm. In some brine or runoff

in agricultural areas the potassium concentration may reach 100 ppm.

APPLICATION:

Drinking, surface, and saline water.

RANGE:

1.0 – 10.0 ppm Potassium

METHOD:

Potassium reacts with sodium tetraphenylborate to form a colloidal white precipitate in

quantities proportional to the potassium concentration.

SAMPLE HANDLING

& PRESERVATION:

Store samples in polyethylene bottles, not in soft glass where leaching of potassium from the

glass may occur. Samples may be acidified to pH 2 with nitric acid, but should be neutralized

before analyzing.

INTERFERENCE:

Calcium and magnesium interfere at very high concentrations.

PROCEDURE

Rinse a clean colorimeter tube (0967) with sample water. Fill to the 10 mL line with sample.

Select setting 1 on “Select Wavelength” knob and press “30 Second Read” button.

Insert tube into colorimeter chamber and adjust to 100%T with “Set Blank” knob. This is the 100%T blank.

Remove tube from colorimeter chamber. Add 4 drops of *Sodium Hydroxide, 1.0N (4004WT). Cap and mix.

Use the 0.05 g spoon (0696) to add one measure of *Tetraphenylboron Powder (6364). Cap and shake vigorously

until all of the powder has dissolved. Wait 5 minutes.

At end of 5 minute waiting period, press “30 Second Read” button. Mix tube again to suspend any settled precipitate

and immediately insert into colorimeter chamber. Record %T as soon as reading stabilizes.

Consult calibration chart to determine potassium concentration in parts per million (ppm).

DC1600 POTASSIUM CALIBRATION CHART

1.01

1.08

1.14

1.20

1.26

1.32

1.38

1.44

1.50

1.56

1.61

1.67

1.72

1.77

1.82

1.87

1.92

1.97

2.02

2.06

2.11

2.15

2.20

2.24

2.28

2.32

2.36

2.40

2.43

2.47

2.51

2.54

2.58

2.61

2.64

2.67

2.71

2.74

2.77

2.80

2.83

2.86

2.89

2.92

2.95

2.98

3.01

3.04

3.07

3.11

3.14

3.18

3.22

3.26

3.30

3.35

3.40

3.46

3.52

3.58

3.65

3.73

3.82

3.92

4.02

4.14

4.27

4.42

4.58

4.76

4.97

5.20

5.46

5.76

6.09

6.47

6.91

7.40

7.97

8.62

9.37

10.23