English (GB)
29
7.15.3 In the absence of chlorine
7.16 Phosphate, ortho LR,
0.05 - 4 mg/l PO
4
7.16.1 Important notes
1. Ortho-phosphate ions react with the reagent to form an
intense blue colour. Phosphate in organic and condensed
inorganic forms (meta-, pyro- and polyphosphates) must be
converted to ortho-phosphate ions before analysis.
Pretreatment of the sample with acid and heat provides the
conditions for hydrolysis of the condensed inorganic forms.
Organically combined phosphates are converted to
ortho-phosphate ions by heating with acid and persulphate.
The amount of organically combined phosphates can be
calculated:
mg/l phosphate, organic = mg/l phosphate, total - mg/l
phosphate, acid hydrolysable
2. Only ortho-phosphate ions react.
3. The tablets must be added in the correct sequence.
4. The test sample should have a pH-value between 6 and 7.
5. Interferences:
Higher concentrations of Cu, Ni, Cr (III), V (V) and W (VI)
interfere due to their colour.
Silicates do not interfere (masked by citric acid in the tablets).
6. Conversion:
– mg/l P = mg/l PO
4
x 0.33
– mg/l P
2
O
5
= mg/l PO
4
x 0.75
PO
4
P
P
2
O
5
1. Fill a clean vial (
∅
24) with 10 ml of the
water sample, close tightly with the cap.
2. Place the vial in the sample chamber
correctly. See fig.
3. Press the [Zero] key.
4. Remove the vial from the sample
chamber and empty it, leaving a few
drops in the vial.
5. Add one
DPD No. 1
tablet
(No
) and one
DPD No. 3
tablet (No
) straight from the
foil and crush the tablets using a clean
stirring rod.
6. Add water sample to the 10 ml mark.
7. Close the vial tightly with the cap and
swirl gently several times until the tablets
are dissolved.
8. Place the vial in the sample chamber
correctly. See fig.
9. Press the [Test] key. Wait for a reaction
period of 2 minutes.
When the reaction period is finished, the
measurement starts automatically.
The result is shown in the display in mg/l
ozone.
3
0
0
prepare Zero
press ZERO
Zero accepted
prepare Test
press TEST
∅
24
Countdown
2:00
1. Fill a clean vial (
∅
24) with 10 ml of the
water sample. Close tightly with the cap.
2. Place the vial in the sample chamber
correctly. See fig.
.
3. Press the [Zero] key.
4. Remove the vial from the sample
chamber.
5. Add one
Phosphate No. 1 LR
tablet
(No
) straight from the foil to
the 10 ml sample and crush the tablet
using a clean stirring rod.
6. Add one
Phosphate No. 2 LR
tablet
(No
) straight from the foil to
the same water sample and crush the
tablet using a clean stirring rod.
7. Close the vial tightly with the cap and
swirl gently several times until the tablets
are dissolved.
8. Place the vial in the sample chamber
correctly. See fig.
.
9. Press the [Test] key. Wait for a reaction
period of 10 minutes.
When the reaction period is finished, the
measurement starts automatically.
The result is shown in the display in mg/l
ortho phosphate.
3
2
0
prepare Zero
press ZERO
Zero accepted
prepare Test
press TEST
∅
24
Countdown
10:00
Summary of Contents for DIT-M
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