GB/T 5750.11-2006: Standard examination methods for drinking water -- Disinfectants parameters

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1.1 N,N-Diethyl-p-phenylenediamine (DPD) spectrophotometry
1.1.1 Scope
This standard specifies the use of N,N-diethyl-p-phenylenediamine (DPD)
spectrophotometric method to determine free residual chlorine in drinking water
and its source water.
This method is applicable to the determination of free residual chlorine and
combined residual chlorine in various forms in drinking water and its source
water after chlorination and disinfection.
The minimum detection mass of this method is 0.1 µg. If a 10 mL water sample
is taken for the determination, the minimum detection mass concentration is
0.01 mg/L.
High concentrations of monochloramine interfere with the determination of free
residual chlorine, arsenite or thioacetamide can be used to control the reaction
to remove interference. Manganese oxide interference can be eliminated from
making the water sample blank. Chromate interference can be eliminated with
thioacetamide.
1.1.2 Principle
DPD reacts rapidly with free chlorine in water to produce red color. Under the
catalysis of iodide, monochloramine also reacts with DPD to develop color.
When iodide is added prior to the addition of the DPD reagent, a portion of the
trichloramine is developed with the free residual chlorine, and the concentration
of trichloramine can be determined by changing the order of addition of the shift
reagent. This method can use potassium permanganate solution to prepare a
permanent standard series.
1.1.3 Reagents
1.1.3.1 Potassium iodide crystals.
1.1.3.2 Potassium iodide solution (5 g/L). WEIGH 0.50 g of potassium iodide
(Kl), DISSOLVE it in fresh boiled cold purified water, DILUTE it to 100 mL.
permanganate in the standard solution is similar to the DPD and the red color
of the indicated residual chlorine.
1.1.3.9 Chlorine standard use solution [p(Cl2) = 1 μg/mL]. PIPETTE 10.0 mL of
chlorine standard stock solution (1.1.3.8), ADD pure water to dilute it to 100 mL.
MIX it uniformly, TAKE 1.00 mL and DILUTE it to 100 mL.
1.1.4 Instruments
1.1.4.1 Spectrophotometer.
1.1.4.2 Stoppered colorimetric tube, 10 mL.
1.1.5 Analytical procedure
1.1.5.1 Standard curve drawing. PIPETTE 0, 0.1, 0.5, 2.0, 4.0, 8.0 mL of
chlorine standard use solution (1.1.3.9) into six 10 mL stoppered colorimetric
tubes, USE water requiring no chlorine (1.1.3.7) to dilute it to the mark.
Respectively ADD 0.5 mL of phosphate buffer solution (1.3.3.3) and 0.5 mL of
DPD solution (1.1.3.4), MIX it uniformly. DETERMINE the absorbance at a
wavelength of 515 nm in a 1 cm cuvette with pure water as a reference. DRAW
a standard curve.
1.1.5.2 PIPETTE 10 mL of water sample into a 10 mL colorimetric tube, ADD
0.5 mL phosphate buffer solution (1.1.3.3), 0.5 mL of DPD solution (1.1.3.4),
MIX it uniformly; immediately DETERMINE the absorbance at a wavelength of
515 nm in a 1 cm cuvette with pure water as a reference, RECORD the reading
as A, meanwhile MEASURE the sample blank value, DEDUCT it from the
reading.
Note. If the content of monochloramine in the sample is too high, the water
sample can be treated with arsenite or thioacetamide.
1.1.5.3 CONTINUE adding a small crystal of iodinated crystal (about 0.1 mg) to
the above test tube. After mixing it uniformly, MEASURE the absorbance,
RECORD the reading as B.
Note. If the content of dichloramine in the sample is too high, it may add 0.1 mL
of freshly prepared potassium iodide solution (1 g/L).
1.1.5.4 Then ADD potassium iodide crystal (about 0.1 g) to the above tube, MIX
it uniformly. After 2 min, MEASURE the absorbance and RECORD the reading
as C.
1.1.5.5 Take another two 10 mL colorimetric tubes, TAKE 10 mL of water sample
in one of the colorimetric tubes, then ADD a small amount of potassium iodide
crystal (about 0.1 mg), MIX it uniformly; ADD 0.5 mL of buffer solution (1.1.3.3)
and 0.5 mL of DPD solution (1.1.3.4) into the second colorimetric tube, POUR
4.1.1 Scope
This standard specifies the use of N,N-diethyl-p-phenylenediamine (DPD)-
ammonium ferrous sulfate titration method for the determination of chlorine
dioxide in drinking water.
This method applies to the determination of chlorine dioxide in drinking water.
The method requires that the total available chlorine (Cl2) of the water sample
be no higher than 5 mg/L. Once above this value, the sample must be diluted.
The determination scope of this method is 0.025 mg/L ~ 9.5 mg/L, the minimum
detection concentration is 0.025 mg/L (ClO2).
Oxidized manganese and chromate can make DPD produce color, resulting in
high measurement results, it may add sodium arsenite or thioacetamide to the
water sample to correct it; since the entering of titration solution into iron ion
can activate chlorite and interfere with the titration end, it can add
ethylenediaminetetraacetic acid disodium to inhibit it.
4.1.2 Principle
Glycine converts free chlorine in water to glycine chloride without disturbing the
determination of chlorine dioxide. Chlorine dioxide in water reacts with DPD in
red. It is titrated with ammonium ferrous sulfate standard solution. The addition
of phosphate buffer salt will keep the water sample neutral. Under this condition,
chlorine dioxide gets only 1 mol of electrons and is reduced to ClO2-. The
amount of ammonium ferrous sulfate in the water sample can be used to
calculate the mass concentration of the oxygen dioxide.
4.1.3 Reagents
4.1.3.1 Potassium dichromate standard solution [c(1/6K2Cr2O7) = 0.1000 mol/L].
WEIGH 4.904 g of the dried reference potassium dichromate, DISSOLVE it in
distilled water, MAKE its volume reach to 1000 mL, STORE it ground glass
bottles.
4.1.3.2 Bismuth diphenylamine sulfonate solution (1 g/L). WEIGH 0.1 g of
diphenylamine sulfonic acid hydrazine [(C6H5NHC6H4-SO3)2Ba] in 100 mL of
distilled water.
4.1.3.3 Ammonium ferrous sulfate standard solution {c[(NH4)2Fe(SO4)2] =
0.003000 mol/L}. WEIGH 1.176 g of ammonium ferrous sulfate
[Fe(NH4)2(SO4)2•6H2O] into the distilled water containing 1 mL of sulfuric acid
solution (1 + 3), USE the newly boiling and cooled distilled water to dilute it to
1000 mL. USE the potassium dichromate standard solution to calibrate the
concentration in accordance with the following method, this solution can be
c - Concentration of ammonium ferrous sulfate standard solution, in moles
per liter (mol/L);
V2 - The volume of the ammonium ferrous sulfate solution consumed during
the titration of the water sample, in milliliters (mL);
V1 - Volume of ammonium ferric [translator note. should be ferrous] sulfate
standard solution consumed by the oxidized manganese and chromate in
water, in milliliters (mL);
V - Volume of water sample, in milliliters (mL);
13.49 × 5 - The actual mass of chlorine dioxide in milligrams equivalent to
1.00 mL of ammonium ferrous sulfate {c[(NH4)2Fe(SO4)2] = 1.000 mol/L.
4.2 Iodometric method
4.2.1 Scope
This standard specifies the use of iodometric method for the determination of
chlorine dioxide in pure chlorine dioxide aqueous solution.
This method is applicable to the determination of chlorine dioxide in pure
chlorine dioxide solution.
The minimum detection mass of this method is 10 µg (by ClO2). If 500 mL of
aqueous solution is used, the minimum detection mass concentration is 20 μg/L
(by ClO2). Temperature and strong-light can affect the stability of the solution,
so the chlorine dioxide stock solution shall be protected from light, sealed, and
stored refrigerated. In order to minimize the loss of chlorine dioxide, the
preparation and calibration procedures are required to be performed at room
temperature not exceeding 20 °C and in non-direct light.
4.2.2 Principle
Sodium chlorite solution (NaClO2) reacts with dilute sulfuric acid to produce
chlorine dioxide. Impurities such as chlorine are removed ...

Basic Data

Standard ID	GB/T 5750.11-2006 (GB/T5750.11-2006)
Description (Translated English)	Standard examination methods for drinking water -- Disinfectants parameters
Sector / Industry	National Standard (Recommended)
Classification of Chinese Standard	C51
Classification of International Standard	13.060
Word Count Estimation	21,252
Date of Issue	2006-12-29
Date of Implementation	2007-07-01
Older Standard (superseded by this standard)	GB/T 5750-1985
Quoted Standard	GB/T 5750.4-2006; GB/T 5750.10-2006,
Regulation (derived from)	Chinese national standard approved by the announcement in 2006 No. 12 (No. 99 overall)
Issuing agency(ies)	General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China, Standardization Administration of the People's Republic of China