IS 3025-56: Methods of Sampling and Test ( Physical and Chemical ) for Water and Wastewater, Part 56: Selenium

13 Pages·2003·1.3 MB·English

by  Bureau of Indian Standards

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“The Right to Information, The Right to Live” “Step Out From the Old to the New”
IS 3025-56 (2003): Methods of Sampling and Test ( Physical
and Chemical ) for Water and Wastewater, Part 56: Selenium
[CHD 32: Environmental Protection and Waste Management]
“!ान $ एक न’ भारत का +नम-ण”
Satyanarayan Gangaram Pitroda
““IInnvveenntt aa NNeeww IInnddiiaa UUssiinngg KKnnoowwlleeddggee””
“!ान एक ऐसा खजाना > जो कभी च0राया नहB जा सकता हहहहै””ै”
Bhartṛhari—Nītiśatakam
“Knowledge is such a treasure which cannot be stolen”

IS 3025( Part 56 ): 2003
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Indian Standard
METHODS OF SAMPLING AND TEST ( PHYSICAL AND
CHEMICAL ) FOR WATER AND WASTEWATER
PART 56 SELENIUM
Revision )
(First
ICS13.060.50

0 BIS2003
BUREAU OF INDIAN STANDARDS
MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG
NEW DELHI 110002

June 2003 Price Group 3
Environment Protection and WasteManagement Sectional Committee, CHD 32
FOREWORD
This Indian Standard ( Part 56 ) ( First Revision )was adopted bythe Bureau of Indian Standards, after the
draft finalized bythe Environment Protection andWasteManagement Sectional Committee, had been approved
bythe Chemical Division Council.
Pollution caused by substances, on which biotic and abiotic agencies of decomposition are ineffective, isa
unique type of pollution. Toxic trace elements and heavy metals come under the category of non-degradable
pollutants. The problem caused by these elements is infact due to their concentration inthe environment in
the bio-available state and above acertain concentration become harmful to the living organism.
Selenium iswidely distributed at low concentrations inthe earth’s crust. Selenium can bepresent insoil due
tothe bacteria andfungi that arecapable ofreducing selenitesandselenatestoelemental selenium andselenides.
Surfaces, ocean and well water contain lessthan 0.05 mg/1selenium, but spring, irrigation — drainage water
may contain up to 1mg/i selenium. Selenium isanessential trace element and selenium deficiency diseases
are well known inveterinary medicine.
Selenium (Se) isan essential trace element for living beings. Earth’s crust contains 0.05-0.09 mg/g of Se. Sea
water contains about 0.06-0.12 mg/1.ofthis element while soils onanaverage maycontain 0.1-2.0 ppm ofthis
metalloid. About 1-10mg of Se ispresent infossil fuels per kgand itisfrom the combustion ofthese fuels in
urban localities that almost 90 percent ofthis element in ambient air isderived. The Secontent of air on an
average basis ranges between 0.1-10 pg/m3.The availability andtoxicity ofSeto living systems aredependent
upon its chemical form and volubility. In nature and in biological system Se occurs as selenates, selenites,
elemental selenium, andselenide. Whileselenatesarerather soluble compounds selenitesandelemental selenium
are virtually insoluble. Selenium compounds maybebio-transformed inthe body byincorporation intoamino-
acids, proteins or by methylation. Biologic role of Se has been attributed to its incorporation in Se-cystein
which goes intothe organization ofglutathione peroxidase. The enzyme reduces organic peroxides and protects
membrane lipids and probably proteins also from oxidant damages.
Industrial exposures to hydrogen selenide produce garlic like breath, dizziness and lassitude. Eyes and nasal
irritation may also occur. Inexperimental animals 10ppm isfatal. Inrabbies 0.01 mlofselenium oxy-chloride,
applied dermaily results death. S e lenium oxy-chloride isavasicant. Itcauses blister formation and destruction
of tissues of skin exposed to it. A c ute selenium poisoning affects central nervous system which includes
nervousness, drowsiness and attimes convulsions. Symptoms ofchronic inhalation exposures include pallor,
coated tongue, gastro-intestinal troubles, nervousness, liver and spleen damage, mucosal irritation and lumber
pain.Consumption of 100-1000 ppmofSewithdietcauses‘blindstagger’inmammals.Itisusuallyinseleniferous
areas only that evidence of chronic Se poisoning isobserved. Discolored or decaying teeth, skin eruptions,
gastro-intestinal disorders, lassitude, partial loss of hairs and nails, impairment of vision, weakness in limbs
and respiratory failures arethe common symptoms. Sehasalso been considered embryo-toxic andterratogenic
element. However, an increased Secontent hasbeen correlated with adecreased cancer death rates inhumans
and apparently it exerts aprotective action against some types of cancer. Inaddition, Se isan antidote to the
toxic effects of some metals like, As, Hg, and Cd.
Asper IS 10500:1991 ‘Drinking water—Specification (first revision )’, thepermissible limits for selenium in
the drinking water is0.01 mg/1,Mac. Beyond this level the water becomes toxic.
However, inviewoftheenvironmentally prevalent natureofSecompounds itslevelsshouldbeclosely monitored
to avoid any likelihood of toxicity caused bythis element.
in the preparation of this standard, considerable assistance isderived from 1S0 9965:1993 ‘Water quality
determination of selenium – Atomic absorption spectrometric method ( hydride technique )’ and Standard
Methods forthe Examination ofWaterandWasteWater, 19thEdition -1995, published bythe American Public
Health Association. Washington, U.S.A. Atomic absorption spectrometric method inthisstandard istechnically
equivalent to the method specified in1S0 9965.

( Continued on third cover)
IS3025( Part 56) :2003
Indian Standard
METHODS OF SAMPLING AND TEST ( PHYSICAL AND
CHEMICAL ) FOR WATER AND WASTEWATER
PART 56 SELENIUM
( First Revision )
1 SCOPE ofsampling, isrequired. The analysis ofsuch samples
is to be carried out within 24 h of sampling. For
This standard ( Part 56 ) prescribes two methods for
preservation, the samples should be acidified with
the determination of selenium:
concentrated nitric acid ( 2 ml of cone nitric acid
in 1Iitresample,just tobring down thepH below 2).
a) Spectrophotometric method ( Diaminona-
The acidified samples can be stored for a few days
phthalene method ), and
(up to 5days) inarefrigerator.
b) Atomic absorption spectrometric method
5 PURITY OF THE REAGENTS
(Hydride technique).
Unless specified otherwise, only pure chemicals and
2 REFERENCES
selenium free distilled water shall be used in tests.
The standards listed below contain provisions which
NOTE—‘Purechemicals’shallmeanchemicalsthat
through reference in this text, constitute provisions
do notcontainimpuritieswhichaffect the result of
ofthisstandard. Atthetimeofpublication, theeditions analysis.
indicated were valid. All standards are subject to
6 SPECTROPHOTOMETRIC METHOD
revision and parties to agreements based on this
(DIAMINONAPHTHALENE METHOD )
standard are encouraged to investigate the possibility
ofapplying the most recent editions ofthe standards.
6.1 Principle
[S No. Title This method is specific to determine selenite
[ SeO~2-, Se (IV) ] in aqueous solution. Se (IV)
3025 Methods of sampling and test
reacts with 2,3-diaminonaphthalene to produce a
(Part 1): 1986 (physical and chemical) for water
brightly coloured andstrongly fluorescent piazselenol
and waste water :Part 1 Sampling
compound, which is extracted in cyclohexane and
(first revision ) measured spectrophotometrically at 480 nm. The

7022 Glossary ofterms relating towater, optimumpH forformation ofthepiazselenol complex
(Part l): 1973 sewage and industrial effluents, is approximately 1.5 but should not be above 2.5,
Part 1 because, the rate of formation of the coloured
compound iscritically dependent onpH abovepH 2.
7022 Glossary ofterms relating towater, Minimum detectable quantity bythis method is 10pg
(Part 2): 1979 sewage and industrial effluents, Se/l. This method isapplicable inthe range of 25to
Part 2 2 000 ~g/1 of selenium. Dissolved Se consists
predominantly of selenite designated as Se(IV) and
3 TERMINOLOGY
selenatedesignatedasSe(VI).Whentotal Seisdesired,
For the purpose of this standard, definitions given Se (VI) is reduced to Se (IV) by digestion with
inIS7022 (Part 1)and IS7022 (Part 2)shall apply. concentrated HCI and the total Se isestimated.
4 SAMPLING AND STORAGE 6.2 Interference
The sampling and storage shall bedone asprescribed No inorganic compound isknown to give apositive
in IS 3025 ( Part 1). The sampling bottles shall be interference. Colouredorganiccompounds extractable
cleaned thoroughly’with dilute nitric acid (6N),prior bycyclohexane maybeencountered, but usually they
tothefinalrinsingwithwater. Thewatersamplesshould areabsentorremoved bysuitabletreatment. Negative
be collected and stored preferably inpolypropylene interference results from compounds that reduce the
bottles or chemically resistant glass containers. For concentration ofdiaminonaphthalene byoxidizing it.
the determination of dissolved selenium content, Addition of EDTA eliminates negative interference
‘filtration through 0.45 ~m membrane filter,atthetime from upto2.5 mgFe2+.

1
IS3025( Part 56 ): 2003
6.3 Apparatus 6.4.11 Potassium Hydroxide
6.3.1 Spectrophotometer — for use at 480 nm, 6.5 Procedure
providing a light path of 1cm.
6.5.1 Preparation of Calibration Curve
6.3.2 Standard Volumetric Glassware 6.5.1.1 Pipette out suitable volumes of standard
selenium solution ranging from Oto 10ml (Oml for
6.3.3 Separato~ Funnel — 250 ml, preferably with the reagent blank )in50mlbeakers.
a fluorocarbon stopcock.
6.5.1.2 Formation ofpiazselenol complex
6.3.4 Thermostatically Controlled Water Bath with
Add2mlHA-EDTA solution toeachofthesebeakers.
Cover
Add about 10mlofwater, and adjustpH to 1.5+0.3
6.3.5 pH Meter usingO.INHCIand 1:1 NHdOHandapH meter, Add
5mlofDANsolution. Cover the beaker with awatch
6.3.6 Centrifuge — with rotor, for 50 ml tubes glass and place inthe water bath maintained at 50°C
(optional). for30min.
6.3.7 Centr@ge Bottles — with fluorocarbon screw 6.5.1.3 Extraction ofpiazselenol complex
cap.
Cool thesolutioninthebeaker. Transfer quantitatively
the contents into a 150 ml separator funnel. Add
6.4 Reagents
3.0mlofcyclohexane. Shakevigorouslyfor5minutes.
6.4.1 Stock Selenium Solution — Dissolve 2.190 g Waitfor2minoruntilcyclohexane layerbecomes well
of sodium selenite inwater containing OmlofHCI separated. ( Ifthe cyclohexane layer isnot properly
and dilute to 1000 ml inavolumetric flask [1.0ml= separated, transfer the organic phase to a 50 ml
1.0mgof Se(IV) ]. centrifuge tube/bottle. Centrifuge for 5 min at
2000 rpmforproper separation.) Transfer theorganic
6.4.2 Standard Selenium Solution — Dilute 10mlof phasetoa5-mlvolumetric flask. Usethisdirectly for
the stock selenium solution to 1000 mlwithwater in absorption measurement. Measure the absorbance
a volumetric flask [ 1.0ml= 10~gofSe(IV) ]. at480 nmusing cyclohexane asreference.
6.4.3 Hydrochloric Acid, concentrated and 0.1N. 6.5.2 Determination of Selenium (IV)
6.5.2.1 Formation of piazselenol complex and
6.4.4 Ammonium Hydroxide, 1:1.
extraction ofpiazselenol complex
6.4.5 Cyclohexane
Pipetteout 10mloranappropriateamountofthesample
containing 10-100ygofselenium intoa50-ml beaker
6.4.6 2,3-Diaminonaphthalene (DAN) Solution —
( sample filtered through 0.45 ~ membrane filter,
Dissolve200mgofDANin200mlofO.INHCI. Shake
if no coloured organic compounds extractable by
for 5min. Extract three times with 25 mlportions of
cyclohexane are present, or the sample is treated
cyclohexane, each time retain the aqueous phase and
with ion exchange resin for the removal of
discardtheorganicphase. Filterintoanambercoloured
organic compounds, as described in 6.5.2.2 ). Add
bottle and store incool, dark place. This reagent is
2-mlof HA-EDTAsolution and about 10mlofwater,
to be used within 8h.
if required, and carry out the paizselenol complex
CAUTION —DAN istoxic.Sohandlewithextreme formation and extraction process as described
care. earlier(6.5.1.2 and6.5.1.3 ). Measure theabsorbance
of the cyclohexane layer at 480 nm. From the
6.4.’7 Hydroxylamine + EDTA Solution ( HA- absorbancedatadeterminethemicrograms ofselenium
EDTA ) — Dissolve 4.5 g NazEDTA in approxi- present in 100 ml of the final solution using the
mately 450 ml water. Add 12.5gof hydroxylamine calibration curve.
hydrochloride (NHZOH-HCI )andadjust thevolume
to500ml. 6.5.2.2 Removal of organic matter
Thoroughly wash the resin ( Amberlite XAD-8 or
6.4.8 Amberlite XAD-8 or Equivalent Resin
equivalent ) with deionized water, remove the fine
6.4.9 pH 1.6Solution — Adjust thepH ofdeionized resin particles by decanting. Washthree times with
water to 1.6with concentration HC1 pH 12solution. Place 5 cm of the washed resin in a
0.8 cm ID glass column. Precondition the column
6.4.10 pH 12Solution — Adjust thepH ofdeionized (at arate of 1ml/min )with 30ml ofpH 12solution,
water to 12 with KOH. and20mlof pH 1.6solution. UsingHCIandpH meter
2
IS 3025( Part 56): 2003
adjustsamplepH to 1.6to 1.8. Pass50mlofthesample Assumingthesamplescontaining250mgofdriedsolids
through the preconditioned column at a rate of are ashed, extracted and diluted to the equivalent of
1ml/min. Discard the first few mlofthe eluent and 500ml,then 100mg and250mgoftheothersubstance
collectalltheremaining eluent. Use it fortheselenium usedwouldcorrespond tothesolidsamples containing
determination as described in6.5.2 and 6.5.2.1. 40 percent and 100 percent of the other substance,
respective; and 3.75 pg of Se would correspond to
6.5.2.3 Determination of total Se[ both (IV) and
the solid samples containing 15mg/kg of Se.
(VI) ] as Se (IV)
7.3 Apparatus
Pipetteout10mloranappropriate amountofthesample
containing10-100~gofselenium intoa 150-mlbeaker. 7.3.1 Atomic Absorption Spectrometer — Fitted
Measureequal amount ofwater inanother beaker for with a hydride system and a suitable radiation
preparing a reagent blank. Add 10ml concentrated source for the determination of selenium, for
HCItoboththesolutions coverthebeakerswith watch example, electrodeless discharge lamp or a hollow
glasses. Placethese beakers inawaterbathmaintained cathode lamp. Abackground correction facility may
at95°Cfor60min.Coolthesolutiontoroomtemperature beappropriate.
and use for selenium determination as described
Table 1 Effect ofOther Substances on the
in6.5.2 and 6.5.2.1 using similarly prepared reagent
Determination of Selenium
blank. [ If the sample contains coloured organic
compounds extractable bycyclohexane, thenthesame (Clause 7.2)
istreated withionexchangeresinforthecolourremoval
(sce 6.5.2.2 )prior to the reduction step]. Other Substances Mass of Effect, in pg Se
Other of the Other
6.6 Calculation Substance Substance on
3.75 pg Se
pgof Se
(1) (2) (3)
mgSe/l =
v Sodiumaschloride 250 0.0
Potassium as chloride 250 -0.1
where
Calcium aschloride 250 0.0
V = volume, inml, ofthe sample used.
Magnesium aschloride 250 0.2
7 ATOMIC ABSORPTION SPECTROMETRIC Aluminium assulphate 250 0.2
METHOD (HYDRIDE TECHNIQUE) Lanthanum as chloride 250 -0.3
Borate as sodium salt 250 -0.1
7.1 Principle
Carbonate as sodium salt 250 -0.2
The method is based on the atomic absorption
Nitrate as sodium salt 250 – 0.5
spectrometric measurement ofsel enium generated by
Ammonium salt ashydroxide 250 0.0
thethermal decomposition ofselenium hydride. Under
Phosphate as potassium salt 250 0.2
the conditions of this method, only Se (IV) is
quantitatively converted to the hydride. To avoid Sulfate assodium salt 250 0.0
errors in determination, other oxidation states need Fluoride assodium salt 250 -0.7
to beconverted to Se (IV) prior tothe determination. Bromide as sodium salt 100 0.2
Se (IV)isreducedtogaseousseleniumdibydride(SeHJ Iodide as sodium salt 100 0.1
by reaction with sodium tetrahydroborate in a
Chromium (111)as chloride 100 -0.2
hydrochloric acidmedium. Theabsorbanceismeasured
Manganese (11)as sulphate 100 0.3
atawavelength of 196.0 nm.
Iron (111)as chloride 250 0.5
7.2 Interferences
Cobalt (II) as chloride 100 -1.7
Table 1givesdetails ofpotential interfering substances Nickel as sulphate I00 -3.4
which have been present during part of the analytical Copper (II) as chloride 250 -1.8
procedure. The solutions forinterference testing were Zinc as oxide 250 0.2
prepared from either solid reagents or concentrated
Cadmium aschloride 100 0.3
solutions of the reagents, in such a way that 500 ml
Mercury (II) as chloride 100 -2.9
of the solution contains the stated mass of the other
Tin (11)as chloride 100 -0.4
substance and the stated mass of selenium. The
Lead (H) as acetate 100 0.5
solutions were then run through the measurement
stage of the method and the results expressed asthe Antimony as sodium tartrate 250 – 3.7
effect on the stated mass of selenium. Bismuth as nitrate 100 -3.0

3
IS 3025( Part 56) :2003
..
7.3.2 Gas Supply — with argon or nitrogen. For example, for the range 1pg/1,pipette 1ml, 3ml,
5ml, 8mland 10mlofselenium standard solution 2
7.3.3 Glassware — to becleaned immediately before
(see 7.4.8)intoaseriesof100ml one-markvolumetric
use with warm, diluted nitric acid ( for example,
flasks. Toeachoftheseflasks,add2mlofhydrochloric
2ml/1) and rinsed with water,
acid anddilute tovolume withwater. These solutions
correspond to selenium concentrations of 1 pg/1,
7.4 Reagents
3 pg/1,5 ~g/1,8 ~g/1and 10 pg/1respectively. The
7.4.1 Sulphuric Acid—p = 1.84 glml. calibration solutions shall be prepared daily.
7.4.2 Hydrochloric Acid-–p = 1.16glml. 7.5.3 Treatment
7.4.3 Hydrogen Peroxide — w ( HZ02)= 30percent For the determination ofthe total selenium content,
(m/m). the samples shall bedigested inorder to decompose
organicseleniumcompounds. Ifexperience hasshown
7.4.4 Sodium Hydroxide
thattheseleniumwillberecoveredquantitativelywithout
7.4.5 Sodium Tetrahydroborate Solution decomposition, the digestion process (7.5.3.1) may
beomitted.
Dissolve 1 g of sodium hydroxide in about 20 ml
of water. Add 3 g of sodium tetrahydroborate 7.5.3.1 Method of digestion
(NaBHd). Dilute to 100mlwith water. The solution
shall be prepared daily. Add 5ml of sulphuric acid (see 7.4.1 ) and 5ml of
hydrogen peroxide (see 7.4.3) totheround-bottomed
7.4.6 Selenium, Stock Solution flask ( see 7.3.3 ). Add some boiling beads and
connect the flask to anapparatus asshown inFig. 1.
Place 1.4053 gof selenium dioxide in avolumetric
Close the cock. Heat the contents of the flask to
flaskofnominal capacity 1000 ml. Add2gofsodium
boiling andcollect the condensate inthe condensate
hydroxide and dissolve inasmall quantity of water.
reservoir. Continue heating until turbid fumes of
Dilute to volume with water ( 1ml~ 1mg ofSe).
sulphuric acid appear. Check the appearance of the
NOTE — Selenium stock solutions are commercially sample. [fit isturbid andalmost colorless, cool and
available. add another 5mlofhydrogen peroxide and continue
boiling asdescribed above. After cooling, return the
7.4.7 Selenium, Standard Solution 1
condensate to the round bottomed flask.
Pipette10mlofseleniumstock solutionintoagraduated
NOTE —Care should betaken toensure that the sample
flask of nominal capacity 1 000 ml, Add 20 ml
is never evaporated to complete dryness.
hydrochloric acid and dilute to volume with water
( 1mls O.01mgofSe ). 7.5.3.2 Reductionfrom Se (VI) to Se (IV)

NOTE — This solution is stable for at least I week. Add 20mlofhydrochloric acidtotheround bottomed

flask. Gently boilthe mixture under reflux for 15min
7.4.8 Selenium, Standard Solution 2
with the cock open. If there is no prior digestion
Pipette 10ml of selenium standard solution 1into a and if the sample contains free chlorine, aerate the
graduated flask of nominal capacity 1000 ml. Add solution with nitrogen (about 1l/rein) for the same
20 mlofhydrochloric acid and dilute to volume with period oftime. Coolthe samples solution andtransfer
water ( 1ml= 0.0001 mgofSe). it quantitatively into a graduated flask of nominal
capacity 100ml. Dilute to volume with water. Treat
NOTE — This solution is stable for at least 1week.
the blank solution ( see 7.5.1 ) and the calibration
7.5 Procedure solutions ( see 7.5.2 ) inthe same way.
7.5.1 Blank Solution 7.5.4 Calibration and Determination
Pipette 2 ml of hydrochloric acid into a graduated Depending onthe hydride system used, volumes that
flask of nominal capacity 100 ml, and dilute to aregreater orsmallerthanthose described inthis sub-
volume with water. Treat the blank in exactly the clause may be used. However, the quantity ratios
same way as the sample. defined shall be maintained. Set all the instrumental
parameters ofthe atomic absorption spectrometer in
7.5.2 Calibration Solutions
accordance withthemanufacturer’s operating manual
Using selenium standard solution 2 ( see 7.4.8 ), (wavelength; 196.0 nm) and optimize the position
prepare at least five calibration solutions covering of the absorption cell inorder to obtain amaximum
the expected working range. transmission.

4
IS 3025( Part 56): 2003
Fk
I
REFLUX CONDENSER
I
RISER
I
Ill~I
“wliii!E’:-
r
w DECOMPOSITION FLASK
OF NOMINAL CAPACITY
1
WV!.’,. 2--5-0- m..l
w’
—
—————,——_—_
-—__—_
——I —
—$
—_
--
FIG. 1 EXAMPLEOFDECOMPOSITIONAPPARATUS
Measure the solutions inthe following order: Add about 5mlofsodium tetrahydroborate solution
a) blank solution; ( see 7.4.5 ) to the solution and record the signal.
Establish the calibration curve using values obtained
b) calibration solutions; and
with the blank and calibration solutions. Repeat the
c) samples. procedure using separate portions of each solution.
Pass a stream of argon or nitrogen through the
NOTE — [t is good practice to check the blank and
systemandzerotheinstrument. introduce,forexample,
calibration points from time to time, With unknown
20 ml of the reduced solution ( see 7.5.3 ) into the
samples, it isgood practice to check the validity ofthe
reaction vessel. Connect the reaction vessel to the method by adding aknown volume of selenium, in one
hydride system. Pass argon or nitrogen through the sample at least. If recovery tests are not satisfactory,
solution until the absorption signal returns to zero. the procedure of standard additions should be used.
5