Showing posts with label Environment. Show all posts
Showing posts with label Environment. Show all posts
Thursday 14 March 2019
SOP for ESTIMATION OF HEXAVALENT CHROMIUM
PRINCIPLE:
The
hexavalent chromium is determined calorimetrically by reaction with diphenylcarbazide in
acid
solution. A red-violet colored complex of unknown composition is produced. The
reaction
is very sensitive, the molar absorptivity based on chromium being about 40000 Lg –1 cm-1
at 540 nm.
MINIMUM
DETECTION LIMIT: 0.05
mg/l
REAGENTS:
1.
Stock chromium solution: Dissolve 141.4 mg K2Cr2O7
water and dilute to 100 ml;
1.00 ml = 500 µg Cr.
2.
Standard chromium solution: Dissolve 1.00 ml stock chromium
solution to 100 ml;
1.00 ml = 500 µg Cr.
3.
Phosphoric acid, H3PO4, conc.
4.
Diphenylcarbazide solution: Dissolve 250 mg 1,5-
diphenylcarbazide
(1,5-diphenylcarbazide) in 50 ml acetone. Store in a brown
bottle. Discard when solution
becomes discolored. Chromium solution (5 mg/L) ranging from 2.00
to 20.0 ml, to give
standards for 10 to 100 µg Cr, into 250-ml beakers or
conical flasks. Proceed with
subsequent treatment
PROCEDURE:
Preparation
of calibration curve:
To
compensate for possible slight losses of
chromium during digestion or other
analytical operations, treat standards by the
same procedure as the sample.
Accordingly, pipette measured volumes of standard
of standards as if they were
samples, also carrying out cupferron treatment of standards
if this is required
for samples. Develop color as for samples, transfer a suitable portion of
each
colored solution to a 1-cm absorption cell, and measure absorbance at 540 nm,
using reagent water as reference. Correct absorbance readings of standards by
subtracting absorbance of a reagent blank carried through the method.
Color
development and measurement: Add 0.25 ml (5 drops) H3PO4. Use
0.2 N
H2SO4 and a pH meter to adjust solution to pH 1.0 ±
0.3 the matter of pH range is
currently being considered by standard methods.
Transfer solution to a 100-ml volumetric
flask, dilute to 100 ml, and mix. Add
2.0 ml diphenylcarbazide solution, mix, and let stand
5 to 10 min for full
color development. Transfer an appropriate portion to a 1-cm
absorption cell
and measure its absorbance at 540 nm, using reagent water as reference.
Correct
absorbance reading of sample by subtracting absorbance of a blank through
the
method. From the corrected absorbance, determine micrograms chromium
present by
reference to the calibration curve.
CALCULATION
HEXAVALENT
CHROMIUM (mg/l) = ABS /
SLOPE
REFERENCE: APHA – 3500 Cr - B Colorimetric Method
SOP for ESTIMATION OF SOLIDS
PRINCIPLE:
TOTAL SOLIDS (TS) – The
sample is evaporated in a weighed dish on a steam
bath and is dried to a
constant mass in an oven either at 103 – 105°C or
179 to 181°C. Total residue
is calculated from increase in mass.
TOTAL DISSOLVED SOLIDS
(TDS) – the sample is filtered and the filtrate
evaporated
in tared dish on steam bath. The residue after evaporation is dried
to constant
mass at 103 – 105°C.
MINIMUM
DETECTION LIMIT(TDS): 5.0 mg/l
REQUIRMENT:
Filtration apparatus: Any
one of the following can be used.
1. Membrane filter funnel
2. Gooch crucible, 25 ml to 40
ml capacity with Gooch crucible adapter.
3. Filtration apparatus with
reservoir and coarse (40 – 60 mm) fritted disk as filter
support.
4. Suction flask of sufficient
capacity for sample size selected.
5. Drying oven for operation
at 180 ± 2 °C.
PROCEDURE:
PREPARATION:
Clean &
thoroughly wash all the glassware’s with dilute Sulphuric acid.
Rinse the
glassware’s several times with distilled water. Dry the glassware’s in oven
at
180oC for 1 hour. Keep them in desiccators for cooling. Weigh the
cooled
evaporating dishes (two nos.) initially. Note down the reading A (dish
for TS) &
B (dish for TDS).
Sample testing:
Select volume of the sample, which has residue, contains
approximately 100 to
200 mg. This value may be calculated from values of
specific conductance. To
obtain measurable residue if necessary, add successive
sample portions to the
same dish after evaporation.
Pipette this
sample to previously weighed evaporating dish A (for TS). Filter the sample
(20
ml /25 ml) using 0.45 m m membrane filter. Collect
the filtrate in a clean beaker.
Measure 10 ml or suitable aliquot of filtrate
& transfer it to second evaporating
dish B. Evaporate the water content
completely using water bath / oven. If oven is used
adjust the temp 103 – 105 oC. Cool the
dishes in desiccators.
Weigh the
cooled dishes. Again heat the samples at temperature 105oC for one
hour
and check the weight loss. If there is considerable difference in first
observation and
second one then repeat the heating till weight of dried sample
remains constant
in two consecutive observations & note down the reading
(C-for without filtration &
D-for filtrate).
OBSERVATIONS:
1. Initial weight of evaporating
dish for sample without filtration -------(A)
= g
2. Initial weight of evaporating
dish for sample with filtration---------(B)
= g
3. Final weight of evaporating
dish for sample without filtration -------
(C) =
g
4. Final weight of evaporating
dish for sample with filtration ----------
(D) = g
CALCULATIONS:
Total Solids (TS)
C - A
mg/L = ----------------------------- x 1000 x 1000
ml of sample taken
Total Dissolved Solids
(TDS)
D - B
TDS = --------------------------------- x
1000 x
1000
ml of sample taken
Total Suspended Solids (TSS) mg / l = TS mg / l – TDS mg / l
REFERANCE: IS : 3025 (Part 15 & 16) – 1984
DRY
RESIDUE, DVS AND TVS
PROCEDURE:
After noting down the final
weights of TS and TDS, keep the samples in muffled
furnace at temperature 550oC
for one hour.
Note down the final weights
of the evaporating dishes.
OBSERVATION:
Final weight of TS
evaporating dish (E) = g
Final weight of TDS
evaporating dish (F) =
g
CALCULATIONS:
1. TVS
(C - A) - E
TVS mg/L =
----------------------------------- x
1000 x 1000
ml of
sample taken
2. DVS
(D - B) - F
DVS mg/L =
------------------------------------- x 1000 x 1000
ml of
sample taken
REFERENCE: APHA –2540 Std. Methods for water and
wastewater analysis
SOP for ESTIMATION OF PHOSPHORUS BY STANNOUS CHLORIDE METHOD
PRINCIPLE:
Molybdophosphoric
Acid is formed and reduced by stannous chloride to intensely
coloured
molybdenum blue.
MINIMUM
DETECTION LIMIT: 3
µg P/l
REAGENTS:
1. Phenolphthalein indicator
aqueous solution.
2. Strong acid solution: Slowly add 300 ml conc. H2SO4
to about 600 ml distilled
water. When cool, add 4.0 ml conc. HNO3 and
dilute to 1000 ml.
3. Ammonium molybdate reagent: Dissolve 25 g ammonium
molybdate in 175 ml
distilled water. Cautiously add 280 ml conc. H2SO4
to 400 ml distilled water.
Cool, add molybdate solution and dilute to 1000
ml.
4. Stannous chloride reagent: Dissolve 2.5 g fresh SnCl2.
2H2O in 100 ml glycerol.
Heat in a water bath and stir with a glass
rod to hasten dissolution. This reagent is
stable and requires neither
preservatives nor special storage.
5. Standard phosphate
solution:
Dissolve 219.5 mg anhydrous KH2PO4 and
dilute with distilled water to 1000
ml. (1ml.= 50 mg PO4)
PROCEDURE:
1. Sample pretreatment: To 100 ml sample
containing not more than 200 mg P and
free from colour
and turbidity. Add 0.05 ml (1 drop) phenolphthalein indicator.
If sample turns
pink add strong acid solution drop wise to discharge the colour.
If more than
0.25 ml (5 drops) is required, take a smaller sample and dilute to
100 ml with
distilled water after first discharging the pink colour with acid.
2. Colour development: Add with through mixing
after each addition,
4.0 ml molybdate reagent and 0.5 ml stannous chloride.
Rate of colour removal
development and intensity of colour depend on temperature
of the final solution.
Each 1o C increases producing about 1 %
increase in colour. Hence hold samples,
standards and reagents within 2 o
C of one another and in the
temperature range between 20 oC and 30 oC.
3. Colour measurement: After 10 min., but before
12 min. using
it specified interval for all determinations.
Measure colour photo
metrically at 690 nm and compare with calibration curve.
CALCULATION:
A B
mg/L of P =
------------------- x -----------
ml of sample C
Where,
A = mg P determined from plotted curve,
B = final volume of diluted sample (ml)
C = Volume of diluted sample used for colour development
(ml)
REFERENCE: APHA – 4500 P D.
Stannous chloride method
SOP for ESTIMATION OF NITRITE NITROGEN
PRINCIPLE:
Nitrite
Nitrogen is determined through formation of a reddish
purple azo-dye produced at pH 2 – 2.5 by coupling diazotized sulphanalic acid
with NED dihydrochloride.
MINIMUM DETECTION LIMIT: 0.01
mg/l
REAGENTS:
1. Sulphanilamide reagent:
Dissolve 5gm of the material in a mixture of 50ml of conc. hydrochloric acid
& 300ml of water. Dilute to 500ml with water. The reagent is stable for
several months.
2. Sodium oxalate (0.05N): Dissolve 3.35 g Sodium
oxalate, primary standard grade in water and dilute to 1000ml.
3. Ferrous Ammonium Sulphate
(0.05N):
19.607 g FAS plus 20 ml Conc. Sulfuric acid dilute to 1000 ml
4. Stock nitrite solution: Dissolve 1.232 g Sodium
nitrite in 1000 ml (250 ppm). Preserve it with 1 ml of chloroform.
5.
Standardization of stock nitrite solution:
Pipette out 50 ml standard (0.05M) KmnO4, 5 ml Conc. Sulfuric acid
and 50 ml stock nitrite solution into a glass stopper flask or bottle. Submerge
pipette tip well below permanganate acid solution while adding stock nitrite
solution. Shake gently. Discharge permanganate colour by adding sufficient 10
ml portion of standard 0.05M FAS. Wait for 5 min.
Titrate excess
FAS with 0.05 M KmnO4 to the faint pink end point. Carry a water
blank through the entire procedure and make the necessary corrections in the
final calculation as shown in the equation below.
Calculate
nitrite content of stock solution
[ (B x C) – (D x E)] x 7
A =
----------------------------------------
F
Where,
A = mg nitrite nitrogen /L in stock solution
B = Total ml of standard KMnO4
used
C = Normality of standard KMnO4
E = Normality of standard reductant,
F = ml stock sodium nitrite solution taken
for titration.
Each one ml
potassium permanganate consume by sodium nitrite solution corresponds to 1750 g
nitrite nitrogen.
6.
Intermediate nitrite
solution: Calculate the volume G of stock nitrite
solution required for the intermediate nitrite solution from G = 12.5/A. Dilute
the volume G (approximately 50 ml) to 250 ml with water. (50 ppm). Prepared
daily
7. Standard nitrite solution: Dilute 10 ml intermediate
nitrite solution to 1000 ml with water (0.5 ppm)
PROCEDURE:
Removal of suspended
solids: If
sample contains suspended solids remove it by passing sample through 0.45 mm membrane filter.
Colour development: If sample pH is not
between 5 – 9, adjust to that range with 1 N HCl
or NH4OH as required. To 50 ml sample or to a portion diluted to 50
ml add 2 ml colour reagent and mix.
Photometric measurement: Bet. 10 min and 2 hr.
after adding colour reagent to samples and standards, measure absorbance at 543
nm.
CALCULATION:
Prepare a standard curve by
plotting absorbance of standards against nitrite nitrogen concentration.
Compute the sample concentration directly from curve.
Nitrite
Nitrogen (as NO2-N) /l = µg NO2-N (in 52 ml of Final volume)
ml of Sample
REFERENCE: IS : 3025 ( Part 34 ) – 1988
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