Chapter - Ill
FLOW INJECTION ANALYSIS
DETERMINATION OF CATIONIC
SURFACTANTS WITH IRON(lll) AND
THIOCYANATE
86
Chapter- III
FLOW INJECTION ANALYSIS DETERMINATION
OF CATIONIC SURFACTANTS WITH IRON(III)
AND THIOCYANATE
Cationic surfactants are widely used in the detergents, soaps, shampoo, lotions, etc. and
theu pollutiOn load specially in the surface water is increasing. The spectrophotometric
method based on the extraction of the cationic surfactants (CS) with anionic dyes i.e.
orange ll into organic solvent i.e. chloroform is widely used for their determination but the
selectivity, sensitivity and sample analysis rate are very poor. In this work, a new, simple,
rapid and scleclive tlow inJectiOn analysis (F!A) procedure for the spectrophotometric
determination of cationic surfactants (CS) i.e. dodecyltrimethylammonium bromide
(DTAI3 ),
tetradecyltrimethylammonium
bromide (TTAI3 ),
cetyltnmethylammonium
bromide (CTAB), cetylpyridinium chloride (CPC) with iron(lll) and thiocyanate ions has
been developed.
The
value of apparent molar absorptivity of the Fe(IIl)-SCN·-cs'
1
complex with various surfactants lie in the range of(2.10- 4.30) x 103 I mole' 1 cm· in the
term of the cationic surfactants at absorption maximum, 475 nm. The most sensitive
surtactant, cetylpyridinium chloride (CPC) has been selected for the detailed studies. The
detection limit (amount causing more peak height than 3s), and sample throughput of the
method are 280 ppb CPC, and 100 samples h· 1, respectively. The eftect of analytical and
FIA variables on the determination of the surfactant are described. The composition of the
complex involved in the determination of the surfactant is discussed. The method is free
from interferences of almost all ions which commonly associated with the surfactant m the
envtronmental samples. The simplicity, sensitivity and rapidity of the proposed method are
better than the orange-1! F!A method. The proposed method has been applied for the
reproductble analysts of the surfactants in vanous environmental samples 1.e. surface.
ground and mumc1pal waste waters and commodity samples.
87
INTRODUCTION.
Catwmc surfactants (CS) arc widely used in the manufacture of numerous consumer
products
1.e.
detergents, soaps, shampoo, fabric softeners, motor oils, pharmaceuticals,
paints, disinfectants, and various cosmetic products due to detersive properties, but they
have also been reported as pollutants [I-ll]. Cationic surfactants comprise less than I 0%
of the total surfactants but they are the most rapidly growing segment of the surfactant
market due to increasing use of the products containing cationic surfactants [12-13]. The
concentration of the surfactants in water bodies z.e. ground water aquifers, surface and
municipal waste water reservoirs of the highly populated Asian countries like India is
tremendously increasing due to high anthropogenic stress generated by change in lilc style
m the fashwn similar to western countries. Many spectrophotometric methods based on
ion-pair extraction of the ion-pair species formed between the cationic surfactants i.e.
dodecyltrimethylammonium bromide (OT AB ), tetradecyltrimethylammonium bromide
(TTAB), cetyltrimethylammonium bromide (CTAB), cetylpyridinium chloride (CPC) and
the aniomc dyes are the common procedures to quantify these surfactants in the complex
materials [14-36). The flow injection analysis (FIA) methods based on the reaction of the
cationic surfactants (CS) with anionic dyes
1.e.
bromophenol blue (BPB), bromocresol
green (BCG), orange II, tetrabromophenolphthalein ethyl ester (TBPE), etc. were reported
for the determination of the cationic surfactants [37-52]. They require prior separation by
solvent extraction with solvents i.e. chloroform, I ,2-dichloroethane to enhance the
selectivity [37-52). Kawase et al. used orange II as ion-pair reagent for the flow injection
analysis (FJA) determination of cationic surfactants, but sensitivity of the method is very
poor with low sample throughput and precision [43-44). Sakai et al. reported tetrabromophenolphthalein ethyl ester (TBPE), bromophenol blue (BPB) I bromochlorophenol blue
(BCPB)-Quimdine (Qd) as reagent for the FIA determination of the cationic surfactants
145-52].
However, they require prior separation by solvent-extraction tcchmquc to
enhance selectivity with poor sample throughput.
In the present work, a new, s1mplc and
88
speciiic llow mjection analysis (FIA) method l(lr the spectrophotometric determination of
cattontc surlactant (CS) in terms of cetyl pyndinium chlondc (CI'C) based on the
enhancement ofeolour intensity of the Fe(lii)-SCN" complex in the nitric acid medium is
described The simplicity, sensitivity, rapidity and reproducibility of the proposed method
are better than the previously reported F!A methods for the analysis of the CS.
The
method· is found to be precisely applicable for the analysis of CS to a variety of
environmental and commodity samples.
EXPERIMENTAL
Appa•·atus
Tecator tlow injection analyzer type-5012 equipped
with ALPKEM UV-VIS
spcGtrophotomcter lypc-510 matched with 0.55 em llow cell was employed lor the FIA
spcetrophotometnc determination of the surfactants. Syslronics 1-1-pH meter type-361 was
used for the pH measurement. The schematic FIA configuration used in the present method
is shown in Figure 3.1.
Reagents
All chemicals used were of analytical grade reagents (E. Merck).
Standard solution of cationic surfactants
The standard solution of cat1onic surfactants t.e. dodecyltrimcthylammonium bromide
( DTAB ),
\e\radccyltrimethylammonium
bromide
(TTAl3 ),
cetyltnmcthylammontum
bromide (CTAB) or cetylpyridmium chloride (CPC) of 1000 ppm (mg liC 1) were prepared
bv dissolving I 000 gin I lit deionized double distilled water. The working soluttons wen:
prepared bv the appropnatc dtlullon of the stock solulion
89
s = 600 I-ll
-"C'--·---1P-'
:!..!.!m!-'m!!..J---{,!.
1'.!:
14
R
0.25 mm
It
0.25 mm
60cm/0.5m~ 20cm/0.5~m ~ W
475 "'"
Figure 3.1. Schematic diagram of FIA configuration.
C =carrier, deionized double distilled water (pH 6.5±0.5).
R,= 1.5 x 10-4 M iron solution in 0.005 M nitric acid.
R 2=0. 7 M ammonium thiocyanate solution (pH 6.5±0.5).
S = ''olume of the analyte solution injected; AB and BC = teflon coils;
D =detector; \\' = waste
90
Solutions used for FIA determination of the cationic surfactants
Carrier solution (L} : Deionized double distilled water was employed as a carrier solution
to propel through the silicon tube of bore size !.14 mm.
Reagent solution (RJ: The iron solution (8.0 ppm or 1.5 x 10-4 M) in 0.005 M nitric acid
was used as reagent solution to propel through the silicon tube of bore size 0.25 mm.
Reagent solution (Rz) : Fresh ammonium thiocyanate solution (5.0 %, w/v or 0.7 M) in
deionized double distilled water was employed as reagent solution to propel through the
siilcon tube of bore size 0.25 nm.
Filtr·ation and degassing: All working solutions employed were filtered and degassed by
using Tecator degassing unit before use.
Procedure
Sample collection
The surface, ground, and municipal waste water samples from different locations of
Raipur city were collected in 100-m\ polyethylene bottles during November 1997 as
prescribed in the literature [2, 53]. For the commodity samples (i.e. detergents, soaps
and shampoo), their weighed amount was dissolved in 100 ml deionized double distilled
water. All
analysis.
sample solutions were filtered with Whatman tiltcr paper no. 42 before
91
l'roccdure for the determination of the cationic surfactants
The !iltcred and degassed deionized double distilled water (C), iron solution in the
nitric acid (R 1) and ammon1um thiocyanate (R 2 ) solutions were propelled by the peristaltic
pump (speed =, 48 cycles min- 1) through appropriate silicon tubes, Figure 3.1. The base
line of the reagent blank having practically neglig1ble absorption at wavelength, 475 nm
was set to zero at gain factor I. A 600 I-ll aliquot of the surfactant solution (contaimng 0.5,
1.0, 2.0, 5.0, 10.0, 15.0, 20, 25,30.0 ppm CPC) was injected by the rotary valve into the
!lowing stream by setting injection time( the span elapsed in delivery of the sample solution
from the mjection loop into the flowing stream), and residence time (the span elapsed after
injection of the sample solution until the complete recording of the peak signal) at 15, and
20 sec, respectively. The signal peak height was recorded at the absorption maximum, 475
nm. A calibration graph for the determination ofCS mthe term ofCPC was prepared by
1
plotting signal peak height versus concentration of the surfactant m ppm (mg lit )
injected. The filtered sample solutions were injected in a similar way. The concentration
of surfactant in the sample solut1ons was computed by using the calibration curve prepared
under similar condition
92
RI<:Sl!LTS AND DISCUSSION
Colour reaction of cationic surfactant with iron( III) and thiocyanate
Ferric ions react with SCN" ions to give a variety or red-orange coloured complexes in
the acidic solutions. The presence of cationic surfactant (CS) stabilize the existence of a
higher thiocyanato complex with enhanced kinetics [54].
+
Where, the value ofn may vary from 2 to 6.
The colour i ntcnsity of the Fe( 111)-SCN' complex quantitatively increases in proportion
of the concentratiOn of the cationic surfactant injected. This reaction has been used for the
flow injection analysis (FlA) spectrophotometric determination of the cationic surfactants
in the proposed work.
Absorption maximum of the complex
The absorption maximum, Ama., of the complex Fe(III)-SCN--Cs+ (CS+ denotes to the
cat10mc surfactants) was determined by recording the signal at different wavelength from
450 to 540 nm. A sharp A"'"' of the complex was recorded around 475 nm, Table 3.1,
Figure 3.2. The position of A""" d1d not change with respect to variation
concentration of the analyte
111
acidity, and the
93
Table 3.1. Determination of absorption maximun of the Fe(III)-SCN--Cs+ complex.
Volume of the analyte solution injected
Concentration of CI'C injected
Concentration of iron
Concentration of IIN03 in iron solution
Concentration of NH 4SCN
Gain factor
ln,jcction time
Residence time
Peak No. in
Figure 3.2
I
2
3
4
5
6
7
8
9
10
II
12
13
14
15
16
17
18
19
20
Wavelength
Peak height
nm
em
450
455
460
465
468
470
472
473
474
475
476
478
480
485
490
500
510
520
530
540
3.4
4.3
4.8
5.2
5.8
6.0
6.2
6.4
6.5
6.7
6.5
6.4
6.2
6.0
5.7
5.4
4.9
4.4
4.0
3.6
= 600 Ill
= 10.0 ppm
= 1.5 x 10-1M
= 0.005 M
=0.7 M
=I
= 15 sec
= 20 sec
Absorbance
Amax
nm
0.032
0.044
0.048
0.052
0.057
0.060
0.062
0.064
0.064
0.066
0.065
0.064
0.062
0.060
0.057
0.054
O.o48
0.044
0.041
0.035
475
94
5
3
6
7
8
9
10
11
12 13 14
15
4
16
17
2
18
19
Figur·c 3.2. Determination of absorption maximun of the l•'e(lli)-SCN·-cs+ complex.
Volume of the analyte solution injected
Concentration of CI'C injected
Concentration of iron
Concentration of HN0 3 in iron solution
Concentration of NII 4 SCN
Gain factor
Injection time
Residence time
=
61111
~--tl
= I 0.0 ppm
= 1.5 X 10~ M
=0.005 M
= 0.7 1\1
=I
= 15 see
= 211 see
zo
95
Optimization of analytical variables
Carrier Solution (C)
The deionized double distilled water was used as carrier solution (C)
111
the llowmg
stream for the investigation of the proposed system. The amount of the carrier solution
propelled aiTected the signal peak as well as the base \me properties.
The effect of
variation in the amount of earner solution was examined by changing the bore size of the
silicon tube.
An analyte signal of the highest peak with the minimum, and constant
absorption of the base line and better resolution of the analyte signals was recorded when
the yellow/blue coded silicon tube (bore size
=
1.52 mm) was used for propelling the
earner solution, Table 3.2, Figure 3.3. Signal peak height proportionally decreased when
the bore size of the tube was decreased from 1.52 to 0.70 mm may be due to incomplc\c
mixing/reaction or the variables. Similarly, the signal peak height slightly decreased when
the bore size was increased from 1.52 to 1.65 mm may be due to dilution of the complex.
In the present work, a silicon tube of bore size 1.52 mm was used to propel the carrier for
the detailed studies.
96
Table 3.2. Effect of different amount of the carrier (deionized double distilled water)
by changing the bore size of the silicon tube (used for propelling the
carrier, C) on the signal peak height and absorptivity of the Fe(III)-SCN'CS+ complex.
Volume of the analyte solution injected
Concentration of CI'C injected
Conccntr:~tion of iron
Concentmtion of IIN03 in iron solution
Concentration of NH 4SCN
Gain factor
Injection time
Residence time
Peak No. m
Figure 3.3
Code of
si I icon tube
Bore size of
silicon tube
mm
1
BIB
0.70
2
3
4
W/W
0.98
1.14
5
RJR
Y/BI
BI/BI
1.52
1.65
= 600 J.ll
= I 0.0 ppm
= 1.5 x
w-• M
=0.005 M
=0.7 M
=1
= 15 sec
= 20 sec
Peak hc1ght
em
3.4
5.7
6.1
6.7
6.5
B=Biack, W=Whitc, R=Rcd, Y=Yellow, BI=Biue.
Absorbance
at
475 mn
0.032
0.056
0.06!
0.066
0.064
97
4
2
5
3
Figure 3.3. Effect of different amount of the carrier (deionized double distilled water)
by changing the bore size of the silicon tube (used for propelling the
carrier, C) on the signal peak height of the Fe(III)-SCN--CS+ complex.
Volume of the analyte solution injected
Concentration of CPC injected
Concentration of iron
Concentration of HN03 in iron solution
Concentration of NH 4SCN
Gain factor
Injection time
Residence time
= 600 ).!I
10.0 ppm
4
= 1.5 X 10 M
= 0.005 M
=
=0.7 M
=I
= 15 sec
= 211 sec
98
Reagent solutions (R 1 and R1 )
The effect of amount as well as concentration of the tron, and ammonium thiocyanate
solutions (R 1 and R2 ) were examined separately by changing the horc size of the silicon
tube, and the concentration of the reagent solution.
The highest peak of signal with
smooth base line was recorded when orange/yellow coded silicon tube (bore size = 0.51
mm) was employed for propelling the iron solution, Table 3.3, Figure 3.4.
The
concentration of iron solution (R 1) was varied from 0.1 x I 04 to 5.5 x 10'4 M.
The
maximum and constant peak height of signal was recorded over concentration range of
4
( 1.0 - 4.0) x I 0 M Fe(III).
However, addition of Fe( III) beyond 4.0 x 1o-4 M caused
bifurcation of signal. Table 3.4, Figure 3.5. A 1.5 x 104 M of iron solution was sckcted
for the detailed studies.
The optimum bore size of the silicon tube used for propelling ammonium thiocyanate
solution (R 2) was found to be 0.38 mm (tube code= orange/green), Table 3.5, Figure 3.6.
The effect of concentration of the thiocyanate solution (R2) on the signal peak height was
examined over 0.02 to 1.5 M NH4SCN. The optimum concentration range of thiocyanate
was found between 0.4- 1.3 M NH.SCN. Beyond L3 M, the sib'llal width was widened,
Table 3.6, Figure 3.7.
studies.
A 0.7 M NH 4SCN solution was chosen for the further detailed
l)l)
Table 3.3. Effect of different amount of the iron solution by changing the bore size of
the silicon tube (used for propelling the reagent, R 1) on the signal peak
height and absorptivity of the Fc(III)-SCN--cs+ complex.
Volume of the analyte solution injected
Concentration of CJ>C injected
Concentration of iron
Concentration of HN03 in iron solution
Concentration of NH 4SCN
Gain factor
Injection time
Residence time
Peak No. in
l'1gure 3.4
I
2
0
~
4
5
6
7
8
Code of
si Iicon tube
0/Bl
0/G
0/Y
0/W
BIB
010
W/W
R!R
Bore size of
silicon tube
= 600 J.tl
= 10.0 ppm
= 1.5 X to-' M
=0.005 M
=0.7 M
=1
=IS sec
= 20 sec
Peak height
mm
em
0.25
0.38
0.51
0.64
0.70
0.85
0.98
1.14
3.7
6.2
6.7
6.2
6.1
5.8
5.5
4.9
A bsorba nee
at
475 nm
0.038
0.062
0.067
0.062
0.061
0.058
0.055
0.049
O=Orange, BI=Blue, G=Green, Y=Yellow, W=White, B=Black, R=Red
100
3
2
4
5
6
7
8
1
Figure 3.4. Effect of different amount of the iron solution by changing the bore size of
the silicon tube (used for propelling the reagent, R 1) on the signal peak
height of the Fe(lll)-SCN--Cs+ complex.
Volume of the analyte solution injected
Concentration of CPC injected
Concentration of iron
Concentration of HN03 in iron solution
Concentration of NH4 SCN
Gain factor
Injection time
Residence time
=600 ~I
= 10.0 ppm
= 1.5 X 10--4M
=0.005 M
=0.7 M
=I
= 15 sec
= 211 sec
101
Table 3.4. Effect of different concentration of the iron solution (11ropellcd through the
channel R 1) on the signal11eak height and absorptivity of the Fe(lll)-SCN-cs• complex.
= 600 )11
= 10.0 ppm
Volume of the analyte solution injected
Concentration of CI'C injected
Concentration of HN03 in iron solution
Concentration of N11 4SCN
Gain factor
Injection time
Residence time
Peak No. in
Cone. of iron in
Figure 3.5
the reagent, R 1
=0.005 M
= 0.7 M
=1
= 15 sec
=20 sec
Peak height
Absorbance
a(
M(xi0-4)
em
475 nm
I
2
0.1
0.2
1.1
1.9
3
0.3
4
5
6
7
8
9
10
ll
12
0.4
0.5
0.7
0.9
1.0
1.5
2.0
4.0
4.5
5.0
5.5
2.6
3.1
4.2
5.3
6.1
6.7
6.8
6.8
6.9
7.0
7.1
7.1
0.0 II
0.019
0. 027
0.031
0.042
0.053
0.061
0.067
0.068
0.068
0.069
0.070
0.071
13
14
O.o?l
102
8
9
10
11
12
13
14
7
6
5
4
3
2
AA
Figure 3.5. Effect of different concentrations of the iron solution (propelled through
the channel R 1) on the signal peak height of the Fe(lii)-SCN·-cs+ complex.
Volume of the analytc solution injected
Concentration of CPC injected
Concentration of HN03 in iron solution
Concentration of NH~SCN
Gain factor
Injection time
ncsidcncc time
= 600 ).11
= 10.0 ppm
= 0.005 M
=0.7 M
=I
=IS sec
= 20 sec
103
Table 3.5. Effect of different amount of the thiocyanate solution by changing the bore
size of the silicon tube (used for proJICIIing the reagent, R 2) on tbc signal
pcal•hcight and absorptivity of the l<'e(lli)-SCN·-cs+ complex.
Volume of the analyte solution injected
Concentration of CI>C injected
Concentration of iron
Concentration of BN0 3 in iron solution
Concentration of NH 4SCN
Gain factor
I njcction time
Residence time
Peak No. in
Figure 3.6
I
2
3
4
5
6
7
O~Orangc,
Code or
silicon tube
0/B!
0/G
0/Y
0/W
BIB
010
W/W
Bore size of
silicon tube
mm
0.25
0.38
0.51
0.64
0.70
0.85
0.98
~
600 Ill
lO.O ppm
= 1.5 x to-' M
= 0.005 M
=0.7 M
=1
= 15 sec
=20 sec
~
Peak height
em
6. I
6.6
6.4
6. I
5.9
5.4
5.0
Absorbance
at
475 nm
0.062
0.067
0.065
0.062
0.059
0.054
0.050
!31=!3\ue, G=Grcen, Y=Yeilow, W=Whitc, B=Black.
104
2
1
3
4
5
6
7
Figure 3.6 Effect of different amount of the thiocyanate solution by changing the bore
size of the silicon tube (used for propelling the reagent, R2) on the signal
peal• height of the Fe(Ill)-SCN--cs+ complex.
Volume of the analyte solution injected
Concentration of CPC injected
Concentration of iron
ConccntratiOJl of HN03 in iron solution
Gain factor
Injection time
Residence time
"' 600 J.!l
"'10.0 ppm
"' 1.5 X 10-1 M
"' 0.005 l\1
"'I
"' I 5 sec
"'20 sec
lOS
Table 3.6. Effect of tliffc•·ent concentration of thiocyanate (in reagent lt 2) on the sign:• I
peak height anti absorptivity of the Fe(III)-SCN·-cs+ cOiliJtlex.
Volume of the analytc solution injected
Concentration of CI'C injected
Concentration of iron
Concentration of liN03 in iron solution
Gain factor
Injection time
Resilience time
Peak No. in
rigure 3.7
Cone. ofthiocyanate
in the reagent, Rz
=
= IIJ.O p[tm
= 1.5 X tO-' M
= 0.005 M
=1
= 15 sec
= 21J sec
Peak height
em
9
10
0.02
0.03
0.04
0.05
0.2
0.3
0.4
0.6
0.7
0.8
II
0.9
12
13
14
15
16
1.0
1.2
1.3
1.4
1.5
1.1
2.6
4.1
5.1
5.8
6.4
6.6
6.8
6.8
6.8
6.8
6.9
7.1
7.2
7.2
7.3
2
3
4
5
6
7
g
Absorbance
at
M
I
c.oo ~-tl
475 nm
0.011
0.026
0.041
0.051
0.052
0.064
0.066
0.068
0.068
0.068
0.06S
0.069
0.071
0.072
0.072
0.073
106
6
7
8
9
10
11
13
12
14
15
16
5
4
3
2
1
A
Figure 3. 7. Effect of different concentrations of the thiocyanate solution (propelled
through the channel R2 ) on the signal peak height of the Fe(lll)-SCN·-cs+
complex.
Volume of the analyte solution injected
Concentration of CPC injected
Concentration of iron
Concentration of HN0 3 in iron solution
Gain factor
Injection time
Residence time
= 600 ).ll
= 10.0 ppm
= 1.5
4
10 M
=0.005 M
=I
= 15 sec
= 20 sec
X
107
Effect of acidity
The pH value of the earner, and R2 solution were kept constant, 6.5±0.5 for all the
experimental work. The acidity of the iron solution was varied with acids 1.e. IICI, H2S0 4 ,
HN03 . All of them imparted same height to the signal at "'"'"'' 475 nm. Of these, HN03
acid was selected for the detailed investigation as scvcrul reductants
/.<'.
CN', Mn( II),
Sn(ll), S2-, S20_, 2·, oxalic acid, ascorbic acid did not interfere. At least 0.003 M HNO, was
required for the maximum and constant peak height of signal and no appreciable change in
the peak height was observed upto addition of 1.0 M HN03 . But after 0.6 M HN03, no
smooth base line was recorded, Table 3.7, Figure 3.8. The concentration of HN03 in the
reagent solution (R 1) was maintained to be 0.005 M for further experimental work.
Similarly, the acidity range for the sample (analyte) solution mjccted was very wide and
found to be in the range of pH, 2.0- 8.0, Tab it: 3.8, Figure 3.9.
108
Table 3.7. Effect of different concentration of nitric acid (used in the reagent R 1) on
the signal peak height and absorptivity of the Fe(lll)-SCN--Cs+ complex.
Volume of the analyte solution injected
Concentration of CI'C injected
Concentration of iron in iron solution
Concentration of NII.,SCN
Gain factor
Injection time
Residence time
Peak No. in
Figure 3.8
I
2
3
4
5
6
7
8
9
10
Acidity in
reagent R 1
M HN0 1
0.0005
0.001
0.003
0.005
0.05
0.2
0.4
0.6
0.8
1.0
Peak height
= 600 ).ll
= 10.0 ppm
= l.Sx 10_.. M
= 0.7
M
=I
= 15 sec
=20 sec
em
Absorbance
at
475 nm
5.7
6.1
6.5
6.7
6.8
6.8
6.7
6.9
6.8
6.8
0.057
0.061
0.065
0.067
0.068
0.068
0.067
0.069
0.068
0.068
109
2
3
4
6
7
8
9
10
Figure 3.8. Effect of different concentrations of nitric acid (used in reagent R 1) on the
signaltleak height of the Fe(lli)-SCN--Cs+ complex.
Volume of the analyte solution injected
Concentration of CPC injected
Concentration of iron
Concentration of Nll~SCN
Gain factor
Injection time
Residence time
= 600 f.ll
= 10.0 ppm
= l.Sx 10-l M
=0.7 M
=1
=IS sec
= 211 sec
110
T:1blc 3.8. Effect of different 1111 of the sample (analyte) solution on the signal peal>
height and absorptivity of the Fe(III)-SCN' -CS+ complex.
Volume of the analytc solution injected
Concentration of CPC injected
Concentration of iron
Concentration of HN03 in iron solution
Concentration of NII 4 SCN
Gain factor
Injection time
Residence time
Peak No. m
Figure 3.9
pH of the
analyte
I
2
3
4
5
6
7
2.0
6.4
3.0
6.5
5.0
6.0
7.0
8.0
9.0
6.6
6.6
6.5
6.5
6.3
Peak height
em
= 600 ~-tl
10.0 ppm
-I
X 10 M
= 0.005 M
= 11.7 M
=I
= 15 sec
= 20 sec
=
= 1.5
Absorbance
at 475 nm
0.064
0.065
0.066
0.066
0.065
0.065
0.063
Ill
2
3
4
5
6
7
Figure 3.9. Effect of different pH of the analyte solution injected on the signal peak
height of the Fe(lli)-SCN·-cs+ complex.
Volume of the analyte solution injected
Concentration of CPC injected
Concentration of iron
Concentration of IIN0 3 in iron solution
Concentration of NH~SCN
Gain factor
Injection time
ltcsidcncc time
=
600 J..ll
= 10.0 ppm
= \.5 X 10--1 l\1
=0.005 M
= 0.7 1\1
=I
=
=
15 sec
2tl SCl"
112
Effect of temperature
The e\Tccl of temperature on the signal peak height was examined. The tc\1on coil, BC
was dipped into the water bath and the temperature was varied from 15 to SO
oc.
1\
maxnnum and constant peak height of signal was obtained when the temperature of the
wain baih was v:ur<.Od ov<.Or
:w- 40"C, Tabk :l '1,
hgurc :l 10
llow<:v<:r, above 40 "C, lh<:
signal peak herght I colour intensity of the complex decreased may be due to either
decrease in the density of the flowing solution or decomposition of the complex or both.
113
Table 3.9. Effect of different temperature of the water bath (into which the teflon coil
BC was dipped) on the signal peak height and absorptivity of the Fe(lli)SCN--cs+ complex.
Volume of the analyte solution injected
Concentration of CPC injected
( 'onceutnttion or iron
Concentration of IIN03 in iron solution
Concentration of NII 4 SCN
(;ain factor
Injection time
Residence time
Peak No m
Figure 3 10
Temperature of
water bath,
oc
1
15
2
J
4
5
6
20
7
25
30
40
45
50
= 600 ~-tl
=
10.0 ppm
= 1.5 x
ttr" M
= 0.005 M
=0.7 M
=I
= 15 sec
=20 sec
Peak he1ght
em
Absorbance
at 475 nm
6.2
6.5
6.6
6.6
0.062
0.065
0.066
0.066
6.5
6.3
0.065
0.063
6.1
0.061
114
1
z
3
4
5
6
7
Figure 3.1 0. Effect of different temperature of the water bath (into which the teflon
coil 8C was dipped) on the signal peak height of the Fe(lll)-SCN--Cs+
complex.
Volume of the ana lyle solution injected
Concentration of CPC injected
Concentration of iron
Concentration of IIN0 3 in iron solution
Concentration of NII~SCN
Gain factor
Injection time
lksitll"nl"l" timc
600 )..11
10.0 ppm
= 1.5 x ur' 1\1
=0.005 M
=0.71\1
=
=
=I
15 sec
=211 scc
=
115
Effect of injection time and residence time
The effect or InJection time (the span elapsed in delivery of the sample solution from
the 1llJecuon loop mto the llowmg stream), and residence tune (the span elapsed after
injection of the sample solution until the complete recording of the peak signal) on peak
he1ght or signal were cxammed. At least I 0, and 15 sec, respectively were required to
obtam a maximum and constant peak height of signal. No adverse effect was observed if
the duration or injectiOn, and residence time were prolonged upto 20 and 40 sec,
respectively.
In thts work, a total cycle time of ,35 sec (injection time = 15 sec and
restdence time= 20 sec) was used to get' a complete picture of the analyte si1,>nal. The
sample throughput (sample analysis rate per hour) of the method was determined and
found to be I 00 samples h- 1 when the speed of the peristaltic pump, and the tlow rate of
1
the 1111xed solul1on were 4ll cycles min- 1 , and 3.5 ml min- , respectively
116
Effect of the length of the tcllon coil and volume of the analyte solution
The effect of len1,>1h of both teflon coils (AB and BC), and volume of the analyte
solution InJected on the peak height of signal were examined. In this work, the bore size
of the tenon tubes used was kept constant (0.5 mm) throughout the work. The length of
both cmls were vaned rrom I U -YU em but no appreciable change was observed 1n the peak
height of signal, Table 3. I 0-3.11, Figure 3.11-3.12. The signal peak height was greatly
affected w1th the variation in volume size of the ana1yte solution injected over the aliquot
range of I 00 - 600
~I
but after volume size of 600 f.ll no adverse effect was observed,
Table 3.12, F1gure 3.13. For the detailed experimental work, length of the tetlon coils
(AB and BC), and volume of the analyte selected were to be 60 em, 20 em, and 600
respectively.
~1.
117
Table 3.1 0. Effect of different length of the teflon tube (mixing coil) between merging
zone AB on the signal peak height and absorptivity of the Fe(III)-SCN-cs• complex.
Volume of the analyte solution injected
Concentration of CPC injected
Concentration of iron
Concentration of IIN03 in iron solution
Concentration of N H~SCN
Gain factor
Injection time
Residence time
Peak No. in
Figure 3. I I
I
2
-'"
4
5
Length of the teflon
tube between AB
em
10
20
30
60
90
600 J.!l
10.0 ppm
1.5 X llr"' M
= 0.005 M
=
=
=
=0.7 M
=I
= IS sec
= 20 sec
Peak height
em
Absorbance
at
475 nm
6.3
6.4
6.5
6.6
0.063
0.064
0.065
0.066
6.6
0.066
118
1
2
3
4
5
Figure 3.11. Effect of different length of the teflon tube (mixing coil) between merging
zone AB on the signal peak height of the Fe(III)-SCN--CS+ complex.
Volume of the analyte solution injected
Concentration of CPC injected
Concentration of iron
Concentration of HN03 in iron solution
Concentration of NH~SCN
Gain factor
Injection time
lksidcncc lime
~
600 J.ll
~ 10.0 ppm
= 1.5 X 10--1M
~o.oo5
=0.7 M
=I
~
)5 SCl'
= 20sec
M
119
Table 3.11. Effect of different length of the tetlon tube (mixing coil) between me•·ging
zone BC on the signal peak height and absorptivity of the Fe(lli)-SCN·CS+ comlllex.
Volume of the analytc solution injected
Concentration of CI'C injected
( 'oru.:cntnttion of irou
Concentration of IIN03 in iron solution
Concentration of NII 4 SCN
Gain factor
Injection time
Residence time
Peak No. in
Figure 3 12
Length of the teflon
tube between BC
=600 (.l.l
= 111.(1 ppm
= 1.s x ur• M
=0.005 M
=0.7 M
=I
=IS sec
= 20 sec
Peak height
Absorbance
em
em
at
475 nm
-'
10
20
30
4
60
5
90
6.4
6.6
6.5
6.4
6.3
0.064
0.066
0.065
0.064
0.063
I
2
0
120
2
3
4
5
Figure 3.12. Effect of different length of the teflon tube (mixing coil) between merging
zone BC on the signal peak height of tbe Fe(III)-SCN--Cs+ complex.
Volume of the analyte solution injected
Concentration of CPC injected
Concentration of iron
Concentration of IIN03 in iron solution
("onccntration of NII~SCN
Gain factor
lnjrction timr
Rrsidt•nce time
= 600 J.ll
= 10.0 ppm
1.5 X 10-1 l\1
= 0.005 l\1
=0.7 M
=I
= 15 sec
= 211 sec
=
121
Table 3.12. Effect of different volume size of the analyte solution injected in the
flowing stream of reagent on the signal11eak height and absoq1tivity of the
l'c(III)-SCN--Cs+ complex.
( 'onn•n Ira I ion of (' I'C i n_jt•t•ll"d
I 0.0 )1)1111
= I.S X 10-1M
=0.005 M
=0.7 M
=l
=IS sec
=20 sec
=
Concentration of iron
Concentration of IIN0 3 in iron solution
Concentration ofNII 4SCN
Gain factor
Injection time
Residence time
Peak No. in
Figure3.13
Sample volume
f.! I
Peak height
em
Absorbance
at 475 nm
I
2
3
4
5
6
7
100
200
300
400
500
600
700
4.0
4.6
5.3
5.7
6.0
6.6
6.6
0.040
0.046
0.053
0.057
0.060
0.066
0.066
\22
6
7
5
3
4
2
1
Figure 3.13. Effect of different volume size of the analyte solution injected in the
flowing stream of the reagent on the signal peak height of the Fe(lll)SCN--Cs+ complex.
Concentration of CPC injected
Concentration of iron
Concentration of BN0 3 in iron solution
Concentration of N II~SCN
Gain factor
Injection time
Kcsidcncc time
= 10.0 ppm
= 1.5 X 104
0.005 M
=0.7 M
=
=I
= 15 sec
= 211 sec
M
123
Composition of the complex
Ferric iron react with SeN- in the nitric acid solution to g1vc a red-orange coloured
binary complex Fc(lli)-SCN-, wh1eh m the presence of the cationic surfactant (eS) form a
more deep red-orange coloured ternary complex, Fc(lll)-SCN--Cs+. The composition of
the ternary complex, :[Fe( SCN), [m CS+) >+m-n was determined by the curve-llttmg method
by plotting log distributiOn ratio D = (h,qlhmux- h"1) (h,q =peak height of the signal when
the reagent was in equilibrium, and hmux =peak height of the signal when the reagent was
in constant excess) versus log molar concentration of the reagent propelled. The values of
slope for the log (h,/h"'"'- h"1) versus log [SCN-), and log (hc/hmax- h,q) versus log [FeH J
were found to be 3.1, and 1.1, close to integer 3 and I, respectively. The slope values
suggested the mvolvemcnt of 3 and I moles of seN- and CP', respectively with I mole of
Fe'', Tables 3.13-3.14. Figures 3.14-3.15. The reaction mechanism can be expressed as:
FeH
f
3 SCN +
CP'
______
.........._
-=.....------
llowever, m the nitric ac1d solution a four or
SIX
co-ordinated iron-thiocyanate
complex 1s expected.
Fe" '
3 SCN" +
No,-
~===="'=
+ CP'
or
- 1+
h::
1-
3 SCN
+
3 NO,-
+
__:::,.._
.........- - - - - cr+ ____
\[Fe (SCN), NO,]CPl
124
Table 3.13. Curve-fitting method for the determinution of molar ratio of the Fe(lll) to
S('N- in the lie(lll)-SCN--CS' COIIljtlcx.
Molar concentration of Peak height
thiocyanate
h, em
Distribution ratio of iron
M
logM
hmax
hcq
0.02
-1.69
6.8
1.1
0.19
-0.71
0.03
-1.52
6.8
2.6
0.62
-0.21
0. 04
-I .40
6.&
4.1
1.52
0.1 R
0.05
-1.30
68
5.1
3.00
0.48
D= ( h,qlhmux-hcq)
Slope
log I)
3.1
125
0.6 r - - - - - - - - - - - - - ,
0.4
0
OJ)
0
-0.4
- 0 .S L---_-,.L.._6--_....,,...._4:-----_, . . _-::-2-----'
log M
Figure 3.14. Curve-fitting method for the determination of molar ratio of the Fe( III)
to SCN' in the Fe(lll)-SCN--Cs+ complex by plotting log (h,./hm.,-h,.,1)
versus log M concentration of thiocyanate solution propelled through the
channel R 2•
126
Table 3.14. Curve-fitting method for the determination of mole ratio of the Fe( II I) to
CS+ in the Fe(IIl)-SCN--Cs+ complex.
Molar concentration
of iron
M(
10'4 )
Peak height
h,cm
Distribution ratio of the CS
logM
hnwx
0.09
-5.05
6.8
1.1
0.09
-0.72
() 18
-4.75
6.8
1.9
0.39
-0.41
027
-4.57
6.8
2.6
0.62
-0.21
0.36
-4.44
6.8
3.1
0.84
-0.08
X
hcq
D
=
(heihnno.,-heq)
Slope
logD
1.1
127
0
- o.t.
- 0·8 L___ _ _s='-____
o
. ,. 4....,.8-----:t.-':.s------JL,.'-t,--J
log M
Figur·e 3.15. Curve-fitting method for the determination of mole ratio of the Fe( Ill) to
CS+ in the Fe(lli)-SCN--Cs+ complex by plotting log (h,.,,fhm.-·h,.• l versus
log M concentration of the iron solution propelled through the channel R,.
128
Effect of type of sorfactants
The effect of vanous types of surfactants on the colour intensity I signal peak height of
the
Fe( Ill )-SCN-
comrlcx
was
examined.
The
callomc
surfactants
( CS)
'· <'.
dodecyltrimethylammonium bromide (DTAB), tctradecyltrimethylammonium bromide
(TTAB), cctyltrimethylammonium bromide (CTAB), cetylpyridinium chloride (CPC) were
found to remarkably enhance the colour intensity of the complex as they are able to fonn
ion-pair complex unlikely to neutral and anionic surfactants i.e. Triton X-1 00, Triton X300, Brij-35, sodium laurylsulphate (SLS). The value of apparent molar absorptivity of the
1
complexes with above four surfactants lie in the range of(2.10- 4.30) x 10 I mor' em·' at
A.,,," , 475 mn, Table 3.15. The h1ghest sensitivity was recorded w1th cetylpyridinium
chloride (CPC) may be due to either higher reaction kinetics or higher basicity or
combmation or both, Table 3.16, l'igure 3.16. Hence, in this work, CPC was selected for
the detailed studies.
129
Table 3.15. Effect of various surfactants on the absoq1tivity of the Fe( 111)-SCN--Cs+
complex.
Volume of the analyte solution injected
Concentration of the surfactant injected
Concentration of iron
Concentration of IIN03 in iron solution
Concentration of N H~SCN
Gain factor
Injection time
Residence time
Surfactant
=600 ~I
= 10.0 ppm
= 1.5 x ur~ M
0.005 M
=0.7 M
=I
= 15 sec
= 20 sec
=
A.nlHX
nm
Cetylpyndinium chloride (CPC)
Cctyltrimcthylammonium hromidc (CTi\1~)
Tctradccyltrimcthylammonium bromide ('!TAll)
Dodecyltrimethylammonium bromide (DTAB)
475
475
475
475
Apparent value of 1:
1
lmor 1 cm- 1 (x 10 )
4 30
J ()()
2.40
2. I 0
130
Table 3.16. Effect of various cationic surfactants on signal peal< height and
ahsoq1tivity of the Fc(III)-SCN--cs• complex.
Volume of the analytc solution injected
Concentration of the surfactant
t:onccntration of iron
Concentration of IIN03 in iron solution
Concentration of N II~SCN
Gain factor
Injection time
Residence time
Peak No m
F1gure 3.16
I
..,
3
4
Surfactant injected
Cetylpyridinium chloride
=600 J.!l
10.0 ppm
X 10--1M
=0.005 M
= 0.7 M
=I
= 15 sec
= 20 sec
=
= 1.5
Peak height
em
Absorbance
at 475 mn
6.5
0.065
4.4
0.044
3.9
0.039
3.6
0.036
(CPC)
Cctyltnmcthylummon1um
bromide (CTAB)
Tetradecyltrimethylammonium
bromide CfTAl3)
Dodecyltrimethylamrnoniurn
bromide (DTAB)
131
2
3
L--------------------------------~
Figure 3.16. Effect of various cationic surfactants on the signal peak height of the
Fc(III)-SCN·-cs+ complex.
Volume of the analyte solution injected
= 600 J.tl
Concentration of the surfactant injected = 10.0 ppm
= 1.5 x 10-1M
Concentration of iron
Concentration of IIN03 in iron solution = 0.005 M
Concentration of NII~SCN
= 0.7 1\1
Gain factor
=I
Injection time
= 15 sec
Residence time
= 20 sec
132
Optimum conccninttion range, detection limit, sensitivity and statistics
The Signal re:oh heoght lin
th~
dollerent concenlraloon or ( 'I'C os shown
111
Table 3 17,
F1gure 3.17. The method followed linearity upto 30.0 ppm of CPC w1th slope, intercept
and correlation cocrtiCJcnt of 0 66, 6.58 x 10"2 , and 0.99, respectively
The value of
apparent molar absorptivity of the Fe(lli)-SCN·-cs+ complex (calculated by taking the
concentration of the surfactant inJected in molarity and path length of the flow cell to he
0.55 em) m the term ofCPC was (4.30) x 10 1 I mor' em·' at absorption maximum, 475
nm The detection limit (>peak height than 3 std. dev.) was 280 ppb
ere
The relative
standard deviation for the analysis of six different solutions of the surfactants contaimng
5.0 ppm
ere was found to be ±0.9%, Table 3. 18, Figure 3. 18.
133
Table 3.17: Calibration graph (peak height versus concentration) for the I<' IA
determination of the cationic surfactants.
Volume of the analyte solution injected
Concentration of iron
Conccnlrlltion of IIN03 in iron solution
Concentration of N H4SCN
Gain factor
ln,it•ction timl'
Residence time
Peak No. in
Figure 3.17
Concentration
ofCPC, ppm
I
2
3
0.5
10
2.0
5.0
lO.O
l5.0
4
5
6
7
8
9
20.0
25.0
30.0
Peak height
em
03
07
13
3.4
66
10.2
13.2
17.1
19.3
=600 J.!l
= 1.5 x 10-1M
= 0.005 M
=0.7 M
=I
= 15 sec
= 20 sec
Absorbance
at475 nm
0 003
0.007
0 013
0.034
0.066
O.l02
0.132
0.171
0 193
134
3QO ppm
25.0
20.0
15.0
10.0
5.0
20
o.o
0.5
1.0
Figure 3.17. Calibration graph (peak height versus concentration) obtained from the
standard solutions of CPC, 0.5-30.0 ppm for the FIA determination of
cationic surfactants.
Table 3.18. I' recision of the present method.
Volume of the analytc solution injected
Concentration of CI'C injected
Concentration of iron
CmH'l'nlration of IINOJ in iron solution
Concentration of N 11 4SCN
Gain factor
ln,jection time
Residence time
No. of
observations
Absorbance
at Amu'
Peak
height
em
11
6
"
0.067
0.068
0.067
0.066
0.067
0.067
6.7
6.8
6.7
6.6
6.7
6.7
Mean
peak
height, ern
== (,()() Jll
== I 0.0 ppm
== I.S X 10-1 M
== U,UUS M
== 0.7 M
== I
==IS sec
= 20 sec
Standard
deviation
dcvm11on
x,
6.7
Relative
standard
I ~~'t)
Is
6.32
X
10'2
0.9
136
Figure 3.18. Standard deviation for 6 different solutions containing tO.O ppm f:PC.
Volume of the analytc solution injected
Concentration of (:J>(: injected
( 'onccntration of iron
Concentration of IJN03 in iron solution
Concentration of NII 4SC:N
Cain factor
Injection time
Residence time
= 600 ~J,I
= I t).(l ppm
= 1.5 X 10-1 M
= 0.005 M
=0.7 M
=I
=IS sec
= 20 sec
137
Effect of diverse ions
The effect of various diverse ions in the determination of 2.0 rpm CI'C (at gam l~tctor
I)
was exammed serarately. None of the tested diverse ions including neutral and anionrc
surfactants were found to mterlen: in the dctcnnination or CPC urto ccrtam levels.
However, the ions 1.e. V(V), F, CN- are tolerated at moderate levels because they react
either with SCN- or Fe(lll) to give colourless to coloured complexes. Their tolerance
limits (in ppm) in the determination ofCPC are summarized in Table 3.19.
138
Table 3.19. Effect of various diverse ions in the determination of2.0 ppm CS.
Volume of the analytc solution injected
Concentration of CI'C injected
Concentration of iron
Concentration of IIN03 in iron solution
Concentration of N11 4SCN
Gain factor
Injection time
Residence time
"' 600 1-!1
"' 2.0 (IJlffi
10""1 M
=0.005 M
= 1.5 X
"'0.7 M
=1
= 15 sec
"'20 sec
Ions
Added as
Na(l)
NaCI
500
K( I)
KCI
500
Cl
NaCI
400
N01-
NaN01
400
SO/
Na"so,
400
SLS
Sodium laurylsulphate
250
Ca(ll)
CaCO,
200
Mg(ll)
s--•
MgC01
200
Na 2S
200
citrate
Sodium citrate
200
tartrate
Sodi urn tartrate
200
Tnton X-100
Triton X-100
200
Tnton X-300
Triton X-300
200
Bnj-35
Brij-35
200
Tolerance limit*
(ppm)
Cont..
139
Cont...
Table 3.19.
Ions
i\ddcd as
Tolerance limit*
(ppm)
AI( Ill)
AI(NO,h. 9H,O
50
Cr(VI)
K2Cr201
50
P0 41 -
Na1 P0 4. l2H 20
50
so, 2-
Na 2 S0 1
50
Br"
KBr
50
Th10urca
NII 2CSNI1 2
40
I
Kl
40
N1( II)
N1S0 1.6lizO
25
Cu(ll)
CuS0 4 . 7H 20
20
Zn(ll)
ZnS0 1 71-1 20
20
Mn(ll)
MnCI 2. 4H 2 0
20
Co(! I)
CoSO,. 1H20
20
81(111)
Bi 2 (S04)J
20
Oxal1c acid
Oxalic acid
20
Ascorbtc acid
Ascorbic acid
20
V(V)
NH1VO,
10
F
NaF
10
CN.
KCN
10
* ±2 o, o error.
140
Comparison with other methods
The valld1ty and prccis1on of the results of the proposed method was checked with well
established Orange II- FIA method, Table 3.20. The analytical potentiality of the prorosed
1nethod
IS
compared w1th the other established methods, Table 3.21.
In v1ew of the
simplicity, specificity and rapidity, the proposed method seems to be superior to the most
of the FIA methods reported.
141
Table 3.20. Application of the method in the determination of cationic surfactant in
water and detergent samples in the term of CPC.
Sample
by the Orange II method
CPC found
r.s.d. •
ppm
± o/o
Pond.\', Raipur
Kankali
Ni\
Raja
Ni\
Bendri
NA
Katora
NA
Budha
NA
Handi
NA
(;round water aquifers (tuhewell.\), Raipur
Kar1kal1pata
Raja talab
Katora talab
lludha ram
llaudi para
Municipal waste water, Raipur
Raja talab
Katon1 talab
2.h
0.9
1.6
2.0
2.5
3.2
3.5
0.8
0.9
0.8
1.0
0.9
Ni\
NA
NA
NA
NA
OK
0
NA
NA
NA
NA
4.2
5.0
3.0
3.7
Kola
Dagania
Household Commodities
Vim
NA
(Mfd by Hindustan Lever Ltd., India)
Ghari Detergent
21.2
(Mtd. by Rahul Detergents, India)
0.5
1.0
1.2
1.3
<)
1.0
0.8
I)<)
1.0
1.0
0.9
0.8
0.9
5.0
0.7
1.9
20.0
1.0
1.8
31.0
1.1
1.7
72
1.0
1.7
53
0.9
132
1.6
I35
0.8
150
1.7
148
1.0
165
1.5
168
1.1
30 4
Surf dctcrgcut
by the present method
CPC found
r.s.d. •
ppm
±%
(Mfd. by Hindustan Lever Ltd., India)
Lifebuoy soap
70
(Mf(l. by Hindustan Lever Ltd., India)
Nrrnw soap
54
( Nirma Chcmrct-Iis. lndra)
( 'li111c Plu~ ~hampoo
(~lid
by llmdustan Lever Ltd., Indta)
Pantcne ~iw:n1poo
(Procter & Gamble India Ltd.)
Organ res sha1npoo
t'lfd bv llmdustan Lever Ltd .. India)
·~"
''""Pic' "ere anal~ ted.
]\:A ~not applicable
142
lahll' 3.21. <:umparison of the (ll·cscnt nwthod with other JilA method~ fur lhl' dctl•rrninutiun of
'-'ntionil' surfa-.·tant,.
M<:thod
.1\.111.1\
Wor~1ng
range
nrn
ppm
pi I/ Solvent Prior Sample
acHllly
Scpan through
range
-tion
-put, h' 1
'l'etrabrornophenol
phthalein ethyl
cs!er (TBPE)
610 () 12-0 16 8 510 ()
< hangc II
·IX~
'J'ctrabrornophcnol
phthak1n ethyl
ester (TBPE)
610 0.2-0.8
R
-.---
Anionic surliu;tants
interefcrc
l<ci'
36
ethane
70-1 ()()()
I3romochlorophenol 605 2.0-18.0
blue+qurnidine
Fe(lii)-SCN
1.2-dichloro-
Remar~s
1.6
l'IICI 1
R
20
Scnsrt1vitv 1s very poor wrth 4_1
low sarnrle throu('.hpul
7 012.5
I,2-dichloro
ethane
R
60
Many metal 1ons mtcrfcn:
6.87.8
1,2-dichloro
ethane
R
30
Low sample throughput and 52
..
preCJSJOil.
NR
100
Simple, specific, rapid,
and reproducible.
475 0.5-30.0 0.003- Water
0.6M
HNO,
*Present method, R =Required, NR =Not required.
45
*
143
APPLICATION OF TilE MJ<:TIIOD
The present method has been applied for the determination of the cationic surfactant
(CS) in the term of cetylpyridinium chlonde (CPC) to the various cnvm>nmcntal and
commodity samples 1.e. surface waters, ground
detergents, soaps, and shampoo, Table 3.20.
waters, municipal waste waters,
A 600 J.d aliquot of the filtered sample
solution was inJeCted m a similar way as described in the procedure.
The commodity
samples were dissolved with water and their filtered solutions after appropriate dilution
were injected. The peak height of signal was recorded at 475 nm and concentration of
CS m the term of CPC was evaluated by using calibration curve. The concentration level
of the eatwmc surli1ctants in the(, surli1ce water, 5 ground water, 4 mulliC'I>al wa,tc wat<:l,
and g commodity samples w<:re l1c m the range 1.6 - 3.5 (mc:an
2.6, med1an
2.5,
standard devwtion · 0 7), 0. 5 - 1.3 (mean • 1.0, median · 1 0, standard deviat1on
tU ).
3 0- 5.0 (mean~ 4.0, med1an = 3.9, standard deviation= 0.8), and 5.0- 168 ppm (mean=
79, median= 62, standard deviation~ 63), respectively. The main expected sources of the
catiomc surfactants m water bodies of Raipur area
are household commodities 1.e.
detergents, soaps, shampoo, liberated from the human activities.
144
CONCLUSION
The proposed method is very simple, rapid and specitic for the F!A determination of
the cationic surfactants i.e. DTAB, TTAB, CTAB, CPC in the various water and
commodity samples and reproducibly applicable down to 0.5 ppm CPC in the water
samples. The selectivity, sensitivity and reproducibility and rapidity of the proposed
method is better than most of the methods reported for the determination of the cationic
surfactants. All
the
stationary surface water bodies (ponds), municipal waste water
reservoirs and ground water aquifers lie nearer to the sources i.e. ponds, municipal waste
water reservoirs, etc. of Raipur city were found to be contaminated with CS in the range of
0 'i - 'i .0 ppm CI'C
145
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