DOI: 10.2478/s11532-007-0007-y
Research article
CEJC 5(2) 2007 581–589
Determination of sulfanilamide based on the
Mn(II)-catalyzed oscillating chemical reaction
Jinzhang Gao1∗ , Dongyu Lv1,2 , Wu Yang1, Xiaoxia Wei1 ,
Jie Qu1, Hua Chen1, Hongxia Dai1, Jie Ren1
1
2
Chemistry & Chemical Engineering College,
Northwest Normal University,
Lanzhou 730070, P.R. China
Chemistry & Chemical Engineering College,
Lanzhou University,
Lanzhou 730000, P.R. China
Received 17 October 2006; accepted 27 November 2006
Abstract: A convenient and sensitive method for determination of sulfanilamide (SNA) was described
based on the Mn(II)-catalyzed oscillating chemical reaction. Under optimum conditions, a linear
relationship existed between the changes of oscillating period or amplitude and the negative of logarithm
of SNA concentration in the range of 4.27 × 10−8 mol ·L−1 ∼ 7.41 × 10−6 mol ·L−1 (RSD, 0.85%) and
9.33 × 10−8 mol ·L−1 ∼ 3.02 × 10−6 mol ·L−1 (RSD, 1.08%), respectively. The lower limit of detection
was found to be 2.69 × 10−8 mol ·L−1 and 6.03 × 10−8 mol ·L−1 , respectively.
c Versita Warsaw and Springer-Verlag Berlin Heidelberg. All rights reserved.
Keywords: Sulfanilamide; Mn(II)-catalysed oscillating chemical reaction, analyte pulse perturbation
technique; continuous-flow stirred tank
1
Introduction
Sulfa-drugs represent a group of compounds discovered in a conscious search for antibiotics. They inhibit bacteria by preventing the synthesis of folic acid, a vitamin that is
essential to growth. Although some sulfa-drugs have been replaced by newer antibacterial
drug, sulfanilamide (SNA) is still used today in developing countries due to the drug’s
affordability. Thereby, sulfanilamide analysis continues to be an important objective.
The commonly used methods for the determination of sulfanilamide are HPLC [1] and
∗
E-mail: [email protected]
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FIA [2] techniques that are selective and sensitive. Unfortunately, these methods also
require expensive equipment.
Compared to instrumental analysis, a oscillating chemical reaction has numerous advantages as an analytical tool – it is easy to set-up, simple to operate, linear over a wide
range range (ca. 10−7 to 10−3 mol·L−1 ), and is sensitive (ca. 10−6 to 10−8 mol·L−1 ).
Due to these characteristics, more and more analysts are adopting this technique [3, 4].
Moreover, the well-know FKN mechanism [5] and Talyor’s theoretical analysis for the B-Z
oscillating chemical reaction [6] promoted further study of this technique. The combination of analyte pulse perturbation technique (APP) [7] and continuous-flow stirred tank
reactor (CSTR) established a milestone in the analytical application of B-Z oscillating
chemical reaction [8, 9]. Since then, the determination of inorganic [10–13] and organic
[14–17] substances has been extensively studied.
In the present paper, a convenient and sensitive method for determination of sulfanilamide was reported based on the Mn(II)-catalyzed oscillating chemical reaction.
2
Experimental
2.1 Reagents
All chemicals were of analytical grade and all solutions were prepared using doubly
distilled-deionized water.
Postassium bromate, malonic acid (MA), and Mn(II) ion were separately prepared
with 1.0 mol × L−1 sulfuric acid solution sulfuric acid solution.
0.01 M of sulfanilamide solution was prepared in distilled-deionized water and stored
in refrigerator at 5 ◦ C. The lower concentrations were prepared immediately prior to use.
2.2 Apparatus
Studies were carried out within a 50 ml reactor wrapped in a water recirculation jacket.
Reactants were distributed to the CSTR and products removed from it using a Model
LEAD-1(Baoding Longer Precision Pump Co. Ltd.) with four-channel peristaltic pump,
in which three were used to feed reactants solutions, and the fourth was used to maintain
a constant reaction volume (see Fig. 1). The pump allowed the instantaneous selection
of different flow rate as needed. A Model CS 501 thermostat with an accuracy ±0.1◦ C
(Shanghai Yangguang Experimental Instrumental Factory) and a Model ML-902 magnetic
stirrer (Shanghai Pujiang Analytical Instrumental Factory) were used to maintain the
constant temperature. An electrochemical analytical instrument with Model CHI-832
(CHI, USA) was used to record the potential oscillation with an accuracy ±0.1 mV, which
were monitored by a platinum electrode (Rex, 213, China) and an Hg|Hg2 SO4 |K2 SO4
reference (Rex, 217, China). Signals were recorded as a function of time at intervals of
0.1 s. A micro-syringe was also used in the experiment for injecting different amounts of
sulfanilamide samples.
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2.3 Procedure
A mixed solution containing 0.260 mol·L−1 malonic acid, 1.0 mol·L−1 sulfuric acid and
6.00×10−3 mol·L−1 of Mn(II) was first placed into CSTR. Then, the indicator and reference electrodes were immersed in the mixture solution. The mixture was stirred well
and kept the temperature constant. After adding 0.195 mol·L−1 of potassium bromate,
the computer was immediately started to record all signals. Meanwhile, three channels
of peristaltic pump were started to supply the reactants at a rate of 1.4 mL·min−1 . The
system evolved gradually to constant oscillating amplitude and period. Once a regular
oscillating profile appeared, the analyte was injected to perturb the profile.
MnSO4 + H2SO4
KBrO3 + H2SO4
CH2(COOH)2 +H2SO4
Fig. 1 Experimental set-up for the determination of sulfanilamide based on Mn(II)-BrO−
3CH2 (COOH)2 -H2 SO4 oscillating regime.
3
Results and discussion
The Mn(II)-catalyzed oscillating system in a strong acid medium exhibits periodic changes
in the concentration of Mn(II) and Br− that reflect cyclic changes in color and potential .
The color of the solution changes from pink at the maximum point of the cyclic profile to
clear at the minimum point. Adding a trace amount of SNA perturbed the regular profile,
implying that the SNA reacts with some of the components in the oscillating system.
Because the changes both period and amplitude are proportional to the concentration of
SNA, and the oscillating profile can be recovered quickly, thus, these characteristics will
be able to use in determination.
In the open system, the first experiment was carried out in the absence of SNA in order
to ensure that the process was stable and repeatable. Subsequenty, adding SNA to the
regular oscillating system ensured that highest sensitivity and precision were obtained.
Since the addition of SNA changed the oscillating amplitude and period significantly,
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we defined A and Ao as the amplitudes after and before adding analyte and P and Po as
the periods after and before adding analyte. Then the values of ΔA and ΔP which were
used as analytical signals can be expressed as follows, respectively,
ΔA = Ao − A
(1)
ΔP = Po − P
(2)
Fig. 2 showed a typical oscillation profile in the absence and presence of SNA perturbations. The injection of SNA results in the decrease of amplitude and increase of period
of the next profile, which was proportional to the concentration of SNA. However, in order
to get an accurate and reproducible result, the addition of the analyte (or called injection
point) should be carefully tested. In general, the injection point should be chosen at the
maximum or minimum amplitude in the regular profile. Repeatly adding the analyte at
the same position ensures that the process is reproducible and precise.
Potential / v
0.72
0.66
0.60
0.54
100
200
300
400
500
600
Time / s
Fig. 2 Typical oscillation profile obtained in the absence and presence of SNA perturbation. Arrows indicate the addition of SNA.
For getting a regular oscillating profile, the flow rate of all reactants must be predetermined. In this study, the optimum rate was kept at 1.4 mL·min−1 . Temperature is
another parameter to effect on the oscillating profile, the range from 25 ◦ C to 40 ◦ C has
been examined and 35 ◦ C was determined to be a suitable temperature.
3.1 Influence of experimental variables on determination of sulfanilamide
Since the B-Z reactions take place in an acidic medium, the sulfuric acid concentration
was examined at first. The results demonstrate that increasing the concentration of
sulfuric acid up to 1.00 mol·L−1 shortens the oscillation period (no change was observed
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585
at concentrations greater than 1.00 mol·L−1 ). Thus, 1.00 mol·L−1 was adopted as optimal
sulfuric acid concentration (see Fig. 3A).
Fig. 3B demonstrates that as the potassium bromate concentration was adjusted
from 0.050 mol·L−1 to 0.450 mol·L−1 , the perturbation peaked at 0.195 mol·L−1 , and
then decreased as the potassium bromate was further increased. Thus, 0.195 mol·L−1 of
potassium bromate was chosen as the optimum concentration.
The concentration of malonic acid in the CSTR was studied over the range from
0.160 mol·L−1 to 0.300 mol·L−1 . The results demonstrated that the response of perturbation reached the maximum when the malonic acid concentration was 0.260 mol·L−1as
illustrated in Fig. 3C. A concentration of 0.260 mol·L−1 was finally adopted.
Raising manganese(II) concentration from 3.00×10−3 mol·L−1 to 9.00×10−3 mol·L−1
resulted in a longer period and a larger amplitude. The response to the SNA perturbation showed that the sensitivity of ΔA and ΔP gave rise to maximum when Mn(II)
concentration was 6.00×10 mol·L−1 (Fig. 3D).
3.2 Approach to determination of sulfanilamide
The perturbation to the oscillating system by injecting 0.2 ml of various concentrations
of SNA under the optimal conditions selected above caused changes in the oscillation
amplitude and period that was quantitatively related to the analyte concentration (see
Fig. 4). Therefore, the response to the SNA perturbation could be evaluated by employing
two oscillation parameters, namely (A) the decrease of amplitude and, (B) the increase
of period for the oscillating profile after injecting sample.
The limit of detection (LOD) was calculated as the amount of analyte yielding signal
equal to three times the standard deviation of the oscillation period in the absence of perturbation (n=25), and the precision was expressed as relative standard deviation (RSD)
within the dynamic range. The calibration curves obey the following linear regression
equation:
(3)
ΔP (s) = (81.7 ± 0.9) + (10.9 ± 0.15) lg CSN A
ΔA(mv) = (151 ± 3) + (20.9 ± 0.5) lg CSN A
(4)
A comparison of the two linear relationships as can be seen in Table 1. Although
both of them performed well in the determination of SNA, the parameter ΔP features a
higher precision, a lower determination limit and a wider dynamic range, thus ΔP was
selected as the measurement parameter for subsequent experiments.
It is well known that oscillating chemical reactions are sensitive to inpurities. Therefore, the effect of some of common inorganic ions and organic compounds on this technique were investigated. Generally, the inorganic ions and organic compounds with small
molecular weight had little influence on the analysis in acidic medium; Additionally, common sulfonamides in clinical practice, such as sulfanilamide (SNA), sulfadimidine (SDD),
sulfamethoxazole (SMZ), sulfadiazine (SDZ) and trimethoprim (TMP), cannot dissolve
in water, and are not expected to influence the analysis of SNA.
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19
20
18.5
16
17
26
24
'A / mv
22
'P / s
'A / mv
'T
'A
B
16
18.0
15
17.5
12
20
8
18
16
4
14
'P / s
18
19.0
'T
'A
A
14
0.6
0.8
1.0
1.2
1.4
0
0.0
17.0
0.1
0.2
'A / mv
20
16
44
24
20
12
16
0.28
36
32
30
28
24
24
12
4
0.32
2
48
42
36
8
0.24
0.5
'T
'A
D
40
'A / mv
'T
'A
C
'P / s
24
0.20
0.4
C (KBrO3) / M
C(H2SO4) / M
0.16
0.3
'P / s
13
3
4
5
6
7
8
9
18
10
C(MnSO4) / M
C(CH2(COOH)2) / M
Fig. 3 Influence of the concentrations of H2 SO4 (A), KBrO3 (B), CH2 (COOH)2 (C),
and MnSO4 (D) on the sulfanilamide-perturbed oscillating system (the symbol • refers
to amplitude change and refers to period change). Experimental conditions: T = 35
◦
C, overall flow rate 1.4 ml·min−1 , [SNA] = 0.750 µmol; (A) 6.00×10−3 mol·L−1 MnSO4 ,
0.195 mol·L−1 KBrO3 , 0.260 mol·L−1CH2 (COOH)2 ; (B) 1.00 mol·L−1 H2 SO4 , 6.00×10−3
mol·L−1 MnSO4 , 0.260 mol·L−1 CH2 (COOH)2 ; (C) 1.00 mol·L−1H2 SO4 , 6.00×10−3
mol·L−1 MnSO4 , 0.195 mol·L−1 KBrO3 ; (D) 1.00 mol·L−1 H2 SO4 , 0.260 mol·L−1
CH2 (COOH)2 , 0.195 mol·L−1 KBrO3 .
Table 1 Determination of sulfanilamide concentration with the proposed method.
Parameter
ΔP
ΔA
Linear range / M
determination limit / M
Precision (RSD), %
coefficient
4.26 × 10−8 ∼ 7.41 × 10−6
2.69 × 10−8
0.85
0.9981,
(n = 15)
9.33 × 10−8 ∼ 3.02 × 10−6
6.03 × 10−8
1.08
0.9978,
(n = 12)
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40
25
(A)
(B)
30
20
'A / mv
'P / s
15
10
20
10
5
0
0
5.0
5.5
6.0
6.5
7.0
7.5
5.6
6.0
-logCSM
6.4
6.8
7.2
-logCSM
Fig. 4 Calibration curve of changes in period (A) and in amplitude (B) versus the negative
of logarithm of sulfanilamide concentration.
4
Sample analysis
A known content of sulfonamide tablets (Biochemical Pharmaceutical Co. Ltd, Jinzhou,
China) was analyzed again to validate this method. Using the given sample as standard,
a working solution of 7.90 × 10−5 mol·L−1 SNA was prepared. Then, using the standard
addition to evaluate the proposed method, results are listed in Table 2.
Table 2 Determination of sulfaniliamide concentatration in sample solutions.
1
2
3
4
5
5
Continents original / M
Added / M
Total found / M
Recovery (%)
7.90×10−7
7.90×10−7
7.90×10−7
7.90×10−7
7.90×10−7
0
1.00×10−6
2.00×10−6
3.00×10−6
4.00×10−6
7.85×10−7
1.78×10−6
2.81×10−6
2.80×10−6
2.82×10−6
99.4
98.7
103
101
104
Conclusion
Sulfanilamide (SNA) is a eurytropic antibiotic, which can inhibit bacteria by preventing
the synthesis of folic acid, which is essential to their growth. Since SNA is still used today
in developing countries, a simple and rapid method is required for the routine analysis
in hospitals. The proposed method meets this need. This method, offers a largely linear
range (ca. 10−8 ∼ 10−6 mol·L−1) and a lower detection limit (ca. 10−8 mol·L−1 ). As an
analytical method, oscillating chemical reactions should be further invetigated.
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Acknowledgment
This work was supported in part by the Project of International Cooperation between
China and Ukraine (043-05), the National Natural Science Foundation (20475044) and
the Invention Project of Science & Technology (KJCXGC-01, NWNU), China.
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