Spectrophotometric determination of triclosan in personal care products

Article abstract of DOI:10.1016/j.saa.2009.04.007

A spectrophotometric method for the determination of triclosan in personal care products was proposed. It was based on the reaction of sodium nitrite with p-sulfanilic acid in an acidic medium to form diazonium ion, with which triclosan further formed an

Full text of DOI:10.1016/j.saa.2009.04.007

Spectrochimica Acta Part A 73 (2009) 854–857
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Spectrophotometric determination of triclosan in personal care products
Huihui Lua, Hongbing Mab, Guanhong Taoa,∗
a College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, Jiangsu 215123, China
b College of Life Sciences, Soochow University, Suzhou, Jiangsu 215123, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A spectrophotometric method for the determination of triclosan in personal care products was proposed.
It was based on the reaction of sodium nitrite with p-sulfanilic acid in an acidic medium to form diazo-
nium ion, with which triclosan further formed an azo compound in an alkaline medium. The resulting
yellow colored product has a maximum absorption at 452 nm. A good linear relationship (r = 0.9999) was
obtained in the range of 0–30 mg L−1 triclosan. A detection limit of 0.079 g L−1 was achieved and the rela-
tive standard deviation was 0.24% (n = 11) at 14 mg L−1 triclosan. The proposed method has been applied
to the analyses of triclosan in several personal care products and the results were in good agreement with
those obtained by high-performance liquid chromatography.
Received 3 December 2008
Received in revised form 28 March 2009
Accepted 15 April 2009
Keywords:
Triclosan
Spectrophotometry
Determination
Diazotization
© 2009 Elsevier B.V. All rights reserved.
Personal care products
1. Introduction
chromatography–mass spectrometry (LC–MS) [16–18]. Although
GC–MS and LC–MS enable the determination of triclosan at very
Triclosan, 2,4,4ꢀ-trichloro-2ꢀ-hydroxydiphenyl ether, or com-
mercially known as Irgason DP 300, is a nonionic, broad spectrum
antimicrobic agent. It is added to a variety of personal care prod-
ucts, such as shampoo, handwash, and toothpaste. Because it is a
stable and lipophilic compound, large consumption of triclosan has
also provoked a great deal of concern over its environmental fate,
as triclosan has been widely found in river water, lake water, sed-
iments, fish, and even in human milk [1–4]. It was also reported
that chloroform and chlorinated organics could be formed by the
reaction of triclosan with free chlorine in chlorinated tap water
[5,6]. Although TCS has not been reported to be toxic to mam-
mals, it is toxic to aquatic organisms, fish, and some algae species
[7]. As a consequence, the restriction of triclosan usage in personal
care products has been enacted [8,9]. According to the European
Economic Community Council directive 76/768 (Annex VI and sub-
sequent amendments) [8], and Chinese Hygienic Standard [9], its
use is permitted at a maximum concentration of 0.3% (w/w). There-
fore, analytical methods able to perform selective and sensitive
determination of triclosan are necessary to verify the adherence
of the finished products to hygienic legislation.
low concentration (ng mL−1), these techniques require expensive
instrumentation, which might not be available in many labora-
tories. Simple methods based on chemiluminescence [19] and
electrochemistry [20,21] were proposed recently.
In the present paper, attempts were made to develop a simple,
rapid and practical method for the determination of triclosan in per-
sonal care products. Spectrophotometry was used, which was based
on the diazotization reaction between sodium nitrite, p-sulfanilic
acid and triclosan. To our best knowledge, no spectrophotomet-
ric method for the determination of triclosan has been reported
yet.
2. Experimental
2.1. Instrumentation
An SP-2000 spectrophotometer (Spectrum Instruments, Shang-
hai, China) was used for spectrometric measurements. Sample cells
with a path length of 1 cm were used throughout the study.
A Waters liquid chromatography system, consisting of two
pumps (Model 510) and an ultra-violet absorbance detector (Model
486), was used for the verification tests. Waters Baseline chro-
matographic software was used for data acquisition and analysis.
Chromatographic separation was performed with a Nova Pak C18
column (15 cm × 0.39 cm ID, 4 ␮m particle size).
General methods for determination of triclosan include
reversed phase high performance liquid chromatography with
UV [10,11], diode array [12] and voltammetric detection [13], gas
chromatography–mass spectrometry (GC–MS) [14,15], and liquid
An ultrasonic cleaner (KQ218, Kunshan Ultrasonic, China) was
used for the extraction of samples. The cleaner was operated at a
power of 100 W and a frequency of 40 KHz.
∗
Corresponding author. Fax: +86 512 65880089.
E-mail address: taogh@suda.edu.cn (G. Tao).
1386-1425/$ – see front matter © 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2009.04.007

H. Lu et al. / Spectrochimica Acta Part A 73 (2009) 854–857
855
Fig. 1. Proposed reaction mechanism of chromogenic species by means of diazotization reaction.
2.2. Reagents and standards
sample was extracted for 5 min in the ultrasonic cleaner. The
extracted sample was transferred into a centrifugal tube and cen-
trifuged for 5 min at 3000 rpm. The supernatant fluid was diluted
to 25 mL and was ready for the spectrophotometric analysis.
All chemicals used were of analytical-reagent grade, which
were purchased from Sinopharm Group, Shanghai, China except
for triclosan which was purchased from Alfa Aesar. All solutions
were prepared with sub-boiling distilled deionized water. Attention
should be paid that sodium nitrite used in the spectrophotomet-
ric reaction is a high toxic substance with a rat oral acute toxicity
(LD50) of 85 mg/kg. para-sulfanilic acid used has a low toxicity
(LD50 > 3200 mg/kg).
3. Results and discussion
3.1. The mechanism of chromogenic reactions
The proposed mechanism of the diazotization reaction is illus-
trated in Fig. 1.
The color of the final derivative was intense and stable yellow
which corresponding to the maximum absorption wavelength at
452 nm in the visible range. The reactions could take place rapidly
at room temperature and remain stable for at least 1 h.
A triclosan stock solution of 200 mg L−1 was prepared by dissolv-
ing 0.020 g triclosan in 20 mL of 0.01 mol L−1 NaOH and diluting to
100 mL with deionized water, which was stored in a refrigerator.
Working standard solutions were prepared daily by appropri-
ate dilution of the stock solution with deionized water. Sodium
nitrite stock solution with a concentration of 0.50 mol L−1 was pre-
pared by dissolving 3.45 g NaNO2 in 100 ml water, and diluted to
0.020 mol L−1 with water before use. para-sulfanilic acid solutions
were prepared by dissolving appropriate amount of p-sulfanilic
acid in 0.09 mol L−1 hydrochloric acid. An alkaline glycine buffer
solution (pH 11.93 at 25 ◦C) was prepared by mixing 92 mL of
0.1 mol L−1 glycine and 0.1 mol L−1 sodium chloride mixing solution
with 108 mL of 0.1 mol L−1 sodium hydroxide solution.
3.2. Optimization of reaction conditions
As shown in Fig. 1, the whole derivatization process could be
divided into two steps. First, sodium nitrite reacted with p-sulfanilic
acid to form a diazonium ion in an acidic medium. Second, under
a basic condition, the formed diazonium ion further reacted with
triclosan to form the final diazotization species for measurement.
Hydrochloric acid was chosen in the first step as the acidic
medium. The effect of hydrochloric acid concentrations on
the sensitivity of the method was studied over the range of
0.07–0.12 mol L−1. The results are shown in Fig. 2. 0.09 mol L−1 HCl
was chosen for the further study to achieve higher response.
2.3. Operating procedures
In a typical derivatization experiment, 1.4 mL of 0.020 mol L−1
nitrite solution, 1.0 mL of 0.25% p-sulfanilic acid solution contain-
ing 0.09 mol L−1 hydrochloric acid, 3.5 mL of triclosan standard or
sample solution, and 2.2 mL of glycine buffer solution were trans-
ferred subsequently into a 10 mL volumetric flask. The solutions in
the flask were mixed thoroughly before a new solution was added.
Finally, the solution was diluted with deionized water to the mark
of 10.00 mL volumetric flask before detection. A blank reagent solu-
tion was performed in the same manner without triclosan spiking.
Absorbance was measured at the maximum absorption wavelength
of 452 nm. All the experiments were consecutively studied in trip-
licate.
For the liquid chromatographic analysis, a standard method [9]
was adopted in this study. An isocratic mobile phase of methanol
and water (80:20, v/v) was used at a flow rate of 1.0 mL min−1. The
eluent was monitored with a UV detector at 282 nm and the chro-
matograph was recorded. 10 ␮L of pretreated sample solution after
filtrated with 0.45 ␮m membrane filter was injected.
2.4. Sample preparation
Samples including toothpaste, handwash gel and pubes disinfec-
tion solution were purchased from a local supermarket. About 0.15 g
of each sample was weighed and transferred into a 25 mL beaker.
10 mL of 0.01 mol L−1 sodium hydroxide solution were added. The
Fig. 2. Effect of HCl concentration on the sensitivity. The sample concentration was
14 mg L−1 triclosan. Other conditions are given in Section 2.

856
H. Lu et al. / Spectrochimica Acta Part A 73 (2009) 854–857
Fig. 3. Effect of NaNO2 concentration on the sensitivity. The sample concentration
Fig. 5. Effect of the amount of glycine buffer solution added on the sensitivity. The
was 14 mg L−1 triclosan. Other conditions are given in Section 2.
sample concentration was 14 mg L−1 triclosan. Other conditions are given in Section
2.
The effects of sodium nitrite and p-sulfanilic acid concentrations
on the sensitivity of the method were also investigated. The results
are shown in Figs. 3 and 4, respectively. The response increased
gradually with increase in both sodium nitrite and p-sulfanilic acid
concentrations and remained almost constant when their concen-
trations exceeded 0.015 mol L−1 and 0.20%, respectively. Therefore,
0.020 mol L−1 sodium nitrite and 0.25% p-sulfanilic acid were cho-
sen for the further study.
The effect of reaction temperature was investigated in this study
by immersing the test tubes in a temperature-controllable water
bath. There was no significant difference in terms of sensitivity
and reaction rate between the temperatures tested from 0 to 40 ◦C.
Therefore, room temperature was used.
3.3. Interference studies
In this study, two other anilines with strong electrophilic groups,
p-anisidine, and 2,4-dinitroaniline, were also investigated as the
diazonium-ion-forming reagent. Yet, p-sulfanilic acid was superior
to the anilines investigated in terms of sensitivity and stability of
the final chromogenic species.
In the second step as illustrated in Fig. 1, the azo compound for
the spectrophotometric measurement was formed under an alka-
line condition. The glycine buffer was chosen in this study to adjust
the acidity of reaction solution to alkaline and maintain at a sta-
ble pH since the first step of derivatization took place in the acidic
medium. The amount of buffer solution added played a critical role
on the system’s performance. As shown in Fig. 5, 2.2 mL of buffer
solution added yielded the highest response. Thus, it was used in
the present study.
The ingredients and inorganic ions commonly used in personal
care products were chosen for the interference studies. The results
shown in Table 1 indicate the general freedom from interferences.
However, experiment data showed that phenols including nitro-
phenol, chlorophenol, bisphenol A, and m-trihydroxybenzene may
generate positive interference. Yet these substances are generally
not used in personal care products. Some preservatives and fra-
grances used in personal care products, such as cinnamaldehyde,
methyl salicylate, eugenic acid and vamillic aldehyde, absorb near
452 nm [22–24], which may interfere the measurement. In addition,
p-sulfanilic acid used as chromogenic reagent in this study might
be oxidized under alkaline conditions to a product which absorbs
at 452 nm [25].
3.4. Analytical performance and its use for practical assays
The system was calibrated with a series of triclosan standards
having concentrations up to 30 mg L−1. Calibration graphs obeyed
the equation, Abs = −0.0018 + 0.0286 × Ctriclosan (n = 6, r = 0.9999,
SDy,x = .00171), where Abs represents absorbance and Ctriclosan is the
triclosan concentration in mg L−1. The molar absorptivity (ε) of the
proposed method was 8.27 × 103 L mol−1 cm−1 and the detection
Table 1
Effect of potential interferents on the recovery of triclosan measurements (14 mg/L).
Interferents
Concentration
(mg/L)
Recovery (%)
Glycerol, urea, polyethyleneglycol,
18,200
18,200
95–103
96–105
3−
propanediol, ethanol, C6H5O7
−
K+, Na+, Ca2+, Mg2+, Ba2+, Sr2+, NO3
,
−, SO4
2
F
−
Benzoate, NO2
7,000
1,400
700
95–103
98–104
99–102
96–103
PO43−, SDS
Formaldehyde, HPO42−, CO32−, SiO3
2−
−
Sn2+, Zn2+, H2PO4
280
Fig. 4. Effect of p-sulfanilic acid concentration on the sensitivity. The sample con-
centration was 14 mg L−1 triclosan. Other conditions are given in Section 2.
All results are averages of three measurements with 1–2% RSD.

H. Lu et al. / Spectrochimica Acta Part A 73 (2009) 854–857
857
Table 2
should be paid that some additives used in personal care products
may yield interference.
Analytical results of some personal care products and recovery tests by proposed
method and HPLCa.
No.
Sample
Measured concn. (mg/g)
Recovery by present
method (%)
Acknowledgements
Present method
HPLC method
The National Natural Science Foundation of China is thanked
for financial support (Project Nos. 20345006 and 20575043). The
authors are grateful to Dr. Jian Zhu and Mr. Chengrong Lu for their
valuable suggestions on the reaction mechanism.
1
2
3
4
5
Toothpaste 1
Toothpaste 2
Toothpaste 3
Toothpaste 4
Disinfection
solution
2.72 0.01
1.54 0.01
2.64 0.02
2.75 0.02
3.37 0.03
2.75 0.02
1.50 0.01
2.65 0.02
2.78 0.03
3.30 0.03
92.5
92.1
93.8
100.0
100.0
References
6
Handwash
0.195 0.01
0.201 0.01
94.0
a
The measurements were run in triplicate. For the recovery tests, 0.3–1.6 mg/g
[1] G.-G. Ying, R.S. Kookana, Environ. Int. 33 (2007) 199–205.
[2] A. Lindstrom, I.J. Buerge, T. Poiger, P. Bergvist, M.D. Muller, H. Buser, Environ.
Sci. Technol. 36 (2002) 2322–2329.
triclosan was spiked after the samples were extracted and diluted appropriately.
[3] H. Singer, S. Muller, C. Tixier, L. Pillonel, Environ. Sci. Technol. 36 (2002)
4998–5004.
[4] M. Adolfsson-Erici, M. Pettersson, J. Parkkonen, J. Sturve, Chemosphere 46
(2002) 1485–1489.
[5] E.M. Fiss, K.L. Rule, P.J. Vikesland, Environ. Sci. Technol. 41 (2007) 2387–2394.
[6] B.J. Vanderford, D.B. Mawhinney, F.L. Rosario-Ortiz, S.A. Snyder, Anal. Chem. 80
(2008) 4193–4199.
[7] D.R. Orvos, D.J. Versteeg, J. Inauen, M. Capdevielle, A. Rothenstein, V. Cunning-
ham, Environ. Toxicol. Chem. 21 (2002) 1338–1349.
[8] European Economic Community Council directive 76/768 EEC (Appendix VI
81976).
[9] Hygienic Standards for Cosmetics, Ministry of Health of the People’s Republic
of China, 2007.
[10] A. Piccoli, J. Fiori, V. Andrisno, M. Orioli, Il Farmaco 57 (2002) 362–372.
[11] A. Sanches-Silva, R. Sendon-Garcia, J. Lopez-Hernandez, P. Paseiro-Losada, J.
Sep. Sci. 28 (2005) 65–72.
[12] A.R.M. Silva, J.M.F. Nogueira, Talanta 74 (2008) 1498–1504.
[13] L.-H. Wang, S.-C. Chu, Chromatographia 60 (2004) 385–390.
[14] J.-L. Wu, N.P. Lam, D. Martens, A. Kettrup, Z. Cai, Talanta 72 (2007) 1650–1654.
[15] M.J. Gomez, A. Aguera, M. Mezcua, J. Hurtado, F. Mocholi, A.R. Fernandez-Alba,
Talanta 73 (2007) 314–320.
limit was 0.079 mg L−1, based on 3ꢀ of a blank solution (n = 11).
The relative standard deviation of the signals at a level of 14 mg L−1
triclosan was 0.24% (n = 11).
The practical feasibility of the proposed system was tested on
several personal care product samples. The results are shown in
Table 2 and recoveries of the spiked samples are generally sat-
isfactory. The accuracy of the proposed system was evaluated by
analyzing the samples with the high-performance liquid chro-
matographic method described in Section 2. A two-population
(independent) t-test was performed to evaluate the difference of
the results obtained by the two methods. A t-value of 0.00857 and
a p-values of 0.993 were obtained. Because the t-value is smaller
than 2.015 [T(5)0.05] and the p-value is greater than 0.05, the results
obtained are not significantly different statistically at the 95% confi-
dence interval. In another word, the results obtained by the present
method were in good agreement with those obtained with the chro-
matographic method.
[16] S. Chu, C.D. Metcalfe, J. Chromatogr. 1164 (2007) 212–218.
[17] J.B. Quintana, T. Reemtsma, Rapid Comm. Mass Spectrom. 18 (2004) 765–774.
[18] X. Ye, A.M. Bishop, L.L. Needham, A.M. Calafat, Anal. Chim. Acta 622 (2008)
150–156.
[19] S. Song, Q. Song, Z. Chen, Anal. Bioanal. Chem. 387 (2007) 2917–2922.
[20] M. Amiri, S. Shahrokhian, E. Psillakis, Frank Marken, Anal. Chim. Acta 593 (2007)
117–122.
4. Conclusion
[21] L. Vidal, A. Chisvert, A. Canals, E. Psillakis, A. Lapkin, F. Acosta, K.J. Edler, J.A.
Holdaway, F. Marken, Anal. Chim. Acta 616 (2008) 28–35.
[22] J. Cocchiara, C.S. Letizia, J. Lalko, A. Lapczynski, A.M. Api, Food Chem. Toxicol.
43 (2005) 867–923.
[23] A. Lapczynski, L. Jones, D. McGinty, C.S. Letizia, A.M. Api, Food Chem. Toxicol.
45 (2007) S428–S452.
[24] S.G. Wang, C. Mosley, G. Stewart, H. Yu, J. Photochem. Photobiol. Chem. 197
(2008) 34–39.
[25] S.A. Farokhi, S.T. Nandibewoor, Tetrahedron 59 (2003) 7595–7602.
A spectrophotometric method was developed and used success-
fully for the determination of triclosan in personal care products.
Comparing with those previously reported methods, it is simple,
rapid and reliable. These merits make it promising to be used in rou-
tine analysis applications, such as adherence verification of hygienic
legislation, and quality control of production line. Yet, due to the
inherent shortcomings of a spectrophotometric method, attention