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      Screen-Printed Carbon Electrodes Modified with Cobalt Phthalocyanine for Selective Sulfur Detection in Cosmetic Products

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          Abstract

          Cobalt phthalocyanine (CoPc) films were deposited on the surface of a screen-printed carbon electrode using a simple drop coating method. The cyclic voltammogram of the resulting CoPc modified screen-printed electrode (CoPc/SPE) prepared under optimum conditions shows a well-behaved redox couple due to the (Co I/Co II) system. The CoPc/SPE surface demonstrates excellent electrochemical activity towards the oxidation of sulfur in a 0.01 mol·L −1 NaOH. A linear calibration curve with the detection limit (D L, S/N = 3) of 0.325 mg·L −1 was achieved by CoPc/SPE coupled with flow injection analysis of the sulfur concentration ranging from 4 to 1120 mg·L −1. The precision of the system response was evaluated (3.60% and 3.52% RSD for 12 repeated injections), in the range of 64 and 480 mg·L −1 sulfur. The applicability of the method was successfully demonstrated in a real sample analysis of sulfur in anti-acne creams, and good recovery was obtained. The CoPc/SPE displayed several advantages in sulfur determination including easy fabrication, high stability, and low cost.

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          Direct electrochemical determination of carbaryl using a multi-walled carbon nanotube/cobalt phthalocyanine modified electrode.

          The electrochemical detection of carbaryl at low potentials, in order to avoid matrix interferences, is an important challenge. This study describes the development, electrochemical characterization and utilization of a glassy carbon (GC) electrode modified with multi-wall carbon nanotubes (MWCNT) plus cobalt phthalocyanine (CoPc) for the quantitative determination of carbaryl in natural waters. The surface morphology was examined by scanning electron microscopy, enhanced sensitivity was observed with respect to bare glassy carbon and electrocatalytic effects reduced the oxidation potential to +0.80 V vs. SCE in acetate buffer solution at pH 4.0. Electrochemical impedance spectroscopy was used to estimate the rate constant of the oxidation process and square-wave voltammetry to investigate the effect of electrolyte pH. Square-wave voltammetry in acetate buffer solution at pH 4.0, allowed the development of a method to determine carbaryl, without any previous step of extraction, clean-up, or derivatization, in the range of 0.33-6.61 micromol L(-1), with a detection limit of 5.46+/-0.02 nmol L(-1) (1.09+/-0.02 microg L(-1)) in water. Natural water samples spiked with carbaryl and without any purification step were successfully analyzed by the standard addition method using the GC/MWCNT/CoPc film electrode.
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            Optimization of ultrasound assisted-emulsification-dispersive liquid-liquid microextraction by experimental design methodologies for the determination of sulfur compounds in wines by gas chromatography-mass spectrometry.

            A new method was developed for analyzing sulfur compounds in the aroma of white wines using ultrasound assisted-emulsification-dispersive liquid-liquid microextraction coupled with gas chromatography-mass spectrometry detection. In the present work, the analytical method for simultaneous determination of seven sulfur compounds (methylmercaptoacetate, methyl(methylthio)acetate, 2-methylthioethanol, 3-methylthiopropanol, 3-methylthiohexanol, 4-methylthio-4-methyl-2-pentanone and hexanethiol) is reported. Parameters that affect the efficiency of the methodology such as extracting and dispersing solvents, sample volume, ion strength, cavitation time and centrifugation time were investigated using a fractionated factorial 2(6-1) (R=V) screening design. Then, the factors presenting significant positive effects on the analytical response (extracting volume, ion strength, cavitation time and centrifugation time) were considered in a further central composite design to optimize the operational conditions for the ultrasound assisted-emulsification-dispersive liquid-liquid microextraction procedure. Additionally, multiple response simultaneous optimization by using the desirability function was used to find the optimum experimental conditions. The best results were obtained using pH sample 4.25, extractant volume 150μL, ionic strength 8.75% NaCl, cavitation time 20s and centrifugation time 50s. The use of the optimized ultrasound assisted-emulsification-dispersive liquid-liquid microextraction technique allowed to obtain the best extraction results with the minimum interference from other substances from the matrix, and it allowed to quantify the analytes in white wine samples by calibration graphs. Recoveries ranging from 91.99% to 125.87% for all sulfur compounds proved the accuracy of the proposed method in white wine samples. Method detection limits were in the range of 0.36-1.67ngmL(-1) and limits of quantitation were between 0.63 and 3.02ngmL(-1) for sulfur compounds in white wine samples. The proposed methodology was successfully applied for the determination concentrations of sulfur compounds in different commercial Chardonnay wine samples from Mendoza, Argentine. Copyright © 2010 Elsevier B.V. All rights reserved.
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              The use of sulfur in dermatology.

              Sulfur has antifungal, antibacterial, and keratolytic activity. In the past, its use was widespread in dermatological disorders such as acne vulgaris, rosacea, seborrheic dermatitis, dandruff, pityriasis versicolor, scabies, and warts. Adverse events associated with topically applied sulfur are rare and mainly involve mild application site reactions. Sulfur, used alone or in combination with agents such as sodium sulfacetamide or salicylic acid, has demonstrated efficacy in the treatment of many dermatological conditions.
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                Author and article information

                Journal
                Int J Mol Sci
                ijms
                International Journal of Molecular Sciences
                Molecular Diversity Preservation International (MDPI)
                1422-0067
                2011
                09 June 2011
                : 12
                : 6
                : 3810-3820
                Affiliations
                [1 ] Department of Cosmetic Science, Providence University 200 Chungchi Rd., Taichung 43301, Taiwan; E-Mails: pychen2@ 123456pu.edu.tw (P.-Y.C.); s9624065@ 123456pu.edu.tw (M.-C.C.); tftsay@ 123456pu.edu.tw (F.-J.T.); nfchang@ 123456pu.edu.tw (N.-F.C.)
                [2 ] Department of Safety, Health and Environmental Engineering, Hung Kuang University, 34 Chungchi Rd., Taichung 43302, Taiwan; E-Mail: andyluo@ 123456hk.edu.tw
                Author notes
                [* ]Author to whom correspondence should be addressed; E-Mail: yingshih@ 123456pu.edu.tw ; Tel.: +886-4-26328001; Fax: +886-4-26311167.
                Article
                ijms-12-03810
                10.3390/ijms12063810
                3131592
                21747708
                a1e2ff3a-0aa6-40d5-ac9b-1c5de6451dc4
                © 2011 by the authors; licensee Molecular Diversity Preservation International, Basel, Switzerland.

                This article is an open-access article distributed under the terms and conditions of the Creative Commons Attribution license ( http://creativecommons.org/licenses/by/3.0/).

                History
                : 13 April 2011
                : 31 May 2011
                : 02 June 2011
                Categories
                Article

                Molecular biology
                cobalt phthalocyanine,sulfur,screen-printed carbon electrode,cosmetics
                Molecular biology
                cobalt phthalocyanine, sulfur, screen-printed carbon electrode, cosmetics

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