use of basic reagents in test methods of analysis with ... and their applications in chemical test methods. ... The following organic reagents were studied: Mala-.
ISSN 1061-9348, Journal of Analytical Chemistry, 2008, Vol. 63, No. 3, pp. 297–299. © Pleiades Publishing, Ltd., 2007. Original Russian Text © V.G. Amelin, 2008, published in Zhurnal Analiticheskoi Khimii, 2008, Vol. 63, No. 3, pp. 327–329.
ARTICLES
Artificial and Natural Fiber Fabrics with Immobilized Di- and Triaminotriarylmethane Reagents in Chemical Test Methods V. G. Amelin Department of Chemistry and Ecology, Vladimir State University, ul. Gor’kogo 87, Vladimir, 600000 Russia Received September 28, 2006; in final form, January 30, 2007
Abstract—The potentials of fabrics made of artificial and natural fibers as supports for the di- and triaminotriarylmethane reagents were shown for their possible use in chemical test methods. Malachite Green, Brilliant Green, Methyl Violet, Crystal Violet, and Parafuchsine were immobilized on viscose, calico, coarse calico, and a mixed fabric. The reagent retention was 70–90%. The indicator fabrics are resistant to strong acids and alkalies and can be used for the test determination of 0.01–10 mg/L of phosphates, 1–80 mg/L of silicates, 0.01– 8 mg/L of dissolved oxygen, biological oxygen demand for 5 days (BOD5), 0.5–10 mg/L of formaldehyde, and 0.1–10 mg/L of anionic surfactants. The analysis time was 10–15 min. The relative standard deviation did not exceed 30%. DOI: 10.1134/S1061934808030192
Di- and triaminotriarylmethane reagents are used for the extraction–photometric determination of – – 2– – – – Au Cl 4 , Ga Cl 4 , Os Cl 6 , Ta F 6 , BF 4 , Sb Cl 6 , and other anions [1]. These reactions occur in strongly acidic media; the maximum absorbances the associates formed in an organic phase virtually coincide with those in aqueous solutions. These factors prohibit the use of basic reagents in test methods of analysis with indicator papers, because paper is unstable in strongly acidic or alkaline solutions. The use of Malachite Green immobilized on a thin layer of silica gel was studied for the determination of gold(III), acids, and alkalis [2]. The goal of this work was to study the possibility of using fabrics made of artificial and natural fibers as supports for the di- and triaminotriarylmethane reagents and their applications in chemical test methods. EXPERIMENTAL We used viscose (GOST (State Standard) 20272-83, Russia), calico (GOST (State Standard) 29298-92, Russia), viscose and cotton blend (50% each) (GOST (State Standard) 20272-96) and ashless filter paper (TU (Specification) 6-09-1678-95). The following organic reagents were studied: Malachite Green, Brilliant Green, Methyl Violet, Crystal Violet, and acid Parafuchsine. Adsorption immobilization of the reagents on fabrics was performed by soaking them in the reagent solutions (5–10 min) with further drying. We used 1 mg/mL standard solutions of phosphates (GSO (State Reference Sample) 7791-2000), anionic
surfactants based on sodium dodecyl sulfate (GSO (State Reference Sample) 7348-96), silicates (GSO (State Reference Sample) 8212-2002), and formaldehyde (GSO (State Reference Sample) 7347-96). Working solutions of a certain concentration were prepared by diluting the stock standard solutions with distilled water on the day of experiment. Truncated cones of the test unit were made of lowpressure polyethylene or polypropylene. To pass a certain volume of the solution (25 mL) under study through the test unit, we used a single-use Luer-lock injection syringe with a rubber cuff. The methods for preparation and use of the test strips and test units are described in [3]. The acidity of the solutions was adjusted by acetate– ammonium buffer solutions, and pH was measured by an I-130 potentiometer with a glass–silver chloride electrode system. The absorption spectra of the reagents immobilized on fabric were recorded using a SF-46 spectrophotometer against the samples free of an immobilized reagent. The absorbance of these matrices was measured after wetting them with solutions with a given acidity and pressing them between transparent glasses. To determine the reagent retention, the fabrics with immobilized reagents was placed in the solution with a given acidity, the solution was stirred for 3–5 min, and the absorbance of the fabric was measured. Retention R (%) was calculated by the equation R = (A/A0) × 100%, where A was the absorbance of the fabric supports after the reagent was washed out, and A0 was the absorbance
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of the fabric supports wetted with solutions of the same acidity. The absorbance was measured relative to the fabric not treated with the reagents, wetted with distilled water, and pressed between transparent glasses. RESULTS AND DISCUSSION Immobilization of the reagents. The retention of all of the studied reagents was higher on cellulose fabrics (70–90%) than on paper (40–50%), and it was almost independent on the solution pH. The retention on artificial fabrics was higher than on natural ones because of disorderly cross-linked molecules of artificial cellulose, unlike the compactly packed, long chains of natural cellulose [4]. Bathochromic shifts of the absorption bands of the reagents on matrices were also observed with respect to their absorption in solutions; the higher the retention of the reagents, the larger the bathochromic shift. For example, in the case of the reagents immobilized on paper, such a shift was 2–6 nm, while for fabrics, 10–20 nm. In the procedures proposed below, viscose fabric was used as a matrix for the retention of the reagents and reaction products. Determination of oxygen, BOD5 , and formaldehyde. Di- and triaminotriarylmethane compounds can be discolored by sodium sulfite with the formation of leucosulfonic compounds SO3Na R2
R3 R2 C
R1
Na2SO3
R3 C
R1
Parafuchsine (R1 , R2 , R3 = –NH2), Malachite Green (R1 = –H; R2 , R3 = –N(CH3)2), Methyl Violet (R1 = −NHCH3; R2 , R3 = –N(CH3)2), and Crystal Violet (R1 , R2 , R3 = –N(CH3)2). The leucosulfonic compounds are adsorbed on fabrics in a similar way as the initial reagents; these fabrics keep their properties for no less than 2 years. Aldehydes and oxygen reduce the quinoid structure of the reagents and, consequently, their color by binding sodium sulfite. The best results on the determination of formaldehyde were obtained on the viscose fabric with Parafuchsine. In distinction to Malachite Green, Brilliant Green, Methyl Violet, and Crystal Violet, Parafuchsine provides the indicator fabric with a more intense color (red) and a higher sensitivity of determination. The analytical range for formaldehyde was 0.5– 100 mg/L. The determination of formaldehyde was not
affected by the presence in the solution of 500 mg/L of ethanol, 100 mg/L of phenol, 10 mg/L of acetone, and 1 mg/L of oxygen. The interfering effect of oxygen was eliminated by the addition to the solution under study of the reagent paper with sodium sulfite. The fabric with immobilized Malachite Green is suitable to determine dissolved oxygen. In the presence of 0.01–8 mg/L of oxygen, the reaction area of the discolored indicator fabric was colored turquoise. To determine BOD5 , the water sample under analysis was saturated with oxygen by bubbling air through the sample for 3–5 min. The oxygen concentration was determined in one portion of the sample; another portion was pumped into a 25-mL syringe, tightly sealed with a cap, and left in a dark place at 18–20°C for five days. After five days, the test unit with the indicator fabric was connected to the syringe, and the analyzed sample was passed through the unit at a rate of 1–2 drops per second. The color of the indicator fabric was compared to a reference color scale, and the oxygen concentration was determined. BOD5 was calculated by the difference between the oxygen concentration before and after keeping the water sample for 5 days. Determination of phosphates and silicates. The determination is based on the formation of ion associates of basic dyes with molybdophosphoric or molybdosilicic heteropolyacids. The formed associates have a color similar to the color of the initial reagents and are stable in an acidic medium, where the reagents are discolored. Therefore, the determination of phosphates (silicates) was performed as follows. The reagent paper soaked with ammonium molybdate and tartaric acid (masking of silicates) or oxalic acid (masking of phosphates) was placed in a 25-mL aliquot portion of the analyzed solution; the solution was mixed for 3–5 min. The obtained solution was pumped in a syringe and passed through the test unit with the indicator fabric soaked with Malachite Green at a rate of 1–2 drops per second. Then, one drop of a 2 M HCl solution was placed on the reaction area, and the obtained color was compared to the reference color scale. The analytical range for phosphates was 0.01–10 mg/L, while for silicates, 1–80 mg/L. The presence of 100 mg/L of silicates or phosphates in the solution did not interfere with the determination of each others. Determination of anionic surfactants. In an acidic medium, anionic surfactants form with basic reagents ion associates. Malachite Green and Crystal Violet are protonated in an acidic medium (pH 0–2), and their color changes from turquoise (Malachite Green) or blue (Crystal Violet) to yellow or green, respectively. When anionic surfactants are added, the initial color of the reagents returns (in some cases, a small bathochromic shift of the absorption bands can be observed). Crystal Violet is suitable for the determination of anionic surfactants (by the example of sodium dodecyl sulfate). The analytical range for the surfactant was 0.1–10 mg/L, when 20 mL of the analyzed solution was
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ARTIFICIAL AND NATURAL FIBER FABRICS
The table illustrates the use of the developed test systems in the analysis of natural waters. The following composition of water was determined by the photometric and volumetric methods: total hardness, 4.5 mM; total alkalinity, 1.8 mM; sulfates, 15 mg/L; chlorides, 10 mg/L; nitrates, 0.08 mg/L; iron, 0.2 mg/L; molybdenum, 0.04 mg/L; zinc, 0.06 mg/L; copper, 0.001 mg/L. The relative standard deviation of the analysis results was less than 0.3; the analysis time was 10– 15 min.
Analysis of natural waters (n = 3, P = 0.95) Analyte O2 O2 (boiler water) BOD5 Formaldehyde (added) Phosphates Silicates Sodium dodecyl sulfate (added)
Found Found by the RSD, by the photometric test method, % method, mg/L mg/L 6.0 0.02 1.6 3.0
5±1 0.03 ± 0.01 2.0 ± 0.5 4±1
18 32 19 18
0.15 8.0 5.0
0.20 ± 0.05 7±2 4±1
26 20 16
ACKNOLEDGMENTS This work was supported by the Russian Foundation for Basic Research, project no. 05-03-32024.
passed through the test unit. In the experiment, pH 1 was created by adding a 2 M solution of hydrochloric acid. At this pH value, Crystal Violet was in the form of diprotonated cation (two maxima were observed in the absorption spectrum: (1) at 450 and (2) 610 nm). In the interaction with the anionic surfactant, the ion associate was formed with an absorption maximum at 640 nm. The determination of anionic surfactants was not affected by the presence of 100 mg/L of nonionic and cationic surfactants, nitrates, sulfates, phosphates, chlorides, and alkali metal ions; 50 mg/L of alkalineearth metal ions; and 5 mg/L of Fe(III), Cu(II), Zn and Al.
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REFERENCES 1. Pilipenko, A.T. and Tananaiko, M.M., Raznoligandnye i raznometall’nye kompleksy i ikh primenenie v analiticheskoi khimii (Heteroligand and Heterometallic Complexes and Their Use in Analytical Chemistry), Moscow: Khimiya, 1983. 2. Amelin, V.G. and Tret’yakov, A.V., Zh. Anal. Khim., 2006, vol. 61, no. 2, p. 202. 3. Amelin, V.G., Zh. Anal. Khim., 1998, vol. 53, no. 9, p. 958 [J. Anal. Chem. (Engl. Transl.), vol. 53, no. 9, p. 840]. 4. Klenkova, N.I., Struktura i reaktsionnaya sposobnost’ tsellulozy (The Structure and Reactivity of Cellulose), Leningrad: Nauka, 1976.
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