Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy
Application of Micro-cloud point extraction for spectrophotometric determination of Malachite green, Crystal violet and Rhodamine B in aqueous samples
Graphical abstract
Introduction
Nowadays, synthetic dyes are extensively used in various industrial purposes, such as paper, leather, textile, food, cosmetic, and pharmaceutical industries. Every year thousands of tons of such dyes are continuously entering the ecosystem from these industries. Some of these dyes are hazardous in their nature and even the others which do not show immediate threat, can be dangerous if combined with other materials or if get along with other compounds in body of animals and humans [1]. As a result, monitoring of environmental samples for trace determination of organic dyes [2], [3], [4] and their removal [5], [6], [7], [8], [9], [10] had become very important in recent decades especially in water samples.
Malachite green (MG) and crystal violet (CV) (Fig. 1a and b) are cationic triphenylmethane dyes that are soluble in water. They have been widely used around the world as fungicide, parasiticide and antiseptic in the aquaculture. Since it has been reported [11] that like other triphenylmethane compounds, MG and CV may cause human carcinogenesis and mutagenesis [12], [13], [14], the use of MG and CV in aquaculture has raised serious concerns. Rhodamine B (Fig. 1c) is one of the mostly used fluorophore, laser dyes, and fluorescent analytical reagents [15], [16]. It is soluble in water, methanol and ethanol and is widely used as a colorant in textiles and foodstuffs and as a tracer dye within water to determine the rate and direction of flow and transport. Rhodamine B (RB) is toxic for humans and animals [17], [18]. Because of their low cost and high effectiveness, these harmful and toxic dyes are widely used in a lot of countries. Thus, it was considered worthwhile to make efforts to develop a simple method for the determination of Malachite green, crystal violet, and Rhodamine B in water and wastewater samples.
Due to the low concentration of dyes in water, applying a sample preparation/preconcentration step before introduction of sample to analytical instrument seems to be necessary. Many techniques have been developed for this purpose, including solvent extraction [19] solid phase extraction (SPE) [20], [21], molecularly imprinted solid-phase extraction [22], [23], [24], dispersive liquid-liquid microextraction (DLLME) [25], [26], [27], and cloud point extraction (CPE) [28], [29].
CPE is a simple and easy to operate extraction method. Since the first report of CPE in 1977 by Watanabe [30], it has become a popular technique for preconcentration and extraction of all kind of analytes including inorganic [31], [32], organic [33], and pharmaceutical [34], [35] analytes in various matrixes. The most featured character of CPE is utilization of a surfactant compound as an extractant phase instead of organic solvents. CPE consists of three simple steps [36]: adding surfactant to sample solution; putting the sample in water bath for formation of micelle by surfactant molecules (cloudy solution); and separating of enriched micellar phase from aqueous phase (usually with centrifugation). Like other methods, CPE has some drawbacks: it usually needs large volume of sample solution [37] and also water bath step can become long and tiresome [38]. Besides, there is the necessity of diluting the enriched micellar phase before introducing it to any analytical instrument. Particularly coupling of CPE with spectrophotometer, needs the enriched micellar phase to be diluted up to 3 mL [39], [40] which is not in agreement with green chemistry. Therefore with introduction of new microextraction methods which use less organic solvents such as dispersive liquid-liquid microextraction (DLLME) [41] and single drop microextraction (SDME) [42], CPE has been applied less and less. But since CPE is an efficient and simple technique and has much potential for extraction of variety of analytes, we tried to improve it with help of some modifications. In our first report [43], we introduced a new micro cloud point extraction (MCPE) method based on CPE in room temperature for simultaneous spectrophotometric determination of Uranium and Vanadium. We applied two modifications on CPE. For reducing cloud point temperature to room temperature, we performed MCPE in brine; and in order to minimize the use of the solvents, we utilized microcells instead of normal cells for UV–Vis spectrophotometer. Therefore we successfully eliminated a tiresome and time consuming step and also reduced the consumption of organic solvent in diluting step. Following our researches, here we applied MCPE as a very fast, simple, inexpensive and environmentally friendly method for preconcentration and determination of a few other dyes in environmental samples. For this purpose Malachite green, crystal Violet and Rhodamine B were individually extracted and determined in water and wastewater samples by MCPE/UV–Vis.
Section snippets
Instrument
A Shimadzu UV/Vis spectrophotometer, UV-160 (Kyoto, Japan), equipped with two microcells (10 μL capacity, Starna, UK) was used for measuring the absorbance and recording the spectra.
Reagents and chemicals
All chemicals were of analytical grade and were purchased from Merck KGaA (Germany). They were used without any preparation. Triton X-114 (2% v/v) and Na2SO4 (5% w/v) solutions were prepared in doubly distilled water. Stock solutions of each dye containing 500 mg/L dye, were prepared by dissolving of 0.050 g of dyes in
Absorption of spectra
After MCPE extraction of the three dyes by proposed method, their absorption spectra were recorded at the wavelength range of 400 to 800 nm against the reagent blanks (Fig. 3). The results indicate that the maximum absorption wavelength were 618 nm, 588 nm and 555 nm for MG, CV and RB respectively. Accordingly, these wavelengths were selected as the chosen absorption wavelengths for further determinations of dyes. During all of the following experiments, the blank absorbance of all reagents was
Conclusions
In this study, a fast, economical, effective and easy to operate method based on Micro-cloud point extraction for preconcentration and determination of traces of organic dyes (Malachite green, Crystal violet, and Rhodamine B) is presented. Triton X-114 was used as a non-ionic and green extractant solvent. In comparison to the similar methods of extraction, MCPE showed comparable LODs for dyes, while it is much faster. The total analysis time including microextraction was less than 7 min. Organic
Acknowledgment
This research was supported by the University of Sistan and Baluchestan.
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2023, Journal of Water Process EngineeringQuantification of twenty pharmacologically active dyes in water samples using UPLC-MS/MS
2022, HeliyonCitation Excerpt :Additionally, the presented method enables, for the first time, to determine pharmacologically active dyes such as ACR, PRO, AZA, AZC, TH, NMB, NBA, EV, PR, VBB, VBR, VPBBO in water samples. Until now there have been a few published methods for determination of dyes in water samples allowing the detection and quantification of dyes at the concentration level below 1 μg/l. LOQ for MG (0.01 μg/l) in the presented method is lower than LOQ obtained with methods developed by Mitrowska [21] (0.04 μg/l), Khan [12] (0.1 μg//l), Zhang [7] (0.25 μg/l), Fang [35] (0.5 μg/l) and Ghasemi [23] (13.6 μg/l). LOQ of another triphenylmethane dye, CV (0.01 μg/l) allows the determination of the dye at lower concentration than LOQ obtained with other authors' methods: Zhang [7] (0.25 μg/l), Šafařı́k [34] (0.5 μg/l), Sadeghi [27] (4.7 μg/l), An [19] (16 μg/l), Ghasemi [23] (17.6 μg/l), Aydin [20], Yu [16] (32 μg/l).