Elsevier

Microchemical Journal

Volume 145, March 2019, Pages 813-818
Microchemical Journal

Developing a new and simple ultrasound-assisted emulsification liquid phase microextraction method built upon deep eutectic solvents for Patent Blue V in syrup and water samples

https://doi.org/10.1016/j.microc.2018.11.053Get rights and content

Highlights

  • A green deep eutectic solvent based liquid phase microextraction method has been developed for Patent Blue V.

  • The effects of analytical parameters were systematically optimized.

  • The influences of matrix components were investigated.

  • The method has been applied to the analysis of Patent Blue V in real samples.

Abstract

In this study, Deep Eutectic Solvents (DESs) were utilized for ultrasound-assisted emulsification liquid phase microextraction (UA-ELPME) of Patent Blue V in syrup and water samples. Patent Blue V in sample solution of pH 4.0 was extracted into DES phase prepared from choline chloride and phenol. Concentration of Patent Blue V in final DES phase was measured at 627.5 nm with Uv-Vis spectrophotometry. Sample volume, pH, matrix effect, volume and type of DES, ultrasonication and centrifugation times were investigated and optimized. The developed UA-ELPME method presents a limit of detection (LOD) of 0.37 μg L−1, preconcentration factor of 15 and a relative standard deviation (RSD, %) of 6.0% under the optimum conditions. The validation was carried out with standard addition-recovery experiments for syrup and water samples. The obtained recovery results showed that the developed UA-ELPME method was applicable for routine Patent Blue V analysis in syrup and water samples.

Introduction

When microbiological features are not considered, the quality of pharmaceuticals and foods are usually assessed based on its color, texture, flavor and nutritional quality. Color is a fundamental food quality in our perception. Unless a pharmaceutics or food has an appealing color, it doesn't have a chance to be consumed by human beings regardless of its nutritional value, taste or texture [1]. Synthetic organic colorants are added to pharmaceuticals and foods in dispersion or solution. They are better than natural colorant extracts in terms of tinctorial power, stability, consistency of strength, range and brilliance of shade, and applicability [2,3]. Colors used in pharmaceuticals and foods have been scrutinized for their safety in public health in recent years. Currently, approximately ten colorants are allowed to be used as pharmaceuticals and foods coloring agents in many developed countries and many colorants were prohibited due to their carcinogenity and toxicity in the last two decades [4,5]. Patent Blue V (E-131) is synthetic organic azo colorants that may exist in widely available pharmaceuticals, foods and drinks. A thorough examination of these coloring agents is of crucial value in the food and pharmaceutic industry.

In order to analyze the colors in pharmaceuticals, foods and drinks both qualitatively and quantitatively, several analytical methods have been developed. These methods include, but not limited to, thin layer chromatography (TLC) [[3], [4], [5], [6]], dynamic column-solid phase extraction (DC-SPE) system [5], UV–Vis spectrophotometry [7,8], capillary electrophoresis (CE) [9], and chromatographic techniques [10]. Various combinations of these techniques were also used for the analyses at trace levels. The cost of the equipments and the expertise required to operate make chromatographic techniques are very disadvantageous. Long analysis times and excessive complexity of operation make some of the other methods un-preferable [11].

On the other hand, the UV–Vis spectrophotometer has a very wide usage in tracing analytes in environmental samples. Major advantages of it are its ease of operation at the analysis stage and its cheapness. Moreover, its wide availability at almost every analytical chemistry laboratory makes it much more advantageous compared to the other methods. However, low sensitivity of the Uv-Vis spectrophotometer and penetration of peaks of different species into each other limits its usage [12]. As a result, a preconcentration-separation technique is necessary to perform the correct and precise measurements. In recent years, scientists have devoted considerable efforts to enhance separation and preconcentration methods to comply with Green Chemistry demands. As a result, entire removal of toxic organic solvents or a significant reduction in their amount is considered as a main goal by many pro-green analytical chemists [13]. To answer the demands of green chemistry and to eradicate the disadvantages of traditional preconcentration methods like liquid-liquid extraction (LLE), solid phase extraction (SPE), coprecipitation and cloud point extraction (CPE), the chemists have developed micro-sized methods. These methods are liquid phase microextraction (LPME) and solid phase microextraction methods (SPME), respectively [14,15].

LPME methods have several superiorities when compared with the other methods. These superiorities include the usage of simple laboratory equipments, necessity of the minimum amount of sample, and reduction in amounts of organic chemicals, short extraction time, low cost, and high preconcentration factor. The most essential step of LPME methods is selecting correct, environmentally friendly and low-cost extraction solvents [[16], [17], [18]]. Also, green solvents can decrease environmental problems related to the usage of conventional damaging solvents. Therefore, the chemists have been chasing green, cheap and eco-friendly extraction solvents for a long time.

Deep eutectic solvents (DESs) were discovered as result of these investigations [13,19]. DESs are new types of solvents that are in use for the extraction studies [13,[19], [20], [21]]. They are safer and greener than traditional solvents. One can prepare a DES by mixing at least two cheap and low toxic components. DESs have caught a considerable attention due to their features and eutectic solvents are used in several areas such as material chemistry, organic and catalysis reactions, absorption of SO2, and CO2 gases, nanotechnology etc. Choline chloride (ChCl), which is a biodegradable, harmless and cheap quaternary ammonium salt, is one of the most common component used in preparation of DES. Water-soluble choline is also commonly used as an additive to animal food. Choline chloride is capable of forming hydrogen bonds [22,23]. Some of DESs are in the liquid state at 25 °C including the used DES in the presented study. This provides an advantage for usage of DESs in microextraction studies.

The aim of this study was to develop a simple, cheap and quick microextraction method built upon deep eutectic solvents for the separation/enrichment of Patent Blue V from syrup and water samples prior to its UV–Vis spectrophotometric determination.

Section snippets

Instrumentation

pH measurements were performed with a WTW730 model pH-meter. Measurements of absorbance were carried out by Optizen alpha model Mecasys double-beam Uv-Vis spectrophotometer by using quartz cells. A Hettich Universal 320 centrifuge (Tuttlingen, Germany) was used for phase separation. A Wisd Wise Clean (Seoul, Korea) ultrasonic bath which has maximum 160 W ultrasonic peak output and 35 kHz of Frequency was used for sonication of solutions in the experiments.

Reagents and solutions

All chemicals in the experiments were

Influence of pH

The measurement of precise pH value of sample solution is fundamental in separation/preconcentration studies for almost all analytes [[27], [28], [29], [30], [31], [32]]. The influence of pH of solution on the recovery values of Patent Blue V was worked in the range of pH 2.0–10.0 as an initial optimization parameter by using desired pH. As shown in Fig. 2, the recovery values increased with the pH increase reached the quantitative value (≥95%) at pH 4.0 and then decreased again. The obtained

Conclusions

In this paper, a DES based ultrasound-assisted emulsification liquid phase micro extraction method (UA-ELPME) was used to accurate, fast and reliable analysis of the Patent Blue V in syrup and water samples. The most important superiority of this method is the use of the DESs as green solvent in extraction. The suggested method is eco-friendly, simple, inexpensive and fast for dependable identification of Patent Blue V in different syrup and water samples. The quantitative recovery results

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