A simple and green deep eutectic solvent based air assisted liquid phase microextraction for separation, preconcentration and determination of lead in water and food samples by graphite furnace atomic absorption spectrometry

Deep Eutectic Solvents for Extraction and Preconcentration of Organic and Inorganic Species in Water and Food Samples: A Review

Deep eutectic solvents (DESs) have been developed as green solvents and these are capable as alternatives to conventional solvents used for the extraction of organic and inorganic species from food and water samples. The continuous generation of contaminated waste and increasing concern for the human health and environment have compelled the scientific community to investigate more ecological schemes. In this concern, the use of DESs have developed in one of the chief approach in the field of chemistry. These solvents have appeared as a capable substitute to conventional hazardous solvents and ionic liquids. The DESs has distinctive properties, easy preparation and components availability. It is not only used in scienctific fields but also used in quotidian life. There are many advantages of DESs in analytical chemistry, they are largely used for extraction and determination of inorganic and organic compounds from different samples. In previous a few years, several advanced researches have been focused on the separation and preconcentration of low level of pollutants using DESs as the extractants. This review summarizes the use of DESs in the separation and preconcentration of organic and inorganic species from water and food samples using various microextraction processes.

Sensing lead ions in water: a comprehensive review on strategies and sensor materials

It is well-known fact that elevated lead ions (Pb2+), the third most toxic among heavy metal ions in aqueous systems, pose a threat to human health and aquatic ecosystems when they exceed permissible limits. Pb2+ is commonly found in industrial waste and fertilizers, contaminating water sources and subsequently entering the human body, causing various adverse health conditions. Unlike being expelled, Pb2+ accumulates within the body, posing potential health risks. The harmful impact of presence of Pb2+ in water have prompted researchers to diligently work toward maintaining water quality. Recognizing the importance of Pb2+, this review article makes a sincere and effective effort to address the issues associated with Pb2+. This overview article gives insights into various sensing approaches to detect Pb2+ in water using different sensing materials, including 2-dimensional materials, thiols, quantum dots, and polymers. Herein, different sensing approaches such as electrochemical, optical, field effect transistor-based, micro-electromechanical system-based, and chemi resistive are thoroughly explained. Field effect transistor-based and chemiresistive work on similar principles and are compared on the basis of their fabrication processes and sensing capabilities. In conclusion, future directions for chemiresistive sensors in Pb2+ detection are proposed, emphasizing their simplicity, portability, straightforward functionality, and ease of fabrication. Notably, it sheds light on various thiol and ligand compounds and coupling strategies utilized in Pb2+ detection. This comprehensive study is expected to benefit individuals engaged in Pb2+ detection.

Deep eutectic solvents as a green alternative for trace element analysis in food and beverage samples: Recent advances and challenges

Metals and metalloids have different effects on human health even at trace levels. Some of them are essential for living organisms while others can be toxic. Therefore, the determination of trace elements in food and beverage is highly important to understand their impact in human health. A new generation of solvents named deep eutectic solvents (DES) has emerged as a green alternative for trace element analysis, owing to their low toxicity, biodegradability, and high extraction capacity. In recent years, the application of DES in extraction techniques for trace element analysis in food and beverage samples has increased significantly. This review summarizes recent advances and challenges on the application of DES to develop microextraction techniques useful for the analysis of samples with complex matrices. The importance of the use of biodegradable substances instead of classic organic solvents, which are toxic, volatile, and flammable in methods for elemental analysis with a positive environmental impact is also highlighted. Finally, conclusions and future challenges arising from the use of DES in microextraction techniques are discussed.

Deep eutectic solvents for the determination of endocrine disrupting chemicals

The harmful effects of endocrine disrupting chemicals (EDCs) to humans and other organisms in the environment have been well established over the years, and more studies are ongoing to classify other chemicals that have the potential to alter or disrupt the regular function of the endocrine system. In addition to toxicological studies, analytical detection systems are progressively being improved to facilitate accurate determination of EDCs in biological, environmental and food samples. Recent microextraction methods have focused on the use of green chemicals that are safe for analytical applications, and present very low or no toxicity upon disposal. Deep eutectic solvents (DESs) have emerged as one of the viable alternatives to the conventional hazardous solvents, and their unique properties make them very useful in different applications. Notably, the use of renewable sources to prepare DESs leads to highly biodegradable products that mitigate negative ecological impacts. This review presents an overview of both organic and inorganic EDCs and their ramifications on human health. It also presents the fundamental principles of liquid phase and solid phase microextraction methods, and gives a comprehensive account of the use of DESs for the determination of EDCs in various samples.

Analytical techniques for determination of heavy metal migration from different types of locally made plastic food packaging materials using ICP-MS

Plastic food packaging is an essential element for customer convenience and the preservation of food quality. Nonetheless, heavy metals in the packaging materials, either intentionally or nonintentionally added, can be transferred to the food. Therefore, determining heavy metal contents in these packaging materials is essential. In this study, heavy metals, including Co, Ge, As, Cd, Sb, Pb, Al, and Zn from different intrinsic plastic food packaging materials were analyzed using the inductively coupled plasma-mass spectrometry (ICP-MS) method. Moreover, the migration of these elements into the environment was also investigated. This method is validated following the new technique's requirements, which include linearity range, accuracy, precision, the limit of detection (LOD), and the limit of quantitation (LOQ). The method has been suitably validated with the regression equation from the standards prepared in HNO₃ 1% v/v. The linear range was found to be ~1-20 ng mL^-1 for Co, Ge, As, Cd, Sb, and Pb and 5-80 ng mL^-1 for Al and Zn elements. The LODs are ~0.10, 0.25, 0.12, 0.13, 0.11, 0.12, 0.61, and 0.85 ng mL^-1, and the LOQs are 0.33, 0.83, 0.40, 0.43, 0.36, 0.40, 2.01, and 2.81 ng mL^-1 obtained for Co, Ge, As, Cd, Sb, Pb, Al, and Zn, respectively. In addition, the recovery percentages received ranged 85.4%-94.1% for Co, 82.6%-95.1% for Ge, 86.3%-97.9% for As, 87.3%-96.3% for Cd, 88.0%-104.4% for Sb, 96.3%-106.0% for Pb, 88.4%-104.0% for Al, and 95.1%-99.7% for Zn. Finally, the migration of these heavy metals from polypropylene (PP) and polystyrene (PS) into foodstuffs was also simulated according to EU legislation, showing that the most leached element was Zn, followed by Al and Pd, with the migration of ~8.38% and ~0.41%, and ~0.19%, respectively.

Detection Techniques for Lead Ions in Water: A Review

Lead pollution has increasingly become the focus of environmental pollution, which is a great harm to the ecological environment and human health. Strict control of the emission of lead pollutants and accurate monitoring of lead are very important. The lead ion detection technologies are introduced here, including spectrophotometry, electrochemical method, atomic absorption spectrometry, and other detection methods, and the methods' applicability, the advantages, and disadvantages are discussed. The detection limits of voltammetry and atomic absorption spectrometry are as low as 0.1 μg/L, and those of atomic absorption spectrometry are as low as 2 μg/L. The detection limit of photometry is higher (0.01 mg/L), but this method can be achieved in most laboratories. The application of different extraction pretreatment technologies in lead ion detection is introduced. The new technologies develop at home and abroad, such as precious metal nanogold technology, paper microfluidic technology, fluorescence molecular probe technology, spectroscopy, and other emerging technologies in recent years, are reviewed, and the principle and application of various technologies are expounded.

Reversed-phase dispersive liquid-liquid microextraction based on decomposition of deep eutectic solvent for the determination of lead and cadmium in vegetable oil

In this work, a reversed-phase dispersive liquid-liquid microextraction procedure based on the decomposition of deep eutectic solvent was suggested for the first time. The procedure was utilized for fast and simple separation of lead and cadmium from vegetable oil samples. The procedure assumed mixing of oil sample and DES based on menthol, formic acid and water. Water as component of DES promoted its decomposition in sample matrix resulting menthol dissolution in the sample phase and dispersion of aqueous formic acid solution. In this procedure menthol acted as a dispersive solvent during DES decomposition for dispersion of aqueous formic acid solution. The metals were determined by the square-wave anodic stripping voltammetry. The limits of detection, were 0.01 µg kg^-1 for lead and 0.006 µg kg^-1 for cadmium. The RSD was less then 6% for both analytes. The enrichment factor was 36 and 39 for lead and cadmium, respectively.

Air assisted in situ deep eutectic solvent decomposition followed by the solidification of floating organic droplets-liquid-liquid microextraction method for extraction of azole antifungal drugs in biological samples prior to high-performance liquid chromatography

A free dispersive method, air-assisted in situ deep eutectic solvent decomposition followed by the solidification of floating organic droplets liquid-liquid microextraction was indicated in this study. This technique was utilized to simultaneously ascertain some azole antifungal drugs prior to high-performance liquid chromatography. In this research, a quasi-hydrophobic deep eutectic solvent was formed from tetrabutylammonium bromide and 1-dodecanol as an organic solvent at a 1:2 molar ratio. The synthesized deep decomposition in the sample solution caused in situ dispersion of extraction solvent and analytes. Air-assisted enhanced a dispersion condition in the sample solution. 1-dodecanol as a green option was replaced with typical extraction solvents providing the advantages of a suitable freezing point near room temperature and low density. The effect of important analytical parameters on the extraction recovery of analytes was assessed. Under these optimal conditions, the limits of detection and limits of quantitation determined were in the range of 0.5-2.8 μg L^-1 and 1.5-9 μg L^-1 , for water, urine and plasma samples, respectively. The Intra-day and inter-day relative standard deviations (RSD% n = 5) were calculated to be 2.9-4.6 % and 4.2-8.9 %, respectively. The results represented the effectiveness of the developed method for the extraction and determination of analytes in biological samples. This article is protected by copyright. All rights reserved.

Dispersive liquid-liquid microextraction based on deep eutectic solvent for elemental impurities determination in oral and parenteral drugs by inductively coupled plasma optical emission spectrometry

A simple, fast, sensitive and green pretreatment method for determination of Cd, Co, Hg, Ni, Pb and V in oral and parenteral drug samples using inductively coupled plasma optical emission spectrometry (ICP OES) has been developed. According to United States Pharmacopoeia (USP), those metals must be reported in all pharmaceutical products for quality control evaluation (i.e., elemental impurities from classes 1 and 2A of USP Chapter 232). To improve the analytical capabilities of ICP OES, a dispersive liquid-liquid microextraction (DLLME) has performed using a safe, cheap and biodegradable deep eutectic solvent (DES) as extractant solvent (a mixture of 2:1 M ratio of DL-menthol and decanoic acid). Seven parameters affecting the microextraction efficiency have carefully optimized by multivariate analysis. Under optimized conditions, the DES-based DLLME-ICP OES procedure improved limit of quantitation (LOQ) values on range from 12 to 85-fold and afforded an enrichment factor on average 60-times higher than those obtained to direct ICP OES analysis. Consequently, LOQ values for Cd, Co, Hg, Ni, Pb and V have been on average 10-times lower than target limits recommended for drugs from parenteral route of administration. Trueness has evaluated by addition and recovery experiments following USP recommendations for three oral drug samples in liquid dosage form and three parenteral drugs. Recovery and RSD values have been within the range of 90-109% and 1-6%, respectively. All analytes were below the respectives LOQ values, hence, lower than the limits proposed by USP Chapter 232.

Deep Eutectic Solvents Application in Food Analysis

Current trends in Analytical Chemistry are focused on the development of more sustainable and environmentally friendly procedures. However, and despite technological advances at the instrumental level having played a very important role in the greenness of the new methods, there is still work to be done regarding the sample preparation stage. In this sense, the implementation of new materials and solvents has been a great step towards the development of "greener" analytical methodologies. In particular, the application of deep eutectic solvents (DESs) has aroused great interest in recent years in this regard, as a consequence of their excellent physicochemical properties, general low toxicity, and high biodegradability if they are compared with classical organic solvents. Furthermore, the inclusion of DESs based on natural products (natural DESs, NADESs) has led to a notable increase in the popularity of this new generation of solvents in extraction techniques. This review article focuses on providing an overview of the applications and limitations of DESs in solvent-based extraction techniques for food analysis, paying especial attention to their hydrophobic or hydrophilic nature, which is one of the main factors affecting the extraction procedure, becoming even more important when such complex matrices are studied.

Investigation of the Conditions for Preconcentration of Cadmium Ions by Solid Phase Extraction Method Using Modified Juglans regia L. Shells

BACKGROUND

Juglans regia L. shells as agricultural waste can be considered as alternative sorbents to minimize the problems associated with heavy metal pollution.

OBJECTIVE

In this study, J. regia shells (JRS) and JRS modified with hydrazine hydrate (JRS-HH) were used as sorbents and compared for the preconcentration of Cd(II) ions from aqueous solution.

METHODS

For the characterization of sorbents, scanning electron microscopy and energy dispersive X-ray (SEM/EDX) analysis and Fourier transform infrared (FTIR) spectroscopy were used. For preconcentration, the solid phase extraction (SPE) technique was used. Preconcentration studies were performed by column method and pH, eluent type and concentration, sample volume, flow rate, and interfering ions effect were studied to determine the optimum column parameters.

RESULTS

The limit of detection (LOD) of the sorbents (JRS and JRS-HH) are 0.31 and 0.18 µg/L, respectively. According to the Langmuir isotherm model for both sorbents, for JRS KL = 0.030 L/mg, R2 = 0.992, 0.016 L/mg, and for JRS-HH KL = 0.016 L/mg, R2 = 0.998 and maximum adsorption capacities of the sorbents were found to be as 29.6 and 65.7 mg/g, respectively. The mean recoveries and RSD values at a 95% confidence level (N = 6) for Cd(II) were 100.9% and 3.42, and 100.6% and 3.79, for the JRS and JRS-HH sorbents, respectively.

CONCLUSIONS

Using this method good results were obtained when compared with those in the literature and the proposed method was successfully applied to the analysis of the certificated reference material (NIST 1640).

HIGHLIGHTS

JRS are an effective and inexpensive sorbent for the preconcentration of metal ions when modified. Thus, low-cost agricultural wastes are both recovered and have an economic value.

A novel liquid colorimetric probe for highly selective and sensitive detection of lead (II)

A novel liquid colorimetric sensor based on deep eutectic solvent (DES) was developed for the preconcentration and detection of Pb²⁺ in fruit juice, milk and cereal samples. The colorimetric probe was simply fabricated by adding dithizone (DZ) into DES, prepared from choline chloride and phenol. Pb²⁺ was formed complex with DZ in the probe, providing hydrophobic complex of [Pb-DZ] which was simultaneously extracted into DES and the color was changed from light orange to carmine red. The enriched [Pb-DZ] in DES was detected using spectrophotometer at 520 nm and naked-eyes. In addition, a smartphone in combination with an Image J program was used as an alternative detection device. Under optimal conditions, the enrichment factor was 92 with LOD of 2.1 µg L^-1 and the linear range was 0.007-0.075 mg L^-1. The proposed liquid colorimetric sensor was successfully applied for Pb²⁺ detection in various food samples and the results were in good agreement with those obtained by FAAS. The advantages of this method are simple, rapid, environmental friendly and low cost.

Development of an Ion-Pair Dispersive Liquid-Liquid Microextraction Method Based on a Ternary Deep Eutectic Solvent for Determination of Some Herbicide Residues in Edible Oil Samples

An ion-pair deep eutectic solvent (DES)-based dispersive liquid-liquid microextraction method was introduced and applied for the extraction of some acidic herbicides from edible oil samples prior to their determination by high performance liquid chromatography. First, a ternary DES composed of decanoic acid, dichloroacetic acid, and phosphocholine chloride is prepared under mild conditions. Then, the analytes are extracted into an alkaline solution from the oil samples by deprotonation of the herbicides. Afterward, the deprotonated analytes are extracted into the prepared DES with the aid of tri-butyl amine (as an ion-pair agent) in the presence of acetic acid (as a pH adjustment agent and dispersive solvent). The validation parameters indicated that the method has low limits of detection (0.09-0.72 ng mL-1) and quantification (0.30-2.3 ng mL-1), an acceptable percision (relative standard deviation ≤  9.0%) and high extraction recoveries (85-94%), and enrichment factors (566-626). The method was used in the analysis of 35 edible oil samples to assessment the studied analytes and the presence of haloxyfop was confirmed in three corn oils.

Determination of prohibited lead and cadmium traces in hair dyes and henna samples using ultrasound assisted-deep eutectic solvent-based liquid phase microextraction followed by microsampling-flame atomic absorption spectrometry

In this study ultrasound assisted-deep eutectic solvent-based liquid phase microextraction followed by microsampling-flame atomic absorption spectrometry was developed to determine prohibited lead and cadmium traces in hair dye and henna samples. For this purpose, deep eutectic solvent, prepared from choline chloride and phenol, was used as an extraction solvent, dithizone was used as a complexing agent, and THF was used as an aprotic solvent. All parameters that affect extraction efficiency, such as pH, the DES volume and composition, the extraction time, the amount of dithizone, were optimized. Under the optimal conditions, for Pb(ii) and Cd(ii), enhancement factors of 92 and 57, LODs of 2.5 μg L^-1 and 0.75 μg L^-1, LOQs of 7.8 μg L^-1 and 2.5 μg L^-1, linear working ranges of 10-250 μg L^-1 and 2.5-50 μg L^-1, were obtained, respectively. Relative standard deviation (n = 10) was calculated to be 2.7 for 100 μg L^-1 of Pb(ii) and 2.1 for 25 μg L^-1 of Cd(ii). The matrix effect was investigated by comparing the solvent-based calibration curve with the matrix-matched calibration curve. The determination of lead and cadmium in hair dye and henna samples without being affected by the sample matrix was successfully performed. The lead content was between 1.3 and 6.5 μg g^-1, and the cadmium content was between 0.028 and 0.54 μg g^-1 for the selected hair dye and henna samples.

Metal Nanostructures for Environmental Pollutant Detection Based on Fluorescence

Heavy metal ions and pesticides are extremely dangerous for human health and environment and an accurate detection is an essential step to monitor their levels in water. The standard and most used methods for detecting these pollutants are sophisticated and expensive analytical techniques. However, recent technological advancements have allowed the development of alternative techniques based on optical properties of noble metal nanomaterials, which provide many advantages such as ultrasensitive detection, fast turnover, simple protocols, in situ sampling, on-site capability and reduced cost. This paper provides a review of the most common photo-physical effects impact on the fluorescence of metal nanomaterials and how these processes can be exploited for the detection of pollutant species. The final aim is to provide readers with an updated guide on fluorescent metallic nano-systems used as optical sensors of heavy metal ions and pesticides in water.

N-doped mesoporous carbon as a new sorbent for ultrasonic-assisted dispersive micro-solid-phase extraction of 1-naphthol and 2-naphthol, the biomarkers of exposure to naphthalene, from urine samples

This study aimed to optimize a new sample preparation method using N-doped mesoporous carbon sorbent for simultaneous measurement of 1-naphthol and 2-naphthol, the biomarkers of exposure to naphthalene. The samples were analyzed using high-performance liquid chromatography supplied with ultraviolet detector (HPLC-UV). N-doped mesoporous carbon sorbent was obtained via the hard template procedure. The synthesized nanosorbent was then characterized by transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), and elemental analysis (CHN). The effective factors in the extraction of the studied biomarkers were examined by the Box-Behnken (BBD) methodology. Regarding the optimum conditions, the sketched calibration curve for naphthols was linear in the concentration levels of 1-600 µg L^-1 for human urine samples. The accuracy and reproducibility of the introduced method were determined using the relative recovery (RR %) and relative standard deviation (RSD %) tests on the fortified urine samples. RR% and RSD% were found to be 97.0-101.2% and 3.1-9.0%, respectively. The calculated method detection limit of the optimized procedure was 0.3 µg L^-1 and 0.5 µg L^-1 for 1-naphthol and 2-naphthol, respectively.

Review: Microextraction Technique Based New Trends in Food Analysis

Food chemistry is the study and classification of the quality and origin of foods. The identification of definite biomarkers and the determination of residue contaminants such as toxins, pesticides, metals, human and veterinary drugs, which are a very common source of food-borne diseases. The food analysis is continuously demanding the improvement of more robust, sensitive, highly efficient, and economically beneficial analytical approaches to promise the traceability, safety, and quality of foods in the acquiescence with the consumers and legislation demands. The traditional methods have been used at the starting of the 20th century based on wet chemical methods. Now it existing the powerful analytical techniques used in food analysis and safety. This development has led to substantial enhancements in the analytical accuracy, precision, sensitivity, selectivity, thereby mounting the applied range of food applications. In the present decade, microextraction (micro-scale extraction) pays more attention due to its futures such as low consumption of solvent and sample, throughput analysis easy to operate, greener, robotics, and miniaturization, different adsorbents have been used in the microextraction process with unique nature recognized with wide range applications.

Deep Eutectic Solvent-Based Microextraction of Lead(II) Traces from Water and Aqueous Extracts before FAAS Measurements

Microextraction procedures for the separation of Pb(II) from water and food samples extracts were developed. A deep eutectic solvent composed of α-benzoin oxime and iron(III) chloride dissolved in phenol was applied as a phase separator support. In addition, this deep eutectic mixture worked as an efficient extractor of Pb(II). The developed microextraction process showed a high ability to tolerate the common coexisting ions in the real samples. The optimum conditions for quantitative recoveries of Pb(II) from aqueous extracts were at pH 2.0, conducted by adding 150 µL from the deep eutectic solvent. The quantitative recoveries were obtained with various initial sample volumes up to 30 mL. Limits of detection and limits of quantification of 0.008 and 0.025 µg L^-1 were achieved with a relative standard deviation (RSD%) of 2.9, which indicates the accuracy and sensitivity of the developed procedure. Recoveries from the reference materials, including TMDA 64.2, TMDA 53.3, and NCSDC-73349, were 100%, 97%, and 102%, respectively. Real samples, such as tap, lake, and river water, as well as food samples, including salted peanuts, chickpeas, roasted yellow corn, pistachios, and almonds, were successfully applied for Pb(II) analysis by atomic absorption spectroscopy (AAS) after applying the developed deep eutectic solvent-based microextraction procedures.

Application of aeration-assisted homogeneous liquid-liquid microextraction procedure using Box-Behnken design for determination of curcumin by HPLC

A simple, efficient, and rapid sample preparation method based on aeration-assisted homogeneous liquid-liquid microextraction was developed for determination of curcumin in food samples by high-performance liquid chromatography. The centrifuge step has been eliminated in this procedure. The effects of some variables, such as pH, volume of extraction solvent, extraction time, and salt effect, were studied through a Box-Behnken design method. Under the optimum conditions, calibration curves of curcumin were linear in the range of 0.08-4000 μg/mL with R2  = 0.997. Limit of detection and relative standard deviation were 0.019 μg/mL and 3.01%, respectively. The preconcentration factor achieved was 166. The proposed method was successfully applied to determination of curcumin in various food samples.

Preparation of a new three-component deep eutectic solvent and its use as an extraction solvent in dispersive liquid-liquid microextraction of pesticides in green tea and herbal distillates

BACKGROUND

A new solvent, deep eutectic solvent, in which there is growing interest, has been prepared and used as an extraction solvent in the dispersive liquid-liquid method of microextraction. To prepare the solvent, dichloroacetic acid, l-menthol, and n-butanol are mixed at a molar ratio of 4:1:1 and the deep eutectic solvent is formed after heating. Then a dispersive liquid-liquid microextraction method using the prepared solvent is used for the extraction and preconcentration of some pesticides from an aqueous sample. To carry out the procedure, the deep eutectic solvent is mixed with methanol and rapidly injected by a syringe into the aqueous sample containing the analytes. After centrifuging, an aliquot of the sedimented phase is injected into the gas chromatograph. The influence of several variables on the extraction efficiency was investigated and optimized.

RESULTS

Extraction recoveries and enrichment factors were obtained in the ranges of 53-86% and 1760-2853, respectively. The intra- (n = 6) and inter-day (n = 5) precision of the method was satisfactory, with relative standard deviations ≤ 7% obtained at two concentrations of 10 and 50 μg L^-1 of each analyte. Moreover, detection and quantification limits for the target analytes were obtained in the ranges of 0.11-0.23 and 0.38-0.74 μg L^-1 , respectively.

CONCLUSION

Different samples, including green tea, rose water, lemon balm, mint, and pussy willow distillates were analyzed successfully using the method that was developed, and chlorpyrifos was found in rose water at a concentration of 17 ± 1 μg L^-1 (n = 3). © 2019 Society of Chemical Industry.

Highly sensitive and selective optical sensor for lead ion detection based on liquid crystal decorated with DNAzyme

Lead ions (Pb²⁺) are one of the major environmental pollutants that are dangerous for human health, thus the detection methods of Pb²⁺ become very important as well. However, most reported techniques suffer from drawbacks such as long time, expensive equipment and complicated testing process, which prevent the use of real-time application. Herein, we demonstrate a novel liquid crystal optical sensor for detection of Pb²⁺ based on DNAzyme and its combined strand. The ordered and disordered configuration of liquid crystals, induced by complementary DNA strand and catalytically cleaved DNA in presence of lead ion separately, leads to dark and bright optical image under POM. The proposed naked-eye optical sensor possesses an extremely broad detection range of Pb²⁺ from 50 nM to 500 µM, with a low detection limit about 36.8 nM. The sensor also demonstrates high selectivity of Pb²⁺ from many other metal ions. The proposal LC sensor is highly sensitive and selective for Pb²⁺ detection, which provides a novel platform for other heavy metal, DNAs or antigen in biological and chemical fields by modifying sensing molecules.