Dispersive liquid–liquid microextraction combined with microvolume spectrophotometry to turn green the 5530 APHA standard method for determining phenols in water and wastewater

Spectrophotometric determination of phenol impurity in phenoxyethanol and phenol index of drinking water and municipal wastewater effluent after salting-out assisted liquid phase microextraction (SA-LPME)

In this study, a novel and convenient analytical method based on salting-out-assisted liquid phase microextraction (SA-LPME) has been developed. A spectrophotometric technique was employed to quantify the concentration of phenol in drinking water and treated wastewater, as well as the phenol impurity in 2-phenoxyethanol (PE). To accomplish this, a solution containing dissolved PE was supplemented with 4-aminoantipyrine (4-AAP) and hexacyanoferrate. Subsequently, NaCl was added to induce the formation of a two-phase system, consisting of fine droplets of PE as an extractant phase in the aqueous phase. The resulting red derivative was then extracted into the extractant phase and separated through centrifugation. Finally, the absorbance of the extracted derivative was measured at 520 nm. The Response Surface Methodology (RSM) based on the Box-Behnken Design (BBD) was employed to optimize the influential factors, namely 4-Aminoantipyrine (4-AAP), buffer (pH = 10), hexacyanoferrate, and NaCl. By utilizing the optimal conditions (buffer: 50 μL, 4-AAP (1% w/v): 80 μL, hexacyanoferrate (10% w/v): 65 μL, and NaCl: 0.7 g per 10 mL of the sample), the limit of detection was determined to be 0.7 ng mL-1 and 0.22 μg g-1 for water and PE samples, respectively. The relative standard deviation (RSD) and correlation of determination (r2) obtained fell within the range of 2.4-6.8% and 0.9983-0.9994, respectively. Moreover, an enrichment factor of 65 was achieved for a sample volume of 10 mL. The phenol concentration in two PE samples (PE-1, PE-2), provided by a pharmaceutical company (Pars Sadra Fanavar, Iran), were determined to be 0.83 ± 0.05 μg g-1 and 2.70 ± 0.14 μg g-1, respectively. Additionally, the phenol index in drinking water and treated municipal wastewater was found to be 3.60 ± 1.06 ng mL-1 and 4.60 ± 1.17 ng mL-1, respectively. These mentioned samples were spiked in order to evaluate the potential influence of the matrix. The relative recoveries from PE-1, PE-2 samples, drinking water, and treated municipal wastewater samples were measured as 104.5%, 97.5%, 101.6%, and 107.8%, respectively, indicating no matrix effect.

Whole-cell bioreporter application for rapid evaluation of hazardous metal bioavailability and toxicity in bioprocess

Assessing heavy metal bioavailability and toxicity during bioprocess is critical for advancing green biotechnology. The capability of whole-cell bioreporters to measure heavy metal bioavailability has been increasingly recognized. The advantages of this technology being applied to bioprocess monitoring are less studied. Here we investigate the potential of a cadmium- and lead-sensitive bioreporter to be used for heavy metals as a class, which holds great interest for bioprocess applications. We evaluated the bioavailability of eight individual heavy metals with bioreporter zntA, as well as the bioavailability and toxicity of mixed metals. The bioavailability and toxicity of heavy metals in bioprocess samples were also evaluated. We have demonstrated for the first time that the zntA bioreporter can effectively detect the bioavailability of zinc, nickel, and cobalt with limit of detection lower than 0.01, 0.08 and 0.5 mg·L-1, respectively. The detection limits meet the requirements of the WHO, the U.S. Environmental Protection Agency, and the China drinking water quality standards, which makes this approach reasonable for monitoring heavy metal bioavailability in bioprocess. LIVE/DEAD toxicity experiments have been conducted for the detection of mixed metal solution toxicity to zntA bioreporter which shows an EC50 (as EC50, concentration for 50% of maximal effect) value of mixed metal solution is 3.84 mg·L-1. Samples from wastewater treatment plants, sludge treatment plants and kitchen waste fermentation processes were analyzed to extend upon the laboratory results. The results of this study confirm the potential for practical applications of bioreporter technology in bioprocess monitoring. In turn, development for such practical applications is key to achieve the necessary level of commercialization to further make the routine use of bioreporters in bioprocess monitoring feasible.

Spectrophotometric determination of phenol and chlorophenols by salting out assisted liquid-liquid extraction combined with dispersive liquid-liquid microextraction

In this work, salting out liquid-liquid extraction (SALLE) combined with dispersive liquid-liquid microextraction (DLLME) was developed as a novel extraction method for extraction and preconcentration of phenol and chlorophenols (CPs) in environmental water samples. The analytes were derivatized with 4-aminoantipyrineand determined by spectrophotometry. Experimental parameters such as type and volume of the organic solvent, type and amount of salt, pH and vortex time were optimized. Under the optimum conditions, calibration curves were linear in the range of 1-300 μg L^-1 and limit of detections (LODs) were in the range of 0.15-0.22 μg L^-1. The extraction recoveries and enrichment factors ranged from 94.80% to 106.1% and 78.12 to 82.53, respectively. Repeatability of method based on five replicate measurements of phenols was in the range of 4.8-7.2%. The results obtained in this study showed that the proposed method is simple, rapid and environmentally friendly with high extraction efficiency for preconcentration and determination of phenol and CPs in real samples. The proposed method was also compared with the reference method.

Development of a Polyphenol Oxidase Biosensor from Jenipapo Fruit Extract (Genipa americana L.) and Determination of Phenolic Compounds in Textile Industrial Effluents

In this work, an innovative polyphenol oxidase biosensor was developed from Jenipapo (Genipa americana L.) fruit and used to assess phenolic compounds in industrial effluent samples obtained from a textile industry located in Jaraguá-GO, Brasil. The biosensor was prepared and optimized according to: the proportion of crude vegetal extract, pH and overall voltammetric parameters for differential pulse voltammetry. The calibration curve presented a linear interval from 10 to 310 µM (r² = 0.9982) and a limit of detection of 7 µM. Biosensor stability was evaluated throughout 15 days, and it exhibited 88.22% of the initial response. The amount of catechol standard recovered post analysis varied between 87.50% and 96.00%. Moreover, the biosensor was able to detect phenolic compounds in a real sample, and the results were in accordance with standard spectrophotometric assays. Therefore, the innovatively-designed biosensor hereby proposed is a promising tool for phenolic compound detection and quantification when environmental contaminants are concerned.

Evaluation of total phenol pollution in water of San Martin Canal from Santiago del Estero, Argentina

Santiago del Estero is a province located in northwestern Argentina. The Dulce River is used for irrigation through a vast network of channels and ditches, including the San Martin Canal (SMC), which crosses the capital city of Santiago del Estero. This canal's water is used for drinking, as well as recreational use for the general population. However, this river has been seriously polluted for several decades. The present study focuses on the identification and the quantification of the water pollution levels of total phenols in the SMC according to the seasonal periods. Water samples from various areas of the canal in different months of the year, extending from December to September, were collected for analysis. Additionally, the concentration of total dissolved solids (TDS), chlorides, sulphates, nitrites and organic matter, as well as water hardness and alkalinity, were analysed in order to conduct a more complete study of the contamination of this area. The results showed a worrying total phenol concentration that exceeded the limit set by Argentine legislation for drinking water, as well as water for recreational use (5 μg/L). The total phenol (TP) concentration was directly determined by a molecular absorption spectroscopy method based on a new flow injection analysis system (FIA). Under the selected experimental conditions, the detection and quantification limits were 0.0490 and 0.1633 μg/mL, respectively. The developed method provides a number of improvements related to the speed of analysis, the restricted consumption of the reagents and sample volumes and the unnecessary sample treatment that contribute to environmentally friendly analytical chemistry. The results showed that TP make a significant contribution in the SMC pollution, especially during the months of April (400 ± 110 μg/L) and September (240 ± 20 μg/L). A high sulphate concentration that was higher than the limit allowed by the legislation was also found.

Determination of phthalate esters in seawater of Chabahar Bay using dispersive liquid-liquid microextraction coupled with GC-FID

Phthalate esters (PEs), a group of environmental pollutants which are possibly carcinogenic to humans, have been detected in seawater. Seven PEs in seawater were quantitatively determined by using gas-chromatography flame ionizing detection after executing dispersive liquid-liquid microextraction. The suggested method is optimized for microextraction and determination of PEs in artificial sea water. Factors affecting the microextraction procedure such as the type and volume of extracting and dispersive solvents (carbon tetrachloride, 20 μL; methanol, 0.5 mL), extraction time and pH (7) were investigated. Under optimum conditions, the limit of detection of the analytes were obtained between 0.04 and 4.52 μg·L^-1, and linearity and linear range were of 0.999 ≥ R² ≥ 0.994 and 10-560 μg·L^-1 respectively. Enrichment factors were found in the range of 761-827 fold, while the relative standard deviations of the analytes were between 0.17 and 7.5% (n = 6) for real sea water samples. Using this method, total PEs content of seawater from several locations in Chabahar Bay (the southeast part of Iran) was estimated 2.33-90.45 μg·L^-1.

Optimization and modeling of preconcentration and determination of dyes based on ultrasound assisted-dispersive liquid-liquid microextraction coupled with derivative spectrophotometry

Present study is based on describing an ultrasound-assisted dispersive liquid-liquid microextraction coupled with derivative spectrophotometry (UAS-DLLME-UV-vis) as useful technique for selective determination of crystal violet (CV) and azure b (Az-B). The significant factors like pH, extractor volume, disperser value and extraction time contribution and their numerical coefficient in quadratic model were calculated according to central composite design (CCD). According to desirability function (DF) as good criterion the best experimental conditions was adjusted and selected at pH of 7.0, 170μL of chloroform, 800μL of ethanol that strongly mixed with the aqueous phase via 4min sonication. Additionally, under study system was modeled by trained artificial neural networks (ANNs) as fitness function with acceptable error of MSE 2.97×10^-06 and 1.15×10^-05 with R²: 0.9999 and 0.9997 for CV and Az-B, respectively. The optimum conditions by using genetic algorithm (GA) method was pH of 6.3, 160μL of chloroform, 740μL of ethanol and 4.5min sonication. Under above specified and optimize conditions, the predicted extraction percentage were 99.80 and 102.20% for CV and Az-B, respectively. The present UAS-DLLME-UV-vis procedure has minimum interference from other substances assign to the matrix, which candidate this method as good alternative to quantify under study dyes content with recoveries in the range of 86-100% for dyes. The detection limits were 2.043ngmL^-1 and 1.72ngmL^-1, and limits of quantitation were 6.81ngmL^-1 and 5.727ngmL^-1 for CV and Az-B, respectively. The proposed methodology was successfully applied for quantification of under study analytes at different media.

Amperometric Biosensor Based on Zirconium Oxide/Polyethylene Glycol/Tyrosinase Composite Film for the Detection of Phenolic Compounds

A phenolic biosensor based on a zirconium oxide/polyethylene glycol/tyrosinase composite film for the detection of phenolic compounds has been explored. The formation of the composite film was expected via electrostatic interaction between hexacetyltrimethylammonium bromide (CTAB), polyethylene glycol (PEG), and zirconium oxide nanoparticles casted on screen printed carbon electrode (SPCE). Herein, the electrode was treated by casting hexacetyltrimethylammonium bromide on SPCE to promote a positively charged surface. Later, zirconium oxide was mixed with polyethylene glycol and the mixture was dropped cast onto the positively charged SPCE/CTAB. Tyrosinase was further immobilized onto the modified SPCE. Characterization of the prepared nanocomposite film and the modified SPCE surface was investigated by scanning electron microscopy (SEM), Electrochemical Impedance Spectroscopy (EIS), and Cyclic voltamogram (CV). The developed biosensor exhibits rapid response for less than 10 s. Two linear calibration curves towards phenol in the concentrations ranges of 0.075–10 µM and 10–55 µM with the detection limit of 0.034 µM were obtained. The biosensor shows high sensitivity and good storage stability for at least 30 days.

New trends in sample preparation techniques for environmental analysis

Environmental samples include a wide variety of complex matrices, with low concentrations of analytes and presence of several interferences. Sample preparation is a critical step and the main source of uncertainties in the analysis of environmental samples, and it is usually laborious, high cost, time consuming, and polluting. In this context, there is increasing interest in developing faster, cost-effective, and environmentally friendly sample preparation techniques. Recently, new methods have been developed and optimized in order to miniaturize extraction steps, to reduce solvent consumption or become solventless, and to automate systems. This review attempts to present an overview of the fundamentals, procedure, and application of the most recently developed sample preparation techniques for the extraction, cleanup, and concentration of organic pollutants from environmental samples. These techniques include: solid phase microextraction, on-line solid phase extraction, microextraction by packed sorbent, dispersive liquid-liquid microextraction, and QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe).

Optimization of dispersive liquid-liquid microextraction for preconcentration and spectrophotometric determination of phenols in Chabahar Bay seawater after derivatization with 4-aminoantipyrine

We have optimized dispersive liquid-liquid microextraction to preconcentrate trace phenolic compounds after derivatization with 4-aminoantipyrine in artificial sea water for spectrophotometric determination. Factors such as reaction time (7.5 min), pH (9.5), solvent (chloroform), dispersing solvent (ethanol), and volume ratio of dispersing to organic phase (11:1) were optimized. Under optimum conditions, the limit of detection was 0.18 μg/L and the linearity range 1-900 μg/L. The relative standard deviation and enrichment factor were 6% (n=7) and 920, respectively. The results demonstrate the efficiency of coupling the 5530 APHA standard for derivation and dispersive liquid-liquid microextraction of phenolic compounds from seawater samples. Using this method, total phenol content in seawater from several locations in Chabahar Bay (southeast Iran) was estimated at 27.8-74.8 μg/L.

Application of derivative and derivative ratio spectrophotometry to simultaneous trace determination of rhodamine B and rhodamine 6G after dispersive liquid-liquid microextraction

Two novel methods, first derivative spectrophotometric method ((1)D) and first derivative ratio spectrophotometric method ((1)DR), have been developed for the simultaneous trace determination of rhodamine B (RhB) and rhodamine 6G (Rh6G) in food samples after dispersive liquid-liquid microextraction (DLLME). The combination of derivative spectrophotometric techniques and DLLME procedure endows the presented methods with enhanced sensitivity and selectivity. Under optimum conditions, the linear calibration curves ranged from 5 to 450 ng mL(-1), with the correlation coefficients (r) of 0.9997 for RhB and 0.9977 for Rh6G by (1)D method, and 0.9987 for RhB and 0.9958 for Rh6G by (1)DR method, respectively. The calculated limits of detection (LODs) based on the variability of the blank solutions (S/N = 3 criterion) for 11 measurements were in the range of 0.48-1.93 ng mL(-1). The recoveries ranged from 88.1% to 111.6% (with RSD less than 4.4%) and 91.5-110.5% (with RSD less than 4.7%) for (1)D and (1)DR method, respectively. The influence of interfering substances such as foreign ions and food colorants which might be present in the food samples on the signals of RhB and Rh6G was examined. The developed methods have been successfully applied to the determination of RhB and Rh6G in black tea, red wine and chilli powder samples with the characteristics of simplicity, cost-effectiveness, environmental friendliness, and could be valuable for routine analysis.