Green Analytical Technique Research Articles

A novel green HPTLC method for simultaneous analysis of four antipsychotics in their pharmaceutical formulations: Assessment by Eco-scale

Implementing green analytical techniques has been one of the main objectives of the analytical chemistry community for the past two decades. The aim of transitioning to green analytical chemistry is to establish new methods environmentally benign instead of traditional methods. According to WHO, 20 million people worldwide are affected by schizophrenia, and 45 million people worldwide are affected by bipolar disorders. For that, in this work we develop a green HPTLC method to quantify simultaneously the four antipsychotics chloropromazine HCl, asenapine maleate, quetiapine fumarate and aripiprazole in pure form and tablet formulations. In this chromatographic method, separation was performed using silica gel 60 F254 HPTLC plates, the mobile phase composed of binary mixture of green solvents (ethanol : water (9 : 1 v/v)) which gave compact band with Rf values ranged between 0.14 to 0.70 for the drugs. The method was validated for linearity, accuracy, precision, selectivity and robustness according to ICH guidelines. It was assessed for greenness by analytical Eco-scale and compared with reported HPTLC methods for single analysis of these antipsychotics.

Near infrared spectroscopy and smartphone-based imaging as fast alternatives for the evaluation of the bioactive potential of freeze-dried açai

The development of green analytical techniques for food industry quality control has become an important issue in the context of the fourth industrial revolution. In this sense, near infrared spectroscopy (NIR) and smartphone-based imaging (SBI) were applied to evaluate the bioactive potential of freeze-dried açai pulps. For this purpose, reference results of ninety-six samples were obtained by determining total anthocyanins (TAC), polyphenol content (TPC), and antioxidant capacity (DPPH, ORAC and TEAC) by traditional methods and correlated to NIR spectra and SBI to build predictive models based on partial square least (PLS) regression. In summary, the NIR-PLS models showed better performance for predicting the TAC, TPC and antioxidant capacity of studied samples; considering the parameters of merit, such as coefficient of determination (0.8) and residual prediction deviation (RPD) (2.2) compared to the SBI-PLS models (0.7 and lower 1.5, respectively). The better performance of NIR-PLS could be potentially justified by a higher sensitivity of the NIR equipment than the smartphone images. In conclusion, these results show that the proposed alternative methods are promising tools for the future context of the 4.0 food industry.

High resolution and high throughput analytical methods for d-tagatose and process related impurities using capillary electrophoresis

d-tagatose is a low calorie multifunctional rare ketohexose sugar with sweetness similar to that of sucrose and it has high potential benefits for food and pharmaceutical industries. It is found in traces in some fruits as a natural component. In view of its high demand as a substitute for sugar, mass production of d-tagatose through enzymatic conversion of Lactose to d-tagatose is adopted. The existing HPLC method has limitations with respect sensitivity and resolution in quantification and monitoring of d-tagatose in the presence of its process related impurities. In the present investigation a new robust, fast and green analytical technique has been developed based on capillary electrophoresis (CE) for the separation and quantification of d-tagatose in presence of other sugars: Lactose, d-glucose, d-galactose and d-talose. Optimum conditions are found to be: Back Ground Electrolyte (BGE): 36 mM of Na2HPO4 and 130 mM of NaOH; pH: 12.6; voltage: +18 kV for high resolution and −18 kV for high throughput methods with direct UV-Detector at 265 nm. At these optimum conditions, good separation between the sugars is achieved in less than 20 min for high resolution and less than 4 min for high throughput methods. The developed methodology is validated as per ICHQ2R1 guide lines and successfully applied for monitoring d-tagatose during the enzymatic conversion of Lactose/d-galactose to d-tagatose and also to determine the unknown amounts of d-tagatose in crystallized samples and further, it is used in identifying the d-tagatose in fruits.

Laboratory-Scale Preparation and Characterization of Dried Extract of Muirapuama (Ptychopetalumolacoides Benth) by Green Analytical Techniques.

This work reports on the preparation of a drying process from the ethanolic extract of Muirapuama and its characterization through green analytical techniques. The spray-drying processes were performed by using ethanolic extract in a ratio of 1:1 extract/excipient and 32 factorial design. The properties of dried powder were investigated in terms of total flavonoid content, moisture content, powder yield, and particle size distribution. An analytical eco-scale was applied to assess the greenness of the developed protocol. Ultra-high performance liquid chromatography (UHPLC)with reduced solvent consumption in the analysis was compared to the conventional HPLC method. A Fourier transform near-infrared (FT-NIR) spectroscopic method was applied based on the principal component scores for the prediction of extract/excipient mixtures and partial least squares regression model for quantitative analysis. NIR spectroscopy is an economic, powerful, and fast methodology for the detection of excipient in muirapuama dried extracts, generating no residue in the analysis. Scanning electron microscopy (SEM) images showed samples with a higher concentration of excipient, presenting better morphological characteristics and a lower moisture absorption rate. An eco-scale score value of 85 was achieved for UHPLC and 100 was achieved for NIR (excellent green analysis). Above all, these methods are rapid and green for the routine analysis of herbal medicines based on dried extracts.

FTIR combined with chemometric tools (fingerprinting spectroscopy) in comparison to HPLC: which strategy offers more opportunities as a green analytical chemistry technique for pharmaceutical analysis.

Fourier transform infrared spectroscopy (FTIR) is a widespread technique that can provide a chemical signature (fingerprints) of solid, liquid, or gas samples with a wide range of analytical applications. High-performance liquid chromatography (HPLC) is a leading analytical strategy for pharmaceutical analysis. Here we present a side-by-side comparison of the potential of these techniques for quantitative analysis of pharmaceutical active ingredient combinations in light of green analytical chemistry (GAC) principles. The methods were successfully applied for the analysis of ketoprofen (KTP)/hyoscine (HYS) and benzocaine (BENZ)/dextromethorphan HBr (DEX) in their binary mixtures and pharmaceutical preparations. In FTIR analysis, calibration models were constructed based on partial least squares regression (PLSR) with satisfactory regression coefficients (r2) of 0.9998, 0.9994, 0.9855, and 0.9895 for KTP, HYS, DEX, and BENZ, respectively, over a wide linearity range (10-100, 10-100, 5-75, and 10-100 μg mL-1) that covers the concentration ratios in the market samples. External validation using a validation set and internal validation using leave-one-out-cross-validation calculations were performed, and small root-mean-square-error-of-cross-validation (RMSECV) values were obtained indicating the good resolving power of the models. The same performance was obtained using the HPLC method for separation of the same mixtures with r2 equal to 0.9998, 0.9999, 0.9998, and 0.9998 over linear ranges of 50-1000, 10-200, 5-100, and 5-100 μg mL-1 for KTP, HYS, DEX, and BENZ, respectively. The HPLC methods were validated following ICH guidelines with good recovery percentages in the range of 98-100%. The statistical comparison of the FTIR and HPLC methods for analysis showed almost the same results with good applicability towards commercial dosage forms. Concerning the twelve GAC principles, a detailed comparison was performed to highlight the opportunities of each technique. FTIR-PLSR analysis showed superior performance as it allows for less solvent consumption, portability, less generated waste, short operating time, less operation cost, less energy consumption, and more operator safety and it is easily coupled with chemometric tools. Besides, FTIR is a direct analytical technique that can be used for the analysis of samples in all the physical forms (solid, liquid, and gas) without modifications.

Electrochemically Fabricated Solid Phase Microextraction Fibers and Their Applications in Food, Environmental and Clinical Analysis

Background:Designing an analytical methodology for complicated matrices, such as biological and environmental samples, is difficult since the sample preparation procedure is the most demanding step affecting the whole analytical process. Nowadays, this step has become more challenging by the legislations and environmental concerns since it is a prerequisite to eliminate or minimize the use of hazardous substances in traditional procedures by replacing with green techniques suitable for the sample matrix.Methods:In addition to the matrix, the nature of the analyte also influence the ease of creating green analytical techniques. Recent developments in the chemical analysis provide us new methodologies introducing microextraction techniques and among them, solid phase microextraction (SPME) has emerged as a simple, fast, low cost, reliable and portable sample preparation technique that minimizes solvent consumption.Results:The use of home-made fibers is popular in the last two decades since the selectivity can be tuned by changing the surface characteristics through chemical and electrochemical modifications. Latter technique is preferred since the electroactive polymers can be coated onto the fiber under controlled electrochemical conditions and the film thicknesses can be adjusted by simply changing the deposition parameters. Thermal resistance and mechanical strength can be readily increased by incorporating different dopant ions into the polymeric structure and selectivity can be tuned by inserting functional groups and nanostructures. A vast number of analytes with wide range of polarities extracted by this means can be determined with a suitable chromatographic detector coupled to the system. Therefore, the main task is to improve the physicochemical properties of the fiber along with the extraction efficiency and selectivity towards the various analytes by adjusting the electrochemical preparation conditions.Conclusion:This review covers the fine tuning conditions practiced in electrochemical preparation of SPME fibers and in-tube systems and their applications in environmental, food and clinical analysis.

Determination of polybrominated diphenyl ethers in milk samples. Development of green extraction coupled techniques for sample preparation

Ultrasound-assisted extraction (UAE), cloud point extraction (CPE), and ultrasound back-extraction (UABE) techniques have been coupled for lixiviation, preconcentration, and cleanup of polybrominated diphenyl ethers (PBDEs) from milk samples for determination by gas chromatography-electron capture detection (GC-ECD). Physicochemical parameters that affect the efficiency of the extraction system were investigated using a design of experiments based on multivariate statistical tools, and considering the sample matrix along the development. The coupling of the leaching step, UAE, enhanced ca. 3.5 times the extraction efficiency of the former sample preparation methodology (CPE-UABE) leading to cleaner sample extracts suitable for GC analysis. Under optimum conditions, the proposed methodology exhibits successful performance in terms of linearity and precision, with recoveries in the range of 68-70% and LODs within the range 0.05-0.5 ng/g dry weight (d.w.). The proposed sample preparation methodology coupled three green analytical techniques. It expands the application frontiers of CPE for the analysis of biological samples by GC. The optimized methodology was used for determination of PBDEs in powder milk samples, from both commercial and human sources.

Modern Safety Control for Meat Products: Near Infrared Spectroscopy Utilised for Detection of Contaminations and Adulterations of Premium Veal Products

This article gives insights into the development of a modern “green analytical technique” based on near infrared (NIR) spectroscopy to detect harmful frauds or accidental contaminations with pork and pork fat in processed veal products. A project carried out at the Institute of Analytical Chemistry and Radiochemistry of the University of Innsbruck led to promising results in the field of food safety and control. The aim of the project was to develop quick and reliable methods for different fields of application based on non-destructive NIR spectroscopy. In this connection, three specialised techniques were successfully developed, each using an individual instrumental setup and data evaluation process. Methods suited for accurate laboratory measurements (benchtop instrument), ready for in- and at-line applications or high-throughput-analyses (utilising a fibre optic probe) and a method characterised by flexibility and user friendliness with the ability to perform on-site analyses (handheld spectrometer) were developed within the scope of this project. It was possible to detect contamination with pork as well as contamination with pork fat from 50% w/w down to 10% w/w in handmade veal sausages. Satisfying results were achieved even for additional measurements in which spectra were recorded directly through a polymer packaging. A limit of detection of 3% w/w was found for analyses of pure minced veal samples contaminated with pork.

Determination of Mercury in Environmental Samples by Using Water Exchangeable Liquid-Liquid Microextraction as Green Extraction Method Couple with Cold Vapor Technique

This is a green method for determination of mercury ion (Hg2+) in environmental samples. The method of exchangeable water based on liquid-liquid microextraction (EW-LLME) was first time introduced as a green analytical separation technique. Exchangeable water was made by the reaction of carbon dioxide with diethylenetriamine. The exchanging phenomena from low polarity to high polarity were confirmed by Fourier transforms infrared spectrometry. The complex formation between Hg2+ and 1, 5-diphenylcarbazone was achieved under the optimized experimental conditions. The enrichment factor and limits of detection of the present method were obtained to be 45.2 and 0.5 ng L−1, respectively. The accuracy of the present method was confirmed with certified reference materials. The EW-LLME was successfully applied for determination of Hg2+ in solid matrices of block-III and V of Thar coalfield.

Green sample preparation of complex matrices: towards sustainable separations of organic compounds based on the biorefinery concept

AbstractThe development and application of green analytical techniques aiming at the sample preparation of complex matrices for the study of organic compounds have been growing considerably over the last 15 years. Miniaturisation, automation and solventless techniques are gaining importance in this field, associated to others, as is the case of metrics. However, the unreflected use of the so-called green analytical techniques “might lead to doing the same things better, rather than rethinking solutions altogether”. Some limits and potentialities of the green sample preparation towards sustainable separations of organic compounds using the biorefinery concept will be also discussed in this paper, a promising biobased route that can integrate sustainable extraction and purification processes in a whole complete circular unity.

Highly selective enrichment of baicalin in rat plasma by boronic acid-functionalized core–shell magnetic microspheres: Validation and application to a pharmacokinetic study

To the best of our knowledge, this study is the first to successfully apply a novel, highly selective enrichment technique based on boronic acid-functionalized core–shell magnetic microspheres (BA-Fe3O4@SiO2–Au@mSiO2) with a large surface area and uniform pore size, to determine the baicalin concentration in rat plasma by HPLC. By taking advantage of the special interaction between boronic acid and baicalin under alkaline conditions, as well as the microspheres' size exclusion ability, baicalin was selectively extracted from protein-rich biosamples, such as plasma, without any other pretreatment procedure except for a 10-min vortexing step. BA-Fe3O4@SiO2–Au@mSiO2 microsphere-adsorbed baicalin was straightforwardly and rapidly isolated from the matrix using a magnet. Baicalin was subsequently eluted from the microspheres under acidic conditions for 2min for further HPLC analysis. The extraction conditions, such as the amount of microspheres added, adsorption time, adsorption pH, and elution time and pH, were also determined. Furthermore, method validation, including the linear range, detection limit, precision, accuracy, and recovery, were determined. This newly developed method based on BA-Fe3O4@SiO2–Au@mSiO2 microspheres is a simple, accurate, selective, and green analytical preparatory technique for analyzing baicalin in rat plasma. This study will be further novel research on the analysis of complex plasma samples and the pharmacokinetics of drugs similar to baicalin.

Microwave-Assisted Ionic Liquid Extraction of n-Alkanes and Isoprenoid Hydrocarbons from Petroleum Source Rock

Microwave-assisted ionic liquid extraction (MAILE) has been investigated for the extraction of n-alkanes and isoprenoid hydrocarbons from petroleum source rock and the conditions for maximum yield of the analytes were determined. An aqueous solution of an ionic liquid, 1-butyl-3-methylimidazolium bromide (BmimBr), was employed as the extracting medium. The results showed that the concentration of ionic liquid, extraction time and extraction temperatures have effects on extraction yields of aliphatic hydrocarbons with optimal conditions at: 3.0 mol L−1 ionic liquid solution, 30 min and 120 °C, respectively. The extraction yields of all the n-alkanes and acyclic isoprenoid hydrocarbons were much higher using microwave-assisted ionic liquid extraction than with Soxhlet extraction and accelerated solvent extraction. There were good correlations of the diagnostic geochemical ratios calculated from the gas chromatographic (GC) data of MAILE, Soxhlet extraction and accelerated solvent extraction. The results of this study show that MAILE is an efficient and green analytical preparatory technique for geochemical evaluation of petroleum source rock.

Separation of 97Ru from niobium target using PEG based aqueous biphasic systems

Separation of no-carrier-added (NCA) 97Ru from bulk niobium target has been carried out for the first time using green analytical technique, aqueous biphasic system. 50 % (w/v) polyethylene glycol (PEG)-4000, against 2 M solutions of various salts such as Na-citrate, Na-tartarate, Na-malonate, Na2CO3, NaHSO3, Na2SO4, Na2S2O3 K2HPO4, K3PO4, K2CO3 and 4 M KOH were employed at room temperature for the extraction of NCA 97Ru from bulk niobium. Influence of molecular weight of PEG rich phase as well as pH of some salt rich phase (e.g., Na-tartarate) on the extraction behaviour of NCA 97Ru into PEG rich phase was also observed. In the presence of sodium-tartarate salt solution, when volume of PEG-4000: Na-tartarate was 3:1, 91 % of NCA 97Ru was extracted into the PEG rich phase without any contamination of niobium target. Dialysis of PEG rich phase containing NCA 97Ru was carried out against deionised water to obtained pure NCA 97Ru.

Electrochemical arsine generators for arsenic determination.

Arsine generation is the gateway for several sensitive and selective methods of As determination. An electrochemical arsine generator (EAG) is especially green: we report here the use of two electrode materials, aluminum and highly oriented (ordered) pyrolytic graphite (HOPG) never before used for this purpose. The first is operated on a novel constant voltage mode: current flows only when the sample, deliberately made highly conductive with acid, is injected. As a result, the cathode, despite being a highly active metal that will self-corrode in acid, lasts a long time. This EAG can be made to respond to As(III) and As(V) in an equivalent fashion and is fabricated with two readily available chromatographic T-fittings. It permits the use of a wire roll as the cathode, permitting rapid renewal of the electrode. The HOPG-based EAG is easily constructed from ion chromatography suppressor shells and can convert As(III) to AsH3 quantitatively but has significantly lower response to As(V); this difference can be exploited for speciation. The success of Al, an active metal, also dispels the maxim that metals with high hydrogen overpotential are best for electrochemical hydride generation. We report construction, operation, and performance details of these EAGs. Using gas phase chemiluminescence (GPCL) with ozone as a complementary green analytical technique, we demonstrate attractive limits of detection (LODs) (S/N = 3) of 1.9 and 1.0 μg/L As(V) and As(III) for the HOPG-based EAG and 1.4 μg/L As(V) or As(III) for the Al-based EAG, respectively. Precision at the ~20 μg/L As(V) level was 2.4% and 2.1% relative standard deviation (RSD) for HOPG- and Al-based EAGs, respectively. Both HOPG- and Al-based EAGs permitted a sample throughput of 12/h. For groundwater samples from West Texas and West Bengal, India, very comparable results were obtained with parallel measurements by induction coupled plasma-mass spectrometry.

Surfactant–Solvent-Based Quaternary Component Emulsification Microextraction Followed by High-Performance Liquid Chromatography for the Simultaneous Analysis of Benzimidazole Anthelmintics in Milk Samples

A simple surfactant-solvent-based quaternary component emulsification microextraction (SSEME) method combined with high-performance liquid chromatography–photodiode array detection has been developed for the extraction, preconcentration, and determination of four benzimidazole anthelmintic (i.e., oxfendazole, mebendazole, albendazole, and fenbendazole) residues in milk samples. The quaternary component solvent of SSEME carried out in 10 mL aqueous solution were Triton X-114 (emulsifier or carrier), acetonitrile (disperser solvent), and 1-octanol (extraction solvent). The surfactant has an important role in the enhancement of the extraction efficiency of the high polar analytes. For milk sample analyses, linearity was obtained in the range of 10–200 μg/L with the determination coefficients (R2) higher than 0.996. Preconcentration factor was obtained in the range of 21–38, corresponding to limits of detection in the range of 2.6–9.9 μg/L. Intra-day (n = 6) and inter-day (n = 6 × 3) precisions in the sample studied were obtained with relative standard deviation below 8.8 %. The recoveries for the spiked target anthelmintics at different concentrations (25, 50, 100, and 150 μg/L) were obtained in the range 80.1–114.1 %. The proposed SSEME method has been demonstrated that is simple, effective, and reliable for the analysis of analytes in the samples studied and can be used as an alternative green analytical technique for benzimidazole analysis.

Infrared-assisted non-ionic surfactant extraction as a green analytical preparatory technique for the rapid extraction and pre-concentration of picroside I and picroside II from Picrorhiza scrophulariiflora Pennell

The extraction of picroside I and picroside II from Picrorhiza scrophulariiflora Pennell using non-ionic surfactants with the assistance of infrared was investigated and the conditions for maximum yield were determined. Under optimum conditions, i.e. 10% Genapol X-080 (v/v), liquid : solid ratio of 150 : 1 (mL g−1), infrared power 200 W and infrared-assisted extraction for 4 min, the extraction yield reached the highest value. For the preconcentration of picroside I and picroside II by cloud-point extraction, the solution was incubated in a thermostatic water bath at 100 °C for 10 min, and 15% NaCl (w/v) was added to the solution to facilitate the phase separation. When compared with various polar and nonpolar solvents (pure water, ethanol, acetone, acetic ether and hexane), the extraction efficiency of 10% Genapol X-080 reached a statistically higher value (p < 0.05). By using an infrared-assisted non-ionic surfactant extraction method, the determined amounts of the picrosides in Picrorhiza scrophulariiflora Pennell were statistically higher than those extracted with conventional ultrasound-assisted extraction and heat-reflux extraction (p < 0.05). The results show that infrared-assisted non-ionic surfactant extraction is a good, efficient and green analytical preparatory technique for the rapid extraction and pre-concentration of pharmacologically active ingredients from Picrorhiza scrophulariiflora Pennell without disturbing the subsequent chromatographic analysis.

Ionic liquid-based magnetic solid phase extraction coupled with inductively coupled plasma-optical emission spectrometry for the determination of Cu, Cd, and Zn in biological samples

Ionic liquids of methyltrioctylammonium chloride modified magnetic nanoparticles were prepared, and a new method of magnetic solid phase extraction combined with inductively coupled plasma-optical emission spectrometry was established for the determination of Cu, Zn, and Cd in human hair and urine samples. The effect of pH on the extraction of Cu, Zn, and Cd was investigated. The results show that the ionic liquid played a key role in the extraction of target analytes. The magnetic nanoparticles served as the carriers of the ionic liquid and the base of the phase separation. Several parameters affecting the extraction and desorption of the target analytes were investigated including the sample volume, extraction time, eluent concentration and volume, desorption time, sedimentation time, amount of the ionic liquid and Fe3O4@Si–OH, and the optimized conditions were established. Under the optimized conditions, the detection limits of Cu, Zn, and Cd were 0.54, 0.56, and 0.33 μg L−1, respectively, and the relative standard deviations (n = 7) were 4.9% (c = 2 μg L−1), 3.7% (c = 2 μg L−1), and 5.1% (c = 1 μg L−1), respectively. To validate the accuracy of the proposed method, it was applied to analyze certified reference materials of GBW07601 human hair and GBW09103 human urine. The determined values agree with the certified values. The developed method was also employed to analyze human hair and urine, and the recoveries for the spiked samples were in the range of 89.1% to 120%. The developed method was simple, highly sensitive, solvent-free, chelate-free, and could be considered as a green analytical technique.

A new approach to sample preparation for the determination of trace metals in petroleum source rocks

The dissolution and extraction of petroleum source rocks using a nonionic surfactant to determine their trace metal (V, Ni, Co, Mn, and Mo) content with the assistance of microwave irradiation were investigated and the conditions for obtaining the optimum yield were determined. A complementary microwave-assisted acid dissolution method was also optimized. The results showed that the temperature and time have significant effects on yields of the trace metals. Factors such as surfactant concentration and sample/solvent ratio had little influence on the digestion and extraction efficiencies for these metals. The optimum temperature for microwave-assisted nonionic surfactant dissolution of petroleum source rocks for trace metal determination was 200 °C and the best yields of the metals were obtained in 40 min. The optimum temperature and time for nonionic surfactant extraction of trace metals from petroleum source rocks were 90 °C and 45 min, respectively. The microwave-assisted acid digestion gave optimum yields of the trace metals in 70 min. The new nonionic surfactant digestion and extraction methods showed efficiencies comparable to those afforded by using the acid digestion method for three out of five elements determined in this study, although the recoveries of vanadium and manganese were relatively low, but the reduction of the digestion/extraction time and environmentally friendliness of the new nonionic surfactant based methods are clear advantages. The new method showed a very good reproducibility. The results of this study also show that the microwave-assisted nonionic surfactant digestion method is a good, efficient and better alternative green analytical preparatory technique for the determination of some trace metals in petroleum source rocks.

Green Bioanalysis: Some Innovative Ideas Towards Green Analytical Techniques

The key target of green chemistry is to make compounds and materials available to mankind, while causing no harm to the environment. In the 21st century analytical scientists are more concerned about green analytical method development. The number of literatures on green chemistry has undergone a dramatic increase in the new millennium. Green bioanalytical techniques aim to minimize or eliminate the hazardous waste associated with bioanalytical methods. An efficient and sincere approach towards bioanalytical method development has an enormous contribution towards green analysis. The selection of organic constituents of the mobile phase, choice of sample extraction process, adoption of an appropriate separation procedure and a few others, control the green chemistry approach of the bioanalytical method. In routine practice, UHPLC-MS can be the most suitable approach, while supercritical fluid chromatography is one of the best available techniques for green bioanalytical methods. Nevertheless, there always remains great scope of further research on green bioanalytical methods.

HF-LPME as a green alternative for the preconcentration of nickel in natural waters

In the last years, some analytical methodologies have been identified as a source of pollution, receiving increasing attention to decrease their impact on the environment. In this sense, the so-called solvent-less methodologies appear as a green alternative to reduce the volume of solvents used in many sample treatment procedures and, consequently, the volume of toxic wastes produced. Among these techniques, analytical methodologies based on liquid-phase microextraction are being continuously developed, although most applications are focused on organic compounds. In this work, a three-phase hollow-fibre liquid-phase microextraction (HF-LPME) system has been developed for the preconcentration of nickel in natural waters, prior to the analysis by atomic absorption spectrometry. Under optimum conditions, the new system allowed an enrichment factor of 29.80 to be obtained after 60 min of experiment, and it was successfully applied to the determination of nickel in both saline and non-saline water samples, at ppb and ppt levels. The results were compared with those obtained using a well-established methodology based on liquid solvent extraction showing no significant differences (α = 0.05) between both values. In addition, the new HF-LPME presents the advantages of a green analytical technique, as its greenness profile shows, with the additional reduction of sample manipulation and time cost.