Solid-surface Fluorescence Research Articles

Determination of Lead in Bee Products by Solid Surface Fluorescence Using Complexation and Coacervation at Room Temperature Processes. An Environmental Friendly Methodology.

An accurate, economic and green methodology for Pb(II) monitoring in bee products is proposed. Complexed metal traces were preconcentrated on Nylon membranes using the coacervation phenomenon based on room temperature reaction between the cationic surfactant hexadecyltrimethylammonium bromide and the bile salt sodium cholate. The increase in solid surface fluorescence signal of dyes 8-hydroxyquinoleine and o-phenanthroline due to Pb(II) presence was used for the metal quantification. Experimental variables that influence on preconcentration step and fluorimetric sensitivity were optimized using uni-varied assays. Pb(II) concentration was determined on membranes by solid surface fluorescence at λem = 470nm (λexc = 445nm), using a solid sample holder. The calibration at optimal experimental conditions showed a LOD of 4.2 × 10-4mg Kg-1 with a linear range of 1.28 × 10-3mg Kg-1 to 8.73mg Kg-1 and was successfully applied to Pb(II) quantification in different bee products produced in central west region of Argentina. The proposed methodology was applied to all samples after appropriate dilution. Accuracy methodology was evaluated by comparison of the obtained results with those found by ICP-MS, with percentage relative error under 8%. The precision was better than 0.0344 CV for Pb(II) determination.

A solid-surface fluorescence study of Rhodamine B and fluorescein adsorbed onto a filter paper, and semi-quantitative determination using EEM data

A solid-surface fluorescence study of Rhodamine B and fluorescein adsorbed onto a filter paper, and semi-quantitative determination using EEM data

Surfactant coated silver nanoparticles as manganese fluorescent sensor. Manganese quantification in argentinian wines

A number of red, white, rose and blend wines from vineyards of the west region of Argentina were analyzed for Mn(II) traces quantification by solid surface fluorescence using silver nanoparticles as sensors. Nanoparticles were synthesized and coated with sodium dodecylsulphate by sonochemical procedure, characterized in composition and size; they are proposed as nanosensor for the Mn(II) quantification. Experimental variables that influence on analytical quality of synthesis, sorption and determination steps were studied and optimized. Thanks to the implementation of solid phase extraction procedure on filter paper with a determination step by solid surface fluorescence, an adequate tolerance to foreign species was obtained. At optimal experimental conditions (λem = 502 nm; λεxc = 460 nm; Filter paper Blue Ribbon with Sodium Dodecyl Sulfate coated Silver Nanoparticles; pH 8.0 employed phosphate buffer at concentration 2.5 × 10−4 mol/L), a limit of detection of 0.064 µg/L and a limit of quantification of 0.194 µg/L were reached. The new methodology was successfully applied to analyte determination in the 17 argentinian wines including Cabernet Sauvignon, Malbec, Tempranillo, Tocai, Viognier, Chardonnay, Sauvignon Blanc, Tannat, Malbec and Pinot strains. Recovery studies showed values near to 100% being validated by ICP-MS.

Copper Traces Quantification in Bee's Products by Solid Surface Fluorescence. A Green Analytical Proposal.

A new methodology based on the fluorescence of Cu(II) ternary system with o-phenanthroline (o-Phen) and eosin (Eo) dyes is proposed. The metal was selectively retained on Nylon membranes and the solid surface fluorescence (SSF) was used for anayte quantification. Experimental variables that influence the formation of Cu(II)-o-Phen-eo system and retention step were studied and optimized. At optimal experimental conditions, an adequate tolerance to foreign species was shown with a LOD of 1.18ng L-1 and a LOQ of 3.57ng L-1. The methodology was evaluated for their greenness profile and successfully applied to analyte determination in bee's products of West-Center Argentina. Recovery studies showed values near to 100% being satisfactorily validated by ICP-MS.

An eco-friendly MIP-solid surface fluorescence immunosensor for detection of CA 19-9 tumor marker using Ni nanocluster as an emitter labels

In the present study, an eco-friendly solid surface fluorescence immunosensor was fabricated for the ultra-selective and sensitive determination of CA 19-9 antigen based on polydopamine (PDA) molecular imprinted polymer (MIP) as an antibody substitution and Ni nanoclusters (Ni NCs) as the fluorescent signal probe. Here, the uniform MIP film for CA 19-9 antigen was established by electropolymerization of DA and target antigen on the surface of ITO electrode. When the imprinted cavities were occupied by CA 19-9 antigen and Ni NCs-Ab, respectively, the fluorescence emission of Ni NCs on the MIP-modified electrode surface was increased. Actually, MIP has been used in immunoassays as antibody substitute. Under optimized experimental conditions, taking advantage of both MIP-FL assays, the proposed immunosensor demonstrated a good analytical performance for the CA 19-9 antigen detection in an excellent linear range from 1 pg mL−1 to 48 ng mL−1 with detection limit of 0.13 pg mL−1 (S/N = 3). The application of the proposed MIP-FL immunosensor for detection of CA 19-9 antigen in human serum samples was evaluated, and the obtained results were found to be in acceptable agreement with those obtained with an ELISA assay as standard method. The developed fluorescence immunosensor demonstrated high specificity and can provide a simple, sensitive and reliable approach for the ultra-trace detection of other tumor markers in clinical monitoring.

Film polysaccharide matrices for immobilization of hydrophilic fluorescence probes

The selection of a suitable matrix for immobilizing a reagent is one of the key issues in the development of a luminescent chemosensor. Various polysaccharide matrices from cellulose, cellulose nitrate, cellulose diacetate, chitosan and its acrylic copolymers have been investigated as a platform for immobilizing fluorescent probes (eosin Y and tripaflavin) for using in optical chemosensors. The parameters of the dyes sorption from aqueous solutions on the matrices were determined. Matrices with high signals of solid-surface fluorescence of the probes were revealed. A film matrix made of cellulose diacetate was shown to be the most promising sorbent for tripaflavine. A composite matrix based on chitosan and cellulose and a matrix made of chitosan modified with formic acid were the best for eosin immobilization. The developed sensitive elements (matrix ​+ ​dye) can be used to design optical chemosensors.

New Analytical Methodology for Sb(III) Traces Quantification as Emergent Contaminant in Drinks Packaged PET Samples by Solid Surface Fluorescence

Emerging contaminants constitute a set of substances that are released into the environment for which regulations are currently not established for their environmental monitoring, being antimony one of them. A new methodology for Sb(III) traces monitoring by solid surface fluorescence is proposed. The metal was complexed with alizarine (Az) as fluorosphore reagent in alcaline medium in presence of the bile salt sodium cholate. To isolate the analyte of matrix constituents, a preconcentration/separation strategy on filter paper was introduced prior to determination step. The solid surface fluorescence was measured λem = 450 nm and λexc = 363 nm using a solid sampler holder. Under optimal conditions, the limits of detection and quantification of proposed methodology were 0.08 and 0.24 μg·L-1, respectively, showing a linear range from 0.24 to 304.4 μg·L-1 with good sensitivity and adequate selectivity. It was applied to the Sb(III) traces determination present in drinking water and beverages samples packaged in polyethylene terephthalate (PET) bottles widely consumed in Argentina. The combination of a preconcentration step on common filter paper and the inherent sensitivity of photoluminescent methods have permitted to achieve sensitivity similar to atomic spectroscopies using a lower price instrument typical in control laboratories. Precision and accuracy were tested with excellent agreement. Results were truenessed by ETAAS with satisfactory concordance.

Comparative study of antimony exposition by cigarettes and alternatives of tobacco consumption

A comparative study of Sb(III) exposition is presented. The determination of trace amounts of Sb(III) present in tobacco samples (tobacco of conventional cigarettes, refill solutions for e-cigarettes, snuff used in water pipe, snus and dry rapé) has been realized by solid surface fluorescence using alizarin as fluorogenic reagent (λem = 450 nm, λexc = 363 nm). In a first step, a chemisorption on filter paper was carried out with the bile salt sodium cholate (pH 10.2). In these conditions, the metal was selectively retained on the solid support preventing the spectral interferences of the complex matrix. The calibration graphs resulted linear in the range of 0.24 to 304.4 μg L−1 with detection limit of 0.08 μg L−1 (S/N = 3.3). Results were truenessed by ETAAS with adequate agreement. The results will be used in prevention workshops for the purpose to provide scientific evidence to serve young people to make a correct decision respect the tobacco consumption.

Solvent Effect on the Solid-Surface Fluorescence of Pyrene on Cellulose Diacetate Matrices

The effect of the solvent nature (acetonitrile, ethanol, dimethyl sulfoxide, and dioxane) and its concentration on the fluorescence intensity of pyrene sorbed on the cellulose diacetate (CDA) film from a water-organic solution was studied. Dimethyl sulfoxide and ethanol are shown to be the most effective solvent additives for pyrene solid-surface fluorescence (SSF). The maximum SSF signal of pyrene was found upon sorption of the substance from aqueous media containing 1.2-4.2 vol% DMSO. For the pyrene quantitation the concentration dependence of its SSF intensity at the maximum of the spectrum at λem = 394 nm and λexp = 320 nm was plotted. The dependence has a linear character in the pyrene concentration range 2·10−6 - 2·10-8 g/L, and the limit of pyrene detection is 2·10-11 g/L. The possibility of determining benzo(a)pyrene using SSF technique with the CDA matrix is proved. The proposed method is promising for use in environmental monitoring of polycyclic aromatic hydrocarbons.

Metsulfuron-methyl determination in environmental samples by solid surface fluorescence

A new environmental friendly methodology for metsulfuron-methyl quantification based on the fluorescent signal enhancement of rhodamine B dye has been developed. A cationic surfactant (cetyltrimethylammonium bromide, CTAB) and an anionic one (sodium dodecylsulfate) were employed to preconcentrate the herbicide using a coacervation phenomenon, in sodium borate buffer medium (pH9.2). The coacervate phase was collected on a nylon membrane (0.45μm) and the solid surface fluorescence signal was determined (λexc=515nm, λem=565nm). Experimental variables that influence on preconcentration step and fluorimetric sensitivity have been studied and optimized using response surface methodology. Under optimal working conditions, a LOD of 0.17μgL−1 and a LOQ 0.53μgL−1 was obtained. The zeroth order regression calibration was linear from 0.53 to 5.00μgL−1. The method showed adequate sensitivity and selectivity, and was applied to the determination of trace amounts of metsulfuron-methyl in environmental water samples. The proposed methodology implies an alternative to traditional techniques for metsulfuron-methyl monitoring using an accessible instrument in control laboratories, representing a contribution in the toxicological and environmental areas for the monitoring of MSM in environmental samples, in agreement with the Green Chemistry.

Green Photoluminescent Methodology for Aluminium Traces Quantification in 24-Hour Urine of Subjects with Different Exposition to Tobacco Smoke

The aim of this work has been to evaluate the aluminium (Al(III)) traces contents in 24-hour urine samples from subjects with different tobacco smoke expositions using a new methodology with 1,4-dihydroxy-9, 10-anthraquinone (Quinizarine, QZ) as a fluorosphore. Biological samples were tested using commercial reagent strips and clinical parameters. Al(III) was determined complexing with QZ followed by a solid phase extraction step using Nylon membranes as a solid support. The analyte was subsequently quantified by solid surface fluorescence (SSF, λem= 573, λexc= 490) with a detection limit of 0.88 μg L-1 and quantification limit of 2.69 μg L-1. The calibration curve was linear from 2.69 to 499.13 μg L-1 Al(III) (R2 = 0.9973). Urine samples were successfully analysed with an average recovery close to 100%. Solid phase extraction step showed efficacy to eliminate foreign ions and the highly fluorescent matrix own of urine. Results were validated by electrothermal atomic absorption spectrometry (ETAAS) with an adequate concordance. The new methodology has low operation cost with simple instrumentation and without organic solvent.

Solid surface fluorescence methodology for fast monitoring of 2,4-dichlorophenoxyacetic acid in seed samples

A new method for pre-concentration/separation and determination of 2,4-dichlorophenoxyacetic acid (2,4-D) by solid-surface fluorescence (SSF) is proposed. The herbicide was complexed with Rhodamine B at pH7.0 in the presence of phosphate buffer and anionic surfactant admicelles. A Nylon membrane was selected as a solid support for SSF measurement and the presence of 2,4-D was evident by the RhB quenching effect. Under optimal experimental conditions, the limit of detection and quantification were 6.93 and 21ngL−1, respectively, and the linear range was obtained from 0.021 to 22.11μgL−1 2,4-D concentration. The developed methodology showed good sensitivity and adequate selectivity, and it was applied to the 2,4-D determination in seed samples. The SSF represents a simple and fast alternative to conventional methods of analysis, employing an existing instrument in most laboratories.

Acriflavine-immobilized eggshell membrane as a new solid-state biosensor for Sudan I–IV detection based on fluorescence resonance energy transfer

A novel solid-surface fluorescence biosensor for rapid detection of Sudan I–IV was proposed based on fluorescence resonance energy transfer (FRET). The biosensor was fabricated by immobilizing acriflavine (AY) on the eggshell membrane (ESM) with glutaraldehyde as cross-linking agent. FRET mechanism was demonstrated by using AY and Sudan dyes as donor and acceptor respectively, an efficient energy transfer in the present system was indicated by the sufficient spectral overlap integral (J) and proper Förster critical distance (R0). Under optimum conditions, the fluorescence of the AY-ESM could be efficiently quenched by Sudan I–IV and the corresponding linear range was 0.5–60μM with the detection limits (3σ/slope) of 0.16, 0.26, 0.21 and 0.17μM respectively. Compared to the detection of Sudan dyes in solution-state, the membrane biosensor exhibited advantages of low detection limits, high sensitivity and selectivity, as well as excellent stability. Recovery tests in spiked real samples also achieved satisfactory results.

Sequential determination of nickel and cadmium in tobacco, molasses and refill solutions for e-cigarettes samples by molecular fluorescence

In this work, a new procedure was developed for separation and preconcentration of nickel(II) and cadmium(II) in several and varied tobacco samples. Tobacco samples were selected considering the main products consumed by segments of the population, in particular the age (youth) and lifestyle of the consumer. To guarantee representative samples, a randomized strategy of sampling was used. In the first step, a chemofiltration on nylon membrane is carried out employing eosin (Eo) and carbon nanotubes dispersed in sodium dodecylsulfate (SDS) solution (phosphate buffer pH 7). In this condition, Ni(II) was selectively retained on the solid support. After that, the filtrate liquid with Cd(II) was re-conditioned with acetic acid /acetate buffer solution (pH 5) and followed by detection. A spectrofluorimetric determination of both metals was carried out, on the solid support and the filtered aqueous solution, for Ni(II) and Cd(II), respectively. The solid surface fluorescence (SSF) determination was performed at λem = 545nm (λex = 515nm) for Ni(II)-Eo complex and the fluorescence of Cd(II)-Eo was quantified in aqueous solution using λem = 565nm (λex = 540nm). The calibration graphs resulted linear in a range of 0.058–29.35μgL−1 for Ni(II) and 0.124–56.20μgL−1 for Cd(II), with detection limits of 0.019 and 0.041μgL−1 (S/N = 3). The developed methodology shows good sensitivity and adequate selectivity, and it was successfully applied to the determination of trace amounts of nickel and cadmium present in tobacco samples (refill solutions for e-cigarettes, snuff used in narguille (molasses) and traditional tobacco) with satisfactory results. The new methodology was validated by ICP-MS with adequate agreement. The proposed methodology represents a novel fluorescence application to Ni(II) and Cd(II) quantification with sensitivity and accuracy similar to atomic spectroscopies, introducing for the first time the quenching effect on SSF.

Direct solid surface fluorescence spectroscopy of standard chemicals and humic acid in ternary system

The front face fluorescence spectroscopy is often used to quantify chemicals in well-known matrices as it is a rapid and powerful technique, with no sample preparation. However it was not used to investigate extracted organic matter like humic substances. This work aims to fully investigate for the first time front face fluorescence spectroscopy response of a ternary system including boric acid, tryptophan and humic substances, and two binaries system containing quinine sulfate or humic substance in boric acid. Pure chemicals, boric acid, tryptophan, quinine sulfate and humic acid were mixed together in solid pellet at different contents from 0 to 100% in mass. The measurement of excitation emission matrix of fluorescence (3D fluorescence) and laser induced fluorescence were then done in the front face mode. Fluorescence matrices were decomposed using the CP/PARAFAC tools after scattering treatments. Results show that for 3D fluorescence there is no specific component for tryptophan and quinine sulfate, and that humic substances lead to a strong extinction effect for mixture containing quinine sulfate. Laser induced fluorescence gives a very good but non-specific related response for both quinine sulfate and tryptophan. No humic substances fluorescence response was found, but extinction effect is observed as for 3D fluorescence. This effect is stronger for quinine sulfate than for tryptophan. These responses were modeled using a simple absorbance versus emission model.

Application of solid surface fluorescence EEM spectroscopy for tracking organic matter quality of native halophyte and furrow-irrigated soils

Solid surface fluorescence excitation-emission matrix (EEM) is developed a potential method to characterize soil organic matter (SOM). Solid surface EEM spectroscopy with parallel factor analysis (PARAFAC) and hierarchical cluster analysis (HCA) is used to extract fluorescent components, to seek latent factors, and to investigate spatial distribution of SOM. Soil samples were collected from four native halophyte and two furrow-irrigated soil profiles, i.e. Comm. Salicornia europaea (CSE), Comm. Suaeda glauca (CSG), Comm. Kalidium cuspidatum (CKC), Comm. Sophora alopecuroides (CSA), corn fields (CFD), and wheat fields (WFD). SOM contained six fluorescent components: microbial/terrestrial fulvic-like fluorescent components (C1), tryptophan-like/lignin-derived phenol fluorescent components (C2), terrestrial humic-like fluorescent component (C3), lignin oxidative degradation by-products (C4 and C5), and amino acids (C6). The C 4 and C5 were the representative components of SOM within the CSE, CSG, CKC, CSA and CFD soil profiles, while the C2 and C6 were dominated within the WFD soil profile. The C4, C5, C1 and C2 were latent factors, and they could roughly distinguish SOM within the whole saline soil profiles except the CFD. A humification index (H/L) deduced from the fluorescent components, was very suitable to indicate humification levels of SOM. Humification levels of SOM within the halophyte soil profiles decreased with soil depth, but the opposite trends within the furrow-irrigated soil profiles. The H/L was closely correlated with exchangeable sodium percentage (ESP), and humification levels increased with the decreasing ESP. Soil surface EEM may not only indicate organic matter fractions of saline soils, but may be transferred to other types of landscape.

New room temperature coacervation scheme for lead traces determination by solid surface fluorescence. Application to wines produced in Argentina

Lead traces were preconcentrated on paper filter discs using the coacervation phenomenon based on cationic and anionic surfactant reaction at room temperature. The increase in fluorescent signal of Rhodamine B dye was used for metal quantification by solid surface fluorescence. Experimental variables that influence on preconcentration step and fluorimetric sensitivity were optimized using uni-varied assays. The calibration graph using zeroth order regression was linear from 1.24×10−3μgL−1 to 1.25μgL−1 with a correlation coefficient of 0.997. At the experimental optimal conditions, a limit of detection of 3.73×10−4μgL−1 and a limit of quantification of 1.24×10−3μgL−1 were obtained. The method showed good sensitivity, adequate selectivity with good tolerance to foreign ions, and was applied to the determination of trace amounts of Pb(II) in red and white wines produced in Argentina with satisfactory results validated by ICP-MS. The proposed method represents an innovative application of paper filters to solid surface fluorescence methodology.

New solid surface fluorescence methodology for lead traces determination using rhodamine B as fluorophore and coacervation scheme: Application to lead quantification in e-cigarette refill liquids

A new environmental friendly methodology based on fluorescent signal enhancement of rhodamine B dye is proposed for Pb(II) traces quantification using a preconcentration step based on the coacervation phenomenon. A cationic surfactant (cetyltrimethylammonium bromide, CTAB) and potassium iodine were chosen for this aim. The coacervate phase was collected on a filter paper disk and the solid surface fluorescence signal was determined in a spectrofluorometer. Experimental variables that influence on preconcentration step and fluorimetric sensitivity have been optimized using uni-variation assays. The calibration graph using zero th order regression was linear from 7.4×10−4 to 3.4μgL−1 with a correlation coefficient of 0.999. Under the optimal conditions, a limit of detection of 2.2×10−4μgL−1 and a limit of quantification of 7.4×10−4μgL−1 were obtained. The method showed good sensitivity, adequate selectivity with good tolerance to foreign ions, and was applied to the determination of trace amounts of Pb(II) in refill solutions for e-cigarettes with satisfactory results validated by ICP-MS. The proposed method represents an innovative application of coacervation processes and of paper filters to solid surface fluorescence methodology.

Novel method for determination of zinc traces in beverages and water samples by solid surface fluorescence using a conventional quartz cuvette

A new method for zinc pre-concentration/separation and determination by molecular fluorescence is proposed. The metal was complexed with o-phenanthroline and eosin at pH 7.5 in Tris; a piece of filter paper was used as a solid support and solid fluorescent emission measured using a conventional quartz cuvette. Under optimal conditions, the limits of detection and quantification were 0.36×10−3 and 1.29×10−3μgL−1, respectively, and the linear range from 1.29×10−3 to 4.50μgL−1. This method showed good sensitivity and selectivity, and it was applied to the determination of zinc in foods and tap water. The absence of filtration reduced the consumption of water and electricity. Additionally, the use of common filter papers makes it a simpler and more rapid alternative to conventional methods, with sensitivity and accuracy similar to atomic spectroscopies using a typical laboratory instrument.

Quantification of caffeine in dietary supplements and energy drinks by solid-surface fluorescence using a pre-concentration step on multi-walled carbon nanotubes and Rhodamine B

A new method for the determination of caffeine, a non-fluorescent analyte, based on the enhancement of the fluorescence of Rhodamine B dye on a membrane filter modified with multi-walled carbon nanotubes is proposed. The method comprises pre-concentration of caffeine on a solid support by chemofiltration in buffered solution onto multi-walled carbon nanotubes previously oxidised and dispersed in cationic surfactant admicelles. The effect of experimental parameters, including the nature of the buffer and pH, the nature of the solid support, filtration flow rate, dye and carbon nanotube concentration, and the nature of the surfactant and concentration were investigated by means univariation assays. Under optimum experimental conditions, the pre-concentration system gave detection and quantification limits of 0.3 and 1.1 µg l−1, respectively. A wide linear range was achieved varying from concentrations of 1.1 to 9.7 × 103 µg l−1 (r2 = 0.999). Satisfactory recovery values were obtained using the method of standard addition, confirming the feasibility of this method for caffeine determination in energising dietary supplements and energy drinks.