Ultrasensitive determination of silver ion based on synchronous fluorescence spectroscopy with nanoparticles

Based on the characteristics of synchronous fluorescence spectroscopy (SFS), a new method with high sensitivity and selectivity was developed for rapid determination of silver ion with functional cadmium sulphide (CdS) nanoparticles as a fluorescence probe. When Δλ (λ_em − λ_ex) = 215 nm, maximum synchronous fluorescence is produced at 304 nm. Under optimal conditions, functional cadmium sulphide displayed a calibration response for silver ion over a wide concentration range from 0.8 × 10⁻¹⁰ to 1.5 × 10⁻⁸ mol L⁻¹. The limit of detection was 0.4 × 10⁻¹⁰ mol L⁻¹ and the relative standard deviation of seven replicate measurements for the lowest concentration (0.8 × 10⁻¹⁰ mol L⁻¹) was 2.8%. Compared with several fluorescence methods, the proposed method had a wider linear range and improved the sensitivity. Furthermore, the concentration dependence of the synchronous fluorescence intensity is effectively described by a Langmuir-type binding isotherm.     

Synchronous fluorescence measurement of enrofloxacin in the pharmaceutical formulation and its residue in milks based on the yttrium (III)-perturbed luminescence

A simple, rapid and sensitive synchronous fluorescence method is put forward for the determination of enrofloxacin (ENRO) in the pharmaceutical formulation and its residue in milk based on the yttrium (III)-perturbed luminescence. When Y³⁺ is added into the ENRO solution, the fluorescence of ENRO is significantly enhanced. The synchronous fluorescence technology is employed in the method to determine trace amount of ENRO residue in milks. The synchronous fluorescence intensity of the system is measured in a 1-cm quartz cell with excitation wavelength of 328 nm, Δλ = 80 nm. A good linear relationship between the fluorescence intensity and the ENRO concentration is obtained in the range of 1.0 × 10⁻⁹ to 2.0 × 10⁻⁶ mol L⁻¹ (r² = 0.9992). The limit of detection (LOD) of this method attains as low as 3.0 × 10⁻¹⁰ mol L⁻¹ (S/N = 3). The selectivity of this method is also very good. Common metal ions, rare-earth ions and some pharmaceuticals, which are usually used together with ENRO, do not interfere with the determination of ENRO under the actual conditions. The proposed method can be applied to determine ENRO residue in milks, and limit of quantification (LOQ) determined in the spiked milk is estimated to be 2.8 × 10⁻⁸ mol L⁻¹ (10 μg L⁻¹). Moreover, this method can be used as a rapid screening for judging whether the ENRO residues in milks exceed Minimal Risk Levels (MRLs) or not. In addition, the mechanism of the fluorescence enhancement is also discussed in detail.     

A new resonance scattering spectral method for the determination of trace amounts of iodate with rhodamine 6G

Under the conditions of 0.04 mol L⁻¹ HCl-8.0 × 10⁻⁴ mol L⁻¹ KI, there is a fluorescence peak at 540 nm and a synchronous fluorescence peak at 540 nm for rhodamine 6G (RhG). When there is IO₃⁻, it reacts with exceed I⁻ to form I₃⁻. And I₃⁻ and RhG combine into ion association particles. The particles exhibit three resonance scattering peaks at 320, 400 and 595 nm. And there is fluorescence quenching at 540 nm. Iodine concentration is proportional to the intensity of the resonance scattering intensity at 400 nm in the range of 1.0-20 × 10⁻⁷ mol L⁻¹. And a new resonance scattering spectral (RSS) method has been described for the determination of IO₃⁻ in salt samples. The spectral results have been verified that the formation of (RhG-I₃)_n association particles and solid-liquid interfaces are the main factor that cause the fluorescence quenching and resonance scattering effects.     

A potential visual fluorescence probe for ultratrace arsenic (III) detection by using glutathione-capped CdTe quantum dots

The interaction between mercaptoacetic acid (MA)-capped CdTe QDs, MA-capped CdTe/ZnS QDs or glutathione (GSH)-capped CdTe QDs with As(III) was studied using fluorescence spectrometry. As (III) has a high-affinity to reduced-GSH to form As(SG)₃, and the emission of the GSH-capped CdTe QDs (λ_em. = 612 nm) is quenched effectively. Thus, a novel fluorescence spectrometric method was developed for As (III) determination by using GSH-CdTe QDs. Under optimal conditions, the quenched fluorescence intensity (F₀/F) increased linearly with the concentration of As (III) ranging from 5.0 × 10⁻⁶ to 25 × 10⁻⁵ mol L⁻¹. The limit of detection (3σ) for As (III) was found to be 2 × 10⁻⁸ mol L⁻¹. This method is potentially useful in visual detection of As (III) under irradiation of the ultraviolet light.     

An rhodamine-based fluorescence probe for iron(III) ion determination in aqueous solution

An “off-on” rhodamine-based fluorescence probe for the selective signaling of Fe(III) has been designed exploiting the guest-induced structure transform mechanism. This system shows a sharp Fe(III)-selective fluorescence enhancement response in 100% aqueous system under physiological pH value and possesses high selectivity against the background of environmentally and biologically relevant metal ions including Al(III), Cd(II), Fe(II), Co(II), Cu(II), Ni(II), Zn(II), Mg(II), Ba(II), Pb(II), Na(I), and K(I). Under optimum conditions, the fluorescence intensity enhancement of this system is linearly proportional to Fe(III) concentration from 6.0 × 10⁻⁸ to 7.2 × 10⁻⁶ mol L⁻¹ with a detection limit of 1.4 × 10⁻⁸ mol L⁻¹.     

Rapid simultaneous analysis of 1-hydroxypyrene, 2-hydroxyfluorene, 9-hydroxyphenanthrene, 1- and 2-naphthol in urine by first derivative synchronous fluorescence spectrometry using Tween-20 as a sensitizer

A novel method of first derivative synchronous fluorescence was developed for the rapid simultaneous analysis of trace 1-hydroxypyrene (1-OHP), 1-naphthol (1-NAP), 2-naphthol (2-NAP), 9-hydroxyphenanthrene (9-OHPe) and 2-hydroxyfluorene (2-OHFlu) in human urine. Only one single scan was needed for quantitative determination of five compounds simultaneously when Δλ = 10 nm was chosen. In the optimal experimental conditions, there was a linear relationship between the fluorescence intensity and the concentration of 1-OHP, 1-NAP, 2-NAP, 9-OHPe and 2-OHFlu in the range of 1.75 × 10⁻⁹ to 4.50 × 10⁻⁶ mol L⁻¹, 3.64 × 10⁻⁸ to 2.20 × 10⁻⁴ mol L⁻¹, 8.18 × 10⁻⁹ to 1.20 × 10⁻⁴ mol L⁻¹, 3.26 × 10⁻⁹ to 8.50 × 10⁻⁵ mol L⁻¹ and 4.88 × 10⁻⁹ to 5.50 × 10⁻⁶ mol L⁻¹, respectively. The limits of detection (LOD) were found to be 5.25 × 10⁻¹⁰ mol L⁻¹ for 1-OHP, 1.10 × 10⁻⁸ mol L⁻¹ for 1-NAP, 2.46 × 10⁻⁹ mol L⁻¹ for 2-NAP, 9.77 × 10⁻¹⁰ mol L⁻¹ for 9-OHPe and 1.46 × 10⁻⁹ mol L⁻¹ for 2-OHFlu. The proposed method is reliable, selective and sensitive, and has been used successfully in the determination of traces of 1-OHP, 1-NAP, 2-NAP, 9-OHPe and 2-OHFlu in human urine samples, whose results were in good agreement with those gained by the HPLC method.     

Functionalized cadmium sulfide quantum dots as fluorescence probe for silver ion determination

CdS quantum dots (QDs) modified with l-cysteine has been prepared by one step. They are water-soluble and biocompatible. To improve CdS QDs stability and interaction between silver ion and functionalized CdS QDs in aqueous solution, some amounts of fresh l-cysteine were added to functionalized CdS solution. Based on the characteristic fluorescence enhancement of CdS QDs at 545 nm by silver ions in the presence of some amounts of fresh l-cysteine, simultaneously, a gradual red shift of fluorescence emission bands of CdS QDs from 545 to 558 nm was observed. A simple, rapid, sensitive and specific detection method for silver ion was proposed. Under optimum conditions, the fluorescence intensity of CdS QDs is linearly proportional to silver concentration from 2.0 × 10⁻⁸ to 1.0 × 10⁻⁶ mol/L with a detection limit of 5.0 × 10⁻⁹ mol/L. In comparison with single organic fluorophores, functionalized CdS quantum dots are brighter, more stable against photobleaching, and don’t suffer from blinking. Furthermore, owing to the fluorescence enhancement effect of CdS QDs by silver ion, the proposed method showed lower detection blank and higher sensitivity. Possible fluorescence enhancement mechanism was also studied.     

Study on the new fluorescence enhancement system of Tb-1,10-bis(2′-carboxylphenyl)-1,4,7,10-tetraoxadecane in silver chloride collosol and its analytical application

A new salicylic-based open-chain crown ether ligand, 1,10-bis(2′-carboxylphenyl)-1,4,7,10-tetraoxadecane (BCPTD) was synthesized. Solutions of its complex with Tb³⁺ can emit the intrinsic fluorescence of Tb³⁺. The fluorescence intensity of the complex in KCl solution was enhanced by the addition of silver(I), leading to a new fluorescence enhancement phenomenon. The spectrofluorimetric determination of traces of silver(I) based on the above phenomenon was carried out. The excitation and emission wavelengths are 298 and 545 nm, respectively. Under optimal conditions, the differential value of fluorescence intensity in the absence and presence of Ag⁺ was proportional to the concentration of silver(I) in the range 0.5-20 μg ml⁻¹. The method was applied to the determination of silver(I) in a standard ore sample. The analytical performance is investigated in detail by using common aromatic carboxylic acids or synthetic analogues of BCPTD as ligands to replace BCPTD. It was found that Tb-aromatic acid complexes did not result in fluorescence enhancement of Tb³⁺ in AgCl collosol. The phenomenon was only observed in Tb(III) with BCPTD or its open-chain crown ether analogues solutions.In addition, the enhancement of the fluorescence intensity of terbium(III) in these complexes depends on the extent of formation of the AgCl collosol.     

Synchronous fluorescence determination of DNA based on the interaction between methylene blue and DNA

The fluorescence intensity of methylene blue (MB) quenched by DNA in the pH range of 6.5-8.0 was studied with synchronous fluorescence technology. A novel method for detecting single-stranded and double-stranded DNA was developed. The decreased fluorescence intensity at 664 nm is in proportion to the concentration of DNA in the range of 0.28-11.0 μmol L⁻¹ for ctDNA, 0.14-8.25 μmol L⁻¹ for thermally denatured ctDNA and 0.28-8.25 μmol L⁻¹ for hsDNA. The detection limits (S/N = 3) are 0.11, 0.04 and 0.04 μmol L⁻¹, respectively. The method is rapid, selective, and the reagents are lower toxic. It has been used for the determination of DNA in synthetic samples with good satisfaction. In addition, the interaction modes between MB and ctDNA and the mechanism of the fluorescence quenching were also discussed in detail. The experimental results from absorption spectra and fluorescence polarization indicate that the possible interaction modes between MB and DNA are the electrostatic binding and the intercalation binding.     

Flow-injection determination of hydrogen peroxide based on fluorescence quenching of chromotropic acid catalyzed with Fe(II)

Flow-injection analysis system (FIA system), which was based on Fe(II)-catalyzed oxidation of chromotropic acid with hydrogen peroxide, was developed for the determination of hydrogen peroxide. The chromotropic acid has a fluorescence measured at λ_em = 440 nm (emission wavelength) with λ_ex = 235 nm (excitation wavelength), and the fluorescence intensity at λ_em = 440 nm quietly decreased in the presence of hydrogen peroxide and Fe(II), which was caused by Fe(II)-catalyzed oxidation of chromotropic acid with hydrogen peroxide. By measuring the difference of fluorescence intensity, hydrogen peroxide (1.0 × 10⁻⁸-1.0 × 10⁻³ mol L⁻¹) could be determined by the proposed FIA system, whose analytical throughput was 40 samples h⁻¹. The relative standard deviation (RSD) was 1.03% (n = 10) for 4.0 × 10⁻⁸ mol L⁻¹ hydrogen peroxide. The proposed FIA technique could be applied to the determination of hydrogen peroxide in rain water samples.     

Synchronous fluorescence determination of urinary 1-hydroxypyrene, β-naphthol and 9-hydroxyphenanthrene based on the sensitizing effect of β-cyclodextrin

A novel method for the simultaneous determination of 1-hydroxypyrene (1-OHP), β-naphthol (β-NAP) and 9-hydroxyphenanthrene (9-OHPe) in human urine has been established by using synchronous fluorescence spectrometry. It was based on the fact that synchronous fluorescence spectrometry can resolve the broad-band overlapping of conventional fluorescence spectra, which arise from their similar molecular structures. Only one single scan is needed for quantitative determination of three compounds simultaneously when Δλ = 15 nm is chosen. The signals detected at these three wavelengths, 369.6, 330.0 and 358.0 nm, vary linearly when the concentration of 1-OHP, β-NAP and 9-OHPe is in the range of 2.16 × 10⁻⁸-1.50 × 10⁻⁵ mol L⁻¹, 1.20 × 10⁻⁷-1.10 × 10⁻⁵ mol L⁻¹ and 1.07 × 10⁻⁷-3.50 × 10⁻⁵ mol L⁻¹, respectively. The correlation coefficients for the standard calibration graphs were 0.994, 0.999 and 0.997 (n = 7) for 1-OHP, β-NAP and 9-OHPe, respectively. The limits of detection (LOD) for 1-OHP, β-NAP and 9-OHPe were 6.47 × 10⁻⁹ mol L⁻¹, 3.60 × 10⁻⁸ mol L⁻¹ and 3.02 × 10⁻⁸ mol L⁻¹with relative standard deviations (R.S.D.) of 4.70-6.40%, 2.80-4.20%, 3.10-4.90% (n = 6), respectively. The method described here had been applied to determine traces of 1-OHP, β-NAP and 9-OHPe in human urine, and the obtained results were in good agreement with those obtained by the HPLC method. In addition, the interaction modes between β-cyclodextrin (β-CD) and 1-OHP, β-NAP or 9-OHPe, as well as the mechanism of the fluorescence enhancement were also discussed.     

Post-column terbium complexation and sensitized fluorescence detection for the determination of norepinephrine, epinephrine and dopamine using high-performance liquid chromatography

Terbium sensitized fluorescence was used as a post-column detection system to develop a simple, sensitive and rapid high-performance liquid chromatographic method for the simultaneous determination of catecholamines norepinephrine (NE), epinephrine (E) and dopamine (DA).Catecholamines were separated by an ion-pair reversed-phase chromatography on a BDS-Hypersil analytical column with a mobile phase of methanol and 50 mmol l⁻¹ acetate buffer (pH 4.7) containing 1.1 mmol l⁻¹ SOS and 0.11 mmol l⁻¹ EDTA (15+85 v/v).Catecholamines and the internal standard (3,4-dihydroxybenzylamine, DHBA) were post-column derivatized by the addition to the eluent of an alkaline solution containing a stoichiometric mixture of terbium(III) chloride and EDTA. Fluorescence detection (λ_ex=300 nm, λ_em=545 nm) is based on the sensitization of terbium ion fluorescence after complexation with catecholamines.The chemical compatibility between the eluent and the post-column reagent was studied and the analytical characteristics of the method were established. Detection limits found were 1.0×10⁻⁸, 4.0×10⁻⁸ and 7.0×10⁻⁸ mol l⁻¹ for NE, E and DA, respectively. The method has been successfully applied to the determination of catecholamines in urine samples after solid-phase extraction (SPE) pre-treatment. Recoveries from urine spiked with NE (4.0×10⁻⁷, 2.0×10⁻⁶ and 4.0×10⁻⁶ mol l⁻¹), E (8.2×10⁻⁸, 4.1×10⁻⁷ and 8.2×10⁻⁷ mol l⁻¹) and DA (1.0×10⁻⁶, 5.0×10⁻⁶ and 1.0×10⁻⁵ mol l⁻¹) varied from 98 to 100% (mean=99.3%), from 106 to 107% (mean=106.3%) and from 98 to 101% (mean=99.3%), respectively. The between-run precision (relative standard deviation, R.S.D.) for the method for three urine samples at different concentration levels of each catecholamine varied from 3.6 to 7.0%.     

A novel fluorescence sensor based on covalent immobilization of 3-amino-9-ethylcarbazole by using silver nanoparticles as bridges and carriers

A novel technique of covalent immobilization of indicator dyes in the preparation of fluorescence sensors is developed. Silver nanoparticles are used as bridges and carriers for anchoring indicator dyes. 3-amino-9-ethylcarbazole (AEC) was employed as an example of indicator dyes with terminal amino groups and covalently immobilized onto the outmost surface of a quartz glass slide. First, the glass slide was functionalized by (3-mercaptopropyl) trimethoxysilane (MPS) to form a thiol-terminated self-assembled monolayer, where silver nanoparticles were strongly bound to the surface through covalent bonding. Then, 16-mercaptohexadecanoic acid (MHDA) was self-assembled to bring carboxylic groups onto the surface of silver nanoparticles. A further activation by using 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) converted the carboxylic groups into succinimide esters. Finally, the active succinimide esters on the surface of silver nanoparticles were reacted with AEC. Thus, AEC was covalently bound to the glass slide and an AEC-immobilized sensor was obtained. The sensor exhibited very satisfactory reproducibility and reversibility, rapid response and no dye-leaching. Rutin can quench the fluorescence intensity of the sensor and be measured by using the sensor. The linear response of the sensor to rutin covers the range from 2.0 × 10⁻⁶ to 1.5 × 10⁻⁴ mol L⁻¹ with a detection limit of 8.0 × 10⁻⁷ mol L⁻¹. The proposed technique may be feasible to the covalent immobilization of other dyes with primary amino groups.     

Highly sensitive and selective detection of biothiols using graphene oxide-based “molecular beacon”-like fluorescent probe

A fluorometric method for quantity analysis of biothiols was developed using a graphene oxide (GO)-based “molecular beacon”-like probe, which consisted of FITC labeled thymine (T)-rich single-stranded DNA (ssDNA), GO and Hg²⁺ ions. The labeled ssDNA containing T–T mismatches would self-hybridize to duplex in the presence of Hg²⁺, which can avoid its adsorption on GO and the fluorescence of this GO-based probe was recovered. The fluorescence of the probe quenched after the addition of biothiols such as glutathione (GSH) and cysteine (Cys) owing to thiol groups can selectively competitive ligation of Hg²⁺ ions with T–T mismatches. In the present work, the GO-based probe was used for the determination of GSH and Cys. Under the optimal conditions, a linear correlation was established between fluorescence intensity ratio I₀/I and the concentration of GSH in the range of 2.0 × 10⁻⁹–5.0 × 10⁻⁷ mol L⁻¹ with a detection limit of 1.0 × 10⁻⁹ mol L⁻¹. The linear range for Cys is from 5.0 × 10⁻⁹ to 4.5 × 10⁻⁷ mol L⁻¹ with a detection limit of 2.0 × 10⁻⁹ mol L⁻¹. The proposed method was applied to the determination of GSH in human serum and cell extract samples with satisfactory results.     

A sensitive enzymatic method for paraoxon detection based on enzyme inhibition and fluorescence quenching

A sensitive and selective method for the paraoxon detection based on enzyme inhibition and fluorescence quenching was presented in this study. Under the catalytic effect of acetylcholinesterase (AChE), acetylthiocholine (ATCh) hydrolysis released thiocholine (TCh) which could react with N-(7-dimethylamino-4-methylcoumarin-3-yl) maleimide (DACM) to produce a blue fluorescence compound. Subsequently, AChE catalytic activity was inhibited with the addition of paraoxon, which caused TCh decreased, leading to a significant decrease of the blue fluorescent compound. Meanwhile, p-nitrophenol, the hydrolysis product of paraoxon, would lead to a quenching of the fluorescence. Therefore, fluorescence intensity of the system would decrease dramatically by a combined effect of enzyme inhibition and fluorescence quenching. Under optimal experimental conditions, an excellent linear relationship between the decrease of fluorescence intensity and paraoxon concentration over the range from 5.5 × 10⁻¹² to 1.8 × 10⁻¹⁰ mol L⁻¹ was obtained. Fluorescence background caused by nonenzymatic hydrolysis of ATCh or other matters was relatively low, the proposed approach offered adequate sensitivity for the detection of paraoxon at 3.5 × 10⁻¹² mol L⁻¹.     

Laser induced fluorescence and photochemical derivatization for trace determination of camptothecin

Laser-excited fluorescence was used for the selective determination of camptothecin in samples containing anti-cancer camptothecin-analogs (irinotecan and topotecan). The selectivity of the method was based on the UV photochemical derivatization in basic solution which increased the analyte fluorescence (337/450 nm) and eliminated fluorescence from the two campthotecin-analogs. The influence of UV exposure time and sodium hydroxide concentration was studied using an experimental design. Limit of detection was 4 × 10⁻¹⁰ mol L⁻¹ with linear fluorescence response up to 1 × 10⁻⁶ mol L⁻¹. Average recoveries of camptothecin (added to the samples to simulate a contamination) were 92 ± 4 and 94 ± 6% (n = 3) respectively in irinotecan and topotecan based pharmaceuticals.     

Investigation on enhanced chemiluminescence reaction systems with bis(hydrogenperiodato) argentate(III) complex anion for fluoroquinolones synthetic antibiotics

A novel chemiluminescence (CL) reaction system with bis(hydrogenperiodato) argentate(III) complex anion (Ag(III) complex, [Ag(HIO₆)₂]⁵⁻), for the first time, is developed for the determination of lomefloxacin (LMFX), enrofloxacin (ENLX) and pefloxacin (PFLX). The possible CL emission mechanism was discussed by comparing the fluorescence emission with CL spectra. The CL conditions of [Ag(HIO₆)₂]⁵⁻-H₂SO₄-LMFX/ENLX/PFLX systems were investigated and optimized. Under the optimized experimental conditions, the CL intensity is proportional to the concentration of the drugs in the range 0.2994-36.80 × 10⁻⁷ g mL⁻¹ for LMFX, 4.00-30.0 × 10⁻⁷ g mL⁻¹ for ENLX and 1.54-27.64 × 10⁻⁷ g mL⁻¹ for PFLX. The limit of detection (s/n = 3) was 9.1 × 10⁻⁹ g mL⁻¹ for LMFX, 3.1 × 10⁻⁹ g mL⁻¹ for ENLX and 4.4 × 10⁻⁹ g mL⁻¹ for PFLX. The recovery of LMFX, ENLX and PELX from the spiked pharmaceutical preparations was in the range of 92.3-105% with the RSDs of 0.5-2.7%. For urine, serum and milk samples the recoveries of the three drugs were in the range of 85.1-107% for LMFX with the RSDs of 2.3-3.4%. 80.2-112% for ENLX with the RSDs of 1.4-2.8%, and 87.8-114% for PFLX with the RSDs of 1.6-2.7%. The proposed method was applied successfully to the determination of these compounds in real samples.     

Preparation of silver hexacyanoferrate nanoparticles and its application for the simultaneous determination of ascorbic acid, dopamine and uric acid

A silver hexacyanoferrate nanoparticles/carbon nanotubes modified glassy carbon electrode was fabricated and then successfully used for the simultaneous determination of ascorbic acid, dopamine and uric acid by cyclic voltammetry. A detailed investigation by transmission electron microscopy (TEM) and electrochemistry was performed in order to elucidate the preparation process and properties of the nanocomposites. The size of silver hexacyanoferrate nanoparticles was examined by TEM around 27 nm. Linear calibration plots were obtained over the range of 4.0 × 10⁻⁶-7.8 × 10⁻⁵, 2.4 × 10⁻⁶-1.3 × 10⁻⁴ and 2.0 × 10⁻⁶-1.5 × 10⁻⁴ mol L⁻¹ with detection limits of 4.2 × 10⁻⁷,1.4 × 10⁻⁷ and 6.0 × 10⁻⁸ mol L⁻¹ for ascorbic acid, dopamine and uric acid, respectively. The practical analytical utilities of the modified electrode were demonstrated by the determination of ascorbic acid, dopamine and uric acid in urine and human blood serum samples.     

Selective determination of bisphenol A (BPA) in water by a reversible fluorescence sensor using pyrene/dimethyl β-cyclodextrin complex

A bifurcated optical fiber chemical sensor for continuous monitoring of bisphenol A (BPA) has been proposed based on the fluorescence quenching (λ_ex/λ_em = 286/390 nm) of pyrene/dimethyl β-cyclodextrin (HDM-β-CD) supramolecular complex immobilized in a plasticized poly(vinyl chloride) (PVC) membrane, in which pyrene served as a sensitive fluorescence indicator probe. The decrease of the fluorescence intensity of pyrene/HDM-β-CD complex upon the addition of BPA was attributed to the displacement of pyrene by BPA, which has been utilized as the basis of the fabrication of a BPA-sensitive fluorescence sensor. The response mechanism of the sensor was discussed in detail. The sensor exhibited a dynamic detection range from 7.90 × 10⁻⁸ to 1.66 × 10⁻⁵ mol L⁻¹ with a detection limit of 7.00 × 10⁻⁸ mol L⁻¹, and showed excellent reproducibility, reversibility, selectivity, and lifetime. The proposed sensor was successfully used for the determination of BPA in water samples and landfill leachate.     

Localized surface plasmon resonance sensor for simultaneous kinetic determination of peroxyacetic acid and hydrogen peroxide

A new sensor for simultaneous determination of peroxyacetic acid and hydrogen peroxide using silver nanoparticles (Ag-NPs) as a chromogenic reagent is introduced. The silver nanoparticles have the catalytic ability for the decomposition of peroxyacetic acid and hydrogen peroxide; then the decomposition of them induces the degradation of silver nanoparticles. Hence, a remarkable change in the localized surface plasmon resonance absorbance strength could be observed. Spectra-kinetic approach and artificial neural network was applied for the simultaneous determination of peroxyacetic acid and hydrogen peroxide. Linear calibration graphs were obtained in the concentration range of (8.20 × 10⁻⁵ to 2.00 × 10⁻³ mol L⁻¹) for peroxyacetic acid and (2.00 × 10⁻⁵ to 4.80 × 10⁻³ mol L⁻¹) for hydrogen peroxide. The analytical performance of this sensor has been evaluated for the detection of simultaneous determination of peroxyacetic acid and hydrogen peroxide in real samples.