Study on the resonance Rayleigh scattering and resonance non‐linear scattering spectra of ion‐association complexes of [PdI4]2−‐protein systems and their analytical applications

In an acid medium solution, proteins such as bovine serum albumin, human serum albumin, ovalbumin, hemoglobin, lysozyme, γ‐globulin, α‐chymotrypsin and papain could react with [PdI₄]^2? by virtue of electrostatic attraction and hydrophobic force to form ion‐association complexes. As a result, the resonance Rayleigh scattering (RRS) and resonance nonlinear scattering such as second‐order scattering (SOS) and frequency doubling scattering (FDS) intensities were enhanced greatly and new scattering spectra appeared. The maximum scattering peaks of RRS, SOS and FDS were at 367, 720 and 370 nm, respectively. The enhanced RRS, SOS and FDS intensities were directly proportional to the concentrations of proteins. The detection limits for the different proteins were 2.4–11.8 ng/mL for RRS method, 9.5–47.9 ng/mL for SOS method and 4.6–18.5 ng/mL for FDS method. In this work, the influences of the interaction of [PdI₄]^2? with proteins on spectral characteristics of RRS, SOS and FDS were investigated and the optimum conditions were tested. Meanwhile, the effects of coexisting substances were tested and the results showed that the method exhibited a good selectivity. Based on the above research, a highly sensitive, simple and rapid method for the determination of trace amounts of proteins by resonance light scattering technique has been developed. It can be applied to the determination of proteins in tablet, human serum and urine samples. Copyright © 2009 John Wiley & Sons, Ltd.     

Study on the ternary system of MoO42‐–enzyme–PdCl2 by resonance Rayleigh scattering,second‐order scattering and frequency‐doubling scattering spectra and its analytical application

In pH 4.0 Britton–Robinson buffer medium, PdCl₂ was able to react with enzymes (EZ) such as lysozyme (LYSO) and papain (PAP) to form a coordination complex (EZ–PdCl₂), which further reacted with MoO₄^2‐ to form a ternary complex (MoO₄^2‐–EZ–PdCl₂). As a result, the absorption and fluorescence spectra changed; new spectra of resonance Rayleigh scattering (RRS), second‐order scattering (SOS) and frequency‐doubling scattering (FDS) appeared and their intensities were enhanced greatly. The maximum RRS, SOS and FDS wavelengths of two ternary complexes were located at 310, 560 and 350 nm, respectively. The increments of scattering intensity were directly proportional to the concentrations of EZ within certain ranges. The detection limits (3σ) of LYSO and PAP were 4.5 and 14.0 ng/mL (RRS method), 9.6 and 57.8 ng/mL (SOS method), and 5.2 and 106.0 ng/mL (FDS method). Taking the MoO₄^2‐–LYSO–PdCl₂ system, which was more sensitive, as an example, the effects of coexisting substances were evaluated. The methods showed excellent selectivity. Accordingly, new rapid, convenient, sensitive and selective scattering methods for the determination of LYSO and PAP were proposed and applied to determine LYSO in egg white with satisfactory results. The reaction mechanism and basis of the enhancement of scattering were discussed. Copyright © 2012 John Wiley & Sons, Ltd.     

Interaction of proteins with aluminum(III)–chlorophosphonazo III by resonance Rayleigh scattering method

In weak acid medium, aluminum(III) can react with chlorophosphonazo III [CPA(III), H₈L] to form a 1:1 coordination anion [Al(OH)(H₄L)]^2‐. At the same time, proteins such as bovine serum albumin (BSA), lysozyme (Lyso) and human serum albumin (HSA) existed as large cations with positive charges, which further combined with [Al(OH)(H₄L)]^2‐ to form a 1:4 chelate. This resulted in significant enhancement of resonance Rayleigh scattering (RRS), second‐order scattering (SOS) and frequency doubling scattering (FDS). In this study, we investigated the interaction between [Al(OH)(H₄L)]^2‐ and proteins, optimization of the reaction conditions and the spectral characteristics of RRS, SOS and FDS. The maximum RRS wavelengths of different protein systems were located at 357–370 nm. The maximum SOS and FDS wavelengths were located at 546 and 389 nm, respectively. The scattering intensities (ΔI) of the three methods were proportional to the concentration of the proteins, within certain ranges, and the detection limits of the most sensitive RRS method were 2.6–9.3 ng/mL. Moreover, the chelate reaction mechanism or the reasons for the enhancement of RRS were discussed through absorption spectra, fluorescence spectra and circular dichroism (CD) spectra. Copyright © 2013 John Wiley & Sons, Ltd.     

Study on the interaction between ligustrazine and 12‐tungstophosphoric acid using resonance Rayleigh scattering and resonance nonlinear scattering spectra,and its analytical applications

In an HCl medium (pH 1.5), ligustrazine (2,3,5,6‐tetramethylpyrazine, TMP) reacted with 12‐tungstophosphoric acid (TP) to form a 3 : 1 ion‐association complex. As a result, the intensities of resonance Rayleigh scattering (RRS), second‐order scattering (SOS) and frequency doubling scattering (FDS) were greatly enhanced and new scattering spectra appeared. The maximum RRS, SOS and FDS wavelengths of the ion‐association complexes were located at 379, 738 and 395 nm, respectively. The scattering intensity increments (ΔI_RRS, ΔI_SOS and ΔI_FDS) were directly proportional to the concentration of ligustrazine within certain ranges. The detection limits (3σ) of RRS, SOS and FDS were 1.6, 3.2 and 2.8 ng/mL. Optimal conditions for the RRS method and factors influencing the method were discussed, and the structure of the ion‐association complex and the reaction mechanism were investigated. Transmission electron microscopy (TEM) was used to characterize the structures of the ion‐association complex. Based on the ion‐association reaction and its spectral response, a rapid, simple and sensitive RRS method for the determination of TMP was developed. It was applied to the determination of TMP in tablet and urine samples with satisfactory results. Copyright © 2014 John Wiley & Sons, Ltd.     

Determination of doxepin hydrochloride in spiked human plasma and capsule after derivatization with eosin Y using resonance Rayleigh scattering,second-order scattering and frequency doubling scattering methods

Doxepin hydrochloride (DOX) is a tricyclic antidepressant drug. Three sensitive spectrofluorimetric methods, namely resonance Rayleigh scattering (RRS), frequency doubling scattering (FDS) and second-order scattering (SOS), were developed and validated for their estimation of doxepin in spiked human plasma and formulation using liquid–liquid extraction method through the formation of an ion pair complex with eosin Y at a pH of 4.5. Various factors affecting fluorescence intensity were optimized, and the reaction kinetics was determined using the Arrhenius equation method. Different scattering methods such as RRS, FDS and SOS were developed at maximum scattering wavelengths λ_ex/λ_em = 567/567 nm for RRS, 720/360 nm for SOS and 260/520 nm for FDS, respectively. The methods exhibited high sensitivities, and the detection limits for DOX were found to be 0.82, 1.20 and 1.03 ng/ml for RRS, FDS and SOS methods, respectively. The FDS method exhibited the highest sensitivity. The methods were validated using the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use guidelines and applied to determine DOX in capsule and spiked human plasma samples.     

A nanogold resonance Rayleigh scattering method for determination of trace As based on the hydride nanoreaction

In H₂SO₄ solution, As(III) was reduced to arsine (AsH₃) by NaBH₄, and was absorbed in HAuCl₄ solution to form nanogold particles (NGs) that exhibited a resonance Rayleigh scattering (RRS) effect at 370 nm. Under the selected conditions, when the As(III) concentration increased the RRS peak also increased due to the formation of more NGs. There was a linear correlation between RRS intensity and As(III) concentration in the range 6–1000 ng/mL, with a detection limit of 3 ng/mL. This new hydride generation–nanogold reaction RRS (HG–NG RRS) method was applied to determine trace amounts of As in milk samples, with satisfactory results. Copyright © 2015 John Wiley & Sons, Ltd.     

Effects of the interaction between Na2Wo4‐6‐benzylaminopurine anionic chelate and rhodamine 6G on the resonance Rayleigh scattering and fluorescence spectra and their analytical applications

In pH 4.99‐6.06 Britton‐Robinson (BR) buffer medium, 6‐benzylaminopurine (6‐BA) reacted with Na₂WO₄ to form 1:1 anionic chelate (6‐BA·WO₄)^2‐, which further reacted with rhodamine 6G to form ternary ion complexes at room temperature. This resulted in a significant enhancement of resonance Rayleigh scattering (RRS) with a maximum RRS wavelength of 316 nm. Meanwhile, the fluorescence of the solution was quenched and excitation (λ_ex) and emission (λ_em) wavelengths of the fluorescence were 290 and 559 nm, respectively. Intensities of RRS enhancing (ΔI_RRS) and fluorescence quenching (ΔI_F) were directly proportional to concentrations of 6‐BA. As a result, RRS and fluorescence quenching for determination of trace amounts of 6‐BA were developed. Under optimal conditions, linear ranges and detection limits of the two methods were 0.05‐15.00 µg/mL and 8.2 ng/mL (RRS), 0.50‐15.00 µg/mL and 17.0 ng/mL, respectively. It was found that the RRS method was superior to fluorescence quenching. The influence of these methods were investigated and results showed that RRS had good selectivity. RRS was applied to determine 6‐BA in vegetable samples with satisfactory results. Furthermore, the reaction mechanisms of the ternary ion‐association system are discussed. In addition, the polarization experiment revealed that the resonance light scattering (RLS) peak of Na₂WO₄‐6‐BA‐R6G consisted mainly of depolarized resonance fluorescence and resonance scattering. It was speculated that light emission fluorescence energy (E_L) transformed into resonance light scattering energy (E_RLS), which was a key reason for enhancement of RRS. Copyright © 2012 John Wiley & Sons, Ltd.     

Resonance Rayleigh‐scattering spectral method for the determination of some aminoglycoside antibiotics using CdTe quantum dots as a probe

A novel method is used for the determination of some aminoglycoside antibiotics (AGs) such as etimicin (ETM), isepamicin (ISP) and amikacin (AMK). It is based on the resonance Rayleigh scattering (RRS) intensities enhanced by AGs‐induced CdTe quantum dots aggregation. Under the optimum conditions, the increments in RRS intensity were directly proportional to the concentration of AGs in certain ranges. At the same time, the second‐order scattering, the frequency‐doubling scattering and the frequency‐trebling scattering intensities were also enhanced and their increments were proportional to the concentration of AGs. Among them, the RRS method had the highest sensitivity; the linear ranges and detection limits for ETM, ISP and AMK were 0.085–7.2, 0.0067–1.2, 0.017–6.0 and 0.025, 0.0051, 0.0020 μg mL^?1. This method was applied to the measurement of AGs in human serum and urine with satisfactory results. In addition, the reaction mechanism and the reasons for the enhancement of RRS are discussed using fluorescence, RRS, transmission electron microscope technology and quantum chemistry method. Copyright © 2009 John Wiley & Sons, Ltd.     

A rapid and sensitive resonance Rayleigh scattering spectra method for the determination of quinolones in human urine and pharmaceutical preparation

A new method based on resonance Rayleigh scattering (RRS) was proposed for the determination of quinolones (QNS) at the nanogram level. In pH 3.3–4.4 Britton–Robinson buffer medium, quinolones such as ciprofloxacin, pipemidic acid (PIP), lomefloxacin (LOM), norfloxacin (NOR) and sarafloxacin (SAR) were protonated and reacted with methyl orange (MO) to form an ion‐pair complex, which then further formed a six‐membered ring chelate with Pd(II). As a result, new RRS spectra appeared and the RRS intensities were enhanced greatly. RRS spectral characteristics of the MO–QNS–Pd(II) systems, the optimum conditions for the reaction, and the influencing factors were investigated. Under optimum conditions, the scattering intensity (∆I) increments were directly proportional to the concentration of QNS with in certain ranges. The method had high sensitivity, and the detection limits (3σ) ranged from 6.8 to 12.6 ng/mL. The proposed method had been successfully applied for the determination of QNS in pharmaceutical formulations and human urine samples. In addition, the mechanism of the reaction system was discussed based on IR, absorption and fluorescence spectral studies. The reasons for the enhancement of scattering spectra were discussed in terms of fluorescence‐scattering resonance energy transfer, hydrophobicity and molecular size. Copyright © 2014 John Wiley & Sons, Ltd.     

Study on the interaction between erythrosine B and the cardiac drug amiodarone using fluorescence,scattering, and absorbance spectra and their analytical application

In an acidic buffered solution, erythrosine B can react with amiodarone to form an association complex, which not only generates great enhancement in resonance Rayleigh scattering (RRS) spectrum of erythrosine B at 346.5 nm but also results in quenching of fluorescence spectra of erythrosine B at λ_emission = 550.4 nm/λ_excitation = 528.5 nm. In addition, the formed erythrosine B–amiodarone complex produces a new absorbance peak at 555 nm. The spectral characteristics of the RRS, absorbance, and fluorescence spectra, as well as the optimum analytical conditions, were studied and investigated. As a result, new spectroscopic methods were developed to determine amiodarone by utilizing erythrosine B as a probe. Moreover, the ICH guidelines were used to validate the developed RRS, photometric, and fluorimetric methods. The enhancements in the absorbance and the RRS intensity and the decrease in the fluorescence intensity of the used probe were proportional to the concentration of amiodarone in ranges of 2.5–20.0, 0.2–2.5, and 0.25–1.75 μg/mL, respectively. Furthermore, limit of detection values were 0.52 ng/mL for the spectrophotometric method, 0.051 μg/mL for the RRS method, and 0.075 μg/mL for the fluorimetric method. Moreover, with good recoveries, the developed spectroscopic procedures were applied to analyze amiodarone in its commercial tablets.     

High‐performance liquid chromatography study of gatifloxacin and sparfloxacin using erythrosine as post‐column resonance Rayleigh scattering reagent and mechanism study

Herein, a highly selective high‐performance liquid chromatography (HPLC) coupled with resonance Rayleigh scattering (RRS) method was developed to detect gatifloxacin (GFLX) and sparfloxacin (SPLX). GFLX and SPLX were first separated by HPLC, then, in pH 4.4 Britton–Robinson (BR) buffer medium, protonic quaternary ammonia cation of GFLX and SPLX reacted with erythrosine (ERY) to form 1:1 ion‐association complexes, which resulted in a significant enhancement of RRS signal. The experimental conditions of HPLC and post‐column RRS have been investigated, including detection wavelength, flow rate, pH, reacting tube length and reaction temperature. Reaction mechanism were studied in detail by calculating the distribution fraction. The maximum RRS signals for GFLX and SPLX were recorded at λ_ex = λ_em = 330 nm. The detection limits were 3.8 ng ml^?1 for GFLX and 17.5 ng ml^?1 for SPLX at a signal‐to‐noise ratio of 3. The developed method was successfully applied to the determination of GFLX and SPLX in water samples. Recoveries from spiked water samples were 97.56–98.85%.     

Resonance Rayleigh scattering method for the determination of chitosan with some anionic surfactants

In weak acidic buffer medium, chitosan binding with an anionic surfactant, such as sodium dodecyl benzene sulphonate (SDBS), sodium lauryl sulphate (SLS) or sodium dodecyl sulphonate (SDS), can result in a significant enhancement of resonance Rayleigh scattering (RRS) intensity. The results showed that under optimum conditions the enhanced RRS intensity is proportional to the concentration of chitosan in the range 0.10–20.0 µg/mL for SDBS, 0.27–15.0 µg/mL for SLS and 0.20–15.0 µg/mL for SDS. Among these, the sensitivity of SDBS is the highest and its detection limit for chitosan is 29 ng/mL, while those of SLS and SDS are 83 and 61 ng/mL, respectively. The method has good selectivity and was applied to the determination of trace amounts of chitosan in practical samples with satisfactory results. Therefore, a simple and convenient method with high sensitivity and selectivity for the determination of chitosan was established. Copyright © 2008 John Wiley & Sons, Ltd.     

Resonance Rayleigh scattering technique as a detection method for the RP‐HPLC determination of local anaesthetics in human urine

A highly selective and sensitive method of reversed phase high‐performance liquid chromatography (RP‐HPLC) coupled with resonance Rayleigh scattering (RRS) was developed for the determination of procaine, bupivacaine and tetracaine. Separation of three local anaesthetics was achieved at 35 °C on a C₁₈ column. The mobile phase was 30: 70 (v/v) acetonitrile/triethylamine–phosphoric acid buffer (pH 2.9) at flow rate of 0.3 mL/min. The RRS detection was conducted by taking advantage of the strong RRS enhancement of the local anaesthetics with erythrosine reaction in an acidic medium. Under optimum conditions, the limit of detection (S/N = 3) values were in the range of 2.4–11.2 ng/mL. Recoveries from spiked human urine samples were 95.8%–104.5%. The proposed method applied to the determination of local anaesthetics in human urine achieved satisfactory results. In addition, the mechanism of the reaction is fully discussed. Copyright © 2016 John Wiley & Sons, Ltd.     

Resonance Rayleigh scattering methods for the determination of chitosan with Congo red as probe

Two methods were presented for the sensitive and selective determination of chitosan (CTS) with Congo red (CR) as probe based on resonance Rayleigh scattering (RRS) intensities in health products. In weakly acidic buffer solution, the binding of CTS to CR, could result in the enhancement of the RRS intensities. Moreover, after adding OP emulsifier (octyl‐phenyl polyoxyethylene ether) to the system, the RRS intensities showed more significantly enhancement. The maximum RRS signals for the CTS–CR system and the CTS–CR–OP system were located at 380 nm and 376 nm, respectively. Under optimum experimental conditions, the increased RRS intensities (ΔI) of these two systems were linear to CTS concentration in the range of 0.40–8.00 μg/ml and 0.05–1.00 μg/ml. Their limits of detection (LOD) were 44.81 ng/ml and 6.99 ng/ml, which indicated that the latter system was more sensitive than the former. In this work, the optimum conditions and the effects of some foreign substances on the determination were studied. In addition, the effect of the molecular weight of CTS and the reasons for the enhancement of resonance light scattering were discussed. Finally, these two methods were applied to the determination of chitosan in health products with satisfactory results.     

Study on interactions of aminoglycoside antibiotics with calf thymus DNA and determination of calf thymus DNA via the resonance Rayleigh scattering technique

A simple and sensitive resonance Rayleigh scattering (RRS) spectra method was developed for the determination of calf thymus DNA (ctDNA). The enhanced RRS signals were based on the interactions between ctDNA and aminoglycoside antibiotics (AGs) including kanamycin (KANA), tobramycin (TOB), gentamicin (GEN) and neomycin (NEO) in a weakly acidic medium (pH 3.3–5.7). Parameters influencing the method were investigated. Under optimum conditions, increments in the scattering intensity (?I) were directly proportional to the concentration of ctDNA over certain ranges. The detection limit ranged from 12.2 to 16.9 ng/mL. Spectroscopic methods, including RRS spectra, absorption spectra and circular dichroism (CD) spectroscopy, coupled with thermo‐denaturation experiments were used to study the interactions, indicating that the interaction between AGs with ctDNA was electrostatic binding mode. Copyright © 2015 John Wiley & Sons, Ltd.     

Determination of bismuth in pharmaceutical products using phosphoric acid as molecular probe by resonance light scattering

A novel method for the sensitive determination of bismuth(III) in pharmaceutical products using phosphoric acid as a molecular probe by resonance light scattering (RLS) is discussed. In 0.5 mol/L phosphoric acid (H₃PO₄) medium, bismuth(III) reacted with PO₄^3? to form an ion association compound, which resulted in the significant enhancement of RLS intensity and the appearance of the corresponding RLS spectral characteristics. The maximum scattering peak of the system existed at 364 nm. Under optimal conditions, there was linear relationship between the relative intensity of RLS and concentration of bismuth(III) in the range of 0.06–10.0 µg/mL for the system. A low detection limit for bismuth(III) of 3.22 ng/mL was achieved. The relative standard deviations (RSD) for the determination of 0.40 and 0.80 µg/mL bismuth(III) were 2.1% and 1.1%, respectively, for five determinations. Based on this fact, a simple, rapid, and sensitive method was developed for the determination of bismuth(III) at nanogram level by RLS technique with a common spectrofluorimeter. This analytical system was successfully applied to determine the trace amounts of bismuth(III) in pharmaceutical products, which was in good agreement with the results obtained by atomic absorption spectrometry (AAS). Copyright © 2011 John Wiley & Sons, Ltd.     

Study on the interaction between palladium(II)–lincomycin chelate and erythosine by absorption,fluorescence and resonance Rayleigh scattering spectra and its analytical applications

In pH 5.0–5.4 HAc–NaAc buffer solution, lincomycin (Linco) reacted with Pd(II) to form 1:1 cationic chelate, which could further react with erythrosine (Ery) to form 1:1 ion‐association complexes (Pd–Linco)Ery. As a result, not only were the absorption and fluorescence spectra changed, but also the resonance Rayleigh scattering (RRS) intensity was greatly enhanced. These phenomena offered useful means for the determination of Linco by spectrophotometry, fluorescence and RRS methods. The linear range and detection limit of Linco were 0.20–3.00 µg/mL and 0.057 µg/mL, 0.20–4.80 µg/mL and 0.061 µg/mL, 0.05–2.70 µg/mL and 0.015 µg/mL for the spectrophotometric, fluorescence quenching and RRS methods, respectively. Among these, the RRS method obtained the highest sensitivity. Therefore, the optimum reaction conditions and the influences of coexisting substances were investigated using the RRS method. A simple, sensitive and rapid method has been developed for the determination of Linco in either the pharmaceutical form or human body fluids, and the reasons for RRS enhancement are discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

A new and simple resonance Rayleigh scattering method for human serum albumin using graphite oxide as probe

Graphite oxide (GO) was prepared by the Hummer procedure, and can be dispersed to stable colloid solution by ultrasonic wave. The GO exhibited an absorption peak at 313 nm, and a resonance Rayleigh scattering (RRS) peak at 490 nm. In pH 4.6 HAc‐NaAc buffer solution, human serum albumin (HSA) combined with GO probe to form large HSA‐GO particles that caused the RRS peak increasing at 490 nm. The increased RRS intensity was linear to HSA concentration in the range 0.50–200 µg/mL. Thus, a new and simple RRS method was proposed for the determination of HSA in samples, with a recovery of 98.1–104%. Copyright © 2012 John Wiley & Sons, Ltd.     

A highly sensitive resonance Rayleigh scattering and colorimetric assay for the recognition of propranolol in β‐adrenergic blocker

In this work, a highly sensitive, citrate anion‐capped gold nanoparticles (AuNPs)‐based assay for the determination of propranolol in real samples with resonance Rayleigh scattering (RRS) and colorimetry was developed. When AuNPs were prepared by the sodium citrate reduction method, citrate anions self‐assembled on the surface of AuNPs to form supramolecular complex anions. In BR 4.6 buffer solution, propranolol was positively charged and could bind with AuNPs to form larger aggregates through electrostatic force and hydrophobic effects. This results in remarkable enhancement of the RRS intensity and a color change in the AuNPs solution from red to blue via purple. Thus, a highly sensitive RRS and colorimetric assay the for detection of propranolol was developed with a linear range of 0.2–5.2 and 8–112 ng/ml, respectively. In addition, no difference was seen when comparing R‐propranolol with S‐propranolol, therefore, this method could not be used in the recognition of chiral propranolol. However, upon addition of other β‐adrenergic blockers, no phenomenon like that seen with propranolol was observed, meaning that this method can be used for determining the presence of propranolol in a mixture β‐adrenergic blockers. Finally, the optimum conditions, factors influencing the reaction, its mechanism and the reasons for enhancement of the RRS were discussed.     

A simple and rapid resonance Rayleigh scattering method for detection of indigo carmine in soft drink

A novel method that uses acridine orange (AO) to detect indigo carmine (IC) in soft drinks was developed. The method is highly sensitive and is based on a resonance Rayleigh scattering (RRS) technique. In Britton–Robinson (BR) buffer solution, pH 4.3, the weak RRS intensity of AO was greatly enhanced by the addition of IC, with the maximum peak located at 332 nm. Under optimum conditions, it was found that the enhanced RRS intensity was proportional to the concentration of IC over a range of 2–32 × 10^?6 mol/L. A low detection limit of 2.4 × 10^?8 mol/L was achieved. The sensitivity and selectivity of the method are high enough to permit the determination of trace amounts of IC without any significant interference from high levels of other components such as common anions and other amino acids. Finally, the concentration of IC in three different soft drinks was determined with satisfactory results. Copyright © 2016 John Wiley & Sons, Ltd.