At pH 1.3–1.6, tungstate WO₄^2–, can be converted to hexatungstate W₆O₁₉^2–, which can react with positively charged polymyxin B sulfate (PMB) to result in enhancement of resonance Rayleigh scattering (RRS) and resonance non-linear scattering, including second order scattering and frequency doubling scattering. Linear relationships can be established between enhanced scattering intensity and PMB concentration. The detection limits (3σ) were 5.5 ng/mL (RRS), 10.1 ng/mL (second order scattering) and 34.6 ng/mL (frequency doubling scattering). The optimum reaction conditions, influencing factors and related analytical properties were tested. The interaction mechanism was investigated via absorption spectrum, circular dichroism spectra and atomic force microscopy imaging. The basis of scattering enhancement is discussed. PMB in eardrops, human serum and urine, were quantified satisfactorily by RRS. Copyright © 2013 John Wiley & Sons, Ltd.

In weak acidic medium, interaction between papain and calf thymus DNA (ctDNA) resulted in absorption spectral change, fluorescence quenching of papain and remarkable enhancement of resonance Rayleigh scattering (RRS). The interaction types and binding modes were discussed by characteristics of RRS, absorption, fluorescence and circular dichroism spectra combining thermodynamic data. Four interaction types include electrostatic attraction, hydrophobic force, hydrogen bonding and aromatic stacking interaction. Papain interacted with the major groove of ctDNA. Aromatic stacking interaction is the main reason of change of absorption spectrum and fluorescence quenching of papain. Surface enhanced scattering effect, resonance energy transfer effect, increase of molecular volume and conformational change make contribution to RRS enhancement. The enhanced RRS intensity (ΔI) is directly proportional to the concentration of ctDNA or papain. The detection limit (3σ) is 5.2 ng·mL⁻¹ for ctDNA and 5.6 ng·mL⁻¹ for papain. This creates conditions for determination of papain and ctDNA.

In weak acid medium, eosin Y (EY) has a strong absorption band in the visible light region, and the maximum absorption wavelength (λ_max) is at 517 nm. There is no light absorption for polyvinylpyrrolidone (PVP) in 250–700 nm. When EY was reacted with PVP to form a binding product, a fading reaction of EY appeared and the maximum fading wavelength was still located at 517 nm. At the same time, a smaller absorption peak was observed at 545 nm. The extent of the fading (ΔA) is directly proportional to the concentration of PVP in the range of 0.40–3.20 mg· L⁻¹. The fading reaction has high sensitivity. The molar absorptivity (ε) is 6.4×10⁶ L·mol⁻¹·cm⁻¹ and the detection limit for PVP is 0.12 mg·L⁻¹. The influencing factors for the reaction have been studied, and the results show that the selectivity is good. Based on this fact, a new fading spectrophotometric method for the determination of PVP with EY has been developed, which is simple and rapid, and it can be applied to the quantitative determination of PVP in beer samples.

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.

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.

Heated in a boiling water bath, penicillin antibiotics such as amoxicillin, ampicillin, sodium cloxacillin, sodium carbenicillin and sodium benzylpenicillin could react with K₃[Fe(CN)₆] to form combined products in a dilute HCl medium. As a result, resonance Rayleigh scattering (RRS) intensity was enhanced greatly and new RRS spectra appeared. The maximum scattering wavelengths of the five combined products are all located at 330 nm. The scattered intensity increments (ΔI) of the combined products are directly proportional to the concentrations of the antibiotics in a certain range. The methods exhibit high sensitivity, and the detection limits for the five penicillin antibiotics are between 4.61 and 5.62 ng·mL⁻¹. The spectral characteristics of RRS and the optimum reaction conditions were investigated. The mechanism of reaction and the reasons for the enhancement of resonance light scattering were discussed. The effects of coexisting substances have been examined, and the results indicated that the method had a good selectivity. It can be applied to the determination of penicillin antibiotics in capsule, tablet, human serum and urine samples.

In pH 4.5–4.8 Britton-Robinson buffer solution, rifamycin SV (i.e. rifamycin sodium) can react with serum albumin such as human serum albumin (HSA) and bovine serum albumin (BSA) to form macromolecular complexes by electrostatic attraction and hydrophobic force. As a result, the resonance Rayleigh scattering (RRS) of the drug was enhanced remarkably and the RRS peaks were at 374 and 552 nm. The enhancement of RRS (ΔI) is directly proportional to the concentration of HSA or BSA. The linear ranges and the detection limits are 0.03–6.0 µg/mL and 9.0 ng/mL for HSA, and 0.01–8.0 µg/mL and 2.0 ng/mL for BSA, respectively. In this work, a sensitive, selective, simple and fast method for the determination of trace amounts of serum albumin by RRS technique has been developed, which was applied to the determination of serum albumin in the synthesized samples and human urine samples with satisfactory results.

Eu₂O₃nanorods were synthesized and characterized. The crystallites of Eu₂O(CO₃)₂·H₂O nanorods and Eu₂O₃ nanorods were obtained by means of surfactant assistance, with aqueous butanol solution as the solvent and hexamethylene tetramine as the base. The characteristics of the nanorods were analyzed by transmission electron microscopy, high-resolution transmission electron microscopy, scanning electron microscopy and X-ray diffraction. The Eu₂O₃ nanorod is about 80–300 nm in diameter and 1–5 µm in length. The formation mechanism of the 1D products was also proposed.

In pH 4.9 Britton-Robinson buffer solution, methotrexate (MTX) reacted with thallium(III) to form a 3:1 chelate. This resulted in great enhancement of second-order scattering (SOS) spectra and frequency doubling scattering (FDS) spectra and appearance of new SOS and FDS spectra. Their maximum wavelengths were located at 520 and 390 nm, respectively. The increments of scattering intensities (ΔI) were directly proportional to the concentrations of MTX in the ranges of 0.022–2.0 µg·mL⁻¹ (SOS method) and 0.008–2.5 µg·mL⁻¹ (FDS method). The methods exhibited high sensitivities. The detection limits for MTX were 7.4 ng·mL⁻¹ (SOS method) and 2.3 ng·mL⁻¹ (FDS method), respectively. The optimum conditions of the reaction, the influencing factors and the effects of coexisting substances were investigated. A highly sensitive, simple and fast method for the determination of MTX has been developed. The method can be applied satisfactorily to the determination of MTX in human serum samples. In this work, the charge distribution of MTX was calculated by a CNDO quantum chemistry method. In addition, the reaction mechanism was discussed.

In pH 5.0–5.4 HOAc-NaOAc buffer solution, clindamycin (Clin) could react with Pd(II) to form a 1:1 cationic chelate, which could further react with halofluorescein dyes such as diiodofluorescein (DIF), erythrosine (Ery) and eosin Y (EY) to form 1:1 ion-association complexes. As a result, not only the absorption and fluorescence spectra were changed, but also the resonance Rayleigh scattering (RRS) intensities enhanced greatly and new RRS spectra appeared. The three reaction products had characteristic RRS spectra and their maximum RRS wavelengths were located at 285 (DIF system), 287 (Ery system) and 321 (EY system) nm, respectively. The scattering intensities were proportional to the concentration of Clin in certain range which could be applied to determine Clin. The linear ranges and detection limits of Clin were 0.025–2.1 µg·mL⁻¹ and 7.8 ng·mL⁻¹ for the DIF system, 0.053–2.4 µg·mL⁻¹ and 16.0 ng·mL⁻¹ for the Ery system, 0.038–2.4 µg·mL⁻¹ and 11.0 ng·mL⁻¹ for the EY system, respectively. In this work, the optimum reaction conditions and the foreign substances were investigated. A simple, sensitive and fast method was developed for the determination of Clin either in the pharmaceutical form or in the human body fluid. Moreover, the composition, structure, reaction mechanism of the ternary complexes and their effects on the absorption, fluorescence and RRS spectra as well as the reasons of RRS enhancement were discussed.

In weak acidic medium, the anticancer antibiotics bleomycin A₅ (BLMA₅) and bleomycin A₂ (BLMA₂) bind with halofluorescein dyes, such as erythrosin (Ery), eosin Y (EY) and eosin B (EB), to form ion-association complexes, which causes fluorescence quenching of halofluorescein dyes. The quenching values (ΔF) are directly in proportional to the concentrations of bleomycins over the range 0.09–2.5 µg/mL. Based on this, a fluorescence quenching method for the determination of BLMA₅ and BLMA₂ has been developed. The dynamic range is 0.12–2.5 µg/mL for the determination of BLMA₅ and 0.09–2.0 µg/mL for BLMA₂, with detection limits (3σ) of 0.04 µg/mL for BLMA₅, 0.03 µg/mL for BLMA₂, respectively. It has been applied to determine the two antibiotics in human serum, urine and rabbit serum samples. The recovery is in the range 90–102%. In this work, the optimum reaction conditions and the spectral characteristics of the fluorescence are investigated. The reasons for fluorescence quenching are discussed, based on the fluorescence theory. Copyright © 2007 John Wiley & Sons, Ltd.