Resonance Rayleigh scattering spectral method for the determination of raloxifene using gold nanoparticle as a probe

When gold nanoparticles were being prepared by sodium citrate reduction method, citrate anions self-assembled on the surface of gold nanoparticles to form supermolecular complex anions with negative charges, and protonated raloxifene (Ralo) was positively charged and could bind with the complex anions to form larger aggregates through electrostatic force and hydrophobic effects, which could result in the remarkable enhancement of the resonance Rayleigh scattering intensity (RRS), and the appearance of new RRS spectra. At the same time, the second-order scattering (SOS) and frequency-doubling scattering (FDS) intensities were also enhanced. The maximum wavelengths were located near 370 nm for RRS, 520 nm for SOS, and 350 nm for FDS, respectively. Among them, the RRS method had the highest sensitivity and the detection limit was 5.60 ng mL⁻¹ for Ralo, and its linear range was 0.05-2.37 μg mL⁻¹. A new RRS method for the determination of trace Ralo using gold nanoparticles probe was developed. The optimum conditions of the reaction and influencing factors were investigated. In addition, the reaction mechanism and the reasons for the enhancement of RRS were discussed.     

Resonance Rayleigh scattering and resonance non-linear scattering method for the determination of aminoglycoside antibiotics with water solubility CdS quantum dots as probe

In pH 6.6 Britton–Robinson buffer medium, the CdS quantum dots capped by thioglycolic acid could react with aminoglycoside (AGs) antibiotics such as neomycin sulfate (NEO) and streptomycin sulfate (STP) to form the large aggregates by virtue of electrostatic attraction and the hydrophobic force, which resulted in a great enhancement of resonance Rayleigh scattering (RRS) and resonance non-linear scattering such as second-order scattering (SOS) and frequency doubling scattering (FDS). The maximum scattering peak was located at 310 nm for RRS, 568 nm for SOS and 390 nm for FDS, respectively. The enhancements of scattering intensity (ΔI) were directly proportional to the concentration of AGs in a certain ranges. A new method for the determination of trace NEO and STP using CdS quantum dots probe was developed. The detection limits (3σ) were 1.7 ng mL⁻¹ (NEO) and 4.4 ng mL⁻¹ (STP) by RRS method, were 5.2 ng mL⁻¹ (NEO) and 20.9 ng mL⁻¹ (STP) by SOS method and were 4.4 ng mL⁻¹ (NEO) and 25.7 ng mL⁻¹ (STP) by FDS method, respectively. The sensitivity of RRS method was the highest. The optimum conditions and influence factors were investigated. In addition, the reaction mechanism was discussed.     

Effects of interaction of folic acid with uranium (VI) and basic triphenylmethane dyes on resonance Rayleigh scattering spectra and their analytical applications

In pH 4.2-4.8 HAc-NaAc buffer solution, folic acid (FA) could react with uranium (VI) to form a 2:1 anionic chelate which further reacted with some basic triphenylmethane dyes (BTPMD) such as Ethyl Violet (EV), Methyl Violet (MV) and Crystal Violet (CV) to form 1:2 ion-association complexes. As a result, not only the absorption spectra were changed, but also the intensities of resonance Rayleigh scattering (RRS) were enhanced greatly and the new RRS spectra were observed. The maximum RRS wavelengths were located at 328 nm for EV system, 325 nm for MV system and 328 nm for CV system. The fading degree (ΔA) and RRS intensities (ΔI) of three systems were different. Under given conditions, the ΔA and ΔI were all directly proportional to the concentration of FA. The linear ranges and the detection limits of RRS methods were 0.0039-5.0 μg mL⁻¹ and 1.2 ng mL⁻¹ for EV system, 0.0073-4.0 μg mL⁻¹ and 2.2 ng mL⁻¹ for MV system, 0.014-3.5 μg mL⁻¹ and 4.7 ng mL⁻¹ for CV system. The RRS methods exhibited higher sensitivity, so they are more suitable for the determination of trace FA. The optimum conditions, the influencing factors and the effects of coexisting substances on the reaction were investigated. The method can be applied to the determination of FA in serum and urine samples with satisfactory results. The structure of the ternary ion-association complex and the reaction mechanism were discussed in this work.     

Study on the resonance Rayleigh scattering spectra and resonance non-linear spectra of congo red-amikacin system and its analytical application

The interaction between congo red (CR) and amikacin (AMK) was studied by resonance Rayleigh scattering (RRS), frequency doubling scattering (FDS) and second-order scattering (SOS) combining with absorption spectrum. In a weak acidic medium, CR combined with AMK to form an ion association complex with the composition ratio of 1∶1 by electrostatic interaction, hydrophobicity and charge transferring effect. As a result, the new spectra of RRS, FDS, and SOS appeared and their intensities were enhanced greatly. The maximum wavelengths of RRS, FDS and SOS were located at 563 nm, 475 nm and 940 nm, and the scattering intensities were proportional to the concentration of AMK. These three methods have very high sensitivities, and the detection limits were 4.0 ng·mL?1 for RRS, 3.6 ng·mL?1 for FDS and 1.9 ng·mL?1 for SOS, respectively. At the same time, the methods have better selectivity. A new method for the determination of trace amounts of AMK with congo red by resonance scattering technique has been developed. The recovery for the determination of AMK in blood serum and urine sample was between 95.5% and 105.5%. In this study, the properties, such as enthalpy of formation, charge distribution and mean polarizability, were calculated by AM1 quantum chemistry method. In addition, the reaction mechanism and the reasons for the enhancement of scattering spectra were discussed.     

Ferric nanoparticle-based resonance light scattering determination of DNA at nanogram levels

A novel assay of DNA has been proposed by using ferric nanoparticles as probes coupled with resonance light scattering (RLS) detection. At pH 7.40, the RLS intensity of ferric nanoparticles can be greatly enhanced by the aggregation of positively charged ferric nanoparticles through electrostatic interaction with negatively charged DNA. The enhanced intensity of RLS at 452 nm is proportional to the concentration of DNA in the range of 0.01-0.8 μg ml⁻¹ for calf thymus and salmon sperm DNA and in the range of 0.005-0.3 μg ml⁻¹ for E. coli K12 genomic DNA. Detection limits are 3.6 ng ml⁻¹ for calf thymus DNA, 4.4 ng ml⁻¹ for salmon sperm DNA, and 1.9 ng ml⁻¹ for E. coli K12 genomic DNA, respectively. Compared with the chromophores previously used in RLS assay, the ferric nanoparticles have offered several advantages in easy preparation, good photostability and high sensitivity without being modified or functionalized.     

Analytical Application of Resonance Rayleigh Scattering,Frequency Doubling Scattering,and Second-Order Scattering Spectra for the Sodium Alginate-CTAB System

Three new methods for the determination of trace amounts of sodium alginate (SA) based on the reaction of SA with cetyltrimethylammonium bromide (CTAB) by resonance Rayleigh scattering (RRS), frequency doubling scattering (FDS), and second-order scattering (SOS) have been investigated. The SA can react with CTAB in a pH 10.0 Britton–Robinson buffer to form a new product, which can lead to a significant enhancement of RRS, FDS, and SOS intensities and appearance of new spectra. The maximum scattering wavelengths, λex/λem, appear at 351 nm/351 nm for RRS, 240 nm/480 nm for SOS, and 870 nm/435 nm for FDS, respectively. The increments of the scattering intensities (ΔI) are proportional to the concentration of SA in a certain range. The detection limits (3σ) for SA are 3.69 ng mL^?1 for the RRS method, 6.91 ng mL^?1 for the FDS method, and 7.45 ng mL^?1 for the SOS method under optimum conditions. The proposed methods were applied to the determination of SA in real samples with satisfactory results.     

A dual-wavelength resonance light scattering ratiometry of biopolymer by its electrostatic interaction with surfactant

A dual-wavelength resonance lighting scattering (DW-RLS) ratiometry is developed to detect anion biopolymer based on their bindings with cation surfactant. Using the interaction of Hyamine 1622 (HM) with fish sperm DNA (fsDNA) as an example, a dual-wavelength resonance light scattering (DW-RLS) ratiometric method of DNA was constructed. In Britton-Robinson buffer controlled medium, fish sperm DNA (fsDNA) could interact with Hyamine 1622 (HM), displaying significantly enhanced RLS signals. By measuring the RLS signals characterized at 300.0 nm (I_300.0) and the RLS intensity ratio (I_276.0/I_294.0), respectively, fsDNA over a wide dynamic range of content could be detected. Typically, when HM concentration is kept at 6.0 × 10⁻⁵ mol l⁻¹, using I_300.0 could detect fsDNA over the range of 50-2000 ng ml⁻¹ with the limit of 3.0 ng ml⁻¹, while using I_276.0/I_294.0 could detect fsDNA over the range of 0.5-2500 ng ml⁻¹ with the limit of 0.05 ng ml⁻¹. Thus the latter so-called DW-RLS ratiometry is obviously superior to the former one. Based on the measurements of I_300.0 and I_276.0/I_294.0 data, a Scatchard plot concerning the interaction between HM and fsDNA could be constructed and thus the binding number (n) and binding constant (K) could be available with the values of 13.5 and 1.35 × 10⁵ mol⁻¹ l, and 11.9 and 1.65 × 10⁵ mol⁻¹ l, respectively.     

Room-temperature luminescence optosensings based on immobilized active principles actives: Application to nafronyl and naproxen determination in pharmaceutical preparations and biological fluids

This paper presents two easy and selective methods for determining the active principles nafronyl (NFL) and naproxen (NAP), using a flow-through fluorescence optosensor based on the on-line immobilization on a nonionic-exchanger (Silica Gel, Davisil™ and Amberlite XAD 7, respectively) solid support. The determination was performed in 5×10⁻³ M HAc/NaAc buffer solution at pH 5 for NFL and 15×10⁻³ M glycine/HCl buffer solution at pH 2.5 for NAP at a working temperature of 20 °C. The fluorescence intensities were measured at λ_ex/em=294/336 nm and λ_ex/em=332/354 nm for NFL and NAP, respectively. The response time for these optosensors were practically instant, obtaining a linear concentration range between 0 and 700.0 ng ml⁻¹ with a detection limit of 20.8 ng ml⁻¹, an analytical sensitivity of 10.1 ng ml⁻¹ and a standard deviation of 1.27% at a 500 ng ml⁻¹ concentration level for NFL and a linear concentration range between 0 and 200.0 ng ml⁻¹ with the detection limit of 13.3 ng ml⁻¹, an analytical sensitivity of 6.0 ng ml⁻¹ and a standard deviation of 3.52% at a 100 ng ml⁻¹ concentration level for NAP. The proposed methods were satisfactorily applied to real samples (three commercial formulations and urine samples). The effects of the possible interferences were evaluated in all cases.     

Resonance Rayleigh scattering method for the recognition and determination of double-stranded DNA using amikacin

In weakly acidic buffer medium, the interaction of amikacin with calf thymus DNA, yeast RNA and denatured DNA has been investigated by using resonance Rayleigh scattering (RRS) technique. The result shows that calf thymus DNA is capable of enhancing the RRS intensity of the amikacin, while yeast RNA and denatured DNA have very little enhancement effect. Based on the characteristics, a sensitive assay for detecting double-stranded DNA in the presence of denatured DNA and yeast RNA has been developed. The enhancement of the RRS signal is directly proportional to the concentration of double-stranded DNA in the range 0.02-12.0 μg ml⁻¹ for calf thymus DNA and its detection limit (3σ) is 2.5 ng ml⁻¹. The method shows a wide linear range and high sensitivity, and almost no interference can be observed from RNA, denatured DNA, amino acid and most of the metal ions. The trace amounts of nucleic acid in synthetic samples and practical samples are determined with satisfactory results. Therefore, the proposed method is promising for as an effect means for recognition in vivo and determination in situ of double-stranded DNA.     

Study on Frequency Doubling Scattering and Second—Order Scattering Spectra of Heparin—Methylene Blue System

Binding of heparin with methylene blue(MB) in pH5.7 Britton-Robinson buffer can result in a significant enhancement of frequency doubling scattering (FDS) and second-order scattering (SOS).Their maximum scattering wavelengths(λmax) appear at 350nm for FDS and 700nm for SOS,respectively.The optimum conditions of the reaction,the influencing factors and the relationship between the two scattering intensities and the concentration of heparin have been investigated.The new methods for the determination of trace amounts of heparin bassed on the FDS and SOS methods have been developed,which exhibit high sensitivities.The detection limits of heparin are 4.36ng/mL for the FDS method and 3.55ng/mL for the SOS method,respectively.Both of the methods have fairly godd selectivity and ware applied to the determination of heparin in sodium heparinate injection samples with satisfactory results.Moreover,the relative mechamisms have also been discussed.     

Determination of verapamil hydrochloride with 12-tungstophosphoric acid by resonance Rayleigh scattering method coupled to flow injection system

A flow injection analysis (FIA) method coupled to resonance Rayleigh scattering (RRS) detection for the determination of verapamil hydrochloride (VP) was proposed. In pH 1.0 acidic medium, 12-tungstophosphoric acid (TP) reacted with VP to form an ion-association complex, which resulted in a significant enhancement of RRS intensity. The maximum scattering peak was located at 293 nm. RRS intensity was proportional to the concentration of VP in the range of 0.017-13.0 μg mL⁻¹, and the detection limit (3σ) was 5.1 ng mL⁻¹. The proposed method exhibited satisfactory reproducibility with a relative standard derivation (R.S.D.) of 2.1% for 11 successive determinations of 5.0 μg mL⁻¹ VP. Therefore, a novel method for the determination of VP by FIA-RRS was developed. The optimum reaction conditions and the parameters of the FIA operation such as flow rate, injection volume, reactor length, and so on had been optimized in this paper. The present method had been applied to the determination of VP in serum samples and pharmaceuticals with satisfactory results. The maximal sample throughput in the optimized system was 80 h⁻¹.     

Determination of proteins with Alizarin Red S by Rayleigh light scattering technique

A new protein determination method by enhanced Rayleigh light scattering (RLS) technique has been developed. In acid condition (pH=3.60), RLS of 1,2-dihydroxyanthraquinone-3-sulfonate (Alizarin Red S) can be greatly enhanced by addition of proteins, resulting in two characteristic peaks, 360 and 505 nm, respectively. The new protein assay is based on the RLS enhancement and spectrum change. The optimum condition for the reaction was investigated. The linear range is 0.20-24.9 μg ml⁻¹ for BSA and 0.20-15.5 μg ml⁻¹ for HSA. The detection limits (S/N=3) are 9.59 ng ml⁻¹ for BSA and 9.51 ng ml⁻¹ for HSA. The results of determination for human serum samples were comparable to those obtained by Bradford method. The binding stoichiometry was determined.     

Study of the interaction of Azur B with DNA and the determination of DNA based on resonance light scattering measurements

Based on the measurements of molecular absorption and resonance light scattering (RLS), the aggregation of Azur B (AB) was in a medium of pH ranging from 1.98 to 2.56 and ionic strength <0.12 M. The presence of double stranded DNA prompts the aggregation, resulting in enhanced RLS signals. Linear relationships were achieved between the enhanced RLS intensity at 359.7 nm and DNA concentration in the range of 0-4.5 μg ml⁻¹ for both calf thymus DNA (ctDNA) and fish sperm DNA (fsDNA) if 3.0×10⁻⁵ M AB was employed. The 3σ limits of detection were 9.3 and 8.9 ng ml⁻¹ for ctDNA and fsDNA, respectively. Five synthetic samples were analysed satisfactorily.     

Study on the resonance Rayleigh scattering spectra of the interactions of palladium (II)-cephalosporins chelates with 4,5-dibromofluorescein and their analytical applications

In pH 2.8-3.8 BR buffer medium, the third generation cephalosporin antibiotics (TGCs) such as ceftazidime (CZD), ceftriaxone (CTRX), cefoperazone (CPZ), and cefotaxime (CFTM) react with palladium(II) (Pd(II)) to form 1:2 yellowish-brown cationic chelates, which further react with 4, 5-dibromofluorescein (DBF) to form 1:3 brown ion-association complexes. As a result, not only the spectra of absorption and fluorescence are changed, but also the resonance Rayleigh scattering (RRS) is enhanced greatly and the new RRS spectra are observed. The four TGCs products have similar spectral characteristics and their maximum RRS wavelengths are all located at 291 nm. The quantitative determination ranges and the detection limits of the four TGCs are 0.0065-1.0 μg mL⁻¹ and 2.0 ng mL⁻¹ for CZD, 0.0070-1.1 μg mL⁻¹ and 2.2 ng mL⁻¹ for CTRX, 0.0090-1.6 μg mL⁻¹ and 2.7 ng mL⁻¹ for CPZ, and 0.014-2.2 μg mL⁻¹ and 4.2 ng mL⁻¹ for CFTM, respectively. The optimum conditions of the reactions and the effects of foreign substances are investigated, and the composition of ion-association complexes is discussed also. Based on the ion-association reaction, a highly sensitive, simple and rapid method has been proposed to the determination of TGCs.     

Direct quantification of γ-globulin in human blood serum by resonance light scattering techniques without separation of human serum albumin

We describe the preparation and characterization of functionalized nano-PbS. The functionalized nanoparticles are water-soluble. Reaction of mercaptoacetic acid functionalized nano-PbS with γ-globulin (γ-IgG) results in an enhanced resonance light scattering (RLS) at 385 nm. Based on this, a new direct quantitative method for γ-globulin in blood serum samples without separation of human serum albumin is established. Under optimal conditions, the enhanced RLS intensity is in proportion to the γ-IgG concentration in the range 10-500 ng ml⁻¹. The 3σ limit of detection is 2.75 ng ml⁻¹. The contents of γ-IgG in blood serum samples were determined with a recovery of 97-104% and R.S.D. of 1.5-2.1% (n=6). This method proved to be very sensitive, rapid, simple and tolerant of most interfering substances.     

Highly sensitive spectrofluorimetric kinetic determination of ultratrace amounts of vanadium(V) based on the oxidation of 1,8-diaminonaphthalene by bromate

A highly sensitive catalytic quenching spectrofluorimetric method was described for the determination of V(V) based on its catalytic effect on the oxidation of 1,8-diaminonaphthalene by potassium bromate with Tiron as an activator in weakly acidic medium and the reaction mechanism was investigated. The reaction was followed spectrofluorimetrically by measuring the fluorescence intensity of 1,8-diaminonathphlene (DAN) (λ_ex=356 nm, λ_em=439 nm) at a fixed time of 5 min from initiation of the reaction. Under the optimum conditions, vanadium(V) can be determined in the range 0.05-50.0 ng ml⁻¹ with a S.D.=0.024 for 15 times measurements. The detection limit of the method was down to 0.0088 ng ml⁻¹ and the catalytic reaction activation energy was found to be 43.92 kJ mol⁻¹. The proposed method was tested for the determination of vanadium(V) in rice and natural water samples.     

A novel spectrofluorimetric method for the ultra trace analysis of nitrite and nitrate in aqueous medium and its application to air, water, soil and forensic samples

A highly sensitive and virtually specific method has been developed for the trace and ultra trace 5 ng ml⁻¹-1 μg ml⁻¹ fluorimetric analysis of nitrite. The method is based on the quenching action of nitrite on the native fluorescence of murexide (ammonium purpurate) [λ_ex=349.0 nm, λ_em=444.5 nm] in the acid range of 0.045-0.315 (M) H₂SO₄. The method is very precise and accurate (S.D.=±0.4877 and R.S.D.=0.4878% for the determination of 0.1 μg ml⁻¹ of nitrite in 11 replicates). Relatively large excesses of over 35 cations and anions do not interfere. The proposed technique has been successfully applied for the determination of nitrite and nitrate in ground water, surface water and sea water, nitrite in soil and nitrate in forensic samples. The method has also been extended for the analysis of NO_x in air.     

A reversed-phase high performance liquid chromatography coupled with resonance Rayleigh scattering detection for the determination of four tetracycline antibiotics

A new reversed-phase high performance liquid chromatography with resonance Rayleigh scattering detection (HPLC-RRS) was developed for simultaneous separation and determination of four tetracycline antibiotics (TCs). A good chromatographic separation among the compounds was achieved using a Synergi Fusion-RP column (150 mm × 4.6 mm; 4 μm) and a mobile phase consisting of methanol-acetonitrile-oxalic acid (5 mM) at the flow rate of 0.8 mL min⁻¹. Column temperature was 30 °C. The RRS signal was detected at λ_ex = λ_em = 370 nm. The recoveries of sample added standard ranged from 95.3% to 103.5%, and the relative standard deviation was below 2.79%. A detection limit of 2.12-5.12 μg mL⁻¹ was reached and a linear range was found between peak height and concentration in the range of 10.36-518.0 μg mL⁻¹ for oxytetracycline (OTC), 12.11-605.5 μg mL⁻¹ for tetracycline (TC), 11.79-589.5 μg mL⁻¹ for chlortetracycline (CTC) and 10.32-516.0 μg mL⁻¹ for doxycycline (DC). The linear regression coefficients were all above 0.999. The method has been applied successfully to the determination of OTC, TC, CTC, DC in pharmaceutical formulations and in honey. The method was simple, rapid and showed a better linear relation and high repeatability.     

Two different spectrofluorimetric methods for simultaneous determination of gemfibrozil and rosiglitazone in human plasma

Two accurate, reliable, and highly sensitive spectrofluorimetric methods were developed for simultaneous determination of binary mixture gemfibrozil and rosiglitazone in human plasma without prior separation steps. The first method is based on synchronous fluorescence spectrometry using double scans. At Δλ = 27 nm, gemfibrozil yields detectable signal that is independent of the presence of rosiglitazone. Similarly, at Δλ = 120 nm the signal of rosiglitazone is not influenced by the presence of gemfibrozil. Signals at two wavelengths, 301 (Δλ = 27 nm) and 368 nm (Δλ = 120 nm) vary linearly with gemfibrozil and rosiglitazone concentrations over the range 100-700 ng mL⁻¹ (for gemfibrozil) and 20-140 ng mL⁻¹ (for rosiglitazone), respectively. The limits of detection (LOD) were 2.3 and 2.72 ng mL⁻¹ for gemfibrozil and rosiglitazone, respectively. The second method is based on the technique of simultaneous equations (Vierodt's method), in which 258 nm was selected as the excitation wavelength. Two equations are constructed based on the fact that at (λEm₂=302 nm of gemfibrozil) and (λEm₂=369 nm of rosiglitazone) the fluorescence of the mixture is the sum of the individual fluorescence of gemfibrozil and rosiglitazone. The limits of detection (LOD) were 28.1 and 23.63 ng mL⁻¹ for gemfibrozil and rosiglitazone, respectively. The proposed methods were successfully applied for the determination of the two compounds in synthetic mixtures and in human plasma with a good recovery.     

A study on the sizes and concentrations of gold nanoparticles by spectra of absorption, resonance Rayleigh scattering and resonance non-linear scattering

Liquid phase gold nanoparticles with different diameters and colors can be prepared using sodium citrate reduction method by controlling the amounts of sodium citrate. The mean diameters of gold nanoparticles are measured by transmission electron microscope (TEM). Gold nanoparticles with different sizes have specific absorption spectra. When the diameters of nanoparticles is between 12 and 41 nm, the maximum absorption peaks locate at 520-530 nm and there are red shifts gradually with the increase of diameters of gold nanoparticles. And when the size of gold nanoparticle is constant, the absorbance is proportional to the concentration of gold. Obvious resonance Rayleigh scattering (RRS) and the resonance non-linear scattering such as second-order scattering (SOS) and frequency-doubling scattering (FDS) appear at the same time as well, and the maximum scattering peaks are located at 286 nm (RRS), 480 nm (SOS) and 310 nm (FDS), respectively. When the concentration of gold is constant, absorbance and the intensities of RRS, SOS and FDS (I(RRS), I(SOS) and I(FDS)) have linear relationships with the diameters of gold nanoparticles. When the diameter of gold nanoparticle is constant, the absorbance and I(RRS), I(SOS), I(FDS) are directly proportional to the concentrations of gold nanoparticles. Therefore, it is very useful for studying the liquid phase gold nanoparticles by investigating the absorption, RRS, SOS and FDS spectra.