Second-order Scattering Method Research Articles

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 of4.5. 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 λex /λem = 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.

Surface state-regulated redox carbon nanodots for plasmonic morphology-dependent ratiometric sensing

Controlled-synthesis of carbon nanodots (CNDs) with tunable properties has always been challenging. Here, novel CNDs (blue-emitting CNDs (b-CNDs) and green-emitting CNDs (g-CNDs)) with tunable redox abilities and emission are synthesized via one-pot hydrothermal method. The redox ability of CNDs is regulated by surface state tailoring. The abundant reductive groups on the surfaces endow the b-CNDs appealing reducibility, whereas g-CNDs with fewer surface functional groups are deficient in reducibility. Using HAuCl4 indicator, the distinct reducibility of CNDs is visually identified. Gold salts are reduced to Au nanobelts under reduction and stabilization of b-CNDs, causing plasmons-induced color changes, whereas g-CNDs have no reduction effect on Au3+. The size-evolution process of Au nano-species can guide not only plasmonic absorbance alteration but also fluorescence (FL) and second-order scattering (SOS) changes. Therefore, based on the plasmonic morphology-induced SOS increasement and the Förster resonance energy transfer-induced FL switch off, the b-CNDs contribute to a ratiometric sensor coupled with FL and SOS for Au3+ detection. The ratiometric strategy displays a better sensitivity and selectivity and a broader linear range than single-signal SOS or FL method. The regulation of redox CNDs and ratiometric assay of Au3+ provide a new prospect for the preparation and application of versatile CNDs.

Dynamic Aggregation of Poly-N-Isopropylacrylamide Characterized Using Second-Order Scattering.

A second-order scattering (SOS) method is presented for the characterization of aqueous particle suspensions undergoing aggregation. Scattering intensities are measured at 90° by a standard fluorimeter and referenced against dynamic light scattering (DLS) measurements to determine particle size increase in a metal-promoted aggregation process for 0.05 mg/mL aqueous poly-N-isopropylacrylamide (PNIPAm), MW ∼10 k g/mol. Particle size increases monotonically from 30 nm to 210 nm at temperature 308 K. A further validation of the SOS method was performed using monodisperse polystyrene reference particles sized at 52 nm, 101 nm, 151 nm, and 206 nm, which demonstrated the technique's accuracy to within 6% and its versatility with respect to sample composition. The technique is ideal for monitoring colloidal stability and macromolecular assembly and it can be performed at lower concentrations than are typically used in DLS.

Study on interaction between palladium(ІІ)–Linezolid chelate with eosin by resonance Rayleigh scattering, second order of scattering and frequency doubling scattering methods using Taguchi orthogonal array design

Linezolid reacted with palladium to form 1:1 binary cationic chelate which further reacted with eosin dye to form 1:1 ternary ion association complex at pH 4 of Walpole’s acetate buffer in the presence of methyl cellulose. As a result not only absorption spectra were changed but Resonance Rayleigh Scattering (RRS), Second-order Scattering (SOS) and Frequency Doubling Scattering (FDS) intensities were greatly enhanced. The analytical wavelengths of RRS, SOS and FDS (λex/λem) of ternary complex were located at 538nm/538nm, 240nm/480nm and 660nm/330nm, respectively. The linearity range for RRS, SOS and FDS methods were 0.01–0.5μgmL−1, 0.1–2μgmL−1 and 0.2–1.8μgmL−1, respectively. The sensitivity order of three methods was as RRS>SOS>FDS. Accuracy of all methods were determined by recovery studies and showed recovery between 98% and 102%. Intraday and inter day precision were checked for all methods and %RSD was found to be less than 2 for all methods. The effects of foreign substances were tested on RRS method and it showed the method had good selectivity. For optimization of process parameter, Taguchi orthogonal array design L8(24) was used and ANOVA was adopted to determine the statistically significant control factors that affect the scattering intensities of methods. The reaction mechanism, composition of ternary ion association complex and reasons for scattering intensity enhancement was discussed in this work.

Study on the ternary system of MoO42--enzyme-PdCl2by 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.

A sensitive assay of erythrosine using enhanced resonance scattering signals with Fe(phen) 32+ in aqueous ethanol media

In a weak acidic Britton–Robinson buffer medium, erythrosine (Ery) can react with Fe(phen) 3 2+ to form 2:1 ion-association complex in the presence of ethanol, which will cause the remarkable enhancement of resonance Rayleigh scattering (RRS), second-order scattering (SOS), and frequency doubling scattering (FDS) spectra, and the appearance of new spectra of RRS, SOS, and FDS. The maximum wavelengths ( λ ex/ λ em) of the ion-association complex are located at 350 nm/350 nm for RRS, 280 nm/560 nm for SOS, and 780 nm/390 nm for FDS, respectively. The increments of scattering intensities (Δ I) are directly proportional to the concentration of Ery in a certain range. The detection limits for Ery are 5.6 ng mL −1 for RRS method, 13 ng mL −1 for SOS method, and 17 ng mL −1 for FDS method, respectively. Based on the above researches, a new highly sensitive and simple method for the determination of Ery has been developed. In this work, the spectral characteristics of RRS, SOS, and FDS spectra, the optimum conditions of the reaction and influencing factors were investigated. In addition, the reaction mechanism was discussed.

Resonance Rayleigh scattering, second-order scattering and frequency doubling scattering spectra for studying the interaction of erythrosine with [formula omitted] and its analytical application

In a weak alkaline Britton–Robinson buffer medium, erythrosine (Ery) can react with Fe ( phen ) 3 2 + to form 1:1 ion–association complex, which will cause not only the changes of the absorption spectra, but also the remarkable enhancement of resonance Rayleigh scattering (RRS), second-order scattering (SOS) and frequency doubling scattering (FDS) spectra, and the appearance of new spectra of RRS, SOS and FDS. The maximum RRS, SOS and FDS wavelengths ( λ ex/ λ em) of the ion–association complex are located at 358/358 nm, 290/580 nm and 780/390 nm, respectively. The increments of scattering intensities (Δ I) are directly proportional to the concentration of Ery in a certain range. The detection limits for Ery are 0.028 μg mL −1 for RRS method, 0.068 μg mL −1 for SOS method and 0.11 μg mL −1 for FDS method, respectively. Among them, the RRS method has the highest sensitivity. Based on the above researches, a new highly sensitive and simple method for the determination of Ery has been developed. In this work, the spectral characteristics of absorption, RRS, SOS and FDS spectra, the optimum conditions of the reaction and influencing factors for the RRS, SOS and FDS intensities were investigated. In addition, the reaction mechanism was discussed.

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.

Resonance Rayleigh Scattering, Second-Order Scattering and Frequency Doubling Scattering Spectra of Copper(II)-Flutamide System with Anionic Surfactants and its Analytical Application

A simple, sensitive, and rapid method based on ion association, for the determination of FLD has been developed. Flutamide (FLD) can react with Cu(II) to form 1:1 cationic chelate at pH 2.2-7.0 Mclivaine buffer medium, which can further react with anionic surfactants (AS) such as sodium dodecyl sulfate (SDS), sodium lauryl sulfonate (SLS) and sodium dodecylbenzene sulfonate (SDBS) to form 1:1 ion-association complexes. As a result, the resonance Rayleigh scattering (RRS), second-order scattering (SOS) and frequency doubling scattering (FDS) were enhanced to the highest degree. The maximum RRS, SOS and FDS wavelengths of three ion-association complexes were located at 345/345 nm, 610/305 nm and 430/860 nm, respectively. The increments of scattering intensity (ΔI) were directly proportional to the concentration of FLD in certain ranges. The detection limits (3σ) of FLD for SDS, SLS and SDBS systems were 1.9 ng ml(-1), 2.1 ng ml(-1) and 2.2 ng ml(-1)(RRS method), 2.4 ng ml(-1), 2.7 ng ml(-1) and 2.6 ng ml(-1) (SOS method) and 2.3 ng ml(-1), 2.4 ng ml(-1) and 2.5 ng ml(-1) (FDS method), separately. The sensitivity of RRS method was higher than those of FDS and SOS methods. The optimum conditions of RRS method and the influence factors, the composition and the reaction mechanism have been discussed. Since the method is highly selective, it does not interference concomitant substances. These methods were applied successfully for the determination of FLD in pharmaceutical formulation and urine samples.

Study on the interaction between palladium(II)-chlorpromazine hydrochloride and sodium tungstate by the resonance Rayleigh scattering, second-order scattering and frequency doubling scattering spectra and its analytical application

The interaction between palladium(II)-chlorpromazine hydrochloride and sodium tungstate was investigated by ultraviolet-visible absorption, resonance Rayleigh scattering (RRS), second-order scattering (SOS) and frequency doubling scattering (FDS) spectroscopy. In pH 5.3 Britton-Robinson (BR) buffer medium, chlorpromazine hydrochloride (CPZ) reacted with Pd(II) to form 2:1 cationic chelate, which further reacted with Na2WO4 to form a 1:1 ternary ion-association complex ([Pd(CPZ)2]·WO4). As a result, the signal intensities of RRS, SOS and FDS were enhanced greatly, and the enhancements of scattering were proportional to the CPZ concentration in a certain range. Their maximum wavelengths were located at 310 nm, 570 nm and 391 nm, respectively and the detection limits (3σ) were 1.6 ng/mL (RRS method), 3.2 ng/mL (SOS method) and 5.6 ng/mL (FDS method). The optimum reaction conditions, the influences of coexisting substances and analytical application were mainly investigated by RRS method due to its highest sensitivity. A highly sensitive, simple, rapid and new method had been proposed to determine CPZ in the pharmaceutical form and residue of CPZ in pork. In addition, the Gibbs free energy change (δGf) of ion-association reaction was computed by using B3LYP/3-21g*/LanL2dz method. The formation of ion-association and the reasons for the enhancement of RRS were also discussed.

Determination of Promethazine Hydrochloride with Palladium(II) and Na2WO4 by Resonance Rayleigh Scattering and Resonance Nonlinear Scattering Spectra

ABSTRACT In a weak acidic medium, promethazine hydrochloride (PMZ) reacted with Pd(II) to form 2:1 cationic chelate ([Pd(PMZ)2]2+), it further reacted with Na2WO4 by virtue of electrostatic attraction and hydrophobic force to form 1:1 ternary ion-association complex ([Pd(PMZ)2] · ()), which can result in the large-scale enhancement of the resonance Rayleigh scattering (RRS), second-order scattering (SOS) and frequency doubling scattering (FDS). The maximum RRS, SOS and FDS peaks of [Pd(PMZ)2] · were located at 310 nm, 570 nm and 391 nm, respectively, and the enhancements of scattering were proportional to the concentration of PMZ in the range of 0.0081–2.6 µg mL−1 (RRS method), 0.02–3.0 µg mL−1 (SOS method) and 0.08–2.6 µg mL−1 (FDS method). Above three methods' detection limits (3σ) were 2.1 ng mL−1, 4.4 ng mL−1 and 6.6 ng mL−1 respectively. Using Pd(II) and Na2WO4 as probe, we have developed three new, sensitive, and rapid methods for the determination of PMZ. The RRS method was applied in the determination of PMZ in the pharmaceutical form with satisfactory results. In this work, the optimal reaction conditions and the influences of coexisting substances were investigated, the composition of ion-association complex and the reaction mechanism were also discussed by the RRS method.

Determination of Chondroitin Sulfate A by Resonance Rayleigh Scattering and Resonance Non-linear Scattering with Proteins as Probes

In a pH 2. 5 ～ 4. 0 Britton-Robinson( BR) buffer medium,some proteins such as bovine serum albumin( BSA) ,Chymotrypsin( Chy) and α-amylase( α-Amy) can react with chondroitin sulfate A( CS) via electrostatic force,hydrogen bond force or/and hydrophobic force to form binding products. As a result,the resonance Rayleigh scattering( RRS) ,second-order scattering( SOS) and frequency doubling scattering( FDS) were enhanced greatly with new scattering spectra appeared. The increments of scattering intensity( ΔI) were proportional to the concentration of CS in certain ranges. The detection limits( 3σ) of CS in Chy,BSA and α-Amy systems were 1. 4,2. 0 and 1. 8 μg/L( RRS method) ,2. 3,2. 9 and 2. 5 μg/L( SOS method) ,5. 8,13. 2 and 9. 6 μg/L ( FDS method) ,respectively. Among them,the RRS method exhibited the highest sensitivity and the Chy-CS system was more sensitive than others. The characteristics of the spectra and optimal conditions of RRS method were investigated. The effects of external substances were tested. The established methods have a good selectivity and can be applied to the determination of CS in eye drops with satisfactory results.

The interaction between furosemide-palladium (II) chelate and basic triphenylmethane dyes by resonance Rayleigh scattering spectra and resonance non-linear scattering spectra and their analytical applications

In pH 4.5–7.0 Britton-Robinson buffer solution, furosemide (FUR) reacted with Pd (II) to form a 1:1 anionic chelate. This chelate could further react with such basic triphenylmethane dyes (BTPMD) as ethyl violet (EV), crystal violet (CV), methyl violet (MV), methyl green (MeG) and brilliant green (BG) to form 1:1 ion-association complexes. This not only resulted in the change of absorption spectra, but also led to the significant enhancement of resonance Rayleigh scattering (RRS), second-order scattering (SOS) and frequency doubling scattering (FDS). The maximum RRS wavelengths were located at 324 nm for the EV, CV and MV system, and 340 nm for the BG and MeG system. The maximum SOS wavelengths were located at 550 nm for the EV, CV, BG and MeG system, and 530 nm for the MV system. The maximum scattering peaks of all the systems were at 392 nm for FDS. The enhanced RRS, SOS and FDS intensities were directly proportional to the concentration of FUR. The detection limits for the different dye systems were 0.3–4.9 ng mL−1 for the RRS method, 3.2–33.1 ng mL−1 for the SOS method and 9.0–85.7 ng mL−1 for the FDS method. These methods could be used for the determination of trace amounts of FUR. The effects of the formation of ternary ion-association complexes on the spectral characteristics and intensities of absorption, RRS, SOS and FDS have been investigated. The optimum conditions of these reactions, the influencing factors and the analytical properties have been tested. The influences of coexisting substances were tested by RRS method and the results showed that this method exhibited a high sensitivity. Based on the aforementioned research, the highly sensitive, simple and rapid methods for the determination of trace amounts of FUR by resonance light scattering technique have been established, which could be applied to the determination of FUR in tablet, injection, human serum and urine samples. The composition and structure of the ternary ion-association complex and the reaction mechanism were discussed.

Study on the resonance nonlinear scattering spectra of the interactions of promethazine hydrochloride and chlorpromazine hydrochloride with 12-tungstophosphoric acid and their analytical applications

In pH 1.0 HCl medium, 12-tungstophosphoric acid (TP) reacted with promethazine hydrochloride (PMZ) and chlorpromazine hydrochloride (CPZ) to form ion-association complexes, which led to a great enhancement of the resonance nonlinear scattering such as second-order scattering (SOS) and frequency doubling scattering (FDS). Their maximum SOS and FDS peaks were located at 585 nm (TP–PMZ), 584 nm (TP–CPZ) and 388 nm (TP–PMZ), 329 nm (TP–CPZ), respectively. These results provided some indication for the determination of PMZ and CPZ by SOS and FDS methods. The linear range of TP–PMZ and TP–CPZ systems were 0.0069–2.5 μg mL −1, 0.102–5.0 μg mL −1 (SOS) and 0.079–6.0 μg mL −1, 0.0133–5.0 μg mL −1 (FDS), respectively. The detection limits (3 σ) of PMZ and CPZ were 2.08 ng mL −1, 3.07 ng mL −1 (SOS) and 2.22 ng mL −1, 3.98 ng mL −1 (FDS), respectively. In this work, the optimum reaction conditions, the influences of coexisting substances and ionic strength and analytical application have been investigated. The methods have been successfully applied to the determination of PMZ and CPZ in tablets. In addition, the composition of ion-association complexes and the reaction mechanism are also discussed.

The investigation of the interactions between CdSe quantum dots and human serum albumin by resonance Rayleigh scattering and second-order scattering spectra

Human serum albumin (HSA) was the most abundant protein in human plasma and has significant physiological function. In Tris–HCl buffer solution (pH 7.4), water-soluble semiconductor CdSe quantum dots (QDs) reacted with HSA and the products resulted in a great enhancement of the intensity of resonance Rayleigh scattering (RRS) and second-order scattering (SOS). Based on this, a new method was developed to investigate the interactions between QDs and HSA. The parameters with regard to determination were optimized, and the reaction mechanism was discussed. Under optimal conditions, the increments of scattering intensity (Δ I) were directly proportional to the concentrations of HSA in the range of 0.4–48.0 μmol L −1. The detection limits were 0.10 μmol L −1 for RRS method and 0.25 μmol L −1 for SOS method. The proposed method was sensitive, simple and rapid. It has been successfully applied to the determination of HSA in human urine samples. Analytical results obtained with this novel assay were satisfactory.

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, gamma-globulin, alpha-chymotrypsin and papain could react with [PdI(4)](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 [PdI(4)](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.

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 (Δ I) 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 (3 σ) 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.

Novel and sensitive methods for the determination of dopamine based on the resonance Rayleigh scattering, second-order scattering and frequency doubling scattering quenching effects

Three novel methods were designed for the determination of dopamine (DA) by means of the quenching effects on resonance Rayleigh scattering (RRS) and non-linear scattering such as second-order scattering (SOS) and frequency doubling scattering (FDS) intensities. In Britton–Robinson buffer medium (pH 6.02), I 3 − could react with DA to produce I −, which resulted in the decreases of the RRS, SOS and FDS intensities of the ethyl violet (EV)–I 3 − system, and the decreases of scattering intensity (Δ I) were directly proportional to the concentrations of DA in a certain range. The detection limit (3 σ) for DA was 0.0195 μmol/L for the RRS method, 0.286 μmol/L for the SOS method and 0.0985 μmol/L for the FDS method, respectively. In this work, the characteristics of absorption, RRS, SOS and FDS spectra of this reaction have been studied; the optimum reaction condition and influencing factors have been investigated. The methods were applied to the determination of DA in pharmaceutical samples with satisfactory results.

Second‐order Scattering and Frequency Doubling Scattering Spectra of Thallium(III)‐Methotrexate System and Its Analytical Application

AbstractIn 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.

Resonance Rayleigh scattering, second-order scattering and frequency doubling scattering methods for the indirect determination of penicillin antibiotics based on the formation of Fe 3[Fe(CN) 6] 2 nanoparticles

Under the HCl solution and heating condition, penicillin antibiotics such as amoxicillin (AMO), ampicillin (AMP), sodium cloxacillin (CLO), sodium carbenicillin (CAR) and sodium benzylpenicillin (BEN) could react with Fe(III) to produce Fe(II) which further reacted with Fe(CN) 6 3− to form a Fe 3[Fe(CN) 6] 2 complex. By virtue of hydrophobic force and Van der Waals force, the complex aggregated to form Fe 3[Fe(CN) 6] 2 nanoparticles with an average diameter of 45 nm. This resulted in a significant enhancement of resonance Rayleigh scattering (RRS) and non-linear scattering such as second-order scattering (SOS) and frequency doubling scattering (FDS). The increments of scattering intensity (Δ I) were directly proportional to the concentrations of the antibiotics in a certain range. The detection limits for the five penicillin antibiotics were 2.9–6.1 ng ml −1 for RRS method, 4.0–6.8 ng ml −1 for SOS method and 7.4–16.2 ng ml −1 for FDS method, respectively. Among them, the RRS method exhibited the highest sensitivity and the AMO system was more sensitive than other antibiotics systems. Based on the above researches, a new highly sensitive and simple method for the indirect determination of penicillin antibiotics has been developed. It can be applied to the determination of penicillin antibiotics in capsule, tablet, human serum and urine samples. In this work, the spectral characteristics of absorption, RRS, SOS and FDS spectra, the optimum conditions of the reaction and the influencing factors were investigated. In addition, the reaction mechanism was discussed.