Ion Association Research Articles

Kinetic study on bimolecular photochemical quenching of tris(2,2'-bipyridyl)ruthenium(II) complex in water-ethylene glycol binary media.

The bimolecular photochemical quenching of the tris(2,2'-bipyridyl)ruthenium (II) complex by ferricyanide ions in water-ethylene glycol binary media was investigated using a spectrophotometric approach, as previously reported by our research group. Time-resolved spectroscopy revealed that dynamic photochemical quenching occurred via a diffusion-dominated pathway. The static quenching process was found to occur significantly when the concentration of ethylene glycol was greater than 40 wt%. The analysis of the Stern-Volmer plots revealed that the emitters and quenchers tended to show ionic associations in water-ethylene glycol compared to our previous results with a water-glycerol binary solvent system. This is attributed to hydrophobicity, which is consistent with pioneering works that report that the addition of ethylene glycol to pure water forms hydrophobic regions, leading to dehydration of the complex ions.

Electrochemical Selective Removal of Oxyanions in a Ferrocene-Doped Metal-Organic Framework.

Metal-organic frameworks (MOF) are a class of crystalline, porous materials possessing well-defined channels that have widespread applications across the sustainable landscape. Analogous to zeolites, these materials are well-suited for adsorption processes targeting environmental contaminants. Herein, a zirconium MOF, UiO-66, was functionalized with ferrocene for the selective removal of oxyanion contaminants, specifically NO3-, SO42-, and PO43-. Electrochemical oxidation of the embedded ferrocene pendants induces preferential adsorption of these oxyanions, even in the presence of Cl- in a 10-fold excess. Anion selectivity strongly favoring PO43- (Soxy/comp = 3.80) was observed following an adsorption trend of PO43- > SO42- > NO3- > (10-fold)Cl- in multi-ion solution mixtures. The underlying mechanisms responsible for ion selectivity were elucidated by performing ex situ X-ray photoelectron spectroscopy (XPS) on the heterogeneous electrode surface postadsorption and by calculating the electronic structure of various adsorption configurations. It was eventually shown that oxyanion selectivity stemmed from strong ion association with a positively charged pore interior due to the spatial distribution of charge by oxygen constituents. While ferrocenium provided the impetus for ion migration-diffusion, it was the formation of stable complexes with zirconium nodes that ultimately contributed to selective adsorption of oxyanions.

Ion Association and Hydration of Some Heavy-Metal Nitrate Salts in Aqueous Solution.

Aqueous solutions of four heavy-metal nitrate salts (AgNO3, TlNO3, Cd(NO3)2 and Pb(NO3)2) have been studied at 25 °C using broadband dielectric relaxation spectroscopy (DRS) at frequencies 0.27 ≤ ν/GHz ≤ 115 over the approximate concentration range 0.2 ≲ c/mol L-1 ≲ 2.0 (0.08 ≲ c/mol L-1 ≲ 0.4 for the less-soluble TlNO3). The spectra for AgNO3, TlNO3, and Pb(NO3)2 were best described by assuming the presence of three relaxation processes. These consisted of one solute-related Debye mode centered at ∼2 GHz and two higher-frequency solvent-related modes: one an intense Cole-Cole mode centered at ∼18 GHz and the other a small-amplitude Debye mode at ∼500 GHz. These modes can be assigned, respectively, to the rotational diffusion of contact ion pairs (CIPs), the cooperative relaxation of solvent water molecules, and its preceding fast H-bond flip. For Cd(NO3)2 solutions an additional solute-related Debye mode of small-amplitude, centered at ∼0.5 GHz, was required to adequately fit the spectra. This mode was consistent with the presence of small amounts of solvent-shared ion pairs. Detailed analysis of the solvent modes indicated that all the cations are strongly solvated with, at infinite dilution, effective total hydration numbers (Zt0 values) of irrotationally bound water molecules of ∼5 for both Ag+ and Tl+, ∼10 for Pb2+, and ∼20 for Cd2+. These results clearly indicate the presence of a partial second hydration shell for Pb2+(aq) and an almost complete second shell for Cd2+(aq). However, the hydration numbers decline considerably with increasing solute concentration due to ion-ion interactions. Association constants for the formation of contact ion pairs indicated weak complexation that varies in the order: Tl+ < Ag+ < Pb2+ < Cd2+, consistent with the charge/radius ratios of the cations and their Gibbs energies of hydration. Where comparisons were possible the present constants mostly agreed well with the rather uncertain literature values.

Stepwise extraction of Cu, Co, and Ni from hazardous waste: A novel process based on ammonia leaching and 2-((4-butylphenoxy)methyl)pyridine (BMPY) extraction system

The extraction of Cu, Co, and Ni from spent batteries and spent catalysts is crucial for resource recovery and environmental pollution reduction. Ammonia leaching offers a promising alternative in the hydrometallurgical treatment of these hazardous waste due to its selective leaching properties. However, the development of this method has been impeded by the lack of efficient extractants. In this work, an efficient extractant, 2-((4-butylphenoxy)methyl)pyridine (BMPY), was designed and synthetized. Utilizing the high affinity of BMPY for Cu, Co, and Ni and exploiting the different ionic association states of these metals at different pH levels, an effective process for separating Cu, Co, and Ni from ammonia leach solution was proposed, producing CuSO4, CoSO4, and NiSO4 with over 99.9 % purity. Mechanism investigations and pilot-scale experimental validation have demonstrated that the ammonia leaching-BMPY extraction process is a viable method for extracting Cu, Co, and Ni from hazardous waste, with significant potential for industrial application.

A green procedure for the determination of bioavailable forms of aluminum in natural waters by electrothermal atomic absorption spectroscopy combined with microextraction technique.

Aluminum is a prevalent element in nature, but bioavailable forms of aluminum are toxic to plants, animals, and humans. The present study is dedicated to the development of an ecologically friendly, fast, simple, reliable, sensitive, and accurate improved procedure for the determination of subtrace concentrations of bioavailable forms of aluminum in natural waters. The procedure includes the separation and pre-concentration of bioavailable forms of aluminum using vortex-assisted liquid-liquid microextraction (VALLME) of ionic associates with salicylaldehyde 4-picolinhydrazone (SAPH) and sodium dodecyl sulfate (DDSNa) by isoamylacetate (200μl) and direct electrothermal atomic absorption spectroscopy (ETAAS). The SAPH reagent interacts only with water-soluble forms of aluminum. SAPH is used for the pre-concentration of bioavailable forms of aluminum as well as a chemical modifier; it increases the absorbance and the precision of the analytical signal of aluminum. The calibration curve shows the linear dependence in the range of 0.05-86μg⋅L-1 of the aluminum concentration (R2 = 0.992), with the limit of detection at 0.015μg⋅L-1 and the limit of quantification at 0.05μg⋅L-1. The accuracy of the proposed procedure for bioavailable forms of aluminum determination was verified on model solutions and against a reference method on natural samples of river and lake waters (RSD 3.2-5.2%, recovery 97.1-103.4%).

Влияние цетиламина на спектры поглощения и протолитические свойства люмогаллиона и магнезона ХС

The interaction of monoazo compounds lumogallion (LG) and magnezon HS (MHS) with cetylamine (CA) in a wide pH range has been studied using a spectrophotometric method.It has been shown that the formation of ionic associates of CA under the interaction of its cation with sulfo group of azo compounds in the pH range 1–4 does not change the electronic absorption spectra of the azodyes. The interaction of CA at dissociated OH groups conjugated with the π-system of the azo compounds leads to a bathochromic shift in the maximum of the absorption spectrum of the corresponding ionic form of the reagents by 15 and 30 nm for the doubly and triply charged forms of LG, respectively, and by 50 nm for the doubly charged form of MHS. The shift in the maximum of the absorption spectrum is accompanied by the shift in the apparent pK value of the reagents by 2–4 pH units, caused by the binding of the dissociated form of the reagents. The reason for these changes in the absorption spectra and protolytic properties of both reagents is the formation of hydrophobically hydrated ionic associates of azo compounds with the cetylamine cation.

Adapalene as a chemical sensor for sensitive determination of manganese

ABSTRACT The work describes the use of 6-[3-(1-adamantyl)-4-methoxyphenyl]-2- naphthoic acid, or Adapalene (ADP) as a fluorescence tagging reagent, in a straightforward and very specific spectrofluorometric approach for the trace measurement of manganese (VII) in water. The process is based on the redox interaction of ADP with manganese (VII) in an acidic solution, which forms the complex [Mn (II)-ADP] and causes fluorescence at λex max/λem max = 323/400 nm. High-intensity fluorescence at 400 nm was seen in the fluorescence spectra of the formed complex ion association, Mn (II)-ADP, at pH 4. 1.55 µg mL−1 was the quantification limit, and 0.51 µg mL−1 was the detection limit and the correlation coefficient (R2) was 0.9863. 1.2173 L mol−1 was determined to be the Stern-Volmer. Spectrofluorometric technique is used to validate the approach in environmental water samples, yielding reasonable recovery percentages (89–93%). The current approach is advised to be used for reliable and accurate assessment of manganese (VII) in all wastewater and seawater samples, without the need for complex instrumentation and lengthy procedures.

Narrow Range of Coagulation of Ion Associates of Poly(styrene sulfonate) with Alcian Blue Dye.

The ionic association of Alcian Blue dye with poly(styrene sulfonate) in aqueous solutions was studied for analytical purposes. The quadruple-charged cationic dye, Alcian Blue, was found to form colloidal ionic associates with poly(styrene sulfonate) anions. When the amounts of opposite charges are nearly equal, the resulting ionic associates lose solubility and coagulate rapidly. This effect occurs within a narrow range of the ratio of poly(styrene sulfonate) to Alcian Blue. At the point of charge equivalence, the zeta potential of the resulting particles is zero, which facilitates flocculation. The resulting flocs enlarge to approximately 0.05-0.5 mm and precipitate rapidly. FTIR spectroscopy confirms that the precipitate contains both poly(styrene sulfonate) and Alcian Blue dye. Sedimentation kinetics was studied in detail using scanning turbidimetry. Due to the high molar absorbance of the Alcian Blue dye at 600 nm, the point of equimolar charge ratio was precisely determined by spectrophotometry. The complete precipitation of ionic associates occurs when the amount of poly(styrene sulfonate) ranges from 1.4 to 1.55 mmol per 1 g of Alcian Blue dye. Such a narrow coagulation range allows for the use of the studied effect for quantitative analysis. Both Alcian Blue dye and poly(styrene sulfonate) can be quantified if one of their concentrations is known.

Determination of Rhodamine 6G with direct immersion single-drop microextraction combined with an optical probe.

The combination of an optical probe and single-drop direct immersion microextraction (DI-SDME-OP) was used for the preconcentration and subsequent spectrophotometric determination of rhodamine 6G (Rh6G). The developed method is based on the formation of an ionic associate between Rh6G and picric acid at pH 3.0 and its extraction with amyl acetate. A microdrop of the organic phase was stably placed in the hole of an optical probe immersed in the sample solution. The absorbance of the extraction phase was monitored at 534 nm. The proposed method combines in a single step several stages of the analytical procedure, such as pre-concentration, phase separation, transfer of the extraction phase to the instrument and online measurement. The sensitivity of the proposed approach is not inferior to existing microextraction methods involving the combination of liquid-phase or solid-phase extraction with spectrophotometry or HPLC with a UV-Vis detector. The evaluation of the greenness of the developed method carried out by the AGREE method (0.58 points) showed that it outperforms other similar existing techniques using this parameter. The calibration plot for the determination of Rh6G by the DI-SDME-OP method was linear over the range of 10-500 nM with a correlation coefficient of 0.9956. The limit of detection was 3.4 nM. The accuracy and applicability of the method were evaluated by the determination of Rh6G in natural waters and lipstick.

Studies on interactions of L-glutamic acid with L-arabinose/D-xylose in aqueous medium: Ultrasonic velocity and acoustic parameter studies supported by FTIR spectroscopic investigation

Glutamic acid is a non-essential amino acid, meaning that the body can synthesize it on its own, and it doesn’t necessarily need to be obtained from the diet. Using an ultrasonic interferometer, the ultrasonic velocity at 293.15 K and 298.15 K and at experimental pressure P = 101 kPa were determined in order to evaluate and comprehend the synergy between non-essential amino acid and saccharides (L-arabinose/D-xylose) in an aqueous system. There is a direct correlation between the weak and strong molecular interactions that occur between the solution’s constituents and the propagation of ultrasonic sound waves through the experimental solutions. Using the ultrasonic velocity data, isentropic compressibility (Ks) apparent molar isentropic compressibility (Ks,ϕ) and isothermal compressibility (KT) were calculated. In addition to these characteristics, acoustic impedance (Z), internal pressure (πi), relative association (RA), molar free volume (Vf), molar free length (Lf) and surface tension (γ) were deduced and analysed to advocates potent ion- solvent interactions. In order to gain understanding of Glu-Glu and Glu- L-arabinose/D-xylose interactions in aqueous medium, these parameters were interpreted. Ion-solvent interactions are stronger than ion-ion interactions due to the greater and positive values of Ks0. Strong contacts occur between the polar segments of L-arabinose/D-xylose and the zwitterionic groups of Glu, and these interactions become stronger as the concentration of L-arabinose/D-xylose increases, as indicated by positive values of Ks,ϕ,tr0. The water structure is reformed during the solvation and ion association processes of Glu. Furthermore, the spectroscopic investigation has been conducted using the FTIR technique in order to verify the results obtained from acoustic studies. Predominant ion-hydrophilic/hydrophobic interactions prevail in the studied system is validated by FTIR study. Absorption band widening indicates that intermolecular hydrogen bonding predominates over intramolecular hydrogen bonding.

Electrokinetic properties of NaCl solution via molecular dynamics simulations with scaled-charge electrolytes.

Scaling ionic charges has become an alternative to polarizable force fields for representing indirect charge transfer effects in molecular simulations. In our work, we apply molecular dynamics simulations to investigate the properties of NaCl aqueous solutions in homogeneous and confined media. We compare classical integer- and scaled-charge force fields for the ions. In the bulk, we validate the force fields by computing equilibrium and transport properties and comparing them with experimental data. Integer-charge ions overestimate dielectric saturation and ionic association. Both force fields present an excess in ion-ion correlation, which leads to a deviation in the ionic conductivity at higher ionic strengths. Negatively charged quartz is used to simulate the confinement effect. Electrostatic interactions dominate counter-ion adsorption. Full-charge ions have stronger and more defined adsorption planes. We obtain the electroosmotic mobility of the solution by combining the shear plane location from non-equilibrium simulations with the ionic distribution from equilibrium simulations. From the Helmholtz-Smoluchowski equation, the zeta potential and the streaming potential coupling coefficient are computed. From an atomic-scale perspective, our molecular dynamics simulations corroborate the hypothesis of maximum packing of the Stern layer, which results in a stable and non-zero zeta potential at high salinity. The scaled-charge model representation of both properties is in excellent qualitative and quantitative agreement with experimental data. With our work, we demonstrate how useful and precise simple scaled-charge models for electrolytes can be to represent complex systems, such as the electrical double layer.

Paper based analytical devices for ions determination in nasal secretions demonstrating association with olfactory function

Nasal ions environment plays a crucial role in maintaining nasal physiology and supports olfactory transmission. Addressing the limited research on nasal ion levels and their association with olfactory function, paper-based sensors were developed for determination of sodium, potassium, calcium and chloride in the nasal mucus of healthy volunteers and patients with olfactory dysfunction. Multi-walled carbon nanotubes and carbon quantum dots from beetroot were incorporated into paper substrate where sensors were designed with ion association complexes for sodium, potassium, calcium and chloride enhancing the recognition sensing capabilities. The sensors composition was optimized, including ion-exchange materials and plasticizers, to enhance sensitivity and selectivity. The performance of the sensors is evaluated based on Nernstian slope, dynamic range, detection limit and response time. Selectivity of the sensors was tested and the results demonstrated high selectivity for the target ions. The sensors were successfully determined sodium, potassium, calcium and chloride levels in nasal mucus of healthy volunteers and patients with olfactory dysfunction. The results revealed elevated calcium levels in patients with olfactory dysfunction, highlighting associated diagnostic implications. This suggests that the proposed sensors could serve as a diagnostic tool for olfactory evaluation, particularly in resource-constrained settings where access to advanced diagnostic tools is limited.

Structure and Screening in Confined Electrolytes: The Role of Ion Association.

The effect of ionic association on the structure and property of confined electrolytes is investigated using the classical density functional theory. We find that ionic association strongly affects the ion distribution, surface force, and screening behavior of confined electrolytes. The decay length ξ, which can describe the screening effect of high-concentration electrolytes, satisfies a scaling relationship ξ/λD ∼ (σ/λD)n, with λD being the Debye length and σ representing the ion diameter. We find that n = 1.5 in the nonassociation model, which is contributed by the charge correlation, but n = 3 in the association model, which is contributed by the density correlation. The ion association changes the concentration-dependent characteristics of the screening length by promoting the shift of the decay behavior from the charge-dominated regime to the density-dominated regime. Our result reveals the importance of ion association for electrolyte structure and screening behaviors.

Ion association behaviors in the initial stage of calcium carbonate formation: An ab initio study

In this work, we performed static density functional theory calculations and ab initio metadynamics simulations to systematically investigate the association mechanisms and dynamic structures of four kinds of ion pairs that could be formed before the nucleation of CaCO3. For Ca2+–HCO3− and Ca2+–CO32− pairs, the arrangement of ligands around Ca2+ evolves between the six-coordinated octahedral structure and the seven-coordinated pentagonal bipyramidal structure. The formation of ion pairs follows an associative ligand substitution mechanism. Compared with HCO3−, CO32− exhibits a stronger affinity to Ca2+, leading to the formation of a more stable precursor phase in the prenucleation stage, which promotes the subsequent CaCO3 nucleation. In alkaline environments, excessive OH− ions decrease the coordination preference of Ca2+. In this case, the formation of Ca(OH)+–CO32− and Ca(OH)2–CO32− pairs favors the dissociative ligand substitution mechanism. The inhibiting effects of OH− ion on the CaCO3 association can be interpreted from two aspects, i.e., (1) OH− neutralizes positive charges on Ca2+, decreases the electrostatic interactions between Ca2+ and CO32−, and thus hinders the formation of the CaCO3 monomer, and (2) OH− decreases the capacity of Ca2+ for accommodating O, making it easier to separate Ca2+ and CO32− ions. Our findings on the ion association behaviors in the initial stage of CaCO3 formation not only help scientists evaluate the impact of ocean acidification on biomineralization but also provide theoretical support for the discovery and development of more effective approaches to manage undesirable scaling issues.

Investigation of ion association kinetics in Na2SO4-H2O by excess Raman spectroscopy and 2D correlation Raman spectroscopy

The ion association of salts aqueous solutions have long captivated the attention of researchers within the field of physical chemistry. In this paper, we have performed a comprehensive analysis of ion interactions in sodium sulfate (Na2SO4) aqueous solutions using a combination of high-resolution techniques, including excess (ERS) and two-dimensional correlation (2DCRS) Raman spectroscopy in conjunction with molecular dynamics (MD) calculations. The Raman spectrum shows that two inflection points in the Raman shift of the O–H vibration are observed with the increase in Na2SO4 concentration. Simultaneously, a new peak of the SO42- vibration appears at first inflection point, representing the formation of ion association. Further analysis based on ERS and 2CRS reveals that these two inflection points correspond respectively to the formation of ion pairs (CIPs) and small ion clusters. Importantly, MD simulations confirm the above experimental results. Our study provides evidence for ion association and clustering in aqueous in salt ion aqueous solutions.

High sensitivity determination of sweetener glycyrrhizic acid by triple-wavelength overlapping resonance Rayleigh scattering method and its analytical application

Under suitable acidic conditions, the triphenylmethane cationic dyes ethyl violet (EV) and crystal violet (CV) can form hydrogen-bonded cationic supramolecular aggregates with water molecules, respectively. Upon the addition of glycyrrhizic acid (GZA), these hydrogen-bonded cationic supramolecular aggregates undergo ionic association reactions with GZA, leading to the forming of new ion-associated hydrogen-bonded supramolecular aggregates. By optimizing the reaction conditions, two novel systems for the determination of GZA were developed using the triple-wavelength overlapping resonance Rayleigh scattering (TWO-RRS) technique. The enhancement observed in these systems was proportional to the concentration of GZA within a specific range. The linear ranges for these systems were 0.05–0.55 μg/mL, with limits of detection (LOD) at 0.016 μg/mL and 0.011 μg/mL, respectively. The standard addition method was employed to determine the content of GZA in actual samples. This study presents a new and valuable method for the determination of GZA, a sweetener.

Revisit the classical theories of the conductance of unassociated electrolytes. Is there reality in relaxation?

The experimental results of the ionic conductance of the electrolytic solution can be explained without the use of relaxation until almost 2M concentration of the NaCl solution within 97% agreement with two parameters: the hydrated ion radii for cations and anions. No other fitting parameters were introduced, and no ion association was assumed. The theory is based on a newly introduced electrochemical potential that incorporates the interaction between ions and fluctuations in electrolyte concentration in the nanosized region. It was found that the concept of local chemical potential, fluctuation in the nanosized area, and symmetry of the system are closely related to the Boltzmann distribution of ions. Extending the concept of a local chemical potential to the case of an external field, the derived ionic mobility automatically includes the effect of electrophoresis. The so-called electrophoretic retardation was found to be equivalent to the shielding effect of the external field. Relaxation bears a minor effect and may contribute to the ion transport of electrolytic solution at most 3%, if exists.

Wettability, imbibition and interdiffusion of lithium-based water-in-salt electrolytes in nanoporous carbon in relation to energy storage: A neutron radiography study

Superconcentrated lithium salt electrolytes, or lithium-based Water-in-Salt (WiS) electrolytes emerge as alternative electrolytes in supercapacitors and advanced batteries, such as the Li–O2 ones, especially when combined with a mesoporous carbon with very high surface area. In this work, we analyze the wettability, imbibition, and diffusivity of very concentrated lithium salts in a bimodal mesoporous carbon with pores of 5 nm and 25 nm in diameter. For the first time a neutron radiography technique is used to determine the imbibition and interdiffusion of lithium salts in mesoporous carbon. We found that a 20 m LiTFSI aqueous solution wets the surface of graphite and mesoporous carbon better than water. As a consequence, this WiS electrolyte is embedded rather fast in the mesoporous carbon by the action of capillary forces, exhibiting an intrinsic permeability K = (1.16 ± 0.03).10−18 m2. Finally, by resorting to the different cross-section of the 6Li and 7Li isotopes for the neutron capture, we could analyze the diffusion of LiCl in D2O confined in the mesoporous carbon. The interdiffusion coefficient of the confined LiCl is 5.0 10−7 cm2 s−1, corresponding to a tortuosity coefficient τ = 1.32. This moderate confinement effect results from the strong ion association of the LiCl that precludes the electrostatic interactions of Li+ ions with the negative charge on the pore walls. In summary, the combined properties of the lithium-based WiS electrolytes and the mesoporous carbon allow us to glimpse their use in supercapacitors and Li–O2 batteries.

Selective separation of lead (II) from foodstuffs and environmental samples by adsorption onto modified truffle peels with nanoparticles [TPs/TiO2(NP)] as a novel biomass

ABSTRACT This study aims to examined truffle peel powder modified with nanoparticles [TPs/TiO2(NP)] as a solid adsorbent for the removal of lead ions Pb(II) from environmental media and foodstuffs. The characterisation of TPs/TiO2(NP) was studied by a Fourier-transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and energy dispersive X-ray (EDX). Through the application of several adsorption isotherm models, the Langmuir at 25°C revealed to be most appropriate, having the highest R2 (0.961), and the maximum Pb(II) adsorption capacity was found 0.908 mg g−1. In addition, the various kinetics models were applied, and the data was well-fitted by the pseudo-second order kinetics model (R2 = 0.9997). Thermodynamic parameters indicated that the technique of adsorption had been endothermic (∆H = 30.79 J mol−1), The value of ΔG indicates the spontaneous and physical nature (- 29.26 KJ mol−1) and the positive value of ∆S indicates a moderate step of sorption of the Pb(II) complex ion associate (98.32 J). Foodstuffs (energy drinks and ice pops) and environmental samples (tap water) were successfully confirmed with a good recovery.

Determination of glycyrrhizic acid as sweeteners by dual-wavelength overlapping resonance Rayleigh scattering

This study used cationic dyes methyl violet (MV) and neutral red (NR) as probes, based on dual-wavelength overlapping resonance Rayleigh scattering (RRS), and designed two highly sensitive methods for the determination of the natural sweetener glycyrrhizic acid (GZA). In the Clark-Lubs buffer solution, when only MV or NR was present in the solution, they formed supramolecular polymers through hydrogen bonding. When adding GZA at different concentrations, the formation of ionic association complexes led to a subsequent decrease in RRS intensity at two wavelengths in the MV − GZA system and NR − GZA system, and the amount of the decline was proportional to the GZA concentration. The linear ranges were determined as 0.1 − 0.6 mg/L and 0.1 − 0.7 mg/L, with correlation coefficients of 0.9972 and 0.9996, and limits of detection were 0.052 mg/L and 0.016 mg/L, respectively. For this study, reaction conditions were optimized, potential interfering substances were investigated, and the mechanisms behind RRS generation and intensity decrease were discussed. The proposed methods were sensitive, fast, time-saving and efficient, and have been successfully applied to licorice and dried ginger decoction analysis, yielding satisfactory results.