Acetonitrile Solution Research Articles

A single 8-hydroxyquinoline-appended bile acid fluorescent probe obtained by click chemistry for solvent-dependent and distinguishable sensing of zinc(II) and cadmium(II).

Construction of fluorescent probes for zinc ion (Zn2+ ) and cadmium ion (Cd2+ ) is significant for the safety of humans. However, the discriminating recognition of Zn2+ and Cd2+ by a single probe remains challenging owing to their similar properties. Herein, a novel deoxycholic acid derivative containing 8-hydroxyquinoline fluorophore has been facilely synthesized through click chemistry to form a clamp-like probe. Using its perfect bonding cavity from 1,2,3-triazole and quinoline, this molecule showed favorable solvent-dependent fluorescent responses and distinguished Zn2+ and Cd2+ in different solvents. In ethanol aqueous solution, it displayed good selectivity and ratiometric fluorescence to Zn2+ with 30 nm spectroscopic red-shifts. In acetonitrile aqueous solution, it exhibited good selectivity and ratiometric fluorescence to Cd2+ with 18 nm spectroscopic red-shifts. Moreover, the unique microstructural features of the probe in assembly were used to reflect its recognition processes. Due to its merits of low detection limit and instant response time, the probe was utilized for sensing Zn2+ and Cd2+ in water, beer and urine with high accuracy. Meanwhile, this probe served as a handy tool and was employed to obtain inexpensive test strips for the prompt and semiqualitative analysis of Zn2+ and Cd2+ with the naked eye.

Photophysical Properties of Homo- and Hetero-Aggregate Assemblies Made of N-Annulated Perylene Derivatives.

We report the absorption spectra and photophysical properties of homo and hetero-aggregate assemblies of a strongly emissive N-annulated perylene dye (P) and of a dyad made of P and a methyl viologen derivative (P-MV), in ethanol-water solutions. In homo-aggregate assemblies of P, the π-π* fluorescence of the isolated chromophore is replaced by excimer emission at lower energy, with a lifetime of 900 ps, due to excimer formation from the initially prepared excitons. In homo-aggregate assemblies of P-MV, photoinduced charge separation, with formation of P+ -MV- species, occurs in 3 ps with a charge recombination of 20 ps. In hetero-aggregate P/P-MV systems, the light energy absorbed by the P components delocalizes over various P subunits, and when a P-MV unit is reached, charge separation occurs; however, excimer emission is present for P/P-MV ratio larger than 3 : 1, indicating that delocalized excitons within the hetero-aggregate systems extend over a limited number of P chromophores.

Bimetallic Eu/Tb Complexes for Ratiometric Temperature Sensing with Unusual Enhancement of Eu Luminescence with Temperature

In this paper we describe the results of the influence of temperature in the range of 280–340 K on the luminescence of bimetallic Eu/Tb complexes with N-heterocyclic ligand L based on 2,2′-bipyridyldicarboxylic acid in acetonitrile. The experiments were carried out for systems with various Eu/Tb ratios. The stability of the complexes of the ligand L with metal M (Eu or Tb) was determined using spectrophotometric titration in acetonitrile solutions. The LM complexes’ stability constants were found to be typical for these systems; however, the stability of Eu complex is slightly higher than that for Tb. Along with rising temperature, we observed a decrease in Tb emission intensity and, at the same time, an enhancement in Eu luminescence. An explanation of Eu luminescence enhancement involves the appearance of charge transfer states, bands of which can be observed in the Eu luminescence excitation spectra as difference spectra measured with two close temperatures. The unusual Eu luminescence enhancement upon heating was observed for the first time for the complex with tetradentate O,N-type heterocyclic diamide ligand L, while an inverse phenomenon was observed with the Tb luminescence. The Eu luminescence enhancement was found earlier for various carboxylate complex salts, but not for heterocyclic coordination complexes. This allows the construction of a ratiometric luminescent thermometer in the range of 280–340 K using the ratio of luminescence intensities for Eu and Tb. The stability constants for the individual Eu and Tb complexes help us to understand the equilibrium in L:Tb:Eu complex system and shed light on plausible speciation in solution.

Dual-Emissive Monoruthenium Complexes of N(CH3)-Bridged Ligand: Synthesis, Characterization, and Substituent Effect.

Three monoruthenium complexes 1(PF6)2-3(PF6)2 bearing an N(CH3)-bridged ligand have been synthesized and characterized. These complexes have a general formula of [Ru(bpy)2(L)](PF6)2, where L is a 2,5-di(N-methyl-N'-(pyrid-2-yl)amino)pyrazine (dapz) derivative with various substituents, and bpy is 2,2'-bipyridine. The photophysical and electrochemical properties of these compounds have been examined. The solid-state structure of complex 3(PF6)2 is studied by single-crystal X-ray analysis. These complexes show two well-separated emission bands centered at 451 and 646 nm (Δλmax = 195 nm) for 1(PF6)2, 465 and 627 nm (Δλmax = 162 nm) for 2(PF6)2, and 455 and 608 nm (Δλmax = 153 nm) for 3(PF6)2 in dilute acetonitrile solution, respectively. The emission maxima of the higher-energy emission bands of these complexes are similar, while the lower-energy emission bands are dependent on the electronic nature of substituents. These complexes display two consecutive redox couples owing to the stepwise oxidation of the N(CH3)-bridged ligand and ruthenium component. Moreover, these experimental observations are analyzed by computational investigation.

Development and Validation of an HPLC-DAD Method for the Simultaneous Analysis of Phenolic Compounds

Phenolic compounds are natural substances that exhibit different functional bioactivities and provide health-protective actions against chronic illnesses. The vast potential of these compounds in health and other sectors demands the establishment of analytical procedures for their immediate and simultaneous analysis. In this study, a high-performance liquid chromatography with diode-array detection (HPLC-DAD) method was developed and validated for the simultaneous analysis of gallic acid, catechin, epicatechin, rutin hydrate, caffeic acid, syringic acid, ellagic acid, p-coumaric acid, trans-ferulic acid, myricetin, resveratrol, and quercetin. The chromatographic separation of the selected polyphenols was carried out in a reversed-phase Inertsil ODS-3 column (250mm x 4.5mm x 5µm) at a flow rate of 0.8 mL/min, injection volume of 20 µL, and column temperature of 30°C. The detection and quantification of phenolic compounds were done at specific wavelengths (254, 275, 305, and 325 nm) using gradient elution for 40 minutes, with acidified water and acetonitrile solution as mobile phase. Validation of the established analytical procedure showed that the coefficient of determination (R2 > 0.99), limit of detection (0.01 to 0.35 µg/mL), limit of quantitation (0.03 to 1.07 µg/mL), recovery values (98.33 to 101.12%), and repeatability (RSD < 5%) respectively indicated a linear, sensitive, accurate, and precise analytical method for the simultaneous chromatographic analysis of the 12 phenolic compounds. Overall, the developed HPLC-DAD procedure can offer adequate confidence for the identification and quantification of specific polyphenols and can be modified or updated for future analysis of phenolic compounds in different plant extracts.

Synthesis of Aryl Carboxylic Acids through Ambient Electro-oxidation of Arylacetylenes

AbstractAn efficient and environment-friendly synthesis of aryl carboxylic acids through the ambient electro-oxidation of the arylacetylenes is demonstrated. The reaction proceeds smoothly at certain applied potentials in a mixed solution of acetonitrile and water with potassium peroxymonosulfate (Oxone) as the additive. The isolated yields of the desired products are good up to 90%, and the reaction exhibits excellent functional-group tolerance. In this electrochemical system, transition metal catalysts, extra acids/bases, and high temperature are not required. This method may open up a pathway for the synthesis of carboxylic acids by the electrochemistry strategy.

Wavelength dependent excited state dynamics observed in canonical pyrimidine nucleosides

Epidemiological evidence indicates that damage to DNA/RNA initialized by ultraviolet (UV) radiation is associated with skin cancer. Wavelength dependence of DNA photodamage was proposed as early as 1990s and demonstrated later on. Unraveling the photo-activated dynamics involved in related reactions is essential. However, studies aimed at uncovering the wavelength dependent excited state dynamics in canonical pyrimidine nucleosides have not received enough attention. In this work, excitation wavelength dependent excited state dynamics of 2′-deoxy-thymidine (dThd) and oxy-uridine (Urd) are investigated in acetonitrile solutions by femtosecond broadband transient absorption spectroscopy. Varying the excitation wavelength leads to a significant difference in the branching of the excited state population at the Franck-Condon (FC) region, resulting higher fluorescence quantum yield with 285 nm pump but higher triplet state quantum yield under 267 nm excitation. Based on our results, a vibronic coupling regulated excited state relaxation mechanism is proposed. This mechanism information is important for understanding the formation of harmful photoproducts for DNA/RNA with different wavelength UV excitations.

Polyoxometalate-based crown ether supramolecular hybrid electrocatalyst for the hydrogen evolution reaction and robust nitrite reduction

The novel crown ether–polyoxometalate assembly, [Na(H24C12O6)(CH3CN)(H2O)]2[Na(H24C12O6)(CH3CN)2][PW12O40] (PW12@Crown), based on Keggin-type phosphotungstic acid, was successfully synthesized in acetonitrile solution, and characterized by single-crystal/powder X-ray diffraction and a wide range of analytical methods, including FT-IR, Raman spectroscopies, thermogravimetric analysis. This POM-based supramolecular structure is the first example of a Keggin-type POM linked to three [18]-crown-6 ether components forming unique supramolecular host-guest structures by hydrogen bonding and other intermolecular forces. In addition, the hydrogen evolution reaction (HER) and the reduction of sodium nitrite (NaNO2) activity were studied by cyclic voltammetry to verify the catalytic performance of the compound.

Coordination and fragmentation chemistry of CyMe4-BTPhen complexes with lanthanides and actinides: A combined investigation by ESI-MS and DFT calculations.

To further understand the complexation and fragmentation during the extraction process, the formation of 2,9-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-12,4-benzotriazin-3-yl)-1,10-phenanthroline (CyMe4-BTPhen) complexes with lanthanides (Ln = La, Ce, Nd, Sm, Eu, Yb) and actinides (UO22+, Th4+) was observed by electrospray ionization mass spectrometry (ESI-MS) technique and density functional theory (DFT) calculations. Mass spectrometry titrations showed the variation relationship of different complexes in acetonitrile. For lanthanides, the major complexes were 1:2 species ([Ln(L)2]3+ and [Ln(L)2(NO3)]2+) with a ratio of 1:2, which were observed at the initial addition of Ln3+, whereas the species ([Ln(L)(NO3)2]+) with a ratio of 1:1 was detected when the [Ln]/[L] concentration ratio reached 1.0. For UO22+ and Th4+ complexes, 1:1 or 1:2 species ([UO2L(NO3)]+, Th(L)2(NO3)3+ and Th(L)2(NO3)22+) were formed. The fragmentation chemistry of both the ligand and the complex cations was characterized in detail by collision-induced dissociation. The fragmentation process of CyMe4-BTPhen was unfolded sequentially on both sides of the ligand by cleavage of C-C and C-N bonds. DFT calculations provided a detailed analysis of the structures and thermodynamics of those complexes, which indicated that the stable complexes formed in acetonitrile solution were consistent with the ESI-MS results.

CO2 electroreduction in aqueous and acetonitrile solutions on porous cathode fabricated by anode dezincification of CuZn

The rates of the CO2 electrochemical reduction were determined on porous cathodes formed by electrochemical dealloying of CuZn under different regimes of selective anodic dezincification of brass. It was established that the formation of a porous surface proceeds in two following stages: 1) the dissolution of Zn from the CuZn mainly along the grain boundaries with the formation of submicron crevices between them, and 2) electrochemical dezincification of brass grains and formation of nanopores. The zinc content in the nanoporous copper surface is less than 1%. It was proved that anodically dezincified brass porous cathodes demonstrate a significantly higher CO2 reduction current on their surface than smooth copper and brass surfaces. For instance, in aqueous solutions, at an electrode potential of –1.5 V, the value of cathode current density on porous Cu cathodes is between 5 to 9 mAcm–2, while it is only 2.5 and 1.5 mAcm–2 on smooth Cu and CuZn cathodes, respectively. A similar trend is observed in an acetonitrile environment, where the current density of the CO2 electroreduction at the electrode potential of –3.0 V is 22 to 27 mAcm–2, 15 mAcm–2, and 18 mAcm–2 on porous cathodes, Cu cathode, and CuZn cathode, respectively. As the pore size decreases from submicron to submicron-nanosized, there is a tendency for an increase in cathodic currents by approximately 80% and 25% in aqueous and in acetonitrile solutions, respectively. Additionally, CO2 recovery on porous cathodes remains stable during long-term electrolysis at an electrode potential below –1.5 V.

Simple and efficient UPLC-ESI-MS/MS method for multi-residue analysis of 14 coccidiostatic agents in poultry liver and muscle tissues

Simple, rapid, efficient and cost-effective UPLC-ESI-MS/MS confirmatory method for the simultaneous determination of 14 coccidiostatic agents (salinomycin, monensin, lasalocid, halofuginone, robenidine, nicarbazin as 4,4′-dinitrocarbanilide, narasin, maduramycin, decoquinate, diclazuril, semduramycin, clopidol, amprolium and toltrazuril as parent drug and as its metabolites toltrazuril sulfone and toltrazuril sulfoxide) in chicken and turkey meat and liver was developed, validated and approved in routine laboratory practice. Main steps of sample preparation are as follows: homogenization, ultrasonication with acetonitrile and buffer solution, centrifugation, extraction by organic solvents mixture containing ethyl acetate and dichloromethane, evaporation and defatting of reconstituted residue by hexane. The technique is capable for multi-analyte determination of coccidiostats with LODs of 1–3 μg kg−1 depending on analyte using matrix-fortified calibrations. Procedure's adequacy was evaluated according to Commission Implementing Regulation (EU) 2021/808. Proposed method's efficiency is provided by the rational selection of extractants and ultracentrifugation at last stage of sample preparation. The developed technique is suitable to be used, when applying external standards and internal standards approaches. Time-consuming and costly procedures with ion suppressive desalting agents or SPE purification, which are common for coccidiostats assay, are not involved in the elaborated method, being method's main benefit comparing with known multi-residue LC-MS/MS techniques for coccidiostats analysis. This method is suitable for the control of safety parameters of poultry meat and liver as well as for establishing withdrawal periods of veterinary drugs based on coccidiostatic agents.

Fluorination of vanadates with organic fluorinating agents

The organic fluorinating agents [bis(2-methoxyethyl)amino]sulfur trifluoride (Deoxo-fluor®), diethylaminosulfur trifluoride (DAST), and N-fluorobenzenesulfonimide (NFSI) were used to inspect the efficiency of fluorination of monovanadate, HxVO4(3−x)− (V1), and decavanadate, HxV10O28(6−x)− (V10), in solution by 51V NMR spectroscopy. It was observed that either VOF4− or VO2F2− can be generated in acetonitrile solutions at room temperature after one hour selectively for HxVO4(3−x)−, while HxV10O28(6−x)− is more sensitive towards reduction and only NFSI can be used to generate VOF4−. The differences in reactivity can be attributed to the electrophilicity of fluorine in Deoxo-fluor® and DAST, and its nucleophilicity in NFSI. Tetrabutylammonium fluoride, triethylamine trifluoride, and hydrogen fluoride–pyridine adduct were also used under the same conditions for comparison of the efficiency and selectivity of fluorination. It was observed that only HF.pyridine provided a complete transformation of V1 and V10 into VOF4−. The pilot experiments introduced in this work are the first example of fluorination of polyoxometalates with organic fluorination agents and other less commonly used fluorides with organic cations and show their great potential in the synthesis of polyoxometalates with fluorido ligand.

Manganese(I) Diamine Electrocatalysts: Electrochemical Carbon Dioxide Reduction to Carbon Monoxide

Novel organometallic complexes Mn(benzene-1,2-diamine)(CO)3Br, Mn-1, Mn(3-methylbenzene-1,2-diamine)(CO)3Br, Mn-2, and Re(benzene-1,2-diamine)(CO)3Cl, Re-1, have been synthesized and characterized by IR, UV/Vis, 1H-NMR, EA and HRMS. The structures of Mn-2 and Re-1 were confirmed by X-ray crystallography. The three novel compounds were studied for their electrocatalytic reduction of carbon dioxide to carbon monoxide using cyclic voltammetry in acetonitrile solutions. Controlled potential electrolysis was used to obtain information on faradaic yield, with product formation being confirmed by GC. Using earth-abundant manganese, compounds Mn-1 and Mn-2 display turnover frequencies of 108 s−1 and 82 s−1, respectively, amid selective production of carbon monoxide (faradaic yields ~85%), with minimal co-production of dihydrogen (<2%), and low overpotential of 0.18 V. The rhenium congener, Re-1, displays no activity as an electrocatalyst for carbon dioxide reduction under identical conditions.

Enhancing protein trapping efficiency of graphene oxide-polybutylene succinate nanofiber membrane via molecular imprinting

Filtration of biological liquids has been widely employed in biological, medical, and environmental investigations due to its convenience; many could be performed without energy and on-site, particularly protein separation. However, most available membranes are universal protein absorption or sub-fractionation due to molecule sizes or properties. SPMA, or syringe-push membrane absorption, is a quick and easy way to prepare biofluids for protein evaluation. The idea of initiating SPMA was to filter proteins from human urine for subsequent proteomic analysis. In our previous study, we developed nanofiber membranes made from polybutylene succinate (PBS) composed of graphene oxide (GO) for SPMA. In this study, we combined molecular imprinting with our developed PBS fiber membranes mixed with graphene oxide to improve protein capture selectivity in a lock-and-key fashion and thereby increase the efficacy of protein capture. As a model, we selected albumin from human serum (ABH), a clinically significant urine biomarker, for proteomic application. The nanofibrous membrane was generated utilizing the electrospinning technique with PBS/GO composite. The PBS/GO solution mixed with ABH was injected from a syringe and transformed into nanofibers by an electric voltage, which led the fibers to a rotating collector spinning for fiber collection. The imprinting process was carried out by removing the albumin protein template from the membrane through immersion of the membrane in a 60% acetonitrile solution for 4 h to generate a molecular imprint on the membrane. Protein trapping ability, high surface area, the potential for producing affinity with proteins, and molecular-level memory were all evaluated using the fabricated membrane morphology, protein binding capacity, and quantitative protein measurement. This study revealed that GO is a controlling factor, increasing electrical conductivity and reducing fiber sizes and membrane pore areas in PBS-GO-composites. On the other hand, the molecular imprinting did not influence membrane shape, nanofiber size, or density. Human albumin imprinted membrane could increase the PBS-GO membrane’s ABH binding capacity from 50 to 83%. It can be indicated that applying the imprinting technique in combination with the graphene oxide composite technique resulted in enhanced ABH binding capabilities than using either technique individually in membrane fabrication. The suitable protein elution solution is at 60% acetonitrile with an immersion time of 4 h. Our approach has resulted in the possibility of improving filter membranes for protein enrichment and storage in a variety of biological fluids.

Role of non-covalent interactions in 2,5-di-Me-pyrazine-di-N-oxide - tertiary butyl alcohol - single-walled and multi-walled carbon nanotubes electrocatalytic systems

Oxidation of tert-butyl alcohol (tert-BuOH, Me3COH), a compound with a high C-H bond breaking energy in the absence of precious metals or their oxides as catalysts and using metal-free electrodes, is an inexpensive process and is of interest for practical applications in electrocatalysis and sensors. In this work, electrocatalytic systems 2,5-di-Me-pyrazine-di-N-oxide (Pyr1) - tert-BuOH – single - walled (SWCNT) and multi-walled (MWCNT) carbon nanotube paper electrodes in 0.1 M Bu4NClO4 solution in acetonitrile (MeCN) were studied by the methods of cyclic voltammetry, quantum chemical modeling and electron paramagnetic resonance (EPR) electrolysis. Calculaition of energies of non-covalent interactions between the components of the electrocatalytic system in complexes Me3COH*Me3COH, Me3COH*MeCN, Pyr1*Me3COH and the adsorption energy of Me3COH and complexes of Pyr1*Bu4NClO4, Pyr1*Me3COH, Pyr1*MeCN and Me3COH *Bu4NClO4 on CNTs surface using a cluster model describing the surface of conducting carbon nanotubes (10, 10) was performed. The study made it possible to reveal the regularities characteristic of aromatic-di-N-oxide – CNT electrocatalytic systems and to propose a mechanism of tert-BuOH oxidation in the presence of electrochemically generated radical cation Pyr1. The data will be useful at using CNT electrodes in electrocatalytic processes, as well as aromatic di-N-oxide-CNT catalytic systems in electrocatalysis and sensors.

Analysis of authorized coccidiostats in chicken feces and environmental water by ultra-performance liquid chromatography-tandem mass spectrometry based on dispersive solid-phase extraction and lyophilization

A simple, sensitive, and efficient method based on ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was developed for the determination of 8 coccidiostats in chicken feces and environmental water (including sewage, pond water, and lake water) surrounding the farm. Target analytes in chicken feces were extracted with 2% acetic acid in acetonitrile solution, followed by a dispersive solid-phase extraction (DSPE) cleanup step using the mixture of PSA and C18 adsorbents. Environmental water samples were pretreated using a lyophilization approach. Analysis was carried out on a UPLC-MS/MS with the combination of methanol and 0.1% formic acid aqueous solution as the mobile phase under multiple reaction monitoring in positive and negative ionization modes. Results showed that 8 coccidiostats were linear with correlation coefficients higher than 0.99. Method validation was performed using fortified samples, reaching satisfactory recoveries of 75.9%–97.8% in chicken feces and 71.9%–108.2% in environmental water. Limits of detection for 8 analytes in chicken feces and environmental water were 0.03∼2 µg/kg and 0.005∼1 µg/L, respectively. Matrix effects were calculated and strong signal suppression (>50%) for some coccidiostats was observed. The developed method was successfully applied to analyze coccidiostats in chicken feces and environmental water collected from local chicken farms.

Investigation into the Nucleation of the p-Hydroxybenzoic Acid:Glutaric Acid 1:1 Cocrystal from Stoichiometric and Non-Stoichiometric Solutions.

The nucleation in the p-hydroxybenzoic acid:glutaric acid 1:1 cocrystal (PHBA:GLU) system has been investigated in stoichiometric and non-stoichiometric acetonitrile solutions by induction time experiments. Utilizing the ternary phase diagram, the supersaturated non-stoichiometric solutions were created with compositions along the invariant point boundary lines. In all cases, the PHBA:GLU cocrystal was the nucleating phase, even though the non-stoichiometric solutions were also supersaturated with respect to the pure solid phases. The nucleation of the cocrystal from the mixed solutions is found to be more difficult than the nucleation of the pure compounds from the respective pure solutions, as captured by lower pre-exponential factors (A). However, if the driving force is defined per reactant molecule instead of per heterodimer, the cocrystal nucleation difficulty is close to that of the more difficult-to-nucleate pure compound. The difference in nucleation difficulty of the cocrystal from stoichiometric and non-stoichiometric solutions was captured by differences in the interfacial energy, while the pre-exponential factor remained unchanged. Apart from the pure GLU system, the relation between the experimentally determined pre-exponential factors for the different systems correlates with calculated values using theoretical expressions for volume-diffusion and surface-integration control.

New Ruthenium Nitrosyl Complexes Combining Potentially Photoactive Nitrosyl Group with the Magnetic Nitroxide Radicals as Ligands.

Two ruthenium nitrosyl complexes of Na[RuNOCl4L] with nitronyl nitroxide radicals coordinated to ruthenium with N-donor pyridine rings were prepared and described. The crystal structure of both complexes is 1D or 2D polymeric, due to the additional coordination of sodium cation by bridging the chloride ligands or oxygen atoms of nitroxides. Partially, the oligomeric forms remain in the solutions of the complexes in acetonitrile. The magnetic measurements in the solid state demonstrate the presence of antiferromagnetic interactions through the exchange channels, with the distance between paramagnetic centers equal to 3.1-3.9 Å. The electrochemical behavior of the prepared complexes was investigated in acetonitrile solutions.

Au13 Superatom Bearing Two Terpyridines at Coaxial Positions: Photoluminescence Quenching via Complexation with 3d Metal Ions

Abstract A gold cluster [Au13(dppe)5(EPTpy)2]3+ (dppe = 1,2-bis(diphenylphosphino)ethane, EPTpy-H = 4′-(4-ethynylphenyl)-2,2′:6′,2′′-terpyridine) was synthesized by ligand exchange reaction of [Au13(dppe)5Cl2]3+. Single-crystal X-ray diffraction analysis revealed that two terpyridyl moieties were σ-bonded to the coaxial positions of the icosahedral Au13 core. These two terpyridyl moieties were coordinated with 3d metal ions M2+ (M = Co, Ni, Cu, Zn) in acetonitrile solution under ambient conditions. The photoluminescence (PL) of [Au13(dppe)5(EPTpy)2]3+ with a quantum yield of 0.17 at ∼780 nm was almost completely quenched by coordination with Co2+, Ni2+, and Cu2+, while the PL was not affected by Zn2+ coordination. The metal-dependent PL quenching behavior is ascribed to the difference in the electronic structure of the metal ions. The energy transfer from the Au13 chromophore to the coordinated Co2+, Ni2+, or Cu2+ with an open electronic structure proceeds efficiently via an electron exchange mechanism, while the process is prohibited for Zn2+ with a closed electronic structure.

Simultaneous Determination of Five Iridoids of Picrorhiza scrophulariiflora in Rat Plasma Using UHPLC-ESI-MS/MS.

In this study, we developed an ultra-performance liquid chromatography-electrospray tandem quadrupole mass spectrometry (UHPLC-ESI-MS/MS) method to simultaneously determine Picroside-I, Picroside-II, Picroside-III, minecoside, and sweroside in rat plasma. The chromatographic column was an ACQUITY UHPLC® BEH Amide Column (2.1 × 100 mm, 1.7 µm; Waters, MA, USA), column temperature 40 °C. The mobile phase was 0.1% formic acid aqueous solution-0.1% formic acid acetonitrile solution. The flow rate was 0.4 mL/min. Multiple reaction monitoring (MRM) and negative ion modes were adopted. The results showed that the calibration curves of five compounds in plasma showed good linearity (r > 0.9911) over the studied dose range. The lower limits of quantification (LLOQ) for Picroside-I, Picroside-II, Picroside-III, minecoside, and sweroside were 6.876, 5.193, 5.040, 1.260, and 4.527 ng/mL, respectively. The intra-day and inter-day precision were <15%. The matrix effects ranged from 95.77 to 101.9%. The Tmax were 1.1 ± 0.2, 1.1 ± 0.1, 0.8 ± 0.1, 1.0 ± 0.2, and 2.1 ± 0.1 h. This study will be useful in understanding the behavior of drugs in the body and the body's effect on drugs. It also offers theoretical underpinnings and highlights the importance of clinical applications and creating novel drugs.