67 results about "Ion binding" patented technology

There is provided a fluorinase variant thereof having at least 70% sequence identity to a sequence MSDLGX6TDDSVAQCKGLMLSICPX24VX26IX28DX30CHX33MTPX37DVVEGARYIVDLPR X52FPEGTVFATTTYPATGTX70X71RSVAX76RX78KX80AALGGARGQX90AGSGX95GX97E RAEGX103YIYIAPNNGLLTX116VIEEHGYX124EAYEVSX131TX133VIPX137X138PEPTFYSR EMVAIPSAHLAAGFPLX163X164VGRX168LX170DX172EIVRFEX179X180KX182X183X184VX186G X188X189LX191GX193X194X195X196X197DHPFGNX204WTNX208HRTDLEKAGIX219YX221TX223X 224KX226VX228DGVLX233FX235LPLX239PTFADAX246X247X248GX250PVX253YX255NSRGYLX2 62X263ARNAAX269LAYPYNLX277AGX280SVX283VTX286A (SEQ ID NO: 1), wherein X is a natural amino acid, and wherein the variant comprises one or more mutations at a site selected from the group consisting of an ion-egress site, a S-Adenosyl-L-Methionine (SAM) binding site, an ion-binding site (IBS), and a conserved site. Also disclosed are polynucleotides encoding the variants, vectors comprising the polynucleotides encoding the variants, and host cells comprising the vectors thereof. Also disclosed are Methods for producing the variants, methods of catalyzing the fluorination of a compound, uses of the fluorinase variants, and methods of treatment using the fluorinase variants thereof.

The invention provides a protein and metal ion binding site identification method, device and equipment, and belongs to the field of protein detection.The method comprises the steps that feature extraction is conducted on known metal ion binding protein, and multiple sample evolution information features are obtained; the method comprises the following steps: for an unknown protein sequence, determining candidate distant homologous metal ion binding proteins through multi-sequence comparison and cosine similarity screening, and further constructing a training set; a composite framework in which a bidirectional long-short-term memory network and a full-connection neural network are connected in series is adopted, input features comprise evolutionary information features and physicochemical attribute features, and probability values of binding sites of different metal ions are output; training the composite framework through the training set to obtain a site prediction model; and predicting a binding site of an unknown protein sequence by using the prediction model. The stable and efficient prediction on the metal ion binding site is realized.

The invention concerns a medical device comprising a coating, said coating comprising: polymer Z bonded to the medical device and moieties of Formula (A), wherein X is an amino group which is covalently bonded to Z or which can ionically bind to free carboxyl groups, wherein the moieties according to Formula A are present in the coating at an amount of 05-30 nmol / cm2; and wherein polymer Z comprises free carboxyl groups in an amount of 1-30 μmol / cm2.

The present invention relates to a fast-response bistable electrochromic device, which comprises a transparent electrode layer, an electrochromic layer with a relatively low lithium-ion binding energy, an electrochromic layer with a relatively high lithium-ion binding energy, an ion conduction layer and a top electrode layer arranged in sequence; and a first fast ion conductor layer and a second fast ion conductor layer are respectively arranged on the upper and lower surfaces of the electrochromic layer with a relatively high lithium-ion binding energy; preferably, the first fast ion conductor layer and the second fast ion conductor layer are selected from at least one of LLZO, LLTO and LIPON.

The present disclosure relates to a brine purification device, its purification method and uses thereof. It is disclosed a brine purification device comprising a housing with an inlet configured to receive untreated brine and an outlet configured to discharge purified brine from a purification chamber; wherein the purification chamber within said housing is configured to have two separated hemispheres; wherein the at least one plate comprises a first engraved serpentine flow channel in a first side configured for the flowing of brine and a second engraved serpentine flow channel in the opposite side of the same plate configured for the flowing of a flowing fluid; wherein the two sides of the at least one plate are separated by an anion-exchange membrane in such a way that the untreated brine combine with counter-ions from the flowing fluid through said anion-exchange membrane; wherein the at least one plate is configured for a fluid velocity of 0.007 to 0.015 m / s considering a thickness of 3 to 6 mm.

The application provides a preparation device and method of nanoscale superfine powder, and relates to the technical field of calcium particle preparation, and comprises a solid-gas mixing cylinder, a positive voltage cylinder, a negative voltage cylinder and a positive-negative ion impact tube; the solid-gas mixing cylinder is provided with a feeding port for inputting animal skeleton coarse particles and oxygen to form a solid-gas mixed gas flow; the solid-gas mixing cylinder is communicated with the positive voltage cylinder and the negative voltage cylinder; the positive voltage cylinder ionizes the oxygen in the solid-gas mixed gas flow into a positive ion state, and the negative voltage cylinder ionizes the oxygen in the solid-gas mixed gas flow into a negative ion state; the outlet of the positive voltage cylinder is communicated with the outlet of the negative voltage cylinder, the solid-gas mixed gas flow with the positive ion state and the solid-gas mixed gas flow with the negative ion state are combined at the outlet and enter the positive-negative ion impact tube, the solid-gas mixed gas flow with the positive ion state and the solid-gas mixed gas flow with the negative ion state in the positive-negative ion impact tube are strongly impacted, and a large amount of energy released when the positive ion and the negative ion combine crushes the animal skeleton coarse particles into superfine powder.

The invention discloses a genetically engineered cell capable of reducing binding of metal ions and application, and particularly provides the genetically engineered cell, expression or activity of at least one gene of related genes synthesized by Pulveriminic Acid of the cell is reduced, binding to the metal ions is reduced, and the cell can be used for synthesizing the metal ions. Therefore, the condition that the fermentation liquor becomes red due to generation of red substances due to combination of metal ions in the culture process, such as reduction of combination of Fe < 3 + >, is effectively solved, and the problem of separation and purification caused by the red fermentation liquor is further reduced or even eliminated; the improvement can also effectively solve the problem that the IVTT activity value of existing K.lactis in amplified production is insufficient, subsequent production is further facilitated, and the K.lactis has very remarkable application value.

An oral appliance configured for temporary use in a patient's mouth. The oral appliance has an oral appliance body formed from an ionic polyurethane-based resin, which is a reaction product of ingredients including a diisocyanate, a diol chain extender, a polyglycol, and an ionically charged modifier. An ionic active agent is ionically bound to the ionically charged modifier. This may be done by solution imbibing technique or bulk mixing (e.g., thermal compounding or solvent mixing) technique. The ionic active agent may include fluoride ions. The ionic active agent may include an antimicrobial agent. The ionic active agent may include one or more essential oils.

Perovskite solar cells are provided that comprise a hole transport layer; an electron transport layer; and a perovskite layer between the hole transport layer and the electron transport layer, the perovskite layer comprising a perovskite and perovskite binding ligands, wherein the perovskite binding ligands each comprise an aryl group, a first perovskite binding group bound to the aryl group and bound to a first uncoordinated ion of the perovskite, a second perovskite binding group bound to the aryl group and bound to a second uncoordinated ion of the perovskite, wherein the perovskite binding ligands have a planar orientation relative to a surface of the perovskite between the first and second uncoordinated ions.

The present invention relates to a supramolecular peptide complex comprising several peptide oligomerisation domains capable of forming multivalent complexes, bonded to at least one antigen-binding molecule and to at least one chelating group binding at least one metal cation of a heavy metal (M) having an oxidation state (M2+, M3+, M4+).

Disclosed herein are assays, methods, and devices for detecting a target ion via ionophore-based ion-selective sensing using Surface Enhanced Raman Spectroscopy (SERS). For example, disclosed herein are assays for detection of a target ion via SERS, the assays comprising: an ionophore, a nanostructured metal, an ion exchanger, and an indicator, wherein the ionophore comprises a binding portion configured to bind with the target ion, wherein the nanostructured metal is configured to enhance a Raman signal of at least a portion of the indicator, wherein the Raman signal changes when the target ion is bound to the ionophore. Also disclosed herein are methods, for example, comprising contacting any of the assays described herein with a liquid sample; subsequently collecting a surface enhanced Raman signal from the liquid sample and the assay; and processing the surface enhanced Raman signal to determine a property of the liquid sample.

The application provides a mass spectrometry detection device and method for active protein-small molecule interaction, which uses a mass spectrometry sensor to obtain tandem mass spectrometry data of non-covalent complexes of active protein incubated with small molecule compounds at different concentration points; performs non-linear curve fitting on the concentration sequence of the small molecule compounds based on the ion combination rate of the protein binding small molecules at each concentration point, to obtain an apparent dissociation constant of the active protein-small molecule interaction; determines a local conformation change parameter of the active protein induced by small molecule binding and a potential binding domain of the small molecule; and performs fusion evaluation on the binding strength and conformation influence degree of the protein-small molecule interaction based on the apparent dissociation constant, the local conformation change parameter and the potential binding domain, to output a stability grade of the protein-small molecule interaction. Based on the above scheme, non-denatured state mass spectrometry detection of protein-small molecule complexes in a liquid phase environment can be realized.

The invention discloses an engineering bacterium VB27701 capable of adsorbing copper ions as well as a preparation method and application of the engineering bacterium VB27701. The engineering bacterium VB27701 takes Escherichia coli Nissle 1917 as a chassis cell, and comprises a first recombinant covert plasmid and a second recombinant covert plasmid which are used for expressing and displaying the copper ion binding protein CueR on the surface. The engineering bacterium VB27701 constructed by the invention can specifically adsorb copper ions in intestinal tracts, reduces copper circulating in vivo from the source, can be applied to preparation of preparations for adsorbing copper ions in the intestinal tracts of mammals, and can also be applied to preparation of drugs for treating hepatolenticular degeneration.

The invention provides an SBA-16-DC-UiO-66 composite material as well as a preparation method and application thereof, and belongs to the technical field of transfer hydrogenation reaction catalyst materials. According to the invention, 3-(triethoxy silyl) propyl succinic anhydride is used as a carboxyl functional reagent and is subjected to co-condensation with tetraethoxysilane to prepare the double-carboxyl functional mesoporous silica SBA-16-DC with adjustable aperture, high specific surface area and excellent hydrothermal stability, metal ion binding sites of the carrier are increased, and the mesoporous silica SBA-16-DC has the advantages of high specific surface area, high specific surface area and excellent hydrothermal stability. Steric hindrance is provided for UiO-66 growth to inhibit agglomeration, the mass transfer efficiency can be enhanced through a mesoporous confinement effect, and the efficiency of catalyzing a furfural transfer hydrogenation reaction and the yield of a catalytic product are remarkably improved; carboxyl on the surface of SBA-16-DC can effectively adsorb Zr < 4 + >, the dispersion uniformity and stability of the active component UiO-66 in the carrier are improved, the problems of agglomeration and loss are avoided, and the catalytic performance and stability of the composite material are remarkably improved.

The present invention belongs to the technical field of active peptide preparation, and specifically relates to an angiotensin I converting enzyme inhibitory peptide and its application. The present invention uses Yinghong No. 9 black tea residue as raw material, and utilizes enzymatic hydrolysis, ultrafiltration, high performance liquid chromatography separation and purification, mass spectrometry, etc. to screen out angiotensin I converting enzyme inhibitory peptides from 59 peptide segments. The molecular docking results show that the inhibitory peptide can bind to multiple amino acid residues in the S1, S2 and S1′ active pockets of ACE, and it is mainly hydrogen bonds, metal ion binding and hydrophobic interactions that play the most important role in stabilizing the docking complex and inhibiting ACE activity. In addition, the EA.hy926 cell model was used to find that the inhibitory peptide can play an active role by promoting the release of NO and inhibiting the secretion of ET‑1. The inhibitory peptide is expected to be used as a potential antihypertensive drug or functional food ingredient.

The present invention belongs to the technical field of gas reservoir exploitation, and discloses a multi-functional acid system for reducing the fracture pressure of muddy reservoirs and a preparation method thereof. The mass percentage of each component in the multi-functional acid system is: hydrochloric acid 5-10.0%, hydrofluoric acid 5%, multi-functional acid 1.0-3.0%, corrosion inhibitor 3.0-5.0%, acidizing agent 0.5-1.0%, stabilizer 1.0-2.0%, and the balance is water. The multi-functional acid of the present invention has efficient and specific recognition of metal cations such as silicon ions, magnesium ions, and calcium ions produced during the acidification process of muddy reservoirs by using a tetrapod polycarboxylic acid skeleton; by introducing an amide group, the multi-functional acid is made more capable of binding to metal cations; by introducing a long-chain alkyl hydrophobic group, the cations can be more tightly wrapped to avoid the cations from contacting hydroxide to produce metal hydroxide precipitation and causing reservoir damage; the multi-functional acid system of the present invention can reduce the fracture pressure of the reservoir during fracturing construction.

The invention discloses modified polyethyleneimine (TPEI) and a preparation method and application thereof.Thioglycollic acid modified polyethyleneimine (TPEI) can be specifically chelated with Pd (II) in a low-pH and high-salinity complex water sample, so that the problem that an existing polyelectrolyte material (PEI) is poor in metal ion binding capacity in low-pH and high-salinity water is solved; according to the method, high-selectivity removal of Pd (II) in low-pH and high-salinity industrial wastewater or palladium-containing complex water is achieved through the polyelectrolyte material of a specific structure and the polyelectrolyte material and Pd (II) in a specific molar ratio, and the removal rate can still reach 90% or above under the condition that the pH value is 1; by means of the method, industrial wastewater can be treated with low cost, Pd (II) in the wastewater can be removed, the wastewater discharge standard is met, selective trapping and recycling of Pd (II) can be achieved, and the recycling rate can reach 91.5%.

The present invention discloses a hole transport material, a preparation method thereof, and a perovskite solar cell, wherein the hole transport material comprises a phenanthroline metal complex as shown in Formula 1: M is a divalent metal ion; X is a halogen ion. The phenanthroline metal complex of the present invention has excellent semiconductor properties; and its physical, electronic, and optical properties can be regulated by changing the divalent metal element therein; in particular, the halogen ions contained in the phenanthroline metal complex can react with the Pb that is not fully coordinated on the surface of the perovskite light-absorbing layer. 2+ Ionic bonding has an interface passivation effect, reducing the ineffective loss of carriers, thereby effectively improving the device stability and service life of the solar cell; in addition, the o-phenanthroline metal complex shown in Formula 1 is easy to obtain and low in cost.

The preparation method comprises the following steps that S1, a calcium source and an erbium source are dissolved in deionized water, and a solution A containing the calcium ions and the erbium ions is obtained; dissolving a fluorine source in deionized water to obtain a solution B containing fluorine ions; and S2, under the heating condition of 50-85 DEG C, dropwise adding the solution B into the solution A, and carrying out stirring reaction, static aging, washing and drying to obtain the erbium-doped calcium fluoride. According to the method, reaction is carried out in an aqueous solution with the temperature higher than the room temperature, the collision probability of calcium ions, erbium ions and fluorine ions is effectively increased, the doping concentration of the erbium ions in calcium fluoride crystal lattices can be increased to the maximum degree in the process that calcium and fluorine ions are combined and react to generate calcium fluoride, and pure-phase calcium fluoride is generated. And the high-concentration erbium-ion-doped erbium-doped calcium fluoride synthesized by the method is simple in process, short in preparation period and beneficial to industrial mass production.

The invention relates to the technical field of fine chemical engineering, in particular to a method for green production of D-tartaric acid by a double-compartment bipolar membrane process, which comprises the following steps: preparing a raw material sodium tartrate solution generated by hydrolysis of a sodium epoxysuccinate solution through a strain into a raw material solution with the mass concentration of 7-8.5%, and carrying out electrodialysis on the raw material solution through a double-compartment bipolar membrane electrodialysis device to obtain D-tartaric acid. Directional ion migration is realized under the action of direct current; sodium ions enter an alkali side through a positive membrane and are combined with hydroxyl ions generated by dissociation of a bipolar membrane to generate a sodium hydroxide solution with the mass concentration of 3-4%; hydrogen ions enter an acid side through the bipolar membrane and are combined with tartrate ions to generate a D-tartaric acid solution, and a D-tartaric acid finished product is obtained through subsequent concentration and drying; through the mode, one-step conversion from sodium tartrate to D-tartaric acid is realized, the cost is reduced, and the yield is improved.

A solid electrolyte composition of the present disclosure includes: a solid electrolyte material having ion-binding properties; and an organic solvent. The organic solvent includes: a halogen-group-containing compound; and at least one selected from the group consisting of an ether-group-containing compound and a hydrocarbon.

The invention discloses a regeneration method of silicon oxide polishing waste liquid and application thereof. The regeneration method comprises the following steps: S1, collecting crystallized or agglomerated silicon oxide polishing waste liquid; s2, adding a hydrofluoric acid aqueous solution into the waste liquid, uniformly mixing for reaction, eroding bonding points on the surfaces of the agglomerated silicon oxide particles by utilizing hydrofluoric acid, converting part of silicon oxide into movable fluosilicate ions, and combining the fluosilicate ions with metal cations in the waste liquid to generate fluosilicate precipitates; s3, performing primary filtration on the mixed solution treated in the step S2 through a first filter medium to remove particles with the particle size greater than a first threshold value so as to obtain a primary filtrate; s4, the primary filtrate is subjected to secondary filtration through a second filter medium, particles with the particle size larger than a second threshold value are removed, fine filtrate is obtained, and the pore diameter of the second filter medium is smaller than that of the first filter medium; and S5, collecting the fine filtrate as a regenerated silicon oxide polishing solution. The invention aims to reduce the chemical mechanical polishing processing cost of the silicon carbide substrate.

In this invention Total Antioxidant Capacity (TAC) is determined by a combined Spectrophotometric and Electrochemical method. A reversible spectroelectrochemical sensor consist of a covalently immobilized organic ligand to indium tin oxide (ITO) coated glass, for the binding of metal cations. A metal ion binding to an organic ligand and an auxiliary ligand gives a colored complex whose color depends on the oxidation state of the metal ion. Due to the antioxidative action of the biological sample, the metal ion is reduced in proportion to the TAC of the biological sample. The change in absorption of a thin layer on ITO glass is measured with an optical detector, based on the principle of total internal reflection. The sensor is returned to its oxidized state using electrochemical oxidation. Measuring the current required for the oxidation of reduced ions, an electrochemical signal proportional to the TAC of sample is obtained.

The invention belongs to the technical field of surface treatment, and particularly relates to a cyanide-free lead-free cupronickel tin electroplating process which comprises the following steps: adding methionine copper, sodium stannate, potassium hydroxide, zinc oxide, potassium carbonate, conducting salt, a brightener, sodium phosphite, 3-aminobenzoic acid ethyl ester methyl sulfonate and a wetting agent to form a plating solution; starting mechanical stirring, heating to a required temperature, putting the workpiece into the plating solution, electroplating, and controlling the current density, the metal ion concentration of the plating solution and the temperature to be within a preset range. According to the copper methionine serving as a copper source, copper is coordinated and combined with amino and carboxyl of methionine to form stable inner complex salt, and the advantage of remarkable hydrolysis resistance is achieved. And multiple coordination groups of methionine anions are chelated with Cu < 2 + >, so that free Cu < 2 + > is stabilized, and refining of coating crystallization is assisted. Sodium phosphite focuses on binding with stannate ions to reduce the reduction potential of tin, and ethyl 3-aminobenzoate methyl sulfonate is preferentially chelated with Cu < 2 + > to improve the reduction potential of copper, so that the problem of large potential difference between copper and tin is solved.

A blood analysis system comprises: a centrifugation unit to receive blood of a subject to hold first capturing molecules, wherein one first capturing molecule binds with, to chemically capture, one molecule or ion that causes coagulation of the plasma and centrifuge to suspend cellular components with a minimal plasma along with a number of the first capturing molecules; a detection unit to receive the plasma with remaining number of the first capturing molecules and unbound molecules and ions, but without the cellular components, to determine concentration of one or more types of molecules and / or ions; and a correction unit to correct the determined concentration of the one or more types of molecules and / or ions.

The high-temperature anti-corrosion and anti-scaling gradient coating comprises a base layer, an adhesion layer is arranged at the top of the base layer, a middle layer is arranged at the top of the adhesion layer, a first anti-incrustation layer and a second anti-incrustation layer are arranged at the top of the middle layer, the first anti-incrustation layer comprises an adhesion layer, and the second anti-incrustation layer comprises a second anti-incrustation layer. The first anti-incrustation layer comprises a plurality of adhesion layers, first IPSE alloy particles are arranged in the adhesion layers, the second anti-incrustation layer comprises a plurality of strip-shaped adhesion layers, and second IPSE alloy particles are arranged in the strip-shaped adhesion layers. According to the high-temperature anti-corrosion and anti-scaling gradient coating for the incinerator, the first anti-scaling layer and the second anti-scaling layer are coated and polished, IPSE alloy particles in the first anti-scaling layer and the second anti-scaling layer are exposed outside, the first IPSE alloy particles and the second IPSE alloy particles release free electrons after making contact with water, the free electrons are combined with calcium and magnesium cations forming scales in the water, and therefore the scale forming effect is improved. The combination of calcium and magnesium with acid radical ions is prevented, so that the scale inhibition effect is achieved.

The invention relates to the technical field of water treatment, in particular to an electrode pair for water softening and an application method thereof.The electrode pair comprises a positive electrode and a negative electrode, and a water passing channel is formed between the positive electrode and the negative electrode; the positive electrode comprises a current collector as well as a supporting middle layer and a resin layer which are sequentially attached to the current collector, and the negative electrode comprises a current collector as well as a catalyst layer, a supporting middle layer and a resin layer which are sequentially attached to the current collector; the resin layer of the positive electrode is an OH-type anion exchange resin layer, and the resin layer of the negative electrode is an H + type cation exchange resin layer; the support middle layer comprises a binder and conductive powder with the particle size of 100-800 meshes; the catalyst layer includes a noble metal catalyst. The catalyst layer is arranged in the negative electrode, the reverse electrode is the positive electrode during regeneration, water is subjected to in-situ electrolysis under the action of an electric field to generate regenerated ions, and resin recovery is achieved together with the electrolysis action of the negative electrode during regeneration; and meanwhile, the supporting middle layer is matched, so that the adhesion stability of the resin layer is improved.

The invention provides a carbazole-thiazole Schiff base fluorescent probe as well as a preparation method and application thereof, and belongs to the technical field of fluorescent probes. The preparation method disclosed by the invention comprises the following steps: mixing a benzothiazole-2-formaldehyde solution and a 3-amino-9-ethyl carbazole solution, and then carrying out a Schiff base condensation reaction, so as to obtain the carbazole-thiazole Schiff base fluorescent probe. The preparation method disclosed by the invention is simple, mild in reaction condition, high in yield and low in cost; the fluorescent probe can identify and detect mercury ions, ferric ions, aluminum ions and chromium ions with high selectivity and high sensitivity through fluorescence and color dual signals, the detection limit is as low as nanomole level, and the fluorescent probe has high sensitivity. After being combined with different target ions, the probe respectively shows obvious color change and fluorescence enhancement under sunlight and ultraviolet light, can realize quick distinguishing by naked eyes, and has wide application prospects in the fields of environmental monitoring, biological imaging, food safety detection and the like.

The application discloses a flexible temperature sensor based on a bionic multi-cell mixed ion pump and a preparation method thereof, and relates to the technical field of flexible electronic sensing. The application adopts thermoplastic polyurethane as a flexible substrate, introduces ionic liquid and nano zinc oxide to construct a bionic multi-cell mixed ion pump structure, and proposes a sensing mechanism of heat-induced reversible hydrogen bond rupture to release free ions. Through the formation of a hydrogen bond network between the surface hydroxyl groups of nano ZnO and the anions of ionic liquid, ions are accurately limited, and ion-electron dual signal amplification is realized in combination with the quantum size effect. The resistance temperature coefficient of the sensor in the high-temperature zone can reach 47.9% / DEG C, the temperature resolution is 0.1 DEG C, the response time is 55 ms, the recovery time is 62 ms, the sensor has excellent zero drift cycle stability and excellent mechanical anti-deformation interference capacity, the tensile strength breaks through 30 MPa, and the elongation at break is close to 400%.

A Cu-61 separation and purification method based on multistage resin combination comprises the following steps: step 1, placing an irradiated target material in HCl, heating until the target material is completely dissolved, and then filtering to obtain a clear solution; 2, filling a chromatographic column with ZR resin for activation; loading the clarified solution obtained in the step 1 to adsorb Ga ions in the clarified solution, and collecting effluent; washing the chromatographic column; step 3, filling AG1-X8 resin into a chromatographic column, loading the ZR resin effluent obtained in the step 2, and then washing; then carrying out gradient elution, and collecting an eluent; and 4, neutralizing the eluent obtained in the step 3, and evaporating and concentrating to a target volume. According to the method, a resin function cooperation mechanism is adopted, the ZR resin has super-strong selectivity and large adsorption capacity on Ga ions on the basis of a hydroxamic acid group, the AG1-X8 resin captures Cu ions through anion exchange, and Cu and Zn isotopes are accurately separated in combination with gradient elution.