Capillary electrophoresis of microbial aggregates

Uncontrolled aggregation of bacterial cells is a significant disadvantage of electrophoretic separations. Various aspects of the electrophoretic behavior of different strains of Gram‐positive Bacillus cereus, Bacillus subtilis, Sarcina lutea, Staphylococcus aureus(1), and Micrococcus luteus bacteria and Gram‐negative Escherichia coli bacteria were investigated in this study. Our findings indicate that bacteria can be rapidly analyzed by CZE with surface charge modification by calcium ions (Ca²⁺). Bound Ca²⁺ ions increase zeta potential to more than 2.0 mV and significantly reduce repulsive forces. Under the above conditions, bacterial cells create compact aggregates, and fewer high‐intensity signals are observed in electropherograms. The above can be attributed to the bridging effect of Ca²⁺ between bacterial cells. CE was performed to analyze bacterial aggregates in an isotachophoretic mode. A single peak was observed in the electropherogram.     

A Glycosylated Covalent Organic Framework Equipped with BODIPY and CaCO3 for Synergistic Tumor Therapy

Ca²⁺, a ubiquitous but nuanced modulator of cellular physiology, is meticulously controlled intracellularly. However, intracellular Ca²⁺ regulation, such as mitochondrial Ca²⁺ buffering capacity, can be disrupted by ¹O₂. Thus, the intracellular Ca²⁺ overload, which is recognized as one of the important cell pro‐death factors, can be logically achieved by the synergism of ¹O₂ with exogenous Ca²⁺ delivery. Reported herein is a nanoscale covalent organic framework (NCOF)‐based nanoagent, namely CaCO₃@COF‐BODIPY‐2I@GAG ( 4 ), which is embedded with CaCO₃ nanoparticle (NP) and surface‐decorated with BODIPY‐2I as photosensitizer (PS) and glycosaminoglycan (GAG) targeting agent for CD44 receptors on digestive tract tumor cells. Under illumination, the light‐triggered ¹O₂ not only kills the tumor cells directly, but also leads to their mitochondrial dysfunction and Ca²⁺ overload. An enhanced antitumor efficiency is achieved via photodynamic therapy (PDT) and Ca²⁺ overload synergistic therapy.     

Aggregation and fusion of phospholipid vesicles

Membrane fusion and aggregation of phospholipid vesicles are reviewed and discussed. The fusion process is viewed as consisting of several stages: aggregation and close apposition of the particles, destabilization, and finally, merging of the bilayers. A procedure is presented which yields both the rate constant of the dimerization (C₁₁) and the rate constant for fusion of the dimers (f₁₁), which is a direct measure of the probability that two apposed vesicles will fuse. Experimental methods used in the study of membrane fusion are reviewed, primarily with respect to their capacity to monitor the kinetics of vesicle fusion. A few kinetic studies on the mixing of aqueous contents, leakage and increase in size of fusing vesicles are presented in detail.The range of C₁₁ values for Ca²⁺-induced aggregation and fusion of small unilamellar vesicles (SUV, ～ 125 Å radius) composed of phosphatidylserine (PS) is 10⁶ to 5 × 10⁷ M^-1 in the presence of Ca²⁺ concentrations from 1.15 to 2 mM, respectively. For larger PS vesicles (LUV, ～ 500 Å radius) C₁₁ = 6.5 × 10⁷ M^-1s^-1 in the presence of 5 mM Ca²⁺. These values are in good agreement with theoretical calculations based on van der Waals and electrostatic interactions, in which binding of cations is explicitly taken into account. The rate constants of fusion, f₁₁, are 5 s^-1 for PS SUV and 0.08 s^-1 for LUV in the presence of 2 mM and 5 mM Ca²⁺, respectively. The significance of these fusion rate constants to the duration of the fusion event is discussed.Factors affecting fusion such as cations, temperature, membrane composition vesicle concentration and size are reviewed and analyzed. Di- or tri-valent cations induce fusion of acidic phospholipid vesicles (except for phosphatidylinositol) in either pure or mixed form. Among the neutral phospholipids, phosphatidylcholine (PC) inhibits but phosphatidylethanolamine (PE) sustains or enhances the fusion capacity of acidic phospholipid vesicles. Monovalent cations induce reversible aggregation of negatively charged vesicles, but they inhibit the fusion induced by divalent cations such as Ca²⁺ or Mg²⁺. Fusion of neutral phospholipid vesicles, and it occurs the cation-induced fusion of acidic phospholipid vesicles, and it occurs only at temperatures below the gel to liquid crystalline phase transition temperature Tc. This is in contrast to the acidic phospholipid vesicle fusion which is greatly enhanced when the temperature is above the Tc of the phospholipid.     

Highly Selective Detection of 2,4,6‐Trinitrophenol and Cu2+ Ions Based on a Fluorescent Cadmium–Pamoate Metal–Organic Framework

A luminescent cadmium–pamoate metal–organic framework, [Cd₂(PAM)₂(dpe)₂(H₂O)₂]?0.5(dpe) ( 1 ), has been synthesized under hydrothermal conditions by using π‐electron‐rich ligands 4,4′‐methylenebis(3‐hydroxy‐2‐naphthalenecarboxylic acid) (H₂PAM) and 1,2‐di(4‐pyridyl)ethylene (dpe). Its structure is composed of both mononuclear and dinuclear Cd^II building units, which are linked by the PAM and dpe ligands, resulting in a (4,8)‐connected 3D framework. The π‐conjugated dpe guests are located in a 1D channel of 1 . The strong emission of 1 could be quenched efficiently by trace amounts of 2,4,6‐trinitrophenol (TNP), even in the presence of other competing analogues such as 4‐nitrophenol, 2,6‐dinitrotoluene, 2,4‐dinitrotoluene, nitrobenzene, 1,3‐dinitrobenzene, hydroquinone, dimethylbenzene, and bromobenzene. The high sensitivity and selectivity of the fluorescence response of 1 to TNP shows that this framework could be used as an excellent sensor for identifying and quantifying TNP. In the same manner, 1 also exhibits superior selectivity and sensitivity towards Cu²⁺ compared with other metal ions such as Zn²⁺, Mn²⁺, Mg²⁺, K⁺, Na⁺, Ni²⁺, Co²⁺, and Ca²⁺. This is the first MOF that can serve as a dual functional fluorescent sensor for selectively detecting trace amounts of TNP and Cu²⁺.     

Double Metal Ions Competitively Control the Guest‐Sensing Process: A Facile Approach to Stimuli‐Responsive Supramolecular Gels

A facile approach to the design of stimuli‐responsive supramolecular gels (SRSGs) termed double‐metal‐ion competitive coordination control is reported. By this means, the fluorescence signals and guest‐selective responsiveness of the SRSGs are controlled by the competitive coordination of two different metal ions with the gelators and the target guest. To demonstrate this approach, a gelator G2 based on multiple self‐assembly driving forces was synthesized. G2 could form Ca²⁺‐coordinated metallogel CaG with strong aggregation‐induced emission (AIE). Doping of CaG with Cu²⁺ results in AIE quenching of CaG and formation of Ca²⁺‐ and Cu²⁺‐based metallogel CaCuG. CaCuG could fluorescently detect CN^? with specific selectivity through the competitive coordination of CN^? with the Cu²⁺ and the coordination of Ca²⁺ with G2 again. This approach may open up routes to novel stimuli‐responsive supramolecular materials.     

Supramolecular Vesicles Based on Water‐Soluble 2,6‐Helic[6]arene: High Affinity Binding,Stimuli Responsiveness and Delivery of Doxorubicin to Cancer Cells

Water‐soluble 2,6‐helic[6]arene was used to construct supramolecular vesicles via host‐guest interaction. Water‐soluble 2,6‐helic[6]arene was discovered to be high affinity host for suitable biomarkers. Supramolecular vesicles were responsive to multiple stimuli types, including temperature, pH, Ca²⁺, CO₂ bubbling and biomarker displacement. Supramolecular vesicles were used to load and deliver anti‐ tumor drug doxorubicin to HeLa cells in vitro.     

Analysis of allergens in tubeimu saponin extracts by using rat basophilic leukemia 2H3 cell‐based affinity chromatography coupled to liquid chromatography and mass spectrometry

An affinity two‐dimensional chromatography method was developed for the recognition, separation, and identification of allergic components from tubeimu saponin extracts, a preparation often injected to treat various conditions as indicated by traditional Chinese medicine. Rat basophilic leukemia‐2H3 cell membranes were used as the stationary phase of a membrane affinity chromatography column to capture components with affinity for mast cells that could be involved in a degranulation reaction. The retained components were enriched and analyzed by membrane affinity chromatography with liquid chromatography and mass spectrometry via a port switch valve. Suitability and reliability of the method was investigated using appropriate standards, and then, the method was applied to identify components retained from tubeimu saponin extracts. Tubeimoside A was identified in this way as a potential allergen, and degranulation assays confirmed that tubeimoside A induces RBL‐2H3 cell degranulation in a dose‐dependent manner. An increase in Ca²⁺ influx indicated that degranulation induced by tubeimoside A is likely Ca²⁺ dependent. Coupled with the degranulation assay, RBL‐2H3 cell‐based affinity chromatography coupled with liquid chromatography and mass spectrometry is an effective method for screening and identifying allergic components from tubeimu saponin extracts.     

Cation-mediated interaction of dextran sulfate with phospholipid vesicles: binding, vesicle surface polarity, leakage and fusion

 The interaction of dextran sulfate (DS) with dimyristoylphosphatidylcholine (DMPC) large unilamellar vesicles was investigated. DS of different molecular weights (1, 8, 40 and 500 kDa) and divalent cations (Ca²⁺, Mg²⁺ and Mn²⁺) and the trivalent cation La³⁺ were used in the experiments. Binding of DS was studied by use of the microelectrophoresis and monolayer technique. Binding depends strongly on cation and NaCl concentrations in the medium and does not occur in the absence of multivalent cations. Binding is modulated by the molecular weight of the polymers; DS with lower molecular weights lead to less negative zeta potentials at identical concentrations. A comparable monomer of DS, glucose-6-sulfate, does not change the zeta potential of DMPC vesicles. Monolayer experiments revealed a decrease in surface pressure after addition of multivalent cations and DS, indicating a stronger interaction of the cation–polymer complex with the phosphatidylcholine headgroups than its penetration into the phospholipid (PL) bilayer. The cation-mediated binding of DS to the vesicles leads to aggregation of the vesicles. The tendency to promote aggregation of DMPC vesicles is La³⁺>Ca²⁺>Mn²⁺≥ Mg²⁺. The aggregated vesicles show a stacklike arrangement of the bilayers as shown by freeze-fracture electron microscopy. The strong aggregation is accompanied by lipid mixing measured by the 1,4-nitrobenzo-2-oxa-1,3-diazole–phosphatidylethanolamine (PE)/lissamine rhodamine B sulfonyl-PE assay. At low ionic strength substantial lipid mixing can be observed in the previously mentioned order of the cations. This lipid mixing is accompanied by an increase in the permeability of the vesicles as revealed by the 1-aminonaphthalene-3,6,8-trisulfonic acid/p-xylenebis (pyridiium bromide) assay. The extent of leakage is determined by the cation used and the DS molecular weight. These interaction processes between the opposing bilayers are connected with a decrease in the water content in the gap between the opposing PL bilayers. As a measure for the change of the polar properties of the vesicle surface the shift of the emission wavelength of the fluorescent probe dansylphosphatidylethanolamine was measured. The effectiveness of divalent/trivalent cations to decrease the surface dielectric constant of DMPC vesicles also followed the sequence of ions as found for binding, PL mixing and leakage. The results are discussed in terms of the changed hydration at the bilayer surface induced by DS in the presence of multivalent ions. Received: 16 December 1998/Accepted: 17 December 1999     

Induced Color Change of Conjugated Polymeric Vesicles by Interfacial Catalysis of Phospholipase A2

A blue to red color change is induced on addition of phospholipase A₂ to modified PDA vesicles 1 (PDA=polydiacetylene). This bathochromic transition results from chemical modification of the vesicles by hydrolysis of the enzyme substrate embedded in the PDA matrix. Addition of a known phospholipase inhibitor or removal of Ca²⁺ ions suppresses the color change, which suggests the potential for applications in high‐throughput screening assays.     

New Calcium‐Selective Smart Contrast Agents for Magnetic Resonance Imaging

Calcium plays a vital role in the human body and especially in the central nervous system. Precise maintenance of Ca²⁺ levels is very crucial for normal cell physiology and health. The deregulation of calcium homeostasis can lead to neuronal cell death and brain damage. To study this functional role played by Ca²⁺ in the brain noninvasively by using magnetic resonance imaging, we have synthesized a new set of Ca²⁺‐sensitive smart contrast agents (CAs). The agents were found to be highly selective to Ca²⁺ in the presence of other competitive anions and cations in buffer and in physiological fluids. The structure of CAs comprises Gd³⁺‐DO3A (DO3A=1,4,7‐tris(carboxymethyl)‐1,4,7,10‐tetraazacyclododecane) coupled to a Ca²⁺ chelator o‐amino phenol‐N,N,O‐triacetate (APTRA). The agents are designed to sense Ca²⁺ present in extracellular fluid of the brain where its concentration is relatively high, that is, 1.2–0.8 mM . The determined dissociation constant of the CAs to Ca²⁺ falls in the range required to sense and report changes in extracellular Ca²⁺ levels followed by an increase in neural activity. In buffer, with the addition of Ca²⁺ the increase in relaxivity ranged from 100–157 %, the highest ever known for any T₁‐based Ca²⁺‐sensitive smart CA. The CAs were analyzed extensively by the measurement of luminescence lifetime measurement on Tb³⁺ analogues, nuclear magnetic relaxation dispersion (NMRD), and ¹⁷O NMR transverse relaxation and shift experiments. The results obtained confirmed that the large relaxivity enhancement observed upon Ca²⁺ addition is due to the increase of the hydration state of the complexes together with the slowing down of the molecular rotation and the retention of a significant contribution of the water molecules of the second sphere of hydration.     

A model for cation adsorption to clays and membranes

A cation adsorption model is presented and its recent applications are discussed. The model combines electrostatic equations with specific binding, and considers neutral and positively charged complexes between the negative surface sites and organic cations in a closed system. Extensions in the model account for dye aggregation in solution, and for the formation of solution complexes of inorganic cations, such as [M⁺⁺ Cl^–]⁺. The amounts of 45Ca²⁺ adsorbed to vesicles extracted from the plasma membranes of melon root cells could be adequately simulated and predicted. The binding coefficients determined for Ca²⁺, Na⁺, and Mg²⁺ are in the range of values previously deduced for binding to phospholipid components. Model calculations were applied to the test of hypotheses on the effect of salt stress on the growth of roots. The adsorption of monovalent organic cations to montmorillonite is characterized by binding coefficients that are at least six orders of magnitude larger than those of Na⁺, Mg²⁺, Ca²⁺, and Cd²⁺, or those of CdCl⁺ or CaCl⁺. Monovalent organic cations were found to adsorb 140–200% of the cation exchange capacity of the clay and to cause charge reversal. Deductions from adsorption results of acriflavin are consistent with those drawn from the application of other experimental methods. Preliminary results on the adsorption of divalent organic cations are presented. Agro-environmental applications of organo-clays are discussed.     

Light-regulated permeability of rhodopsin-phospholipid membrane vesicles.

Abstract—Light absorption by rhodopsin in receptor cell membranes initiates the excitation of the receptor cell. Rhodopsin-phospholipid membrane vesicles were studied to localize initial transduction events. Rhodopsin-phospholipid recombinant membranes are thermally stable and light sensitive and may be chemically regenerated after bleaching in the same manner as receptor cell membranes. Rhodopsin-containing vesicles prepared from unsaturated phosphatidylcholine (PCho) or PCho and phosphatidylethanolaminc display kinetics for the metarhodopsin I to II transition which are comparable to those of receptor cell membranes. NMR spectroscopy was used to examine the permeability of the membrane vesicles to added shift (Eu³⁺) or relaxation reagents (Mn²⁺, Co²⁺). Unexposed rhodopsin-phospholipid vesicles are sealed to ion movement and become permeable after light exposure. Selected ions (Ca²⁺, Mn²⁺, Co²⁺) may be photoreleased from the interior of loaded membrane vesicles. The quantity released is proportional to the initial ionic concentration. The number of ions released/rhodopsin bleached is dependent on the light intensity, and high yields (40–160) of Ca²⁺/rhodopsin bleached are observed at low levels of light bleaching. The present results indicate that rhodopsin spans the phospholipid bilayer membrane, and are consistent with an increase in the permeability of the membrane initiated by light excitation of rhodopsin.     

A Synthetic Fluorescent Mitochondria‐Targeted Sensor for Ratiometric Imaging of Calcium in Live Cells

Ca²⁺ handling by mitochondria is crucial for cell life and the direct measure of mitochondrial Ca²⁺ concentration in living cells is of pivotal interest. Genetically‐encoded indicators greatly facilitated this task, however they require demanding delivery procedures. On the other hand, existing mitochondria‐targeted synthetic Ca²⁺ indicators are plagued by several drawbacks, for example, non‐specific localization, leakage, toxicity. Here we report the synthesis and characterization of a new fluorescent Ca²⁺ sensor, named mt‐fura‐2, obtained by coupling two triphenylphosphonium cations to the molecular backbone of the ratiometric Ca²⁺ indicator fura‐2. Mt‐fura‐2 binds Ca²⁺ with a dissociation constant of ≈1.5 μm in vitro. When loaded in different cell types as acetoxymethyl ester, the probe shows proper mitochondrial localization and accurately measures matrix [Ca²⁺] variations, proving its superiority over available dyes. We describe the synthesis, characterization and application of mt‐fura‐2 to cell types where the delivery of genetically‐encoded indicators is troublesome.     

Synthesis of Novel 4‐((Substituted bis‐indolyl)methyl)‐benzo‐15‐crown‐5 for the Colorimetric Detection of Hg2+ Ions in an Aqueous Medium

A practical, two‐step synthesis of novel 4‐(substituted bis‐indolyl)methyl)benzo‐15‐crown‐5 has been reported. The strategy employed for the synthesis of the desired molecules involved Duff formylation of benzo‐15‐crown‐5 to get 4‐formyl benzo‐15‐crown‐5 followed by subsequent reactions with substituted indoles in trifluoroacetic acid to yield novel 4‐(substituted bis‐indolyl)methyl)benzo‐15‐crown‐5 in moderate to good yield. One of the reported novel molecule tested for the complexation behavior with various metal cations, such as Li⁺, Na⁺, K⁺, Mg²⁺ Ca²⁺, Al³⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Sn²⁺, Ba²⁺, Hg²⁺, and Pb²⁺, showed a visual colorimetric probe for the detection of mercury cations (Hg²⁺) in an aqueous medium.     

Investigation of DOTA–Metal Chelation Effects on the Chemical Shift of 129Xe

Recent work has shown that xenon chemical shifts in cryptophane‐cage sensors are affected when tethered chelators bind to metals. Here, we explore the xenon shifts in response to a wide range of metal ions binding to diastereomeric forms of 1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid (DOTA) linked to cryptophane‐A. The shifts induced by the binding of Ca²⁺, Cu²⁺, Ce³⁺, Zn²⁺, Cd²⁺, Ni²⁺, Co²⁺, Cr²⁺, Fe³⁺, and Hg²⁺ are distinct. In addition, the different responses of the diastereomers for the same metal ion indicate that shifts are affected by partial folding with a correlation between the expected coordination number of the metal in the DOTA complex and the chemical shift of ¹²⁹Xe. These sensors may be used to detect and quantify many important metal ions, and a better understanding of the basis for the induced shifts could enhance future designs.     

A Highly Selective Fluorescence Turn‐On Sensor for Extracellular Calcium Ion Detection

A highly water‐soluble, fluorescence turn‐on sensor for Ca²⁺ is reported. The sensor affords high selectivity in sensing Ca²⁺ over other biologically important metal cations. The dissociation constant of the sensor in binding Ca²⁺ is 0.92 mm . Fluorescence microscopy experiments demonstrate that the sensor is cell‐impermeable and capable of detecting extracellular Ca²⁺.     

Observation of salt-induced β-lactoglobulin aggregation using sedimentation field-flow fractionation

Sedimentation field-flow fractionation (SdFFF) was applied in order to characterize particle sizes of β-lactoglobulin aggregates induced by Ca²⁺ or Zn²⁺. Aggregation induced by Zn²⁺ was faster than that induced by Ca²⁺. Effects of Zn²⁺ and β-lactoglobulin concentrations, as well as contact time, on the aggregation of β-lactoglobulin were examined. All factors exhibited a combined effect on the size of aggregates, whereby larger aggregates were obtained at increased concentrations of Zn²⁺ and β-lactoglobulin. At fixed concentrations of 2% (w/v) β-lactoglobulin and 10 mM Zn²⁺, the particle size of the aggregates increased from 0.19 μm (at 15 min) to 0.38 μm (at 2880 min). Further, a hyphenated technique of SdFFF and inductively coupled plasma–optical emission spectrometry (ICP–OES) was used to examine whether intermolecular ionic bridges take part in salt-induced β-lactoglobulin aggregation. With SdFFF–ICP–OES, protein–cation–protein cross-linkages were observed for β-lactoglobulin aggregation induced by Zn²⁺, but not for that induced by Ca²⁺.      

A New Fluorescent Chemosensor for Cu2+ Based on 1,2,3,4,5,6,7,8,9,10‐Decahydroacridine‐1,8‐dione Fluorophore

A new chemosensor for Cu²⁺ was synthesized based on 1,2,3,4,5,6,7,8,9,10‐decahydroacridine‐1,8‐dione dyes, which exhibited an obvious fluorescent selectivity to the sensing of Cu²⁺ ions over other cations, such as Na⁺, K⁺, Ca²⁺, Cd²⁺, Co²⁺, Hg²⁺, Mg²⁺, Mn²⁺, Ni²⁺, Zn²⁺, Ag⁺ and Pb²⁺. Moreover, it presented a fluorescent switch function when EDTA was added to the compound‐Cu²⁺ complex in examined systems.     

A new caged Ca2+, azid-1, is far more photosensitive than nitrobenzyl-based chelators

Background: Photolabile chelators that release Ca²⁺ upon illumination have been used extensively to dissect the role of this important second messenger in cellular processes such as muscle contraction and synaptic transmission. The caged calcium chelators that are presently available are often limited by their inadequate changes in Ca²⁺ affinity, selectivity for Ca²⁺ over Mg²⁺ and sensitivity to light. As these chelators are all based on nitrobenzyl photochemistry, we explored the use of other photosensitive moieties to generate a new caged calcium with improved properties.Results: Azid-1 is a novel caged calcium in which a fluorescent Ca²⁺ indicator, fura-2, has been modified with an azide substituent on the benzofuran 3-position. Azid-1 binds Ca²⁺ with a dissociation constant (K_d) of ∼230 nM, which changes to 120 μM after photolysis with ultraviolet light (330–380 nm). Mg²⁺ binding is weak (8–9 mM K_d) before or after photolysis. Azid-1 photolyzes with unit quantum efficiency, making it 40–170-fold more sensitive to light than caged calciums used previously. The photolysis of azid-1 probably releases N₂ to form a nitrenium ion that adds water to yield an amidoxime cation; the electron-with-drawing ability of the amidoxime cation reduces the chelator's Ca²⁺ affinity within at most 2 ms following a light flash. The ability of azid-1 to function as a caged calcium in living cells was demonstrated in cerebellar Purkinje cells, in which Ca²⁺ photolytically released from azid-1 could replace the normal depolarization-induced Ca²⁺ transient in triggering synaptic plasticity.Conclusions: Azid-1 promises to be a useful tool for generating highly controlled spatial and temporal increases of Ca²⁺ in studies of the many Ca²⁺-dependent biological processes. Unlike other caged calciums, azid-1 has a substantial cross section or shows a high susceptibility for two-photon photolysis, the only technique that confines the photochemistry to a focal spot that is localized in three dimensions. Azide photolysis could be a useful and more photosensitive alternative to nitrobenzyl photochemistry.     

Application of mercapto‐silica polymerized high internal phase emulsions for the solid‐phase extraction and preconcentration of trace lead(II)

A new class of solid‐phase extraction column prepared with grafted mercapto‐silica polymerized high internal phase emulsion particles was used for the preconcentration of trace lead. First, mercapto‐silica polymerized high internal phase emulsion particles were synthesized by using high internal phase emulsion polymerization and carefully assembled in a polyethylene syringe column. The influences of various parameters including adsorption pH value, adsorption and desorption solvents, flow rate of the adsorption and desorption procedure were optimized, respectively, and the suitable uploading sample volumes, adsorption capacity, and reusability of solid phase extraction column were also investigated. Under the optimum conditions, Pb²⁺ could be preconcentrated quantitatively over a wide pH range (2.0–5.0). In the presence of foreign ions, such as Na⁺, K⁺, Ca²⁺, Zn²⁺, Mg²⁺, Cu²⁺, Fe²⁺, Cd²⁺, Cl^? and NO₃^?, Pb²⁺ could be recovered successfully. The prepared solid‐phase extraction column performed with high stability and desirable durability, which allowed more than 100 replicate extractions without measurable changes of performance. The feasibility of the developed method was further validated by the extraction of Pb²⁺ in rice samples. At three spiked levels of 40.0, 200 and 800 μg/kg, the average recoveries for Pb²⁺ in rice samples ranged from 87.3 to 105.2%.