Simultaneous quantitation of urinary cotinine and acrylonitrile-derived mercapturic acids with ultraperformance liquid chromatography–tandem mass spectrometry

Acrylonitrile (AN), a widely used industrial chemical also found in tobacco smoke, has been classified as a possible human carcinogen (group 2B) by the International Agency for Research on Cancer. AN can be detoxified by glutathione S-transferase (GST) to form glutathione (GSH) conjugates in vivo. It can be metabolically activated by cytochrome P450 2E1 to form 2-cyanoethylene oxide, which can also be detoxified by GST to generate GSH conjugates. The GSH conjugates can be further metabolized to mercapturic acids (MAs), namely, N-acetyl-S-(2-cyanoethyl)cysteine (CEMA), N-acetyl-S-(2-hydroxyethyl)cysteine (HEMA), and N-acetyl-S-(1-cyano-2-hydroxyethyl)cysteine (CHEMA). This study developed an ultraperformance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS) method to quantitatively profile the major AN urinary metabolites (CEMA, HEMA, and CHEMA) to assess AN exposure, as well as analyze urinary cotinine (COT) as an indicator for tobacco smoke exposure. The limits of quantitation were 0.1, 0.1, 1.0, and 0.05 μg/L for HEMA, CEMA, CHEMA, and COT, respectively. This method was applied to analyze the three AN-derived MAs in 36 volunteers with no prior occupational AN exposure. Data analysis showed significant correlations between the level of COT and the levels of these MAs, suggesting them as biomarkers for exposure to low levels of AN. The results demonstrate that a highly specific and sensitive UPLC-MS/MS method has been successfully developed to quantitatively profile the major urinary metabolites of AN in humans to assess low AN exposure.     

A method for the quantification of biomarkers of exposure to acrylonitrile and 1,3-butadiene in human urine by column-switching liquid chromatography–tandem mass spectrometry

1,3-Butadiene and acrylonitrile are important industrial chemicals that have a high production volume and are ubiquitous environmental pollutants. The urinary mercapturic acids of 1,3-butadiene and acrylonitrile—N-acetyl-S-(3,4-dihydroxybutyl)cysteine (DHBMA) and MHBMA (an isomeric mixture of N-acetyl-S-((1-hydroxymethyl)-2-propenyl)cysteine and N-acetyl-S-((2-hydroxymethyl)-3-propenyl)cysteine) for the former and N-acetyl-S-2-cyanoethylcysteine (CEMA) for the latter—are specific biomarkers for the determination of individual internal exposure to these chemicals. We have developed and validated a fast, specific, and very sensitive method for the simultaneous determination of DHBMA, MHBMA, and CEMA in human urine using an automated multidimensional LC/MS/MS method that requires no additional sample preparation. Analytes are stripped from urinary matrix by online extraction on a restricted access material, transferred to the analytical column, and subsequently determined by tandem mass spectrometry using labeled internal standards. The limits of quantification (LOQs) for DHBMA, MHBMA, and CEMA were 10 μg/L, 2 μg/L, and 1 μg/L urine, respectively, and were sufficient to quantify the background exposure of the general population. Precision within series and between series for all analytes ranged from 5.4 to 9.9%; mean accuracy was between 95 and 115%. We applied the method on spot urine samples from 210 subjects from the general population with no occupational exposure to 1,3-butadiene or acrylonitrile. A background exposure of the general population to acrylonitrile was discovered that is basically influenced by individual exposure to passive smoke as well as active smoking habits. Smokers showed a significantly higher excretion of MHBMA, whereas DHBMA levels did not differ significantly. Owing to its automation, our method is well suited for application in occupational or environmental studies. Figure Boxplots of the results from LC/ESI-MS/MS analysis of urinary excretion of CEMA reveal a strong correlation with nicotine metabolite cotinine, indicating that exposure to passive smoke as well as active smoking is the main source of exposure to acrylonitrile in the general population     

Accurate quantification of mercapturic acids of styrene (PHEMAs) in human urine with direct sample injection using automated column-switching high-performance liquid chromatography coupled with tandem mass spectrometry

Styrene is one of the most important industrial chemicals, with an enormously high production volume worldwide. The urinary mercapturic acids of its metabolite styrene-7,8-oxide, namely N-acetyl-S-(2-hydroxy-1-phenylethyl)-l-cysteine (PHEMA 1) and N-acetyl-S-(2-hydroxy-2-phenylethyl)-l-cysteine (PHEMA 2), are specific biomarkers for the determination of individual internal exposure to this highly reactive intermediate of styrene. We have developed and validated a fast, specific and very sensitive method for the accurate determination of the sum of phenylhydroxyethyl mercapturic acids (PHEMAs) in human urine with an automated multidimensional liquid chromatography–tandem mass spectrometry method using ¹³C₆-labelled PHEMAs as internal standards. Analytes were stripped from the urinary matrix by online extraction on a restricted access material, transferred to the analytical column and subsequently determined by tandem mass spectrometry. The limit of quantification (LOQ) for the sum of PHEMAs was 0.3 μg/L urine and allowed us to quantify the background exposure of the (smoking) general population. Precision within series and between series ranged from 1.5 to 6.8% at three concentrations ranging from 3 to 30 μg/L urine; the mean accuracy was between 104 and 110%. We applied the method to spot urine samples from 40 subjects of the general population with no known occupational exposure to styrene. The median levels (range) for the sum of PHEMAs in urine of non-smokers (n = 22) were less than 0.3 μg/L (less than 0.3 to 1.1 μg/L), whereas in urine of smokers (n = 18), the median levels were 0.46 μg/L (less than 0.3 to 2.8 μg/L). Smokers showed a significantly higher excretion of the sum of PHEMAs (p = 0.02). Owing to its automation and high sensitivity, our method is well suited for application in occupational or environmental studies.     

Sensitive monitoring of monoterpene metabolites in human urine using two-step derivatisation and positive chemical ionisation-tandem mass spectrometry

A gas chromatographic–positive chemical ionisation-tandem mass spectrometric (GC–PCI-MS/MS) method for the simultaneous determination of 10 oxidative metabolites of the monoterpenoid hydrocarbons α-pinene, (R)-limonene, and Δ³-carene ((+)-3-carene) in human urine was developed and tested for the monoterpene biomonitoring of the general population (n = 36). The method involves enzymatic cleavage of the glucuronides followed by solid-supported liquid–liquid extraction and derivatisation using a two-step reaction with N,O-bis(trimethylsilyl)-trifluoroacetamide and N-(trimethylsilyl)imidazole. The method proved to be both sensitive and reliable with detection limits ranging from 0.1 to 0.3 μg L⁻¹. In contrast to the frequent and distinct quantities of (1S,2S,4R)-limonene-1,2-diol, the (1R,2R,4R)-stereoisomer could not be detected. The expected metabolite of (+)-3-carene, 3-caren-10-ol was not detected in any of the samples. All other metabolites were detected in almost all urine samples.     

The synthesis and characterisation of N-(1-carbamoyl-1,1-dialkyl-methyl)-(S)-prolinamides and related pyrrolidin-2-yl-4,5-dihydro-1H-imidazol-5-ones as potential enantioselective organocatalysts

The acylation of substituted 2-aminopropanamides with (2S)-Boc-proline, (2S)-Cbz-proline and (2S)-Bn-proline was used to prepare substituted 1-protected N-(1-carbamoyl-1,1-dialkyl-methyl)-(S)-prolinamides (74-89%), whose subsequent deprotection gave N-(1-carbamoyl-1,1-dialkyl-methyl)-(S)-prolinamides (94-95%). The enantiomerically pure N-(1-carbamoyl-1,1-dialkyl-methyl)-(S)-prolinamides obtained were tested as organocatalysts for the aldol reaction of cyclohexanone with 4-nitrobenzaldehyde, with yields ranging from 38% to 79% ee. The highest enantioselectivity (89% ee) was achieved by catalysis with N-(1-carbamoyl-cyclopentyl)-(S)-prolinamide (methanol, l0% HCl). By the action of sodium methoxide, Boc-N-(1-carbamoyl-cyclopentyl)-(S)-prolinamide was quantitatively cyclised to 2-(1-Boc-pyrrolidin-2-yl)-1,3-diazaspiro[4.4]non-1-en-4-one, which was accompanied by racemisation at the stereogenic centre of the proline skeleton. Alternatively, the substituted 4,4-dialkyl-2-pyrrolidin-2-yl-4,5-dihydro-1H-imidazol-5-ones were prepared by oxidation of 4,4-dialkyl-2-((2S)-1-Boc-pyrrolidin-2-yl)-4,5-dihydro-1H-imidazolidin-5-ones (54-69%). In an acid medium, 2-pyrrolidin-2-yl-1,3-diazaspiro[4.4]non-1-en-4-one and (4S)-4-isopropyl-4-methyl-2-pyrrolidin-2-yl-4,5-dihydro-1H-imidazol-5-one underwent racemisation. Conversely, the free base of (2S)-2-pyrrolidin-2-yl-1,3-diazaspiro[4.4]non-1-en-4-one very easily underwent oxidation to give the achiral 2-(4,5-dihydro-3H-pyrrol-2-yl)-1,3-diazaspiro[4.4]non-1-en-4-one.     

Development of a chiral micellar electrokinetic chromatography–tandem mass spectrometry assay for simultaneous analysis of warfarin and hydroxywarfarin metabolites: Application to the analysis of patients serum samples

The enantioseparation of warfarin (WAR) along with the five positional and optical isomers is challenging because of the difficulty to simultaneously separate and quantitate these chiral compounds. Currently, no effective chiral CE–MS methods exist for the simultaneous enantioseparation of WAR and all its hydroxylated metabolites in a single run. Polymeric surfactants (aka. molecular micelles) are particularly compatible with micellar electrokinetic chromatography–mass spectrometry (MEKC–MS) because they have a wider elution window for enantioseparation and do not interfere with the MS detection of chiral drugs. Using polysodium N-undecenoyl-l,l-leucylvalinate (poly-l,l-SULV) as a chiral pseudophase in MEKC–MS baseline separation of WAR, its five metabolites along with the internal standard was obtained in 45 min. This is in comparison to 100 min required for separation of the same mixture with packed column CEC–MS using a vancomycin chiral stationary phase. Serum samples were extracted with mixed-mode anion-exchange (MAX) cartridge with recoveries of greater than 85.2% for all WAR and hydroxywarfarin (OH-WAR) metabolites. Utilizing the tandem MS and multiple reaction monitoring mode, the MEKC–MS/MS method was used to simultaneously generate calibration curves over a concentration range from 2 to 5000 ng/mL for R- and S-warfarin, 5 to 1000 ng/mL for R- and S-6-, 7-, 8- and 10-OH-WAR and 10 to 1000 ng/mL for R and S-4′-OH-WAR. For the first time, the limits of detection and quantitation for most WAR metabolites by MEKC–MS/MS were found to be at levels of 2 and 5 ng/mL, respectively. The method was successfully applied for the first time to analyze WAR and its metabolites in plasma samples of 55 patients undergoing WAR therapy, demonstrating the potential of chiral MEKC–MS/MS method to accurately quantitate with high sensitivity.     

Thermodynamic properties of CO2 absorption in hydroxyl ammonium ionic liquids at pressures of (100–1600) kPa

Solubility of CO₂ in six hydroxyl ammonium ionic liquids 2-hydroxyethanaminium acetate [hea], bis(2-hydroxyethyl)ammonium acetate [bheaa], 2-hydroxy-N-(2-hydroxyethyl)-N-methylethanaminium acetate [hhemea], 2-hydroxyethanaminium lactate [hel], bis(2-hydroxyethyl)ammonium lactate [bheal], 2-hydroxy-N-(2-hydroxyethyl)-N-methylethanaminium lactate [hhemel] at temperatures (298.15, 313.15, and 328.16) K and pressures ranging from (100 to 1600) kPa was determined. From the experimental solubility data, the Henry’s constant of CO₂ for each hydroxyl ammonium ionic liquids was estimated and reported as a function of temperature. Furthermore, enthalpy and entropy of absorption were obtained from estimated Henry’s constant. The results showed that the solubility increase with increasing pressure and decrease with increasing temperature and the solubility of CO₂ in these six hydroxyl ammonium ionic liquids was in sequence: [hea] > [bheaa] > [hel] > [bheal] > [hhemel] > [hhemea].     

Synthesis, characterization and degradability of the novel aliphatic polyester bearing pendant N-isopropylamide functional groups

The synthesis, characterization, and degradability of the novel aliphatic polyester bearing pendant N-isopropylamide functional group are reported for the first time. 2-(N-Isopropyl-2-carbamoylethyl)cyclohexanone (CCH) was first synthesized by the Michael reaction of N-isopropylacrylamide with cyclohexanone and was subsequently converted into 6-(N-isopropyl-2-carbamoylethyl)-?-caprolactone (CCL) by the Baeyer-Villiger oxidation reaction using 3-chloroperoxybenzoic acid (mCPBA) as the oxidant. Finally, the novel functionalized poly(?-caprolactone) bearing the pendant N-isopropylamide functional groups, poly(6-(N-isopropyl-2-carbamoylethyl)-?-caprolactone-co-?-caprolactone)s (poly(CCL-co-CL)), were carried out successfully by bulk ring-opening polymerization of CCL and ?-CL initiated by Sn(Oct)₂. Poly(CCL-co-CL) were characterized by ¹H NMR, ¹³C NMR, SEC and DSC. The copolymer containing 9.1 mol% CCL formed flexible films and was used to study its degradability. A phosphate buffer (pH = 7.4) with temperature 37 °C was adopted to proceed the degrading study all through. Compared with poly(?-caprolactone), the hydrolytic degradation of poly(CCL-co-CL) was much faster, which is confirmed by the weight loss and change of intrinsic viscosity.     

Quantification of the neurotransmitters melatonin and N-acetyl-serotonin in human serum by supercritical fluid chromatography coupled with tandem mass spectrometry

The aim of this study was developing a supercritical fluid chromatography tandem mass spectrometry (SFC-MS/MS) method and an ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method, for the analysis of N-acetyl-serotonin (NAS) and melatonin (Mel) in human serum, and to compare the performance of these methods. Deuterated isotopologues of the neurotransmitters were synthesized and evaluated for suitability as internal standards in sample preparation. Liquid-liquid extraction was selected as sample preparation procedure. With chloroform, the best extraction solvent tested, an extraction yield of 48 ± 2% for N-acetyl-serotonin and 101 ± 10% for melatonin was achieved. SFC separation was accomplished within 3 min on a BEH stationary phase, employing isocratic elution with 90% carbon dioxide and 0.1% formic acid as well as 0.05% ammonium formate in methanol. For the 4 min UHPLC gradient separation with 0.1% formic acid in water and methanol, respectively, a Kinetex XB-C18 was used as stationary phase. Both chromatographic techniques were optimized regarding mobile phase composition, additives to the mobile phase and column temperature. Multiple reaction monitoring (MRM) analysis was used for quantification of the metabolites. Both methods were validated regarding retention time stability, LOD, LOQ, repeatability and reproducibility of quantification, process efficiency, extraction recovery and matrix effects. LOD and LOQ were 0.017 and 0.05 pg μL⁻¹ for NAS and 0.006 and 0.018 pg μL⁻¹ for Mel in SFC-MS/MS compared to 0.028 and 0.1 pg μL⁻¹ for NAS and 0.006 and 0.017 pg μL⁻¹ for Mel in UHPLC-MS/MS.     

A simple,fast and low-cost turn-on fluorescence method for dopamine detection using in situ reaction

A simple, fast and low-cost method for dopamine (DA) detection based on turn-on fluorescence using resorcinol is developed. The rapid reaction between resorcinol and DA allows the detection to be performed within 5 min, and the reaction product (azamonardine) with high quantum yield generates strong fluorescence signal for sensitive optical detection. The detection exhibits a high sensitivity to DA with a wide linear range of 10 nM–20 μM and the limit of detection is estimated to be 1.8 nM (S/N = 3). This approach has been successfully applied to determine DA concentrations in human urine samples with satisfactory quantitative recovery of 97.84%–103.50%, which shows great potential in clinical diagnosis.     

Synthesis and Characterization of Catechol-Containing Polyacrylamides with Adhesive Properties

In this study, a row of four analogous dopamine acryl- and methacrylamide derivatives, namely N-(3,4-dihydroxyphenyethyl) acrylamide, N-(3,4-dihydroxyphenyethyl) meth acrylamide, N-phenethyl methacrylamide, N-(4-hydroxyphenethyl) methacrylamide were synthesized and characterized by ¹H-NMR and ¹³C-NMR, followed by further solvent-based radical polymerization with N-hydroxyethyl acrylamide. All copolymers were characterized by ¹H-NMR, dynamic differential calorimetry, and gel permeation chromatography. The dependency of the used comonomer ratios to the molecular mass of the corresponding copolymers has been described. The synthesis of the various polymers serves as a feasibility study and provides important data for a future biometric application in the medical field. We synthesized N-(3,4-dihydroxyphenyethyl) acrylamide copolymer up to 80 mol% by free radical polymerization without using any protecting groups. All polymers show identical perfect adhesive properties by a simple scratch test. Further, the monomers were used as a photo reactive glue formulation to test its adherence to a medical titanium surface sample by tensile shear test.     

A practical enantioselective total synthesis of (−)-(S)-stepholidine

A convergent enantioselective total synthesis of (−)-(S)-stepholidine, a drug candidate for the treatment of schizophrenia and/or drug abuse, was described, which represented the first example of successful auxiliary-assisted Bischler–Napieralski cyclization of amide bearing bromine atom at 2-position of the C ring, followed by an introduction of the aryl methyl ester via Br–Li exchange. (−)-(S)-Stepholidine was synthesized in 6 steps, with 52% overall yield and >99% ee. The reported synthesis is practically free from chromatographic separation.     

Rare direct imidation of aromatic metallacycle by reaction of CpCo(dithiolene) complex with N-halosuccinimide

The aromatic [CpCo(S₂C₂(R)(H))] (R = Ph, Me, 9-phenanthryl, H) complexes reacted with N-halosuccinimides (NXS; X = Cl, Br, I) in carbon tetrachloride at room temperature to undergo the N-succinimide substitution reaction on the dithiolene ring, but no halogenated dithiolene complex was obtained. The imidation products [CpCo(S₂C₂(R)(N-sccinimide))] were yielded up to 64% where X = I and R = 9-phenanthryl. The reaction of [CpCo(S₂C₂(Ph)(H))] with N-bromophthalimide (NBP) also gave the imidation product [CpCo(S₂C₂(Ph)(N-phthalimide))]. This is the rare direct imidation reaction to an aromatic metallacycle by NXS. The reaction of [CpCo(S₂C₂H₂)] (R = H) with NIS afforded the double imidation product. One by-product in this reaction was the dithiolene-dithiolene homo-coupling product [CpCo(S₂C₂(R))]₂ (R = Ph, Me, 9-phenanthryl). The microwave-enhanced (MW) reactions were attempted in the carbon tetrachloride solution. Although the solution temperature increased up to only 43 °C by MW irradiation, the imidation reaction worked with short reaction time.     

The interactions between some N-acetyl-N′-methyl-l-α-amino acid amides and urea in water at 298.15 K

The enthalpies of solution of N-acetyl-N′-methylglycinamide, N-acetyl-N′-methyl-l-α-alaninamide, N-acetyl-N′-methyl-l-α-leucinamide and N-acetyl-N′-methyl-l-α-serinamide have been measured in water and in aqueous urea solutions with molalities from 0.25 to 3.0 mol kg⁻¹ at 298.15 K. From these data the standard dissolution enthalpies of amides in aqueous urea solutions have been determined. The results have been treated according to McMillan-Mayer's theory in order to obtain the enthalpic coefficients of the interactions between amino acid derivatives and urea molecules. The obtained parameters were compared with the hydrophobic scale for the amino acid side chains.     

Synthesis of a water-soluble chiral NMR shift reagent: (S)-PDTA

A five-step synthesis of the water-soluble chiral polydentate ligand, (S)-PDTA [(S)-PDTA = N,N,N′,N′-tetrakis[(hydroxycarbonyl)methyl]-(S)-1,2-diaminopropane] starting from l-alanine has been worked out, via steps with retention of chirality. Total yield is 50.7% (average of ～88% for each step), while published methods report 33.4% total yield over four steps.     

Stereospecific ligands and their complexes. IV: Synthesis,characterization and cytotoxicity of novel platinum(IV) complexes with ethylenediamine-N,N′-di-S,S-2-propanoate and halogenido ligands: Crystal structure of s-cis-[Pt(S,S-eddp)Cl2]·4H2O and uns-cis-[Pt(S,S-eddp)Br2]

The syntheses of two novel platinum(IV) complexes of formula [PtX₂(S,S-eddp)]·nH₂O (S,S-eddp = ethylenediamine-N,N′-di-S,S-2-propanoate ion, X = chlorido (1) or bromido (2), n = 4, 0) are reported. The complexes have been obtained by direct reaction of corresponding potassium hexahalogenidoplatinate(IV) with neutralized ethylenediamine-N,N′-di-S,S-2-propanoic acid (H₂-S,S-eddp). The complexes were characterized by elemental analysis, infrared, ¹H and ¹³C NMR spectroscopy. The spectroscopically predicted geometrical configurations of the obtained complexes were confirmed by X-ray analyses of the crystal structures of the s-cis-[Pt(S,S-eddp)Cl₂]·4H₂O and uns-cis-[Pt(S,S-eddp)Br₂]. These complexes displayed significantly lower in vitro cytotoxicity in comparison to cisplatin.     

In vitro stable isotope labeling for discovery of novel metabolites by liquid chromatography–mass spectrometry: Confirmation of γ-tocopherol metabolism in human A549 cell

A general approach for discovering novel catabolic metabolites from a parent biocompound was developed and validated on the metabolism of γ-tocopherol in human A549 cell. The method is based on LC–MS analysis of in vitro stable isotope-labeled metabolites and assumes that a parent compound and its metabolites share a common functional group that can be derivatized by well-documented reagents. In this method, two equal aliquots of extracted metabolites are separately derivatized with isotope-coded (heavy) and non-isotope-coded (light) form of derivatizing reagent, mixed at 1:1 ratio and analyzed using LC–MS. The metabolites with common functional group are then easily recognized by determination of a chromatographically co-eluted pair of isotopomers (MS doublet peaks) with similar peak intensities and mass difference corresponding to the mass difference between heavy and light form of derivatization reagent. The feasibility of this approach was demonstrated and validated by the identification of products of γ-tocopherol catabolism in human A549 cell culture media using N-methyl-nicotinic acid N-hydroxysuccinimide ester (C1-NANHS) and N-methyl-d3-nicotinic acid N-hydroxysuccinimide ester (C1-d3-NANHS) derivatizing reagent. Overall four γ-tocopherol metabolites were identified including 9′-COOH, 11′-COOH, 13′-COOH and 13′-OH. In addition, the developed LC–MS method can also be used for the fast and sensitive quantitative analysis of γ-tocopherol and other forms of vitamin E related compounds.     

Synthesis of thio-C-glycosides from 2′-carbonylalkyl C-glycosides by a tandem β-elimination and intramolecular hetero-Michael addition

2′-Carbonyl 5-S-acetyl-C-glycofuranosides and 2′-carbonyl 4-S-acetyl-C-glycopyranosides were converted in good yields to respective 5-thio-C-glycopyranosides and 4-thio-C-glycofuranosides under base treatment. The transformation was resulted from β-elimination on 2′-carbonyl C-glycoside to form α,β-conjugated aldehyde (or ketone) and following intramolecular hetero-Michael addition by the thiol group.     

Synthesis of a novel electrode material containing phytic acid-polyaniline nanofibers for simultaneous determination of cadmium and lead ions

The development of nanostructured conducting polymers based materials for electrochemical applications has attracted intense attention due to their environmental stability, unique reversible redox properties, abundant electron active sites, rapid electron transfer and tunable conductivity. Here, a phytic acid doped polyaniline nanofibers based nanocomposite was synthesized using a simple and green method, the properties of the resulting nanomaterial was characterized by electrochemical impedance spectroscopy (EIS), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). A glassy carbon electrode modified by the nanocomposite was evaluated as a new platform for the simultaneous detection of trace amounts of Cd²⁺ and Pb²⁺ using differential pulse anodic stripping voltammetry (DPASV). The synergistic contribution from PANI nanofibers and phytic acid enhances the accumulation efficiency and the charge transfer rate of metal ions during the DPASV analysis. Under the optimal conditions, good linear relationships were obtained for Cd²⁺ in a range of 0.05–60 μg L⁻¹, with the detection limit (S/N = 3) of 0.02 μg L⁻¹, and for Pb²⁺ in a range of 0.1–60 μg L⁻¹, with the detection limit (S/N = 3) of 0.05 μg L⁻¹. The new electrode was successfully applied to real water samples for simultaneous detection of Cd²⁺ and Pb²⁺ with good recovery rates. Therefore, the new electrode material may be a capable candidate for the detection of trace levels of heavy metal ions.