Effect of concomitant analytes on As signal during pre-evaporation of the solvent prior to introduction into inductively coupled plasma mass spectrometry

Axial profiling was done, with detection by inductively coupled plasma time-of-flight mass spectrometry, to investigate how a pre-evaporation extension interface (i.e. heated glass tube between the nebulizer and the torch) affects the signal from As and other analytes. A reproducible axial profile was observed for As⁺ in a 20-μg/L multielemental solution in 1% HNO₃, with a signal enhancement ratio (heated/unheated) of 1.55, (obtained by taking the ratio of the signal observed at the optimal axial position in each case). In contrast, the axial profile of a 20-μg/L monoelemental As solution also in 1% HNO₃ showed a signal intensity ratio (heated/unheated) of 0.65 (very similar to that for Se). No such difference in signal was observed for all the other analytes investigated, which are ionic in solution, in contrast to As and Se, which would be mostly in neutral form in 1% HNO₃. In fact, for ionic analytes, the optimal signal upon heating was similar or higher than that without heating, with an inverse dependency on analyte mass. Increasing the number of concomitant analytes and/or their concentration enhanced the As⁺ signal upon heating the interface. Switching to a 0.01 M NaOH matrix, which would not evaporate and would dominate the ionic strength even if As is then entirely in anionic form, similarly resulted in enhancement of the As signal upon heating the extension. All these observations could be rationalized by changes in the number of Coulomb fission events occurring during pre-evaporation, which depend on the size and charge of droplets, as well as the identity and concentration of the matrix.     

Inductively coupled plasma mass spectrometry with an enlarged sampling orifice and offset ion lens. II. Polyatomic Ion interferences and matrix effects

A new inductively coupled plasma mass spectrometer with an enlarged sampling orifice (1.31-mm dia.) and an offset ion lens yields very low levels of many troublesome polyatomic ions such as ArO⁺, ArN⁺, Ar₂ ⁺, ClO⁺, and ArCl⁺. The signals from refractory metal oxide ions are ≈ 1% of the corresponding metal ion signals, which is typical of most ICP-MS devices. Grounding the first electrode of the ion lens greatly reduces the severity of matrix effects to <- 20% loss in signal for Co⁺, Y⁺, or Cs⁺ in the presence of 10 mM Sr, Tm, or Pb. This latter lens setting causes only a modest loss (30%) in sensitivity for analyte elements compared to the best sensitivity obtainable by biasing the first lens. Alternatively, matrix effects can also be mitigated by readjusting the voltage applied to the first lens with the matrix present.     

Highly selective fluorescent recognition of Zn2+ based on naphthalene macrocyclic derivative

A new macrocyclic chemosensor containing two naphthalene fluorophores has been synthesized. The fluorescent properties of this receptor has been studied in the presence of various metal ions such as Na⁺, Ag⁺, Cr³⁺, Mn²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺ and Pb²⁺. When increasing concentrations of Zn²⁺ ions were introduced, the emission of L was drastically increased (EFE = 4.34). This special change was not observed when other metal ions were used; such highly selective fluorescent response indicates that this receptor can easily discriminate Zn²⁺ ions from other similar species. Model calculations at DFT level further suggest the possible interaction mode, and relatively steric position between the host and guest also influence the optical response.     

ESI‐MS studies of the non‐covalent interactions between biologically important metal ions and N‐sulfonylcytosine derivatives

The aim of this report is to present the electrospray ionization mass spectrometry results of the non‐covalent interaction of two biologically active ligands, N‐1 ‐ (p‐toluenesulfonyl)cytosine, 1‐TsC, 1 and N‐1 ‐ methanesulfonylcytosine, 1‐MsC, 2 and their Cu(II) complexes Cu(1‐TsC‐N3)₂Cl₂, 3 and Cu(1‐MsC‐N3)₂Cl₂ and 4 with biologically important cations: Na⁺, K⁺, Ca²⁺, Mg²⁺ and Zn²⁺. The formation of various complex metal ions was observed. The alkali metals Na⁺ and K⁺ formed clusters because of electrostatic interactions. Ca²⁺ and Mg²⁺ salts produced the tris ligand and mixed ligand complexes. The interaction of Zn²⁺ with 1–4 produced monometal and dimetal Zn²⁺ complexes as a result of the affinity of Zn²⁺ ions toward both O and N atoms. Copyright © 2016 John Wiley & Sons, Ltd.     

High resolution studies of the origins of polyatomic ions in inductively coupled plasma-mass spectrometry,Part I. Identification methods and effects of neutral gas density assumptions,extraction voltage,and cone material

Common polyatomic ions (ArO⁺, NO⁺, H₂O⁺, H₃O⁺, Ar₂⁺, ArN⁺, OH⁺, ArH⁺, O₂⁺) in inductively coupled plasma-mass spectrometry (ICP-MS) are identified using high mass resolution and studied using kinetic gas temperatures (T_gas) determined from a dissociation reaction approach. Methods for making accurate mass measurements, confirming ion identifications, and correcting for mass bias are discussed. The effects of sampler and skimmer cone composition and extraction voltage on polyatomic ion formation are also explored. Neutral species densities at several locations in the extraction interface are estimated and the corresponding effects of the T_gas value are calculated. The results provide information about the origins of background ions and indicate possible locations for their formation or removal.     

Probing the interaction of alkali and transition metal ions with bradykinin and its des-arginine derivatives via matrix-assisted laser desorption/ionization and postsource decay mass spectrometry

The complexes of the peptides (Pep) bradykinin (RPPGFSPFR), des-Arg¹-bradykinin, and des-Arg⁹-bradykinin with the metal (M) ions Na⁺, K⁺, Cs⁺, Cu⁺, Ag⁺, Co²⁺, Ni²⁺, and Zn²⁺ are generated in the gas phase by matrix-assisted laser desorption/ionization and the structures of the corresponding [Pep + M⁺]⁺ or [Pep − H⁺ + M²⁺]⁺ cations are probed by postsource decay (PSD) mass spectrometry. The PSD spectra depend significantly on the metal ion attached; moreover, the various metal ions respond differently to the presence or absence of a basic arginine residue. The Na⁺ and K⁺ adducts of all three peptides mainly produce N-terminal sequence ions upon PSD; the fragments observed point out that these metal ions are anchored by the PPGF segment and not the arginine residue(s). In contrast, the adducts of Cu⁺ and Ag⁺ show a strong dependence on the position of Arg; complexes of des-Arg¹-Pep (which contains a C-terminal Arg) produce primarily y_n ions whereas those of des-Arg⁹-Pep generate exclusively a_n and b_n ions. These trends are consistent with Cu⁺ ligation by Arg’s guanidine group. The [Pep + Cs⁺]⁺ ions mainly yield Cs⁺; a second significant fragmentation occurs only if a C-terminal arginine is present and involves elimination of this arginine’s side chain plus water. This reaction is rationalized through a salt bridge mechanism. The most prominent PSD products from [Pep − H⁺ + Co²⁺]⁺ and [Pep − H⁺ + Ni²⁺]⁺ contain at least one phenylalanine residue, revealing a marked preference for these divalent metal ions to bind to aromatic rings; the fragmentation patterns of the complexes further suggest that Co²⁺ and Ni²⁺ bind to deprotonated amide nitrogens. The coordination chemistry of Zn²⁺ combines features found with the divalent Co²⁺/Ni²⁺ as well as the monovalent Cu⁺/Ag⁺ transition metal ions. Generally, the structure and fragmentation behavior of each complex reflects the intrinsic coordination preferences of the corresponding metal ion.     

Selective transport of zinc and copper ions by synthetic ionophores using liquid membrane technology

This work highlights the role of synthetic carrier (ionophore) in the separation of heavy metal ions. A new series of ionophores; 4,4′-nitrophenyl-azo-O,O′-phenyl-3,6,9-trioxaundecane-1,10-dioate (R₁), bis[4,4′nitro-phenylazo-naphthyl-(2,2-dioxydiethylether)] (R₂) 1,8-bis-(2-naphthyloxy)-3,6-dioxaoctane (R₃), 1,11-bis-(2-naphthyloxy)-3,6,9-trioxaunde-cane (R₄), 1,5-bis-(2-naphthyloxy)-3-oxa-pentane (R₅) have been synthesized and used as extractant as well as carrier for the transport of various metal ions (Na⁺, K⁺, Mg²⁺, Ni²⁺, Cu²⁺ and Zn²⁺) through liquid membranes. Effect of various parameters such as metal ion concentration, ionophore concentration, liquid–liquid extraction, back extraction, comparison of transport efficiency of BLM and SLM and different membrane support (hen’s egg shell and PTFE) have been studied. In BLM ionophores (R₂–R₅) transport Zn⁺ at greater extent and the observed trend for the transport of Zn²⁺ is R₂?>?R₄?>?R₃?>?R₅ respectively. Further transport efficiency is increased in SLM. In egg shell membrane ionophores (R₂–R₅) transport Zn⁺ due to their non-cyclic structure and pseudo cavity formation while ionophore R₁ transports Cu²⁺ ions at greater extent due to its cyclic structure and cavity size. Among the membrane support used egg shell membrane is found best for the transport of zinc ions because of its hydrophobic nature and exhibits electrostatic interactions between positively charged zinc ions and –COOH group of egg shell membrane. Thus structure of ionophores, hydrophobicity and porosity of the membrane support plays important role in separation of metal ions.     

Gas-Phase Chemistry of Ti+ to Zn+ with Butyl Isothiocyanate

Using a complete set of ²H-labeled isotopomers, the gas-phase reactions of Ti⁺ to Zn⁺ with butyl isothio-cyanate are studied. The main product for most of the metal ions is MHNCS⁺ formed by an ion/dipole mechanism. Exceptions are Cr⁺, which yields significant amounts of H₂ and H₂S loss, Mn⁺, which is the only ion that does not form MHNCS⁺ at all but produces mainly C₂H₄ and C₃H₆, and Zn⁺, which predominantly reacts by charge transfer.     

Synthesis and ion-exchange properties of zirconium antimonate

Samples of zirconium antimonate have been prepared under varying conditions of precipitation. Their properties, composition, and ion-exchange behaviour are reported. The 1g K_d vs. pH curves are given for Rb⁺, Cs⁺, Zn²⁺, Ca²⁺ and Tl³⁺ ions. The distribution coefficients of 26 metal ions have been measured and several separations of analytical and radiochemical importance achieved.     

Na+/K+-ATPase: Activity and inhibition

The aim of the study was to give an overview of the mechanism of inhibition of Na⁺/K⁺-ATPase activity induced by some specific and non specific inhibitors. For this purpose, the effects of some ouabain like compounds (digoxin, gitoxin), noble metals complexes ([PtCl₂DMSO₂], [AuCl₄]⁻, [PdCl₄]²⁻, [PdCl(dien)]⁺, [PdCl(Me₄dien)]⁺), transition metal ions (Cu²⁺, Zn²⁺, Fe²⁺, Co²⁺), and heavy metal ions (Hg²⁺, Pb²⁺, Cd²⁺) on the activity of Na⁺/K⁺-ATPase from rat synaptic plasma membranes (SPM), porcine cerebral cortex and human erythrocytes were discussed. The article is published in the original.     

Chromium antimonate as an ion-exchanger

Summary Chromium antimonate has been synthesised under varying conditions of precipitation and the cation-exchange properties of the various samples are reported. Systematic study has resulted in a product suitable for column operations. The effect of equilibration time, concentration of the electrolyte, size and charge of the ion and drying temperature on exchange capacity is reported. The chemical stability and regeneration power of the sample are also investigated. The plots of log K_d against pH for Rb⁺, Cs⁺, Tl⁺, Ca²⁺, Zn²⁺, and Tl³⁺ ions suggest a predominently ion-exchange mechanism in the case of Rb⁺ and Cs⁺ ions. K_d values of 27 metal ions have been determined and some chromatographic separations of analytical and radiochemical importance based on them have been achieved on chromium antimonate columns.Presented at the Annual Convention of Chemists (India), Roorkee, December 1975.     

Direct Determination of Gold in Rock Samples Using Collision Cell Quadrupole ICP-MS

This study investigated the determination of Au in rock samples using collision cell quadrupole inductively coupled plasma mass spectrometry (ICP-MS). It is essential to remove various interferents using a collision cell because polyatomic ions such as ¹⁸¹Ta¹⁶O⁺ and ¹⁸⁰Hf¹⁶O¹H⁺ can interfere with the direct determination of monoisotopic ¹⁹⁷Au when using ICP-MS. The addition of oxygen as a reaction gas removed isobaric interferents by transforming TaO⁺ and HfOH⁺ to TaO₂⁺, TaO₃⁺, and HfO₂H⁺, HfO₃H⁺, respectively, in the cell without significant Au⁺ loss. The ion kinetic energy effect (IKEE) due to the potential difference between the plasma and the hexapole affected the reactions in the cell. Au and interfering ions were very sensitive to cell bias voltage (Vc) at constant plasma potential (Vp) and quadrupole bias voltage (Vq). Under the condition of hot plasma, the transmission of ions was promoted, and the maximum Au signal intensity was 50% greater than under normal conditions. At Vc > 7 V, TaO⁺ ions were removed to background level. Optimized conditions for real sample analysis were obtained by introducing He as an additional collision gas in hot plasma. TaO⁺ ions were removed to background level at He flow rates above 0.6 mL min⁻¹, and the Au signal remained high. The detection limit (three times the standard deviation of the blank) of this method was 3.06 pg g⁻¹. The results for reference materials (STM-1 and DGPM-1) and spiked samples showed good agreement between specified and measured concentrations.     

Efficient ensemble and IDA system based on the metal binding motif for highly sensitive and selective detection and determination of carbonate and citrate ions

Herein, we have reported a novel naked eye detection method which is based on the analyte competing for a metal reporter with a chromogenic indicator. This assay is based on the highly specific interaction between the anions and the metal ions and murexide (Mure) probe in a competition assay format. The resulting high sensitivity and selectivity for citrate and carbonate were achieved by changing the metal ions. The indicator is set free due to its displacement from the Mure/Cu²⁺ complex by citrate (Cit³ˉ) and the change in absorbance may be due to the further complexation of carbonate (CO₃²ˉ) with the additional coordination sites present in the zinc atom of Mure/Zn²⁺ complex. The dye-based ensemble systems are expected to be a potential and practical way for the detection of nanomolar concentrations of analytes in 100% aqueous solutions. The chemosensor enabled sensitive and selective detection of Cit³ˉ and CO₃²ˉ with detection limits of 19.1 and 9.4 nmol L^?1, respectively. These systems are simple in design, fast in operation and are more promising than previous methods. This novel method eliminated the need for separation processes, chemical modifications, organic cosolvents, and sophisticated instrumentations. Chiefly, the protocol offers high selectivity for the determination of Cit³ˉ and CO₃²ˉ among anions found in human urine samples in the presence of some biological species, including K⁺, Mg²⁺, Fe³⁺, Ca²⁺, Zn²⁺, Na⁺, glucose, urea, uric acid and ascorbic acid. Further, NAND and INHIBIT molecular logic gates were obtained using chemical inputs and UV–Vis absorbance signal as the output.     

Study of ion transport processes in soils by radioabsorption method

The transport processes of Na⁺, K⁺, Cs⁺, Ca²⁺, Zn²⁺, Mn²⁺, Fe³⁺ and HPO ₄ ²⁻ ions were studied in soils by radioabsorption method. The effective diffusion coefficients varied in the interval of 10⁻¹⁶–10⁻¹⁰ m²s⁻¹. The effective diffusion coefficient of Ca²⁺, Co²⁺, Zn²⁺ and Fe³⁺ ions increased by several orders of magnitude as a result of the addition of a complex forming agent.     

Speciation analysis of mercury contaminants in water samples by RP-HPLC after solid phase extraction on modified C18 extraction disks with 1,3-bis(2-cyanobenzene)triazene

A highly sensitive and accurate method for preconcentration and determination of ultra trace amounts of inorganic mercury and organomercury compounds in different water samples is proposed. The preconcentration is achieved using octadecyl silica (C₁₈) extraction disks modified with 1,3-bis(2-cyanobenzene)triazene (CBT). The retained analytes as their triazenide complexes on the solid phase was eluted with 10 ml acetonitrile and measured by reversed-phase high-performance liquid chromatography (RP-HPLC). Type and amount of eluent, pH, amount of CBT, flow rates of sample solution and eluent have been optimized in order to obtain quantitative recovery of the analytes. The effect of interfering ions, such as Cu²⁺, Mn²⁺, Fe²⁺, Al³⁺, Zn²⁺, Cd²⁺, Ca²⁺, Mg²⁺, Ba²⁺, Pb²⁺, K⁺ and Na⁺ usually present in water samples on the recovery of the analytes has also been investigated. The enrichment factor of 100 was obtained for all mercury species and the analytical detection limits of phenylmercury, methylmercury and Hg²⁺ were found as 0.8, 1.0 and 1.3 ng l^− 1, respectively. Stability of mercury species after extraction on the modified disks was studied and the results showed that complexes collected on the disks were stable for at least 5 days. The proposed method has been applied to the quantitative determination of mercury species in natural and synthetic water samples with recoveries more than 90%.     

Brushite (Ca,M)HPO4, 2H2O doping with bioactive ions (M = Mg2+, Sr2+, Zn2+, Cu2+, and Ag+): a new path to functional biomaterials?

Dicalcium phosphate dihydrate, DCPD (CaHPO₄·2H₂O), brushite, is an important calcium phosphate compound encountered in mineralized tissues and used in medicine, especially in bone cement formulations. However, the use of DCPD as direct implantable biomaterial has not received dedicated attention. In addition, the possibility to dope DCPD with biologically active ions to modulate its performances was not systematically explored. We have investigated in depth the doping of DCPD with Mg²⁺, Sr²⁺, Zn²⁺, Cu²⁺, and Ag⁺ ions. Clear modifications in terms of chemical composition, particle size, pore distribution, crystal morphology, and affinity for water were pointed out. Then, the samples were cultured with human adipose-derived stem cells to explore cytotoxicity and proliferation. Various behaviors were noticed dependent on the incorporated metal ions. Such DCPD compounds associated with bioactive metal ions, and particularly Ag⁺ and Zn²⁺, appear promising as a new family of reactive materials for use, as such or in combination, in bone-related applications.     

Running buffers for determination of chromium(VI)/(III), cobalt(II) and zinc(II) in complex matrices by capillary electrophoresis with contactless conductivity detection

Complex matrices and rather high acidity in environmental samples are often the impelling challenges for the used running buffers of capillary electrophoresis. Twelve binary acid-base buffers were evaluated for separation of Cr(VI)/Cr(III), Co²⁺ and Zn²⁺ in a sample containing various salts by capillary electrophoresis with contactless conductivity detector. The malic acid (MA) systems including MA-His (histidine), MA-Arg (arginine) and MA-Tris (tris(hydroxymethyl)aminomethane) were selected as the candidates with powerful separation efficiency and good response sensitivity. In the MA-Tris buffer, optimization were further carried out in terms of the pH value and the concentration of MA, and the optimal conditions were obtained as 6 mM MA-Tris and 2 mM 18-crown-6 at pH 3.5. Furthermore, a real application was demonstrated by analyzing the plating rinse water (pH 0.8), in which the Ca²⁺, Na⁺, Cr(VI)/Cr(III), Co²⁺ and Zn²⁺ were all detected by adjusting at pH 3.5 with 5% (v/v) diluent ammonia. Both the cations, e.g., K⁺, Ca²⁺, Na⁺, Mg²⁺, and the common high concentration anions in the sample, e.g., Cl⁻, SO₄²⁻ and NO₃⁻ did not cause any disturbance to the concerned analytes.     

Application of a hexapole collision and reaction cell in ICP-MS Part I: Instrumental aspects and operational optimization

The application of an ion-guiding buffer gas-filled hexapole collision and reaction cell in ICP-MS has been studied in order to give a preliminary performance characterization of a new instrument providing this feature for increasing the ion yield and decreasing contributions from Ar induced interfering molecular ions. As buffer gas He was used while H₂ served as reaction gas. Addition of the latter can be an effective means for reduction of typical argon induced polyatomic ions (Ar⁺, ArO⁺, Ar₂ ⁺) by orders of magnitude owing to gas phase reactions. Molecular interferences generated in the cell can be suppressed by a retarding electric field established by a dc hexapole bias potential of –2 V.     

Application of a hexapole collision and reaction cell in ICP-MS Part I: Instrumental aspects and operational optimization

The application of an ion-guiding buffer gas-filled hexapole collision and reaction cell in ICP-MS has been studied in order to give a preliminary performance characterization of a new instrument providing this feature for increasing the ion yield and decreasing contributions from Ar induced interfering molecular ions. As buffer gas He was used while H₂ served as reaction gas. Addition of the latter can be an effective means for reduction of typical argon induced polyatomic ions (Ar⁺, ArO⁺, Ar₂ ⁺) by orders of magnitude owing to gas phase reactions. Molecular interferences generated in the cell can be suppressed by a retarding electric field established by a dc hexapole bias potential of –2 V. Received: 10 May 1999 / Revised: 4 June 1999 / Accepted: 12 June 1999     

Synthetic inorganic ion-exchange materials

The change in selectivities by thermal treatment was studied on crystalline (C-SbA) and amorphous (A-SbA) antimonic(V) acids. The equilibrium distribution coefficients (K_d) of Na⁺ and K⁺ ions in HNO₃ solution showed a maximum on the C-SbA heated at 330 °C. An inverse relationship was noticed between the changes in K_d values and in the lattice constants for the heated C-SbA. A-SbA heated at 20–500°C showed two steps of time dependence of adsorption for Na⁺, while a maximum for K⁺. This behavior can be explained in terms of the transformation from amorphous material to C-SbA.