Diminishing the Gap Between GC-Selective and Universal Detection by Capped Pd Nanoparticles

A simple Pd²⁺ ligand exchanger was prepared and applied for isolation of aromatic heterocyclic sulfur compounds (S-PAHs) from petroleum condensate oil. The ligand exhibited excellent isolation efficiency and selectivity towards S-PAHs. The chromatograms of pre-isolated S-PAHs recorded by universal flame ionization (FID) and mass spectrum (MS) detections are similar to selective sulfur atomic emission detector chromatograms, indicated from traces or absence of hydrocarbons in FID and MS chromatograms. Nitrogen adsorption, electronic microscope, and X-ray diffraction techniques were employed to confirm the formation of capped Pd²⁺ nanoparticle dispersion within the silica framework. The results obtained revealed that Pd²⁺ ions exist as dispersed capped nanoparticles sized between 69 and 79 nm that can be rationalized for their enhanced isolation selectivity towards the S-PAH fraction of petroleum condensate oil.

     

自动化质谱图解卷积和鉴定系统用于鉴定含痕量杂原子的石油馏分（英文）

Here we present a simple yet effective gas chromatography-mass spectrometry (GC-MS) identification approach for the detection of heteroatom-containing compounds (HACCs) in petroleum fractions. The MS/AMDIS (Automated Mass Spectral Deconvolution and Identification System) program was used to identify parts per million (ppm) HACC concentrations in petroleum fractions in place of traditional techniques (extraction and standard injection). Polycyclic aromatic sulfur heterocycles (S-PAHs) were used as model compounds to confirm the validity of the AMDIS identifiers, which were compared with extracted results using the off-line X-calibur software. AMDIS was able to identify ppm concentrations of S-PAHs in oil condensate. There was good agreement between experimental and AMDIS identification results for S-PAHs in oil condensate. AMDIS was also used to detect nitrogen-containing compounds (NCCs) and alkylphenols in oil condensate. Our results confirmed the presence of 2-methylbenzothiazole, carbazole, and 2,4-ditertbutyl phenol. In a crude oil sample, AMDIS identification of m/z=191 biomarkers was consistent with empirical results. Therefore, AMDIS can help to reduce the number of experimental steps in identification protocols.     

新型包覆Pb纳米粒子液相色谱-串联质谱法用于鉴定沙特阿拉伯原油中的含氧化合物（英文）

Saudi Arabian crude oil is a super complex mixture and,up to now,there has been little research into its heteroatom-containing compounds.First,oxygenated compounds(OCs)were isolated from Saudi Arabian oil using a Pd nanoparticle exchange complex,which formed between the nano-Pds and the oxygenated ligands.Normally,polycyclic aromatic sulphur heterocycles(S-PAHs)are separated from petroleum oil via the same method.The obtained results reveal that all the OC formulations with S-PAHs can be separated from the pre-isolated aromatic fraction of crude oil via this approach.S-PAHs are mixtures of benzothiophene and dibenzothiophene congeners.The isolated OCs are composed mainly of hydroxyl compounds.The liquid chromatography(LC)/electrospray ionization(ESI)in positive ion mode ESI(+)/tandem mass spectrometry(MS/MS)technique was used to assign the molecular weight distribution and identify the isolated OCs.The LC/ESI(+)-MS/MS technique differentiates S-PAHs and OCs using protonated ions.Thus,LC/ESI(+)-MS/MS can be used to assign molecular weight distributions for both the groups as a single mixture.MS/MS in precursor ion mode was used for the immediate identification of the target S or O analytes.     

新型包覆Pd纳米粒子液相色谱-串联质谱法用于鉴定沙特阿拉伯原油中的含氧化合物(英文)

Saudi Arabian crude oil is a super complex mixture and,up to now,there has been little research into its heteroatom-containing compounds.First,oxygenated compounds(OCs)were isolated from Saudi Arabian oil using a Pd nanoparticle exchange complex,which formed between the nano-Pds and the oxygenated ligands.Normally,polycyclic aromatic sulphur heterocycles(S-PAHs)are separated from petroleum oil via the same method.The obtained results reveal that all the OC formulations with S-PAHs can be separated from the pre-isolated aromatic fraction of crude oil via this approach.S-PAHs are mixtures of benzothiophene and dibenzothiophene congeners.The isolated OCs are composed mainly of hydroxyl compounds.The liquid chromatography(LC)/electrospray ionization(ESI)in positive ion mode ESI(+)/tandem mass spectrometry(MS/MS)technique was used to assign the molecular weight distribution and identify the isolated OCs.The LC/ESI(+)-MS/MS technique differentiates S-PAHs and OCs using protonated ions.Thus,LC/ESI(+)-MS/MS can be used to assign molecular weight distributions for both the groups as a single mixture.MS/MS in precursor ion mode was used for the immediate identification of the target S or O analytes.     

Synthesis,spectroscopic characterization and study the effect of gamma irradiation on VO2+, Mn2+, Zn2+, Ru3+, Pd2+, Ag+ and Hg2+ complexes and antibacterial activities

Novel complexes of VO²⁺, Mn²⁺, Zn²⁺, Ru³⁺, Pd²⁺, Ag⁺ and Hg²⁺ have been prepared by reacting their metal salts with ligand, named (4-(4-chlorophenyl)-1-(2-(phenylamino) acetyl) thiosemicarbazone). Study of synthesized metal complexes was confirmed by different analytical and spectral techniques (¹H NMR, MS, FT-IR, UV–Vis, EPR and Powder X-ray diffraction), thermogravimetric studies as well as molecular modeling. FT-IR spectra showed that the compound behave as neutral or monobasic tetradentate. In case of complexes of Mn²⁺, Zn²⁺, Ag⁺ and VO²⁺, through (N2H), (CO) or (CO) groups. While, the ligand behave as neutral bidentate in case of complexes with Pd²⁺ and Hg²⁺. X-ray diffraction pattern of Mn²⁺, Pd²⁺ and Ag⁺ complexes before and after irradiation are recorded. XRD studies exhibited that decrease in the crystalline size of sample Mn²⁺ as compared of samples Ag⁺ and Pd²⁺ upon irradiation and irradiation influenced the crystallinity of the complexes. The possible structures of the ligand, Mn²⁺, Pd²⁺ and Hg²⁺complexes have been computed by means of the molecular mechanic calculations using the hyper chem. 8.03 molecular modeling program. The bond length, bond angle, HOMO, LUMO and dipole moment have been studied to verify the geometry of Mn²⁺, Pd²⁺ and Hg²⁺ complexes. The effect of gamma irradiation was investigated by recording the new results of pervious spectroscopic techniques and other measurements. Thermal studies of these chelates before and after γ-irradiation showed that the complexes after γ-irradiation were more thermally stable than before γ-irradiation. The compound and its metal complexes have been experienced for their inhibitory outcome on the growth of microorganisms against gram positive and gram negative. The results proved that the complexes B₁–B₇ have potent antibacterial activity as compared to that of ligand.     

NMR-Spektroskopische Untersuchungen der kinetischen Limitierung der Kationenselektivität eines cadmiumselektiven Ionophors

NMR Studies of the Kinetic Limitation of Cation Selectivity of a Cadmium-Selective Ionophore The Cd²⁺-selective ionophore N,N,N′,N′-tetrabutyl-3, 6-dioxaoctanedithioamide (1) looses its capability to induce cation selectivity in solvent polymeric membranes if these are contacted with Cu²⁺, Pd²⁺, Pt²⁺, Ag⁺ and Hg²⁺. For systems with a free energy of activation of the ligand exchange reaction of more than about 65 kJ mol^?1 (in acetonitrile) the cation complexes of the ionophore act as anion exchangers (Pt²⁺, Pd²⁺). Below about 45 kJ mol^?1 cation permselectivity is observed (Zn²⁺, Cd²⁺). Ag⁺ and Hg²⁺ induce a decomposition of the ionophore.     

Ion Mobility-Mass Spectrometry Study of Folded Ubiquitin Conformers Induced By Treatment with <Emphasis Type="Italic">cis</Emphasis>-[Pd(en)(H<Subscript>2</Subscript>O)<Subscript>2</Subscript>]<Superscript>2+</Superscript>

Ion mobility-mass spectrometry is used to study the new conformers of bovine ubiquitin (Ub) and the palladium(II) binding sites after the incubation with cis-[Pd(en)(H₂O)₂]²⁺ where en = ethylenediamine. Palladium(II) complexes are potentially useful proteomic reagents because they selectively bind to the side groups of methionine and histidine and hydrolytically cleave the peptide bond. Incubating 1.0 mM solution of Ub with 10.0 molar excess of cis-[Pd(en)(H₂O)₂]²⁺ results with one to four Pd²⁺ or Pd(en)²⁺ being attached to intact Ub and two conformer families at each of the 4+ to 11+ charge states. The 4+ and 5+ species exhibit a compact form, which is also observed in untreated Ub, and a new highly folded conformer. The 6+ to 10+ exhibit an elongated form, also observed in Ub, and a new partially folded conformer. The new conformers are shown to be more stable if they contain at least one Pd²⁺, rather than all Pd(en)²⁺. IM-MS/MS of [UbPd₂en+5H]⁹⁺ shows that both the partially folded and elongated conformers first lose the en ligand, followed by dissociating into product ions that indicate that Met1, Glu51/Asp52, His68, and Glu16 are binding sites for Pd²⁺. These results suggest that Pd²⁺ is simultaneously binding to multiple side groups across different regions of Ub. This type of sequestering of Pd²⁺ probably reduces the efficiency of Pd²⁺ ions to selectively cleave Ub because it prevents Pd²⁺ anchoring to only Met or His and to an adjacent backbone amide nitrogen and forming the “activated complex” necessary for specific peptide bond cleavage.     

Self‐assembly and Cycling of a Three‐state PdxLy Metallosupramolecular System

The use of stimuli to induce reversible structural transformations in metallosupramolecular systems is of keen interest to chemists seeking to mimic the way that Nature effects conformational changes in biological machinery. While a wide array of stimuli have been deployed towards this end, stoichiometric changes have only been explored in a handful of examples. Furthermore, switching has generally been between only two distinct states. Here we use a simple 2‐(1‐(pyridine‐4‐methyl)‐1H‐1,2,3‐triazol‐4‐yl)pyridine “click” ligand in combination with Pd^II in various stoichiometries and concentrations to quantitatively access and cycle between three distinct species: a [PdL₂]²⁺ monomer, a [Pd₂L₂]⁴⁺ dimer, and a [Pd₉L₁₂]¹⁸⁺ cage.     

A fluorescent probe for the discrimination of oxidation states of palladium

Palladium-based catalysts are widely used in pharmaceutical industries, which can sometimes cause palladium contamination in pharmaceutical drug manufacture. It is important to separately quantify the different oxidation states of palladium (Pd⁰ and Pd²⁺) in pharmaceuticals as they react with scavengers differently. Although palladium sensors have been under intense investigation, oxidation state differentiators are very rare. Here, we report a simple porphyrin–coumarin conjugate, PPIX-L2, that can selectively discriminate between the oxidation states of palladium. The reaction of PPIX-L2 with Pd⁰ showed a 24-fold fluorescence increase of the coumarin emission, meanwhile, the presence of Pd²⁺ led to a 98% quenching of the porphyrin emission. Fluorescent responses of PPIX-L2 towards Pd⁰ and Pd²⁺ are specific, and its sensitivity towards both palladium species is significantly increased with a detection limit of 75 nM and 382 nM for Pd⁰ and Pd²⁺ respectively.

A simple porphyrin–coumarin conjugate PPIX-L2 was developed for the discrimination of different oxidation states of palladium (Pd⁰ and Pd²⁺), and with a significantly improved sensitivity.     

Synthesis of 8‐hydroxyquinolium chloroacetate and synthesis of complexes derived from 8‐hydroxyquinoline,and characterization,density functional theory and biological studies

8‐Hydroxyquinolium chloroacetate ( L¹ ) was synthesized and characterized. The results suggest that L¹ loses ethyl chloroacetate ion on coordination at low pH (2–5) and consequently it behaves as 8‐hydoxyquinoline ( L² ). Cu²⁺, Co²⁺, Pt⁴⁺, Pd²⁺, Au³⁺, Ag⁺ and Nd³⁺ complexes derived from L² have been synthesized and characterized using spectral, magnetic and thermal measurements. L² acts as a neutral bidentate ligand in the case of Cu²⁺, Co²⁺, Pt⁴⁺, Pd²⁺ and Nd³⁺ complexes and as a mononegative bidentate ligand in the case of Au³⁺ and Ag⁺ complexes. Octahedral geometry is proposed for Cu²⁺, Co²⁺ (grey) and Pt⁴⁺ complexes and square‐planar for Co²⁺ (green), Pd²⁺ and Au³⁺ complexes. The bond lengths, bond angles, chemical reactivities, binding energies and dipole moments for all compounds were evaluated using density functional theory and molecular electrostatic potential for L¹ . Superoxide dismutase radical scavenger‐like activity and cytotoxic activity of the complexes towards HepG2 liver cancer cells has been screened. Cytotoxicity measurements show that Ag⁺ and Pd²⁺ complexes have the highest cytotoxic activity while L¹ , Cu²⁺, Co²⁺ (grey), Co²⁺ (green), Pt⁴⁺ and Nd³⁺ complexes have no cytotoxic activity. Copyright © 2015 John Wiley & Sons, Ltd.     

The characterization and quantitation of sulfur-containing compounds in (heavy) middle distillates by LC-GC-FID-SCD

A modified sulfur chemiluniinescence detector (SCO) has been interfaced to a HPLC-HRGC hyphenated system. This combination enables the full characterization and quantitation of the sulfur containing compounds in (heavy) middle distillate oil fractions (boiling range 150–450°C). The system is suited to identify and determine the various groups of orgaiio-sulfur structures such as: thiols + sulfides + thiophencs, benzothiophenes, dibenzothiophenes and benzo-naphthothiophenes. Within these groups a separation according to boiling point is accomplished. Therefore it allows the separation, identification and quantitation of a number of individual species, especially those which are refractory to hydrodesulfu-rization (HDS), such as 3-methyl-benzothiophene, 4-methyl-dibenzothiophene and -J,6-dimethyl-dibenzothiophene. The analysis of these groups and specific compounds is the key in understanding the kinetics of the chemistry involved in HDS. The complete instrumental set-up is fully automated by computer control. To suppress possible interferences and quenching of the sulfur response of the SCL from (large amounts of) hydrocarbons, it is aligned above the adapted flame ionization detector (FID) of the GC. This renders a sensitivity of the SCO for sulfur of 2 pg. s^?1, which corresponds to a minimum detectable level for individual sulfur species in oil fractions for the complete system of 1 ppm (mg. kg^?1) sulfur. Its linear dynamic range exceeds 10⁵, which means that also untreated, high sulfur containing feedstocks can be analyzed directly. The selectivity of sulfur to carbon of the modified SCO exceeds 10⁶. A number of HDS feedstocks and desulfurized products of different desulfurization levels have been analyzed with the system. From the analysis results the behavior of the refractory compounds in HDS can now be followed closely.     

Development and evaluation of gas and liquid chromatographic methods for the analysis of fatty amines

In contrast to the plethora of publications on the separation of fatty acids, analogous studies involving fatty amines are scarce. A recently introduced ionic‐liquid‐based capillary column for GC was used to separate trifluoroacetylated fatty amines focusing on the analysis of a commercial sample. Using the ionic liquid column (isothermal mode at 200°C) it was possible to separate linear primary fatty amines from C₁₂ to C₂₂ chain length in less 25 min with MS identification. The log of the amine retention factors are linearly related to the alkyl chain length with a methylene selectivity of 0.117 kcal/mol for the saturated amines and 0.128 kcal/mol for the mono‐unsaturated amines. The sp² selectivity for unsaturated fatty amines also could be calculated as 0.107 kcal/mol for the ionic liquid column. The commercial sample was quantified by GC with flame ionization detection (FID). An LC method also was developed with a reversed phase gradient separation using acetonitrile/formate buffer mobile phases and ESI‐MS detection. Native amines could be detected and identified by their single ion monitoring chromatograms even when partial coelution was observed. The analysis of the commercial sample returned results coherent with those obtained by GC–FID and with the manufacturer's data.     

Pd2+-Initiated Formic Acid Decomposition: Plausible Pathways for C-H Activation of Formate

Formic acid (HCOOH, FA) has long been considered as a promising hydrogen-storage material due to its efficient hydrogen release under mild conditions. In this work, FA decomposes to generate CO₂ and H₂ selectively in the presence of aqueous Pd²⁺ complex solutions at 333 K. Pd(NO₃)₂ was the most effective in generating H₂ among various Pd²⁺ complexes explored. Pd²⁺ complexes were in situ reduced to Pd⁰ species by the mixture of FA and sodium formate (SF) during the course of the reaction. Since C−H activation reaction of Pd²⁺-bound formate is occurred for both Pd²⁺ reduction and H₂/CO₂ gas generation, FA decomposition pathways using several Pd²⁺ species were explored using density functional theory (DFT) calculations. Rotation of formate bound to Pd²⁺, β-hydride elimination, and subsequent CO₂ and H₂ elimination by formic acid were examined, providing different energies for rate determining step depending on the ligand electronics and geometries coordinated to the Pd²⁺ complexes. Finally, Pd²⁺ reduction toward Pd⁰ pathways were explored computationally either by generated H₂ or reductive elimination of CO₂ and H₂ gas.     

A simple and highly selective fluorescent sensor for palladium based on benzofuran-2-boronic acid

Benzofuran-2-boronic acid could be used as a fluorescent sensor for the detection of Pd²⁺ because it was rapidly converted to highly fluorescent derivative after mixing with Pd²⁺ under basic condition at room temperature. We found that dimerization of benzofuran was occurred to form fluorescent derivative by the catalytic activity of palladium. The fluorescence intensity at 360 nm increased with increasing the concentration of Pd²⁺. The excellent selectivity for Pd²⁺ was demonstrated among other metal ions. Based on this findings, we successfully applied benzofuran-2-boronic acid to develop a microplate-based assay for high-throughput measurement of Pd²⁺. The detection limit (blank + 3SD) for Pd²⁺ of the proposed assay was 9.8 nM.     

Development of a species-specific isotope dilution GC-ICP-MS method for the determination of thiophene derivates in petroleum products

A species-specific isotope dilution technique for accurate determination of sulfur species in low- and high-boiling petroleum products was developed by coupling capillary gas chromatography with quadrupole ICP-MS (GC-ICP-IDMS). For the isotope dilution step ³⁴S-labeled thiophene, dibenzothiophene, and mixed dibenzothiophene/4-methyldibenzothiophene spike compounds were synthesized on the milligram scale from elemental ³⁴S-enriched sulfur. Thiophene was determined in gasoline, ‘sulfur-free’ gasoline, and naphtha. By analyzing reference material NIST SRM 2296, the accuracy of species-specific GC-ICP-IDMS was demonstrated by an excellent agreement with the certified value. The detection limit is always limited by the background noise of the isotope chromatograms and was determined for thiophene to be 7 pg absolute, which corresponds to 7 ng sulfur/g sample under the experimental conditions used. Dibenzothiophene and 4-methyldibenzothiophene were determined in different high-boiling petroleum products like gas oil, diesel fuel, and heating oil. In this case a large concentration range from about < 0.04 to more than 2,000 μg g⁻¹ was covered for both sulfur species. By parallel GC-ICP-MS and GC-EI-MS experiments (EI-MS electron impact ionization mass spectrometry) the substantial influence of co-eluting hydrocarbons on the ICP-MS sulfur signal was demonstrated, which can significantly affect results obtained by external calibration but not those by the isotope dilution technique.     

Extraction of thorium(IV) and europium(III) by a phosphorylated calix[4]arene in dichloromethane

Summary The extractive properties of 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis(diphenylphosphinoylmethoxy)calix[4]arene towards thorium(IV) and europium(III) ions are studied. The conventional log-log analysis of the extraction data reveals that the stoichiometry of the extracted species is 1 : 1 metal ion to ligand ratio for the two metals. The effects of ligand concentration, types of diluent and concentration of the salting-out agents are investigated and discussed. The selectivity of the ligand for thorium and europium ions versus Mn²⁺, Pb²⁺, Cd²⁺, Fe²⁺, Ni²⁺ and Co²⁺ is examined.     

Complexation of di-benzyloxy ether derivatives of calix[4]arene with alkali earth metal cations

The synthesis and complexing abilities of 26,28-bis-benzyloxy-25,27-dihydroxy-5,11,17,23-tetra-tertbutyl-calix[4]arene towards alkali earth metal ions Mg²⁺, Ca²⁺, Sr²⁺, and Ba²⁺ in a methanol-chloroform mixture have been evaluated at 25°C, using UV-Vis spectrophotometric techniques. The results showed that the ligand is capable to complex all alkali earth cations by 1:1 metal to ligand ratios. The selectivity presented considering the calculated stability constants are in the order Mg²⁺ > Ca²⁺ > Sr²⁺ > Ba²⁺ towards the ligand.     

Perylene diimide based ‘turn-on’ fluorescence sensor for detection of Pd in mixed aqueous media

A perylene diimide (PDI) based fluorescence chemosensor (PDI-1) for Pd²⁺ was prepared. PDI-1 showed a remarkable fluorescence enhancement (over 120-fold) in the presence of Pd²⁺ in mixed aqueous media with high selectivity and sensitivity. Moreover, the dramatically ‘off–on’ fluorescence response concomitantly induced the obvious color change from dark purple to brilliant pink, which could also be identified by naked eyes easily. The low limit for Pd²⁺ detection was found to be as small as 10⁻⁹ mol/L. Hence, PDI-1 is a highly promising fluorescent chemosensor for the direct determination of residual Pd²⁺ in chemical medicines and environment samples.     

Highly Sensitive and Fast‐Responsive Fluorescent Chemosensor for Palladium: Reversible Sensing and Visible Recovery

The well‐known rhodamine spiro‐lactam framework offers an ideal model for the development of fluorescence‐enhanced chemosensors through simple and convenient syntheses. Herein, we report a new tridentate PNO receptor, which was introduced into a rhodamine spiro‐lactam system to develop Pd²⁺‐chemosensor RPd4 , that displayed significantly improved sensing properties for palladium. Compound RPd4 shows a very fast response time (about 5 s), high sensitivity (5 nM ), and excellent specificity for Pd²⁺ ions over other PGE ions (Pt²⁺, Rh³⁺, and Ru³⁺). In addition, RPd4 displays quite different responses to different valence states of the Pd ions, that is, very fast response towards Pd²⁺ ions but slow response towards Pd⁰, which may provide us with a convenient method for the selective discrimination of Pd species in different valence states. According to proof‐of‐concept experiments, RPd4 has potential applications in Pd²⁺‐analysis in drug compounds, water, soil, and leaf samples. Owing to its good reversibility, RPd4 can also be used as a sensor material for the selective detection and visual recovery of trace Pd²⁺ ions in environmental samples.     

A New Tridentate Sulfur Receptor as a Highly Sensitive and Selective Fluorescent Sensor for Cu2+ Ions

The introduction of Lawesson′s reagent into a bis‐rhodamine spirolactam system afforded a new fluorescent sensor for Cu²⁺ ions, SRR , which contained a new tridentate sulfur ligand. SRR showed excellent specificity for Cu²⁺ ions over other cations (including Cu⁺, Hg²⁺, and Fe³⁺), very high sensitivity (10 nM ), and a rapid response time (3 min). The detection mechanism was investigated by ¹H NMR, ¹³C NMR, ³¹P NMR, and ESR spectroscopy, MS, and Gaussian calculations. Coordination of a Cu²⁺ ion to the tridentate sulfur ligand, which promotes ring‐opening of the rhodamine groups, followed by a spontaneous reduction reaction (Cu²⁺ into Cu⁺), has been proposed as the sensing mechanism.