Design and preparation of imprinted surface plasmon resonance (SPR) nanosensor for detection of Zn(II) ions

A novel Zn(II) ions imprinted poly (2-hydroxyethyl Methacrylate-N-methacryloyl-(L)-histidine methyl ester) poly(HEMAH) surface plasmon resonance (SPR) nanosensor were designed for detection of Zn(II) ions in aqueous solution and artificial plasma providing a low cost, rapid and reliable results compared to other techniques such as atomic absorption spectroscopy, inductively coupled plasma-mass spectrometer, X-ray fluorescence with synchrotron radiation. Zn(II) ions imprinted nanofilm on the SPR chip surface was synthesized by bulk polymerization. Characterization of Zn(II) ions imprinted nanosensor was performed by contact angle measurement, atomic force microscopy (AFM), ellipsometry and Fourier transform infrared spectroscopy-attenuated total reflection (FTIR-ATR). Designed nanosensor was applied for selective detection of Zn(II) ions in aqueous solution within the range of 0.5–1.0?µg/mL. The limit of detection (LOD) and limit of quantification (LOQ) were calculated as 0.19 and 0.64?ng/mL, respectively. Association kinetics analysis, Scatchard, Langmuir, Freundlich, Langmuir–Freundlich, Tempkin and Dubinin-Radushkevich isotherms were analyzed to the experimental data in order to identify the adsorption behavior. The selectivity of the SPR nanosensor was examined by using competitive metal ions such as Cd(II), Cu(II), Pb(II), and Fe(II). To evaluate the imprinting effect of Zn(II) ions imprinted (MIP) and non-imprinted (NIP) nanosensor was also prepared as the control. Repeatability of the response signal was tested by four times adsorption–desorption–regeneration cycle.     

Sulfur containing polymers.: Aromatic polydithiocarbonates and polythiocarbonates: synthesis and thermal properties

New polydithiocarbonates and polythiocarbonates were obtained by interfacial polymerization of bis(4-mercaptophenyl)methane, bis(4-mercaptophenyl)ether and bis(4-mercaptophenyl)sulfide with phosgene, bisphenol A bischloroformate and bisphenol A polycarbonate oligomers (-OH/-O-CO-Cl terminated). Polymerization process was carried out under interfacial conditions using a phase-transfer catalyst, as earlier described for the synthesis of polydithiocarbonates and polythiocarbonates from 2,2-bis(4-mercaptophenyl)propane. The structures of the polymers were examined by IR and NMR spectroscopies; their thermal properties were investigated by thermogravimetric analysis and differential scanning calorimetry. In particular, the effect of the substitution of one or both the ethereal oxygen atoms of the carbonate group by sulfur has been analyzed by comparing the T_g values and the ability to crystallize of the sulfur containing polymers with those of the corresponding polycarbonates.     

Characterization of chromium-induced apoptosis in cultured mammalian cells:: A differential scanning calorimetry study

The present study examined the cytotoxic effect of increasing Cr(VI) concentrations on cultured cells by a combination of biochemical methods and DSC, a novel use of DSC in the study of cell death. The characteristics of apoptotic cells are compared with normal cells. Chromatin in human epithelial-like L-41 cells has two thermal transitions at 100 and 105 °C. The heat from these endotherms is 90.5 ± 11.0 J/g DNA. The total heat of denaturation (Q_d) is 27.5 ± 3.5 J/g dry biomass. The heat evolved (−Q) is 15.6 ± 3.0 J/g dry biomass. The treatment of cells with 20 μM Cr(VI) for 2 and 4 h has not revealed any changes in heat of denaturation and heat evolution (−Q). However increased treatment time with Cr(VI) at 20 μM resulted in significant changes to the thermal profile and a sharp linear decrease of (−Q) and Q_d values. The Q_d and (−Q) values of cells treated with 20 μM Cr(VI) for 48 h are equal to 15.5 ± 2.0 and 2.1 ± 0.4 J/g dry biomass, respectively. The changes in chromatin conformation, Bax expression and the collapse of the mitochondrial membrane permeability coincide with the time point from which the action of chromium is irreversible.     

Enhanced surface plasmon resonance by Au nanoparticles immobilized on a dielectric SiO2 layer on a gold surface

This paper introduces strategies for enhancement of a surface plasmon resonance (SPR) signal by adopting colloidal gold nanoparticles (AuNPs) and a SiO₂ layer on a gold surface. AuNPs on SiO₂ on a gold surface were compared with an unmodified gold surface and a SiO₂ layer on a gold surface with no AuNPs attached. The modified surfaces showed significant changes in SPR signal when biomolecules were attached to the surface as compared with an unmodified gold surface. The detection limit of AuNPs immobilized on a SPR chip was 0.1 ng mL⁻¹ for the prostate-specific antigen (PSA), a cancer marker, as measured with a spectrophotometer. Considering that the conventional ELISA method can detect ∼10 ng mL⁻¹ of PSA, the strategy described here is much more sensitive (∼100 fold). The enhanced shift of the absorption curve resulted from the coupling of the surface and particle plasmons by the SiO₂ layer and the AuNPs on the gold surface.     

Swellable molecularly imprinted polyN-(N-propyl)acrylamide particles for detection of emerging organic contaminants using surface plasmon resonance spectroscopy

Lightly crosslinked theophylline imprinted polyN-(N-propyl)acrylamide particles (ca. 300 nm in diameter) that are designed to swell and shrink as a function of analyte concentration in aqueous media were spin coated onto a gold surface. The nanospheres responded selectively to the targeted analyte due to molecular imprinting. Chemical sensing was based on changes in the refractive index of the imprinted particles that accompanied swelling due to binding of the targeted analyte, which was detected using surface plasmon resonance (SPR) spectroscopy. Because swelling leads to an increase in the percentage of water in the polymer, the refractive index of the polymer nanospheres decreased as the particles swelled. In the presence of aqueous theophylline at concentrations as low as 10⁻⁶ M, particle swelling is both pronounced and readily detectable. The full scale response of the imprinted particles to template occurs in less than 10 min. Swelling is also reversible and independent of the ionic strength of the solution in contact with the polymer. Replicate precision is less than 10⁻⁴ RI units. By comparison, there is no response to caffeine which is similar in structure to theophylline at concentrations as high as 1 × 10⁻² M. Changes in the refractive index of the imprinted polymer particles, as low as 10⁻⁴ RI units could be readily detected. A unique aspect of the prepared particles is the use of light crosslinking rather than heavy crosslinking. This is a significant development as it indicates that heavy crosslinking is not entirely necessary for selectivity in molecular imprinting with polyacrylamides.     

Fluorinated phosphorus compounds: Part 10. Bis(fluoroalkyl) S-alkyl phosphorothiolates and tris(fluoroalkyl) phosphorothionates

Treatment of bis(fluoroalkyl) phosphites (R_FCH₂O)₂P(O)H, where R_F was CF₃ or C₂F₅ with sulfur in pyridine at 80 °C gave salts of structure [(R_FCH₂O)₂P(O)SH]NC₅H₅ in 90 and 88% yield, respectively. The salts reacted with alkyl iodides in acetonitrile at 50 °C to furnish bis(fluoroalkyl) S-alkyl phosphorothiolates (R_FCH₂O)₂P(O)SR, where R was Me, Et, n- and i-Pr (when R_F = CF₃) and Me (when R_F = C₂F₅). Yields ranged from 21 to 57%. Bis(trifluoroethyl) S-methyl phosphorothiolate (CF₃CH₂O)₂P(O)SMe underwent fluorination by silver(I) fluoride in acetonitrile at room temperature to yield the phosphorofluoridate (CF₃CH₂O)₂P(O)F in 75% yield. Tris(fluoroalkyl) phosphorothionates (R_FCH₂O)₃P = S, where R_F was CF₃, C₂F₅ and C₃F₇, were prepared in 30-34% yield by heating the tris(fluoroalkyl) phosphites (R_FCH₂O)₃P and sulfur to 200 °C in a sealed tube for 8 h.     

Complex macromolecular dynamics:: I. Estimation technique for time-resolved emission anisotropy ratio of chromophores incorporated into polymer chains

Time-resolved fluorescence emission anisotropy ratios of carbazolyl groups incorporated into polystyrene chains in polyethyleneoxide(PEO)/1,2-dichloroethane mixtures have been measured by the single photon counting method. The fluorescence depolarization method is very excellent to clarify various dynamical modes of polymer chains, and many theoretical and experimental researches have so far been reported in the field of polymer chain dynamics. However there are few reports about the dynamics on the polymer side chain, because the dynamical mechanism of the polymer side chain is very complicated. In this report we tried to analyze the dynamical modes of the polymer side chains by the fluorescence depolarization method. Five dynamical modes of a polymer chain based on the Wöessner model were estimated by our original analytical technique `χ²-map method'. The value of each mode of a polymer side chain was discussed above the overlap concentration (C^*) of PEO and the micro-environments were clarified in the vicinity of the chromophore attached to the polymer side chain.     

Combination of H nuclear magnetic resonance spectroscopy and mass spectrometry as tools for investigation of the thermolytic and solvolytic effects: Case of carbamates analysis

The carbamate pesticides are a well known thermo-sensible compound class. Under unfavourable conditions, these compounds are highly prone to degradation via fragmentation and/or rearrangement mechanisms. Their transformation processes are observed in consequence of two factors: structure with fragile bonds on the one hand and a stressing environment on the other hand leading to a difficult direct gas chromatography (GC) analysis, i.e. without derivatisation. In this paper, we investigated an original methodology based on the complementarity of analysis by proton nuclear magnetic resonance spectroscopy (¹H NMR) and those provided by GC hyphenated with ion-trap mass selective detection (GC–ITMS) to investigate combined effects of temperature and solvent nature affecting the behaviour of 16 carbamates. Among tested solvents, toluene and acetonitrile with 0.1% acetic acid were considered as the best solvents for storage and GC analysis respectively. Carbaryl, chlorpropham, carbofuran and N-sulfenylated compounds began to be thermodegraded with a loss equal to 1–5% even at 50 °C. An on-column injection validated as providing no degradation was used to analyse the identical solution that in ¹H NMR and it was emphasised that results of the measured degradation rates were identical at ±2%. It was highlighted that this methodology was extensible to study mechanisms and parameters with other (bio)molecules.     

Regioselective phosphorylation of vicinal 3,4-hydroxy myo-inositol derivative promoted practical synthesis of d-PtdIns(4,5)P2 and d-Ins(1,4,5)P3

The reactivity of 3 and 4-OH in 3,4-diol myo-inositol derivatives were observed through the phosphorylation, acylation and silylation. The results indicated that 3-OH is much more reactive than 4-OH, giving regiospecifically 3-mono-functionalized products. This investigation provided a concise methodology for the synthesis of natural d-form of PtdIns(4,5)P2 and d-Ins(1,4,5)P3 from l-1,2-O-cyclohexylidene-3,4-O-(tetraisopropyl disiloxane-1,3-diyl)-myo-inositol.     

Fluorinated phosphorus compounds: Part 7. The reactions of bis(fluoroalkyl) phosphorochloridates with nitrogen nucleophiles

Forty bis(fluoroalkyl) phosphoramidates (R_FO)₂P(O)R were prepared in 10-91% yield by treating phosphorochloridates (R_FO)₂P(O)Cl where R_F was HCF₂CH₂, HCF₂CF₂CH₂, HCF₂CF₂CF₂CF₂CH₂, CF₃CH₂, C₂F₅CH₂, C₃F₇CH₂, (CF₃)₂CH, (FCH₂)₂CH and (CH₃)₂CF₃C with nucleophiles HR, where R was NH₂, NHMe, NMe₂, NHEt and NEt₂ in diethyl ether at 0-5 °C. The bulky chloridate [(CH₃)₂CF₃CO]₂P(O)Cl reacted with ammonia, methylamine, dimethylamine and ethylamine, but not with diethylamine—even on heating in the presence of 4-dimethylaminopyridine—due to steric hindrance at phosphorus. Fluorinated phosphoramidates have lower basicity and nucleophilicity than their unfluorinated counterparts: (EtO)₂P(O)NH₂ is more easily hydrolysed by HCl than (CF₃CH₂O)₂P(O)NH₂ and whereas, (EtO)₂P(O)NH₂ is known to react with oxalyl chloride and thionyl chloride to give (EtO)₂P(O)NCO and (EtO)₂P(O)NSO respectively, (CF₃CH₂O)₂P(O)NH₂ reacted only with oxalyl chloride to give (CF₃CH₂O)₂P(O)NCO in 10% yield. Two other new fluorinated species, (CF₃CH₂O)₂P(O)NHOMe and (CF₃CH₂O)₂P(O)N₃, were prepared by nucleophilic substitution of bis(trifluoroethyl) phosphorochloridate with methoxyamine and azide ion.     

Low-temperature F NMR spectroscopy of 1-fluoro-1-lithioethenes : Stability, shifts and unexpected coupling constants

Half-lives and fluorine atom shifts of stabilized 1-fluoro-1-lithioethenes bearing hydrogen, fluorine, phenyl, and/or dimethylphenylsilyl groups in the β-positions have been determined by a low-temperature ¹⁹F NMR spectroscopy. Some 1-fluoro-1-lithioethenes displayed an exceptionally low value of the trans-³J_FF coupling constant. Stereoselectivity of carbenoid formation, as well as an effect of configuration on the stability is discussed.     

Fluorinated phosphorus compounds: Part 8. The reactions of bis(fluoroalkyl) phosphorochloridates with sulfur nucleophiles

The reactivity of bis(fluoroalkyl) phosphorochloridates to nucleophiles is summarised. Previous data and the results described here indicate that reactivities decrease in the order: amines>alcohols>thiols. The synthesis of CF₃CH₂OP(O)(SEt)₂ in 30% yield was accomplished by treating CF₃CH₂OP(O)Cl₂ with two molar equivalents of EtSH and Et₃N in ether. The chloridates (CF₃CH₂O)₂P(O)Cl and (C₂F₅CH₂O)₂P(O)Cl did not react with MeSH in ether at −78 °C or when heated with Pb(SMe)₂ in benzene. Ethanethiol and propanethiol reacted with fluorinated chloridates in the presence of triethylamine to give thiolates (R_FO)₂P(O)SR in 13-41% yield where R_F was CF₃CH₂, C₂F₅CH₂, C₃F₇CH₂ or (CF₃)₂CH and R was Et or n-Pr. Similarly, reaction of phosphorobromidates (R_FCH₂O)₂P(O)Br, made by brominating the corresponding bis(fluoroalkyl) H-phosphonates, with benzenethiol gave derivatives (R_FCH₂O)₂P(O)SPh in 43 and 46% yield where R_F was CF₃ and C₂F₅, respectively. Treatment of the chloridothiolate Cl(EtO)P(O)SMe, prepared in two steps from triethyl phosphite, with fluoroalcohols and triethylamine in ether gave species R_FO(EtO)P(O)SMe in 62-74% yield where R_F was CF₃CH₂, C₂F₅CH₂, C₃F₇CH₂ or (CF₃)₂CH. The reactions of bis(trifluoroethyl) phosphorochloridate with 2-mercaptoethanol, 3-mercaptopropanol and ethane-1,2-dithiol gave several unexpected products whose structures were tentatively assigned.     

Interactions between Ni ions and tetrapeptides containing (Asp/Lys)HisGly(l/d)His sequence

A series of linear tetrapeptides containing two histidyl residues in positions 2 and 4 with different chirality: DHGH, DHG(d-His), KHGH, KHG(d-His), Ac-DHGH-NH₂, Ac-DHG(d-His)-NH₂, Ac-KHGH-NH₂, and Ac-KHG(d-His)-NH₂ were synthesized, characterized and their binding properties towards Ni²⁺ were investigated. To establish the stoichiometry and the stability of the resulting Ni²⁺ complexes, potentiometric titrations were carried out. The coordination mode of the complexes formed was investigated by performing extensive spectroscopic analyses (UV–Vis, CD) in strict correlation with the potentiometric results. The effects of the nature of the first amino acid (Lys versus Asp) and of the N-terminal amino group acetylation were determined. A careful comparison of the Ni²⁺ coordination abilities of the linear peptides provides a specific insight into the impact of the chirality of the C-terminal histidine residue (His⁴) on the metal binding properties.     

Enzyme immobilization procedures on screen-printed electrodes used for the detection of anticholinesterase pesticides: Comparative study

A comparison between several acetylcholinesterase (AChE) immobilization procedures on the 7,7,8,8-tetracyanoquinodimethane (TCNQ)-modified graphite working electrodes is presented. The immobilization methods employed crosslinking with glutaraldehyde in presence of BSA protein and photopolymerization with poly(vinyl alcohol) bearing styrylpyridinium groups (PVA-SbQ). The main variations were related to the enzyme charge in each electrode and the enzyme conditioning and storage conditions after immobilization. Initially, the enzyme-substrate reaction was carried out and the following parameters were chrono-amperometrically and -coulometrically monitored: current intensities, time to stabilize the current response, and the mass transfer represented by the Coulomb charge. The screen-printed biosensors that presented best characteristics were then used to perform the inhibition assays and to verify the sensitivity against the following NMC insecticides: aldicarb, carbaryl, carbofuran, and methomyl.In general, diffusion of electrons into the sensitive layer, mass transfer, and time to stabilize the current were adequate in all cases. The Cottrell law was followed before the 1 min of enzyme-substrate reaction. Adequate reproducibility within electrochemical measurements was also observed, with relative standard deviations varying from 6.5 to 18.6%.AChE immobilization with glutaraldehyde allow to obtain robust and reproducible biosensors, but they need a much higher enzyme content (80 mUA per electrode) to achieve current values comparable to that constructed by immobilizing the AChE through photopolymerization with PVA-SbQ (0.7 to 1 mUA per electrode). The limits of detection were determined with a minimum 10% inhibition, and varied from 10⁻⁹ to 8×10⁻⁹ M (0.2 to 1.5 ppb) by employing the enzyme immobilization through photopolymerization with PVA-SbQ. In practice, this kind of immobilization procedure is much simpler and produces good results: fast response, adequate reproducibility, large pesticides working ranges, and excellent sensitivities to N-methylcarbamates (NMCs) which in general do not present enzyme inhibition power as elevated as for the organophosphate pesticides.     

New Sn(IV) and Ti(IV) bis(trimethylsilyl)amides in d,l-lactide polymerization, SEM characterization of polymers

Ring-opening polymerization of d,l-lactide initiated with new chlorotris(bis(trimethylsilyl) amido) tin(IV), tetrakis(bis(trimethylsilyl)amido) tin(IV) and titanium(IV) was investigated. New complexes reveal practically quantitative conversion degrees and produced polymers with higher molecular weight with respect to reference alkoxo-species.The X-ray crystal structure of chlorotris(bis(trimethylsilyl)amido) tin (IV) was investigated. Axial enantiomerism of [SnCl{N(SiMe₃)₂}₃] molecules in solution was studied by high-field dynamic NMR, the value of Gibbs activation energy ΔG^‡ = 59.5 kJ/mol.Field emission SEM investigation of bulk polymer samples and thin films on conductive Al foil revealed a stratified fibrous textures in the bulk polymers, as well as nanoscaled topographical features due to coils and entanglements of individual macromolecules in thin films.     

Fluorinated phosphorus compounds: Part 11. The reactions of some fluorinated amines with dialkyl and bis(fluoroalkyl) phosphorochloridates

Dimethyl phosphorochloridate reacted with R_FCH₂NH₂ in ether in the presence of Et₃N to afford (MeO)₂P(O)NHCH₂R_F, where R_F = CF₃ and C₂F₅, in 39 and 47% yield, respectively. Similar reactions with di-n-propyl and diisopropyl phosphorochloridates could be effected only with H₂NCH₂CF₃ when 4-dimethylaminopyridine catalyst was added and (n-PrO)₂P(O)NHCH₂CF₃ and (i-PrO)₂P(O)NHCH₂CF₃ were isolated in 49 and 25% yield, respectively. Treatment of POCl₃ with one molar equivalent each of H₂NCH₂CF₃ and Et₃N permitted the synthesis of Cl₂P(O)NHCH₂CF₃ in 43% yield. Bis(fluoroalkyl) phosphorochloridates (R_FO)₂P(O)Cl, where R_F = C₂F₅CH₂, C₃F₇CH₂ and (CF₃)₂CH, reacted with 2,2,2-trifluoroethylamine and 2,2,3,3,3-pentafluoropropylamine to furnish phosphoramidates (R_FO)₂P(O)NHCH₂R, where R = CF₃ or C₂F₅, in yields of 32-67%.     

Synthesis and characterisation of Pd(II) complexes with a derivative of aminoazobenzene: Dynamic H-NMR study of cyclopalladation reactions in DMF

Three new Pd(II) complexes, i.e. [PdCl₂L]₂ (A), PdCl₂L₂ (B) and [Pd(μ-Cl)(L-H)]₂ (C), each with two diethyl [α-(4-benzenazoanilino)-2-hydroxybenzyl]phosphonates (L) bound to either one or two palladium atoms, are synthesized and characterized by elemental analysis, by IR, UV-vis and solid-state ¹³C-NMR spectra. Complexes B and C are additionally characterized by ¹H-, ¹³C- and ³¹P-NMR and electrospray mass spectrometry (ESMS) studies using dimethylformamide (DMF) as a solvent. In DMF solution adducts A and B undergo spontaneous rearrangement into the cyclopalladated complex C. Dynamic ¹H-NMR study of this rearrangement as well as of the reactions of L with PdCl₂ and Na₂PdCl₄ revealed a complex equilibrium in DMF solutions and enabled the formation mechanism of all involved species to be resolved. The complex A is immediately solvolyzed producing two molecules of intermediate M [PdCl₂(L)(DMF)]. Complex M was also the first intermediate in the reaction of L with PdCl₂. Once present in concentration above 10⁻⁵ mol dm⁻³M dimerizes very fast into chloro-bridged dimer [PdCl(μ-Cl)(L)]₂ (D) which undergoes cyclopalladation and converts into the complex C. The formation of C from the intermediate D is clearly demonstrated by the concentration dependence of the cyclopalladation reaction which has order greater than one. Chloride ions, released by cyclopalladation, react with D by splitting chloro-bridge and binding to metal atoms to produce byproduct [PdCl₃(L)]⁻ (T). The same species T are formed in the reaction of L with Na₂PdCl₄ whereby a chloride ion is replaced by the ligand L. The complex B undergoes similar, but slower, solvolytic reaction producing M and L while further reaction steps are identical as in the solvolysis of A.     

Kinetics of thermo-oxidative and thermal degradation of poly(d,l-lactide) (PDLLA) at processing temperature

Poly(d,l-lactide) (PDLLA) degraded at processing temperature under air and nitrogen. A random chain scission model was established and used to determine the activation energy E_a, and FT-IR, ¹H and ¹³C NMR were used to elucidate the degradation behavior under different atmospheres. Results showed that there were two to three stages. The 1st stage was dominated by the oligomers containing carboxylic acid groups and hydroxyl groups, during which oxygen and nitrogen had little effect on the degradation, thus they share similar E_a. When the oligomers were consumed over or evaporated, the 2nd stage began, and oxygen had a promoting effect on the thermo-oxidation process, resulting in the great decrease in E_a. The third stage of PDLLA was observed when it degraded under nitrogen over 200 °C, which was caused by the appearance of carboxylic acid substance.     

Fluorinated phosphorus compounds: Part 6. The synthesis of bis(fluoroalkyl) phosphites and bis(fluoroalkyl) phosphorohalidates

Reaction of phosphorus trichloride with tert-butanol and fluoroalcohols gave bis(fluoroalkyl) phosphites (R_FO)₂P(O)H in 42-89% yield, where R_F=HCF₂CH₂, H(CF₂)₂CH₂, H(CF₂)₄CH₂, CF₃CH₂, C₂F₅CH₂, C₃F₇CH₂, (CF₃)₂CH, (FCH₂)₂CH, CF₃(CH₃)₂C, (CF₃)₂CH₃C, CF₃CH₂CH₂, C₄F₉CH₂CH₂ and C₆F₁₃CH₂CH₂. Treatment of these with chlorine in dichloromethane gave the bis(fluoroalkyl) phosphorochloridates (R_FO)₂P(O)Cl in 49-96% yield. The chloridate (CF₃CH₂O)₂P(O)Cl was isolated in much lower yield from the interaction of thionyl chloride with bis(trifluoroethyl) phosphite. Heating the latter in dichloromethane with potassium fluoride and a catalytic amount of trifluoroacetic acid gave the corresponding fluoridate (CF₃CH₂O)₂P(O)F in 84% yield. Treatment of bis(trifluoroethyl) phosphite with bromine or iodine gave the bromidate (CF₃CH₂O)₂P(O)Br and iodidate (CF₃CH₂O)₂P(O)I in 51 and 46% yield, respectively. The iodidate is the first dialkyl phosphoroiodidate to have been isolated and characterised properly—its discovery lags behind the first isolation of a dialkyl phosphorochloridate by over 130 years. The fluoroalkyl phosphoryl compounds are generally more stable than known unfluorinated counterparts.     

Mechanisms involved in stannane generation by aqueous tetrahydroborate(III): Role of acidity and l-cysteine

The role played by acidity (0.01–5 mol L^− 1 HNO₃) and l-cysteine (0.1–0.2 mol L^− 1) in the formation of stannane by reaction of Sn(IV) solution with aqueous tetrahydroborate(III) (0.05–0.2 mol L^− 1), has been investigated by continuous flow hydride generation coupled with atomic absorption spectrometry using a miniature argon–hydrogen diffusion flame as the atomizer. Different mixing sequences and reaction times of the reagents were useful in the identification of those processes which contribute to the generation of stannane in different reaction conditions, both in the absence and in the presence of l-cysteine. The lack of stannane generation at high acidities is due to the formation of Sn substrates and hydridoboron species which are unreactive. The capture of the stannane in solution, following its ionization to SnH₃⁺ from already formed stannane, does not play any role. While the presence of l-cysteine, does not affect the generation efficiency at lower acidities, it expands the optimum range of acidities for stannane generation to higher values. This effect can be addressed to both the buffering capacity of l-cysteine and to the formation of Sn-(l-cysteine) complexes, while the formation of (l-cysteine)–borane complexes do not play a significant role. Formation of Sn-(l-cysteine) complexes also appears to be useful for stabilization of tin solution at low acidities values.