Loss Of HCl Research Articles

1H NMR and electrospray mass spectrometry of the mono-ionized bis(2,2′-bis(4,5-dimethylimidazole)chloronitrosylruthenium(II) complex ([Ru(NO)Cl(LH 2) 2] +, LH 2=2,2′-bis(4,5-dimethylimidazole)

The reaction of RuCl 3(NO)(H 2O) 2 with 2 equiv. of LH 2=2,2′-bis(4,5-dimethylimidazole) in refluxing ethanol generates cis-[Ru(NO)Cl(LH 2) 2] 2+ ( 1), analogous in structure to cis-[Ru(NO)Cl(bpy) 2] 2+, as the chloride salt. In 1, the methyl groups are differentiated into eight different 1H NMR magnetic environments. Substitution of 4,5-dimethyl-2,2′-biimidazole (L′H 2), an 11.1% impurity in commercial LH 2, occurred randomly with the undecorated ring diminishing the intensity of all eight resonances equally. The methyl group of the “out-of-plane” ring that hangs over the π orbitals of the NO + ligand (CH 3(6)) is shifted most upfield from 2.19 ppm of free LH 2 and is assigned to the 1.23 ppm resonance. With the aid of 2-D NMR methods, we assign the following shifts. The ring donor opposite the {Ru(NO)} 3+, CH 3(7), should experience the greatest withdrawing influence, and is assigned as the origin of the 2.50 ppm resonance. Its ring partner, CH 3(5), placed below another ring current, is assigned to the resonance at 2.13 ppm. 2-D NMR methods support the assignments of 1.39 ppm to CH 3(1) and 2.09 ppm to CH 3(2), the “in-plane-near” CH 3 groups; 2.36 and 2.34 ppm to “in-plane-remote” CH 3(3) and CH 3(4); a 2.47 ppm shift is assigned to the remaining CH 3(8). Because of the presence of the impurity L′H 2 which has a substitution rate advantage (ca. 2.14-fold) due to a lower steric barrier for the unmethylated ring, the isolated product contained 62.4% ( 1a) [Ru(NO)Cl(LH 2) 2]Cl 2, 31.9% ( 1b) [Ru(NO)Cl(LH 2)(L′H 2)]Cl 2, and 5.7% ( 1c) [Ru(NO)Cl(L′H 2) 2]Cl 2. The ESI MS spectrum exhibits parent 1+ ions ( 2a– c) in which one of the imidazole rings has been deprotonated. Thus, eight-line patterns for RuCl-containing fragments appear for m/ z with z=1+ centered about 546 ( 2a), 518 ( 2b) and 490 ( 2c) in the intensity ratios of 1.000:0.511:0.091, respectively. The atomic composition for 2a was shown to be RuC 20H 27N 9OCl ( m/ z=540.109049) by checking the “540” line of the isotopic bundle around m/ z=546. The atomic composition of 2b was established from the “512” mass as RuC 18H 23N 9OCl ( m/ z=512.077748) from the isotopic bundle around m/ z=518. 2a– c undergo the loss of LH 2 or L′H 2 with low efficiency, but few other fragmentations were observed. Notably, the loss of NO or HCl are absent. 2a– c have good π-donating imidazole and imidazolato functionalities which suppress NO loss. IR laser loss experiments on 2a in the mass spectral cavity were unable to identify a frequency value that selectively dissociates NO. Rather, complete fragmentation of the complexes 2a– c occurred at energies sufficient to induce any ligand dissociation; the parent ions being very robust. The 1H NMR data are supported by an MMFF94 energy-minimized structure for 1 and its theoretical trans isomer.

Glycine Crystallization during Spray Drying: The pH Effect on Salt and Polymorphic Forms

Spray drying of aqueous solutions of glycine revealed a strong pH effect on the salt and polymorphic forms of the resulting powders. Adjusting pH by aqueous HCl or NaOH between 1.7 and 10.0 caused the glycine solutions to crystallize as two polymorphs (α and γ) of the neutral glycine (+H3NCH2CO2−) and as three salts (diglycine HCl, +H3NCH2CO2− · +H3NCH2CO2H · C1−; glycine HCl, +H3NCH2CO2H · C1−; and sodium glycinate, H2NCH2CO2− · Na+). Although α‐glycine crystallized from solutions without pH adjustment (pH 6.2), changing the pH to 4.0 and 8.0 caused γ‐glycine to crystallize as the preferred polymorph. This phenomenon is attributed to the pH effect on the dimeric growth unit of α‐glycine. The formation of α‐glycine by spray drying solutions of neutral glycine contrasts the outcome of freeze drying, which yields β‐glycine. Because γ‐glycine is thermodynamically more stable than α‐glycine, the crystallization of γ‐glycine by pH adjustment provides a way to improve the physical stability of glycine‐containing formulations. Spray drying at low pH yielded various mixtures of neutral glycine and its HCl salts: pH 3.0, γ‐glycine and diglycine HCl; pH 2.0, diglycine HCl; and pH 1.7 (the natural pH of glycine HCl), diglycine HCl (major component) and glycine HCl (minor component). Spray drying glycine HCl solutions (pH 1.7) yielded the same diglycine HCl/glycine HCl mixture as did spray drying neutral glycine solutions acidified to pH 1.7. Obtaining diglycine HCl by spray drying glycine HCl solutions indicates a 50% loss of HCl during processing. The extent of HCl loss could be altered by changing the inlet temperature of the spray drier. Spray drying glycine solutions at pH 9.0 and 10.0 gave predominantly γ‐glycine and an additional crystalline product, possibly sodium glycinate. The glycine powders spray dried at different pH had different particle morphologies and sizes, which may influence their suitability for pharmaceutical formulations. © 2002 Wiley‐Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 91:2367–2375, 2002

Gas-phase behaviour of negative ions produced from thiazidic diuretics under electrospray conditions.

A systematic mass spectrometric study of 10 thiazidic diuretics and related compounds was undertaken by mass spectrometry (MS) with electrospray ionization in the negative ion mode. Collisional dissociation 'in-source' (CID-MS) and in a low-pressure collision cell (CID-MS/MS) were compared in both excitation regions. Spectra obtained by CID-MS and by CID-MS/MS were matched. Using the two methods, loss of HCl and consecutive dissociations from 2HCl losses were exhibited from compounds such as methyclothiazide and trichlormethiazide but not from other thiazidic diuretics that contain chlorine substituents in the aromatic moiety. However, deprotonated dichlorphenamide gave rise to loss of HCl by CID-MS and CID-MS/MS. For other diuretics such as hydroflumethiazide and hydrochlorothiazide, the loss of HCN and [HCN + SO(2)] was relevant. Reaction mechanisms were checked by means of deuterium-hydrogen exchange, which showed that deprotonation took place regioselectively on the heterocyclic moiety. The cleavage pathways require molecular isomerization forming ion-dipole complexes prior to decompositions, allowing long-distance proton transfer for neutral elimination. Identifications of the most specific fragmentations presented in this paper were applied to the screening and unambiguous identification of diuretics for horse doping control.

Mass spectrometry of cis-diamminedichloroplatinum(II) adducts with the dinucleosidemonophosphates d(ApG), d(GpG) and d(TpC) in an ion trap.

The detection and fragmentation behaviour of adducts of the chemotherapeutic cis-diamminedichloroplatinum(II) (cisplatin) with the dinucleosidemonophosphates d(ApG), d(GpG) and d(TpC) as model compounds for DNA adducts in an ion trap with electrospray ionization were studied. Mainly the monofunctional adduct, the bifunctional adduct and the bifunctional adduct with platinum bridging two dinucleosidemonophosphates were detected. In addition, several more complex adducts were seen resulting from reactions among these species. Adduct formation was low in the case of d(TpC). Fragmentation could be controlled strongly by varying the temperature of the transfer capillary; furthermore, tandem mass spectrometric (MS/MS) experiments on both the monofunctional and the bifunctional adducts were performed. For the adducts of d(ApG) and d(GpG) losses of NH(3) and HCl were the most dominant reactions, followed by the losses of one, then another two units of 98 amu from the sugar-phosphate backbone, whereas d(TpC)-Pt predominantly forms the dinucleosidemonophosphate. In the gas phase, the conversion of the monofunctional into the bifunctional adducts through binding to another site in the dinucleotide accompanied by loss of NH(3) or HCl could also be observed. The removal of a ligand from the coordination sphere of the square-planar platinum complexes appeared to be the crucial step for the induction of further fragmentation of the dinucleotide ligand. MS(n) experiments of the bifunctional adducts of d(ApG) and d(GpG) revealed different fragmentation pathways involving the loss of phosphoric acid, metaphosphoric acid, deoxyribose units (intact or dehydrated) and the nucleobases in different orders, leaving characteristic binding site-determining fragments. Fragmentation of these ions was also performed, mainly resulting in fragmentation of the bases. The study confirmed the remarkable stability of the platinum-guanine bond compared with other nucleobases.

Novel furano analogues of duocarmycin C1 and C2: design, synthesis, and biological evaluation of seco-iso-Cyclopropylfurano[2,3- e]indoline ( seco-iso-CFI) and seco-Cyclopropyltetrahydrofurano[2,3- f]quinoline ( seco-CFQ) analogues

The design, synthesis and biological evaluation of novel seco-iso-cyclopropylfurano[2,3- e]indoline ( seco-iso-CFI) and the seco-cyclopropyltetrahydrofurano[2,3- f]quinoline ( seco-CFQ) analogues of the duocarmycins are described. These novel analogues ( 4– 7) were designed on the premise that the lone pair of electrons on the furano-oxygen atom could enter into conjugation with the isocyclopropylfurano[ e]indolone (iso-CFI) alkylating moiety, formed from the loss of HCl in compounds 4– 7. The seco-iso-CFI DNA alkylating pharmacophore was synthesized through a well precedented approach of 5-exo-trig aryl radical cyclization with a vinyl chloride. In our studies, in addition to the formation of the seco-iso-CFI product, an equal amount of an unexpected seco-CFQ product was also generated during the radical cyclization reaction. Like CC-1065 and adozelesin, using Taq DNA polymerase stop and thermal cleavage assays, the seco-iso-CFI compounds ( 4 and 6) and the seco-CFQ compounds ( 5 and 7) were shown to preferentially alkylate the adenine-N3 position within the minor groove of long stretches of A residues. A MM2 energy optimized molecular model of a 1:1 complex of compound 6 with DNA reveals that the iso-CFI compound fits snugly within the minor groove. Using a MTT based experiment, the cytotoxicity of compounds 4– 7 were determined against the growth of murine leukemia (L1210), mastocytoma (P815) and melanoma (B16) cell lines. The concentrations of compounds required to inhibit the growth of these tumor cells by 50% is in the range of 10 −8 M. These compounds were also tested against a panel of human cancer cells by the National Cancer Institute, demonstrating that the compounds exhibited a high level of activity against selected solid tumors. At a concentration of 0.0084 μM (based on the IC 50 of compound 17 ( seco-CBI-TMI) against the growth L1210 cells), while compounds 4 and 17 were toxic against murine bone marrow cells as judged by a colony forming study of freshly isolated murine progenitor hematopoeitic cells, compound 5, a seco-CFQ compound, was significantly less toxic. Flow cytometric analysis of P815 cells that had been incubated for 24 h with compounds 4 and 5 at their cytotoxic IC 50 concentrations indicated the induction of apoptosis in a large percentage of cells, thereby suggesting that this might be the mechanism by which the iso-CFI compounds kill cells.

Determination of drug binding sites to proteins by electrospray ionisation mass spectrometry: the interaction of cisplatin with transferrin.

Cisplatin, cis-[PtCl2(NH3)2], is known to bind to human serum transferrin, but the binding site remains a matter of some debate. Electrospray ionisation mass spectrometry has been used to characterise the interaction of cisplatin with transferrin. The studies indicate that cisplatin initially docks with, and subsequently bonds covalently to, the hydroxyl functional group of threonine 457, with the loss of HCl affording a transferrin-O-PtCl(NH3)2 adduct.

Preparation of highly insulating dimeric and polymeric metal complexes with higher thermal stability in the solid state

Cobalt(II), nickel(II) and copper(II) complexes of Schiff bases derived from isoniazide (pyridylhydrazone) and salicylaldehyde were prepared and characterised. The study indicates that the ligand coordinates in its keto form (except for complex 4 obtained from the reaction of nickel acetate) to give monomeric (2 and 5) and polymeric (1, 3, and 4) complexes. The keto form of the ligand in the complexes transforms into enol one through the loss of HCl or HNO 3 upon heating in the solid state. The monomeric complexes of nickel and copper are thermochromic in both solid state and DMF. The thermochromism obtained is discussed in terms of geometrical and structural changes. The two complexes change their colours from yellow and orange into red and green, respectively, upon heating in the solid state. The dimeric red form and polymeric green form are characterised by higher thermal stability as well as insulating properties.

Direct collection of HNO 3 and HCl by a diffusion scrubber without inlet tubes

Laboratory and field studies were conducted to evaluate the transmittance losses and interactions of atmospheric HNO 3 and/or HCl through inlet tubings at a flow rate of 1.0 l min −1. Approximately 80% of HNO 3 and 70% of HCl in the dry standard gas were lost through the stainless steel tubing (3 mm i.d., 1.5 m). The loss of HCl through PFA tubing (3 mm i.d., 10 m length) under the given dry and humid conditions was negligible. As for HNO 3 on PFA tubing, although the loss was negligible at <50% RH, relative humidity increased the loss up to about 10% at 77% RH. When an HNO 3/HCl mixed standard gas passed through the PFA tubing which had been exposed to the marine atmosphere, the loss of HNO 3 was enhanced up to ∼50% at 77% RH, and HCl artifact was simultaneously produced by the reaction of HNO 3 with deposited NaCl sea-salt particles. To eliminate the loss and interaction of HNO 3 and HCl through inlet tubing, direct collection without inlet tubing was performed by installing an outdoor diffusion scrubber that was connected to an indoor ion chromatograph (direct DS-IC system). HNO 3 and HCl in the marine atmosphere were measured by the direct DS-IC system along with another DS-IC system connecting PFA inlet tubing (3 mm i.d., 10 m length) prior to the diffusion scrubber (tubing DS-IC system). As a result, there were a reduction of 22–53% of HNO 3 and an increase of 15–106% of HCl through the PFA tubing, which were the negative and positive artifacts produced by the reaction of HNO 3 with the deposited NaCl. Thus, inlet tubing should not be used for collecting atmospheric HNO 3 and HCl especially in marine environments. The direct DS-IC system is useful for their measurements.

Hetero-Diels-Alder reactions of chlorodithioformates with acyclic 1,3-dienes

At elevated temperatures chlorodithioformates 1 react with acyclic 1,3-dienes 2 with remarkable regioselectivity to yield 2 H -3,6-dihydrothiopyrans 3 . Spontaneous loss of HCl from 3 leads to the isolable but labile 2 H -thiopyrans 4 .

Analysis of platinum group elements and gold in geological materials using NiS fire assay and Te coprecipitation; the NiS dissolution step revisited

The NiS fire assay–Te coprecipitation separation procedure for inductively coupled plasma mass spectrometry (ICP-MS) analyses of platinum-group elements (PGE) in silicate rocks has been revisited with the aim of reducing volatile PGE losses (Os, Pd). The NiS bead was dissolved in 20.2% HCl, in an open system allowing H 2S to escape without loss of HCl. Yield, accuracy and reproducibility were tested by replicate analyses of a CANMET reference material (UMT1), a mantle lherzolite (FON B 93), prepared as in-house standard, and abyssal harzburgites, analysed as unknowns. The yields as estimated from UMT1 range from 97% (Ir) to 93–94% (Rh, Pt, Pd) and 91% (Au). The Os value (7.13±1.4 ppb) is equal within 1 sigma level, to the CANMET provisional value. The mean Os content of FON B 93 (3.42 ppb) fits the Os concentration inferred for the terrestrial mantle very well, as does the Os/Ir ratio (1.053 vs. 1.063) while Pd concentrations are increased by 18% compared to previous analyses after open-beaker dissolution steps. The abyssal harzburgites also yield consistent Os contents (3.28±0.19 ppb) and a perfectly chondritic Os/Ir ratio (1.07). Thus modified, the NiS fire-assay method allows Os to be nearly completely recovered, while greatly reducing the volatility of Pd. Moreover, the PGE analyses of coarse-grained rocks are highly reproducible (1% for Rh, Pt, Pd; 4% for Ir, 5% for Ru, 6% for Au), if performed from large-sized powder aliquots.

Ranking of gas-phase acidities and chloride affinities of monosaccharides and linkage specificity in collision-induced decompositions of negative ion electrospray-generated chloride adducts of oligosaccharides

Negative ion electrospray-tandem mass spectrometry has been employed to study chloride adducts of saccharide molecules. Decompositions of [M + Cl] − obtained under identical low-energy collision conditions allow the approximate ranking of chloride affinities and gas-phase acidities of a series of isomeric monosaccharides. The ketohexoses are found to be more acidic than the aldohexoses. Chloride adduct decompositions are examined for a glucopyranosyl fructose and a glucopyranosyl glucose series. For each disaccharide series, the linkage position is shown to markedly influence the favored pathways of [M + Cl] − decompositions, initiated either by loss of neutral HCl to form [M − H] − and possibly leading to further (consecutive) decompositions, or by loss of M to form Cl −. Upon formation of [M − H] −, both cross-ring cleavages and glycosidic bond decompositions were observed in varying degrees for the two series of disaccharides. Remarkably, for three non-reducing polysaccharides that each contain a terminal sucrose group at the “downstream” end, chlorine-containing product ions arising from cleavage of the Glcα–2Fru linkage have been observed. Apart from Cl −, chlorine-containing product ions are not observed for any of the other disaccharides investigated, and they appear to be specifically diagnostic of a terminal Glcα–2Fru linkage. Their appearance is rationalized based upon a substantially reduced tendency for HCl loss from these non-reducing polysaccharides.

Electrospray mass spectrometry of trans-[Ru(NO)Cl(dpaH) 2] 2+ (dpaH=2,2′-dipyridylamine) and ‘caged NO’, [RuCl 3(NO)(H 2O) 2]: loss of HCl and NO from positive ions versus NO and Cl from negative ions

The positive ion electrospray mass spectrometry (ESI-MS) of trans-[Ru(NO)Cl)(dpaH) 2]Cl 2 (dpaH=2,2′-dipyridylamine), obtained from the carrier solvent of H 2O–CH 3OH (50:50), revealed 1+ ions of the formulas [Ru II(NO +)Cl(dpaH)(dpa)] + ( m/ z=508), [Ru IIICl(dpaH)(dpa −)] + ( m/ z=478), [Ru II(NO +)(dpa) 2] + ( m/ z=472), [Ru III(dpa) 2] + ( m/ z=442), originating from proton dissociation from the parent [Ru II(NO +)Cl(dpaH) 2] 2+ ion with subsequent loss of NO (17.4% of dissociative events) or loss of HCl (82.6% of dissociative events). Further loss of NO from the m/ z=472 fragment yields the m/ z=442 fragment. Thus, ionization of the NH moiety of dpaH is a significant factor in controlling the net ionic charge in the gas phase, and allowing preferential dissociation of HCl in the fragmentation processes. With NaCl added, an ion pair, {Na[Ru II(NO)Cl(dpa) 2]} + ( m/ z=530; 532), is detectable. All these positive mass peaks that contain Ru carry a signature ‘handprint’ of adjacent m/ z peaks due to the isotopic distribution of 104Ru, 102Ru, 101Ru, 99Ru, 98Ru and 96Ru mass centered around 101Ru for each fragment, and have been matched to the theoretical isotopic distribution for each set of peaks centered on the main isotope peak. When the starting complex is allowed to undergo aquation for two weeks in H 2O, loss of the axial Cl − is shown by the approximately 77% attenuation of the [Ru II(NO +)Cl(dpaH)(dpa)] + ion, being replaced by the [Ru II(NO +)(H 2O)(dpa) 2] + ( m/ z=490) as the most abundant high-mass species. Loss of H 2O is observed to form [Ru II(NO +)(dpa) 2] + ( m/ z=472). No positive ion mass spectral peaks were observed for RuCl 3(NO)(H 2O) 2, ‘caged NO’. Negative ions were observed by proton dissociation forming [Ru II(NO)Cl 3(H 2O)(OH)] − in the ionization chamber, detecting the parent 1− ion at m/ z=274, followed by the loss of NO as the main dissociative pathway that produces [Ru IIICl 3(H 2O)(OH)] − ( m/ z=244). This species undergoes reductive elimination of a chlorine atom, forming [Ru IICl 2(H 2O)(OH)] − ( m/ z=208). The ease of the NO dissociation is increased for the negative ions, which should be more able to stabilize a Ru III product upon NO loss.

A low temperature method for the synthesis of new lead selenite chlorides: Pb(3)(SeO(3))(SeO(2)OH)Cl(3) and Pb(3)(SeO(3))(2)Cl(2).

Two new lead selenite oxychlorides, Pb3(SeO3)(SeO2OH)Cl3 and Pb3(SeO3)2Cl2, have been synthesized by a low temperature (T ∼ 160 °C) reflux method. This method enabled us to synthesize the compounds in high yield, 62% and 81% for Pb3(SeO3)(SeO2OH)Cl3 and Pb3(SeO3)2Cl2, respectively, and as crystals. Both materials contain lead(II)−oxychloride groups linked to selenium(IV)−oxide moieties. Additional experiments indicate that Pb3(SeO3)(SeO2OH)Cl3 can be irreversibly converted to Pb3(SeO3)2Cl2 with a concomitant loss of HCl.

Synthesis and characterization of meso-[Ru(NO)Cl(dioxocyclam)] and the 1H NMR comparison with [M II(dioxocyclam)] complexes (M II=Ni II and Pd II) (dioxocyclam=1,4,8,11-tetraazacyclotetradecane-5,7-dione)

trans-[Ru(NO)X(dioxocyclam)], X=Cl − and OH −, dioxocyclam=(1,4,8,11-tetraazacyclotetradecane-5,7-dione) have been prepared and characterized by NMR, IR and ESI-MS techniques. The trans-[Ru(NO)Cl(dioxocyclam)] shows the nitrosyl stretch at 1846 versus 1875 cm −1 in the cyclam analogue, indicative of strong π-donation from the deprotonated dioxocyclam ligand to the Ru II center and, in turn, to the NO + group. Upon coordination, the dioxocyclam ligand no longer undergoes facile H/D exchange of the NH and C-6 protons. The methylene protons exist in symmetric patterns indicative of the meso isomer with both C-12 and C-14 methylene carbons projecting below the RuN 4 plane toward the side of the axial Cl − for the major product. A lesser amount of the rac isomer, wherein the C-12 and C-14 methylene carbons reside on opposite sides of the RuN 4 coordination plane, is detected. mmff94 calculations determined that the meso form is more stable than rac by 3.33 kcal mol −1. The Ru II–N(amide) bonds were calculated as having normal lengths (2.07 Å), but the calculated Ru II–N(amine) bonds are elongated to 2.35 and 2.36 Å. (It is known that molecular mechanics can overestimate bond lengths for second and third row metal centers by 0.10–0.15 Å). Even after correcting for the over-calculated bond distance factor, it is seen that the amine–ruthenium distances are longer, and hence the bonds are weaker, than for ‘normal’ Ru II–amines. The presence of the axial Cl − is established by the ESI-MS ion fragments at m/ z=394 for {d 2-[Ru(NO)Cl(dioxocyclam)]H} +. Ions for {[Ru(NO)(H 2O)(dioxocyclam)]} + ( m/ z=377) and {[Ru(NO)(dioxocyclam)]} + ( m/ z=359), the latter from loss of HCl or H 2O from the 394 and 377 ions, are detected. 1H and 13C NMR data for meso-[Ru(NO)Cl(dioxocyclam)] are compared to the meso-[Pd II(dioxocyclam)] complex, and to the Ni II derivative that was synthesized at lower temperature than in previous literature reports. The meso-[Ni II(dioxocylam)] complex was identified previously. In the present work, it is shown that below 50°C the product for the Ni II system is rac-[Ni II(dioxocyclam)]. The assignments for the {Ru(NO)} 3+, Ni II and Pd II dioxocyclam complexes as having the dominant isomeric forms as meso for {Ru(NO)} 3+ and Pd II, and rac for Ni II are supported by the H–H COSY spectrum for {RuNO)} 3+, H–H and C–H COSY spectra for Ni II and the H–H COSY spectrum for Pd II derivatives.

Hazards of dichlorosilane exhaust deposits from the high-temperature oxide process as determined by FT-ICR mass spectrometry

Gas samples from the exhaust system of tools employing dichlorosilane (DCS) in high temperature oxide (HTO) deposition that produced flammable solid deposits have been analyzed by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. Exact mass determinations by the high-resolution FT-ICR allowed the identification of various polysiloxane species present in such an exhaust flow. Ion-molecule reactions of dichlorosilyl cation with water and DCS indicate the preferred reaction pathway is disiloxane formation through HCl loss, a precursor to the highly flammable polysiloxanes that were identified in the gaseous exhaust and in exhaust deposits. Minimization of these hazardous deposits is discussed with respect to water contamination, dilution factor and water scrubbing of the HTO exhaust.

Doping of 2-Cl-PANI/PVC films by exposure to UV, γ-rays and e-beams

2-Chloro-polyaniline (2-Cl-PANI) is chemically prepared in its non-conducting (Emeraldine Base, EB) form and dissolved together with polyvinylchloride (PVC) in THF for casting into thin (10–50 μm) composite films. The electrical conductivity of these films increases by more than four orders of magnitude (from 10 −6 to 10 −2 S/cm) when they are exposed to UV, γ-rays and e-beams. This is attributed to the dehydrochlorination (loss of HCl) of PVC by exposure to energetic particles and subsequent doping of the 2-Cl-PANI (i.e., conversion to Emeraldine Salt, ES) by the in-situ-created HCl. The doped films can also be returned to their undoped form by further exposure to NH 3 vapours. The UV (or other particles)-induced doping/NH 3 undoping cycles can be repeated several times until almost total dehydrochlorination of the PVC matrix. UV–Vis–NIR, Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopic (XPS) techniques are employed to follow the changes in the composite films upon doping by exposure to these energetic particles.

Molecular Beam Studies of HCl Interactions with Pure and HCl-Covered Ice Surfaces

The dynamics of HCl collisions with ice surfaces is studied using molecular beam techniques. The experiments are carried out with a water vapor pressure of up to 3 × 10-5 mbar outside the ice surface, which allows experiments to be performed at surface temperatures of 127−180 K. At the higher surface temperatures, the ice has a very dynamic character and constantly undergoes evaporation and condensation. Angular-resolved intensity and time-of-flight distributions are measured with mass spectrometry, and the effects of surface temperature, incident kinetic energy, and HCl surface coverage are investigated. The dominating outcome of the surface interaction is loss of HCl by sticking to the surface with a residence time of more than 1 ms. Small direct scattering and trapping-desorption channels are also observed depending on the conditions. For a pure ice surface the sticking probability is 1.00 ± 0.02 at thermal incident kinetic energies, E, while a small direct scattering channel is observed when E is incr...

Collision‐induced dissociation of corticosteroids in electrospray tandem mass spectrometry and development of a screening method by high performance liquid chromatography/tandem mass spectrometry

A screening method based on liquid chromatography/electrospray tandem mass spectrometry was developed in order to control the illegal use of corticosteroids as growth promoters in cattle. The objective was the detection of low residue levels of corticosteroids or metabolites in biological matrices. Relative to other studies published on this subject, the present work focused on enhancing specificity and sensitivity. Firstly, fragmentation of corticosteroids by collision-induced dissociation was studied. In positive mode, the losses of H2O for each hydroxyl group fixed on the molecule, as well as the loss of HF or HCl for halogenated compounds, were observed. For higher collision energy, fragmentations in the B, C and D rings were induced. The negative mode was found to be more specific, inducing a cleavage of the C20–C21 bond with concomitant loss of formaldehyde (CH2O). Secondly, three acquisition methods in the negative mode were studied and evaluated, recorded signals being the parent ion [M + acetate]− and the two daughter ions, [M − H]− and [M − H − CH2O]−. For dexamethasone, MS/MS instrumental detection limits of fragment ion and neutral loss scans, and of multiple reaction monitoring (MRM), were 250, 20 and 5 pg injected, respectively. The MRM method was then evaluated with the objective of use for the detection of corticosteroid residues in biological samples (urine, hair, muscle) and for a metabolism study. Copyright © 2000 John Wiley & Sons, Ltd.

Use of pyrolysis–g.c.–m.s. to assess the thermal degradation behaviour of polymers containing chlorineI. The limits of detection and measurement of HCl, deduced from a study of PVC pyrolysis

From measurements of the yields of hydrogen chloride evolved from the thermal degradation of PVC samples, it is deduced that the authors' pyrolysis–gas chromatography–mass spectrometry equipment can detect HCl down to at least 50 ng (1.4 nanomoles). The actual limit is almost certainly smaller, because the calculations assume that HCl is obtained in quantitative yield from PVC on prolonged pyrolysis at 250°C. (Additional sensitivity may also be available by more specialised operation of the mass spectrometer in single ion monitoring mode, but the present work relates to the normal scanning mode used in general analysis). The above measured detection limit is more than 4000 times better than that obtained using g.c. equipment incorporating packed columns and a thermal conductivity detector, because with the latter apparatus there is substantial loss of HCl, probably due to reaction with the column packing. The prolysis–g.c.–m.s. results also provide an absolute sensitivity calibration for HCl, and in addition, permit calculation of the rate constant (specific rate, k) for HCl evolution from PVC at 250°C. The value of k, as calculated from the initial rate, is found to be ca. 5×10 −3 s −1 at 250°C, and is independent of sample size over the range 10–40 micrograms (corresponding to sample thickness 2.5–10 microns on the pyrolysis filament). For samples of 30–40 micrograms, the specific rate increases with conversion to a value in the final stages which is approximately double that of the initial value. This phenomenon is consistent with an autoaccelerative mechanism in which HCl production is promoted by HCl itself, with the residence time for HCl increasing with both the sample size and the degree of cross-linking of the residue.

Electron-Deficient Early−Late Heterobimetallic Sulfido Clusters. Unusual Reactivities of Ti2Ru2S4 Cubane-Type Clusters with Four Cyclopentadienyl Coligands

Treatment of [Cp2Ti(SH)2] (1; Cp = η5-C5H5) with [(Cp*Ru)4(μ3-Cl)4] (2; Cp* = η5-C5Me5) in a Ti:Ru ratio of 1:1 afforded the hydrosulfido-bridged titanium−ruthenium heterobimetallic complex [Cp2Ti(μ2-SH)2RuClCp*] (3). Complex 3 reacted with an excess of triethylamine to give the early−late heterobimetallic cubane-type sulfido cluster [(CpTi)2(Cp*Ru)2(μ3-S)4] (4), with a loss of HCl and cyclopentadiene. An X-ray diffraction study and extended Hückel molecular orbital calculations for the 60e- cluster 4 demonstrated that 4 has four Ru→Ti dative bonds and a weak Ti−Ti interaction. The reaction of 4 with 3 equiv of [Cp2Fe][PF6] afforded the dicationic cubane-type cluster [(CpTi)2(Cp*Ru)2(μ3-S)4][PF6]2 (5), which contains an additional Ru−Ru bond. In contrast, oxidation of 4 with an excess of HCl at room temperature resulted in the formation of the neutral dichloride cluster [(CpTiCl2)(CpTi)(Cp*Ru)2(μ3-S)4] (6). Clusters 5 and 6 were converted into each other by treatment with chloride or hexafluorophosphate anion. Furthermore, substitution of one of the cyclopentadienyl ligands in 6 by a chloride anion took place in boiling 1,2-dichloroethane to give the trichloride cluster [(TiCl3)(CpTi)(Cp*Ru)2(μ3-S)4] (7). The detailed structures of these oxidized cubane-type clusters 5·2DMF, 6·CH2Cl2, and 7·CH2Cl2 as well as the hydrosulfido-bridged dinuclear complex 3 have also been determined by X-ray crystallography. The Ti2Ru2S4 cubane-type cores in 5−7 differ considerably in structure from each other, depending upon the ancillary ligands bound to the Ti atoms, although they have a Ru−Ru bond and two Ru→Ti dative bonds in common.