Potential use of Methylibium sp. as a biodegradation tool in organosilicon and volatile compounds removal for biogas upgrading

Organosilicon compounds are the most undesirable compounds for the energy recovery of biogas. These compounds are still resistant to biodegradation when biotechnologies are considered for biogas purification. Herein we isolated 52 bacterial species from anaerobic batch enrichment cultures (BEC) saturated with D4 and from an anaerobic lab-scale biotrickling filter (BTF) fed with a gas flow containing D4 as unique carbon source. Among those Methylibium sp. and Pseudomonas aeruginosa showed the highest capacity to remove D4 (53.04% ± 0.03 and 24.42% ± 0.02, respectively). Contrarily, co-culture evaluation treatment for the biodegradation of siloxanes together with volatile organic compounds removed a lower concentration of D4 compared to toluene and limonene, which were completely removed. Remarkably, the siloxane D5 proved to be more biodegradable than D4. Substrates removal values achieved by Methylibium sp. suggested that this bacterial isolate could be used in biological removal technologies of siloxanes.

29Si-1H IMPACT HMBC: a suitable tool for analyzing silylated derivatives

A modified version of the IMPACT heteronuclear multiple bond correlation (HMBC) has allowed the characterization of an organosilane and a tetrasilylated yttrium complex. With the help of this sequence, an average gain in sensitivity close to 2 has been obtained compared with the standard HMBC experiment for disilanes as well as for yttrium complexes containing silylated ligands. This modified version of this long-range correlation experiment opens the way for following kinetics in the range of a fraction of a minute and to study by NMR low concentrated samples and low abundant nuclei.

Para-hydrogen induced polarization of Si-29 NMR resonances as a potentially useful tool for analytical applications

Para-hydrogen-induced polarization effects have been observed in the (29)Si NMR spectra of trimethylsilyl para-hydrogenated molecules. The high signal enhancements and the long T(1) values observed for the (29)Si hyperpolarized resonances point toward the possibility of using (29)Si for hyperpolarization applications. A method for the discrimination of multiple compounds and/or complex mixtures of hydroxylic compounds (such as steroids), consisting of the silylization of alcoholic functionalities with an unsaturated silylalkyl moiety and subsequent reaction with para-H(2), is proposed.

Determination of descriptors for organosilicon compounds by gas chromatography and non-aqueous liquid–liquid partitioning

Measurements of retention factors by gas chromatography on up to 10 complementary stationary phases at up to 5 temperatures for each stationary phase and liquid-liquid partition coefficients in three biphasic organic solvent systems (n-hexane-acetonitrile, n-heptane-N,N-dimethylformamide and n-heptane-2,2,2-trifluoroethanol) were used to estimate solute descriptors for 54 organosilicon compounds for use in the solvation parameter model. Many of the E descriptor values (electron lone pair interactions) are negative for simple siloxanes and silanes indicating that these compound bind electron lone pairs more tightly than n-alkanes. Silanes and siloxanes with alkyl groups have near zero dipolarity/polarizability (S descriptor). The S descriptor is only modest for simple phenylsilanes, silazanes, silanols, orthosilicates, and alkoxides. All organosilicon compounds with silicon-oxygen bonds are reasonably strong hydrogen-bond bases (B descriptor) but only the silanol group is a reasonably strong hydrogen-bond acid (A descriptor). Silanes (SiH) and silazanes (SiNHSi) are weak hydrogen-bond acids. Cavity formation and dispersion interactions (V or L descriptor) are often the main component of solvation models for siloxanes and silanes that have simple alkyl and aromatic substituents. A number of physicochemical properties (vapor pressure, aqueous solubility, biphasic partition coefficients, sorption coefficients, etc.) for linear and cyclic dimethylsiloxanes can be reliably predicted from their descriptors in established models for organic compounds.

Liquid-chromatographic separation and determination of process-related impurities, including a regio-specific isomer of celecoxib on reversed-phase C18 column dynamically coated with hexamethyldisilazane

A simple and rapid reversed-phase high-performance liquid-chromatographic method for the separation and determination of process-related impurities of celecoxib (CXB) in bulk drugs and pharmaceuticals was developed. The separation of impurities viz., 4-methylacetophenone (I), 1-(4-methylphenyl)-4,4,4-trifluorobutane-1,3-dione (II), 4-hydrazinobenzene sulfonamide (III) and a regio-specific isomer [3-(4-methylphenyl)-5-trifluoromethyl-1H-pyrazole-1-yl]-benzenesulfonamide (IV), was accomplished on an Inertsil ODS-3 column dynamically coated with 0.1% hexamethyldisilazane (HMDS) in acetonitrile:water (55:45 v/v) as a mobile phase and detection at 242 nm using PDA at ambient temperature. The chromatographic conditions were optimized by studying the effects of HMDS, an organic modifier, time of silanization and column temperature. The method was validated and found to be suitable not only for monitoring the synthetic reactions, but also to evaluate the quality of CXB.

Derivatization of organophosphorus nerve agent degradation products for gas chromatography with ICPMS and TOF-MS detection

Separation and detection of seven V-type (venomous) and G-type (German) organophosphorus nerve agent degradation products by gas chromatography with inductively coupled plasma mass spectrometry (GC-ICPMS) is described. The nonvolatile alkyl phosphonic acid degradation products of interest included ethyl methylphosphonic acid (EMPA, VX acid), isopropyl methylphosphonic acid (IMPA, GB acid), ethyl hydrogen dimethylamidophosphate sodium salt (EDPA, GA acid), isobutyl hydrogen methylphosphonate (IBMPA, RVX acid), as well as pinacolyl methylphosphonic acid (PMPA), methylphosphonic acid (MPA), and cyclohexyl methylphosphonic acid (CMPA, GF acid). N-(tert-Butyldimethylsilyl)-N-methyltrifluroacetamide with 1% TBDMSCl was utilized to form the volatile TBDMS derivatives of the nerve agent degradation products for separation by GC. Exact mass confirmation of the formation of six of the TBDMS derivatives was obtained by GC-time of flight mass spectrometry (TOF-MS). The method developed here allowed for the separation and detection of all seven TBDMS derivatives as well as phosphate in less than ten minutes. Detection limits for the developed method were less than 5 pg with retention times and peak area precisions of less than 0.01 and 6%, respectively. This method was successfully applied to river water and soil matrices. To date this is the first work describing the analysis of chemical warfare agent (CWA) degradation products by GC-ICPMS.

Investigation of thermodynamic properties of poly(methyl methacrylate-co-n-butylacrylate-co-cyclopentyl styryl-polyhedral oligomeric silsesquioxane) by inverse gas chromatography

The thermodynamic properties of poly(methyl methacrylate-co-butyl acrylate-co-cyclo -pentylstyryl polyhedral oligomeric silsesquioxane) (poly(MMA-co-BA-co-styryl-POSS)) were investigated by means of inverse gas chromatography (IGC) using 20 different kinds of solvents as the probes. Some thermodynamic parameters, such as molar heats of sorption, weight fraction activity coefficient, Flory-Huggins interaction parameter, partial molar heats of mixing and solubility parameter were obtained to judge the interactions between POSS-contained polymers and solvents and the solubility of the polymers in these solvents. It was found that acetates, aromatic hydrocarbons and hydrocarbon halides were good solvents, n-hexane, ethanol, n-propanol, n-butanol and n-pentanol were moderate solvents, while n-heptane, n-octane, n-nonane, n-decane and methanol were poor solvents for all POSS-contained polymers within the experimental temperature range. Incorporation of POSS in polymer increased the solubility of polymers in solvents, and the more the POSS in polymer was, the better the solubility was and stronger the hydrogen bonding interaction was, but the POSS content in polymers seemed to have no obvious influence on the solubility parameter of polymers.

Characterization of a single molecular QCA cell by Q-control enhanced amplitude modulation atomic force microscopy

Major technical challenges for reduction of device sizes for computation and memory are the interconnection and power dissipation problems. Molecular quantum-dot cellular automata (QCA) have been proposed as solutions to this problem. Silicon phthalocyanine (SiPc) is a possible candidate for a molecular QCA element. Therefore, it is important to develop an in situ observation technique to visualize individual SiPc molecules. We report here the first image of a single SiPc dimer in air by using quality factor control (Q-control) enhanced amplitude modulation atomic force microscopy (AFM) and an investigation of the interaction forces between the tip and SiPc dimer. The AFM was operated at 0% relative humidity in an ultrapure nitrogen environment either with or without Q-control. Theoretical simulations using the point-mass description of the AFM, demonstrated that Q-enhancement reduced the force exerted from the tip to the sample surface. Our results, consistent with theory, demonstrated that the image force was reduced and a greater height and a larger size were measured. The advantages of this method can be extended to the AFM observation of other "soft" structures, and these results can be useful for a wider community.

Analysis of tert-butyldimethylsilyl derivatives in heavy gas oil from brazilian naphthenic acids by gas chromatography coupled to mass spectrometry with electron impact ionization

Naphthenic acids, C(n)H(2n+Z)O(2), are a complex mixture of alkyl-substituted acyclic and cycle-aliphatic carboxylic acids. The content of naphthenic acids and their derivatives in crude oils is very small, which hinders their extraction from matrixes of wide and varied composition. In this work, liquid-liquid extraction, followed by solid phase extraction with an ion exchange resin (Amberlyst A-27) and ultrasound desorption were used to isolate the acid fraction from heavy gas oil of Marlim petroleum (Campos, Rio de Janeiro, Brazil). The analysis was accomplished through gas chromatography coupled to mass spectrometry with electron impact ionization, after derivatization with N-methyl-N-(tert-butyldimethylsilyl)trifluoracetamide (MTBDMSTFA). The results indicate the presence of carboxylic acids belonging to families of alicyclic and naphthenic compounds which contain up to four rings in the molecule.

Neurochemical analysis of amino acids, polyamines and carboxylic acids: GC-MS quantitation of tBDMS derivatives using ammonia positive chemical ionization

The GC-MS quantitation of a large number of neurochemicals utilizing a single derivatization step is not common but is provided by the reagent N-(tert-butyldimethylsilyl)-N-methyltrifluro-acetamide (MTBSTFA). Previous workers have utilized this derivative for GC-MS analyses of amino acids, carboxylic acids and urea with electron impact (EI) and with positive chemical ionization (PCI; methane as reagent gas). However, these conditions yield significant fragmentation, decreasing sensitivity and in some cases reducing specificity for quantitation with selected ion monitoring (SIM). Additionally, the majority of studies have used a single internal standard to quantitate many compounds. In this study we demonstrate that using isotopic dilution combined with ammonia as the reagent gas for PCI analyses, results in high precision and sensitivity in analyzing complex neurochemical mixes. We also demonstrate for the first time the utility of this derivative for the analysis of brain polyamines and the dipeptide cysteinyl glycine. In the case of ammonia as the reagent gas, all amino acids, polyamines and urea yielded strong [MH](+) ions with little or no fragmentation. In the case of carboxylic acids, [M+18](+) ions predominated but [MH](+) ions were also noted. This approach was used to analyze superfusates from hippocampal brain slices and brain tissue extracts from brain lesion studies. The advantages of this methodology include: (i) simple sample preparation; (ii) a single derivatization step; (iii) direct GC-MS analysis of the reaction mix; (iv) high precision as a result of isotopic dilution analyses; (v) high sensitivity and specificity as a result of strong [MH](+) ions with ammonia reagent gas; (vi) no hydrolysis of glutamine to glutamate or asparagine to aspartate; and (vii) applicability to a wide range of neurochemicals.

[A silicon phthalocyanine axially substituted by nipagin: synthesis, molecular spectroscopic properties, and in vitro photodynamic activities]

A new silicon phthalocyanine axially substituted by Nipagin, i.e. bis(4-methoxycarboxyl phenoxy)phthalocyaninatosilicon, has been synthesized and characterized by IR, NMR, HPLC and elemental analysis. Its electronic absorption spectra and fluorescence spectra in different solvents were investigated. It was found that the compound existed in the form of monomer in a saline solution containing 2% (phi) Cremophor EL and 20% (phi) propanediol. The electronic absorption spectra of the compound in the above saline solution were typical for non-aggregated phthalocyanines, showing an intense and sharp Q band at 683 nm with a molar absorption coefficient of 7.47 x 10(4) mol(-1) x L x cm(-1). The compound exhibited a relatively strong fluorescence emission at 690 nm with a quantum yield of 0.34 and with a fluorescence lifetime of 4.7 ns. The primary in vitro assay showed the compound had photodynamic killing activities against B16 melanoma cells with a LD50(half lethal dose) of 1.2 x 10(-4) mol x L(-1).

Determination of 14 benzodiazepines and hydroxy metabolites, zaleplon and zolpidem as tert-butyldimethylsilyl derivatives compared with other common silylating reagents in whole blood by gas chromatography–mass spectrometry

The most common commercially available silylating reagents, N-methyl-N-(trimethylsilyl)trifluoroacetamide (MSTFA), N,O-bis-(trimethylsilyl)trifluoroacetamide+1% trimethylchlorosilane (BSTFA+1% TMCS) and N-methyl-N-(tert-butyldimethylsilyl)trifluoroacetamide (MTBSTFA) were evaluated to achieve optimal derivatization conditions for analyzing various benzodiazepines based on gas chromatography-electron impact ionization-mass spectrometry (GC-EI-MS). Sensitivity, repeatability, retention times and stability of the derivatives, as well as specificity of mass fragmentation, were studied in detail. Also other parameters affecting the derivatization chemistry of benzodiazepines are discussed. tert-Butyldimethylsilyl (TBDMS) derivatives proved to be more stable, reproducible and sensitive than corresponding trimethylsilyl (TMS) derivatives for the GC-EI-MS analysis of benzodiazepines. Based on the TBDMS derivatives, a rapid, reliable, sensitive and quantitative GC-MS method was developed for the determination of 14 benzodiazepines and two hydroxy metabolites, as well as two non-benzodiazepine hypnotic agents, zolpidem and zaleplon, using 50 microl of whole blood. The method was completely validated in terms of accuracy, intra- and interday precision, limit of detection (LOD), limit of quantitation (LOQ), linearity, selectivity and extraction efficiency; these were all within the required limits, except for the accuracy of nitrazepam at a medium concentration level.

Syntheses of Silatranyl- and Germatranyluridines

[reaction: see text] Silatranyluridine 1 and germatranyluridine 2 have been prepared in five steps from oxazolinouridine 3 in 27 and 29% yields, respectively. These compounds are novel transition-state analogues (TSAs) for RNA hydrolysis and offer a number of advantages over traditional vanadium- or rhenium-based TSAs. Germatrane 2 is completely stable in D(2)O at room temperature, and the half-life of silatrane 1 in D(2)O was found to be >7 days by (1)H NMR spectroscopy.

Evaluation of the analyses of tert-butyldimethylsilyl derivatives of naphthenic acids by gas chromatography–electron impact mass spectrometry

Naphthenic acids are a complex mixture of carboxylic acids with the general formula CnH(2n+Z)O2 and they are natural, toxic components of crude oils. GC-MS analyses of tert-butyldimethylsilyl esters of naphthenic acids are used to estimate component distribution within naphthenic acids mixtures. Our evaluations of the GC-MS method showed that ions from column bleed erroneously appear as C14 Z = -4 acids and that correcting for heavy isotopes of C and Si do not significantly affect ion distribution plots. Overall, the GC-MS method appears to overestimate the relative proportion of low-molecular-mass acids.

Detection of C-Si covalent bond in CH3 adsorbate formed by chemical reaction of CH3MgBr and H:Si(111)

High-resolution electron energy loss spectroscopy (HREELS) yielded evidence for the formation of single covalent bonds between Si(111) surface atoms and CH(3) groups from the reaction of CH(3)MgBr and hydrogen-terminated H:Si(111)(1 x 1). The vibration at 678 cm(-)(1), assigned to the C-Si bond, was isolated within the spectrum of CH(3) on deuterium-terminated D:Si(111)(1 x 1). The CH(3) groups were thermally stable at temperatures below 600 K. The C-Si bonds are essential for enhancing the usefulness of alkyl moieties, which will lead to a new prospective technology of nanoscale fabrication and biochemical application.

[Effects of rice cleaning and cooking process on the residues of flutolanil, fenobucarb, silafluofen and buprofezin in rice]

We studied the effect of cleaning and cooking on the residues of flutolanil, fenobucarb, silafluofen and buprofezin in rice. The rice had been sprayed in a paddy field in Wakayama city, with 3 kinds of pesticide application protocols: spraying once at the usual concentration of pesticides, repeated spraying (3 times) with the usual concentration of pesticides and spraying once with 3 times the usual concentration of pesticides. The residue levels of pesticide decreased during the rice cleaning process. Silafluofen, which has a higher log Pow value, remained in the hull of the rice. Fenobucarb, which has a lower log Pow value, penetrated inside the rice. The residue concentration of pesticide in polished rice was higher than that in pre-washed rice processed ready for cooking. During the cooking procedure, the reduction of pesticides in polished rice was higher than that in brown rice.

[Silicon forms and its role in infant food]

This paper presents an attempt to assess the total content of silicon and its potentially bioavailable forms to the baby body in milk nutrient and baby foods. The measurements of the total and bioavailable silicon were conducted with the use of two analytical methods. The method of atomic absorption spectroscopy (AAS) was used for the determination of total silicon content. Bioavailable silicon was determined by means of visible light spectroscopy (VIS) with ammonium molybdate. In the group milk products the largest amount of total silicon was found in Mlekovita milk -0.54 mg/l, and Humana 2 milk formula contained the largest amount of ionised silicon-0.24 mg/l. In baby foods manufactured by Gerber the total amount of silicon was high and the average content stood at 27 mg/kg in dry matter. The largest amount of total silicon was found in Vegetables and Ham-48.19 mg/kg in dry matter, as well as bioavailable silicon--4.13 mg/kg in dry matter. Compare level of silicon in milk nutrient and baby foods to silicon content in human milk 0.05 mg/l, it was found that large excess of silicon in this foodstuffs.

New selective method for quantification of organosilanol groups in silicone pre-elastomers

The silicone elastomers used for drug delivery are normally reinforced by fumed silica, which contains a high density of silanol groups. These inorganic silanol groups have to be deactivated in order to avoid stiffening the uncured pre-elastomer, also called creep hardening. One commonly used way of achieving this deactivation is to mix the material with low molecular mass organosilanols at an elevated temperature. It is important to be able to quantify the nonbonded organosilanols remaining in the material after manufacture. Traditional testing does not distinguish between inorganic silanols and organosilanols. A new selective method for the quantification of organosilanol groups in silicone pre-elastomers has therefore been developed. This method is based on derivatization of the silanol groups with a mixture of dimethylphenylchlorosilane and tetramethyldiphenylsilazane, so that the silanol groups are replaced with a dimethylphenyl group. The derivatized organosilanols are then determined by liquid chromatography using a size exclusion column and a UV detector. No interference was found from other groups normally present in medical grade pre-elastomers, such as vinyls, hydrides, and inorganic bonded silanol on silica or water. The results agreed well with the nonselective Karl Fischer titration for some short chain silanols.

Computerised gas chromatographic-mass spectrometric analysis of complex mixtures of alkyl porphyrins

Computerised capillary gas chromatography-mass spectrometry (GC-MS) analysis of complex mixtures of alkyl porphyrins, as their bis-(trimethylsiloxy)silicon(IV) and bis(tert.-butyldimethylsiloxy)silicon(IV) derivatives, is described. The latter derivative is more suitable for routine GC-MS analysis. This computerised GC-MS approach, when applied to the alkyl porphyrins of two geological samples, a bitumen (Gilsonite, Eocene age, UT, U.S.A.) and a crude oil (Boscan, Cretaceous age, West Venezuela), has revealed the highly complex compositions of these fractions. Computer-aided data processing, using relative retention index (RRI) calculations, facilitated the classification of the chromatographic peaks according to structural type and membership of pseudo-homologous series. Computerised GC-MS is compared with, and contrasted to high-performance liquid chromatography as a means of petroporphyrin analysis.

New hydrolysis method for extremely small amount of lipids and capillary gas chromatographic analysis as n(O)-tert.-butyldimethylsilyl fatty acid derivatives compared with methyl ester derivatives

The organic basic solution, 1 M tetramethylammonium hydroxide (TMAH) in methanol, was employed for the hydrolysis of extremely small amounts of lipids compared to the classical inorganic basic solution, 1 M KOH in ethanol. The hydrolysed fatty acids were derivatized as N(O)-tert.-butyldimethylsilyl (tBDMSi) esters with N-methyl-N-(tert.-butyldimethylsilyl) trifluoroacetamide (MTBSTFA) and compared with the classical derivatives, the methyl esters, made by the BF3-methanol method. Recoveries of fatty acids determined on the standard fatty acids and soybean oil hydrolysed with TMAH were high: about 1.1-2.1- and 2.0-5.4-times, respectively, in all fatty acids compared with the hydrolysis by KOH regardless of derivatization method. The relative standard deviations (RSDs) on the recoveries of standard fatty acids were less than 5% when hydrolysed with TMAH, regardless of derivatives, but when hydrolysed with KOH, RSDs were more than 5% for most fatty acids, especially for long-chain fatty acids. The RSDs on the recoveries of fatty acids on the soybean oil were also very high in the KOH hydrolysis. Fatty acid compositions of soybean oil were similar in the main fatty acids regardless of hydrolysis methods, but showed slightly different values, depending on the methods of derivatization. RSDs were also very high in the KOH hydrolysis. In view of these results, precision of analysis by KOH hydrolysis was very poor, so we could not rely on the data. On the other hand, the reliability of data by TMAH hydrolysis method was very high, so it is a useful new hydrolysis method for extremely small amounts of lipid samples. Both derivatives of 35 standard fatty acids were successfully separated on a HP-1 nonpolar capillary column. tBDMSi derivatives were completely resolved in 70 min by 295 degrees C. In the methyl ester derivatives it took about 80 min to get satisfying resolution, but these derivatives were completely resolved by 250 degrees C. The sensitivity of tBDMSi derivatives was about 1.5-6.3-times higher than that with methyl ester derivatives. The stability of tBDMSi derivatives was constant for about 144 h except arachidic, docosahexanoic, behenic and heneicosanoic acids, which were stable for only 86 h.

Envelope structure of deeply embedded young stellar objects in the Serpens Molecular Cloud

Aperture-synthesis and single-dish (sub-) millimeter molecular-line and continuum observations reveal in great detail the envelope structure of deeply embedded young stellar objects (SMM 1 = FIRS 1, SMM 2, SMM 3, SMM 4) in the densely star-forming Serpens Molecular Cloud. SMM 1, 3, and 4 show partially resolved (>2" = 800 AU) continuum emission in the beam of the Owens Valley Millimeter Array at lambda = 3.4-1.4 mm. The continuum visibilities accurately constrain the density structure in the envelopes, which can be described by a radial power law with slope -2.0 +/- 0.5 on scales of 300 to 8000 AU. Inferred envelope masses within a radius of 8000 AU are 8.7, 3.0, and 5.3 Msolar for SMM 1, 3, and 4, respectively. A point source with 20%-30% of the total flux at 1.1 mm is required to fit the observations on long baselines, corresponding to warm envelope material within approximately 100 AU or a circumstellar disk. No continuum emission is detected interferometrically toward SMM 2, corresponding to an upper limit of 0.2 Msolar assuming Td = 24 K. The lack of any compact dust emission suggests that the SMM 2 core does not contain a central protostar. Aperture-synthesis observations of the 13CO, C18O, HCO+, H13CO+, HCN, H13CN, N2H+ 1-0, SiO 2-1, and SO 2(2)-1(1) transitions reveal compact emission toward SMM 1, 3, and 4. SMM 2 shows only a number of clumps scattered throughout the primary field of view, supporting the conclusion that this core does not contain a central star. The compact molecular emission around SMM 1, 3, and 4 traces 5"-10" (2000-4000 AU) diameter cores that correspond to the densest regions of the envelopes, as well as material directly associated with the molecular outflow. Especially prominent are the optically thick HCN and HCO+ lines that show up brightly along the walls of the outflow cavities. SO and SiO trace shocked material, where their abundances may be enhanced by 1-2 orders of magnitude over dark-cloud values. A total of 31 molecular transitions have been observed with the James Clerk Maxwell and Caltech Submillimeter telescopes in the 230, 345, 490, and 690 GHz atmospheric windows toward all four sources, containing, among others, lines of CO, HCO+, HCN, H2CO, SiO, SO, and their isotopomers. These lines show 20-30 km s-1 wide line wings, deep and narrow (1-2 km s-1) self-absorption, and 2-3 km s-1 FWHM line cores. The presence of highly excited lines like 12CO 4-3 and 6-5, 13CO 6-5, and several H2CO transitions indicates the presence of material with temperatures > or approximately 100 K. Monte Carlo calculations of the molecular excitation and line transfer show that the envelope model derived from the dust emission can successfully reproduce the observed line intensities. The depletion of CO in the cold gas is modest compared to values inferred in objects like NGC 1333 IRAS 4, suggesting that the phase of large depletions through the entire envelope is short lived and may be influenced by the local star formation density. Emission in high-excitation lines of CO and H2CO requires the presence of a small amount of approximately 100 K material, comprising less than 1% of the total envelope mass and probably associated with the outflow or the innermost region of the envelope. The derived molecular abundances in the warm (Tkin > 20 K) envelope are similar to those found toward other class 0 YSOs like IRAS 16293-2422, though some species appear enhanced toward SMM 1. Taken together, the presented observations and analysis provide the first comprehensive view of the physical and chemical structure of the envelopes of deeply embedded young stellar objects in a clustered environment on scales between 1000 and 10,000 AU.

Analysis of tert.-butyldimethylsilyl [1-13C]palmitic acid in stool samples by gas chromatography-mass spectrometry with electron impact ionisation: comparison with combustion isotope-ratio mass spectrometry

The use of 13C-labelled compounds to study lipid metabolism is increasing. Typically less than 40% of the orally administered label is recovered in breath CO2. The remainder must be either absorbed and not oxidised or not absorbed and remain in the faeces. Two methods of determining how much tracer passes through the body, and is present in the stool, were compared. Compound specific analysis of tert.-butyldimethylsilyl [13C]hexadecanoic acid by gas chromatography-mass spectrometry (GC-MS) with electron impact ionisation was compared with bulk analysis of whole stool and lipid extract by continuous flow isotope ratio mass spectrometry (CF-IRMS) with a combustion interface. The mean difference between the IRMS and GC-MS methods was -0.02 mmol 13C d(-1) with a mean excretion of 14.2 mmol 13C d(-1). Combustion IRMS is both simpler and cheaper, when the objective is to determine how much administered dose appears in stool, and information about the form of the label is not required.

Distribution of organosilicon polymers in augmentation mammaplasties at autopsy

Silicone-containing breast implants have been used since 1963 for cosmetic augmentation and breast reconstruction. Currently, there is intense debate regarding the extent and mechanism of migration of silicone from the area of implant. The current study compares tissue distribution of organosilicon polymers between women with and without silicone breast implants to determine the extent of silicone migration from breast implants. Samples were collected at autopsy from 15 individuals with bilateral breast implants with no known history of chest trauma and from 14 age- and sex-matched controls. Capsule, breast, axillary lymph nodes, abdominal fat, liver, lung, and spleen were collected for analysis of organosilicon polymers by atomic absorption spectrometry and for examination by light microscopy. Blood was collected for analysis of rheumatoid factor and antinuclear antibodies. Silicone was observed microscopically in at least one capsule section from all implant cases and in at least one lymph node in 8 of 15 implant cases. Silicone was not observed in lymph nodes from control cases. Organosilicon polymers were extracted from tissue using heptane, and the silicon content of the extract was quantitated by atomic absorption spectrometry. Silicon was detected in all capsules; statistically significant increases of organosilicon polymers were measured in axillary lymph nodes, breast, and abdominal fat from individuals with silicone breast implants when compared with the nonimplant group. Measurable amounts of organosilicon polymers were found in tissues from the nonimplant group. Suitable blood specimens were analyzed for the presence of rheumatoid factor and antinuclear antibodies. All nine implant cases tested were negative for the presence of antinuclear antibodies. Three implant cases which were tested for rheumatoid factor also were negative. We conclude that organosilicon polymers routinely migrate from the site of breast implantation to regional tissues near the implant site. Tissues from nonimplant cases often contained measurable amounts of organosilicon polymers, and tissue distribution was variable within any single individual: this is consistent with the wide-spread use and form of organosilicon polymers.

Simultaneous gas chromatographic analysis of non-protein and protein amino acids as N(O,S)-isobutyloxycarbonyl tert.-butyldimethylsilyl derivatives

A unique derivatization procedure is described for the simultaneous determination of protein and non-protein amino acids present in aqueous samples. This procedure involves N(O,S)-isobutyloxycarbonylation combined with solid-phase extraction with subsequent tert.-butyldimethylsilylation for gas chromatographic analysis. Using this combined procedure, linear responses were obtained in the range of 10-100 ppm, with correlation coefficients varying from 0.991 to 0.999, for the free amino acids studied except for homocysteine (0.922) and homoserine (0.982). The relative standard deviations ranged from 0.7 to 5% for most amino acids with a few exceptions. Temperature-programmed retention index (I) sets as measured on DB-5 and DB-17 dual-capillary columns were characteristic of each amino acid and thus useful for the screening of amino acids by computer I matching. The mass spectral patterns of amino acid derivatives, exhibiting characteristic [M-57]+, [M-113]+, [M-131]+, [M-159]+, [M-174]+ and other ions, permitted rapid structural confirmation. The present method allowed simultaneous screening of free protein and non-protein amino acids when applied to seed samples such as almond, walnut, and sunflower seeds.

Molecular and isotopic analyses of the hydroxy acids, dicarboxylic acids, and hydroxicarboxylic acids of the Murchison meteorite

The hydroxymonocarboxylic acids, dicarboxylic acids, and hydroxydicarboxylic acids of the Murchison meteorite were analyzed as their tert-butyldimethylsilyl derivatives using combined gas chromatography-mass spectrometry. The hydroxydicarboxylic acids have not been found previously in meteorites. Each class of compounds is numerous with carbon chains up to C8 or C9 and many, if not all, chain and substitution position isomers represented at each carbon number. The alpha-hydroxycarboxylic acids and alpha-hydroxydicarboxylic acids correspond structurally to many of the known meteoritic alpha-aminocarboxylic acids and alpha-aminodicarboxylic acids, a fact that supports the proposal that a Strecker synthesis was involved in the formation of both classes of compounds. Isotopic analyses show these acids to be D-rich relative to terrestrial organic compounds as expected; however, the hydroxy acids appear to be isotopically lighter than the amino acids with respect to both carbon and hydrogen. The latter finding would not be expected if both classes of compounds came exclusively from common precursors as would have been the case for a Strecker synthesis.