Samples from ng to mg in pyrolysis—gas chromatography

Samples of polystryrene, polybutadiene and poly(methyl methacrylate) were pyrolysed in amounts from nanograms to miligrams. With a gas cromatograph equipped with a flame-ionization detector it was possible to detec: 1 ng of polystryrene, 10 ng of polybutadiene and 100 ng of poly(methyl methacrylate).After the addition of microgram amounts of another substance the yield of the pyrolysis procducts from the smallest samples increased.Amounts from micrograms to milligrams were pyrolysed and unambiguous calibration graphs were obtained. The highest yields were obtained by pyrolysing repeatedly for relatively short periods until no further products were formed.     

Bowl adamanzanes--bicyclic tetraamines: syntheses and crystal structures of complexes with cobalt(III) and chelating coordinated oxo-anions

Seven cobalt(III) complexes of the macrobicyclic tetraamine ligand [2(4).3(1)]adamanzane ([2(4).3(1)]adz) are reported along with the crystal structure of six of these complexes. The solid state and solution structures are discussed, and a detailed assignment of the NMR spectra of the sulfato complex is provided. Four of the seven complexes contain a chelate coordinating oxo-anion (sulfate, formiate, nitrate, carbonate). Equilibration of these species with the corresponding diaqua complex is generally slow. The rates of equilibration in 5 mol dm(-3) perchloric acid at 25 degrees C have been measured, yielding half lives of 20 min, 10 min and 3 h for the sulfato, formiato and carbonato species respectively. The corresponding reaction for the nitrato complex occurs with a half life of less than 3 min. The concentration acid dissociation constant for the Co([2(4).3(1)]adz)(HCO(3))(2+) ion has been measured to K(a) = 0.33 mol dm(-3) [25 degrees C, I = 2 mol dm(-3)] and K(a) = 0.15 mol dm(-3) [25 degrees C, I = 5 mol dm(-3)]. The propensity for coordination of sulfate was found to be large enough for a quantitative conversion of the carbonato complex to the sulfato complex to occur in 3 mol dm(-3) triflic acid containing a small sulfate contamination. On this basis the decarboxylation in 5 mol dm(-3) triflic acid of the corresponding cobalt(III) carbonato complex of the larger macrobicyclic tetraamine ligand [3(5)]adz was reinvestigated and found to lead to the sulfato complex as well. The difference in exchange rate of the oxo-anion ligands for the cobalt(III) complexes of the two adamanzane ligands is discussed and attributed to fundamental differences in the molecular structure where an inverted configuration of the secondary non-bridged amine groups is seen for the complexes of the larger [3(5)]adz ligand. The high affinity for chelating coordination of oxo-anions for these two cobalt(iii)-adamanzane-moieties is rationalised on basis of the N-Co-N angles. N-Co-N angles are compared for a series of adamanzane complexes, and the structural consequences are discussed.     

Hybridization of binary monolayers of single stranded oligonucleotides and short blocking molecules

We have studied the immobilization of single stranded (ss) DNA oligonucleotides of 16-27 base pairs on gold. The oligonucleotides were thiol-modified (SH-ssDNA) or disulfide-modified via a dimethoxytrityl-group (DMT-S-S-ssDNA). Immobilization was performed by adsorption of the probes on the gold surface for 10-15 min, a time within which saturation coverage was obtained for both thiol- and disulfide-modified probes. Hereafter the layer was post-treated with hydroxyalkyl substituted lipoamides also for a time of 10-15 min. The surface density of layers with shorter probes (16-18 mer) was twice (2.4 ± 0.2 × 10¹³ probes/cm²) that of the longer probes (25-27 mer) as studied with surface plasmon resonance. Hybridization of single stranded polymerase chain reaction (PCR) amplified products with a length above 300 base pairs gave a very low hybridization response. For amplicons with about 100 base pairs the response was high. The surface coverage was comparable to that of complementary ssDNA binding (3.0 × 10¹² strands/cm²). Surfaces made from SH-ssDNA showed a 30% higher hybridization response than surfaces made from DMT-S-S-ssDNA. The PCR amplified products used are of relevance in breast cancer diagnosis. The results clearly demonstrate that the single stranded PCR products might be used in label-free cancer diagnostics.     

Voice Change in Seasonal Allergic Rhinitis

Voice problems are seldom reported in pollen allergy, although the allergic reaction involves the entire airways. The objective of this study was to investigate voice dysfunction during the pollen season in patients with allergic rhinitis. Thirty patients with verified birch pollen allergy and 30 controls were investigated twice, during the pollen season and outside the pollen season. Both times they scored respiratory and voice symptoms, the latter with the validated questionnaire Voice Handicap Index (VHI), and performed standardized voice recordings. These recordings were analyzed in a controlled manner by a professional voice therapist. During the allergy season, patients reported more respiratory and voice symptoms compared with controls. Those with blinded scored voice dysfunction scored their voice quality during springtime as 31 mm (95% confidence interval [CI] 20-42 mm), compared with 13 mm (95% CI 6-21 mm for participants without voice dysfunction (P<0.01). Furthermore, the group with experienced voice dysfunction scored significantly higher on the VHI in the functional and physical domains and in the total VHI score. Although voice problems during the pollen season are rarely discussed, in allergic rhinitis the larynx may also be involved. These findings support that some patients experience voice change, an experience which can be objectively confirmed.     

Spectrophotometric determination of chloride,bromide, and iodide with an improved mercury-iron-thiocyanate method

Stable reagents for the spectrophotometric mercury-iron-thiocyanate method for the determination of halide have been developed. The molar absorptivity for concentrations up to 170 μmole/liter of halide is for chloride 3.4 × 10³, for bromide 3.9 × 10³, and for iodide 4.0 × 10³. Above this concentration there is a slight decrease of the absorptivity for chloride and a slight increase for bromide and iodide.     

Water-alcohol interactions in the two-phase system water-alcohol-alkane

The system water-alcohol-alkane has been studied at 25°C as a possible model system for micelles. The solubility of water in pure alcohols and in octane in the presence of alcohol has been determined. The data suggest that water may enter the octane phase hydrogen bonded to the hydroxyl group of the alcohol. If this system has any bearing on aqueous micellar solutions, it seems possible that solubilized alcohol molecules may carry water into the micellar interior. Addition of 1,2-propanediol does not increase the water content in octane, probably because dimerization of the diol in octane is energetically more favorable than diol-water interactions.     

Synthesis, crystal structure, and H/D exchange of the inside protonated form of the cage imine 4,8,12-triaza-1-azoniatricyclo[6.6.3.2(4,12)]nonadec-1(15)-ene. A model for proton transfer through an aliphatic membrane

The reaction of the inside protonated form of the tricyclic amine 1,4,8,12-tetraazatricyclo[6.6.3.2(4,12)]nonadecane (1) with iron(III) affords the inside monoprotonated form of the corresponding imine 4,8,12-triaza-1-azoniatricyclo[6.6.3.2(4,12)]nonadec-1(15)-ene (2), which was isolated as the tetrabromozincate salt (2a) in a yield of 78%. The crystal structure of 2a has been solved by X-ray diffraction at T = 120 K. In the imine cation the acidic hydrogen atom and the lone pairs of the nitrogen atoms are oriented toward the inside of the cavity. The acidic hydrogen atom is bound to a nitrogen atom belonging to the triazacyclononane entity. The imine double bond is situated between the N-atom of the triazacyclononane entity and the C-atom belonging to one of the three trimethylene bridges. The imine 2 is stable in acidic solution and the inside coordinated proton is very robust in acidic solution. In basic solution the imine reacts fast to give a quantitative formation of the inside protonated form of the hemiaminal 1,4,8,12-tetraazatricyclo[6.6.3.2(4,12)]nonadecan-5-ol (3). The equilibrium constant K(im) = [3][H(+)]/[2] was determined at three different temperatures from potentiometric measurements, which gave K(im) = 1.57(1) x 10(-5) M at 25 degrees C, Delta S degrees = -83(1) J mol(-1) K(-)(1),and Delta H degrees = 2.6(3) kJ mol(-1) at I = 1.0 M (NaCl). The inside coordinated proton in 3 is labile in basic solution and the rate for NH/ND exchange was determined by (1)H NMR at three different temperatures. The reaction followed the expression k(obs) = k(ex)[OD(-)] with k(ex) = 0.0978(30) dm(3) mol(-1) s(-1) at 25 degrees C, Delta S(++) = 87(4) J mol(-1) K(-1), and Delta H(++) = 104.9(11) kJ mol(-1) at I = 1.0 M (NaCl). The exchange rate is more than 5 x 10(6) times faster than that of the parent saturated cage 1. This extreme enhancement of reactivity is explained by an intramolecular proton transfer reaction mediated by hydroxy and oxy groups flipping in and out of the cavity, which mechanistically has resemblance to the transport of ions in a biological system.     

Microplate-based microbial assay for risk assessment and (eco)toxic fingerprinting of chemicals

We have developed a multi-species microbial assay, MARA, for assessing the (eco)toxic risks of chemical compounds and for the determination of their toxic fingerprints. The main advantages with MARA are (1) the simultaneous testing on several microbial strains; (2) the concept of toxic fingerprinting; (3) the simple and inexpensive handling and reading of the test. The toxic activity is measured in parallel on 11 different micro-organisms lyophilised in a microplate. A concentration gradient of the chemical to be tested is added and growth is indicated through the reduction of tetrazolium red (TTC). The microplates are read by a common flatbed scanner or a microplate spectrophotometer. The array of the 11 different inhibition values constitute a toxic fingerprint, characteristic for each type of chemical compound, and it is shown that the assay can distinguish between 12 standard chemicals. Both the reproducibility (CV≈20%) and the sensitivity are similar to other toxicity tests based on micro-organisms.