Acid deposition probes

Acid deposition probes that are used generally to determine the acid dew point of combustion gases, i.e. the temperature at which acid condensation occurs, usually near the flue gas exit where the temperature is relatively low. Acid dew point temperatures are often in the region of 120 C for most flue gases. 

It has been observed in this laboratory, as in many others, that compounds, which volatilize from the mass spectrometer direct insertion probe at a certain temperature under electron impact conditions, will often volatilize at a lower temperature (50°C or more) if the analysis is carried out under chemical ionization conditions with reagent gas sweeping around the probe tip and then into the source. For sulfuric acid deposited on a Fluoropore filter, a decrease in volatilization temperature of approximately 70°C has been observed for sulfuric acid when the analysis is carried out in the chemical ionization mode. The elution profile is sharper and better defined than that obtained under electron impact conditions. 

Alexander et al [1960] used an air cooled probe to measure acid deposition in oil fired boilers, with the air discharge directly into the flue gas stream. The probe was 2.5 w long x 25 mm in diameter. In a particular test the temperature along the probe wall varied from 80 to 170°C. At temperatures below 94°C the probe surface was damp and analysis of the deposit formed showed that it consisted of metal sulphates suggesting that corrosion of the test surface had occurred. 

Alexander, P.A., Fielder, R.S., Jackson, P. and Raask, E., 1960, An air cooled probe for measuring acid deposition in boiler flue gases. J. Inst. Fuel, 33, 31-37. 

Microarray A microscopic, ordered array of nucleic acids, proteins, small molecules, cells, or other substances that enables parallel analysis of complex biochemical samples. The term microarray originally referred to spotted cDNA arrays, but now others and we use it for any hybridization-based array. The major characteristics of microarrays are that they have a glass or plastic slide as a matrix, and are created with robots that deposit probes on the slides. 

Aqueous solutions of ammonium sulfate and ammonium bisulfate were deposited on Fluoropore filters, placed in the direct insertion probe, and analyzed in the chemical ionization mode (H2O reagent) gas. The samples were heated from 100°C to 330 C at 15 C/minute. No sample ions were observed under these anlaysis conditions, even when several micrograms of ammonium salts were analyzed. The thermal decomposition of ammonium salts of sulfate has been the subject of many studies. (29,30) Some pathways include sulfuric acid production at one stage of the decomposition while others suggest ammonia, SO2 and SO3 are the products. None of these accurately simulate the conditions (temperature, pressure, gas flow) present in our chemical ionization source. However, no sulfuric acid ions (H3SO4+, etc.) were ob-served... 

No direct method exists by which monolayer film structures on water can be studied. Therefore, the LB method has been used to study molecular structures in past decades. The most useful method for investigating the detailed LB-deposited film structure is the well-known electron diffraction technique (or the scanning probe microscope [Birdi, 2002a]). The molecular arrangements of deposited mono-and multilayer films of fatty acids and their salts, using this technique, have been reported. The analyses showed that the molecules were almost perpendicular to the solid surface in the first monolayer. It was also reported that Ba-stearate molecules have a more precise normal alignment compared to stearic-acid monolayers. In some investigations, the thermal stability of these films has been found to be remarkably stable up to 90°C. 

Extensive studies of the acidity and basicity of zeolites by adsorption calorimetry have been carried out over the past decades, and many reviews have been published [62,64,103,118,120,121,145,146,153,154]. For a given zeolite, different factors can modify its acidity and acid strength the size and strength of the probe molecule, the adsorption temperature, the morphology and crystallinity, the synthesis mode, the effect of pretreatment, the effect of the proton exchange level, the Si/Al ratio and dealumination, the isomorphous substitution, chemical modifications, aging, and coke deposits. 

The process of Pb deposition depends on the presence of adsorbed species. On polycrystalline gold, in HCIO4 acid solutions, a combined quartz crystal microbalance and probe beam deflection methods have pointed to three stages of the process - (1) water molecules release from gold surface, (2) metal UPD associated with adsorbed OH ions replacement, followed by (3) water formation [274]. In the presence of adsorbed anions or organic... 

An array of oligonucleotide which is composed of 20 80-mer oligos, or peptide nucleic acid probes, is synthesized either in situ (i.e., on-chip) or using conventional synthesis followed by on-chip immobilization. The resultant DNA array is then exposed to the labeled sample of DNA, hybridized, and the identity/abundance of complementary sequences determined. This method was developed at Affymetrix, Inc. and called DNA chips. Today, oligonucleotide-based chips are manufactured by many companies using alternative in situ synthesis or depositioning technologies. 

Solid samples that have a sufficient vapour pressure at 300 °C are deposited on the tip of a heated metal probe which is then inserted into the instrument through a vacuum lock. With some ionisation methods, the solid sample is mixed with a liquid matrix (e.g. glycerol or benzoic acid). 

Comyn [1] has pointed out that maximum bond strength and consequently greater adhesion between the substrate and polymer could be achieved with a monolayer of silane bound to both the adherend and adhesive. The current investigation was undertaken to evaluate the possibility of monolayer level depositions on silicon substrates by employing a few w -functionalized alkanoyl-substituted derivatives of APTES which will provide polar moieties as well. The interactions of these functionalized silanes covalently immobilized on silicon with octadecylamine and octadecanoic acid, used as models for basic and acidic polymeric adhesives, were also examined in this study. Characterization of the silanized surfaces as well as studies on their interactions with the above two chemical probes were carried out through ellipsometric and XPS measurements. 

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