Sample combustion

Standard sampling trains are specified for some tests. One of these standards is the system specified for large, stationary combustion sources (4). This train was designed for sampling combustion sources and should not be selected over a simpler sampling train when sampling noncombustion sources such as low-temperature effluents from cyclones, baghouses, filters, etc. (5). 

Ion chromatography has been successfully applied to the quantitative analysis of ions in many diverse types of industrial and environmental samples. The technique has also been valuable for microelemental analysis, e.g. for the determination of sulphur, chlorine, bromine, phosphorus and iodine as heteroatoms in solid samples. Combustion in a Schoniger oxygen flask (Section 3.31 )is a widely used method of degrading such samples, the products of combustion being absorbed in solution as anionic or cationic forms, and the solution then directly injected into the ion chromatograph. 

As mentioned above, many variants of the Dohrmann total organic carbon analyser are available, ranging from low-cost non-automated analysers based on sample combustion in a platinum boat (DC8JA) or using persulphate oxidation/ultraviolet irradiation (DC 88) to top-of-range fully automated and computerized systems based on combustion in a ceramic tube (DC 90) or combined simultaneous persulphate-ultraviolet oxidation (DC 180). Only one of these systems, the DC 180, is discussed below in any detail. 

The bomb method for sulfur determination (ASTM D129) uses sample combustion in oxygen and conversion of the sulfur to barium sulfate, which is determined by mass. This method is suitable for samples containing 0.1 to 5.0% w/w sulfur and can be used for most low-volatility petroleum products. Elements that produce residues insoluble in hydrochloric acid interfere with this method this includes aluminum, calcium, iron, lead, and silicon, plus minerals such as asbestos, mica, and silica, and an alternative method (ASTM D1552) is preferred. This method describes three procedures the sample is first pyrolyzed in either an induction furnace or a resistance furnace the sulfur is then converted to sulfur dioxide, and the sulfur dioxide is either titrated with potassium iodate-starch reagent or is analyzed by infrared spectroscopy. This method is generally suitable for samples containing from 0.06 to 8.0% w/w sulfur that distill at temperatures above 177°C (351°F). 

A test method (ASTM D5291) is available for simultaneous determination of carbon, hydrogen, and nitrogen in petroleum products and lubricants. There are at least three instrumental techniques available for this analysis, each based on different chemical principles. However, all involve sample combustion, components separation, and final detection. 

A water-cooled stainless-steel probe (4.1-millimeter internal diameter) with four inlet holes (0.50-millimeter diameter) was used to continuously sample combustion products 2 cm above the burner. The samples were drawn through an ice-bath-cooled water trap, a drying column, and a 5-micron filter to reduce the water mole-fraction and to remove particles. Temperature and static pressure in the absorption cell were monitored using a type-S thermocouple and a pressure gauge. The flow entered the cell on the same end as the optical beam and exited on the opposite end through 0.5-inch windows before... 

Figure 11.12 (a) Microstructure of the center of pure Ti sample combusted at 1.4 MPa nitrogen, indicating extensive melting and low porosity. 

Several of the minor components of coal are of importance, because of the quantity present on occasion, but more so in some cases by virtue of the special properties they possess which are undesirable when the coal is used for certain purposes. For example, to arrive at a correct figure for the combustible carbon in coal, it is necessary to apply a correction for the quantity of carbonate associated with the sample. Combustion analyses determine only the total carbon. Again, coking coals should have low phosphorus content, and anthracites used for malting should contain only very small quantities of arsenic, so that the determination of these elements becomes necessary in certain cases. Since both are found normally in small amounts, they are not included in the general statement of the ultimate analysis but are reported separately. 

Place a test sample 3cm 1 in size on an inorganic heat-insulating sheet f which is standardized to more than 10mm thickness and 12-15cm width. A small liquid petroleum gas flame 11 is brought in contact with the sample for 10 seconds 3 and is removed from the sample. Observe whether the test sample combusts with a flame or without a flame (combustion without a flame means the test sample is heated to red heat with out flame) G. If combustion is not observed, repeat this test 10 times. 

The dynamic system (also called Trace-O-Mat) was developed by Knapp et al. [181] in the early 1980s and allows sample combustion with minimum contamination. The system enables not only combustion in a closed system but also further treatment. The Trace-O-Mat combustion unit VAE-II (Kiimer, Germany) is shown in Fig. 5.13. 

A summary of some of the polymer-derived SiCN fibers is presented in Table 1. This table includes the polymer precursor systems for these fibers, the compositional data, and the developing companies. Reliable elemental analyses of these fibers are often diflScult to obtain because of incomplete sample combustion. In addition, many of these fiber compositions are being changed as their development proceeds. 

As a number of elements have their most sensitive lines at VUV wavelengths, such as N, O, P, S, Cl and H, access to the VUV region is very important, as is possible through the use of sealed spectrometers with air-tight flushed spark stands. For elements that are highly relevant metallurgically, such as C, O, H and N, efforts to lower the blank values due to the environment gases are still required to be able to replace classical C, H, N, O analyzers based on sample combustion. 

The bomb method for sulfur determination (ASTM D-129) uses sample combustion in oxygen and conversion of the sulfur to barium sulfate, which is determined by mass. This method is suitable for samples containing 0.1-5.0% w/w sulfur and can be used for most low-volatility petroleum products. Elements that produce residues insoluble in hydrochloric acid... 

BLANKS A blank is of prime importance. Many materials can produce Figure E26-1. An arson sample combustion products that look like accelerant residues. For example, glues collection container, from carpets, hydrocarbons from floor tiles, or essential oils from grasses. I once had a house fire to investigate that supposedly was set by pouring gasoline... 

However, improvements in design which increase the proportion of sample combusted and hence the detector s sensitivity have led to a resurgence of interest and detectors operating on similar principles to those elucidated above are now commercially available (Tracor Instruments) albeit at a cost. The effluent from the column is coated onto a moving quartz belt, the volatile solvent removed in vacuo and the involatile residue passed through a dual flame ionisation detector system. A number of interesting applications have been reported [43]. 

All gas flow rates must be of sufficient volume to ensure that the sample and its combustion products are passed through the system in a timeframe that allows the analyzer to promptly return to baseline conditions prior to the next injection. Favorable gas flow rates will eliminate or minimize sample valve wetting, ensure sufficient sample combustion, provide sharp Gaussian peak characteristics, and enhance detector response. 

A mercury analyzer based upon complete sample combustion followed by CVAAS has proven to be a relatively simple instrument to operate and maintain. The technique requires practically no sample preparation for a light crude oil therefore loss of analyte or contamination by mercury sources in the laboratory is minimized. By testing a variety of mercury species and sample types, we have demonstrated that instrument response is independent of the form of mercury and the sample matrix. This makes standardization with stable mercury species an easy and reliable procedure. 

It can be seen from our data that, as the content of the halide increases, the temperature and linear burning rate decrease, which is accompanied by a decrease in the acid-alkali balance of the washing water (pH). The maximal yield of titanium nitride is observed at = 1.0-1.2. It should be noted that TiN is also formed at combustion temperatures lower than 900 °C, which can be explained by the increased activity of reagents in the combustion zone. At = 1.5-3.0, the combustion of the system becomes unstable and some samples combust incompletely. The synthesized titanium nitride powder is preferentially black, but there are some gold-yellow particles that are observed in the internal layers of the sample. The color black indicates that the particle size of the titanium nitride is <1 pm, while the gold-yellow hue points to their sintering. The fraction of the latter in the total mass of the titanium nitride powder is no larger than 1%. 

Plasma is separated from cellular contents by immediate centrifugation, and the cellular pellet may be retained for cell content determination. Aliquots of plasma separated by blood centrifugation at the clinieal site are frozen at—70°C and shipped to the analysis laboratory. A 25-pL aliquot of the thawed vortexed plasma is pipetted to a sample combustion vial and reduced to carbon for AMS analysis as above. This provides the total measure of all compounds. 

AUTOMATIC SAMPLE COMBUSTION MEIHODS FOR TEE DETERMINATION OF SOFT BETA-EMITTING ISOTOPES IN DUAL LABELLED ORGANIC COMPOUNDS AND BIOLOGICAL MATERIALS BY LIQUID SCINTILLATION COUNTING... 

A. Sample Combustion System for Carbon-14 and/or Tritium Determination... 

Fig. 13.10 TGandDTG curves of the samples combustion in air flow of grounded rice husks (a) and pyrolysis in nitrogcm flow (b)...

Glucose/Cysteine Systems. The method of sample preparation was adapted from Yeo and Shibamoto 14). L-Cysteine (0.05 mol) and D-glucose (0.05 mol) were dissolved in 30 mL of deionized water, and the pH of each solution was adjusted to 2, 5,7, and 9 with either 6N HCl or 6N NaOH. The solutions were then brought to a final volume of 50 mL with deionized water and covered with Saran Brand plastic wrap. The four solutions were irradiated at the high setting of a 700-W microwave oven for 15 min. At 4-min intervals, the irradiation was interrupted and the samples rotated 90 to ensure uniform irradiation. The irradiation time coincided with the onset of browning, whereas further irradiation led to charring and sample combustion. 

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