Low-temperature asher

LCCC Liquid chromatography under LTA Low-temperature asher... 

Prior to radiochemical analysis the samples were ashed and separated into size fractions by means of procedures described by Nathans et al. The determinations of the fraction weights and of the mean diameters of the particles in the fractions have also been described extensively in the same paper. An aliquot of each size fraction was dissolved and subjected to a separation procedure to isolate Sr, Ru, Sb, Cs, Ce, Pm, U, and Pu fractions. The procedure is sketched in Figure 1. Further decontamination of Ru and Ce was carried out only with the Johnie Boy sample. The Sb and Pu fractions were set aside for later analysis. After complete analysis of the Cs fractions, anomalies were found in the data for the coral samples. These samples had been ashed at about 475°C. Apparently some Cs had volatilized at this temperature. Such a behavior explained the anomalies, and this was confirmed by Heft by more extensive experimentation (4). Thus, Cs data are reported only for the Johnie Boy sample, which was ashed at low temperature in a Tracerlab low temperature asher. 

Ashing. Sections of filter papers containing the samples from Johnie Boy were ashed in a Trapelo low temperature asher to prevent volatilization of some of the fission products of interest for different portions... 

Simultaneously with the efforts to determine the origin of mineral matter in coal, systematic efforts were underway to estimate the quantitative distribution of trace and minor elements in American coals. The early analyses were performed on high-temperature ashes, and as a consequence, the investigators had to be content with determining the nonvolatile metallic oxides. However, with the advent of the low temperature asher and improvisations and advances in wet chemical, radiochemical, and instrumental analytical techniques, we not only can analyze nondecomposed mineral matter but also can study the composition of whole coal. 

Within the past decade the technique of electronic (radiofrequency) low-temperature ashing has been used to investigate mineral matter in coal. In a low-temperature asher, oxygen is passed through a radiofrequency field, and a discharge takes place. Activated oxygen thus formed passes over the coal sample, and the organic matter is oxidized at relatively low temperatures—usually less than 150°C (14). 

The oils were distilled at 1 mm pressure until about one third remained in the pot. The undistilled residue, the solid residue from the reaction (catalyst pellets removed by hand), and the original coal were ashed in an oxygen plasma without external heating, using a low temperature asher from International Plasma Corp. 

Preparation of Chelates The procedure we use is adapted from that used by Hui et al ( ) to measure copper in rat brain Samples of feces approximately 0 25 g were ashed in a low temperature asher dissolved in concentrated HC1 and applied to Bio-Rad AG-1 anion exchange columns [Mention of a trademark or proprietary produce does not constitute a guarantee or warranty of the product by the U S Department of Agriculture and does not imply its approval to the exclusion of other products that may also be suitable ] The various metals were then separated by elution with successively lower concentrations of HCl Recovery of metals from the columns was 97 6+2 7% for Fe, 10(H 2% for Cu, and 93 7+1 8% for Zn Each metal fraction was then refluxed separately with TPP in dimethylformamide to form the metal chelate ( ) ... 

Figure 8.12 Schematic system arrangement. The chamber design consists of a modified low-temperature asher reaction chamber. Adapted from Ref. 7.

Filter Preparation. Currently, for the sake of minimal NASN sample usage, a quarterly composite is constructed from strips from individual filters. A minimum of five samples and not more than seven must be taken per quarter. No two samples shall be taken within the same calendar week. An interval of at least two days must exist between samples. There should be at least one sample and not more than three per month. A composite is oxidized in a low-temperature asher, extracted with mixed (1 3 constant boiling hydrochloric and nitric) acids, the acid extract concentrated and the supernatant taken for analysis. (In some cases... 

The second method of sample preparation used a low-temperature asher (Model LTA 600, Tracerlab). A known weight of the lyophihzed sample was placed in a quartz boat and ashed widi a reduced pressure... 

We used two plasma ashing devices International Plasma Corporation, Model 1003B-248AN and LFE Corporation, Low Temperatures Asher, No. LTA-600.) Since the plasma combustion temperature does not exceed 50°C we avoid the possibility of mineral decomposition (especially of carbonates) encountered during high temperature combustion. 

The dry ashing of these specimens can be carried out either in a muffle furnace or in the low temperature asher (LTA) using an oxygen plasma using the procedure given below ... 

Particulate matter in a measured volume of air can be collected on a cellulose-acetate-membrane filter (e.g., Millipore ). The filter is dry ashed in a low-temperature asher. (This device uses oxygen radicals in a radio-frequency plasma for ashing at below 100°C, thus minimizing losses due to volatility of the test element and retention on crucible walls.) The ash is taken up in dilute HCl and aspirated directly, or the filter can be digested with a mixture of nitric and perchloric acids. For beryllium determination, a nitrous oxide-acetylene flame is used. Results are reported as Mg/m of air. 

Finely ground (usually -300 mesh) coal samples are ashed at 750 C in a muffle furnace to a constant weight. Alternatively, an RF plasma low temperature asher can be used however, the time needed for ashing is of the order of a few days. The coal ash or... 

Hauser et al. (H3) preashed blood samples in the sampling boat in a low temperature asher prior to analysis by the sampling-boat method. 

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