Oils, sample preparation

Name Mineral Oil Sample preparation Capillary film, sodium chloride cell... 

Utilization of a processing plant, it would be necessary to be able to process multiple varieties such as cherry, plum, peach, apple, etc. It is essential that the cost of by-product remain reasonable once a successful recovery operation has been established. Most of the data reported here are for oil samples prepared under laboratory conditions. The extracting solvent used for the oil recovery was usually n-hexane, which is acceptable for edible purposes. Chlorinated solvents are unacceptable for the recovery of edible oils because they may contain chlorinated components such as tetrachloroethane which is not removable by heat treatment and which if present would make the oil too toxic to be consumed. Often oils that are recovered from by-products have properties that make them desirable in cosmetics and in medical preparations. Such specialized application may command a premium price. 

Sample preparation for the modified Fischer assay technique, a standard method to determine the Hquid yields from pyrolysis of oil shale, is necessary to achieve reproducible results. A 100-g sample of >230 fim (65 mesh) of oil shale is heated in a Fischer assay retort through a prescribed temperature range, eg, ca 25.5—500°C, for 50 min and then soaked for 20 min. The organic Hquid which is collected is the Fischer assay yield (7). The Fischer assay is not an absolute method, but a quaHtative assessment of the oil that may be produced from a given sample of oil shale (8). Retorting yields of greater than 100% of Fischer assay are possible. 

Of added interest in this study was the finding that the enantiomeric ratios of a-terpineol also differ widely among populations. In southern populations and the population from the northwestern tip of the island, the amount of (+)-a-terpineol was shown to range from 92.3 to 97.0%, while this enantiomer made up 85.6% in the upper-middle population, but only 66.0% in the population from the southeastern tip of the island. It would be of interest to see if the enzymes responsible for the biosynthesis of a-terpineol have different stereochemical requirements in these populations, or whether some isomerization has occurred in the formation, preparation, or analyses of these oil samples. 

Major emphasis in studies of N-nitroso compounds in foods has been placed upon volatile nitrosamines, in part because these compounds are relatively easy to isolate from complex matrices by virtue of their volatility. Procedures utilizing atmospheric pressure or vacuum distillation have been used by most investigators, with variations of the method of Fine e al. (2) being among the most popular. This procedure employs vacuum distillation of a mineral oil suspension of the sample with optional addition of water to improve nitrosamine recovery from low moisture content samples (6) The usual approach to prevention of nitrosamine formation during analysis involves adding sulfamic acid or ascorbate to destroy residual nitrite at an early stage of sample preparation. 

Some Palmer amaranth samples prepared at SRRC were first extracted with hexane (HX), rather than PE. The organic solvent extracts were supplied for bioassay in the form of oils or solids remaining after solvent removal in vacuo. After each extraction step aliquots of the crude extracts from the roots, stems, or leaves (and thyrses) were evaluated for seed germination regulatory activity. 

SEC in combination with multidimensional liquid chromatography (LC-LC) may be used to carry out polymer/additive analysis. In this approach, the sample is dissolved before injection into the SEC system for prefractionation of the polymer fractions. High-MW components are separated from the additives. The additive fraction is collected, concentrated by evaporation, and injected to a multidimensional RPLC system consisting of two columns of different selectivity. The first column is used for sample prefractionation and cleanup, after which the additive fraction is transferred to the analytical column for the final separation. The total method (SEC, LC-LC) has been used for the analysis of the main phenolic compounds in complex pyrolysis oils with minimal sample preparation [974]. The identification is reliable because three analytical steps (SEC, RPLC and RPLC) with different selectivities are employed. The complexity of pyrolysis oils makes their analysis a demanding task, and careful sample preparation is typically required. 

The goal of our investigations was to characterise the morphology of the sample, and to determine the size and location of the PTFE and silicone oil phases by different methods [46,47], For phase characterization using Raman microscopy, no special sample preparation was necessary. For FTIR imaging, microtomed sections (5 pm in thickness) had to be prepared by cutting the sample with a diamond knife at — 80°C ("cryo-microtomy") to prevent smearing and to obtain flat surfaces. 

Boylan and Tripp [76] determined hydrocarbons in seawater extracts of crude oil and crude oil fractions. Samples of polluted seawater and the aqueous phases of simulated samples (prepared by agitation of oil-kerosene mixtures and unpolluted seawater to various degrees) were extracted with pentane. Each extract was subjected to gas chromatography on a column (8 ft x 0.06 in) packed with 0.2% of Apiezon L on glass beads (80-100 mesh) and temperatures programmed from 60 °C to 220 °C at 4°C per minute. The components were identified by means of ultraviolet and mass spectra. Polar aromatic compounds in the samples were extracted with methanol-dichlorome-thane (1 3). 

MALDI, which is LDI utilizing a particular sample preparation). Although the performance of MALDI is superior to LDI in the analysis of many groups of compounds, LDI is still the perferred choice in some important applications, including cmde oil analysis [155], fullerene detection in rocks [156], atmospheric aerosol analysis [157], semiconductors, and surface analysis [158]. Reference 21 is a comprehensive review of the use of LDI (and several other ion sources) in analysis of inorganics. 

Water may be found in the crude either in an emulsified form or in large droplets. The quantity is generally limited by pipeline companies and by refiners, and steps are normally taken at the wellhead to reduce the water content as low as possible. However, after a spill, water can be introduced by climatic conditions, and the relevant tests (ASTM D96, D954, D1796 IP, 2004) are regarded as important in crude oil analyses. Prior to analyses, it is often necessary to separate the water from a crude oil sample, and this is usually carried out by one of the procedures described in the preliminary distillation of crude petroleum (IP 24). Overall, there are several methods that can be employed for organic semivolatile sample preparation and cleanup procedures (Table 6.4). 

A qualitative method for determining diesel oil in water has been proposed that is based on changes in the internal reflection of an optical fiber coated with an organophilic compound caused by the presence of hydrocarbons. The method does not require any sample preparation but is limited to relatively high... 

High-performance liquid chromatography (HPLC), followed by GC/MS, has been used to fractionate and then quantitate the aliphatic and aromatic hydrocarbons present in liquid fuel precursors in order to determine the fuel potential of the compounds. Kerosene had the advantage of not requiring any sample preparation. Other light fuel oils may require the use of methylene chloride as a solvent prior to HPLC analysis (Lamey et al. 1991). The sensitivity, precision, and recovery of this method were not reported. 

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