Benzene test sample

When reduced, the samples were tested for ammonia synthesis under certain conditions which were normally a temperature of 450°, a pressure of 330 atm. and S.V. = 15,000. The tested samples were cooled down in synthesis gas, removed from the converter in an atmosphere of purified nitrogen and, still in nitrogen, transferred into either benzene or pentane. 

Lineshape and resolution tests on other nuclei follow a similar procedure to that above. Not all nuclei available with a given probe need be tested and typically only tests for inner and outer coil observations on multinuclear probes are required. This means the second test will often involve carbon-13 for which two samples are in widespread use the ASTM (American Society for Testing and Materials) test sample (40% p-dioxane in deuterobenzene also used for the sensitivity test) or 80% benzene in deuteroacetone. In either case on-resonance continuous-wave (CW) decoupling of protons should be used as this provides improved results for a single resonance relative to broadband decoupling. Rather long (30-40 s) acquisition times will be required for a well shimmed system. 

A variation on this technique is twin ebulliometers. In this technique, two matched ebulliometers are connected to the same external pressure at the top of the condenser. A standard substance with accurately known vapor pressure is placed in one ebulliometer and the test sample in the other. When steady boiling is attained in both sides, they are at the same pressure. Pressure is not measured directly rather the two boiling temperatures are measured. Pressure is established by converting the boihng point of the standard to pressure using a previously determined relationship. For organic liquids, water, benzene, or decane are often used as standards. 

In non-aqueous SEC, benzene, methanol, and acetone can be used as test samples with tetrahydrofuran or chloroform as the mobile phases and polystyrene gels as the column packing material. In aqueous SEC, ethylene glycol, sodium p-toluenesulfonate, glucose, and phenylalanine are employed, according to the type of column packing materials and the experimental conditions. 

FIGURE 16.8 High efficiency analysis of a test sample using five coupled Acquity 1.7-pm columns at near ambient temperature (40 C). Analysis conditions Total column length, 450 mm flow rate, 0.17 ml/min (system) pressure, 999 bar temperature, 40°C (Polaratherm) detection, 210 nm (20 Hz). Mobile phase 30/70 acetonitrile/water. Peak identification 1 = uracil, 2 = caffeine, 3 — pyridine, 4 — aniline, 5 — phenol, 6 — acetophenone, 7 = benzene. Source Reproduced with permission from 2006 Elsevier B.V. 

Now heat the tube very gently at first and then more strongly. A non-conden-sible product such as hydrogen or methane is best detected by collecting a sample of the gas in a test-tube as shown in Fig. 71(A). A condensible product such as benzene or phenol should be collected by twisting the delivery-tube downwards and collecting the liquid in a few ml. of water in a test-tube as shown In Fig. 71(B). 

Rapid, simple, quaUtative methods suitable for determining the presence of benzene in the workplace or surroundings have been utilized since the 1930s. Many early tests offered methods for detection of aromatics but were not specific for benzene. A straightforward test allowing selective detection of benzene involves nitration of a sample to y -dinitrobenzene and reaction of the resultant ether extract with an ethanoHc solution of sodium hydroxide and methyl ethyl ketone (2-butanone), followed by the addition of acetic acid to eliminate interferences from toluene and xylenes. Benzene imparts a persistent red color to the solution (87). The method is claimed to be sensitive to concentrations as low as 0.27 ppm benzene from 10 mL air samples. 

Charcoal Tubes Reference has been made earlier to adsorption, which is the property of some solid materials, such as activated charcoal, to physically retain solvent vapors on their surfaces. In environmental health testing, the adsorbed vapors are removed, generally with a solvent, in a laboratory. The solvent is then analyzed by physical methods (gas chromatography, etc.) to determine the individual compounds whose vapors, such as benzene, were present in the sampled air. Industrial atmospheric samples can be collected in small glass tubes (4 mm ID) packed with two sections of activated charcoal, separated and retained with fiberglass plugs. To obtain an air sample, the sealed ends of the tube are broken off, and air is drawn through the charcoal at the rate of 1 liter per minute by means... 

The course of the fermentation is tested by removal of samples which are extracted with methyl isobutyl ketone. The extracts are analyzed by thin layer chromatography using a system of benzene/ethyl acetate (4 1). 

Self-Test 6.9A A sample of benzene, C6H6, was heated to 80°C, its normal boiling point. The heating was continued until 15.4 kj had been supplied as a result, 39.1 g of boiling benzene was vaporized. What is the enthalpy of vaporization of benzene at its boiling point ... 

Self-Test 7.9B Calculate the entropy of a sample of a solid in which it is supposed that a substituted benzene molecule, C6H5F, can take any one of six orientations with the same energy. Suppose there is 1.0 mol of molecules in the sample. 

Sf lf-Test 8.15A The osmotic pressure of 3.0 g of polystyrene dissolved in enough benzene to produce 150. mL of solution was 1.21 kPa at 25°C. Calculate the average molar mass of the sample of polystyrene. 

Figure 2, it will be seen that the major maxima coincide at 550 to 560 m/. The nature of this interfering contaminant is not known, but it is readily extractable into aqueous hydrochloric acid (7). To eliminate the tedium of testing and tracing every lot of benzene, 25 ml. of 10% hydrochloric acid solution are routinely added to the sample just prior ta mincing. This procedure has effectively removed such solvent interference from consideration. 

A number of official samples have been analyzed in the insecticide laboratory of the Production and Marketing Administration, which contained among the active ingredients 7-benzene hexachloride, DDT, and sulfur in the proportions of 3, 5, and 57%, respectively. The following detailed procedure was adopted after testing with authentic formulations of this type. 

The sample pretreatment steps for surfactant analysis such as extraction and concentration can be carried out in a variety of ways. Most of the common and well tested procedures have been described by Schmitt [46]. Solid phase extraction (SPE) with C2, Cg or Cis and divinyl benzene resins as well as special phases, e.g. graphitised carbon black (GCB), can be adequate methods, especially for SPE of metabolites from... 

These conclusions were not applicable when sediment was the source of hydrocarbons. McCain et al. (5) studied the bioavailability of petroleum in sediment to English sole (Parophrys vetu-lus). Sediments rich in alkylated and non-alkylated benzenes and naphthalenes, together with fluorene and phenanthrene, were employed. After 11 days of exposure, samples of skin, muscle, and liver were examined. Fluorene and phenanthrene were not accumulated in the test fish however, significant concentrations of 1-methyl naphthalene, 2-methyl naphthalene, 2,6-dimethyl naphthalene and 1,2,3,4-tetramethylbenzene, were found in skin and liver (Table II) 1-methyl naphthalene and 2-methyl naphthalene were the major components of muscle. In each tissue examined, 1-methyl-naphthalene was the major component 1,2,3,4-tetramethylbenzene occurred in relatively low concentrations in skin and muscle in comparison to naphthalenes containing one and two alkyl groups. 

To determine the concentrations of benzene, toluene, ethylbenzene, and xylenes, approved methods (e.g., EPA SW-846 8021B, SW-846 8260) are not only recommended but are insisted upon for regulatory issues. Polynuclear aromatic hydrocarbons (PAHs) may be present in condensate, and evaluation of condensate contamination should include the use of other test methods (EPA SW-846 8270, SW-846 8310) provided that the detection limits are adequate to the task of soil and groundwater protection. Generally, at least one analysis may be required for the most contaminated sample location from each source area. Condensate releases in nonsensitive areas require analysis for naphthalene only. The analysts should ensure that the method has detection limits that are appropriate for risk determinations. 

A number of different testing kits based on immunoassay technology are available for rapid field determination of certain groups of compounds, such as benzene-toluene-ethylbenzene-xylene (EPA 4030) or polynuclear aromatic hydrocarbons (EPA 4035, Polycyclic Aromatic Hydrocarbons by Immunoassay). The immunoassay screening kits are self-contained portable field kits that include components for sample preparation, instrumentation to read assay results, and immunoassay reagents. 

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