Acetone sampling

Figure 14. Reflectron-TOF spectra of acetone (T) cluster ions. Am (T)mH+, Bm (T)mCH5, Cm = (T)mC2H30+. (a) 0.4% water in the acetone sample, (T)i C6HnO+ (mass 157) and (T)2-C6HnO+ (mass 215) are seen, whereas ion signal corresponds to (T)3-H30+ (mass 193 is not found), (b) 0.7% water in the acetone sample, all peaks corresponding to masses 157, 215, and 193 are observed, (c) 1.0% water in the acetone sample, ion peaks corresponding to (T)vC6HnO+ (mass 157) and (T)2 C6HnO+ (mass 215) are not seen however, (T)3-H30+ (mass 193) is clearly identified. Neutral clusters are ionized at 355 nm using a pulsed Nd YAG laser. Taken with permission from ref. 2.

Figure 14a shows a portion of the TOF spectrum of the acetone cluster ions in the case where the water content in the acetone sample is 0.4% or less. There are no peaks corresponding to (T)3(H20)+ (mass 192) or (T)3 (H20) H+ (mass 193), and one can readily identify the ion peaks at masses 157 and 215 corresponding to the (T)m 2 C6HII0+ (m > 2) ions as clearly originating from the direct elimination of water molecules from the (T)m H+ via the reaction ... 

Figure 7. Acetone sampling data T = 298 K RH = 90% P = 760 mm Hg concentration = 1100 ppm ( ) front section (O) backup section...

The reaction mixture contained Tris-HQ buffer (pH 7.4), glucose-6-phosphate, NADP, glucose-6-phosphate dehydrogenase, and the microsomes. The mixture was preincubated, and the reaction was started by the addition of BaP dissolved in acetone. The mixture was incubated for 30 minutes at 37°C and terminated by the addition of cold acetone. Samples were diluted and injected for analysis. An example of the assay results is shown in Figure 9.126. The activity was from rat microsomes. 

Consider two moles of pure acetone, and suppose that the Gibbs free energy is Gacet. p is simply G/ =Gacet/2, and the free energy of the acetone sample is 2p. Alternatively, consider a lake as the system, to which the two moles of acetone are added. By how much does the free energy of the system increase Temperature and pressure may be supposed constant, and, for the water molecules at least, their environment is unchanged. Acetone, however, now finds itself in a pure water environment, and //acet will be (Fig. 7.4) ... 

A method was developed [41] for the analysis of natural penicillins after methylation. Previously only paper chromatographic methods for the analysis of penicillins were known [42, 43]. Penicillins were extracted with diethyl ether from aqueous solutions at pH 2 and esterified with a small excess of diazomethane at 0—2°C. The solution of methyl esters was evaporated to dryness and the residue was dissolved in acetone. Samples of 1 —3 fxl were analysed on a glass column (150 cm x 4 mm I.D.) packed with 3% OV-17 on Gas-Chrom Q (100-120 mesh) with a carrier gas (nitrogen) flow-rate of 60ml/min. After lOmin isothermal at 180°C the temperature was increased at 4 C/min for 10 min and then kept constant until the end of the analysis. All of the penicillins analysed under these conditions were separated within 45 min methylpenicillin,... 

Experimental Sensitivity The practical sensitivity [21] is determined as follows. When an acetone sample was introduced at a rate of 2.6 x 10 ° g/s from the permeation tube at 25 °C, measurement of the adduct ion current was 2.9 x 10 ° A (with an ion multiplier gain of 2 x 10 ) hence, the sensitivity was ealeulated as 1.12 A/(g/s). The minimum detectable amount (MDA) can be estimated using the actual noise level of the system as the ultimate limitation on the minimum detectable sample size. A signal-to-noise ratio of 10 is a practical and conservative lower Kmit for quantitative detection in the analog detection mode, the MDA was calculated as 8.93 X 10 g/s (with a signal-to-noise ratio of 3), on the assumption that the detection limit of the ion detection system was around 1 x lo A. 

The chromatogram of an acetone sample obtained under these chromatographic conditions is shown in Fig. 9-79. Even after prechloride concentration is below the detection limit. In comparison. Fig. 9-80 illustrates anion analysis in dimethylformamide, which is significantly more contaminated. In this case, a Metrosep Anion SUPP 1 column was used as a stationary phase, with a sodium carbonate eluant. 

First extraction acetone sample/solvent ratio 1 3 Second extraction methanol sample/solvent ratio 1 3 Dichloromethane/60% methanolnvater... 

A comparison of LC methods for determination of cis-trans isomers of P-carotene was made on Vydac C18 201 TP and calcium hydroxide columns (186). The purity and relative distribution of P-carotene and its isomers in several commercially available products were evaluated by HPLC on several columns using a mobile phase of methanol/water (97 3) (187). Because carotenoids and chlorophylls are very sensitive to the nature of injection solvent, such as acetone, sample-solvent interaction may give rise to distorted and even false peaks (188). Because metal column frits may damage carotenoids. Teflon column frits should be used (189). Also artifacts may be produced on the column by reactions among the carotenoids, injection solvents, and mobile phase. Losses that occur during extraction and saponification can be reduced by use of suitable antioxidants (189). 

Titrations were performed automatically, using either a Precision-Dow or Metrohm instrument and a silver billet combination electrode. Standard silver solutions were made from anhydrous silver perchlorate (G. Frederick Smith Chemical Company) dissolved in the purified acetone. They were approximately 0.1N and were standardized against either standard sodium chloride titrated in aqueous solutions or diphenylguanidine in acetone. Samples of the bases which were titrated were usually 1- to 2-mM quantities dissolved in 100 ml of purified acetone. 

Dynamic headspace using Tenax TA. A sample of 500 g of tomato plus 500 mL of saturated calcium chloride solution and an internal standard (2-octanone) were mixed in a blender. The mixture was placed in a 3-L flask. The flask was purged with purified air while the tomato mixture was stirred with a magnetic stirrer the tomato volatiles in the air stream were passed through a 200-mg Tenax trap. The isolation was carried out for 150 min, then the trap was removed and the volatiles extracted with 3 mL of acetone. Samples were concentrated under nitrogen to a volume of 50 pL. 

Benzyl-C, 2-C, -alkyldimethylam-monium chloride, separation by increasing alkyl chain length demonstration of effect of solvents in buffer and in sample solution CZE Silica, 75 [tm x 37 cm, 15kV,25 C 0.02 M phosphate buffer, pH 5.0, 30% CH3CN or 50% acetone sample solution contains CH3OH Cathodic, UV, 210 nm 20,21... 

Table 6.3. Sample molecules acetone and isobutene described by atom pair (ap) descriptors.

Choice of solvent for recrystallisation. Obtain small samples (about 0 5 g.) of the following compounds from the storeroom (i) salicylic acid, (Li) acetanilide, (iii) m-dinitrobenzene, (iv) naphthalene, and (v) p-toluene-sulphonamide. Use the following solvents distilled water, methylated spirit, rectified spirit, acetone, benzene and glacial acetic acid. 

This somewhat lengthy experiment provides a thorough introduction to the use of GG for the analysis of trace-level environmental pollutants. Sediment samples are extracted by sonicating with 3 X 100-mL portions of 1 1 acetone hexane. The extracts are then filtered and concentrated before bringing to a final volume of 10 mL. Samples are analyzed with a capillary column using a stationary phase of 5% phenylmethyl silicone, a splitless injection, and an EGD detector. 

At 25°C, the Mark-Houwink exponent for poly(methyl methacrylate) has the value 0.69 in acetone and 0.83 in chloroform. Calculate (retaining more significant figures than strictly warranted) the value of that would be obtained for a sample with the following molecular weight distribution if the sample were studied by viscometry in each of these solvents ... 

Bhatnagar and Biswast measured the turbidity at 436 nm of 2l single sample of poly(methyl methacrylate) in several solvents, including acetone and methyl ethyl ketone (MEK) ... 

Specification tests are performed on plant streams once or twice per worker shift, or even more often if necessary, to assure the continuing quahty of the product. The tests are also performed on a sample from an outgoing shipment, and a sample of the shipment is usually retained for checking on possible subsequent contamination. Tests on specialty types of acetone may require sophisticated instmments, eg, mass spectrometry for isotopicaHy labeled acetone. 

For small-scale preparation of samples for scientific studies, the precursor polymer may be dissolved in xylene at 80°C, followed by addition of the cation source. A gelled fluid is normally obtained immediately, and the ionomer is recovered as a powder by chopping the gel in a large excess of acetone using a laboratory blender. 

Film or fibers derived from low molecular weight polymer tend to embrittle on immersion ia acetone those based on higher molecular weight polymer (>0.60 dL/g) become opaque, dilated, and elastomeric. When a dilated sample is stretched and dried, it retains orientation and is crystalline, exhibiting enhanced tensile strength. The tensile heat-distortion temperature of the crystalline film is iacreased by about 20°C, and the gas permeabiUty and resistance to solvent attack is iacreased. 

Welding (qv) of titanium requires a protected atmosphere of iaert gas. Furthermore, parts and filler wire are cleaned with acetone (trichloroethylene is not recommended). The pieces to be welded are clamped, not tacked, unless tacks are shielded with iaert gas. A test sample should be welded. Coated electrodes are excluded and higher purity metal (lower oxygen content) is preferred as filler. Titanium caimot be fusion-welded to other metals because of formation of brittle intermetallic phases ia the weld 2oae. 

There is no specific color or other reaction by which methyl chloride can be detected or identified. QuaUty testing of methyl chloride for appearance, water content, acidity, nonvolatile residue, residual odor, methanol, and acetone is routinely done by production laboratories. Water content is determined with Kad Fischer reagent using the apparatus by Kieselbach (55). Acidity is determined by titration with alcohoHc sodium hydroxide solution. The nonvolatile residue, consisting of oil or waxy material, is determined by evaporating a sample of the methyl chloride at room temperature. The residue is examined after evaporation for the presence of odor. Methanol and acetone content are determined by gas chromatography. 

Content of prime - tertiary peroxide groups was measured by the quantity of products of complete decay, which were measured by chromatography. It is known that the main contents in products of the complete decay of Oct-MA-TBPMM samples are acetone and 2,2-dimethylpropanol, which arise in reactions of chain fragmentation of tert-butylperoxy radical or in reaction of chain transfer of this radical. In this case the sum of acetone and 2,2-dimethylpropanol molecules is equal to the quantity of peroxide groups in polymer. As an internal standard we used chloroform. 

Microwave extraction realized at 120 °C for 30 min with Hexane -Acetone (3 2 V/V) as the extraction solvent was identified as the most effective extraction procedure for isolation of TPH from biotic matrices. The aim of this research is to develop a silica gel and alumina fractionation procedure for plant sample extraction. Column chromatography with two solvents (chloroform and hexane dichloromethane) as a mobile phase were used for clean-up of extract. In this research the efficiency of recovery received from chloroform as a mobile phase. 

Hexadecanoic acid (palmitic acid) [57-10-3] M 256.4, m 62-63°, b 215°/15mm, pK 6.46 (50% aq EtOH), 5.0 (H2O). Purified by slow (overnight) recrystn from hexane. Some samples were also crystd from acetone, EtOH or EtOAc. Crystals were stood in air to lose solvent, or were pumped dry of solvent on a vaeuum line. [Iwahashi et al. J Chem Soc, Faraday Trans 1 81 973 1985, pK White J Am Chem Soc 72 1858 1950]. 

Methyl-l-butanol [137-32-6 RS 34713-94-5 S(-)- 1565-80-6] M 88.2, b 130°(/ S), 128.6°(S), [a]p -5.8° (neat), d 0.809, n 1.4082. Refluxed with CaO, distd, refluxed with magnesium and again fractionally distd. A small sample of highly purified material was obtained by fractional crystn after conversion into a suitable ester such as the trinitrophthalate or the 3-nitrophthalate. The latter was converted to the cinchonine salt in acetone and recrystd from CHCI3 by adding pentane. The salt was saponified, extracted with ether, and fractionally distd. [Terry et al. J Chem Eng Data 5 403 7960.]... 

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