Methanol analytical procedures

METHANOL, Analytical Procedures Methanol, Federal Specification 0-M-232E (July 30, 1968) entitled Methanol (Methyl Alcohol) requirements and tests, supplemented by Amena ment 1 (Sept II, 1970)... 

Analytical Procedures. Standard methods for analysis of food-grade adipic acid are described ia the Food Chemicals Codex (see Refs, ia Table 8). Classical methods are used for assay (titration), trace metals (As, heavy metals as Pb), and total ash. Water is determined by Kad-Fisher titration of a methanol solution of the acid. Determination of color ia methanol solution (APHA, Hazen equivalent, max. 10), as well as iron and other metals, are also described elsewhere (175). Other analyses frequendy are required for resia-grade acid. For example, hydrolyzable nitrogen (NH, amides, nitriles, etc) is determined by distillation of ammonia from an alkaline solution. Reducible nitrogen (nitrates and nitroorganics) may then be determined by adding DeVarda s alloy and continuing the distillation. Hydrocarbon oil contaminants may be determined by ir analysis of halocarbon extracts of alkaline solutions of the acid. 

Silica gel, per se, is not so frequently used in LC as the reversed phases or the bonded phases, because silica separates substances largely by polar interactions with the silanol groups on the silica surface. In contrast, the reversed and bonded phases separate material largely by interactions with the dispersive components of the solute. As the dispersive character of substances, in general, vary more subtly than does their polar character, the reversed and bonded phases are usually preferred. In addition, silica has a significant solubility in many solvents, particularly aqueous solvents and, thus, silica columns can be less stable than those packed with bonded phases. The analytical procedure can be a little more complex and costly with silica gel columns as, in general, a wider variety of more expensive solvents are required. Reversed and bonded phases utilize blended solvents such as hexane/ethanol, methanol/water or acetonitrile/water mixtures as the mobile phase and, consequently, are considerably more economical. Nevertheless, silica gel has certain areas of application for which it is particularly useful and is very effective for separating polarizable substances such as the polynuclear aromatic hydrocarbons and substances... 

The analytical procedure for the alkaline aqueous layer containing n is as follows. After acidifying the solution (about pH 2) with 4 mL of concentrated HCl, extract twice with 100 mL of dichloromethane. Dry the dichloromethane extract with anhydrous sodium sulfate and collect the dried solution in a 300-mL round-bottom flask. Evaporate the solvent under reduced pressure. Dissolve the residue in a mixed solvent consisting of 4mL of ethyl acetate, 0.5 mL of methanol and 30 pL of concentrated HCl. To this mixture, add 7 mL of diazomethane-diethyl ether solution and allow the mixture to stand at room temperature for 1 h. Concentrate the reaction mixture to 0.5 mL under reduced pressure and evaporate the solvent in a gentle stream of nitrogen. Dissolve the residue in a small volume of dichloromethane-n-hexane (1 2, v/v) and transfer the solution to the top of column. Elute with solvent of the same composition, discard 60 mL of the initial eluate and collect 100 mL of the subsequent eluate in a 200-mL round-bottom flask. Concentrate the eluate to 0.5 mL under reduced pressure, evaporate the solvent in a gentle stream of nitrogen and dissolve the residue in an appropriate volume of acetone for analysis. 

In another study, PLE with methanol was compared with Soxhlet with methanol [49], Recoveries and relative standard deviations were comparable for both the methods, confirming that Soxhlet can easily be substituted by PLE in already developed methods, without other substantial changes in the analytical procedure. 

Of the analytical procedures used for the determination of LAS in soils (Table 6.7.1), most methods rely on (Soxhlet) extraction with methanol, followed by clean-up on SPE cartridges (RP-C18 and/or SAX) and final quantitative measurements by HPLC—UV/FL. Applying this protocol, detection limits were achieved ranging between 0.05 and 5 mg kg-1 depending on the matrix, the enrichment factor and the optical detection system employed. 

Analytical Procedures. Incubation mixtures were extracted with diethyl ether except in the case of toxaphene where a mixture of chloroform-methanol (5 1, v/v) was used instead. Ether extracts of DDT, dieldrin, and lindane were dried over anhydrous sodium sulfate, evaporated using a gentle stream of nitrogen, and the residues were redissolved in n-hexane. Aliquots of the hexane solutions were directly injected into a gas liquid chromatograph (GLC, Varian, model 240 ) equipped with an electron capture (EC) detector (Aerograph Sc H detector) and a 1.5% 0V-101 on chrom GHP 100/120, 5 x 1/8" stainless steel column. The detector temperature was 245°C, injection port 235°C, and the oven temperature was 125°C for lindane, 180°C for DDT and 200°C for dieldrin. Carrier gas was nitrogen at the flow rate of 40 ml/min. 

Fiamegos, Y.C. et al.. Analytical procedure for the in-vial derivatization-extraction of phenolic acids and flavonoids in methanolic and aqueous plant extracts followed by gas chromatography with mass-selective detection, J. Chromatogr. A, 1041, 11, 2004. 

Other Analytical Procedures. Thin layer chromatography was carried out with silica gel plates G60 (Merck), using either chloroform-methanol-water (65 5 9) or n-propanol-0.2% CaCl2 in H20 (80 20). The plates were developed with resorcinol spray (15). Sialic acid was determined with thiobarbituric acid after hydrolysis in 0.1 sulfuric acid (16). 

Analytical Procedures. The extracts from exposure pads, hand rinses, and apple leaves were evaporated to dryness in the 40-45°C water bath, and the carbaryl residues were determined by the procedure of Maitlen and McDonough (4). In this procedure, the residues were hydrolyzed with methanolic potassium hydroxide to 1-naphthol which was then converted to the mesylate derivative by reaction with methanesulfonyl chloride. The carbaryl mesylate was quantitated with a Hewlett Packard Model 5840A gas chromatograph (GLC) equipped with a flame photometric detector operated in the sulfur mode. The GLC column was a 122 cm x 4.0 mm I.D. glass column packed with Chromosorb G (HP) coated with 5% OV 101. The column was operated at a temperature of 205°C with a nitrogen flow rate of 60 ml/min. 

Cahill et al. [241] have developed a simple and sensitive analytical procedure for determining the concentration of trifluoroacetic acid in plant, soil, and water samples. The analysis involves extraction of trifluoroacetic acid by sulfuric acid and methanol followed by derivatisation to the methyl ester of trifluoroacetic acid. This is accomplished within a single vial without complex extraction procedures. The highly volatile methyl ester is then analysed using headspace gas chromatography. The spike recovery trials from all media ranged from a low of 86.7% to a high of 121.4%. The relative standard deviations were typically below 10%. The minimum detectable limit for the method was 34 ng/g for dry plant material, 0.20 ng/g for soil and 6.5 ng/1 for water. 

If one wishes to explore further the chemical nature of the phospholipid sample, there are a few relatively simple methods that can be used. Usually the phospholipid is obtained as a viscous material (either colorless or a light tan color) but seldom, if ever, as a friable powder. As a consequence, the most effective way to handle the sample is to dissolve it in a solvent such as chloroform-methanol (2 1, v/v) and make to volume in a glass-stoppered volumetric flask. Then aliquots can be taken for the following simple analytical procedures ... 

The GC/MS procedures for methamphetamine are described in Table 4. The papers published in Japanese - have corresponding reports in English. - - Methamphetamine was detected and determined by mass fragmentography in rat hair after administration of the substance. Nine methods also detected the metabolite amphetamine or amphetamine alone. Suzuki et al. determined methamphetamine also in nail, sweat and saliva. The workup (EX after acid or alkaline hydrolysis) and derivatization technique (methanol-trifluoroacetic acid [TEA]) is rather uniform in most procedures. Nakahara et al. ° used methoxyphenamine excretion into beard hair to discuss several washing procedures. Alkaline or methanolic extraction are used with one exception. Derivatization is mainly made by fluorinated anhydrides. A review ° gives details on analytical procedures, incorporation rates of amphetamines from blood to hair, and relationship between drug history and drug distribution in hair. 

Sterol Analyses. The overall analytical procedure for each 2 cm subcore section Is schematically represented in Figure 3, After homogenization and lyophilization, approximately 1 g of each sediment was mixed with 37.5 ml of chloroform, 75 ml of methanol and 30 ml of a buffered aqueous solution (pH=7). The sediment-solvent slurry was then sonicated for 3-5 minutes and the extract decanted to a separatory funnel. Seventy five ml of water was then added to the funnel, resulting In separate aqueous and organic phases. The chloroform layer was then removed and the aqueous phase washed five times with chloroform. The chloroform fractions were then combined and the volume reduced to 10 ml under nitrogen at 37°C. The entire extraction was repeated until the chloroform phase was visually colorless (6-9 extractions). 

The analytical procedures used for TS and VS determinations are those described in Standard Methods for Examination of Water and Wastewater , 16th Edition, 1985. M.B.A.S. analysis were carried out using the same procedure described for water samples after a previous extraction step with methanol in a Soxhlet. This extraction method was found to be more reproducible than reflux extraction, for the latter did not guarantee a total anionic surfactant recovery. 

Sorv of Hydn enation. Catalytic hydrogenation is used extensively both in the laboratory and in industrial processes. In the laboratory it is used in chemical syntheses, as a basis for many analytical procedures, and as a research tool in the identification and determination of the structure of organic compounds. In industry, large quantities of hydrogen are consumed in the manufacture of ammonia, methanol, liquid fuels, oxygenated... 

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