Dichloromethane detecting

Vitamin E (a-tocopherol) was extracted from feed and analyzed at the levels of 8-23 pg/mL on a Cjg column (A = 295 nm, ex 330 nm, em) with a 95/5 methanol/ water mobile phase [334]. Amaud et al. [335], chromatographically studied serum extracts for retinol, a-tocopherol, and ) -carotene on a C g column (A = 450nm, 325 nm or 292 nm) and published the retention times of these compounds in pure methanol and 17 other binaiy and ternary mobile phases including itietha-nol/acetonitrile/hexane, methanol/acetonitrile/cyclohexane, methanol/hexane, and methanol/acetonitrile/dichloromethane. Detection limits of 0.1-1.5 pM... 

Fig. 11A-D. Chromatogram of PMMA 280 kDa injected in eluent the detected by A RI detector, B viscosimeter. Mobile phase MEK/cyclohexane. Column packing Silica gel. From [50] with permission. A chromatogram of polystyrene sample injected in dichloromethane detected by C UV, D ELSD. Mobile phase Dichloromethane/n-hexane. Column packing Silica gel [151]...

The preparations are much simplified if a stoichiometric amount of hydrogen halide is added using an indicator to determine the end point. We have found that 1,9-diphenylnona-1,3,6,8-tetraen-5-one (dicinnamalacetone) is of appropriate basicity to detect excess anhydrous hydrogen halides in organic solvents including chloroform, dichloromethane, benzene, toluene, acetic acid, and acetone (but not in alcohols). The reaction between the... 

Tile chloro derivative 33a (not isolated) interacts with pyridine-2,3-diamine in dichloromethane at room temperature to yield 73 (85%) (93BSB357). A further example deals with the reaction between the salt 39 and benzene-1,2-diamine, which gives an imine 74 (80%) under special experimental conditions (93BSB357). In order for the reaction to work, the salt 39 must be isolated prior to its employment (Section IV,C,8). No traces of the diimines were detected for both cases. However, the experimental conditions were not optimized for this purpose since no more than three equivalents of the diamines were used (Scheme 23). 

Fig. 3-18. Selectivity factors a determined for (3,5-dinitroben-zoyl)leucine diallylamide on CSP 15-24. Conditions analyte (3,5-dinitrobenzoyl)leucine diallylamide column 150 x 4.6 mm i.d. mobile phase 20 % hexane in dichloromethane flowrate 1 mL min f UV detection at 254 nm.

The first application of ionic hquids for salen complexes dealt with the epoxidation of alkenes [14]. Jacobsen s Mn complex was immobilized in [bmimjlPFe] and different alkenes were epoxidized with aqueous NaOCl solution at 0 °C. As the ionic solvent sohdified at this temperature, dichloromethane was used as a cosolvent. The recychng procedure consisted of washing with water, evaporation of dichloromethane, and product extraction with hexane. The results (Table 3) were excellent and only a slow decay in activity and enantioselectivity was detected after several cycles. 

Acetochlor and its metabolites are extracted from plant and animal materials with aqueous acetonitrile. After filtration and evaporation of the solvent, the extracted residue is hydrolyzed with base, and the hydrolysis products, EMA and HEMA (Figure 1), are steam distilled into dilute acid. The distillate is adjusted to a basic pH, and EMA and HEMA are extracted with dichloromethane. EMA and HEMA are partitioned into aqueous-methanolic HCl solution. Following separation from dichloromethane, additional methanol is added, and HEMA is converted to methylated HEMA (MEMA) over 12 h. The pH of the sample solution is adjusted to the range of the HPLC mobile phase, and EMA and MEMA are separated by reversed phase HPLC and quantitated using electrochemical detection. 

Water (1000 mL) is transferred into a 2-L separatory funnel and extracted with two portions of 50 mL of dichloromethane for 30 min with a mechanical shaker, and the extracts are collected in a 200-mL Erlenmeyer flask. The combined extracts are filtered through anhydrous sodium sulfate into a 300-mL round-bottom flask and evaporated to dryness with a rotary evaporator under vacuum. The residue is dissolved in 1 mL of n-hexane and an aliquot is analyzed by GC/NPD or GC/lTD under the conditions described in Section 2.2.3. Recoveries from water samples fortified with 0.0002 and 0.001 mgL of pendimethalin were in the range 94-110% by GC/NPD and 91-111% by GC/lTD. The detection limit was lower than 0.0001 mgL with both methods. 

Heat and reflux a 5-g portion of soil sample with 50 mL of methanol-phosphate buffer (pH 7)-water (15 7 28, v/v/v) solvent mixture in a round-bottom flask for 1 h. After cooling, transfer a 10-mL portion of the supernatant to a test-tube and mix with 11 mL of 0.02M H3PO4 solution. Load this solution on to a silica-based SPE cartridge (Analytichem International Clin-Elut 1020) at a flow rate of 1-2 drops per second. Discard this fraction. Elute the analytes with 30 mL of dichloromethane. Concentrate the eluate to dryness with air in a water-bath at a temperature of 40 °C (do not use vacuum). Dissolve the residues in 5mL of HPLC injection solution [900 mL of water - - 50 mL of phosphate buffer (pH 7) 4-50 mL of ACN 4-4 g of TBABr]. Pinal analysis is performed using liquid chromatography/ultraviolet detection (LC/UV) with a three-column switching system. 

Plant samples are homogenized with sodium hydrogencarbonate aqueous solution to prevent decomposition of the analytes during homogenization. Imibenconazole and its primary metabolite, imibenconazole-debenzyl, are extracted from plan materials and soil with methanol. After evaporation of methanol from the extracts, the residues are extracted with dichloromethane from the residual aqueous solution. The dichloromethane phase is cleaned up on Florisil and Cig columns. Imibenconazole and imibenconazole-debenzyl are determined by gas chromatography/nitrogen-phosphorus detection (GC/NPD). 

Mepanipyrim in crop samples is recovered by acetone solvent extraction. The acetone is evaporated under reduced pressure and the residual aqueous extract is hydrolyzed with enzyme (jS-glucosidases) to release hydroxylated metabolite(s). After enzyme treatment, mepanipyrim and the propanol form metabolite are extracted with dichloromethane, purified by silica gel column chromatography and quantified by gas chromatography/nitrogen-phosphoms detection (GC/NPD). 

Water samples are directly partitioned with dichloromethane (DCM). The DCM exAact is then rotary evaporated and driven to dryness with a sAeam of niAogen. The dry residue is dissolved in acetone and analyzed by gas chromatography/nitrogen-phosphorus detection (GC-NPD). 

Residues are extracted with acetone. The extract is rotary evaporated to remove acetone, the concentrated residue is diluted with 5% aqueous sodium chloride, and residues are partitioned into dichloromethane. The extract is then concentrated and purified on a silica gel column. Residues of pyriproxyfen are quantitated by gas chromatography with nitrogen-phosphorus detection (GC/NPD). For citrus, a hexane-acetonitrile solvent partition step is required for oil removal prior to the dichloromethane partition step. 

Dichloromethane extraction of culture broth, thin layer chromatography of the extract, and visualization with 5% vanillin/sulfuric acid spray is effective for detecting cycloheximide in culture broth. Cycloheximide applied to TLC plates in amounts as low as 1 yg/spot will produce visible color with the vanillin spray. 

Theobromine was determined by GC in various foods (bitter chocolate, milk chocolate, chocolate cake, cocoa powder, chocolate milk), and results are given in graphs and tables.27 Homogenized samples were boiled in alkaline aqueous media, then fat was extracted with n-hexane. The aqueous layer was acidified with diluted HC1 and NaCl was added. Theobromine was extracted from this treated aqueous solution with dichloromethane and the extract was evaporated to dryness. The residue was redissolved in dichloromethane containing an internal standard. GC analysis was performed on a column packed with 1% cyclohexane dimethanol succinate on Gaschrom Q, with FID. Average recoveries were 99 to 101%, coefficient of variation was less than 3% and the limit of detection for theobromine in foods was about 0.005%. 

Electrospray mass spectrometry is a technique that allows pre-existing ions to be transferred from solution to the gas phase with minimal fragmentation, followed by conventional mass analysis. Recently electrospray mass spectra have been studied for a number of cationic phos-phinegold(I) complexes in dichloromethane/methanol solution.2525 For derivatives of the types [Au(PR3)2]+ and [Au(PR3)3]+, the intact cations were observed, but ions of the type [Au(PR3)4]+ where not detected in the gas phase. Even the three-coordinated [Au(PR3)3]+ are relatively unstable in the gas phase, and the ions [Au(PR3)2]+ are readily produced. 

GC of aqueous simulant or water extract of olive oil using cold on-column injector. 1,4 butane diol internal standard Solvent extraction with dichloromethane and concurrent derivatisation with 9-(methylaminomethyl)anthracene. Fluorescent derivatives analysed by HPLC with fluorescence detection... 

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