Hexane liquid chromatography

The method of detecting dimethylterephthalate (DMTP), dibuthyl-phthalate (DBP) and diocthylphthalate (DOP) in aqueous extract is based on their extraction with an organic solvent (hexane) and subsequent concentration using gas-liquid chromatography and an electron-absorbing detector. The detection limit is 0.05 mg/dirf for DMTP and DBP, and 0,01 mg/dm for DOP. 

One example of normal-phase liquid chromatography coupled to gas chromatography is the determination of alkylated, oxygenated and nitrated polycyclic aromatic compounds (PACs) in urban air particulate extracts (97). Since such extracts are very complex, LC-GC is the best possible separation technique. A quartz microfibre filter retains the particulate material and supercritical fluid extraction (SPE) with CO2 and a toluene modifier extracts the organic components from the dust particles. The final extract is then dissolved in -hexane and analysed by NPLC. The transfer at 100 p.1 min of different fractions to the GC system by an on-column interface enabled many PACs to be detected by an ion-trap detector. A flame ionization detector (PID) and a 350 p.1 loop interface was used to quantify the identified compounds. The experimental conditions employed are shown in Table 13.2. 

Olefins, sultones, alkanes, and alkenesulfonates may be separated by liquid chromatography on silica gel using hexane, trichloromethane-hexane, ethanol-dime thy lcarbonate, and ethanol-ammonium hydroxide as the eluents. Pueschel and Prescher [110] achieved the separation of alkene-1,4-sultone and alkene-1,3-sultone from each other and from other sulfonic acid esters in AOS by thin-layer chromatography on silica gel G with 4 1 diethylcarbonate-ligroine as the... 

Figure 7. Separation of eight biogenic amines using ion pair partition liquid chromatography. Conditions 30 cm column with 4 fim silica stationary phase, 0.1M HClO /0.9M NaClO mobile phase, ethylacetate/tributyl phosphate/hexane (72.5/10/17.5) velocity, 0.8 cm/sec (47).

For the high-performance liquid chromatography (HPLC) determination of napro-anilide and its metabolite, 200 mL of 2% sodium sulfate in 0.1M potassium hydroxide solution are added to the concentrate derived from Section 2.2.2. The solution is shaken twice with 100 mL each of dichloromethane or ethyl acetate-n-hexane (1 1, v/v) for 10 min. The combined organic layer is concentrated. " ... 

Soxhlet extraction followed by liquid chromatography/photodiode-array detection (LC/PAD) is used for the trace determination of propanil and its major metabolite, 3,4-dichloroaniline, in soil. A 10-g soil sample is extracted with methanol in a Soxhlet system for 8 h. After the extracts have been concentrated to dryness, the residue is dissolved in 500 pL of n-hexane. °... 

Distilled water, high-performance liquid chromatography grade Acetone, ethyl acetate, diethyl ether, acetonitrile, n-hexane, benzene, pesticide residue analysis grade... 

This technique is based on the same separation mechanisms as found in liquid chromatography (LC). In LC, the solubility and the functional group interaction of sample, sorbent, and solvent are optimized to effect separation. In SPE, these interactions are optimized to effect retention or elution. Polar stationary phases, such as silica gel, Florisil and alumina, retain compounds with polar functional group (e.g., phenols, humic acids, and amines). A nonpolar organic solvent (e.g. hexane, dichloromethane) is used to remove nonpolar inferences where the target analyte is a polar compound. Conversely, the same nonpolar solvent may be used to elute a nonpolar analyte, leaving polar inferences adsorbed on the column. 

High-performance liquid chromatography (HPLC) with a micellar mobile phase or with a selective pre-column or reaction detection system has also been used to determine alkylenebis(dithiocarbamaes). ° Zineb and mancozeb residues in feed were determined by ion-pair HPLC with ultraviolet (UV) detection at 272 nm. These compounds were converted to water-soluble sodium salts with ethylenediaminetetra-acetic acid (EDTA) and sodium hydroxide. The extracts were ion-pair methylated with tetrabuthylammonium hydrogensulfate (ion-pair reagent) in a chloroform-hexane solvent mixture at pH 6.5-8.S. The use of an electrochemical detector has also been reported. ... 

Plant materials are homogenized with methanol. Hexythiazox residue is extracted with hexane and then transferred to acetonitirile by liquid-liquid partitioning. The acetonitirile is removed by rotary evaporation and the sample is cleaned up using Florisil PR column chromatography. The concentrated eluate is subjected to high-performance liquid chromatography (HPLC) analysis. 

Pyrimidifen is extracted from plant materials with methanol-water (7 3, v/v). The extracts are concentrated and pyrimidifen is partitioned with n-hexane after addition of sodium chloride. The organic phase is collected and concentrated. Pyrimidifen in the organic phase is purified by silica gel column chromatography. Pyrimidifen is dissolved in acetonitrile and injected into a high-performance liquid chromatography... 

Methanol, n-hexane, ethyl acetate, distilled water, sodium chloride, sodium sulfate, reagent grade for residue analysis (Wako Pure Chemical Industries, Ltd, Japan) Acetonitrile, methanol, distilled water, reagent grade for high-performance liquid chromatography... 

Enantiomers of the 8,9-dichloro-2,3,4,4 ,5,6-hexahydro-177-pyrazino[l,2-tf]quinoxalin-5-one (structure 249 Rz = R3 = Cl R1 = R4 = H) could be separated by normal-phase, chiral high-performance liquid chromatography (HPLC) with increased retention and separation factors if ethoxynonafluorobutane was used as solvent, instead of -hexane <2001JCH(918)293>. 

Aboul-Enein and Ali [78] compared the chiral resolution of miconazole and two other azole compounds by high performance liquid chromatography using normal-phase amylose chiral stationary phases. The resolution of the enantiomers of ( )-econazole, ( )-miconazole, and (i)-sulconazole was achieved on different normal-phase chiral amylose columns, Chiralpak AD, AS, and AR. The mobile phase used was hexane-isopropanol-diethylamine (400 99 1). The flow rates of the mobile phase used were 0.50 and 1 mL/min. The separation factor (a) values for the resolved enantiomers of econazole, miconazole, and sulconazole in the chiral phases were in the range 1.63-1.04 the resolution factors Rs values varied from 5.68 to 0.32. 

The procedure provides a sensitive derivative for analysis of Diclofopmethyl and of its hydrolysis product by gas-liquid chromatography. Standards of the derivative, stored in hexane at room temperature, were stable for at least one month. The method is rapid and permits the detection of 0.05mg kg-1 of diclofop in soil with minimum interference from coextractives. The alkylation product also provides a second method for verification of diclofop by gas-liquid chromatography. 

By a method similar to that described in the last section phenylazide in cyclohexene was irradiated with ultraviolet radiation and unreacted cyclohexene was distilled off with evaporation. The residue was extracted with n-hexane. The extract was separated into several products by gas and liquid chromatography. The gas chromatogram and the liquid chromatogram are shown in Figures 7 and 8, which give five peaks from A to E, and four peaks from A to D, respectively in addition to the peak due to the solvent. Peaks A and A were determined to be aniline by their retention times. Peaks B and C are due to 3,3 -bicyclohexenyl. Peaks C and D are those of aziridine[9] and the product which was formed by the insertion of phenylnitrene to C-H bond of cyclohexene. ... 

One column can be used for different types of liquid chromatography by changing the eluent components. As an example, a column packed with octadecyl-bonded silica gel has been used for size-exclusion liquid chromatography with tetrahydrofuran (THF), normal-phase liquid chromatography with n-hexane, and reversed-phase liquid chromatography with aqueous acetonitrile. Examples of the chromatograms are shown in Figure 1.4. 

The elution volumes of polystyrene and benzene in the size-exclusion mode were 0.98 and 1.78 ml, respectively (Figure 1.4A). This means that separations by molecular size can be achieved between 0.98 and 1.78 ml in this system. In the normal phase mode the elution volumes of octylbenzene and benzene were 1.98 and 2.08 ml, respectively, in n-hexane solution (Figure 1.4B). This type of chromatography is called adsorption or non-aqueous reversed-phase liquid chromatography. These are adsorption liquid chromatography and non-aqueous reversed-phase liquid chromatography. The elution order of the alkylbenzenes in the reversed-phase mode using acetonitrile was reversed... 

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