Methanol solvent high performance liquid

Milbemectin consists of two active ingredients, M.A3 and M.A4. Milbemectin is extracted from plant materials and soils with methanol-water (7 3, v/v). After centrifugation, the extracts obtained are diluted to volume with the extraction solvent in a volumetric flask. Aliquots of the extracts are transferred on to a previously conditioned Cl8 solid-phase extraction (SPE) column. Milbemectin is eluted with methanol after washing the column with aqueous methanol. The eluate is evaporated to dryness and the residual milbemectin is converted to fluorescent anhydride derivatives after treatment with trifluoroacetic anhydride in 0.5 M triethylamine in benzene solution. The anhydride derivatives of M.A3 and M.A4 possess fluorescent sensitivity. The derivatized samples are dissolved in methanol and injected into a high-performance liquid chromatography (HPLC) system equipped with a fluorescence detector for quantitative determination. 

The methylene blue reaction can also be used in a fractionation procedure for surfactants. The complexes with methylene blue can be collected in an organic solvent, concentrated, dissolved in methanol, and separated by high-performance liquid chromatography [205]. A variation of this method, permitting the collection of surfactant from large volumes of sample, should be workable in seawater. 

Tsuji and Goetz24 developed a quantitative high performance liquid chromatographic method for separating and measuring erythromycins A, B, and C, their epimers and degradation products. This method uses a /iBondapak Ci 8 reverse column with acetonitrile-methanol-O.2m ammonium acetate-water (45 10 10 25) as solvent. The pH and composition of the mobile phase may be adjusted to optimize resolution and elution volume. The authors utilized the procedure on USP reference standard and report a relative standard deviation of 0.64%. 

Pretreated samples were evaporated to remove nonreacted methanol and extracted by solvents (chloroformin-hexane = 1 2) and centrifuged at low temperature to remove glycerin. One milliliter of supernatant was evaporated under vacuum and diluted with methanol (high-performance liquid chromatography [HPLC] grade) for HPLC analysis. 

The products obtained were analyzed for composition using high-performance liquid chromatography (HPLC) (LC -10AT Shimadzu, Kyoto, Japan), which consisted of a column (STR ODS-II, 25 cm in length x 4.6 mm in id Shinwa Chemical, Osaka, Japan) operated at 40°C at a flow rate of 1.0 mL/min with methanol as a carrier solvent. The column was packed with silica particles (5-pm particle diameter and 12-nm pore diameter). The cloud and pour points of the obtained biodiesel were then determined by a mini-cloud/pour point tester (Model MPC-102 Tanaka Scientific, Tokyo, Japan) based on ASTM D2500 for cloud point and ASTM D6749 for pour point (14). 

Hullett and Eisenreich [11] used high performance liquid chromatography for the determination of free and bound fatty acids in river water samples. The technique involves sequential liquid-liquid extraction of the water sample by 0.1m hydrochloric acid, benzene-methanol (7 3) and hexane-ether (1 1). The resultant extract was concentrated and the fatty acids were separated as a class on Florasil using an ether-methanol 1 1 and 1 3 elution. Final determination of individual fatty acids was accomplished by forming the chromatophoric phenacyl ester and separating by high performance liquid chromatography. Bound fatty acids were released by base saponification or acid hydrolysis of a water sample from which the fatty acids had been removed by solvent extraction. 

Schmid et al. described a rapid and sensitive high-performance liquid chromatographic method for the determination of dipyridamole in human plasma [69], The column used was a 12.5 cm x 4.6 mm filled with Lichrosorb RP 18, 5 pm. The mobile phase consisted of methanol-0.2 M Tris HC1 buffer (80 20), eluted at a flow rate of 1 mL/min. Spectrofluorimetric detection at an emission wavelength of 478 nm (excitation at 415 nm) was used for detection. The results were confirmed by re-chromatographing the eluate from the column on silica gel G thin-layer plates, which were developed using a solvent system composed of toluene-isopropanol-ethanol-ammonia (70 15 15 1) and ra-butanol-methyl ethyl ketone (80 20). The Rf values of dipyridamole for the two solvent systems are 0.60 and 0.80, respectively. The plates were dried in a stream of cold air, and then inspected under ultraviolet light at 254 nm. 

Williams et al. used a high performance liquid chromatographic assay method for dipyridamole monitoring in plasma [71]. The HPLC system uses a Waters model 6000 A solvent delivery pump equipped with a U6K injector, a pBondapak C 9 column (30 cm x 39 mm 10 pm), and a Model 440 absorbance detector. The signal from the detector was quantified using a Shimadzu data processor and an Omni-Scribe recorder. A mobile phase flow rate of 1.5 mL/min was produced by a pressure of approximately 102 atm (1500 p.s.i.). The mobile phase was 50 50 mixture of acetonitrile and 0.01 M sodium phosphate in water (adjusted to pH 7). The absorbance reading of dipyridamole in methanol was made at 280 nm. 

Supercritical fluid chromatography (SFC) is very similar in principle to, and is as convenient as, high-performance liquid chromatography, but it uses as the high-pressure eluant fluid CO2 (or other fluid) above its critical point (for CO2 Tc = 31.3°C, Pq = 7.38 MPa, pc = 0.448 g cm-3). SPC can separate relatively small and/or thermally labile molecules. The analyte is introduced as a solution in methanol. Small amounts of organic solvents can be added as "modifiers." Any C02 brought out with the analyte to ambient atmosphere will evaporate harmlessly. 

Reversed-phase high-performance liquid chromatography (RP-HPLC) is the usual method of choice for the separation of anthocyanins combined with an ultraviolet-visible (UV-Vis) or diode-array detector (DAD)(Hebrero et al., 1988 Hong et ah, 1990). With reversed-phase columns the elution pattern of anthocyanins is mainly dependent on the partition coefficients between the mobile phase and the Cjg stationary phase, and on the polarity of the analytes. The mobile phase consists normally of an aqueous solvent (water/carboxylic acid) and an organic solvent (methanol or acetonitrile/carboxylic acid). Typically the amount of carboxylic acid has been up to 10%, but with the addition of a mass spectrometer as a detector, the amount of acid has been decreased to as low as 1 % with a shift from trifluoroacetic acid to formic acid to prevent quenching of the ionization process that may occur with trifluoroacetic acid. The acidic media allows for the complete displacement of the equilibrium to the fiavylium cation, resulting in better resolution and a characteristic absorbance between 515 and 540 nm. HPLC separation methods, combined with electrochemical or DAD, are effective tools for anthocyanin analysis. The weakness of these detection methods is a lack of structural information and some nonspecificity leading to misattribution of peaks, particularly with electrochemical... 

The cosolvent or solvating agent should ideally be UV and VIS radiation transparent and photochemically inert. A common driving force for the choice of a cosolvent is the solvent used for the analytical methods (to help assure photostability of the drug during analytical workup). Thus, acetonitrile and methanol (the most frequently used reversed phase high performance liquid chromatography solvents) are frequently... 

The mobile phase used in the lipophilicity measurements by RP-TLC is usually a binary mixture between an organic solvent and water. The organic solvent can be methanol, acetonitrile, or acetone. The first two can also be used in reversed-phase high-performance liquid chromatography (RP-HPLC) measurements, but... 

Fig. 2 High-performance liquid chromatographic profile of a standard solution at 280, 320, and 350 nm. Separation was achieved with an analytical HPLC unit (Gilson), using a reversed-phase Shepherisorb ODS2 (25.0 x 0.46 cm 5 pm particle size) column. The solvent system used was a gradient of water/formic acid (19 1) (A) and methanol (B). The gradient was as follows 0 min, 30% B 15 min, 30% B 20 min, 40% B 30 min, 45% B 50 min, 60% B 53 min, 100% B and 55 min, 100% B. Detection was accomplished with a DAD. 1—Gallic acid (hydroxybenzoic acid) 2—caffeic acid (hydroxycinnamic acid) 3—mangiferin (xanthone) 4—ferulic acid (hydroxycinnamic acid) 5—eriodictiol (flavanone) 6—hemiarin (coumarine) and 7—quercetin (flavonol).

High performance liquid chromatography may be used to evaluate samples for specific solvents such as methanol. This method for determination is typically lengthy and requires frequent calibration runs. 

The analysis of CAD and alkamides has been completed using a variety of analytical techniques that include high-performance liquid chromatography (HPLC), capillary electrophoresis, gas chromatography (GC), GC-mass spectrometry (GC-MS), liquid chromatography-mass spectrometry (LC-MS), and nuclear magnetic resonance (NMR). Sample preparation methodologies utilize hexane, methanol and ethanol as the primary extraction solvents. 

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