Methanol for HPLC

Differences between acetonitrile and methanol are in price, transparency, toxicity, and viscosity methanol for HPLC is approximately by a factor of 3 cheaper than acetonitrile of identical purity ... 

This is achieved by adding 0.5 mg of flavonoid to 3 mg of 3-D-glucosidase in 0.5 mL of 0.1 M citrate-phosphate buffer, pH 5 (37 °C, 24 h). The hydrolysis products are then extracted with ethyl acetate, taken to dryness under reduced pressure (40 °C), and redissolved in methanol for HPLC analysis (Gil et ah, 1998). 

In this experiment, alkaloids were also extracted from the culture medium as follows. Fifty ml of acetic acid was added to 1 litre of culture medium (pH 2-3) and then the aqueous solution was washed with 100 ml of chloroform twice. The aqueous solution made alkaline with 28% ammonium hydroxide (pH 8-9) was then extracted with 100 ml of a mixture of chloroform and isopropanol (3 1) thrice. The combined organic extract was evaporated in vacuo and dissolved in an appropriate volume of methanol for HPLC analysis. 

To separate free sterols and other non polar soluble component of the plant biomass from sapogenin steroid extraction was done in the following method. 1 gram (accurately weight) of dry biomass was extracted 3 times using a vortex-mixer with 5 ml CHCh for each. The residue was hydrolyzed with 2 N HC1 (100°C, 2 hours), cooled, neutralized with 10N NaOH, extracted 3 times with 5 mi CHCh- The chloroform phase was collected and evaporated in N2 to dryness. The hydrolysate extract was dissolved in 1 ml CHCL3 (accurately) before analysis (for TLC) or in methanol (for HPLC). 

A The extraction of additive concentrates. These are mixed additive packages (which may also contain polypropylene) containing up to six additives at individual levels of typically 2-20%. They do not need an exhaustive extraction procedure but do require a sampling technique that ensures a representative sample, and in some cases a dilution step will be necessary. The extraction procedure generally used is a direct extraction with a fixed volume of solvent at ambient temperature using an ultrasonic bath. Extraction periods of up to 30 min are used. The solvents generally used are carbon tetrachloride for IR measurements, 1,2-dichloroethane for non-aqueous potentiometric measurements, and chloroform with subsequent dilution with excess methanol for HPLC measurements [16]. 

MacMillan and Wright [133] identified and measured saturated and unsaturated 1,3- and saturated 1,4-sultones in anionic surfactants by a series of separation maneuvers. Ion exchange treatment separates sultones from the bulk of the ionic surfactant. TLC concentrates the sultones systems for HPLC analysis. They found that pentane-ether is preferable to the usual hexane-ether system and that the addition of a little methanol sharpens the separations. Finally, HPLC using a micro-Porasil column with 90 1 isooctane/ethanol provides quali-... 

For APCI (if matrix effects become a problem in ESI), the mobile phase consisted of (A) 9 1 methanol-water containing 50 mM ammonium acetate and (B) water containing 50 mM ammonium acetate-methanol (9 1). The gradient was held at 50% A-50% B for 10 min and was then changed to 90% A-10% B in 22 min (held for 3 min). The HPLC column was a Zorbax RX-C8, 4.6-mm i.d. x 250 mm, 5 pm particle size, with a flow rate of l.OmLmin and a 50-pL injection. Table 8 shows the ion transitions (parent to product ions) that were monitored for HPLC/ESI-MS/MS. For single-stage HPLC/ESI-MS, Table 9 shows the ions that were monitored. 

Methanol, ethanol, acetonitrile, benzene, trifluoroacetic anhydride, triethylamine, distilled water reagent grade (Wako Pure Chemical Industries, Ltd, Japan) Methanol, distilled water specially prepared reagent for HPLC (Wako Pure Chemical Industries, Ltd, Japan)... 

Quantitation is performed by the calibration technique. A standard solution containing 0.1 mgkg of both M.A3 and M.A4 is prepared and 1, 2.5, 5 and 7.5mL of this solution are pipetted into around-bottom flask separately and evaporated. Each sample is converted into the fluorescent anhydride derivative according to the procedures described above. Each sample is dissolved in lOmL of methanol for injection into the HPLC system. The calibration curves are obtained by plotting the peak heights against the amounts of M.A3 and M.A4. The derivatives for preparing the calibration curve should be freshly prepared on a daily basis prior to quantitation. 

High Performance Liquid Chromatographic (HPLC) Analysis. A Waters HPLC system (two Waters 501 pumps, automated gradient controller, 712 WISP, and 745 Data module) with a Shimadzu RF-535 fluorescence detector or a Waters 484 UV detector, and a 0.5 pm filter and a Rainin 30 x 4.6 mm Spheri-5 RP-18 guard column followed by a Waters 30 x 3.9 cm (10 pm particle size) p-Bondapak C18 column was used. The mobile phase consisted of a 45% aqueous solution (composed of 0.25% triethylamine, 0.9% phosphoric acid, and 0.01% sodium octyl sulfate) and 55% methanol for prazosin analysis or 40% aqueous solution and 60% methanol for naltrexone. The flow rate was 1.0 mL/min. Prazosin was measured by a fluorescence detector at 384 nm after excitation at 340 nm (8) and in vitro release samples of naltrexone were analyzed by UV detection at 254 nm. 

The active components of the herbaceaous perennial plant Hypericum perforatum are antiinflammatory, antidepressive and healing agents, therefore, their analysis is of considerable importance for health care. Samples were prepared by extracting the dried flowering tops by hot methanol. RP-HPLC separations were performed in an ODS column (250 X 4.6 mm i.d. particle size 5 pm) thermostated at 30°C. The steps of gradient elution are listed in Table 2.49. 

Negative atmospheric pressure chemical ionization (APC) low-energy collision activation mss spectrometry has also been employed for the characterization of flavonoids in extracts of fresh herbs. Besides the separation, quantitative determination and identification of flavonoids, the objective of the study was the comparison of the efficacy of the various detection systems in the analysis of flavonoids in herb extracts. Freeze-dried herbs (0.5g of chives, cress, dill, lovage, mint, oregano, parsley, rosemary, tarragon and thyme) were ground and extracted with 20 ml of 62.5 per cent aqueous methanol. After sedimentation the suspension was filtered and used for HPLC analyses. Separations were carried out in an... 

RP-HPLC has also been used for the analysis of flavan-3-ols and theaflavins during the study of the oxidation of flavan-3-ols in an immobilized enzyme system. Powdered tea leaves (20Qmg) were extracted with 3 X 5 ml of 70 per cent aqueous methanol at 70°C for lQmin. The combined supernatants were filtered and used for HPLC analysis. Flavan-3-ols were separated in a phenyl hexyl column (250 X 4.6 mm i.d. particle size 5 /im) at 30°C. Solvents A and B were 2 per cent acetic acid in ACN and 2 per cent acetic acid in water, respectively. Gradient elution was 0-lQmin, 95 per cent B 10-4Qmin, to 82 per cent B to 40-5Qmin 82 per cent B. The flow rate was 1 ml/min. Theaflavins were determined in an ODS column (100 X 4.6 mm i.d. particle size 3pm) at 30°C. The flow rate was 1.8 ml/min and solvent B was the isocratic mobile phase. The data demonstrated that flavan-3-ols disappear during the oxidation process while the amount of theaflavins with different chemical structures increases [177],... 

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