Oils, HPLC analysis

Under a nitrogen atmosphere, a hexane solution of butyllithium (650 pL, 1.00 nunol) was added to bromobenzene (157 mg, 1.00 mmol) in Et20 (0.5 itiL) at 0 X. The mixture was stirred at room temperature for 1 h and then cooled to -78 °C. Trimethoxyborane (104 mg, 1.00 mmol) was added to the reaction mixture. The mixture was stirred at -78 C for 30 min and then at room temperature for 1 h. To the mixture were added H2O (18 mg, 1.00 mmol), isopropyl tra s-2-hexenoate (262) (62 mg, 0.40 mmol), and a solution of Rh(acacXC2H4)2 (3.1 mg, 12 pmol) and (S)-BINAP (9.0 mg, 14 pmol) in dioxane (2.0 mL). The whole mixture was heated at 100 C for 3 h. Addition of saturated aqueous sodium bicarbonate followed by ethyl acetate extraction and chromatography on silica gel (hexane ethyl acetate = 10 1) gave 90 mg (96% yield) of isopropyl 3-phenylhexanoate 264 as a colorless oil. HPLC analysis was performed on a Shimadzu LC-9A (Shimadzu Corp. Nakagyo-ku, Kyoto, Japan) and a JASCO PU- 980, with a JASCO UV-970 UV detector (Jasco Inc., Easton, MD, U.S.A), liquid chromatographic system with chiral stationary phase columns Chiralcel OD-H, OJ and OG, (95% ee). ... 

Gel permeation ehromatography (GPC)/normal-phase HPLC was used by Brown-Thomas et al. (35) to determine fat-soluble vitamins in standard referenee material (SRM) samples of a fortified eoeonut oil (SRM 1563) and a eod liver oil (SRM 1588). The on-line GPC/normal-phase proeedure eliminated the long and laborious extraetion proeedure of isolating vitamins from the oil matrix. In faet, the GPC step permits the elimination of the lipid materials prior to the HPLC analysis. The HPLC eolumns used for the vitamin determinations were a 10 p.m polystyrene/divinylbenzene gel eolumn and a semipreparative aminoeyano eolumn, with hexane, methylene ehloride and methyl tert-butyl ether being employed as solvent. 

C and the residual solid was dried in vacuo over P205 overnight and then heated in toluene (20 mL) under reflux until TLC showed that the reaction was complete (15 min). The sodium p-toluenesulfinate produced was filtered off and the filtrate was washed with H20 (2 x 50 mL), dried and evaporated to leave the product yield 0.40 g (78%) oil bp 80 C/10 Torr. HPLC analysis (silica column at 0 T7) showed that the tautomers 7a and 8a were present in the ratio 5.9 1. 

You have the task of purchasing some n-hexane for use in three different applications (i) pesticide analysis by gas chromatography, (ii) as a solvent to extract some non-polar high-boiling (200-300°C) oils from a soil sample, and (iii) as a mobile phase for HPLC analysis with UV detection. List and contrast the performance characteristics you need to take into account for purchasing the appropriate grade of hexane in each case. n-Hexane boils at about 70°C. Will any of your choices of hexane be suitable for use for HPLC analysis with fluorescence detection Explain your decision. 

Fig. 2.13. HPLC analysis of the extract in supercritical C02 at 66°C and 450 bar with vegetable oil as co-solvent. Reprinted with permission from G. Vasopollo et al. [37].

Nitrobenzene oxidation was carried out by adding 50 mg of dry soda lignin into a mixture of 7 mL of 2 M NaOH and 4 ttiL of nitrobenzene in a 15 ttiL steel autoclave. Then, the antoclave was heated to 165°C for 3 hours in a preheated thermostat oil bath. After the autoclave was cooled to room temperature, the mixture was then transferred to a liqnid-hquid extractor for continuous extraction with chloroform (5 x 20 mL) in order to remove any nitrobenzene reduction product and excess nitrobenzene. The oxidation mixtnre was then acidified by concentrated HCl to pH 3 and further extracted with chloroform (5x15 mL). The solvent from the second chloroform solution was then removed using a rotary evaporator at 40°C under reduced pressure in order to obtain the nitrobenzene oxidation mixture. The mixture was then dissolved into dicloromethane and made up to 10 luL. This mixture was then used as a stock solution for high performance liquid chromatography (HPLC) analysis [6]. 

High-performance liquid chromatography (HPLC), followed by GC/MS, has been used to fractionate and then quantitate the aliphatic and aromatic hydrocarbons present in liquid fuel precursors in order to determine the fuel potential of the compounds. Kerosene had the advantage of not requiring any sample preparation. Other light fuel oils may require the use of methylene chloride as a solvent prior to HPLC analysis (Lamey et al. 1991). The sensitivity, precision, and recovery of this method were not reported. 

HPLC analysis of TAGs was applied to olive oils and a limit for LLL was established at 0.5% of the total TAGs and enclosed in the European Commission (EC) Regulation on olive oils, as well as in the related international norms (International Olive Oil Trade Norm [2], Codex Alimentarius Standard [3]). The method performed the separation by RP-HPLC on a C18 Lichrosorb or Lichrosphere column, 25x0.46 cm, 5 J,m of particle size, isocratic elution with acetone/acetonitrile (50/50 v/v) and RI detection. Eigure 19.1 reproduced the HPLC traces annexed to the official method [4] chromatogram A refers to 100% soybean oil, B to a mixture 50/50 soybean and olive, C 100% olive oil. 

The development of HPLC techniqne led to an increase in the number of scientific papers dealing with phenolic evalnation in foods and, in the meantime, it also improved the nnmber and type of foods in which phenolic snbstances were evalnated. Despite the high number of scientific papers, HPLC analysis of phenolic snbstances, except for wine and tocopherols in fats and oils, has never became an official method of analysis, so the nnmber of scientific papers has ever more increased. 

The mixture was extracted with ethyl acetate (twice) and the combined organic layers were washed with brine and dried over sodium sulfate. Evaporation of solvent gave a crude mixture of epoxides. After purification by silica gel flash column chromatography (hexane/ethyl acetate 100/1-50/1), the corresponding a, S-epoxy ester 3a was obtained (212.7mg, 1.11 mmol, 89%) as a colourless oil. The enantiomeric excess of 3a was determined by chiral stationary-phase HPLC analysis Daicel Chiralpak AD-H, /-PrOH/ hexane 2/98, flow rate 0.4mL min-1, r 31.5 min [(25,5/ )-isomer] and 38.0 min [(2/ ,35)-isomer], detection at 254 nm. [oc]r> —158.8° [c= 1.06, CHCI3 (99% ee)]. 

Compared to refined vegetable oils, the compositions of crude vegetable oils and oil and fat products are more complicated. These samples contain proteins, carbohydrates, and minerals that interfere with HPLC separation and reduce the lifetime of the HPLC column. These compounds need to be largely eliminated from the extract before HPLC analysis. Saponification and heating are used to weaken sample matrices to allow the solvent to fully access all tocopherols and tocotrienols of the sample. Liquid/liquid extraction is used to remove these polar compounds from the organic solvent layer that contains tocopherols and tocotrienols. The normal-phase HPLC method is usually used for crude vegetable oils and vegetable oil products reversed-phase HPLC can be used for animal fat products. 

Thirty minutes is sufficient for sample preparation beginning with refined vegetable oils. However, the other sample preparations take up to 120 min because of the incubation, re-extraction, and evaporation steps. Usually, a batch of samples is prepared at the same time to reduce the preparation time per sample. The running time for HPLC analysis is approximately 18 min for normal phase or 14 min for reversed phase in order to quantify all tocols. The running time for normal phase could be cut to 12 min for samples without 5-tocopherol and tocotrienol. 

Because the PL concentration in the total lipid extract is generally rather low, a preconcentration step is generally required prior to HPLC analysis crude vegetable oils e.g., contain only 0.5-2.0% of phospholipids. 

TL Mounts, AM Nash. HPLC analysis of phospholipids in crude oil for evaluation of soybean deterioration. J Am Oil Chem Soc 67 757-760, 1990. 

TL Mounts, SL Abidi, KA Rennick. HPLC analysis of phospholipids by evaporative laser light scattering detection. J Am Oil Chem Soc 69 438-442, 1992. 

NK Andrikopoulos, H Brueschweiler, H Felber, C Taeschler. HPLC analysis of phenolic antioxidants, tocopherols and triglycerides. J Am Oil Chem Soc 68 359-364, 1991. 

For coumarins in orange fruits (115), the HPLC used a Zorbax Rx C8 (250-mm X 4.6-mm ID, 5 fim) column maintained at 25°C, and analysis was performed by binary-gradient elution using 0.1% HOAc in acetonitrile (eluent A) and 0.1% HOAc in HzO (eluent B). In the author s lab, standard coumarins could be separated by isocratic elution on Zorbax Rx C8 column with acetonitrile-0.1% HOAc in water (35 65) at 1.0 ml/min, as presented in previous work (1). The eluate from the column was passed to a UV detector (UV 330 nm) and then into a fluorescence detector (excitation at 340 nm, emission at 425 nm). As for the specificity, some of the coumarins do not have native fluorescence. Nine coumarins are separated under UV 330 nm, and three coumarins could not be detected with fluorescence detection. Detailed conditions for coumarin analysis in foods and absorption spectra of coumarins obtained by online diode array detector with HPLC were presented by Lee and Widmer (1). Since coumarins exhibit strong absorption in the ultraviolet region, absorption at approximately 313 nm has been used to estimate the dilution of cold-pressed lemon oil with distilled oil (12). Analysis of umbelliferone (7-hydroxy-coumarin) and scopoletin (6-methoxy-7-hydroxycoumarin) in citrus fruits was performed using... 

Using similar reaction conditions with rapeseed oil, fatty acids were treated with various supercritical alcohols. From the HPLC analysis, it was shown that selective reactions could be obtained. Figure 5 presents the yields of alkyl esters of five fatty acids treated in various supercritical alcohols at 300°C. In the case of methanol, the reaction time for the complete conversion... 

Cartoni, G.P. Coeeioli, F. Jasionawska, R. Ramirez, D. 2000. HPLC analysis of the benzoie and einnamie aeids in edible vegetable oils. Ital. J. Food Sci. 12 163-173. 

Lietz, G. Henry, C.J.K. 1997. A modified method to minimise losses of carotenoids and tocopherols during HPLC analysis of red palm oil. Food Chem. 60 109-117. 

Also important is the use of the modem chromatographic methods to separate and identify individual components in commercial cmde shale oil. The use of efficient gas chromatographic columns coupled with ancillary techniques such as mass spectrometry and vapor-phase IR spectroscopy allows the identification of individual shale oil components. A principal part of this study is the comparison of diflFerent types of open tubular columns for the separation of the alkane-alkene fraction of shale oil WCOT, SCOT, and PLOT columns are examined. Gas chromatographic separation of shale oil acids and bases also is performed allowing the identification of these components. The potential utility of subtractive pre-columns in HPLC analysis is illustrated also. 

Antioxidants are used widely in fats and oils products to delay oxidative processes. Synthetic antioxidants, namely, butylated hydroxyanisole (BHA), butylated hydro-xytoluene (BHT), tert-butyUiydroquinone (TBHQ), and propyl gallate (PG), are permitted antioxidants that are frequently used in products. Their presence and concentration may be determined with HPLC and GC methods. Meanwhile, metal chelators such as citric acid may be determined by HPLC analysis. 

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