Analysis of tocopherols in vegetable oils by high-performance liquid chromatography: Comparison of fluorescence and evaporative light-scattering detection

A comparison of the responses of an evaporative light-scattering detector (ELSD) and a fluorescence detector for tocopherols in vegetable oils by high-performance liquid chromatography is presented. The tocopherols were separated from acylglycerols by gel-permeation chromatography (GPC). The tocopherol fraction was collected off a set of four GPC columns with a mobile phase of methylene chloride before separation on a normal-phase silica column with a mobile phase of hexane/isopropanol, 99.7∶0.3 (vol/vol). An internal standard of 5,7 dimethyltocol, which was detected by both the ELSD and fluorescence detector, was used to obtain quantitative data. The fluorescence detector was ten times more sensitive than the ELSD. γ-Tocopherol was the major tocopherol detected in the vegetable oils studied and ranged from 24.1–93.3 mg/100 g. The amounts of tocopherols found in the vegetable oils agreed favorably with the literature values.     

Determination of sucrose polyesters by high performance gel permeation chromatography

Sucrose polyester (SPE) in feces and diets is determined by freeze-drying the samples, extracting with ethyl ether, and subjecting the extracts to high performance gel permeation chromatography with tetrahydrofuran as solvent. SPE elutes as a single peak before other components of the extract, and is quantitated by a refractive index detector. The relative standard deviation for samples containing 11–60% SPE (dry weight basis) is 2%. The SPE is a mixture of sucrose hexa-, hepta-, and octa-esters with C₁₆ and C₁₈ fatty acids.     

Analysis of free malondialdehyde in photoirradiated corn oil and beef fat via a pyrazole derivative

Malondialdehyde (MA) formed in linolenic acid, linoleic acid, corn oil and beef fat upon photoirradiation was determined by gas chromatography (GC). The MA produced was reacted with methylhydrazine to give 1-methyl-pyrazole and was subsequently analyzed on a GC equipped with a nitrogen-phosphorus specific detector and a fused silica capillary column. MA values determined by this method correspond to free or unbound MA levels. Linolenic and linoleic acids produced 867 μg MA/g and 106 μg MA/g, respectively. Oleic and stearic acids did not produce detectable levels of MA upon photoirradiation. Amounts of MA produced after eight hour irradiations of corn oil and beef fat were 56.24 μg/g and 25.01 μg/g, respectively. Some photoreaction products in irradiated corn oil also were identified as methylhydrazine derivatives.     

Determination of Alcohol Ethoxylates derivatized with Naphthoyl Chloride,in Waste Water Treatment Plant Influent,Effluent and Sludge Samples by Liquid Chromatography Mass Spectrometry

A new analytical procedure for the determination of alcohol ethoxylates (AE) in environmental samples such as influents, effluents and sludge from waste water treatment plants (WWTPs) was developed. Although some work had been previously published on the detection of AE in water samples, this is the first paper that deals with AE in sludge. Alcohol ethoxylates were removed from water samples by sorption on polymeric discs followed by extraction with methanol. The methanol extracts were cleaned up with two alumina solid-phase extractions (SPE) at different conditions of solvent polarity, one before and the other after derivatization with naphthoyl chloride. A final polishing step was carried out on a Florisil SPE column. Liquid chromatography/mass spectrometry with electrospray ionization was used to quantify AE as naphthoyl derivatives. The detection limits for AE ethoxymers range from 0.07 to 0.005 μg/L in water samples. The method was applied to an Italian WWTP in order to follow the fate of AE during treatment, AE concentrations of 839 μg/L, 0.46 μg/L and 10.6 mg/kg were respectively found in the inlet, outlet and sludge samples. AE removals of each ethoxymer in the plant were in the range 99.6–100% and no difference was observed between high or low-mole ethoxymers and between AE with odd or even carbon chain lengths. An overall 99.7% removal was also determined on the mass balance of AE in the inlet, the outlet, and sludge of the plant.     

Light-scattering detection of phospholipids resolved by HPLC

An improved method for the analysis of phospholipids by normal-phase HPLC is described. Addition of methanol and acetonitrile to a gradient based on 2-propanol/hexane/water promoted a rapid separation of major classes of bovine surfactant phospholipids (PL) by using a conventional silica column. The use of an ELSD permitted an accurate analysis of a mixture of PL. Calibration curves were linear within the range of 5–40 μg with detection limits below 1 μg for PE and PC, and CV ranged from 0.6 to 9.6%. PL present in surfactant homogenates were separated by a solid-phase extraction (SPE) procedure before HPLC analysis. This methodology gave a recovery of 95% and combined SPE-HPLC and quantification of biological PL within a 30-min run. The use of ELSD detection of the eluted compounds was precise, linear, and sensitive.     

Quantitative determination of diesel oil in contaminated edible oils using high-performance liquid chromatography

A simple and reliable high-performance liquid chromatography method for the analysis of diesel oil in contaminated edible oils is described. Analysis performed using a diol column with a mobile phase of heptane and isopropanol (94∶6, vol/vol). Although baseline separation between diesel and other background fluorescent components was not achieved, quantitation was still possible using baseline integration. The method is linear over the range of 5–1000 μg/g with a correlation coefficient (r ²) of 0.9984. Average recoveries from spiked edible oils were 94.4–101.3%, with a limit of quantitation (LOQ) of 5 μg/g for sunflower oil, palm olein, and groundnut oil. Corn oil has a higher content of ester components, thus, LOQ was slightly worse (40 μg/g). The applicability of the method was confirmed by gas chromatography-mass spectroscopic detection to show the presence of diesel hydrocarbons in the suspected contaminated crude palm oil. This procedure provides a simple and sensitive method for determining diesel oil concentration in contaminated edible oils without prior sample cleanup or extraction.     

Detection of polycyclic aromatic hydrocarbons in commonly consumed edible oils and their likely intake in the Indian population

Edible oils such as coconut, groundnut, hydrogenated vegetable, linseed, mustard, olive, palm, refined vegetable, rice bran, safflower, sesame, soybean, and sunflower were analyzed for the presence of light and heavy polycyclic aromatic hydrocarbon (PAH) residues using liquid-liquid extraction, cleanup on a silica gel column, and resolution and determination by HPLC using a fluorescence detector. Ten PAH viz. acenaphthene, anthracene, benzo(a)pyrene, benzo(e)pyrene, benz(ghi)perylene, chrysene, coronene, cyclopenta(def)phenanthrene, phenanthrene, and pyrene were monitored. Analysis of 296 oil samples showed that 88.5% (262) samples were contaminated with different PAH. Of 262 contaminated edible oil samples, 66.4% of the samples showed PAH content of more than the 25 μg/kg recommended by the German Society for Fat Science. The total PAH content was highest in virgin olive oil (624 μg/kg) and lowest in refined vegetable oils (40.2 μg/kg). The maximum content (265 μg/kg) of heavy PAH was found in olive oil and the minimum (4.6 μg/kg) in rice bran oil. Phenanthrene was present in 58.3% of the oil samples analyzed, followed by anthracene (53%). Among the heavy PAH, benzo(e)pyrene was observed in 31.2% of the samples followed by benzo(a)pyrene (25.5%). The intake of PAH was highest through olive oil (20.8 μg/day) followed by soybean oil (5.0 μg/day) and lowest through refined vegetable oil (1.3 μg/day). Based on these monitoring studies, international and national guidelines for permissible levels of PAH can be prepared so as to restrict the intake of these toxic contaminants.     

Fast analysis of rapeseed glucosinolates by near infrared reflectance spectroscopy

Industry and plant breeders require fast methods to analyze glucosinolates in rapeseed. We tested the potential of near infrared reflectance spectroscopy (NIRS) for this analysis and developed calibration equations on a large population of whole seeds. Reference methods used are high performance liquid chromatography (HPLC) and gas liquid chromatography (GLC) of desulphoglucosinolates, a glucose-release method after purification on an anion exchange column and a palladium test. In the range from 2 to 107 μM/g and after transformation of the data in first derivative, a correlation coefficient of 0.99 was observed, as well as standard errors of estimated values of 2.15, 2.52, 2.67 and 4.07 for samples analyzed by HPLC, GLC, glucose and the palladium test, respectively. With different wavelengths, a limited calibration test on seeds containing from 4 to 40 μM/g gives a standard error of 1.91 μM/g (HPLC).     

Separation of α-tocopherol and its oxidation products by high performance liquid chromatography

A very sensitive high performance liquid chromatographic (HPLC) method was developed for the separation of α-tocopherol (α-T) and its five oxidation products: α-tocopheryl quinone (TQ), dimer (D), dihydroxy dimer (DHD), trimer (T) and 9-methoxy-α-tocopherone commonly called α-tocopheroxide (TO). The separation was achieved on a normal-phase silica-based column (Ultrasphere-Si), using a mobile phase of hexane/chloroform/isopropanol (95∶4.5∶0.5, v/v/v) at a flow rate of 0.4 ml/min, and the eluants were monitored simultaneously at their maximum absorptions using a variable-wavelength UV detector. The minmum detection limit is 0.01 μg for α-T, TQ and TO, 0.05 μg for DHD and D, and 0.1 μg for T/injection. This normal-phase method has the combined advantages of being very sensitive, fast and capable of separating all six compounds at the same time.     

Separation and analysis of phospholipids in different foods with a light-scattering detector

A method for the separation of phospholipids (PL) from total lipids by solid-phase extraction (SPE) with reversephase C₈ cartridges is described. The method was validated with a standard mixture of PL and applied to natural food matrixes, such as egg, chicken meat, salami, and ripened cheese. The recovery of PL ranged between 93 and 99.7% and was evaluated by an organic phosphorus spectrophotometric determination. The egg powder PL fraction obtained by SPE contained about 20% (w/w) nonpolar PL material when 100–150 mg of lipids were loaded onto the cartridge. Higher percentages of nonphospholipid components (30–43%) were obtained when the amount of lipids loaded was below or above the 100–150 mg range. The purified PL fractions were analyzed by high-performance liquid chromatography (HPLC) with an evaporative light-scattering detector. Good HPLC performance was observed even with low-purity SPE fractions (43% nonphospholipid material).     

甲苯洗液中硝基间甲酚的分离与测定

用气相色谱法分离、测定甲苯洗液中的 4-硝基间甲酚和 6-硝基间甲酚。色谱柱为 5 % OV-1 0 1 /chromosorb W/AW DMCS。以γ- 666为内标物 ,方法简便、快速。方法的建立为甲苯洗液中的4-硝基间甲酚和 6-硝基间甲酚的回收工艺提供了可靠的质控分析手段     

Gram-scale preparative HPLC of phospholipids from soybean lecithins

A preparative procedure has been developed to isolate gram quantities of phospholipid classes from soybean lecithins. Various steps taken to accomplish the isolation are described—an analytical method with silica column and light scattering detector, alcohol fractionation of deoiled lecithins, and columns with increasing internal diameters but packed with the same stationary phase. The loading study showed that it was possible to inject 20 mg on a 100 × 8 mm RadialμPorasil colume. The separation was scaled up to a 25-mm i.d. column and finally to a 50-mm i.d. column. With the larger column, 2.1 g of phospholipids were separated. The collected fractions (phosphatidylethanolamine, phosphatidylinositol, phosphatidic acid and phosphatidylcholine) were of high purity (>99%). The solvent consumption was 7.2 L (separation and column equilibration), and a minimum of 10 g of polar lipids can be separated daily. Presented at the 82nd American Oil Chemists’ Society Annual Meeting, May 13–15 1991, Chicago, IL.     

Determination of plasma tocopherols by gas liquid chromatography

A method is described for the separation and determination of plasma tocopherols by gas liquid chromatography (GLC). Proteins in 0.1 g samples of plasma were precipitated with ethanol containing a known amount of 5,7-dimethyltocol which served as an internal standard. Tocopherols were extracted into petroleum ether, purified by thin layer chromatography and analyzed as trimethylsilyl ethers by gas liquid chromatography (GLC) on 0.5% Apiezon L. Recoveries of α- and γ-tocopherols averaged 100% and 93%, respectively. The mean total tocopherol content of eight human plasma samples was 8.5 μg/g by GLC and 9.9 μg/g by a ferric chloride-α,α′-dipyridyl method. The α- and γ-tocopherol contents of 16 human plasma samples ranged from 4.0 to 12.3 μg/g and 0.6 to 2.1 μg/g, respectively.     

GC determination of synthetic hydrocarbon-based thermal heating fluid in vegetable oils

A combination of alumina column chromatography and GC procedures was developed for the determination of synthetic hydrocarbon-based thermal heating fluid (trademarked as Therminol 55^™) in vegetable oils. In each run, 3 g of sample solution was loaded onto the alumina (50 g) column and was eluted with 200 mL hexane. The eluate was then concentrated to 1 mL with the aid of a nitrogen stream prior to GC analysis. The GC chromatogram of the thermal heating fluid was characterized by the presence of a bell-shaped hump that could not be resolved into individual peaks. The lowest detection limit based on various spiked palm olein samples was 20 μg/g. The CV obtained were 6.5–8.9% for the intra-day study and 8.1–9.7% for the inter-day study. Overall recoveries of these samples ranged from 68.0 to 85.7% and the method was found to be good enough for quality control purposes.     

High performance liquid chromatographic analysis of 1-alkyl-2-acyl- and 1-alkyl-3-acyl-sn-glycerols

A high performance liquid chromatographic (HPLC) method is described for separation and quantitation of 1-alkyl-3-acyl- and 1-alkyl-2-acyl-sn-glycerol, products of the detritylation reaction of 1-alkyl-2-acyl-3-trityl-sn-glycerol. The alkyl glycerides were separated on a 25 cm×4.6 mm ID column packed with ∼5–6 μm silica and eluted isocratically with isooctane/isopropanol (98∶2, v/v) as mobile phase. The good separation and linear refractive index (RI) detector responses using cholesterol as an internal standard indicated the applicability of the method not only for the quantitative determination of the alkylglycerols but also for their semipreparative isolation. This HPLC method shows excellent reproducibility and accuracy and is applicable to other types of glycerides such as mono- and diacylglycerols. Presented in part at the AOCS annual meeting, Honolulu, Hawaii, May 1986.     

Analysis of Polycyclic Aromatic Hydrocarbons in Egyptian Petroleum Condensate Oils

The polycyclic aromatic hydrocarbons (PAH) in Egyptian condensates are analyzed for the first. A solid phase extraction (SPE) followed by gas chromatography-mass selective detection was used for their analysis. The method was calibrated for optimal extraction conditions. Excellent recoveries were found (78–114%) for the PAHs that were identified using a variety of standards and GC-MS spectra. The solid-phase extracted PAH fraction was further separated by HPLC on a Ag(I) mercaptopropanosilica gel to reduce the complexity of the sample by separating the PAHs based on the number of aromatic rings. The analytes were quantified using GC with a flame ionization detector. For this kind of sample SPE is a more convenient separation technique than an open column. PAHs containing two to four rings in the concentration range 0.6–11 μg/L were measured. Some preliminary geochemical hypotheses based on the analyzed PAHs and the previously analyzed S-containing aromatic compounds were formed as to the depositional environment and source rock type.     

废水中均苯四甲酸的回收与测定

用重氮甲烷酯化气相色谱内标法测定从废水中回收的均苯四甲酸。色谱柱为5%OV-17/ChromosorbW/AWDMCS,邻苯二甲酸二甲酯为内标,方法简便、快速。该方法为废水中均苯四甲酸的回收工艺提供了可靠的质控分析手段。     

Quantitative analyses of methyl esters of fatty acid geometrical isomers,and of triglycerides differing in unsaturation,by the Iatroscan TLC/FID technique using AgNO3 impregnated rods

The relative FID responses for Iatroscan analyses ofcis andtrans isomers of methyl esters of 18∶1†6, 18∶1†9 and 18∶1†11 on Chromarods-S impregnated with AgNO₃ were studied at load levels ranging from 0.5 to 20 μg, using methyl stearate as internal standard. The FID response correction factors were greater for thecis than for thetrans isomers. The correction factors were relatively constant in the 10–20 μg interval, but increased in the range 0.5–5 μg. Separation of tristearin, triolein, trilinolein and trilinolenin also was obtained on Chromarods-S impregnated with AgNO₃ using a mixture of benzene: chloroform: acetic acid (90∶8∶2) as the solvent system. The relative FID responses for the triolein, trilinolein and trilinolenin were determined at load levels ranging from 0.5 to 14.3 μg using tristearin as an internal standard. The FID response correction factors of these three triglycerides differed significantly for load levels of 1.0, 2.5 and 5.0 μg. However, the factors could be considered as being equal in the range 10 to 14.3 μg. Correction factors were not affected by repeated re-use of the same set of Chromarods. Several hundred separations and scans appeared feasible.     

固相萃取和高效液相色谱法测定水果中的糖

研究了高效液相色谱法测定水果中的糖。水果样品的糖提取液用WatersSep Pak C1 8固相萃取小柱预分离 ,以WatersSugar Pak- 1 钙型阳离子交换柱为固定相 ,0 .0 5 g·L- 1 EDTA钙钠水溶液为流动相分离 ,示差折光仪为检测器检测。蔗糖、葡萄糖和果糖的检测限分别为 2mg/L、4mg/L和 4mg/L ,相对标准偏差在 0 .76%～1.8%之间 ,标准回收率在 97%～ 10 3 %之间。方法用于几种水果样品的测定 ,结果满意。     

电还原邻硝基苯酚合成邻氨基苯酚的高效液相色谱分析法

建立了一种反相高效液相色谱法同时测定邻硝基苯酚和邻氨基苯酚的新方法。采用Shim-pack VP-ODS(250 mm×4.6 mm,4.6μm)色谱柱,选用纯甲醇为流动相,以285 nm为检测波长,流速为0.8 m L/min,柱温为35℃,以外标法进行定量分析。实验结果表明,邻硝基苯酚和邻氨基苯酚的质量浓度在1.0~40.0μg/m L范围内呈良好的线性关系,其相关系数分别为r=0.999 5(n=9)和r=0.999 8(n=9),测定其在10.0、20.0和30.0μg/m L这3个不同质量浓度下的方法精密度,其相对标准偏差分别≤1.28%和≤1.04%。将本方法应用于以邻硝基苯酚为原料电解合成邻氨基苯酚反应液的分析,其加标回收率分别在93.0%~105.6%和90.6%~106.2%之间,相对标准偏差分别≤3.75%和≤1.44%。实验结果表明,该方法可用于邻硝基苯酚和邻氨基苯酚两种组分的同时测定。