Normal-phase High-performance Liquid Chromatography Research Articles

GLYCOSYLATION FEATURES OF FOLLITROPIN DELTA (REKOVELLE®) MORE RESEMBLE THOSE OF NATURAL HUMAN FSH COMPARED TO FOLLITROPIN ALFA (GONAL F®).

Compare the glycosylation properties of follitropin delta, from a human cell line, with those of natural human derived FSH and with follitropin alfa from a hamster cell line. Follitropin delta (Rekovelle®) produced in PER.C6® human derived cell line, follitropin alfa (Gonal f®) produced in CHO derived cell line and natural human urinary derived FSH (Bravelle®) were used in the study. Isoelectric Focusing (IEF), was used to resolve and profile the isoforms present in FSH preparations. IEF was carried out using a gel with a pH range between pH 3-7. Glycans were released from FSH preparations by enzymatic digestion with PNGase and derivatized with 2-aminobenzamide (2AB). Glycans were sequenced with specific exoglycosidases and analysed using normal phase HPLC and weak anion exchange chromatography. A more acidic isoform profile was obtained by IEF for follitropin delta and human derived FSH in comparison to follitropin alfa. Compared to follitropin alfa, the released glycans from follitropin delta and natural human FSH both show higher abundance of tri- and tetra-antennary forms and a lower abundance of the di-antennary forms. Sialylation of glycans on follitropin delta and natural human FSH comprises both α2,3 linked and α2,6 linked sialic acid, whereas follitropin alfa exhibits only the α2,3 linked form. The resemblance of follitropin delta glycans to the human derived FSH was further supported by the presence of N-acetylgalactosamine (GalNAc) and bisecting N-acetylglucosamine (GlcNAc) which are absent in CHO-derived FSH (Table). Follitropin delta glycosylation is richer and more complex compared to follitropin alfa with a higher proportion of tri- and tetra-antennary and charged glycans, as well as by the presence of α2,6-linked sialic acid, GalNAc residues and bisecting GlcNAc. In these ways follitropin delta shares numerous glycosylation features and more resembles natural human derived FSH.

Simultaneous determination of α-tocopherol, β-tocopherol, γ-tocopherol, δ-tocopherol, sesamin, sesamolin, sesamol, and asarinin in sesame oil by normal-phase high performance liquid chromatography

A simple and fast normal-phase high performance liquid chromatography method for simultaneous detection of α-tocopherol, β-tocopherol, γ-tocopherol, δ-tocopherol, sesamin, sesamolin, sesamol, and asarinin in sesame oil (SO) was investigated. Conditions were a silica gel column as the separation unit, n-hexane and tetrahydrofuran (93:7, v/v) as the mobile phase, isocratic elution, a flow rate of 0.8 mL/min, column temperature of 30 °C, and florescence detector with excitation and emission wavelengths of 295 and 330 nm. SO samples were directly dissolved in n-hexane for HPLC analysis. Results showed that the method performed wide linear ranges and good linearity (0.27–100.0 μg/mL, R2 > 0.9996), low limits of detection (0.09–0.16 μg/mL) and quantification (0.27–0.41 μg/mL), good precision and accuracy (biases of <2.83 % and relative standard deviations of <3.77 %), good separation performance [resolution factor (1.66–6.20), separation factor (1.11–3.94), retention factor (1.08–1.42), and height of theoretical plates (0.01–0.04 mm)], and satisfactory recoveries (87.3–109.8 % for SO and 96.5–106.9 % for lard). The method was successfully applied for the simultaneous determination of the eight analytes in eleven SO samples.

Chiral HPLC separation of enantiomeric blebbistatin derivatives and racemization analysis in vertebrate tissues

Simple and consistent chiral HPLC methods for the efficient separation of enantiomeric blebbistatin derivatives, namely parent compound blebbistatin and derivatives 4-nitroblebbistatin, 4-aminoblebbistatin, 4-dimethylaminoblebbistatin, and 4-t-butylblebbistatin were developed using cellulose tris(3,5-dimethylphenylcarbamate) as a stationary phase (Lux cellulose-1 column). Blebbistatin, 4-aminoblebbistatin, and 4-dimethylaminoblebbistatin racemates were well-separated in normal-phase HPLC conditions while 4-nitroblebbistatin and 4-t-butylblebbistatin were effectively separated in both normal- and reversed-phase HPLC conditions. Furthermore, the order of elution of enantiopure compounds was found to be independent of mobile phase compositions and conditions used, and solely depends on the interaction between the enantiomer and the chiral stationary phase. We found that despite the chiral center being present far from the D-ring in the blebbistatin structure, the D-ring substitutions prominently affect the chiral separation. Ex vivo racemization studies of the most popular blebbistatin derivative (S)-(–)-4-aminoblebbistatin in rat blood and brain tissues revealed that the compound does not convert into the inactive enantiomer. This confirms that (S)-(–)-4-aminoblebbistatin is a useful tool compound in cellular and molecular biology studies without the risks of racemization and degradation effects.

Tissue N-Glycan Analysis Using LC-MS, MS/MS, and MSn.

Tissue glycans usually contain various structures, from simple to highly complicated, in different quantities. N-Glycans are particularly heterogeneous, with up to pentaantennary structures, different branch sequences, and several isomeric structures. 2-Aminopyridine (PA) tagging on released N-glycans is useful for separating isomers and to quantitatively analyze both the major and minor glycan structures in tissues using reversed-phase liquid chromatography (LC)-mass spectrometry (MS) and MS/MS analysis. Because the structural differences of PA-N-glycans influence their retention on a reversed-phase C18 column, it is easy to deduce the core structure, including core Fuc and bisecting GlcNAc as well as the branching pattern of each PA-N-glycan, based on the results of elution position, full MS, and MS/MS analysis. If more detailed structural analysis is required, combining sequential exoglycosidase digestions, sialic acid linkage-specific alkylamidation (SALSA), and/or SALSA/permethylation is useful for determining glycosidic linkages of branches. This article includes detailed protocols for the preparation of N-glycans released from glycoproteins/glycopeptides by glycoamidase F or hydrazinolysis, PA-tagging of N-glycans, fractionation with anion-exchange chromatography, and chemical or enzymatic modifications of PA-N-glycans, as well as reversed-phase LC-MS, MS/MS, and MSn analysis of PA-N-glycans from tissues. © 2021 Wiley Periodicals LLC. Basic Protocol 1: Preparation of released N-glycans from tissue samples using glycoamidase F Alternate Protocol: Preparation of released N-glycans from tissue samples by hydrazinolysis Basic Protocol 2: PA-tagging of N-glycans and sample cleanup Support Protocol 1: Monitoring of PA-N-glycans using normal-phase HPLC Basic Protocol 3: Anion-exchange chromatography of PA-N-glycans Basic Protocol 4: Sequential exoglycosidase digestions Basic Protocol 5: Determination of Sia-linkages by SALSA Support Protocol 2: Cotton-HILIC solid-phase extraction to remove reagents for alkylamidation Basic Protocol 6: Sequential modifications of glycans with SALSA and permethylation Basic Protocol 7: LC-MS and MS/MS analysis of PA-N-glycans (before permethylation) Basic Protocol 8: LC-MS, MS/MS, and MSn analysis of PA-N-glycans (after permethylation).

Anthraquinone Derivatives and its Antibacterial Properties from Paederia foetida Stems

Background: Paederia foetida (Rubiaceae) locally known as Chinese fever vine is a prominent plant species in the east and south Asia. The extract of Paederia foetida Linn. has been used for the treatment of gastric infections or other digestive disorders in Chinese traditional medicine. Objective: The main aim of the study was to isolate bioactive constituents of P. foetida stem through a bio-guided assay, then evaluate their antibacterial activity and compare them with standard agents. Materials and Methods: The stems of P. foetida were extracted by methanol and successively partitioned with ethyl acetate and n-butanol. The ethyl acetate layer further fractionated using column chromatography and normal phase HPLC. The chemical structures of the isolated compounds were elucidated through comparison of the 1H and 13C NMR and MS spectral data with the literature. The antibacterial activity of P. foetida stem was evaluated using agar well diffusion assay and resazurin based micro-dilution technique. Results: Ten compounds were isolated from the Chinese fever vine stem including four anthraquinones, morindaparvin A (1), 1,3-dihydroxy-2-methoxyanthraquinone (2), digiferrol (3), and alizarin (4); two steroids, β-sitosterol (5), and stigmastan-3-one (6); two coumarins, scopoletin (7) and fraxidin (8) and two aromatics, ferulic acid (9) and vanillic acid (10). The four anthraquinones 1-4 were isolated for the first time from Chinese fever vine stem. Compound 2 and 3 significantly inhibited Staphylococcus aureus with MIC values 18.75 and 9.37 μg/mL respectively, and streptomycin (1.8 μg/mL) was used as a positive control. Conclusion: Compound 2 and 3 can be considered as a prospective candidate for the treatment of staphylococcal bacterial infections in both human and animals.

The Influence on Phenolic, Aroma Compounds, Rheological and Sensory Properties of Chocolates by Different Strains Inoculated Fermentation

Four designed cocoa fermentations were conducted in separated wooden boxes with different strains inoculum. One was spontaneous fermentation with natural occurring microorganisms, another was inoculated with Saccharomyces cerevisiae, another was inoculated with Lactobacillus plantarum, and the other was inoculated with Acetobacter aceti. The experimental parameters, including the fermenting cocoa mass temperature, the pH value, the total acidity of the pulp and cotyledons of cocoa beans, along with the fermentation time were determined. Furthermore, the phenolic compounds (flavanols and procyanidins DP1-10) of chocolates were determined by normal phase HPLC. In addition, the rheological, textural properties, and color parameters of the chocolates were measured. Meanwhile, the electronic nose was used to analyze the aroma compounds of the investigated chocolates and the principal components analysis (PCA) was conducted to distinguish the flavor profiles among the chocolates. The consumer sensorial assessment was carried out to evaluate the organoleptic properties of chocolates and their overall acceptability. The quality of chocolates produced by the defined inoculum varied with each other with the exception of the FP and PAC content. Different inoculated fermentation methods affected the rheological, textural properties, and color parameters of the end product chocolates. Furthermore, they influenced the types and numbers of aroma compounds generated during fermentation. However, the impact is mainly on their levels of aroma compounds. From sensory point of view, chocolates produced from inoculated Acetobacter aceti BCRC12324 during fermentation had the highest score point of overall acceptability among the investigated chocolates. The high levels of 2-methylbutanal content occurred in this chocolate could be an adequate reply of this finding. The quality of chocolate from fermentation with Lactobacillus plantarum B0091 inoculum was similar to the others, but some properties such as rheological, textural, and flavor profiles were inferior and less pronounced, leading to a slightly poorer response by the sensory panel. PCA successfully discriminates the aroma profiles into four groups, providing a better visualization of the variation among the chocolates produced by the different strains. This attempt to manipulate the strains during cocoa fermentation is a new approach in Taiwan chocolate industry. By controlling the starter culture of fermentation properly, we could improve the quality and flavor profiles of chocolate with a consistent and more reliable production.

Stevia rebaudiana germplasm characterization using microsatellite markers and steviol glycosides quantification by HPLC

Stevia rebaudiana Bertoni, Asteraceae, is an herbaceous perennial plant native to Paraguay. This species is considered since ancient times a medicinal plant with important bioactive compounds and pharmacologic and food properties, namely diterpenes glycosides. The high natural sweetener potential stevioside and rebaudioside A produced by S. rebaudiana plants are suitable sucrose substitutes, and their obtention is influenced by environmental, phytosociological, and genetic factors. The plants’ genetic profile and sweet potential depiction are needed for suitable plant selection for improvement and deployment. Thirty-one S. rebaudiana accessions grown in the same plot where leaves samples were collected in early 2019, were genotyped using six microsatellite markers, including two steviol glycosides biosynthesis functionally involved markers. Additionally, an aqueous extract of each sample was obtained in a water bath and purified by SPE for stevioside and rebaudioside A quantification by normal phase HPLC. Stevioside and rebaudioside A contents varied between 0.53–7.36% (w w−1) and 0.37–3.60% (w w−1), respectively. Two genotypes displayed interesting ratios of rebaudioside A/stevioside (number 3 and 33). The level of genetic similarity between genotypes was tested through a pairwise similarity coefficient, and two groups of individuals had the same fingerprinting. Strong relatedness was found within genotypes, possibly due to cloning, thus, influx of new germplasm ought to be made to prevent mating between relatives, and for further selection and genetic improvement.

Fast detection of adulteration of aromatic peanut oils based on alpha-tocopherol and gamma-tocopherol contents and ratio

A fast method based on normal-phase high-performance liquid chromatography with UV detection was applied to determine the tocopherols in aromatic peanut oil (APO) and four refined vegetable oils (soybean, sunflower, maize, and rapeseed oils). Our results showed that the tested oils varied greatly on the content of tocopherol isomers, especially on α- and γ-tocopherol concentrations. Consequently, (α+γ)-tocopherol (297.9–393.2 mg kg−1) and α-/γ-tocopherol (1.05–2.13) were successfully applied as discriminating parameters for detecting the adulteration of APO with above four refined vegetable oils. Furthermore, APO was mixed with the four oils (at the levels of 5, 10, 15, 20 and 25 g/100 g, w/w) to determine whether the tocopherol analysis is a better approach than fatty acid profiling for detecting APO adulteration. Our results showed that for tocopherols, our detection limits were 5 g/100 g for soybean oil and 10 g/100 g for other three oils in APO, showing a higher sensitivity than fatty acids profile based method for detecting APO adulteration. Thus, our newly developed method is an alternative and innovative tool for fast and cost-effective detection of the adulteration of APO with soybean, sunflower, maize, and rapeseed oils.

Normal-Phase HPLC-ELSD to Compare Lipid Profiles of Different Wheat Flours

Normal-phase high-performance liquid chromatography (HPLC) is widely used in combination with evaporative light scattering detection (ELSD) for separating and detecting lipids in various food samples. ELSD responses of different lipids were evaluated to elucidate the possibilities and challenges associated with quantification by means of HPLC-ELSD. Not only the number and type of polar functional groups but also the chain length and degree of unsaturation of (free or esterified) fatty acids (FAs) had a significant effect on ELSD responses. Tripalmitin and trilinolein yielded notably different ELSD responses, even if their constituting free FAs produced identical responses. How FA structure impacts ELSD responses of free FAs is thus not predictive for those of triacylglycerols and presumably other lipids containing esterified FAs. Because ELSD responses of lipids depend on the identity of the (esterified) FA(s) which they contain, fully accurate lipid quantification with HPLC-ELSD is challenging and time-consuming. Nonetheless, HPLC-ELSD is a good and fast technique to semi-quantitatively compare the levels of different lipid classes between samples of comparable FA composition. In this way, lipid profiles of different flours from near-isogenic wheat lines could be compared.

Analysis of volatile oxidized oligomers from polyolefins by off-line normal phase high performance liquid chromatography and one-dimensional and comprehensive two-dimensional gas chromatography

The off-line coupled high performance liquid chromatography - gas chromatography - mass spectrometry (HPLC-GC–MS) was used for the analysis of oxidized oligomers from polyolefins. In order to optimize the HPLC fractionation method, a complex substance mixture of volatile organic compounds (VOC) from the provoked thermal oxidation of polyethylene (PE) was investigated. The fractionation was performed by normal phase HPLC, which separated the analytes according to their polarity. The seven obtained fractions were transferred off-line to the GC–MS. By means of fractionation nearly all coelutions present in the total extract could be avoided, which facilitated the identification of substances considerably. In addition, a separation according to functional moieties of substances was achieved, resulting in homologous series of compounds in the individual fractions: polyolefin oligomeric hydrocarbons (POH) in fraction 1, aldehydes and 7-, 6-, and 5-ketones in fraction 3, 2-ketones and alkenals in fraction 4, lactones and carboxylic acids in fraction 5, 1- and 2-alcohols in fraction 6 and diones in fraction 7, respectively. In this work, 7-, 6- and 5-ketones, δ-lactones, 2-alcohols and diones were identified for the first time in oxidized PE. Verification of fractionation and substance identification was done by comprehensive two-dimensional gas chromatography - time of flight - mass spectrometry (GCxGC-TOF-MS) measurements as well as off-line HPLC-GC–MS measurements using a mixture of reference substances. The fractionation approach was applied for the analysis of a commercial PE film after melt flow extrusion. POH were eluted in fraction 1, while n-aldehydes (with a carbon chain length of C11-18) were identified in fraction 3 and 2-ketones (C13-15) in fraction 4. The amounts of the individual detectable oxidized oligomers were estimated semi-quantitatively to range from 10 – 170 µg/kg.

Effects of Processing Time and Temperature on Flavanol and Procyanidin, Proanthocyanidin and Antioxidant Activity of Cocoa Bean in Taiwan

Flavanol in cocoa is beneficial to cardiovascular health. This study investigated the effect of roasting conditions, temperature ranging from 110 to 150°C and time duration 15-35 min, on the level of flavanol and procyanidin (FP), total proanthocyanidin (PAC) and antioxidant activity of fermented cocoa beans in Southern Taiwan. The content of FP in unroasted and roasted cocoa bean was determined by the normal phase HPLC method and the antioxidant activity was assayed by DPPH and ABTS methods. High roasting temperature for long time decreased the content of FP and PAC in cocoa beans, where ranged from 55.30±1.95 mg (-)-epicatechin equivalents /g and 103.56±8.33mg procyanidin B1/g (at 110°C for 15 min) to 19.12±0.66 mg (-)-epicatechin equivalents /g and 51.58±0.86 mg procyanidin B1/g (at 150°C for 35 min), respectively. Meanwhile, as the roasting temperature rose, the DPPH and ABTS free radical scavenging ability of roasted cocoa bean extracts decreased gradually, varying from the maximum (IC50 = 104±2 µg/ml and 50.4±1.1mg TE/g) for unroasted bean to the minimum (IC50 = 144±4 µg/ml and 27.7±2.4 mg TE/g), and then slightly increased to IC50=134±4 µg/ml and 31.5±0.7 mg TE/g, respectively at most severe roasting treatment, showing the formation of melanoidins and polyphenols caused the synergistic effect, leading to the rise of the antioxidant activity. The first order kinetic reaction and the Arrhenius equation were applied to forecast the change of FP concentration during roasting. The activation energy of FP degradation is 11.2 kcal/mol. The obtained kinetic equation could be useful to predict the remaining amount of FP in cocoa beans under the designed experiment. The cocoa products with higher flavanol content and antioxidant activity could be possible by setting appropriate roasting conditions.

Therapeutic drug monitoring of olanzapine: Easy and reliable method for clinical correlation

AIM:The current work establishes an easy, reliable technique for the estimation of serum Olanzapine concentration which correlates it clinically.SUBJECTS AND METHODS:The work was agreed in 61 schizophrenic patients who were on olanzapine. Serum drug amount was estimated by normal-phase high-performance liquid chromatography and brief psychiatry rating scale was used to determine disease progression.RESULTS:Samples provided 61 patients, 40 were under sub-therapeutic range, 18 were under therapeutic range and 3 were above the therapeutic range.CONCLUSION:Therapeutic drug monitoring must be a part of clinical practice in psychiatric hospitals for optimizing the dose of an individual patient along with the correlation of serum concentration with the clinical assessment scales.

Impurity Profiling and Identification of 2,6-Diisopropylphenol by HPLC Method and Raman Spectroscopy Method.

Identification of 2,6-diisopropylphenol by Raman spectroscopy using the TruScan Raman spectrum is validated by specificity test and robustness. HPLC assay method is developed to detect the 2,6-diisopropylphenol and its impurities A =determination of 2,6-diisopropylphenol; its main impurities related compound A =2,6-diisopropylphenyl isopropyl ether, related compound B=2,6-diisopropylquinone, and related compound C=3,3'-5,5'-tetraisopropyl diphenol; and unknown impurities done by HPLC method. Related compound A and C determination has been developed by normal phase HPLC; good resolution peak shapes have resulted from the peak results. The limit of impurities A and C is reported to be 0.05% and 0.03%, and the limit of impurity B is also detected by using the same above procedure, but the column has been changed for the maximum wavelength detection and better elution from the peak results. The reported impurity level was 0.02%, the unknown impurity limit was 0.0149%, and the total impurity level of 2,6-diisopropylphenol was reported to be 0.06% which are in the threshold limit level. It specifies that the drug is safe and efficient without any toxicity.

Chromatographic evaluation of tocols and sterols of processed canola oil and deodorizer distillate.

Tocopherols and tocotrienols in the combined form are known as tocols. Changes of total and individual tocols and sterols concentration of canola oil and deodorizer distillate (DD) during different processing stages were evaluated with the application of gas chromatography (GC) and high-performance liquid chromatography (HPLC). For sterols analysis, GC coupled with flame ionization detector (FID) was used while tocols in canola oil samples and DD, normal phase (NP) HPLC was applied. The results of the present study indicated that levels of total and individual tocols and sterols content were decreased during processing (neutralization to deodorization). Deodorization was found to be the most effective process for the reduction of total sterols and tocols as 55.9% and 34.2%, respectively. A high amount of tocols and sterols was observed in DD. Among tocols and sterols; beta tocopherol (β-T) and β-sitosterol were found to be in greater concentration 53.97% and 31.82%, respectively. Therefore, DD could be used as a valuable by-product in the cosmetics and food industries.

Identification of unusual phospholipids from bovine heart mitochondria by HPLC-MS/MS

Phospholipids, including ether phospholipids, are composed of numerous isomeric and isobaric species that have the same backbone and acyl chains. This structural resemblance results in similar fragmentation patterns by collision-induced dissociation of phospholipids regardless of class, yielding complicated MS/MS spectra when isobaric species are analyzed together. Furthermore, the presence of isobaric species can lead to misassignment of species when made solely based on their molecular weights. In this study, we used normal-phase HPLC for ESI-MS/MS analysis of phospholipids from bovine heart mitochondria. Class separation by HPLC eliminates chances for misidentification of isobaric species from different classes of phospholipids. Chromatography yields simple MS/MS spectra without interference from isobaric species, allowing clear identification of peaks corresponding to fragmented ions containing monoacylglycerol backbone derived from losing one acyl chain. Using these fragmented ions, we characterized individual and isomeric species in each class of mitochondrial phospholipids, including unusual species, such as PS, containing an ether linkage and species containing odd-numbered acyl chains in cardiolipin, PS, PI, and PG. We also characterized monolysocardiolipin and dilysocardiolipin, the least abundant but nevertheless important mitochondrial phospholipids. The results clearly show the power of HPLC-MS/MS for identification and characterization of phospholipids, including minor species.

ABOUT TRAINING IN THE DETERMINATION OF TOCOPHEROLS IN VEGETABLE RAW MATERIAL BY HPLC

Tocopherols, which are important biologically active substances, play the role of antioxidants. Synthesized tocopherols are usually in esterified form; their sample preparation for quantification by high performance liquid chromatography includes high temperature alkaline hydrolysis. Sample preparation of oil-containing objects having natural tocopherols in an unesterified form is carried out by direct extraction in a non-polar solvent. In this work, we determined the content of tocopherols in natural materials (the method of analysis of viscous particles) using the alkaline hydrolysis method and the direct extraction method in a non-polar solvent. It was shown that the use of normal-phase HPLC with a prepared extraction sample in hexane and low-temperature exposure allows us to determine both the total content of tocopherols and its individual forms. This option is less time consuming, requires fewer reagents, which significantly affects the cost of the analysis. It is possible to determine only the total number of tocopherols. At the same time, overestimated results were obtained, which are probably associated with the destructive destruction of both tocopherols and tocotrienols present in plants of plant origin, and one large peak, including all products, is observed in the chromatograms.

Determination of biodiesel and used cooking oil in automotive diesel/green diesel fuels through high-performance liquid chromatography.

This study reports a simple and convenient analytical method for the simultaneous determination of biodiesel and vegetable oils or used cooking oils in petrodiesel and green diesel (hydrotreated vegetable oils or paraffinic diesel). The approach is based on normal-phase high-performance liquid chromatography with refractive index detection. It employed silica stationary phase, n-hexane mobile phase with isopropanol modifier to achieve optimum separation between hydrocarbons (petrodiesel or green diesel), fatty acid methyl esters (biodiesel) and triglycerides (vegetable oils and used cooking oil). In addition to determining vegetable oils or used cooking oils as adulterants in diesel, this method is also proposed as a better alternative to the standard method ASTM D7371, which is currently recommended for determining fatty acid methyl esters in petrodiesel. The method development involved screening of various stationary and mobile phases, with and without modifiers, to achieve acceptable chromatographic resolutions between analytes. Under the optimized method conditions, silica column, and n-hexane containing 0.6% isopropanol as the mobile phase provided the best results. The real-world scenario was simulated for the method validation carried out by fortifying Jatropha seed oil, soybean oil, and used cooking oil in the biodiesel blended petrodiesel and green diesel. Measurement of all analytes was accompanied by high precision, low limit of detection/quantification and linear response range of 0.05 to 50% for biodiesel, and 0.05 to 30% for vegetable oils.The proposed method is simple, fast (runtime 7min), and does not require sample pre-treatment and backflushing.

Critical Evaluation of Methods for the Measurement of Oxidative Rancidity in Vegetable Oils

During storage and shipping, edible oils are susceptible to oxidative deterioration. To ensure high oil quality, it is essential to reliably analyze their oxidative status. The aim of this review was to critically evaluate published methods based on their value and applicability. This review focuses on major chemical, physical and chromatographic methods used for assessing the degree of lipid oxidation. Due to complexity of the mechanism of lipid oxidation, most of the methods determine either early or advanced oxidation products. Methods based on nuclear magnetic resonance spectroscopy, normal-phase high-performance liquid chromatography and high-performance size-exclusion chromatography are discussed as superior methods due to their capability of providing combined information about the extent of early and advanced oxidation stages.

Critical evaluation of methods for the measurement of oxidative rancidity in vegetable oils

During storage and shipping, edible oils are susceptible to oxidative deterioration. To ensure high oil quality, it is essential to reliably analyze their oxidative status. The aim of this review was to critically evaluate published methods based on their value and applicability. This review focuses on major chemical, physical and chromatographic methods used for assessing the degree of lipid oxidation. Due to complexity of the mechanism of lipid oxidation, most of the methods determine either early or advanced oxidation products. Methods based on nuclear magnetic resonance spectroscopy, normal-phase high-performance liquid chromatography and high-performance size-exclusion chromatography are discussed as superior methods due to their capability of providing combined information about the extent of early and advanced oxidation stages.

Studies of Rapid Determination of Vitamin E and Its Application on Natural Foodstuffs

The purpose of this study is to establish a rapid and exact method for the determination of tocopherols, and to estimate the tocopherol contents of common foods in Taiwan by the established method. I. Establishment of tocopherol analysis The analytical methods of tocopherols,including spectrophotometry,thin layer chromatography,gas chromatography and high performance liquid chromatography (HPLC),were evaluated.The tocopherol standards included α-,β-,γ-, and δ- tocopherol. Among these methods, the normal phase HPLC performed by the conditions as follows: column, Develosil SI60-5 (4.6 x 250mm); eluent, n-hexane:dioxane: ethanol (958:40:2, v/v/v)flow rate, 1ml/min;detector, UV 298nm was the best one for the tocopherol determination because of its good calibration, reproducibility,resolution and short time analysis. II. Quantitative determination of tocopherols in foods The investigated food materials included 48 common food samples in Taiwan and 5 capsule samples containing natural vitamin E. The food material was saponified with potassium hydroxide, then extracted with n-hexane and concentrated under nitrogen gas. The residue, dissolved in n-hexane to adjust an appropriate concentration, was prepared for the HPLC analysis. The sample was examined for the contents ofα-,β-,γ-, and δ-tocopherol, and therefore the vitamin E potency could be calculated. Among these food samples ,oils, legumes seeds , nuts,wheat germ , Oolong tea and Chiann-Shyr(seeds of Euryale ferox Salisb. ) showed a high tocopherol content. The foods showing a high α-tocopherol content were Oolong tea 46.2, Chiann-Shyr 41.6 , sunflower oil 27.2 , wheat germ , peanut 11.2, soybeanoil 10.2 , palm oil 8.5 and peanut oil 5.8mg/100g. The foods with a high content ofγ-tocopherol were soybean oil 78.5, sesame oil 43.2, sesame seed 22.7 , soybean 12.5, black bean 12.2 and peanut 7.2mg/100g. The contents ofβ-tocopherol on Chiann-Shyr and wheat germ were 18.1 and 9.8mg/100g. The vitamin E potency in the capsules of vitamin E and lecithin was 14.3-15.9 , or 5.2-5.9mg/100g respectively.