Determination of fatty acid and triacylglycerol composition of human adipose tissue.

The fatty acid composition of adipose tissue was studied in a population in western Andalusia with a diet in which the fat contribution is mainly from olive oil. The lipid composition of adipose tissue, including the fatty acid composition of triacylglycerols, was examined by capillary gas chromatography. Thirty-five peaks were resolved, ranging in chain length from 12 to 24 carbon atoms, including geometric and positional isomers. The major triacylglycerol was POO, followed by PLO and OOO.     

Determination of phospholipid fatty acid and triacylglycerol composition of rat caecal mucosa.

The lipid composition of rat caecal mucosa, including the fatty acid composition of phospholipids and triacylglycerols, has been examined by capillary gas chromatography. Thirty-seven peaks were resolved, ranging in chain length from 12 to 24 carbon atoms. Preliminary identification of fatty acids by comparison with authentic standards was confirmed by gas chromatography-mass spectrometry using electron-impact ionization. The neutral and polar components were examined. Fatty acid methyl esters were quantified in absolute amounts with respect to the percentage of total phospholipid and triacylglycerols. The results show significantly higher levels of 16:0, 18:0, 18:1(n-9), 18:1(n-7), 18:2(n-6) and 20:4(n-6) in phospholipids, and higher levels of 16:0, 18:1(n-9) and 18:2(n-6) in triacylglycerols. On the other hand, analysis of caecal triacylglycerols revealed sn-glycerol-palmitate-oleate-palmitate, sn-glycerol-palmitate-linoleate-palmitate and sn-glycerol-palmitate-linoleate-oleate as major components.     

Determination of moisture in cheese and cheese products

Variables related to oven-drying samples of cheese and cheese products to determine moisture content were examined to provide more efficient and reproducible methods. Over 6500 samples of cheese were analyzed in an effort to modify the current AOAC procedure. The gravity atmospheric oven was unsuitable for use in accurate moisture analysis because of wide temperature differentials within the oven cavity. Use of this for oven moisture determination resulted in higher variance, which corresponded to the high temperature variation within the oven. Cheese sample preparation using an Oster blender yielded consistently lower variance in final moisture content than did preparation of cheese samples with a hand grater, rotary grater, and plug and plunger. Sample size of 3 +/- 0.25 g maximized surface area-to-volume ratios and yielded a lower error in final moisture content because of better control of ambient weight loss rates. Use of combination of disposable 5.5 cm diameter aluminum sample pans with 5.5 cm diameter glass fiber filter pads for covers produced a smaller standard deviation for moisture analysis than did the AOAC pan and insert cover and filter paper covers. All pans must be pre-dried for at least 3 h at 100 degrees C, and the glass fiber covers should be pre-dried for 1 h under the same conditions. All dried pans and covers must be stored in a desiccator with active desiccant. Equipment upgrades from the existing AOAC standard methods provide safer more efficient methods of analysis.     

Chemical composition and molecular speciation of the triacylglycerol of the oils of Lonchocarpus sericeus and Lonchocarpus cyanescens

Proximate composition of the seeds and chemical analysis of the oils of Lonchocarpus sericeus and Lonchocarpus cyanescens were determined. The oil content of the seed of L. cyanescens is 29.71?±?0.20% while that of L. sericeus is 28.00?±?0.50%. The seeds as well as the oils of L. cyanescens and L. sericeus were found to be rich in K, Na and Fe. Linolenic (C18:3) and oleic (C18:1) acid are the dominant fatty acids while the neutral lipids the dominant lipid class in the oils. Phytol, sterols, beta-tocopherol and hydrocarbons were identified in the unsaponifiable matters of the oils using GC-MS. The HPLC results revealed the presence of glycolipids, which are monogalactosyldiacylglycerol, digalactosyldiacylglycerol, digalactosylmonoacylglycerol and monogalactosylmonoacylglycerol. Molecular speciation of the triacylglycerol revealed the presence of molecular species with equivalent carbon chain numbers C(36) (L. sericeus) and C(50) (L. cyanescens) to be dominantly present in the oils.     

Determination of isotopic composition of boron

Investigations were carried out on the determination of isotopic composition of boron using Cs₂BO ₂ ⁺ ion and thermal ionisation mass spectrometry. The results show distinct advantage over the normally used Na₂BO ₂ ⁺ ion.     

Determination of triacylglycerol regioisomers using electrospray ionization-quadrupole ion trap mass spectrometry with a kinetic method

The kinetic method was applied to differentiate and quantify mixtures of regioisomeric triacylglycerols (TAGs) by generating and mass selecting alkali ion bound metal dimeric clusters with a TAG chosen as reference (ref) and examining their competitive dissociations in a quadrupole ion trap mass spectrometer. This methodology readily distinguished pairs of regioisomers (AAB/ABA) such as LLO/LOL, OOP/OPO and SSP/SPS and consequently distinguished sn-1/sn-3, sn-2 substituents on the glycerol backbone. The dimeric complex ions [ref, Li, TAG_{(AAB and/or ABA)}]⁺ generated by electrospray ionization mass spectrometry were subjected to collision induced dissociation causing competitive loss of either the neutral TAG reference (ref) leading to [Li(AAB and/or ABA)]⁺ or the neutral TAG molecule (TAG_{(AAB and/or ABA)}) leading to [ref, Li]⁺. The ratio of the two competitive dissociation rates, defined by the product ion branching ratio (R_iso), was related via the kinetic method to the regioisomeric composition of the investigated TAG mixture. In this work, a linear correlation was established between composition of the mixture of each TAG regioisomer and the logarithm of the branching ratio for competitive fragmentation. Depending on the availability of at least one TAG regioisomer as standard, the kinetic method and the standard additions method led to the quantitative analysis of natural TAG mixtures.     

Characterization of triacylglycerol and diacylglycerol composition of plant oils using high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

Triacylglycerols (TGs) and diacylglycerols (DGs) in 16 plant oil samples (hazelnut, pistachio, poppy-seed, almond, palm, Brazil-nut, rapeseed, macadamia, soyabean, sunflower, linseed, Dracocephalum moldavica, evening primrose, corn, amaranth, Silybum arianum) were analyzed by HPLC-MS with atmospheric pressure chemical ionization (APCI) and UV detection at 205 nm on two Nova-Pak C18 chromatographic columns connected in series. A single chromatographic column and non-aqueous ethanol-acetonitrile gradient system was used as a compromise between the analysis time and the resolution for the characterization of TG composition of five plant oils. APCI mass spectra were applied for the identification of all TGs and other acylglycerols. The isobaric positional isomers can be distinguished on the basis of different relative abundances of the fragment ions formed by preferred losses of the fatty acid from sn-1(3) positions compared to the sn-2 position. Excellent chromatographic resolution and broad retention window together with APCI mass spectra enabled positive identification of TGs containing fatty acids with odd numbers of carbon atoms such as margaric (C17:0) and heptadecanoic (C17:1) acids. The general fragmentation patterns of TGs in both APCI and electrospray ionization mass spectra were proposed on the basis of MSn spectra measured with an ion trap analyzer. The relative concentrations of particular TGs in the analyzed plant oils were estimated on the basis of relative peak areas measured with UV detection at 205 nm.     

Determination of phytoplankton composition using absorption spectra

Characterisation of phytoplankton communities in aquatic ecosystems is a costly task in terms of time, material and human resources. The general objective of this paper is not to replace microscopic counts but to complement them, by fine-tuning a technique using absorption spectra measurements that reduces the above-mentioned costs. Therefore, the objective proposed in this paper is to assess the possibility of achieving a qualitative determination of phytoplankton communities by classes, and also a quantitative estimation of the number of phytoplankton cells within each of these classes, using spectrophotometric determination.Samples were taken in three areas of the Spanish Mediterranean coast. These areas correspond to estuary systems that are influenced by both continental waters and Mediterranean Sea waters. 139 Samples were taken in 7-8 stations per area, at different depths in each station. In each sample, the absorption spectrum and the phytoplankton classes (Bacyllariophyceae (diatoms), Cryptophyceae, Clorophyceae, Chrysophyceae, Prasynophyceae, Prymnesophyceae, Euglenophyceae, Cyanophyceae, Dynophyceae and the Synechococcus sp.) were determined.Data were analysed by means of the Partial Least Squares (PLS) multivariate statistical technique. The absorbances obtained between 400 and 750 nm were used as the independent variable and the cell/l of each phytoplankton class was used as the dependent variable, thereby obtaining models which relate the absorbance of the sample extract to the phytoplankton present in it. Good results were obtained for diatoms (Bacillarophyceae), Chlorophyceae and Cryptophyceae.     

Determination of copolymer composition by Raman spectroscopy

The application of laser-Raman spectroscopy to the analysis of copolymers of glycidyl methacrylate (GMA) with methyl methacrylate (MMA) and styrene is discussed. For both copolymer systems the line near 1451 cm^?1, assigned to the methylene bending mode, was found to be a useful reference. Lines characteristic of each monomer were identified. The intensities of these lines were found to be linearly related to the composition of the copolymers when normalized against the 1451 cm^?1 reference. The line near 1730 cm^?1, assigned to the carbonyl stretching mode, was also found to be a useful reference for the copolymers of methyl methacrylate and glycidyl methacrylate.     

Determination of the triglyceride composition of certain fats

Conclusions Enzymatic hydrolysis, together with Coleman's method of calculation, as modified by us has been used to determine the glyceride composition of oils. It has been established that almost all (93–96%) of the -positions of the glycerides of the coils studied are occupied by radicals of unsaturated acids.Khimiya Prirodnykh Soedinenii, Vol. 5, No. 2, pp. 76–79, 1969     

Study of the influence of triacylglycerol composition on DSC cooling curves of extra virgin olive oil by chemometric data processing

In this work, a coupled high-pressure liquid chromatography-differential scanning calorimetry-partial least square (HPLC–DSC–PLS) procedure was applied to clarify the influence of triacylglycerol composition on the shape of cooling curves for extra virgin olive oil (EVOo), as chemometric processing of digitized DSC curves was previously reported to be an attractive alternative to the application of the common procedure of parameter extrapolation for the analysis of thermal transition. 69 samples of EVOo were analysed to obtain triacylglycerol (TAG) composition by means of HPLC and DSC cooling profiles. Results obtained by the application of PLS algorithm on TAG concentration (%) and digitized DSC curves showed that cooling transitions were markedly influenced by OOO, OLO and OOP + SLO that are the most representative TAG for EVOo. Other TAG as LLP + OLnO, LLL + LLPo and POPo developed good PLS models, appearing to influence EVOo cooling curve, although less markedly than the further. Otherwise, the other identified TAG did not render appropriate models. Finally, grouping TAG according to different unsaturation degree, high correlation coefficients (>0.80) and low relative standard deviations (<11 %) were found for sum of tri-unsaturated triacylglycerols in both calibration and validation sets. Starting from these encouraging results, this new and fast coupled approach may be applied to a wider set of EVOo samples to tentatively discriminate among oils according to different geographical and/or botanical origins taking into account relation established among TAG and cooling curves.     

Determination of chemical composition distributions in synthetic polymers

A characteristic feature of synthetic polymers is their dispersity in molar mass and, in many cases, chemical composition. Since dispersity is highly relevant in relation to polymer properties, ongoing efforts are being put in the development of appropriate analysis methods. In this respect, size-exclusion chromatography (SEC) is well known for the determination of molar mass distributions. Methods for chemical composition distributions are less mature than SEC and mainly include liquid chromatography and mass spectrometry and the combination of these techniques. The term chemical composition distribution is considered broad in this paper, i.e. for the chemical composition distribution of a (co)polymer backbone, for the functionality type distribution of a polymers' functional end groups, for the block length distribution of a block copolymer, for the branching distribution and for the tacticity distribution. In this paper, analysis methods for all types of chemical composition distributions are reviewed. Special attention is paid to practical requirements and common misconceptions that sometimes arise. Applications within the last 5 years are summarized.     

Determination of the triglyceride composition of grapes by HPLC

Summary The triglyceride composition of the Tempranillo grape (Vitis vinifera) has been examined by a combination of HPLC and GLC. To identify the triglycerides, equations were applied relating log k′ with the molecular variables: equivalent carbon number, chain length and number of double bonds in each of the fatty acids in the glycerides. Ten triglycerides were found, the principal ones being trilinolein (35.75%), dilinoleyl-olein (21.03%) and dilinoleyl-palmitin (17.02%).     

Determination of elemental composition of aluminosilicate clays by EDXRF

Aluminosilicate clay samples were analyzed for the constituent elements with respect to a certified reference material using microcrystalline cellulose powder as a binder for presentation as a pressed pellet to an energy dispersive X-ray fluorescence spectrometer. Sample preparation for presentation is highlighted. The data manipulation to achieve the analytical accuracy from the inherent precision is discussed.     

Heat capacity of cheese

The heat capacity of several samples of hard cheese, semi-hard cheese and soft cheese was determined by conventional differential scanning calorimetry (DSC) and by temperature modulated DSC. Additionally, the gross composition of the cheeses was analysed, and equations from the literature were used to calculate the heat capacity therefrom. Both analytical methods were suitable to determine the heat capacity of the cheese samples whereas only one out of three equations proposed for the calculation of the heat capacity of foods from composition data led to results which were comparable with analytical data. As the equation coefficients for particular constituents are responsible for the deviations in the calculated heat capacities the differences between calculated and measured values increase with a decreasing moisture content of the cheeses.