Lipid, analysis composition

Low-wavelength UV detection (200-210 nm) is more sensitive and permits the use of gradients but precludes the use of certain common lipid solvents, such as chloroform and acetone, which are opaque in the UV region of interest. With low-wavelength UV detection, the response will also be somewhat dependent on fatty acid composition. For these reasons the mobile phases used in lipid analysis by HPLC may seem rather strange to workers familiar with the Thin Layer Chromatography (TLC) or open column separations. 

NU Olsson, AJ Harding, C Harper, N Salem Jr. High performance liquid chromatography method with light scattering detection for measurements of lipid class composition analysis of brains from alcoholics. J Chromatogr B 681 213—218, 1996. 

Advanced analytical techniques, particularly mass spectrometry (MS), often combined with liquid chromatography (LC) or gas chromatography (GC), are requisite for lipid analysis and they have played the crucial role in the emergence as well as the progresses of lipidomics. MS is the principal choice for the lipid analysis, particularly using electrospray ionization (ESI) and sometimes also atmospheric pressure chemical ionization or laser-based MS methods for surface analysis. The MS-based techniques are the best choice for lipidomics due to their superior sensitivity and molecular specificity, and because they provide the ability to resolve the extensive compositional and structural diversity of lipids in biological systems. 

Table n shows the changes in the composition of the bacterial substance which occur when 100 mg. of log cells at the depletion point grow into valine cells (if that is the limiting amino acid), or into threonine cells if threonine is limited. The amounts formed from 100 mg. at the point of depletion average 145 mg. in the case of valine and 190 mg. in the case of threonine. The determination of wall substance by mechanical disruption and the determination of membrane substance by lipide analysis have been outlined. The other data are obtained by way of conventional procedures DNA (deoxyribonucleic acid) by diphenylamine, and completely independently by thymine RNA (ribonucleic acid) by ultraviolet extinction and cytoplasmic protein from nitrogen determinations corrected for the nitrogen content of the other components. 

Lipid analysis is typically performed either by incorporating a nonexchangeable radiolabel marker, such as (14C) or (3H) cholesteryl hexadecyl ether (CHE), into the vesicle membrane, or by analyzing the phosphate content and extrapolating the result according to the original composition of the vesicles. Both approaches assume that the label concentration and vesicle composition do not change on vesicle preparation or subsequent manipulation. The phosphate assay is carried out as follows ... 

There is considerable interest in lipid analysis and it is expected that this interest will increase in the future since an increasing number of diseases is recognized to be accompanied by alterations of lipid compositions. Although not yet commonly accepted, MALDI-TOF MS represents a reliable method of lipid analysis. In our opinion, MALDI-TOF MS is a very suitable method because measurements can be performed in a relatively short time and a very convenient... 

Table 1.3 summarizes recent and important oceanographic and limnological work based on the analysis of lipid class composition by TLC-FID. A notable characteristic of this compilation of studies is the broad spectrum of matrices analysed, from lipids in environmental samples of water, sediments, soils and micro-organisms to vertebrates. 

Oshima, T. and Ackman, R. G. (1991) New developments in Chromarod/Iatroscan TLC-FID analysis of lipid class composition. Journal of Planar Chromatography, 4, 27-34. 

Regarding detection limits, both approaches [30,33] provided comparable results (about 400 pmol) and, therefore, both methods might be useful for routine lipid analysis—at least when major changes of the lipid compositions are expected. 

Ohshima, T Ackman, R.G. New developments in chromarod/iatroscan TLC-FID Analysis of lipid class composition. J. Planar Chromatogr. 1991, 4, 27—34. 

Sommer et al. [72] used reversed-phase LC-MS or LC-MS/MS with a C18 capillary column to fully characterize the individual lipid species including fatty acid compositions after fractionation of different lipid classes utilizing normal-phase LC-MS on an offline setting. Similar approaches using 2D LC-MS online or offline were also used by Byrdwell for a total lipid analysis [73] as well as for others [74—77]. 

The majority of CL methods in lipid analysis concern lipid extracts and not untreated lipids, because lipids are not miscible with water. However, any treatment of lipids prior to analysis, such as extraction, changes the chemical composition of the tested sample, which might lead to erroneous results. For this reason, the direct analysis of samples without any treatment would be preferable (Gokmen et al., 2009). 

Although the formation of complexes between silver ions and unsaturated compounds had been known since before 1939, the application of this property in lipid analysis was not reported until the early 1960s . Since that time, however, silver has been applied widely to improve the resolving power of TLC and column chromatography, and has provided the literature with extensive data on lipid isomer composition. 

Liden, K., Takahasi, C. and Nelson, D.E. 1995 The effects of lipids in stable carbon isotope analysis and the effects of NaOH treatment on the composition of extracted bone collagen. Journal ofArchaeological Science 22 321-326. 

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