Wyniki wyszukiwania - BazTech

Ograniczanie wyników

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: witaminy rozpuszczalne w tłuszczach

Sortuj według:

Ogranicz wyniki do:

Thermodynamic parameters of the reversed-phase liquid chromatography retention for some lipid-soluble vitamins

David V., Bala C., Rotariu L.

Chemia Analityczna

2004

Vol. 49, No. 2

191-199

The enthalpy and entropy changes of retention some lipid-soluble vitamins (A, D3 and E) have been estimated by means of the high performance liquid chromatography. Retention was studied using an octadecyl-silica modified stationary phase and different mobile phases containing methanol as the main organic solvent. For each vitamin the linear dependence of the logarithm of capacity factor on the reciprocal of the absolute temperature served for the calculation of the enthalpy contribution of the reversed-phase retention process (ranging between -7 and -14.2 kJ mol-1) and the entropy change (between -18.9 and -37.3 J mol-1 K-1). The results were in agreement with those obtained for other compounds and similar stationary phases.

Za pomocą wysokosprawnej chromatografii cieczowej wyznaczono zmiany entaipii [entropii retencji witamin rozpuszczalnych w tłuszczach (A, Dv E). Retencję badano używając jako fazy stacjonarnej żelu krzmionkowego modyfikowanego oktadecylcm oraz faz ruchomych, których głównym składnikiem był metanol. Do obliczeń wykorzystano liniową zależność logarytmu współczynnika retencji poszczególnych witamin w odwróconym układzie faz od odwrotności temperatury bezwzględnej. Zmiana entalpii mieściła się w zakresie od -7 do-14.2 kJ mol(-1)1 a zmiana entropii w zakresie od-18.9 do-37.3 J mol(-1)1 K(-1). Wartości te były zgodne z wartościami otrzymanymi dla innych związków i podobnych faz stacjonarnych.

Wykorzystanie HPLC do oznaczania witamin rozpuszczalnych w tłuszczach

Wieliński S., Olszanowski A.

Wiadomości Chemiczne

2001

[Z] 55, 11-12

1075-1102

In this review, selected chemical techniques such as TLC, UV-VIS, GC, HPLC and microbiological procedures (published since 1960) used for simultaneous determination of fat-soluble vitamins in different matrices have been discussed. Particular attention has been given to HPLC methods, not only in terms of chromatographic conditions, but also in comparison with other separation techniques. HPLC methods have been shown to have clear advantages over existing chemical or microbiological assays in terms of sensitivity, specificity and sample throughput for the analysis of these vitamins. In order to assist the analyst in the selection of a particular procedure, certain chromatographic conditions have been listed for this purpose. However, as currently, no specific HPLC procedures can be recommended, it was decided to develop new methods for these vitamins. Within the past 30 years, HPLC has become the predominant method for separation and quantification of fat-soluble vitamins. The two major, distinct methods of HPLC separation are referred to as normal-phase chromatography and reverse-phase chromatography. To generalise, reverse-phase HPLC is frequently preferred for analysis of biological samples as the columns are more easily purged of any contaminants and sample separation is usually less sensitive to slight changes in mobile-phase composition. A summary of HPLC systems used for fat-soluble vitamins analysis is provided in Table 1 [60-106] and 2 [107-152] in format: compounds determined, matrix, sample preparation and clean up, column, mobile phase, detection, time of analysis, reference. Finally, this paper describes a procedure for the simultaneous determination of vitamin A (retinol acetate, palmitate), vitamin D3 (cholecalciferol), vitamin E (alpha-tocopherol acetate) and alphacalcidol in capsules from a single sample extract using reverse phase HPLC and column backflushing techniques [162-165]. The procedure eliminates saponification, lengthy extractions and sample workup. It is specific to the compounds of interest, shows very good internal precision and is free of interference compared to current published methods.