食品科學(xué)與工程外文翻譯--高效液相色譜-電化學(xué)檢測(cè)法在檢測(cè)油脂中高級(jí)脂肪酸的應(yīng)用（英文）

1、Journal of Chromatography A, 764 (1997) 177–182Determination of higher fatty acids in oils by high-performance liquid chromatography with electrochemical detection* T. Fuse, F. Kusu, K. TakamuraSchool of Pharmacy, Tokyo

2、University of Pharmacy and Life Science 1432-1, Horinouchi, Hachioji, Tokyo 192-03, JapanReceived 15 April 1996; revised 15 August 1996; accepted 22 October 1996AbstractA system of high-performance liquid chromatography

3、with electrochemical detection was developed for the separation and determination of higher fatty acids. An octadecylsilica (ODS) column was used as the stationary phase and an ethanol– acetonitrile (10:90) mixture as th

4、e mobile phase. The eluate was mixed with a quinone solution which was composed of 6 mM 2-methyl-1,4-naphthoquinone and 76 mM LiClO in ethanol–acetonitrile (10:90) through a mixing coil. Peak height for 4 higher fatty ac

5、ids measured at 2415 mV vs. saturated calomel electrode (SCE) was linear against the amount of acid between 20 and 1200 pmol. Free fatty acids in various oil samples were determined by this method, which was found not on

6、ly sensitive and reproducible but also a simple means for separating and determining free fatty acids in oils.Keywords: Electrochemical detection; Fatty acids1. Introduction phore prior the column separation is required

7、for sensitive detection in HPLC. Many derivatizing Many attempts have been made for the separation (labelling) reagents have been developed for this and determination of fatty acids by gas chromatog- purpose [4–13]. A ca

8、talyst in some cases is required raphy (GC) [1–3] and high-performance liquid chro- for complete derivatization owing to the poor reac- matography (HPLC) [4–13]. In current GC analysis tivity of carboxyl groups [4]. For

9、the derivatization commonly employed today, free fatty acids are of fatty acids with such reagents, the amount of generally converted to their methyl esters and then reagent, reaction temperature and time are critical fo

10、r injected into a capillary GC. Methylation and GC high reaction efficiency and avoiding any side prod- conditions, such as programmed-temperature, split- uct formation. Water is often an incompatible en- injection, as w

11、ell as type of capillary column, carrier vironment for derivatization reactions and to find a gas, and detector, are all important determinants of solution to this problem, examination was made of high accuracy and preci

12、sion. The main advantage of the use of aqueous micellar systems for derivatiza- HPLC with fluorescent detection (HPLC-FL) of fatty tion [5]. Although fluorimetric detection is quite acids is high sensitivity. However, ow

13、ing to the weak sensitive, fluorescent intensity is liable to vary owing absorption and fluorescent properties of fatty acids, to the presence of substances in complicated samples derivatization with a strong chromophore

14、 or fluoro- unless there is a clean-up procedure for their elimina- tion. It is thus highly desirable to develop a simple *Corresponding author. and rapid method that requires no such procedure.0021-9673/97/$17.00 Copyri

15、ght ? 1997 Elsevier Science B. V . All rights reserved PII S0021-9673(96)00906-5T. Fuse et al. / J. Chromatogr. A 764 (1997) 177–182 1793. Results and discussion that applied potential that would give the reduction curre

16、nt of protonated quinone. The reduction potential of protonated quinone was 3.1. Voltammetric reduction of VK in the presence less negative than that of dissolved oxygen. The 3 of fatty acids half-peak potential of the f

17、irst reduction wave of oxygen in ethanol containing 38 mM LiClO was 4 Protonation of quinone at the electrode surface 2730 mV vs. SCE. However, there may have been occurs prior to its electron transfer. Protonated backgr

18、ound current due to the dissolved oxygen, quinone is reduced at a potential less negative than since the oxygen was reduced at potentials more that of quinone to give a new peak on the volt- negative than 2300 mV vs. SCE

19、. ammogram of quinone [17,18]. Higher fatty acids, such as palmitic acid, in an ethanol solution con- 3.2. HPLC-ECD taining VK and LiClO were previously found to 3 4 give rise to a peak of protonated VK on the In conside

20、ration of the above, HPLC-ECD of fatty 3 voltammogram of VK at a potential less negative acids was carried out. Reversed-phase separation of 3 than the reduction potential of VK ; VK itself gave higher fatty acids was do

21、ne using an ODS column 3 3 a clear reduction peak at 2720 mV vs. SCE, and a and a MP of an ethanol–acetonitrile mixture. The peak of protonated VK was noted at 2320 mV vs. dissolved oxygen in MP and the quinone solution

22、3 SCE after adding palmitic acid to the solution. The was removed by the degassor. A 20 ml aliquot of peak height was proportional to added acid con- solution containing fatty acids was injected into the centration [16].

23、 column; the eluate was mixed with the quinone The half-peak potential of a peak of protonated solution and the fatty acids was detected with ECD. VK was previously shown to shift to a more Examination was made of how th

24、e ratio of acetoni- 3 negative potential accompanied by an increase in pK trile to ethanol in the MP influenced the separation a of the added acid [17]. However, half-peak potentials and sensitivity for acid determinatio

25、n. In Fig. 2, the of prepeaks for different higher fatty acids were retention time (A) and the peak heights (B) of signals essentially the same, since acid strength was nearly for 200 pmol linoleic, oleic, palmitic and s

26、tearic acid the same. Each fatty acid could thus be detected at were plotted against the ratio of the two solvents, inFig. 2. Retention time (A) and peak height (B) as functions of solvent ratio of the mobile phase. (a)

27、Linoleic acid, (b) oleic acid, (c) palmitic acid, (d) stearic acid. Amount of acid5200 pmol. HPLC conditions: quinone solution, 6 mM VK 176 mM LiClO in ethanol–acetonitrile 3 4 mixture; sample volume, 20 ml; column, LiCh