使用液体细胞对极低浓度反式脂肪酸的快速FTIR定量分析

指南中描述的反式脂酸定量方法使用GC（AOCS Ce1h-05或AOAC996.06），或者具有与该方法相同性能的其他方法。使用GC的分析不仅需要在测量前进行大量的样品制备，包括使用BF3去除甲基化脂肪，而且还需要1小时以上的分离时间。本报告描述了使用FTIR透射法将反式脂肪酸定量分析至1.0%以下的水平，证明了与GC方法等效的结果，并且可以在极短的时间内获得。实验：用5个标准水平的三赖氨素创建校准曲线，通过将三赖氨酸（应用中图1中的绿色光谱）（反式三醛的异构体）添加到仅含有顺式的顺式三醛（应用中图1的橙色光谱）中制备。本应用中结果表明，使用FTIR透射测量可以实现0.05-1.0%反式脂肪酸的定量分析。该方法具有样品制备少或不制备的明显优点，与GC方法相比速度快得多。然而，细胞必须在两次测量之间清洗，这使得它比ATR方法稍微不方便。因此，我们建议使用ATR方法测量1%的LOQ，使用透射方法测量1.0%以下的LOQ。Application Note Rapid FTIR Quantitative Analysis of Trans-Fatty Acid atExtremely Low Concentrations using a Liquid Cell2/3Application Note 050-Q U -0232 Rapid FTIR Quantitative Analysis of Trans-Fatty Acid at Extremely Low Concentrations using a Liquid Cel l Intro d uc t ion Trans-f atty ac i ds in food are becoming a major concern due to their det ri menta l affects o n human h ealth. A method for the rapid quant i tative analysis usi n g FTIR with temperature controlled ATR has been suggested2) and an off i cial method using FTIR has been proposed by both the AOAC (American Organization of Analytical Chemists) and AOCS (American Oil Chemists' Society) due to its extremely short ana l ysis time， within 1-2 minutes， which is much shorter than that requi r ed by a GC method (Gas Ch r omatography， FT/IR-4000 and 6000 Series Spectrometers wh i c h also requi r es extensive sample preparation). The offici a l method described by the AOCS， suggest tha t the l i m it of quan t itation (LOQ) using t h e ATR method i s around 1.0%2)， this was also demonstrated in ou r FTIR Application data') under the same experimental condi t ions specif i ed by the AOCS. According to“The Gu i deline for Disclosure of Information on Trans-fa t ty acid Content" issued by the Consumer Affairs Agency of Japan，“Zero ” may be shown o n the labeling if the measured content of trans-fatty acid i n food is less than 0.3% w/w or 0.3% w/v (for beverages). I n ot h e r words， 0.3% i s the required limit of quan ti tation (LOQ). Similar requirements are found i n other countries (USA： <0.5 g/meal， Taiwan：<0.3 g / 100 g， Korea o r South America： <0.2 g/meal) and accordingly， a rapid and p recise method i s required for t he quantitat i ve ana l ysis of trans-fatty acid content in food to l imits below 1.0%. The method fo r quantitatio n of trans-fatty acid desc ri bed in t he Gu i deline uses GC (AOCS Ce1h -05or AOAC996.06)， or other methods that have the equi v alent performa n ce to th i s method. The analysis using GC not only requ i res extensive sample prepa r atio n before measurement， includ in g remova l of methylated fat using BF， but also requires more than 1 h our f or the separation. This repo r t desc ri bes the quantitative analysis of trans-fatty acids to levels be l ow 1.0% using an FTIR transmission met h od， demonstrating an eq ui valent r esu l t to the GC method and can be obtained in an ext r eme l y shor t time. Exper i men t al T h e t rans-fatty acid peak at 966 cm is us e d for t h e qua n ti t ative analysis (Fig. 1). This i s also ado p ted i n the of f ic i a l method s ， suc h as t he ATR method). A calibra t i o n curve was crea t ed with 5 standard leve l s of t rielaidi n ， whic h were prepared by addi n g trielaidi n (green color spect r um in Fig . 1)， a n i so m e r of t rans-tr iolei n ， to cis-tr iolein (orange color spectr u m in Fig. 1) which contains only cis-type. Figure 1. I R s p e ct r um o f c is-f a t s and t rans -fats (ATR) Instrument FT/IR-4100 Detector DLaTGS Resolution 4cm Accumulation 64 times Apodization Triangle Temperature 25℃ (ambient temperature) Mode Transmission (method of solution) Cell Sealed liquid cell *NaCl (thickness ： 0.1mm) Standard Sample Triolein， Trielaidin (0.05， 0.1，0.2，0.5，1.0%) Peak Calculation Area 945-990cm1 JASCO INC. 28600 Mary's Cour t ， E a s to n ， M D 21601US A T el ： (800) 333-5272， Fa x ： (410) 822-7526 A ppl ic a tio n Lib r ary： ja s c o i n c.com /appli c a t i o ns R esu l t and D iscussion Transmissio n spectra of 5 standa r d l evels of t r iela i din (0.05，0.1，0.2，0.5，1.0%) are d i splayed in F i g. 3. The correlation coeffic i ent (0.9998) for the calibration curve sh o ws a good li near i ty for the t rans-fatty acid concent r ation us i ng t he peak he i g h t or area around 966 cm1(Fig. 4). Since the S/N (Peak-to-Peak) for the stand a rd level at 0.05% is abou t 15：1， which i s much bette r th an t h e r equi r ed 10：1 normally accepted as t h e l i mit o f quantitation (LOQ) (Fig. 5)， th is method is conside r ed se n si t i ve enough for t h e quant i tat i ve analysis of samples wit h l ow concentrat i ons， down to 0.05%. Figure 2. Se a l e d liq ui d c ell Figure 3. Tran s -fats p e ak at 966 cm The above result i ndicates t h at t h e quantitat i ve analysis of 0.05 - 1.0% trans-fatty acid can be achieved usi n g FT I R t r ansmi s sion measureme n t. This method has t he distinct advantages of litt l e or no sample preparation and is much f aster compared wi t h the GC method. However， the cell h as to be washed between measurements， making it a little less convenient than the ATR method. Therefore， we recommend that the ATR method i s used for measurement to LOQs of 1%and the transmission method is used for sample measurement to LOQs below 1.0%. Figure 4. Cali b ra t ion c ur v e Figure 5. Spe ctr u m o f t rans -fats of 0.05% 1) JASCO F T /IR Appl i cat i o n data 050-AT-0215(2010) 2) AOAC Of fi cial Me t ho d 2000.10， AOCS O f ficial Me t hod Cd 14d-99 28600 Mary's Cour t ， E a s to n ， M D 21601US A A ppl ic a tio n Lib r ary： ja s c o i n c.com /appli c a t i o ns