Sherazi S T H, Mahesar S A, Bhanger M I, van de Voort F R, Sedman J
National Center of Excellence in Analytical Chemistry, University of Sindh, Jamshoro, Pakistan. tufail_sherazi@ yahoo.com
J Agric Food Chem. 2007 Jun 27;55(13):4928-32. doi: 10.1021/jf063554f. Epub 2007 May 26.
A simple, rapid, and reproducible method has been developed for the quantitative determination of free fatty acid (FFA) content in lipids extracted from poultry feeds by Fourier transform infrared (FTIR) spectroscopy with the use of a single-bounce attenuated total reflectance (SB-ATR) accessory. An FTIR calibration curve was prepared by gravimetrically adding oleic acid (15-37%) to pure refined, bleached, and deodorized (RBD) canola oil and measuring the area of the COOH absorption band at 1710 cm-1. The oil from each of 12 poultry feed formulations was extracted using conventional Soxhlet extraction, and after evaporation of the solvent, the FFA content was determined by the conventional AOCS titrimetric procedure and by the SB-ATR/FTIR method. The SB-ATR/FTIR FFA predictions were related to those determined by the AOCS titrimetric method by linear regression, producing an R value of 0.999 and a SD of +/-0.28% FFA. Time-course spectra collected as lipids extracted into hexane indicated that a 15 min extraction was adequate to obtain a representative sample for FFA determination, with further extraction resulting in little, if any, change in the proportion of FFA in the lipid extract. Only a small volume of the hexane extract ( approximately 20 mL) yielded sufficient material for the SB-ATR/FTIR analysis. Thus, by shortening the extraction time and taking a small sample so as to reduce solvent removal time, the SB-ATR/FTIR procedure provides a very simple and rapid means of determining the FFA content of poultry feed lipids.
已开发出一种简单、快速且可重复的方法，用于通过傅里叶变换红外（FTIR）光谱法，使用单次反射衰减全反射（SB-ATR）附件，定量测定从家禽饲料中提取的脂质中的游离脂肪酸（FFA）含量。通过将油酸（15 - 37%）重量法添加到纯精制、漂白和脱臭（RBD）菜籽油中，并测量1710 cm-1处COOH吸收带的面积，制备了FTIR校准曲线。使用传统索氏提取法从12种家禽饲料配方中的每一种提取油，溶剂蒸发后，通过传统的美国油脂化学家协会（AOCS）滴定法和SB-ATR/FTIR法测定FFA含量。通过线性回归将SB-ATR/FTIR对FFA的预测值与AOCS滴定法测定的值相关联，得到的R值为0.999，FFA的标准偏差为±0.28%。当脂质提取到己烷中时收集的时间进程光谱表明，15分钟的提取足以获得用于FFA测定的代表性样品，进一步提取导致脂质提取物中FFA比例几乎没有变化（如果有变化的话）。仅少量己烷提取物（约20 mL）就产生了足以进行SB-ATR/FTIR分析的材料。因此，通过缩短提取时间并取少量样品以减少溶剂去除时间，SB-ATR/FTIR方法提供了一种非常简单快速的测定家禽饲料脂质中FFA含量的方法。
