脂肪中碘值的FT-NIR测定

碘值（IV）用作脂肪不饱和度的指标，用于评估脂肪油和生物柴油的性质。碘值通常使用如ASTM D5554、JIS等标准方法中所述的基于氧化还原反应的湿化学方法来测量。然而，这种方法相当复杂。已经提出了一种使用振动光谱（IR和拉曼）来估计碘值或不饱和度的更简单的方法（参见050TR0125 FT/IR应用数据）。本申请说明旨在与传统的湿化学方法相比，使用专用的FT-NIR（傅立叶变换近红外光谱仪）评估碘值的测量精度。FT近红外光谱仪配备了风冷Peltier恒温样品池支架，以确保样品在液相中进行测量。根据用该系统测量的脂肪油的近红外光谱，使用partial least squares PLS 方法计算校准曲线，将该数据与使用传统湿法获得的碘值进行比较。校准曲线数据用于通过将其应用于实际样品来显示系统的有效性。试验：首先，测量了24种不同碘值的脂肪油（一式两份），并使用近红外光谱计算校准曲线模型。接下来，将使用PLS方法生成的校准曲线模型应用于测量的光谱，并将计算的碘值与湿化学方法相关联。最后，利用该校准曲线模型测量了5个实际样品的碘值。结论：结果表明，具有高波数精度的FT-NIR光谱仪，配有Peltier恒温池支架来控制样品温度，对于碘值的测量非常有效。它提供了与湿化学方法相当的数据质量，但更方便，更简单、更快、无损。Application Note050TR0203-E FT-NIR Measurementof the lodine Value in Fat2/3Application Note FT-NIR Measurement of the lodine Value in Fat In t rod uc tion T h e lodine Value (IV) is used as an i n dex for t h e degree of unsaturat i on in fats， and is used for evaluating the n atu r e of fatty oils and bio-d i esels.T h e i od i ne value is typical l y measured usi n g a wet chemistry method as described in the standard methods of ASTM D5554， JIS etc.， which i s based on a r edox r eaction. However， this method is quite complicated . A simpler method us i ng vibrational spectroscopy (IR and Raman) for t he estimat i on of t h e lodine value o r degree of unsaturat i on has been proposed (r efer to 050TR0125 FT/I R Application Data). This applicat i on note has been developed to evaluate the meas u rement accuracy of the iod i ne value u sing a dedicated FT-NIR (Fourier Transform Near I n frared Spectrometer)，compared to the traditional wet chem i stry method . The FT-NIR spectromete r was fitted with an air-cooled Peltier t hermostated sample cell holder to ensu r e the samples we r e measured in liqu i d phase. Figure 1. F T-NIR s ystem wi t h t h er m o s ta te d cel l h o l d er f or lod in e v a l ue (I V) me a s ur e ment A calibrat i on curve wa s calculated using the partial least squares PLS method from NIR spectra of fatty oils measured with the system， th i s data was compared to the lodine values obtained using a conven t ional wet method. The cal i bration curve data was used to show the effectiveness of the system by applying it to actual samples. Keyword s E x perimen t al F i rst l y， 24 d i ffere n t fatty oils with various lodine values we r e measured (in duplicate) and the NIR spect r a u sed to calculate a cal i bration curve model. Next， the calibration curve model generated u sing the PLS method was applied to measured spectra and the calcu l ated lod i ne values were correlated with the wet chemistry method . Fi n ally， the lodine values of 5actual samples we r e measured utilizing this calibration curve model . Light Source High-Intensity Ceramic Source Temperature Control EHC-716 Air-cooled Peltier(customized) Detector DLATGS Temperature Setting 60°℃(samples were solid at room temperatureand temperature was set at higher than the melting point) Accumulations 16 Photometric Mode Transmittance Resolution 8cm- Cell Quartz Cell， 5 mm pathlength Results and D iscussion F igure 2 s h ows the NIR spect r a of 24 fatty oils， from t his d a ta a cali b ration curve m odel was generated using a PLS met h od i n the wavenumber range 4500 to 4800 cm. Figur e 3 shows the PLS cali b ration c u rv e mod e l which giv e s good corr e lation betwe e n th e ‘t r u e'val u e (o b ta in ed b y wet ch e mical m ethod) and e valua t ed valu e (obtai ne d b y s p ec t ra l an a lysis). Th e correl a t i on co e ff i c ien t is 0.9995. The r e sults of evaluat in g the quant i tation r e producibi lit y (n =30) of 5 diffe r e n t f at t y oi l s with d if ferent lodi n e values usi n g th i s m odel are shown i n Ta b le 1. The average value and t h e sta n da r d d eviat i o n obtained f rom the spectra are presented in the table. Th e val u es i n par e n th es e s are l odi ne values obtained by wet analysis method . Figure 2. N I R s p e ct r a o f 24 di f fe r e n t f a tty o il s Figure 3. P L S ca li b r at ion c u rv e model 28600 Mary's C o ur t ， E asto n， MD 21601US A T el ： (800) 333-5272 F ax： (410) 822-7526A ppl ic a tio n Lib r ary： ja s c o i n c.com /appli c a t i o ns The error betwee n the results o b tained wit h the two a n alysis methods is less than 2% and the standard deviation of t h e reproducibi l i ty i s less than 0.173， which can be co n sidered as a excel l ent r esult. Th e r e sults demonstrate th at th e an FT -NIR spect r omet e r with h igh wav e num be r accuracy， fitted wi t h a Pelt i e r thermostated cel l hold e r to control t h e sample temperatu r e i s ve r y effec t ive for m easurement of th e iodine value. It provides com p a r able data quality to t h e we t chem i stry method， b ut is muc h more convenient ， be in g simpler ， faster and nondestr u ctiv e . Table 1. Res u lts an d co m p a ri s o n o f ac t u al sa mple s Sample A(102.6) B(115.7) C(56.3) D (123.8) E (116.7) Average 119.0 123.7 56.4 115.6 103.5 Standard Deviation 0.161 0.171 0.135 0.173 0.141 V a lues i n......： lodine v al u es ob ta i ne d by wet analy sis me t hod (S t a n dard fa tty oil a na l y s i s me t ho d es t a bl i sh ed by J a p a n Oi l Che mi sts' Socie t y ：Wij s -C yclo h ex an e m e t h o d) JASCO INC. 28600 Mary's C o ur t ， E asto n， MD 21601US A T el ： (800) 333-5272 F ax： (410) 822-7526A ppl ic a tio n Lib r ary： ja s c o i n c.com /appli c a t i o ns