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Jiang H, He Y, Chen Q. Determination of acid value during edible oil storage using a portable NIR spectroscopy system combined with variable selection algorithms based on an MPA-based strategy. JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE 2021; 101:3328-3335. [PMID: 33222172 DOI: 10.1002/jsfa.10962] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Revised: 11/12/2020] [Accepted: 11/22/2020] [Indexed: 06/11/2023]
Abstract
BACKGROUND The acid value is an important indicator for evaluating the quality of edible oil during storage. This study employs a portable near-infrared (NIR) spectroscopy system to determine the acid value during edible oil storage. Four MPA-based variable selection methods, namely competitive adaptive reweighted sampling (CARS), the variable iterative space shrinkage approach (VISSA), iteratively variable subset optimization (IVSO), and bootstrapping soft shrinkage (BOSS) were introduced to optimize the preprocessed NIR spectra. Support vector machine (SVM) models based on characteristic spectra obtained by different selection methods were then established to achieve quantitative detection of the acid value during edible oil storage. RESULTS The results revealed that, compared with the full-spectrum SVM model, the SVM models established by the characteristic wavelengths optimized by the variable selection methods based on the MPA strategy exhibit a significant improvement in complexity and generalization performance. Furthermore, compared with the CARS, VISSA, and IVSO methods, the BOSS method obtained the least number of characteristic wavelength variables, and the SVM model established based on the optimized features of this method exhibited the optimal prediction performance. The root mean square error of prediction (RMSEP) was 0.11 mg g-1, the coefficient of determination (Rp2) was 0.92 and the ratio performance deviation (RPD) was 2.82, respectively. CONCLUSION The overall results indicate that the variable selection methods based on the MPA strategy can select more targeted characteristic variables. This has good application prospects in NIR spectra feature optimization. © 2020 Society of Chemical Industry.
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Affiliation(s)
- Hui Jiang
- School of Electrical and Information Engineering, Jiangsu University, Zhenjiang, China
| | - Yingchao He
- School of Electrical and Information Engineering, Jiangsu University, Zhenjiang, China
| | - Quansheng Chen
- School of Food and Biological Engineering, Jiangsu University, Zhenjiang, China
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2
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Dong Y, Shi S, Li Q, Zhang L, Yu X. An indirect analytical approach based on ATR-FTIR spectroscopy for determining the FFA content in vegetable oils. RSC Adv 2020; 10:24073-24078. [PMID: 35517334 PMCID: PMC9055113 DOI: 10.1039/d0ra03668d] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Accepted: 05/31/2020] [Indexed: 11/21/2022] Open
Abstract
In this study, we developed a novel approach for determining a free fatty acid (FFA) in vegetable oils using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. FFA was converted to carboxylate species by a reaction with phthalimide potassium salt, and the linear relationship between FFA content and ATR-FTIR peak areas at 1541–1616 cm−1 (1595 cm−1 as baseline) was established. Results showed that the R2 values obtained during calibration and validation were more than 0.99. The calibration method concurred to within ±0.035% over the range of 0.4% to 4.0% (quantitative determination of the percentage of FFA in oils, expressed as the percentage of oleic acid). In the calibration model, the root mean square error of prediction was 0.0104, the relative error was less than 0.246% and the relative average deviation was 0.386%, respectively. These indexes demonstrated that the calibration model has great accuracy, high precision and good stability. The indirect method established using ATR-FTIR has the advantages of excellent reproducibility, high exactitude, independent of oil type, simple operation and easy cleaning of the instrument surface. The slope of the verification equation between FFA prediction values and American Oil Chemists' Society's (AOCS) titration method was close to 1, R2 value was more than 0.99. These indicators suggested that the proposed method and the AOCS method have a good correlation through AOCS titration and ATR–FTIR spectroscopy to determine validation samples parallel. In addition, for comparison, when the AOCS titration and ATR-FTIR spectroscopy methods were used for sample validation, the results indicated that the latter method is more reproducible, highly sensitive and has strong anti-disturbance. Therefore, the ATR-FTIR technique can be applied as a simple, highly sensitive, convenient and timely method for the analysis of FFAs in oils. In this study, we developed a novel approach for determining a free fatty acid (FFA) in vegetable oils using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy.![]()
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Affiliation(s)
- Yaoyao Dong
- College of Food Science and Engineering, Northwest A&F University 22 Xinong Road Yangling 712100 Shaanxi P. R. China +86-29-87092486 +86-29-87092275
| | - Shaoxia Shi
- College of Food Science and Engineering, Northwest A&F University 22 Xinong Road Yangling 712100 Shaanxi P. R. China +86-29-87092486 +86-29-87092275
| | - Qi Li
- College of Food Science and Engineering, Northwest A&F University 22 Xinong Road Yangling 712100 Shaanxi P. R. China +86-29-87092486 +86-29-87092275
| | - Lingyan Zhang
- College of Food Science and Engineering, Northwest A&F University 22 Xinong Road Yangling 712100 Shaanxi P. R. China +86-29-87092486 +86-29-87092275
| | - Xiuzhu Yu
- College of Food Science and Engineering, Northwest A&F University 22 Xinong Road Yangling 712100 Shaanxi P. R. China +86-29-87092486 +86-29-87092275
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3
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Abstract
The identification and quantification of free fatty acids (FFA) in edible and non-edible vegetable oils, including waste cooking oils, is a crucial index to assess their quality and drives their use in different application fields. NMR spectroscopy represents an alternative tool to conventional methods for the determination of FFA content, providing us with interesting advantages. Here the approaches reported in the literature based on 1H, 13C and 31P NMR are illustrated and compared, highlighting the pros and cons of the suggested strategies.
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Zhu G, Liu F, Li P, He S, Zhu S, Gao Q, Feng Y. Profiling free fatty acids in edible oils via magnetic dispersive extraction and comprehensive two-dimensional gas chromatography-mass spectrometry. Food Chem 2019; 297:124998. [DOI: 10.1016/j.foodchem.2019.124998] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Revised: 06/07/2019] [Accepted: 06/10/2019] [Indexed: 12/19/2022]
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5
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Monitoring Enzymatic Hydroesterification of Low-Cost Feedstocks by Fourier Transform InfraRed Spectroscopy. Catalysts 2019. [DOI: 10.3390/catal9060535] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Enzymatic hydroesterification is a heterogeneous catalyzed process suitable for the conversion of low-cost feedstocks in biodiesel production, namely, because of its tolerance to high free fatty acid contents. The current study describes the use of Fourier transform infrared spectroscopy (FTIR) to monitor biodiesel production using enzymatic hydroesterification and, as raw materials, acid oil from soapstock and olive pomace oil. Acid oil (~34 wt.% FFA) and olive pomace oil (~50 wt.% FFA) were first hydrolyzed (35 °C, 24 h, 200 rpm, 3 wt.% of lipase from Thermomyces lanuginosus, and 1:0.5 water:oil ratio, w:w), and then enzymatic esterification was performed (35 °C, 7 h, 200 rpm, 2 wt.% of lipase from Thermomyces lanuginosus, and 2:1 molar ratio of methanol to acid). FTIR analyses were conducted on the products using a Jasco FT/IR-4100 with a scanning range of 4000–650 cm−1 at 4 cm−1 spectral resolution and 54 scans. For free fatty acid (FFA) quantification, the C=O band at 1708 cm–1 was used, corresponding to the carboxylic acid, whereas for fatty acid methyl ester (FAME) quantification, the peak corresponding to C=O at 1746 cm−1 was considered, which corresponded to the ester. The results were calibrated using volumetric titration and gas chromatography analyses, concerning FFA and FAME quantification, respectively. The best conditions for analysis were determined, and a calibration method was established. FTIR has shown to be a simple, fast, and clean technique suitable to monitor hydroesterification of low-cost feedstocks.
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Hu K, Huyan Z, Geng Q, Yu X. Rapid Determination of Acid Value of Edible Oils via FTIR Spectroscopy Using Infrared Quartz Cuvette. J Oleo Sci 2019; 68:121-129. [PMID: 30651412 DOI: 10.5650/jos.ess18156] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
A Fourier transform infrared (FTIR) spectroscopy with infrared quartz cuvette (IQC) as spectral accessory method was developed to determine acid value (AV) of edible oils. The absorption peak at 5680 cm-1/5487 cm-1 ascribed to the C-H stretching band was a substitute for the peak of an internal standard. Partial least square (PLS) regression was used for AV calibration, and samples were validated by titrated method. Results showed dilution calibration was feasible for randomly dilution among 6-13:1 (CCl4: oils, v/v). PLS calibration was optimal by a spectral wavenumber (3603 cm-1-3250 cm-1) as the first derivative treatment. Correlation coefficient and root mean square error of calibration were 0.9967 and 0.135, respectively. Calibrated validation, blind sample validation and precision analysis presented a good correlation between IQC-FTIR and titrated methods. Based on the dilution calibration, randomly diluted oil samples can be employed by IQC-FTIR.
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Affiliation(s)
- Keqing Hu
- College of Food Science and Engineering, Northwest A&F University
| | - Zongyao Huyan
- College of Food Science and Engineering, Northwest A&F University
| | - Qiaona Geng
- College of Food Science and Engineering, Northwest A&F University
| | - Xiuzhu Yu
- College of Food Science and Engineering, Northwest A&F University
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Li Q, Chen J, Huyan Z, Kou Y, Xu L, Yu X, Gao JM. Application of Fourier transform infrared spectroscopy for the quality and safety analysis of fats and oils: A review. Crit Rev Food Sci Nutr 2018; 59:3597-3611. [DOI: 10.1080/10408398.2018.1500441] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- Qi Li
- College of Food Science and Engineering, Northwest A&F University, Shaanxi, P R China
| | - Jia Chen
- College of Food Science and Engineering, Northwest A&F University, Shaanxi, P R China
| | - Zongyao Huyan
- College of Food Science and Engineering, Northwest A&F University, Shaanxi, P R China
| | - Yuxing Kou
- College of Food Science and Engineering, Northwest A&F University, Shaanxi, P R China
| | - Lirong Xu
- College of Food Science and Engineering, Northwest A&F University, Shaanxi, P R China
| | - Xiuzhu Yu
- College of Food Science and Engineering, Northwest A&F University, Shaanxi, P R China
| | - Jin-Ming Gao
- Shaanxi Key Laboratory of Natural Products & Chemical Biology, College of Chemistry & Pharmacy, Northwest A&F University, 22 Xinong Road Yangling, Shaanxi, P R China
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Giese E, Winkelmann O, Rohn S, Fritsche J. Determining quality parameters of fish oils by means of 1H nuclear magnetic resonance, mid-infrared, and near-infrared spectroscopy in combination with multivariate statistics. Food Res Int 2018; 106:116-128. [DOI: 10.1016/j.foodres.2017.12.041] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Revised: 11/07/2017] [Accepted: 12/14/2017] [Indexed: 02/03/2023]
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9
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Li M, Xu L, Yu X, Chen J, Liu X. Novel method based on fourier transform infrared spectroscopy for determining fat acidity of cereal products. INTERNATIONAL JOURNAL OF FOOD PROPERTIES 2018. [DOI: 10.1080/10942912.2017.1381113] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- Mengjun Li
- College of Food Science and Engineering, Northwest A&F University, Yangling Shaanxi, P. R. China
| | - Lirong Xu
- College of Food Science and Engineering, Northwest A&F University, Yangling Shaanxi, P. R. China
| | - Xiuzhu Yu
- College of Food Science and Engineering, Northwest A&F University, Yangling Shaanxi, P. R. China
| | - Jia Chen
- College of Food Science and Engineering, Northwest A&F University, Yangling Shaanxi, P. R. China
| | - Xiaoli Liu
- College of Food Science and Engineering, Northwest A&F University, Yangling Shaanxi, P. R. China
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Attenuated Total Reflectance Fourier transform infrared spectroscopy for determination of Long Chain Free Fatty Acid concentration in oily wastewater using the double wavenumber extrapolation technique. Talanta 2017; 165:526-532. [DOI: 10.1016/j.talanta.2017.01.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Revised: 01/02/2017] [Accepted: 01/03/2017] [Indexed: 11/24/2022]
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Jiang X, Li S, Xiang G, Li Q, Fan L, He L, Gu K. Determination of the acid values of edible oils via FTIR spectroscopy based on the OH stretching band. Food Chem 2016; 212:585-9. [DOI: 10.1016/j.foodchem.2016.06.035] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2015] [Revised: 05/16/2016] [Accepted: 06/13/2016] [Indexed: 10/21/2022]
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12
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Meng X, Li L, Ye Q, van de Voort F. Fourier Transform Infrared (FTIR) Spectroscopy as a Utilitarian Tool for the Routine Determination of Acidity in Ester-Based Oils. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2015; 63:8333-8338. [PMID: 26321291 DOI: 10.1021/acs.jafc.5b02738] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
A primary Fourier transform infrared (FTIR) method capable of determining acidity in ester-based oils is described and evaluated. Absolute free fatty acid (%FFA) and acid value (AV) calibrations were devised by spiking oleic acid into a refined, acid-free oil and measuring ν COO(-) at ∼ 1569 and ν phenolate(-) at ∼ 1588 cm(-1), respectively, in the second-derivative differential spectra. The FTIR acidity predictions were compared to the AOCS titrimetric method using acid mixtures as well as acid containing used vendor oils of undefined makeup and provenance, using two spectroscopically divergent reference oils as AC0. Relative to the AOCS reference method, the FTIR procedure was found to be both more accurate (± 0.107 vs ± 0.122) and reproducible (± 0.025 vs ± 0.077) in determining %FFA and similar in predicting AV. The FTIR phenolate method overcomes a variety of limitations of earlier FTIR-based methods, being particularly simple and well suited to routine, semiautomated acidity analysis of ester-based oils using a basic FTIR spectrometer.
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Affiliation(s)
- Xianghe Meng
- Ocean College, Zhejiang University of Technology , 18 Chaowang Road, Hangzhou 310014, China
| | - Lei Li
- Ocean College, Zhejiang University of Technology , 18 Chaowang Road, Hangzhou 310014, China
| | - Qin Ye
- Ocean College, Zhejiang University of Technology , 18 Chaowang Road, Hangzhou 310014, China
| | - Frederik van de Voort
- McGill IR Group, Department of Food Science and Agricultural Chemistry, McGill University , Montreal H9X 3V9, Canada
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13
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Wang LF, Swift ML, Zijlstra RT. A noncalibration spectroscopic method to estimate ether extract and fatty acid digestibility of feed and its validation with flaxseed and field pea in pigs. J Anim Sci 2014; 92:4531-9. [PMID: 25186953 DOI: 10.2527/jas.2013-7210] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Digestibility of ether extract (EE) or fatty acids (FA) is traditionally measured by chemical analyses for EE or GLC methods for FA combined with marker concentration in diet and digesta or feces. Digestibility of EE or FA may be predicted by marker concentrations and spectral analyses of diet and digesta or feces. On the basis of Beer's law, a noncalibration spectroscopic method, which used functional group digestibility (FGD) determined with marker concentration and peak intensity of spectra of diets and undigested residues (digesta or feces), was developed to predict the apparent ileal digestibility (AID) of total FA and apparent total tract digestibility (ATTD) of EE. To validate, 4 diets containing 30% flaxseed and field pea coextruded with 4 extruder treatments and a wheat and soybean basal diet with predetermined AID of total FA and ATTD of EE were used. Samples of ingredients, diets, and freeze-dried digesta and feces were scanned on a Fourier transform infrared (FT-IR) instrument with a single-reflection attenuated total reflection (ATR) accessory. The intensity of either the methylene (CH2) antisymmetric stretching peak at 2,923 cm(-1) (R(2) = 0.90, P < 0.01) or the symmetric stretching peak at 2,852 cm(-1) (R(2) = 0.86, P < 0.01) of ingredients, diet, and digesta spectra was related strongly to the concentration of total FA. The AID of total FA of diets measured using GLC was predicted by the spectroscopic method using FGD at 2,923 and 2,852 cm(-1) (R(2) = 0.75, P < 0.01) with a bias of 0.54 (SD = 3.78%) and -1.35 (SD = 3.74%), respectively. The accumulated peak intensity in the region between 1,766 and 1,695 cm(-1) of spectra was related to EE concentration in ingredients and diets (R(2) = 0.61, P = 0.01) and feces (R(2) = 0.88, P < 0.01). The relation was improved by using second-derivative spectra of the sum of peak intensities at 1,743 and 1,710 cm(-1) for ingredients and diets (R(2) = 0.90, P = 0.01) and at 1,735 and 1,710 cm(-1) for feces (R(2) = 0.92, P < 0.01). The ATTD of EE of test diets determined with proximate analysis was estimated by the FGD of nonderivative spectra with or without baseline (R(2) = 0.90, P < 0.01) with a bias of 3.15 (SD = 3.14%) and 3.50 (SD = 3.24%), respectively. In conclusion, instead of using GLC methods or predictions based on calibrations, the AID of total FA and ATTD of EE can also be estimated directly from ATR FT-IR spectra, provided the ratio of marker in the diet and undigested residue is known.
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Affiliation(s)
- L F Wang
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB T6G 2P5, Canada
| | - M L Swift
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB T6G 2P5, Canada Alberta Agriculture and Rural Development, Lethbridge, AB T1J 4V6, Canada
| | - R T Zijlstra
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB T6G 2P5, Canada
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Tavassoli‐Kafrani MH, Curtis JM, van de Voort FR. A single‐sample method to determine the hydroxyl values of polyols using mid‐FTIR spectroscopy. EUR J LIPID SCI TECH 2014. [DOI: 10.1002/ejlt.201400256] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
| | - Jonathan M. Curtis
- Lipid Chemistry Group, Department of Agricultural, Food and Nutritional ScienceUniversity of AlbertaEdmontonAlberta, CanadaT6G 2P5
| | - Frederik R. van de Voort
- McGill IR Group, Department of Food ScienceMcGill UniversitySt. Anne de BellevueQuebec, CanadaH9X 2V9
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15
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Direct FTIR Analysis of Free Fatty Acids in Edible Oils Using Disposable Polyethylene Films. FOOD ANAL METHOD 2014. [DOI: 10.1007/s12161-014-9963-y] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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16
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Frontiers of two-dimensional correlation spectroscopy. Part 2. Perturbation methods, fields of applications, and types of analytical probes. J Mol Struct 2014. [DOI: 10.1016/j.molstruc.2014.01.016] [Citation(s) in RCA: 81] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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17
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Skiera C, Steliopoulos P, Kuballa T, Diehl B, Holzgrabe U. Determination of free fatty acids in pharmaceutical lipids by ¹H NMR and comparison with the classical acid value. J Pharm Biomed Anal 2013; 93:43-50. [PMID: 23664852 DOI: 10.1016/j.jpba.2013.04.010] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Revised: 04/08/2013] [Accepted: 04/10/2013] [Indexed: 10/26/2022]
Abstract
Indices like acid value, peroxide value, and saponification value play an important role in quality control and identification of lipids. Requirements on these parameters are given by the monographs of the European pharmacopeia. (1)H NMR spectroscopy provides a fast and simple alternative to these classical approaches. In the present work a new (1)H NMR approach to determine the acid value is described. The method was validated using a statistical approach based on a variance components model. The performance under repeatability and in-house reproducibility conditions was assessed. We applied this (1)H NMR assay to a wide range of different fatty oils. A total of 305 oil and fat samples were examined by both the classical and the NMR method. Except for hard fat, the data obtained by the two methods were in good agreement. The (1)H NMR method was adapted to analyse waxes and oleyloleat. Furthermore, the effect of solvent and in the case of castor oil the effect of the oil matrix on line broadening and chemical shift of the carboxyl group signal are discussed.
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Affiliation(s)
- Christina Skiera
- Institute of Pharmacy and Food Chemistry, University of Würzburg, Am Hubland, 97074 Würzburg, Germany; Chemisches und Veterinäruntersuchungsamt Karlsruhe, Weißenburger Str. 3, 76187 Karlsruhe, Germany.
| | - Panagiotis Steliopoulos
- Chemisches und Veterinäruntersuchungsamt Karlsruhe, Weißenburger Str. 3, 76187 Karlsruhe, Germany
| | - Thomas Kuballa
- Chemisches und Veterinäruntersuchungsamt Karlsruhe, Weißenburger Str. 3, 76187 Karlsruhe, Germany
| | - Bernd Diehl
- Spectral Service, Emil-Hoffmann-Str. 33, 50996 Köln, Germany
| | - Ulrike Holzgrabe
- Institute of Pharmacy and Food Chemistry, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
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One Step Ultrasound Extraction and Purification Method for the Gas Chromatographic Analysis of Hydrocarbons from Marine Sediments: Application to the Monitoring of Italian Coasts. Chromatographia 2011. [DOI: 10.1007/s10337-011-2172-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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