TY  - JOUR
AU  - Ražić, Slavica
AU  - Bakić, Tamara
AU  - Topić, Aleksandra
AU  - Lukić, Jelena
AU  - Onjia, Antonije
PY  - 2023
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/4549
AB  - A fast and straightforward reversed-phase dispersive liquid–liquid microextraction (RP-DLLME) using a deep eutectic solvent (DES) procedure to determine free tryptophan in vegetable oils was developed. The influence of eight variables affecting the RP-DLLME efficiency has been studied by a multivariate approach. A Plackett–Burman design for screening the most influential variables followed by a central composite response surface methodology led to an optimum RP-DLLME setup for a 1 g oil sample: 9 mL hexane as the diluting solvent, vortex extraction with 0.45 mL of DES (choline chloride–urea) at 40 °C, without addition of salt, and centrifugation at 6000 rpm for 4.0 min. The reconstituted extract was directly injected into a high-performance liquid chromatography (HPLC) system working in the diode array mode. At the studied concentration levels, the obtained method detection limits (MDL) was 11 mg/kg, linearity in matrix-matched standards was R2 ≥ 0.997, relative standard deviations (RSD) was 7.8%, and average recovery was 93%. The combined use of the recently developed DES -based RP-DLLME and HPLC provides an innovative, efficient, cost-effective, and more sustainable method for the extraction and quantification of free tryptophan in oily food matrices. The method was employed to analyze cold-pressed oils from nine vegetables (Brazil nut, almond, cashew, hazelnut, peanut, pumpkin, sesame, sunflower, and walnut) for the first time. The results showed that free tryptophan was present in the range of 11–38 mg/100 g. This article is important for its contributions to the field of food analysis, and for its development of a new and efficient method for the determination of free tryptophan in complex matrices, which has the potential to be applied to other analytes and sample types.
PB  - MDPI
T2  - Molecules
T1  - Deep Eutectic Solvent Based Reversed-Phase Dispersive Liquid–Liquid Microextraction and High-Performance Liquid Chromatography for the Determination of Free Tryptophan in Cold-Pressed Oils
VL  - 28
IS  - 5
DO  - 10.3390/molecules28052395
ER  - 

@article{
author = "Ražić, Slavica and Bakić, Tamara and Topić, Aleksandra and Lukić, Jelena and Onjia, Antonije",
year = "2023",
abstract = "A fast and straightforward reversed-phase dispersive liquid–liquid microextraction (RP-DLLME) using a deep eutectic solvent (DES) procedure to determine free tryptophan in vegetable oils was developed. The influence of eight variables affecting the RP-DLLME efficiency has been studied by a multivariate approach. A Plackett–Burman design for screening the most influential variables followed by a central composite response surface methodology led to an optimum RP-DLLME setup for a 1 g oil sample: 9 mL hexane as the diluting solvent, vortex extraction with 0.45 mL of DES (choline chloride–urea) at 40 °C, without addition of salt, and centrifugation at 6000 rpm for 4.0 min. The reconstituted extract was directly injected into a high-performance liquid chromatography (HPLC) system working in the diode array mode. At the studied concentration levels, the obtained method detection limits (MDL) was 11 mg/kg, linearity in matrix-matched standards was R2 ≥ 0.997, relative standard deviations (RSD) was 7.8%, and average recovery was 93%. The combined use of the recently developed DES -based RP-DLLME and HPLC provides an innovative, efficient, cost-effective, and more sustainable method for the extraction and quantification of free tryptophan in oily food matrices. The method was employed to analyze cold-pressed oils from nine vegetables (Brazil nut, almond, cashew, hazelnut, peanut, pumpkin, sesame, sunflower, and walnut) for the first time. The results showed that free tryptophan was present in the range of 11–38 mg/100 g. This article is important for its contributions to the field of food analysis, and for its development of a new and efficient method for the determination of free tryptophan in complex matrices, which has the potential to be applied to other analytes and sample types.",
publisher = "MDPI",
journal = "Molecules",
title = "Deep Eutectic Solvent Based Reversed-Phase Dispersive Liquid–Liquid Microextraction and High-Performance Liquid Chromatography for the Determination of Free Tryptophan in Cold-Pressed Oils",
volume = "28",
number = "5",
doi = "10.3390/molecules28052395"
}

Ražić, S., Bakić, T., Topić, A., Lukić, J.,& Onjia, A.. (2023). Deep Eutectic Solvent Based Reversed-Phase Dispersive Liquid–Liquid Microextraction and High-Performance Liquid Chromatography for the Determination of Free Tryptophan in Cold-Pressed Oils. in Molecules
MDPI., 28(5).
https://doi.org/10.3390/molecules28052395

Ražić S, Bakić T, Topić A, Lukić J, Onjia A. Deep Eutectic Solvent Based Reversed-Phase Dispersive Liquid–Liquid Microextraction and High-Performance Liquid Chromatography for the Determination of Free Tryptophan in Cold-Pressed Oils. in Molecules. 2023;28(5).
doi:10.3390/molecules28052395 .

Ražić, Slavica, Bakić, Tamara, Topić, Aleksandra, Lukić, Jelena, Onjia, Antonije, "Deep Eutectic Solvent Based Reversed-Phase Dispersive Liquid–Liquid Microextraction and High-Performance Liquid Chromatography for the Determination of Free Tryptophan in Cold-Pressed Oils" in Molecules, 28, no. 5 (2023),
https://doi.org/10.3390/molecules28052395 . .

TY  - JOUR
AU  - Ražić, Slavica
AU  - Onjia, Antonije
PY  - 2010
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/1363
AB  - Chemical analysis in conjunction with multivariate data evaluation methods was used to study elemental profiles and geographical origin of wines from central Balkan countries (Serbia Montenegro and Macedonia) Nine elements (Na K Mg Ca Fe Mn Zn Cu and Pb) chosen as chemical descriptors were analyzed in 41 commercial wine samples Unsupervised pattern recognition methods principal component analysis (PCA) and factor analysis identified the main factors controlling the data variability while the application of hierarchical cluster analysis (HCA) highlighted a differentiation between sample groups belonging to different variable inputs Three PCs were shown to be the most significant together accounting for 70 8% of the total variance Supervised pattern recognition methods linear discriminant analysis (LDA) k nearest neighbor (kNN) soft independent modeling of class analogy (SIMCA) and artificial neural network (ANN) applied to the classification of wine samples demonstrated different recognition and prediction abilities The recognition rate for LDA was 97 6% and the percentage of classification obtained by kNN SIMCA and ANN was 100% However the LDA method produced the best prediction rate of 83 3% whereas kNN SIMCA and ANN gave much lower percentages of correctly classified samples at 72 2 61 1 and 55 6% respectively Trace elements seem to be suitable descriptors for wine samples studied by classification methods since their concentrations comprising both natural and other sources of influence are attributed to grapegrowing and winemaking sites Comparison of pattern recognition methods reveals the difference in their classification power
PB  - Amer Soc Enology Viticulture, Davis
T2  - American Journal of Enology and Viticulture
T1  - Trace Element Analysis and Pattern Recognition Techniques in Classification of Wine from Central Balkan Countries
VL  - 61
IS  - 4
SP  - 506
EP  - 511
DO  - 10.5344/ajev.2010.10002
ER  - 

@article{
author = "Ražić, Slavica and Onjia, Antonije",
year = "2010",
abstract = "Chemical analysis in conjunction with multivariate data evaluation methods was used to study elemental profiles and geographical origin of wines from central Balkan countries (Serbia Montenegro and Macedonia) Nine elements (Na K Mg Ca Fe Mn Zn Cu and Pb) chosen as chemical descriptors were analyzed in 41 commercial wine samples Unsupervised pattern recognition methods principal component analysis (PCA) and factor analysis identified the main factors controlling the data variability while the application of hierarchical cluster analysis (HCA) highlighted a differentiation between sample groups belonging to different variable inputs Three PCs were shown to be the most significant together accounting for 70 8% of the total variance Supervised pattern recognition methods linear discriminant analysis (LDA) k nearest neighbor (kNN) soft independent modeling of class analogy (SIMCA) and artificial neural network (ANN) applied to the classification of wine samples demonstrated different recognition and prediction abilities The recognition rate for LDA was 97 6% and the percentage of classification obtained by kNN SIMCA and ANN was 100% However the LDA method produced the best prediction rate of 83 3% whereas kNN SIMCA and ANN gave much lower percentages of correctly classified samples at 72 2 61 1 and 55 6% respectively Trace elements seem to be suitable descriptors for wine samples studied by classification methods since their concentrations comprising both natural and other sources of influence are attributed to grapegrowing and winemaking sites Comparison of pattern recognition methods reveals the difference in their classification power",
publisher = "Amer Soc Enology Viticulture, Davis",
journal = "American Journal of Enology and Viticulture",
title = "Trace Element Analysis and Pattern Recognition Techniques in Classification of Wine from Central Balkan Countries",
volume = "61",
number = "4",
pages = "506-511",
doi = "10.5344/ajev.2010.10002"
}

Ražić, S.,& Onjia, A.. (2010). Trace Element Analysis and Pattern Recognition Techniques in Classification of Wine from Central Balkan Countries. in American Journal of Enology and Viticulture
Amer Soc Enology Viticulture, Davis., 61(4), 506-511.
https://doi.org/10.5344/ajev.2010.10002

Ražić S, Onjia A. Trace Element Analysis and Pattern Recognition Techniques in Classification of Wine from Central Balkan Countries. in American Journal of Enology and Viticulture. 2010;61(4):506-511.
doi:10.5344/ajev.2010.10002 .

Ražić, Slavica, Onjia, Antonije, "Trace Element Analysis and Pattern Recognition Techniques in Classification of Wine from Central Balkan Countries" in American Journal of Enology and Viticulture, 61, no. 4 (2010):506-511,
https://doi.org/10.5344/ajev.2010.10002 . .

TY  - JOUR
AU  - Ražić, Slavica
AU  - Onjia, Antonije
AU  - Đogo-Mračević, Svetlana
AU  - Slavković, Latinka
AU  - Popović, Aleksandar
PY  - 2005
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/577
AB  - The concentrations of Cu, Zn, Mn, Fe, K, Ca, Mg, Al, Ba and B in 26 herbal drugs of special importance in phytopharmacywere studied. Flame atomic absorption and emission spectrometry (FAAS, FAES), as well as inductively coupled plasma atomic emission spectrometry (ICP-AES), were applied in this work. The whole procedure, from sample preparation, via dissolution, to measurements, was validated by using CRM (NIST 1573a-tomato leaves), and the obtained recovery values are in the range from 91 to 102%. Drug samples originated from medicinal plants cultivated in Serbia contained Cu (4.47-14.08 mg kg(-1)), Zn (8.4-54.5 mg kg(-1)), Mn (9-155 mg kg(-1)), Fe (47-546 mg kg(-1)), K (0.20-6.24%), Ca (0.18-1.84%), Mg (0.13-1.09%), Al (16-416 mg kg(-1)), Ba (11.70-84.83 mg kg(-1)) and B (5.1-118.7 mg kg(-1)). In order to get a better insight into the elemental patterns, a common chemometric approach to data evaluation was used. Four significant factors identified by principal component analysis (PCA) were attributed partly to the significant influential sources and high mobility of some elements thus referring to potential anthropogenic contamination as well.
PB  - Elsevier Science BV, Amsterdam
T2  - Talanta
T1  - Determination of metal content in some herbal drugs - Empirical and chemometric approach
VL  - 67
IS  - 1
SP  - 233
EP  - 239
DO  - 10.1016/j.talanta.2005.03.023
ER  - 

@article{
author = "Ražić, Slavica and Onjia, Antonije and Đogo-Mračević, Svetlana and Slavković, Latinka and Popović, Aleksandar",
year = "2005",
abstract = "The concentrations of Cu, Zn, Mn, Fe, K, Ca, Mg, Al, Ba and B in 26 herbal drugs of special importance in phytopharmacywere studied. Flame atomic absorption and emission spectrometry (FAAS, FAES), as well as inductively coupled plasma atomic emission spectrometry (ICP-AES), were applied in this work. The whole procedure, from sample preparation, via dissolution, to measurements, was validated by using CRM (NIST 1573a-tomato leaves), and the obtained recovery values are in the range from 91 to 102%. Drug samples originated from medicinal plants cultivated in Serbia contained Cu (4.47-14.08 mg kg(-1)), Zn (8.4-54.5 mg kg(-1)), Mn (9-155 mg kg(-1)), Fe (47-546 mg kg(-1)), K (0.20-6.24%), Ca (0.18-1.84%), Mg (0.13-1.09%), Al (16-416 mg kg(-1)), Ba (11.70-84.83 mg kg(-1)) and B (5.1-118.7 mg kg(-1)). In order to get a better insight into the elemental patterns, a common chemometric approach to data evaluation was used. Four significant factors identified by principal component analysis (PCA) were attributed partly to the significant influential sources and high mobility of some elements thus referring to potential anthropogenic contamination as well.",
publisher = "Elsevier Science BV, Amsterdam",
journal = "Talanta",
title = "Determination of metal content in some herbal drugs - Empirical and chemometric approach",
volume = "67",
number = "1",
pages = "233-239",
doi = "10.1016/j.talanta.2005.03.023"
}

Ražić, S., Onjia, A., Đogo-Mračević, S., Slavković, L.,& Popović, A.. (2005). Determination of metal content in some herbal drugs - Empirical and chemometric approach. in Talanta
Elsevier Science BV, Amsterdam., 67(1), 233-239.
https://doi.org/10.1016/j.talanta.2005.03.023

Ražić S, Onjia A, Đogo-Mračević S, Slavković L, Popović A. Determination of metal content in some herbal drugs - Empirical and chemometric approach. in Talanta. 2005;67(1):233-239.
doi:10.1016/j.talanta.2005.03.023 .

Ražić, Slavica, Onjia, Antonije, Đogo-Mračević, Svetlana, Slavković, Latinka, Popović, Aleksandar, "Determination of metal content in some herbal drugs - Empirical and chemometric approach" in Talanta, 67, no. 1 (2005):233-239,
https://doi.org/10.1016/j.talanta.2005.03.023 . .

TY  - JOUR
AU  - Ražić, Slavica
AU  - Onjia, Antonije
AU  - Potkonjak, B
PY  - 2003
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/427
AB  - Elemental composition of Echinacea purpurea (Asteracae), grown in Serbia under strongly controlled conditions, has been studied. To distinguish elemental patterns of different parts of the plant, the content of Zn, Fe, Cu, Mn, Ca, Mg, Sr, Ni, and Li in root versus upper plant parts were determined, by flame atomic absorption and flame atomic emission spectrometry. Analyses of the mentioned elements in soil and in an ethanolic extract of E. purpurea were made, too. The trace element data were evaluated by multivariate methods, i.e. principal component analysis and hierarchical cluster analysis. This revealed two groups of elements (I: Fe, Cu, Mn, Li; II: Ca, Mg, Zn, Ni), while trace element profiles of root. stem, leaves, and flowers of this plant differed significantly. However, no significant difference in the trace element patterns between the summer and the autumn harvest samples was found.
PB  - Elsevier Science BV, Amsterdam
T2  - Journal of Pharmaceutical and Biomedical Analysis
T1  - Trace elements analysis of Echinacea purpurea - herbal medicinal
VL  - 33
IS  - 4
SP  - 845
EP  - 850
DO  - 10.1016/S0731-7085(03)00338-8
ER  - 

@article{
author = "Ražić, Slavica and Onjia, Antonije and Potkonjak, B",
year = "2003",
abstract = "Elemental composition of Echinacea purpurea (Asteracae), grown in Serbia under strongly controlled conditions, has been studied. To distinguish elemental patterns of different parts of the plant, the content of Zn, Fe, Cu, Mn, Ca, Mg, Sr, Ni, and Li in root versus upper plant parts were determined, by flame atomic absorption and flame atomic emission spectrometry. Analyses of the mentioned elements in soil and in an ethanolic extract of E. purpurea were made, too. The trace element data were evaluated by multivariate methods, i.e. principal component analysis and hierarchical cluster analysis. This revealed two groups of elements (I: Fe, Cu, Mn, Li; II: Ca, Mg, Zn, Ni), while trace element profiles of root. stem, leaves, and flowers of this plant differed significantly. However, no significant difference in the trace element patterns between the summer and the autumn harvest samples was found.",
publisher = "Elsevier Science BV, Amsterdam",
journal = "Journal of Pharmaceutical and Biomedical Analysis",
title = "Trace elements analysis of Echinacea purpurea - herbal medicinal",
volume = "33",
number = "4",
pages = "845-850",
doi = "10.1016/S0731-7085(03)00338-8"
}

Ražić, S., Onjia, A.,& Potkonjak, B.. (2003). Trace elements analysis of Echinacea purpurea - herbal medicinal. in Journal of Pharmaceutical and Biomedical Analysis
Elsevier Science BV, Amsterdam., 33(4), 845-850.
https://doi.org/10.1016/S0731-7085(03)00338-8

Ražić S, Onjia A, Potkonjak B. Trace elements analysis of Echinacea purpurea - herbal medicinal. in Journal of Pharmaceutical and Biomedical Analysis. 2003;33(4):845-850.
doi:10.1016/S0731-7085(03)00338-8 .

Ražić, Slavica, Onjia, Antonije, Potkonjak, B, "Trace elements analysis of Echinacea purpurea - herbal medicinal" in Journal of Pharmaceutical and Biomedical Analysis, 33, no. 4 (2003):845-850,
https://doi.org/10.1016/S0731-7085(03)00338-8 . .