Dimitrieska Stojkovikj, Elizabeta

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Dimitrieska Stojkovikj, Elizabeta

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Analysis of 226Ra, 232Th 40К and 137Cs in samples of soil from some areas of Republic of Macedonia by using gamma spectrometry
(Mac Vet Rev, 2013-10-15)
Todorovic Aleksandra
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Stojanovska-Dimzoska Biljana
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In-house validation and quality control of commercial enzyme-linked immunosorbnet assays for screening of nitrofuran metabolites in food of animal origin
(Mac Vet Rev, 2013-03-15)
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Arsova Gordana
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Stojanovska-Dimzoska Biljana
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Validation of screening method for determination of methyltestosterone in fish
(Mac Vet Rev, 2013-03-15)
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Stojanovska-dimzoska biljana
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Todorovic Aleksandra
Anabolic androgenic steroids are synthetic derivatives of testosterone, which is the primary male sex hormone. These anabolic agents are used to increase the weight gain, to improve the food efficiency, storing proteins and to decrease fatness. However, depending on the use of anabolic agent in animal feed, anabolic residues that may occur in meat and meat products present risks to human health. The aim of this study was the validation of screening ELISA method for determination of methyltestoterone anabolic steroid in fish. The validation process was carried out according to Commission Decision 2002/657/EC criteria. The detection limit for methyltestosterone was 140.95 ng/kg and the detection capability was 564.43 ng/kg. The overall recoveries and the coefficients of variation (CV) were in the range of 82.4%-97.4% and 1.5%-6.9%, respectively, a working range between 50 to 4050 ng/kg, and the regression equation of the final inhibition curve was: y= -0,1741x + 1,5082, R2 = 0.9927. Because of the good recovery and precision, and satisfactory detection capability, this method is applicable in official control laboratories as a rapid screening method for determination of methyltestosterone in fish.
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Multi-class/residue method for determination of veterinary drug residues, mycotoxins and pesticide in urine using LC-MS/MS technique
(Springer Science and Business Media LLC, 2023-09-14)
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Jovanov, Stefan
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Musliu, Dea
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Background Veterinary drugs are widely used in animals to prevent diseases and are a complex set of drugs with very different chemical properties. Multiclass and multi-residue methods for simultaneous detection of residues from veterinary drugs and contaminants in urine are very rare or non-existent. Therefore, the aim of this study was to develop and validate a sensitive and reliable quantitative LC-MS/MS method for simultaneous determination of a wide range of veterinary drug and pesticide residues and mycotoxins in bovine urine. This involved 42 veterinary drug residues (4 thyreostats, 6 anabolic hormones, 2 lactones, 10 beta agonists, 15 antibiotics, 5 sulphonamides), 28 pesticides and 2 mycotoxins. Stable isotopically labelled internal standards were used to facilitate effective quantification of the analytes. Analysis was performed in both positive and negative ionization modes with multiple reaction monitoring transitions over a period of 12 min. Results The parameters validated included linearity, limit of detection (LOD), limit of quantification (LOQ), detection capability (CCβ), decision limit (CCα), stability, accuracy and precision. The process followed guidelines of the regulation 2021/808/EC. The calibration curves were linear with coefficient of correlation (R2) from 0.991 to 0.999. The LODs were from 0.01 to 2.71 µg/L, while the LOQs were from 0.05 to 7.52 µg/L. The CCα and CCβ were in range 0.05–12.11 µg/L and 0.08–15.16 µg/L. In addition, the average recoveries of the spiked urine samples were from 71.0 to 117.0% and coefficient of variation (CV) < 21.38% (intraday and interday). Conclusion A new isotopic LC-MS/MS method has been developed, validated and applied for identification and quantification of 72 residues of veterinary drugs and pesticides and other contaminants such as mycotoxins in bovine urine. The most appropriated sample preparation procedures involved sodium acetate buffer, enzymatic hydrolysis using β-glucuronidase and cleanup solid phase extraction with OASIS SPE cartridges. The parameters were satisfactorily validated fulfilling requirements under Regulation 2021/808/EC. Consequently, the method could be used in routine analysis of bovine urine samples for simultaneous detection of veterinary drug and pesticide residues as well as contaminants such as mycotoxins.
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Radiation levels in samples of dicalcium phosphate (DCP) with a gamma spectrometry method.
(UNIVERSITY OF EAST SARAJEVO FACULTY OF AGRICULTURE, Republic of Srpska, B&H et al, 2021-10-07)
Angeleska, Aleksandra
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Stojanovska-Dimzoska, Biljana
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Radiocesium concentration in mushrooms collected in the Republic of North Macedonia
(Agricultural University of Tirana, 2021-11-03)
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Angeleska, Aleksandra
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Measurement of the 226Ra, 232Th and 40K activities in corn in the Republic of North Macedonia and resulting annual radiation dose by ingestion
(University of Banja Luka Faculty of Agriculture University City Bulevar vojvode Petra Bojovića 1A 78000 Banja Luka, Republic of Srpska, B&H, 2021-05-27)
Angeleska, Aleksandra
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Considering the fact that there has been a significant population growth and this increases the need of food, various agricultural activities are increasingly being used, including the use of phosphate fertilizers that can directly affect agricultural crops. Therefore, it is necessary to know the level of present radionuclides, especially in corn, which is very often used for the needs of people and animals. The purpose of this study was focused on comparing the activity concentrations of 226Ra, 232Th, 40K in corn samples, and the calculated results were the basis for the assessment of the external hazard index (Hex), the internal hazard index (Hin), the radium equivalent activity (Raeq), and the annual gonadal dose equivalent (Dgon). The gamma spectrometry technique was used for measurement of the samples, i.e. an instrument - gamma spectrometer (Canbera Packard) with a high purity germanium detector. The obtained spectra from the measurement were analyzed by using the GENIE 2000 program. Based on the performed examinations, the activity concentrations in corn ranged from 0.42 to 0.77 Bq kg - 1 for 226Ra, from 0.06 to 0.87 Bq kg - 1 for 232Th, and from 117.54 to 322.11 Bq kg - 1 for 40K. The mean value of the radiation hazard index, the Heks value is lower than the maximum allowed value which is <1 for Heks. The value of the radium equivalent activity Raeq ranges from 9.01 to 23.16 and is below the maximum recommended limit, i.e. 370 Bq kg-1. The annual gonadal dose equivalent has an average value of 75.62. The research in this study shows that all samples of corn have no biological hazard i.e. it was found that the natural levels of radioactivity are not within the high-risk range and are below the international standards.
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VALIDATION OF UHPLC-MS/MS METHOD AFTER MODIFIED QUECHERS SAMPLE PREPARATION FOR MONITORING OF PESTICIDE RESIDUES IN BOVINE MILK ACCORDING TO EC/2018/555
(Ss. CYRIL AND METHODIUS UNIVERSITY IN SKOPJE FACULTY OF VETERINARY MEDICINE - SKOPJE, 2022-09-22)
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Angeleska, Aleksandra
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Koceva, Dushica
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Stojanovska Dimzoska, Biljana
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Stojovikj, Goran
The EU Regulation EC/555/2018 has foreseen implementation of monitoring program for selected pesticide residues in bovine milk, aimed for further dietary exposure assessment. Therefore, since 2019 the required pesticide substances were introduced into the National Residue Control Program for animal origin food in North Macedonia. For this purpose, UHPLC-MS/MS method was optimized and validated after modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) sample preparation. The MS/MS method was optimized for 19 pesticide substances and metabolites: carbaryl, carbofuran, fenvalerate, indoxacarb (carbamate pesticides), cypermethrin, deltamethrin, bifenthrin permethrin (pyrethroids), malathion, parathion, diazinone, dichlorvos, chlorpyriphos, chlorpyriphosmethyl, pyrimiphos-methyl (organophosphates), famoxadone, fipronil, including metabolites fipronil sulfone, fipronil sulfide. For each compound the two most sensitive MRM transitions were selected for further determination. Analysis was performed on Waters UHPLC-MS/MS system consisted of H-class UHPLC and Xevo TQ-S micro triple quadrupole detector, in ESI+ and ESI- mode. Chromatographic separation was performed on C18 column with 100 mm length and 1.7 μm particle diameter, using gradient elution with water and methanol, both modified with formic acid and ammonium formate (0.1 % v/v and 5 mmol/L, respectively), at flow rate of 0.45 mL/min. The optimized method was validated according to DG SANTE Document 2017/11813. Validation parameters were linearity, limit of quantification (LOQ), precision, accuracy, and matrix effect. The determined LOQs from the concentration level at which S/N ratio was higher than 1:10, were in the range 1.0 – 8.3 μg/L, and were equal or below the MRL values for the pesticides of interest. Linearity was determined in the range 1-100 μg/L, obtaining five level calibration curves with correlation coefficients ≥0.99 for all tested analytes. Method precision was tested at two concentration levels - 10 and 50 μg/kg), except for carbofuran, for which the target levels were 1 and 10 μg/kg. The calculated relative standard deviation (RSD) ranged from 6.3 to 15.5 %. The method accuracy, estimated from the recovery at two concentration levels, was in the range 73.8 – 107.3 %. Matrix effect did not have significant influence on the analyte signal suppression or enhancement, thus solvent standards could be used for calibration. The method performance characteristics were satisfactory according to the SANTE document requirements (LOQ ≤ MRL, precision ≤20 %, and recovery 70-120 %). With this, it was proven that the proposed method was suitable for analysis of the defined scope of substances, even for pyrethroids, for which gas chromatography was considered to be a more appropriate analysis technique.
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Determination of heavy metals and radionuclides in animal feeds of plant origin.
(Agricultural University of Tirana, 2021-11-03)
Angeleska, Aleksandra
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Koceva, Dusica
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COMPARISON OF EFFICIENCY OF TWO TYPES SPE COLUMNS FOR DETECTION OF BETA AGONISTS IN LIVER WITH LC-MS/MS METHOD
(Faculty of Veterinary Medicine - Skopje, 2024-09-22)
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Jovanov, Stefan
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Angeleska, Aleksandra
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Beta-agonists are a large group of chemical compounds that can be used as drugs to treat bronchial asthma and other pulmonary diseases, due to their spasmolytic properties. Moreover, they are use as tocolytics and heart tonics. Beta-agonists can be illegally used in meat producing animals to accelerate growth and increase muscle mass, thereby increasing total red meat yield. Consumption of meat from treated animals incur a risk to human health, because the residues from beta agonists accumulate and persist in animal tissues. Due to adverse side effects in human, the Commission of European Communities has banned the use of these compounds in slaughter animals. Тhere are various extraction methods for the analysis of beta agonists. The aim of this study was to compare the efficiency of elution procedure of ten beta agonists from liver with two types of solid-phase extraction (SPE) columns. The sample preparation procedure includes homogenization of liver samples, double extraction with phosphate buffer, enzymatic hydrolysis with β-glucoronidasa/aril sulfatase from Helix pomatia and solid phase extraction with two types of SPE columns: Discovery® DSC-MCAX (300 mg, 6 ml) and Strata Screen-C (500 mg, 6 ml). The analyses were performed with liquid chromatography tandem mass spectrometry (LC-MS/MS). The validation of the method was done according to the criteria established in Commission Decision 2002/657. Accuracy (recovery) and precision of the method were used for comparison of the efficiency of the proposed SPE columns. The recovery of the method using DSC MCAX columns ranges from 75.20 % to 109.4 %. A higher recovery can be observed with Strata Screen-C for some β-agonists. For clenbuterol at spiking levels of 0.25 and 0.75 ng/g, the recoveries were 129.0 % and 130.61 %, respectively, while for terbutaline at the spiking levels of 0.25 and 0.5 ng/g, the recoveries were 244.80 % and 275.76 %, respectively. Zilpaterol was not detected using Strata Screen-C columns. The coefficient of variation ranges from 3.43 % to 15.73 % (DSC-MCAX columns) and from 4.07% to 33.57 % (Strata Screen-C). The difference in the efficiency of the two types of columns is a result of the phases they contain. DSC-MCAX columns contain C8 (octyl), while Strata Screen-C columns contain C18 (octadecyl) phase. In the elution of samples, the C8 phase does not retain all analytes of interest. According to the obtained results DSC-MCAX columns fulfil the criteria, while Strata Screen-C columns don’t meet the criteria established in the 2002/657/EC.

Dimitrieska Stojkovikj, Elizabeta

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