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Original Scientific ArticleMac Vet Rev 2016; 39 (1): [65][66][67][68][69][70][71][72][73][74][75][76] Two simple, sensitive, selective, precise, and accurate methods for determination of trimethoprim in different sulfonamide formulations intended for use in human and veterinary medicine were optimized and validated. The methods are based on the trimethoprim reaction with bromcresol green (BCG) and 2,4-dinitro-1-fl uorobenzene (DNFB). As extraction solvents we used 10 % N,N-dimethylacetamide in methanol and acetone for both methods, respectively. The colored products are quantified applying visible spectrophotometry at their corresponding absorption maxima. The methods were validated for linearity, sensitivity, accuracy, and precision. We tested the method applicability on four different medicinal products in tablet and powder forms containing sulfametrole and sulfamethoxazole in combination with trimethoprim. The results revealed that both methods are equally accurate with recoveries within the range 95-105 %. The obtained between-day precision for both methods, when applied on four different medicinal products, was within in the range 1.08-3.20 %. By applying the F-statistical test (P<0.05), it was concluded that for three medicinal products tested both methods are applicable with statistically insignificant difference in precision. The optimized and validated BCG and DNFB methods could find application in routine quality control of trimethoprim in various formulation forms, at different concentration levels, and in combination with different sulfonamides.

Background: Aflatoxins (AFs), as secondary metabolites, are mainly produced by fungi of Aspergillus genus. The determination of contamination rate, dietary exposure, and health risk assessment for aflatoxin M1 (AFM1) was conducted aimed to estimate potential health risks for the population of North Macedonia. Methods: A total of 974 dairy samples, including 404 Ultra-High Temperature (UHT) milk, 291 ice cream, 178 yogurt, and 101 cheese were collected from the markets in North Macedonia. Analysis of AFM1 was done using Enzyme-Linked Immunosorbent Assay and High-Performance Liquid Chromatography with Fluorescence Detection. Results: The AFM1 incidence was highest in yogurt samples (93.8%) and lowest in UHT milk samples (67.8%). AFM1 concentrations were 49.1±68.4, 30.9±30.0, 35.1±40.4, and 40.1±90.1 ng/kg for UHT milk, ice cream, yogurt, and cheese samples, respectively. The Estimated Daily Intake (EDI) for the average population and high consumers (upper bound; samples with AFM1<Limit of Detection (LOD) were 0.150 and 0.456 ng/kg body weight (bw)/day, respectively. The Hazard Index (HI), Margin of Exposure (MoE), and the fraction of Hepatocarcinoma (HCC) cases per 100,000 inhabitants for the average population reached values of 0.33, 8533, and 0.004, respectively. Conclusion: To our best knowledge, this is the first report of dietary exposure and risk assessment of AFM1 in dairy products of North Macedonia, revealing a potential risk of AFM1 in population of this country.

The possible presence of pesticide residues in honey has impelled the need for setting up monitoring programs to determine the proper assessment of human exposure to pesticides. This paper describes an effective multi-class method using a modified QuEChERS sample preparation for detection and quantification of 18 pesticides with Ultra-high-performance liquid chromatography (UHPLC) -tandem quadrupole mass spectrometry. The method was validated according to the requirements laid down in DG SANCO 12571/2013 document. Levels of detection and quantification were lower than the established MRLs, the obtained precision was better than 20 %, and the recovery values were between 74.4 and 104.1 %. Fifty honey samples within the national monitoring program were collected from August to November, 2014 and tested for presence of carbaryl, carbofuran, fenvalerate, cypermethrin, deltamethrin, permethrin, bifenthrin, amitraz, coumaphos, bromopropylate, dichlorvos, diazinone, malathion, parathion, dimethoate, omethoate, methomyl and thiametoxam. Trace levels of methomyl, diazinone, bromopropylate and fenvalerate were detected somewhat above the reporting level for these pesticides (10 µg/kg). This contamination indicates on existing of possible moderate cross-contamination during pollen and nectar collection by bees, and residues of substances used in beekeeping. Although traces of pesticides were found in 16 of the samples tested (32 %), the levels found did not pose increased toxicological risk for the population.

The use of β-agonists in livestock production is prohibited in many countries because the residues of β-agonists in food pose a potential risk to human health. The present work describes the development and validation of the LC-MS/MS method for detection of ten β-agonists in bovine urine according to Commission Decision 2002/657/EC requirements. Linearity of the method resulted with coefficient of correlation >0.990. The decision limits (CCα) ranged from 0.127 ng/mL to 0.646 ng/mL, and the detection capability (CCβ) resulted in the range 0.140 ng/mL to 0.739 ng/mL. The observed recoveries in the fortified bovine urine samples were satisfactory at every fortification level with values from 73.67% to 118.80%. The coefficient of variation (CV, %) at three fortification levels for each β-agonist was in complete agreement with the requirements from Commission Decision 2002/657/EC. The CV for intraday precision varied from 1.619% to 15.472% and the CV for interday precision varied from 2.695% to 10.441%. From the obtained validation results the proposed method is an appropriate method for determination of β-agonists in bovine urine.

Liquid chromatography with fluorescence detection using immunoaffinity column clean-up was a method described for determination of aflatoxins (AFB1, AFB2, AFG1 and AFG2) in peanuts and peanut based products. The validation of the procedure was performed. Good coefficient of correlation was found for all aflatoxins in the range of 0.9993-0.9999. Limit of detection (LOD) and limit of quantification (LOQ) ranged from 0.003-0.005 mg/kg and 0.009-0.023 mg/kg, respectively, which was acceptable. The mean recovery for total aflatoxins was 88.21%. The method also showed acceptable precision values in the range of 0.171-2.626% at proposed concentration levels for all four aflatoxins. RSDR values (within laboratory reproducibility) calculated from the results showed good correlation between two analysts for all aflatoxins and they ranged from 4.93-11.87%. The developed method was applied for the determination of aflatoxins in 27 samples of peanuts and peanut based products. The results showed that 21 peanut samples (77.7%) were below LOD of the method. Three samples had positive results over the MRL. There was one extreme value recorded for the total aflatoxins in peanut (289.2 mg/kg) and two peanut based products, peanut snack and peanut, with total content of aflatoxins being 16.3 mg/kg and 8.0 mg/kg, respectively. The obtained results demonstrated that the procedure was suitable for the de­termination of aflatoxins in peanuts and peanut based products and it could be implemented for the routine analysis

A b s t r a c t: Concentration of natural radionuclides in soil and plants are crucial parameters for defining the level of contamination of the environment. The samples for analysis were collected from the 14 localities of the surrounding of Skopje, of cultivated and uncultivated soil. The specific activity of radionuclides 232 Th, 226 Ra and 40 K are determined by gamma spectrometry. The analysis results show that the mean value of 232 Th specific activity in cultivated soil was 43.74 ± 4.99 Bq•kg 1 , while in uncultivated soil it was 35.70 ± 5.65 Bq•kg 1 . The 226 Ra specific activity had a mean value of 34.09 ± 6.53 Bq•kg 1 and 28.30 ± 5.54 Bq•kg 1 in cultivated and uncultivated soil, respectively. The specific activity of 40 from all localities was higher than the one of 232 Th and 226 Ra, and in cultivated soil the mean value was 608.12 ± 70.43 Bq•kg 1 , while in uncultivated soil it was 506.54 ± 59.96 Bq•kg 1 . From the same locations corn samples were also collected for analysis. Concentration of natural radionuclides in corn is lower then referent values. From the results ttransfer factor (TF) of natural radionuclides from soil to corn was calculated.

The protonation of ten aliphatic amides in sulfuric acid media was studied by UV spectroscopy. (-0.57, -0.29, -0.32 and 0.36, respectively), analogous acetamides were more basic than formamides. Applying the Hammett's equation, satisfactory correlation could be gained only for some formamides, the basicities of which increased linearly with the inductive effect of the electron donating groups. From Taft's approach, it can be concluded that the polar effect slightly dominates over the steric one. Excellent correlation between pK BH + and solvation parameters m* was achieved for formamide, dimethylformamide and diethylformamide. At half-and fullprotonation, better correlation was obtained for formamides than for acetamides.Keywords: UV spectroscopy; formamides; acetamides; protonation constants; Hammett-Taft correlations ОПРЕДЕЛУВАЊЕ НА КОНСТАНТИТЕ НА ПРОТОНИРАЊЕ И СТРУКТУРНИ КОРЕЛАЦИИ НА НЕКОИ ТЕРЦИЈАРНИ ФОРМАМИДИ И АЦЕТАМИДИ ВО СУЛФУРНА КИСЕЛИНА СО УЛТРАВИОЛЕТОВА СПЕКТРОСКОПИЈАПротонирањето на десет алифатични амиди во сулфурна киселина е проучувано со примена на ултравиолетова спектроскопија. Вредностите за pK BH+ и солватационите параметри се пресметани според методот на Yates и McClelland, методот на вишок на киселост и Bunnett-Olsen-овиот метод. Вредностите за pK BH + изнесуваат -1.44, -1.15, -0.80, -0.32, -1.13 и -0.80 за формамид, диметилформамид, диетилформамид, диизопропилформамид, диизобутилформамид и дибутилформамид, соодветно. Според вредностите на pK BH+ определени за ацетамид, диметилацетамид, диетилацетамид и диизопропилацетамид (-0.57, -0.29, -0.32 и 0.36, соодветно) аналогните ацетамиди се побазни од формамидите. Со примена на Hammett-овата равенка добиени се задоволителни резултати само за некои формамиди, чија базност линеарно расте со индуктивниот ефект на електронодонорната група. Од Taft-овскиот пристап може да се заклучи дека поларниот ефект е незначително поголем од стерниот. Постигната е одлична корелација помеѓу вредностите на pK BH + и солватационите параметри m* за формамид, диметилформамид и диетилформамид. Кај полу-и целосна протонација, подобра корелација е добиена за формамиди отколку за ацетамиди.Клучни зборови: UV спектроскопија; формамиди; ацетамиди; константи на протонирање; Hammett-Taft-овски корелации G. Stojković, E. Dimitrieska-Stojković, E. Popovski Maced. J. Chem. Chem. Eng. 34 (2), 255-265 (2015) 256