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The retention characteristics of five stationary phases were tested by using a selection of 5'-mononucleotides and nucleosides with the aim to develop a simple, rapid and sensitive reversed-phase liquid chromatography method without ion-pair reagent usage. The method was optimized by changes in temperature, pH and ionic strength on a column showing a superior performance. The mobile phase consisted of a mixture of 0.05 M phosphate buffer and methanol, delivered at a flow rate of 0.4 mL/min and based on a gradient program. UV detection was used at a 254 nm wavelength. The method was validated for a quantitative analysis of 5'-mononucleotides and nucleosides in wild edible mushrooms. For all nucleosides and nucleotides, the LOD and LOQ were less than 0.02 and 0.07 microg/mL, respectively. Validation parameters yielded recovery rates between 68.6 and 98.2%, with a precision expressed as a relative standard deviation of 7.6-15.3%. The content of 5'-mononucleotides and nucleosides was determined for 10 samples of wild edible mushrooms found in Croatia and, accordingly, the equivalent umami concentrations were calculated.

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Organochlorine Pesticides in Freshwater Fish from the Zagreb AreaThe aim of this study was to determine the level of organochlorine pesticides in freshwater fish from the Zagreb area, Croatia. The study included 215 freshwater fish samples from three sites: the Sava River, Lake Jarun, and five fishponds from the Zagreb surroundings. Organochlorine pesticides DDT and derivates, HCH, HCB, lindane, aldrin, dieldrin, endrin, heptachlor with epoxide, and methoxychlor were determined using the GC-ECD method. The determined amounts of organochlorine pesticides were within allowed concentration limits in all analysed fish samples. Median values ranged from below the detection limit of 0.01 μg kg-1 for dieldrin and metoxychlor to 2.00 μg kg-1 for DDT in the Cyprinidae fish family from the Sava River, Zagreb sampling site (group 1).This study has confirmed pesticide persistence in the overall ecosystem in our country despite the ban of some thirty years ago, like in many other parts of the world.

The sulfonamides (SAs) are stable chemotherapeutics used against the bacterial disease affecting bees, known as American foulbrood (Bacillus larvae), so their residues could appear in the honey of treated bees. Their presence at a concentration above the limit value could be a potential danger to human health. Therefore, a simple, rapid, and reliable method for determination of 11 available SAs in honey was optimized. The samples were homogenized and cleaned with extraction on solid phase by means of Chromabond C18 end-capped cartridge followed by LC/MS analyses. A detection limit of 25 microg/kg was achieved for all analytes. The repeatability of the method was proven and the optimal parameters for temperature and pH of the mobile phase and acetic buffer, respectively, were determined. In this study, 20 samples of domestic honey were included. Six of the analyzed samples were positive, but all results were below the Croatian permissible limit value (100 microg/kg).