[Atomic absorption determination of heavy metals in the milk and meat from several regions of Bulgaria]. / Atomno-absorbtsionno opredeliane na tezhki metali v mliako i meso ot niakoi raioni na stranata.

By AAS after wet digestion of the samples the results were 20% higher (for milk) and 41% higher (for meat) in comparison with dry coshing. Cow and ewe milk and pork, beef, and mutton were sampled in six regions of the country and were studied with regard to residual amounts of four trace elements. Highest appeared to be the content of zinc, and lowest--the content of cadmium. The results were compared with data of workers abroad. On the basis of results of personal investigations and studies of authors abroad a temporary standard norm for the content of cadmium was fixed at 0.15 mg/kg, and for that of lead--at 0.40 mg/kg. A system of technologic and sanitary-and-technical measures are suggested (higher chimneys, catching installations, filters) for the regions of Plovdiv and Kurjali with a view to lowering the concentration of toxic elements and avoiding the pollution of the environment.

[Pesticide residues in honey]. / Ostatuchni kolichestva pestitsidi v pchelen med.

Investigated were a total of 40 samples of flower honey from seven regions of the country (the districts of Mihailovgrad, Gorna Oryahovitsa, Turgovishte, Plovdiv, Pazarjik, Sliven, and Byala Slatina). In 20 per cent of the samples there were traces of the phosphororganic pesticides trichlorfon and DDVF, and in 32 per cent - traces of chlororganic insecticides - HChCH and DDE. The studies made use of the agar diffusion, thin layer chromatography, and gas chromatography methods. It was established that honey was a product that was negligibly contaminated with pesticides. The residual amounts found were minimal (0.0002 to 0.00060 ppm) and were within the range of the admissible Bulgarian and international standards concerning the respective pesticides in food products. These amounts were found to correspond to the values established by other authors.

[Determination of benzoic acid and its salts in food products of animal origin]. / Opredeliane na benzoenata kiselina i solite i v khranitelni produkti ot zhivotinski proizkhod.

A modification of the method for determining benzoic acid and its salts by water-vapour distillation and extraction of the biological material conservant and its titrimetrical determination is proposed. The thin layer chromatography method (TLC) is used parallelly for the identification of the conservant. The advantage of the proposed method consists in that the same distiller is used for quantitative titrimetrical determination and for TLC assessment. The method possesses high sensitivity 1 gamma in TLC scoring and 0.1 mg in titrimetric determination. It is applied for the determination of conservants in various fish assortments, canned fish and roe.

[Determination of sorbic acid, its salts and salicylic acid in food products of animal origin]. / Opredeliane na sorbinovata kiselina, neinite soli i salitsilovata kiselina v khranitelni produkti ot zhivotinski proizkhod.

A foreign method for quantitative assay of sorbic acid and natrium sorbate in food stuff of plant origin was applied by the authors for food stuffs of animal origin. The conservant of the food stuff was isolated by water vapour distillation. Sorbic acid and natrium sorbate assay was performed on part of the distillate colorimetrically at wave length lambda--532 nm. The method proved highly sensitive (2 gammas and 94% reproduction). It can be used in conservant assay of various fish assortments, canned food, roe and some types of cheese. A qualitative method for proving the presence of salicylic acid is proposed, using water vapour distillation of the biological material. Part of the distillate produced is treated directly by 1% ferriammonium sulfate water solution. A violet tint of the solution proves the presence of salicylic acid in the product studied.

[Cyclophosphamide content in the meat and milk after a single application to sheep]. / Zadurzhane na tsiklofosfamida v meso i mliako sled ednokratno prilagane pri ovtse.

Investigated were two groups of 10 Merino sheep each. The test group were given orally cyclophosphamide, singly, at the rate of 25 mg/kg, while the controls of the second group were not treated but were kept under the same conditions. Both milk and meat of the two groups were investigated by thin layer chromatography and gas chromatography on the 1st, 4th, 9th, 14th, 23rd, and 30th day following the introduction of cyclophosphamide. The results obtained by gas chromatography showed that it was not until the fourth day that there were two metabolites of the compound in milk only. On the 9th day the same were established in the milk and meat samples in a maximum concentration, the excretion from the body of the treated animals starting as early as the 14th day. By the 23rd day there were traces only, and after the 30th they were no longer established. Thin-layer chromatography showed that the two metabolites were found in approximately equal amounts up to the 14th day following treatment, and were fully excreted after the third week. Therefore, the full elimination of cyclophosphamide metabolites from the milk and meat of sheep treated with it at the rate cited takes place in about four weeks.

[Organochlorine pesticide residues in the eggs from poultry raising farms]. / Ostatuchni kolichestva ot khlororganichni pestitsidi v iaitsa ot ptitsevudnite stopanstva.

A gas chromatography method was employed to investigate the residual amounts of chlororganic pesticides in a total of 37 average batch samples of eggs taken from 18 large poultry farms. More than two thirds (from 70.3 to 75.6 per cent) of the samples were shown to be free of p'p' DDE, p'p' DDT, and dieldrin, and more than one third (from 35.1 to 43.2 per cent)--of alfa and gamma hexachloran, heptachlor and heptachlorepoxide. In 88,4 per cent of the samples there were found residues of p'p' TDE (up to 0.061 ppm). The egg content showed trace amounts of DDT and metabolites--0.025 ppm, alfa and gamma hexacloran--0.016 ppm, heptachlor--0.006 ppm, heptachlorepoxide--0.01 ppm, and dieldrin--0.002 ppm. These amounts were much lower than the tolerance evaluations postulated by FAO/OMS and those accepted in other countries.

[Thin-layer chromatographic determination of coumarin derivatives]. / Tunkosloinokhromatografsko opredeliane na niakoi proizvodni na kumarina.

Described is a thin-layer chromatography method for the demonstration and identification of the cumarin derivatives cumaphos and warfarin. Tested were five solvents and six developers. Best results were obtained by means of Silica gel plates, the toluol-aceton solvent (85:15), and the developer of a diazosalt 0.4% in an alcohol 20% sodiumhydroxide. Warfarin and cumaphos are demonstrated with the appearance of yellow, resp. orange spots on a white background, the RF values being 0.37 and 0.85, and sensitivity as regards warfarin 0.5 microgram and cumaphos 0.2 microgram.

[Thin-layer chromatographic demonstration of the herbicide zenkor]. / Tunkosloinokhromatografsko dokazvane na kherbitsida zenkor

Established were the thin-layer chromatography conditions for the demonstration of the herbicide Zenkor as a pure substance and a preparation. Comparative experiments were carried out applying Thomson and Stanley's thin-layer chromatography conditions and the authors' personal ones. Most adequate proved to be the following conditions: sorbent-Kieselgel 60F 254 (Merck); solvent -- chloroform: 1,4-dioxan (9:1); developer -- ultraviolet light (authors' technique). Essential with this method is the preliminary (prior to apply the pure substances on the thin-layer chromatographic plaque) moving of the plaque in the indicated mobile phase (authors' technique). Under these thin-layer chromatography conditions work is made feasible and the method is fast and simple, achieving high sensitivity -- 0.5 mug Zenkor.

[Determination of the concentration of copper, lead, cadmium and zinc in milk by atomic absorption spectrophotometry]. / Opredeliane sudurzhanieto na mad, olovo, kadmii i tsink v mliako po metoda na atomno-absorbtsionnata spektrofotometriia

Developed was an atom-absorption method for determining microconcentrations of copper, lead, cadmium, and zink in milk originating from various regions of this country. The study was carried out by means of an atom-absorption spectrophotometer AA-5. Established were the optimal conditions for determining the trace elements reaching the following values of susceptibility: for copper--0.04; for lead--0.11; for cadmium--0.001; and for zinc--0.009 mg/cu.cm, with an allowance of 5%. The results obtained are discussed and statistically processed. Literature data are comparatively studied reflecting the amounts of these elements in milk as found in this country and abroad. Such data will be made use of in the elaboration of Bulgarian reference tables necessary for establishing various regimes and norms concerning the food products offered in children creches, hospitals, canteens, etc.