New accurate, precise, and sensitive spectrophotometric method were developed for the assay of L-ascorbic acid in pharmaceutical preparations. The determination of L-ascorbic acid was based on its oxidation by potassium peroxydisulfate in the presence of Ag(I) as a catalyst. The molar absorptivity of the proposed method was found to be 8.61 · 103 L mol-1 cm-1 at 248 nm. Beer's law was obeyed in the concentration range of 0.46–20.0 μg mL–1. Other compounds commonly found in vitamin C and multivitamin products did not interfere with the determination of L-ascorbic acid. The proposed method was successfully applied for the determination of L-ascorbic acid in pharmaceutical formulations. The results obtained with the proposed method showed good agreement with those given by the titrimetric method using iodine.

In addition to soda, the Solway production process yields large amounts of waste sludge that contains a high percentage of CaCO3 and Ca(OH)2. In this paper, solid waste sludge from a soda factory in Bosnia and Herzegovina of a certain granulation was used to remove metal ions from the binary system initial concentrations of 500 mg/L. The research results showed that the precipitation efficiency for the binary system Cu - Ni was 99.810% at a pH of 11.42 for Cu2+ and 99.896% for Ni2+ at a pH of 10.86, while for the binary system Pb - Zn it was 99.84% at the same pH value of 10.64. This research has shown that it is very difficult to separate and remove metal precipitation from binary systems because the optimal pH for one metal does not correspond to another metal.

: The hydroxide precipitation method, using NaOH as a precipitant agent, was conducted to treat synthetic monocomponent and two-component water solutions of Pb 2+ and Zn 2+ with initial concentrations of 50 and 500 mg/l of each metal. The effect of pH and initial concentration of lead and zinc ions on their removal were investigated. The precipitation experiments were carried out by batch method that involves the mixing of NaOH with solutions containing metal ions to occur nucleation, solid growth and subsequent separation of precipitates from solution by filtration. The results showed that the removal efficiency was increased by increasing of pH and initial concentration of metal ions in their water solutions. Hydroxide precipitation method using NaOH is an ef-ficient technique for the removal of lead and zinc ions from their monocomponent and two-component water solutions of different concentrations, with maximum removal efficiency in the pH range of 10.32 to 11.39.

Two new, accurate, precise, and sensitive spectrophotometric methods were developed for the assay of L-ascorbic acid in pharmaceutical preparations. The determination of L-ascorbic acid was based on its oxidation by potassium peroxymonosulfate (method A) and hydrogen peroxide in the presence of Cu(II) as a catalyst (method B). The molar absorptivities were found to be 1.48×10 and 1.06×10 L mol cm for methods A and B, respectively. Beer's law was obeyed in the concentration range of 0.65–11.20 μg mL for method A and 0.51–16.00 μg mL for method B. Other compounds commonly found in vitamin C and multivitamin products did not interfere with the determination of L-ascorbic acid.. The proposed methods were successfully applied for the determination of L-ascorbic acid in pharmaceutical formulations. The results obtained with the proposed methods showed good agreement with those given by the titrimetric method using iodine.

Wheat bread was prepared by replacing 15%, 30% and 40% of white wheat flour with wholegrain buckwheat flour. Total phenols content (Folin–Ciocalteu method) and antioxidant activity (FRAP) of buckwheat flour enriched wheat bread samples and flour mixtures were analysed and compared with wheat bread and wheat flour (control samples). Wholegrain buckwheat flour (17.91 mg GA/L extract) contained higher total phenols than wheat flour (9.11 mg GA/L extract). The incorporation of buckwheat flour in bread samples increased the total phenols content from 7.46 (mg GA/L extract) to 10.13 (mg GA/L extract), and antioxidant activity from 231.45 (µmol Fe 2+ /L extract) to 368.45 (µmol Fe 2+ /L extract). Total phenols content decreased during the baking process, while the antioxidant activity increased. Bread samples with 15%, 30% and 40% of wholegrain buckwheat flour showed lower L values of crust and crumb colour compared to the control sample.

A simple and highly sensitive direct spectrophotometric method was developed for the determination of L-ascorbic acid. Sodium oxalate (0,0056 mol/dm) was used to stabilize L-ascorbic acid in aqueous medium. The molar absorptivity of the proposed method, which does not require an extraction procedure, was 1.42x10 dm mol cm at 266 nm. Beer’s law was obeyed in the concentration range of 0.857 – 12.0 μg ascorbic acid/cm. The relative standard deviation was 0.81 % for the determination of 8.0 μg ascorbic acid/cm (n = 7). The substances commonly found in vitamin C products do not interfere with the determination of ascorbic acid. Other vitamins, Ca(II) and benzoate interfere. The proposed procedure was successfully applied to the determination of ascorbic acid in pure form and vitamin C preparations. Index Term-Spectrophotometry, L-ascorbic acid, sodium oxalate, stabilizer.

Greenhouse production is getting more and more important in the production of food, particularly if it is considered as ecological production. Having it in mind, it is very important to provide continual control of quality such products. This work is aimed to present the monitoring of the content of heavy metals in tomato, grown in greenhouse conditions. In products grown in greenhouses, heavy metals can be present from different sources such as soil, pesticides, etc. This paper considers the importance of continual monitoring of presence of heavy metals, such as cadmium, lead, copper, iron, etc. in tomato, taking in consideration their bioavailability to plants in acid and basic soil conditions. Obtained results in this work could be used as the base for establishing the model for continual monitoring of contaminants in food, particularly those that are present in very small concentrations, such as lead, cadmium, etc.