Biocidal products are substances or mixtures of several substances, used to combat harmful organisms for human or animal health. Substances with antibacterial effects include quaternary ammonium salts, such as benzalkonium chloride (BAC), didecyl chloride (DDAC), etc. Benzalkonium chloride (BAC) is a compound of the class of quaternary ammonium compounds (QAC) used as a cationic surfactant in personal hygiene, cosmetic and skin disinfection products [1]. BAC is a mixture of alkylbenzyldimethylammonium chlorides [C6H5CH2N(CH3)2RCl], in which R = C12, C14, C16, C18 are the main compounds, and the antibacterial effects being given by the alkyl chain length and the quaternary ammonium groups [1,2].In this study we compare two methods of analysis for quantitative determination: chemical titration [3] and liquid chromatography (HPLC-UV) [4]. Chemical titration is an iodometric method in a strongly acidic medium, in which the 0.05M potassium iodate solution is used as titrant (titration with extracted end point) [3]. HPLC determinations were performed using an Agilent 1100 Series HPLC, equipped with a binary pump, a degasser, an autosampler and a spectrophotometric detector in UV-Vis, and Agilent Chemstation software was used for data acquisition and analysis. Chromatographic parameters were injection volume, 10 μL; analysis time, 25 min; a Zorbax Eclipse XDB-C18 column (5 μm, 4.6 mm × 150 mm); and flow rate, 1.5 mL/min, isocratic conditions 20:80 A:B (v/v), where A = 0.4 M/L NaCl solution and B = methanol [4]. BAC monitoring was performed at a wavelength of 210 nm with the help of a UV-Vis spectrophotometric detector. The identification was performed by comparing the retention time of the analyzed compound with the retention time of the standard solution. Confirmation of the presence of BAC alkylic homologues, prior to quantitative determination, was performed using the mass spectrometry detection technique with a time-of-flight detector (TOF LC/MS).As a measure of selectivity, for calculating the degree of recovery, the standard method of addition was applied. As a measure of selectivity, the degree of recovery determined by the standard addition method was used. For the titrimetric method we studied the influence of the presence of possible interferences different from those of the QAC class, such as ethyl and isopropyl alcohols, glutaraldehyde, non-ionic surfactants, stabilizers, etc. Regarding the HPLC-UV method, we were particularly interested in the selectivity with respect to other quaternary ammonium salts, such as didecyldimethylammonium chloride (DDAC) and cationic surfactants.

In this work, Sb (III) adsorption on oxidized exfoliated graphite nanoplatelets (ox-xGnP) was evaluated for the first time, to the best of our knowledge. The ox-xGnP were characterized by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), Brunauer–Emmet–Teller (BET) analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM) equipped with energy-dispersive X-ray spectroscopy (EDX), and Zeta potential analysis. The adsorption parameters, such as pH and contact time, were optimized, and the best adsorption capacity obtained was 8.91 mg g−1 at pH = 7.0, 1.0 mg ox-xGnP/100 mL solution, T = 293 K, 1.0 mg L−1, Sb (III), 25 min contact time. The best correlation of the kinetic data was described by a pseudo-first-order kinetic model, with R2 = 0.999. The adsorption isotherms of Sb (III) onto ox-xGnP were best described by the Langmuir isotherm model. The thermodynamic parameters showed that the adsorption process was exothermic and spontaneous.

Plant biostimulants, an emerging class of agricultural inputs, are complex products. The reproducibility of their specific action on plant metabolism and plant physiology, which lead to an enhanced nutrient use efficiency, stress tolerance and edible yield quality, is still a challenge. Development of quality insurance systems for plant biostimulants need complex investigation based on adapted analytical, physico-chemical and chemical methods. The objective of this work was to characterize commercial humate biostimulants through different analytical techniques (Fourier transform infrared spectroscopy - FTIR, thermogravimetric analysis- TGA) and to evaluate their textural and chemical (pH, C, N, humic acids, inorganic components) parameters. The first derivative curve from TG analysis showed decomposition of different compounds, classified according to the results obtained by FTIR. The humic substances determined by TGA method was comparable with the results obtained by gravimetric reference method. The inductively coupled plasma-optical emission spectrometry (ICP-OES) technique was applied to determine the inorganic elements either from the production process of humate or from raw materials, as well as for the control of humate in terms of requirements for safety and quality. Their complementary properties obtaining through different analytical techniques provide essential information on the chemical characteristics of the humate plant biostimulant formulations.

In the present work, it was developed a simple, cheap and quick method for Sb determination from mineral water, using ICP-OES, using two different calibration proceedings: calibration curve method (CCM) and standard additions method (SAM). On the studied concentration range, the parameters such as the calibration curve slope, linearity expressed through correlation coefficient r = 0.9992, limits of detection LoD = 0.67 �g L-1 and quantification LoQ = 2.01 �g L-1, the standard deviation of repeatability of 0.25 �g L-1, the accuracy of 0.16 �g L-1 satisfy the performance criteria. The value of extended uncertainty with a confidence level of 95 % (k = 2), is 1.0 �g L-1 obtained for Sb content of 4.10 �g L-1. The mineral waters were analyzed also by the addition standard method. One of the advantages of this method is to eliminate interference from the matrix. By the method of standard additions, the detection limit decreased from LoD=0.67 �g L-1 to 0.16 �gL-1.

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