We introduce a novel approach in simple and highly sensitive fluorometric determination of ammonium nitrogen. The proposed method is based on a fluorescence derivatization with benzyl chloride. The benzyl chloride was converted to a new fluorescent derivative by reaction with ammonium ion (NH4+) in the presence of sodium bicarbonate. The excitation and emission wavelengths were 258 and 284 nm, respectively. The effects of benzyl chloride concentration, sodium bicarbonate concentration, reaction temperature and time, and hydrochloric acid concentration were studied in detail. Under the optimal conditions of the experiment, the linear range for determination of ammonium nitrogen was 0.01-0.60 mg L-1, and the detection limit was 0.008 mg L-1. Relative standard deviation of eleven measurements for 0.40 mg L-1 NH4+-N was 2.6%. The method was successfully applied to the determination of ammonium nitrogen concentration in different water samples. The mechanism of the derivatization was further confirmed by Fourier transform infrared (FTIR) spectra.

A simplified method based on ratio derivative ultraviolet spectrometry for simultaneous determination of bisphenol A (BPA) and bisphenol S (BPS) in environmental water is presented. The method provides a direct analysis of the samples without tedious sample preparation. In this method, the overlapping spectra of BPA and BPS were well resolved using the first derivative (Δλ = 1 nm) of the ratio of their absorption spectra. Measurements of absorbance were performed at wavelengths of 229.5 nm and 245.5 nm for BPA and BPS, respectively, using the ratio derivative spectrum method. Beer's law was followed in the concentration range of 8.8 X 10-7-2.2 X 10-4 mol dm-3 for BPA and 1.4 X 10-6-1.0 X 10-4 mol dm-3 for BPS. The limits of detection were 3.5 X -7 mol dm-3 for BPA and 4.4 X 10 7 mol dm ³ for BPS. Their 5:1 to 1:5 mixtures were resolved with recoveries between 90.5 % and 100.9 % for BPA and between 93.8 % and 101.1 % for BPS. The method was satisfactorily applied to the simultaneous determination of BPA and BPS in environmental water samples.

Um eletrodo de partículas compósitas de carbono modificado com níquel níquel (Ni/AC) foi preparado por deposição sem aplicação de corrente com pré-tratamento livre de paládio para melhorar o desempenho eletrocatalítico do eletrodo compósito em uma cela eletroquímica. As condições de preparo do eletrodo de partículas compósitas de Ni/AC foram otimizadas usando-se como índice a razão do descoramento de uma solução do corante alaranjado de metila. Os eletrodos de partículas compósitas foram caracterizados por microscopia eletrônica de varredura, difração de raios-X e análises por espectrometria de energia dispersiva. Os desempenhos eletrocatalíticos do eletrodo de partículas Ni/AC foram examinados por meio de vários parâmetros, incluindo dosagem do eletrodo de partículas, concentração de sulfato de sódio, tensão da cela e tempo de eletrólise. Os resultados foram comparados com os de eletrodo de partículas convencionais de carbono ativado (AC). Esses resultados indicaram ser possível preparar um eletrodo de partículas compósitas de Ni/AC por revestimento electroless com pré-tratamento sem paládio. As condições ótimas de preparo do eletrodo Ni/AC eram 40 g L-1 NiSO4·6H2O, 27 g L-1 NaH2PO2·H2O, 50 °C temperatura de revestimento, e 20 min tempo de revestimento. O desempenho eletrocatalítico do eletrodo Ni/AC foi superior ao do eletrodo AC sob as mesmas condições de eletrólise. A constante de velocidade de oxidação do alaranjado de metila pelo eletrodo Ni/AC foi 1,5 vezes maior que o do eletrodo AC.

A nickel-loaded activated carbon (Ni/AC) composite particle electrode was prepared by electroless deposition with palladium-free pretreatment to improve the electrocatalytic performance of a composite particle electrode in a three-dimensional electrode cell. The preparation conditions of the Ni/AC particle electrode were optimized using the decolorization ratio of methyl orange dye solution as an index. The composite particle electrodes were characterized by scanning electron microscopy, X-ray diffraction, and energy dispersive spectrometry analyses. The electrocatalytic performances of the Ni/AC particle electrode were examined by a series of parameters, including particle electrode dose, sodium sulfate concentration, cell voltage, and electrolysis time. The results were compared with those of conventional activated carbon (AC) particle electrode. These results indicated the feasibility of preparing a Ni/AC composite particle electrode by electroless plating with non-palladium pretreatment. The optimal conditions for preparing the Ni/AC electrode were 40 g L-1 NiSO4·6H2O, 27 g L-1 NaH2PO2·H2O, 50 °C plating temperature, and 20 min plating time. The electrocatalytic performance of Ni/AC electrode was superior to that of AC electrode under the same electrolysis conditions. The rate constant of the Ni/AC electrode electrochemical oxidation of methyl orange was 1.5 times larger than that of AC electrode.