Selective Membrane Sensor for Aluminum Determination in Food Products, Real Samples and Standard Alloys

The study involves the fabrication of an aluminum liquid membrane sensor based on the association of aluminum ions with the cited reagent 2,9-dimethyl-4,11-diphenyl -1,5,8,12-tetraaza cyclote tradeca-1,4,8,11-tetraene [DDTCT]. The characteristics slope (58 mV), rapid and linear response for aluminum ion was displayed by the proposed sensor within the concentration range 2.5 × 10−7–1.5 × 10−1 M, the detection limit (1.6 × 10−7) M, the selectivity behavior toward some metal cations, the response time 10 s), lifetime (150 days), the effect of pH on the suggested electrode potential and the requisite analytical validations were examined. The suitable pH range was (5.0–8.0 ), in this range the proposed electrode response is independent of pH. The suggested electrode was applied to detect the aluminum ions concentration in food products, real samples and standard alloys. The resulting data by the suggested electrode were statistically analyzed, and compared with the previously reported aluminum ion-selective electrodes in the literature.

New mathematical method for detection of the metal-catalyzer traces on the modified electrodes surface

New mathematical approach for characterization of the measured voltammograms (VAGs) obtained for electrodes with catalytic response and modified by nanoparticles of gold (Au) and palladium (Pd) was applied. The cases with tracing concentrations of the electrodeposited catalyzer were considered, when the corresponding VAGs for the solutes containing catalyzer and background coincide practically with each other. Using the catalyzer electrode response of dopamine (DA) and new mathematical approach for description of the remnant current fluctuations, it was shown that becomes possible to extract a useful information from the measured VAGs because of increasing the limits of the signal/noise ratio. The fluctuations of the remnant currents are transformed into a specific “confidence tube” that is used for detection of the VAGs perturbations evoked by the presence of the analyte traces. Using the proposed mathematical method, it becomes possible to achieve the low boundary of the DA detection up to 10-8 M.

Investigating the Prospect of Copper-Histidine Complex Modified Gold Electrode for Histidine and Human Serum Albumin Recognition

Histidine monolayer was adsorbed on the surface of the gold electrode and further tailored with Cu2+ cation with the aim to investigate adsorption of histidine (His) and human serum albumin (HSA). Formation of the layer on the surface of the gold electrode was confirmed with quartz crystal microbalance. Binding of the His and HSA onto the modified electrode was successfully done for a wide range of tested concentrations. Electrode response was linearly proportional to the concentration of His and HSA with the correlation coefficients R2 = 0.9895 and R2 = 0.9952 respectively.

Electrical conductivity and electrode properties of the chalcogenide films PbS-AgI-As2S3, PbS-Ag2S-As2S3 and PbI2-Ag2S-As2S3 obtained by chemical deposition

Методом химического нанесения из растворов халькогенидных стекол в н-бутиламине получены халькогенидные пленки PbS-AgI-As2S3, PbS-Ag2S-As2S3 и PbI2-Ag2S-As2S3, изучена электропроводность и электродные свойства стекол и пленок аналогичного состава. Синтез стекол проводили согласно методике, описанной в [Легин, 1985]. Пленки наносили по следующей методике. Навеску стекла помещали в кипящий н-бутиламин, затем перемешивали в течение 3–4 ч до полного растворения стекла в амине. Для предотвращения окисления кислородом воздуха пленки наносили в закрытом боксе в атмосфере азота. Подложку помещали на устройство для вращения, наносили на нее раствор, а затем вращали подложку со скоростью 3000–4000 об/мин в течение 1 мин. Отжиг пленок проводили в боксе при температуре 90–100 С в течение 30–60 мин. Исследована электропроводность халькогенидных пленок PbS-AgI-As2S3, PbS-Ag2S-As2S3 и PbI2-Ag2S-As2S3. Величина электропроводности составляет 10–14–10–4 Ом.см–1. Установлено, что значения электропроводности стекол и пленок аналогичного состава практически не отличаются. Электроды с пленочными мембранами PbS- Ag2S-As2S3 и PbI2-Ag2S-As2S3 показали высокую чувствительность к катионам Pb2+. Нернстовская область электродного отклика лежит в пределах 10–2–10–6 моль/л нитрата свинца, предел обнаружения достигает 10–7 моль/л. Тонкопленочные электроды с мембранами PbS-AgI-As2S3 продемонстрировали достаточно высокую чувствительность к катионам Ag+. Нернстовская область электродного отклика составляет 10–1–10–6 моль/л AgNO3, предел обнаружения катионов серебра достигает 10–7 моль/л. Электродные свойства халькогенидных стекол и пленок аналогичного состава практически не отличаются. Chalcogenide films PbS-AgI-As2S3, PbS-Ag2S-As2S3 and PbI2-Ag2S-As2S3, were synthesized from the solutions of chalcogenide glasses in n-butylamine. The electrical conductivity and electrode properties of glasses and films of the same compositions were studied. The synthesis of glasses was carried out according to the procedure described in [Legin, 1985]. The films were prepared as follows. The sample of the glass was placed in boiling n-butylamine, then stirred for 3–4 hours until the glass was completely dissolved in the amine. To prevent oxidation by air oxygen, the films were applied in a closed box under a nitrogen atmosphere. The substrate was placed on a rotating device, a solution was applied thereto, and then the substrate was rotated at a speed of 3000–4000 rpm for 1 minute. Annealing of the films was carried out in the box at a temperature of 90–100 C for 30–60 min. Electrodes with membranes PbS-Ag2S-As2S3 and PbI2-Ag2S-As2S3 showed high sensitivity to cations Pb2+. The Nernst region of the electrode response lies in the range 10–2–10–6 mol/l lead nitrate, and the detection limit reaches 10–7 mol/l. Thin film electrodes with PbS-AgI-As2S3 membranes showed a fairly high sensitivity to the Ag+ cations. The Nernst region of the electrode response is 10–1–10–6 mol/l silver nitrate, the detection limit of Ag+ cations reaches 10–7 mol/l. It has been established that the electrode properties of chalcogenide glasses and films of similar composition are practically the same.

Synthesis and Characterization of Molecularly Imprinted Polymer for Tramadol Hcl Using Acryl Amide and 2-Hydroxyethyl Meth Acrylate as Monomers

Four electrodes were synthesized based on molecularly imprinted polymers (MIPs). Two MIPs were prepared by using tramadol hydrochloride (TRH) as the template, acryl amide (AA) and 2-hydroxy ethyl meth acrylate (2-HEMA) as monomers, divinyl benzene as a cross linker, and benzoyl peroxide as initiator, respectively. The same composition was used to prepare non-imprinted polymers (NIPs), but without the template (Tramadol hydrochloride). Different plasticizers were employed to prepare the membranes; tris (ethyl hexyl) phosphate (TEHP), tri Butyl phosphate (TBP), di-octyl phthalate (DOP) and nitrobenzene (NB) in PVC matrix. The electrode characteristics and properties were studied, including: slope, detection limit, life time and linearity range. The results of selectivity coefficient measurements using amino acids as interfering species showed no effect on tramadol electrode response. The prepared electrodes were intended for use in determining tramadol in pharmaceutical samples