Electrochemical sensor highly selective for estradiol valerate determination based on a modified carbon paste with iron tetrapyridinoporphyrazine.

This work reports the use of iron tetrapyridinoporphyrazine (FeTPyPz) as a highly selective catalyst in the construction of an electrochemical sensor for estradiol valerate (EV) determination. The sensor was prepared by modifying a carbon paste with FeTPyPz. The best results were obtained in a mixture of acetonitrile (MeCN) and 0.1 mol L(-1) phosphate buffer solution (pH 6.0) in a volume ratio of 47 : 53. A linear response range was observed between 45 and 450 micromol L(-1) with a sensitivity of 12160 +/- 306 microA L mol(-1) and quantification and detection limits of 45 and 13 micromol L(-1), respectively. The repeatability, expressed as the relative standard deviation (RSD) for n = 10, was 5.9% ([EV] = 50 micromol L(-1)). The reproducibility (RSD) for the sensor construction was better than 4% and the operational stability (RSD) over 50 measurements was 1.8%. A detailed investigation regarding the selectivity and electrochemical characteristics was carried out. Finally, in a first step to evaluate the application potential of the sensor, it was successfully applied to determine EV in a commercial formulation.

Amperometric sensor for nitrite based on copper tetrasulphonated phthalocyanine immobilized with poly-L-lysine film.

In this work, an amperometric sensor for nitrite detection based on a glassy carbon electrode modified with copper tetrasulphonated phthalocyanine immobilized by polycationic poly-L-lysine film is presented. The modified electrode showed an excellent catalytic activity toward nitrite oxidation. A linear response range from 0.12 up to 12.20 micromol L(-1) was obtained with a sensitivity of 0.83 microA L micromol(-1). The detection limit for nitrite was 36 nmol L(-1). The repeatability of the proposed sensor, evaluated in terms of relative standard deviation, was 1% for 10 measurements of 10 micromol L(-1) nitrite solution. Finally, the developed sensor was applied for nitrite determination in water samples and the results were in agreement to the comparative method. The average recovery for the samples was 101 (+/-4)%.

Amperometric sensor for nitrite using a glassy carbon electrode modified with alternating layers of iron(III) tetra-(N-methyl-4-pyridyl)-porphyrin and cobalt(II) tetrasulfonated phthalocyanine.

The development of a highly sensitive amperometric sensor for nitrite using a glassy carbon electrode modified with alternated layers of iron(III) tetra-(N-methyl-4-pyridyl)-porphyrin (FeT4MPyP) and cobalt(II) tetrasulfonated phthalocyanine (CoTSPc) is described. The modified electrode showed an excellent catalytic activity and stability for the nitrite oxidation decreasing the peak potentials about 200mV toward less positive values and presenting much higher peak currents than those obtained on the bare GC electrode. A linear response range of 0.2-8.6mumoll(-1), with a sensitivity of 0.37muAlmumol(-1) and detection limit of 0.04mumoll(-1) were obtained with this sensor. The repeatability of the proposed sensor, evaluated in term of relative standard deviation, was verified to be 1.4% for 10 measurements of 0.2mumoll(-1) nitrite solution. Interference caused by common ions has been investigated in simulated mixtures containing high concentration level of interfering ions and the sensor was found to be tolerant against these ions. The developed sensor was applied for the nitrite determination in water samples and the results were in agreement with those obtained by a comparative method described in the literature. The average recovery for these samples was 100.1 (+/-0.7)%.