In reliability contexts, probabilities of the type R=P(X<Y), where X and Y are random variables, have shown to be useful tools to compare the performance of these stochastic entities. By considering ...that both X and Y follow a transmuted generalized extreme-value (TGEV) distribution, new analytical relationships were derived for R in terms of special functions. The results hereby obtained are more flexible when compared to similar results found in the literature. To highlight the applicability and correctness of our results, we conducted a Monte-Carlo simulation study and investigated the use of the reliability measure P(X<Y) to select among financial assets whose returns were characterized by the random variables X and Y. Our results highlight that R is an interesting alternative to modern portfolio theory, which usually relies on the contrast of involved random variables by a simple comparison of their means and standard deviations.
An exact expression for R=P(X<Y) has been obtained when X and Y are independent and follow Birnbaum–Saunders (BS) distributions. Using some special functions, it was possible to express R ...analytically with minimal parameter restrictions. Monte Carlo simulations and two applications considering real datasets were carried out to show the performance of the BS models in reliability scenarios. The new expressions are accurate and easy to use, making the results of interest to practitioners using BS models.
A new composite material constituted by mu-{5,10,15,20-tetra(4-pyridyl)porphyrinato cobalt(iii)}-tetrakis-{chloro-bis-(2,2'-bipyridine)ruthenium(ii)} complex (or CoTRP) and cobalt oxide, exhibiting ...high stability and sensitivity for the quantification of hydrogen peroxide, was obtained by the electrochemical polymerization of the tetraruthenated cobalt porphyrin in alkaline medium. The optimized experimental conditions for the preparation of the modified glassy carbon electrodes and for analysis of H2O2 were carefully determined. Fast sequential analysis (120 determinations h(-1)) in a wide linear dynamic range (5.0 x 10(-7) mol L(-1) to 2.0 x 10(-3) mol L(-1)), with high sensitivity and low detection limit (2.0 x 10(-7) mol L(-1)), was achieved by using these electrodes and the batch injection analysis (BIA) technique. Such characteristics allied to a good stability were explored for the specific determination of hydrogen peroxide in six commercial cosmetics and pharmaceutical product samples, giving results in excellent agreement with those obtained by the spectrophotometric method.
A new electrocatalytic active porphyrin nanocomposite material was obtained by electropolymerization of
meso-tetra(4-sulphonatephenyl)porphyrinate manganese(III) complex (MnTPPS) in alkaline ...solutions containing sub-micromolar concentrations of silver chloride. The modified glassy carbon electrodes efficiently oxidize hydrazine at 10
mV
versus Ag/AgCl, dramatically decreasing the overpotential of conventional carbon electrodes. The analytical characteristics of this amperometric sensor coupled with batch injection analysis (BIA) technique were explored. Wide linear dynamic range (2.5
×
10
−7 to 2.5
×
10
−4
mol
L
−1), good repeatability (R.S.D.
=
0.84%,
n
=
30) and low detection (3.1
×
10
−8
mol
L
−1) and quantification (1.0
×
10
−7
mol
L
−1) limits, as well as very fast sampling frequency (60 determinations per hour) were achieved.
This paper proposes a new, fast and precise method to analyze isoniazid based on the electrochemical oxidation of the analyte at a glassy carbon electrode in 0.1
M NaOH. The quantification was ...performed utilizing amperometry associated with batch injection analysis (BIA) technique. Fast sequential analysis (60
determinations
h
−1) in an unusually wide linear dynamic range (from 2.5
×
10
−8 to 1.0
×
10
−3
M), with high sensitivity and low limits of detection (4.1
×
10
−9
M) and quantification (1.4
×
10
−8
M), was achieved. Such characteristics allied to a good repeatability of the current responses (relative standard deviation of 0.79% for 30 measurements), were explored for the specific determination of isoniazid in isoniazid–rifampin tablet.
Knowledge of soil properties and fertility status of farmers’ fields are basic information needed by Agricultural Extension Agents to guide farmers on wise and sustainable management of soil. The ...properties of some cultivated fields in the Sudano-Sahelian of Ghana and Humid Forest zones of Nigeria were studied. The aim was to quantify the soil properties and fertility status with a view to prescribing low input ecological technologies that would improve and sustain soil productivity. Core samples were taken from the depth of 0 – 40 cm in eleven and eight farmers’ fields in the Upper East Ghana and South East Nigeria, respectively. Soil properties determined using standard methods were; pH, TN, SOC, SOM, P, Exchangeable bases, EA, base saturation, PSD, WP, FC, bulk density, P and SHC. Both soils were sand in texture (> 700 g kg-1). The WP and FC were either below or within the lower border of critical levels. This shows crops in all the fields are prone to incipient wilting under any short dry spell. The chemical properties of the Sahelian-Sahelian zone showed that pH averaged 6.54 (moderate acidic), SOC 16 g kg-1 (low), TN 13 g kg-1 (very high), P, 18 mg kg-1 (moderate), K 0.23 C mol kg-1) (moderate), ECEC 8.18 C mol kg-1(medium fertility class). In the Humid Forest zones, pH was 4.38 (extremely acidic), SOC 7.41 g kg-1 (very low), N 1.78 g kg-1 (low), P 15.94 mg kg-1 (moderate), K 1.94 C mol kg-1 (very high) and ECEC 8.8 C mol kg-1 (medium fertility class). The fertility class indicates that the soils will response to external inputs and wise land management practices. A mix of Arbuscular mycorrhizal fungus (AMF), multipurpose tree species, contour cultivation, organic mulch, multiple crop mixture, under vetiver grass buffer strip is recommended.
The performance of a glassy carbon electrode modified with a porphyrin film formed by the Co(TPyP){Ru(bipy)
2Cl}
4(TFMS)
5·H
2O complex for the analysis of sodium metabisulfite in pharmaceuticals is ...described. The sensor can be rapidly and easily prepared by drop-casting of a microliter volume of a diluted methanolic solution of the complex onto the electrode surface. The modified electrode with a supramolecular cobalt porphyrin film led to more favorable responses than the bare electrode. This can be ascribed to the much faster electron transfer processes to the analyte mediated by the tetraruthenated porphyrin and to the protection of the electrode against fouling. The association of the amperometric sensor with the batch injection analysis technique led to results that combine good repeatability of the current responses (relative standard deviation of 0.94% for 30 measurements), wide linear dynamic range (2.5
×
10
−7
mol
L
−1 to 5.0
×
10
−4
mol
L
−1), high sensitivity and low limits of detection (8.1
×
10
−8
mol
L
−1) and quantification (2.7
×
10
−7
mol
L
−1). The system was successfully applied to sodium metabisulfite quantification in commercial samples of injection formulations of sodium (or potassium) diclofenac. The results compared well with those obtained by the polarographic method.
A sensitive method based on the preconcentration of uranium on powdered polyurethane foam (PUF) has been developed to determinate this element in water samples by X-ray florescence. Uranium at ppb ...levels was sorbed as the salicylate complex on powdered PUF at pH
4.0. The resulting PUF was filtered through a filter paper and used for X-ray fluorescence measurements. For 50
μg/l of uranium the coefficient of variation for five measurements is 5% and the detection limit is 5.5
μg/l. The interference level of various ions and ligands was studied and optimum conditions were developed to determine uranium in reference materials, waste water, mine drainage, and sea water.
This paper presents a simple, rapid and reproducible method of analysis of salbutamol in pharmaceutical products, utilizing batch injection analysis (BIA) associated with amperometric detection. A ...study of salbutamol oxidation demonstrated a strong dependence between electrode fouling and pH. All determinations were done utilizing a glassy carbon electrode in presence of 3.0
mol
l
−1 NaOH. A large linear dynamic range from 8×10
−7 to 2×10
−4
mol
l
−1 was obtained by using an injected volume of 100
μl with a detection limit of 2.5×10
−7
mol
l
−1. R.S.D. of 0.92% for 50 successive injections of 4×10
−6
mol
l
−1 of salbutamol and a sample throughput of 60 samples per hour were achieved. The method was applied for salbutamol quantification in syrups.
