Characterization of Salophen Co(III) Acetate Ionophore for Nitrite Recognition

Comparison of electrochemical nitric oxide detection methods with chemiluminescence for measuring nitrite concentration in food samples

Nitrite is a naturally occurring species present in various food samples and also present in our bodies as a product of nitric oxide (NO) oxidation. Considering the ubiquity of nitrite, its determination is of great importance in both biological and food samples. Herein, a very facile indirect method of nitrite determination in meat samples via selective reduction to nitric oxide (NO) is presented. The resulting gaseous product is quantified via portable and cost-effective electrochemical sensors. Both a novel laboratory prepared Pt-Nafion based NO sensor and a commercially available amperometric NO sensor are compared. Excellent correlations between the nitrite amount found in tested samples using both of the electrochemical sensors and a reference chemiluminescence method are demonstrated (r = 0.997 and r = 0.999 for Pt-Nafion based and commercially available NO-B4 electrochemical sensors, respectively, n = 12). Moreover, the slope of the linear regression curves are very close to unity for the comparison of the three systems tested. The amperometric sensors compared within this work exhibit good precision and accuracy and are shown to be an attractive alternative to the costly chemiluminescence detection method for accurately determining nitrite levels in food samples.

NOx- anion recognition by bimetallic cryptates: selectivity for nitrite over nitrate

Nitrate and nitrite anions have multifaceted impacts on the environment and human health. We herein report selective recognition of nitrite over nitrate anion inside the cavity of bimetallic azacryptates having p-xylyl spacers. This work reveals a number of binding interactions which play pivotal roles in nitrite anion recognition by rigid metal cryptates.

Calixarene-doped PVC polymeric films as size-selective optical sensors: Monitoring of salicylate in real samples

Preparation of novel salicylate-selective optical sensors (bulk optodes) was performed and applied successfully for salicylate determination in pharmaceutical formulations, Aspirin® and Aspocid®. t-butyl calix[4]arene ionophore was incorporated in a plasticized poly (vinyl-chloride) membrane containing the chromoionophore ETH5294 (O₁) or ETH7075 (O₅). The optical response to salicylate was due to size-selective extraction of salicylate from the aqueous solution to the optode bulk through formation of hydrogen bond accompanied by chromoionophore protonation, that resulted in the optical response at 680 or 540 nm for O₁ or O₅, respectively. Reliable size-selectivity was measured for salicylate over other anions; The calculated selectivity coefficients of O₅ optode were found to be: -4.4, -2.0 and - 3.7 for iodide, benzoate and perchlorate, respectively. The hydrogen bonding mechanism and selectivity pattern were ensured and explained by IR and ¹H NMR spectroscopy. For the same purpose, a molecular recognition constant of β_sal=10^0.043 was calculated using sandwich membrane method, and its small value ensured that hydrogen bonding interaction is responsible for the optode response. The detection limits of O₁ and O₅ in salicylate buffered solutions were 9.0 × 10^-5 and 8.9 × 10^-5 M with response times of 5 and 3 min, respectively, and with very good reversibility. The practical utility of the developed sensors was ensured by salicylate determination in Aspirin® and Aspocid®. Beyond the observed analytical performance, the present work aims not only to effectively apply Calixarene without derivatization, but also to estimate the strength of the size-dependent hydrogen bonding and comprehensively study the interaction mechanism.

Crystal structure of 1,1′-((1E,1′E)-(((ethane-1,2-diylbis(oxy))bis(2,1-phenylene))bis(azanylylidene))bis(methanylylidene))bis(naphthalen-2-olato)cobalt(II), C36H26N2O4Co

C36H26N2O4Co, monolinic, C2/c (no. 15), a = 43.230(14) Å, b = 17.100(6) Å, c = 11.275(4) Å, β = 103.112(4)°, V = 8118(5) Å3, Z = 12, R gt(F) = 0.0370, wR ref(F 2) = 0.0931, T = 100(2) K.