Ion Chromatographic Determination of Sulfide and Cyanide in Real Matrices by Using Pulsed Amperometric Detection on Ag Electrode

The determination of free sulfide and cyanide by pulsed amperometric detection (PAD) at a silver-working electrode was improved through a deep de-oxygenation (at least 10 min) of both standard and real solutions containing the two analytes and adopting a two-potential waveform able to eliminate Ag working electrode fouling. The waveform stepped around the oxidation of Ag in the presence of 0.1\u20130.4 M hydroxyl ion, from 120.1 to 0.1 V versus saturated calomel electrode (SCE). The eluent composition (0.4M NaOH plus 7.5mM oxalate solution) allowed a very good column efficiency and selectivity. The presence of a polysulfide species was hypothesized in sulfide solutions that had not been de-oxygenated and aged. The polysulfide eluted just before sulfide and was confirmed by a chemical test with SO3 2 12 producing the elimination of the polysulfide peak. Detection limits, according to the Hubaux\u2013Vos method, were 1.0 and 2.0 \ub5g/l for S2 12 and CN 12, respectively. We demonstrated good performance of the optimized method by repeatedly injecting standard solutions and by analyzing different real matrices. The method exhibited very good accuracy and repeatability (10 \ub5g/l and a 500 \ub5l injection loop, had a repeatability better than 3% for sulfide and 100 \ub5g/l had a repeatability better than 1% for cyanide). The two-potential waveform ensured long-term stability of the electrode surface that required no manual polishing procedure for at least 1 month (20 analysis per day)

Muscle spindles of the rat sternomastoid muscle

The sternomastoid (SM) muscle in rodents presents a peculiar distribution of fiber types with a steep gradient from the ventral, superficial, white portion to the dorsal, deep, red region, where muscle spindles are restricted. Cross section of the medial longitudinal third of the rat SM contains around 10,000 muscle fibers with a mean diameter of 51.28±12.62 (μm +/- SD). Transverse sections stained by Succinate Dehydrogenase (SDH) reaction clearly presents two distinct regions: the dorsal deep red portion encompassing a 40% cross section area contains a high percentage of packed SDH-positive muscle fibers, and the ventral superficial region which contains mainly SDH-negative muscle fibers. Indeed, the ventral superficial region of the rat SM muscle contains mainly fast 2B muscle fibers. These acidic ATPase pH 4.3-negative and SDH-negative 2B muscle fibers are the largest of the SM muscle, while the acidic ATPase pH 4.3-positive and SDH-positive Type 1 muscle fibers are the smallest. Here we show that in thin transverse cryosections only 2 or 3 muscle spindle are observed in the central part of the dorsal deep red portion of the SM muscle. Azan Mallory stained sections allow at the same time to count the spindles and to evaluate aging fibrosis of the skeletal muscle tissue. Though restricted in the muscle red region, SM spindles are embedded in perimysium, whose changes may influence their reflex activity. Our findings confirm that any comparisons of changes in number and percentage of muscle spindles and muscle fibers of the rat SM muscle will require morphometry of the whole muscle cross-section. Muscle biopsies of SM muscle from large mammals will only provide partial data on the size of the different types of muscle fibers biased by sampling. Nonetheless, histology of muscle tissue continue to provide practical and low-cost quantitative data to follow-up translational studies in rodents and beyond

Intracellular detection of Cu 2+

A new quinazoline functionalized benzimidazole-based fluorogenic chemosensor H3L is synthesized and fully characterized by conventional techniques including single crystal X-ray analysis. It acts as a highly selective colorimetric and fluorescence sensor for Cu2+ ions in DMF/0.02 M HEPES (1 : 1, v/v, pH = 7.4) medium. Reaction of H3L with CuCl2 forms a mononuclear copper(II) [Cu(Cl)(H2L)(H2O)] (H2L–Cu2+) complex which is characterized by conventional techniques and quantum chemical calculations. Electronic absorption and fluorescence titration studies of H3L with different metal cations show a distinctive recognition only towards Cu2+ ions even in the presence of other commonly coexisting ions such as Li+, Na+, K+, Mg2+, Ca2+, Fe2+, Fe3+, Mn2+, Co2+, Ni2+, Zn2+, Cd2+ and Hg2+. Moreover, H2L–Cu2+ acts as a metal based highly selective and sensitive chemosensor for S2− ions even in the presence of other commonly coexisting anions such as F−, Cl−, Br−, I−, SO42−, SCN−, AcO−, H2PO4−, PO43−, NO3−, ClO4−, NO2−, HSO4−, HSO42−, S2O32−, S2O82−, CN−, CO32− and HCO3− in DMF/0.02 M HEPES (1 : 1, v/v, pH = 7.4) medium. Quantification analysis indicates that these receptors, H3L and H2L–Cu2+, can detect the presence of Cu2+ and S2− ions at very low concentrations of 1.6 × 10−9 M and 5.2 × 10−6 M, respectively. The propensity of H3L as a bio-imaging fluorescent probe for detection of Cu2+ ions and sequential detection of S2− ions by H2L–Cu2+ in Dalton lymphoma (DL) cancer cells is also shown