The importance of chain length for the polyphosphate enhancement of acidic potassium permanganate chemiluminescence

Sodium polyphosphate is commonly used to enhance chemiluminescence reactions with acidic potassium permanganate through a dual enhancement mechanism, but commercially available polyphosphates vary greatly in composition. We have examined the influence of polyphosphate composition and concentration on both the dual enhancement mechanism of chemiluminescence intensity and the stability of the reagent under analytically useful conditions. The average chain length (n) provides a convenient characterisation, but materials with similar values can exhibit markedly different distributions of phosphate oligomers. There is a minimum polyphosphate chain length (∼6) required for a large enhancement of the emission intensity, but no further advantage was obtained using polyphosphate materials with much longer average chain lengths. Providing there is a sufficient average chain length, the optimum concentration of polyphosphate is dependent on the analyte and in some cases, may be lower than the quantities previously used in routine detection. However, the concentration of polyphosphate should not be lowered in permanganate reagents that have been partially reduced to form high concentrations of the key manganese(III) co-reactant, as this intermediate needs to be stabilised to prevent formation of insoluble manganese(IV).     

Determination of selected neurotransmitter metabolites using monolithic column chromatography coupled with chemiluminescence detection

The oxidation of selected clinically important neurotransmitter metabolites with acidic potassium permanganate in the presence of polyphosphates evokes chemiluminescence of sufficient intensity to enable the sensitive determination of these species. Limits of detection for 5-hydroxyindole-3-acetic acid (5-HIAA), vanilmandelic acid (VMA; α,4-dihydroxy-3-methoxybenzeneacetic acid), 4-hydroxy-3-methoxyphenylglycol (MHPG), homovanillic acid (HVA, 4-hydroxy-3-methoxyphenylacetic acid) and 3,4-dihydroxyphenylacetic acid (DOPAC) were between 5 × 10⁻⁹ and 4 × 10⁻⁸ M, using flow-injection analysis methodology. In addition, we demonstrate the rapid determination of homovanillic acid and 5-hydroxyindole-3-acetic acid in human urine - without the need for extraction procedures - using monolithic column chromatography with chemiluminescence detection.     

Monomeric Chini‐Type Triplatinum Clusters Featuring Dianionic and Radical‐Anionic π*‐Systems

Owing to their unique topologies and abilities to self‐assemble into a variety of extended and aggregated structures, the binary platinum carbonyl clusters [Pt₃(CO)₆]_n^2? (“Chini clusters”) continue to draw significant interest. Herein, we report the isolation and structural characterization of the trinuclear electron‐transfer series [Pt₃(μ‐CO)₃(CNAr^Dipp2)₃]^n? (n=0, 1, 2), which represents a unique set of monomeric Pt₃ clusters supported by π‐acidic ligands. Spectroscopic, computational, and synthetic investigations demonstrate that the highest‐occupied molecular orbitals of the mono‐ and dianionic clusters consist of a combined π*‐framework of the CO and CNAr^Dipp2 ligands, with negligible Pt character. Accordingly, this study provides precedent for an ensemble of carbonyl and isocyanide ligands to function in a redox non‐innocent manner.     

Measurement of the Lambda b0 lifetime in Lambda b0-->J/psi Lambda 0 in pp collisions at square root s=1.96 TeV

We report a measurement of the Lambda b0 lifetime in the exclusive decay Lambda b0-->J/psi Lambda 0 in pp collisions at square root s=1.96 TeV using an integrated luminosity of 1.0 fb-1 of data collected by the CDF II detector at the Fermilab Tevatron. Using fully reconstructed decays, we measure tau(Lambda b0)=1.593(-0.078)(+0.083)(stat)+/-0.033(syst) ps. This is the single most precise measurement of tau(Lambda b0) and is 3.2sigma higher than the current world average.     

Measurement of prompt charm meson production cross sections in pp collisions at square root s = 1.96 TeV

We report on measurements of differential cross sections dsigma/dp(T) for prompt charm meson production in ppmacr; collisions at sqrt[s]=1.96 TeV using 5.8+/-0.3 pb(-1) of data from the CDF II detector at the Fermilab Tevatron. The data are collected with a new trigger that is sensitive to the long lifetime of hadrons containing heavy flavor. The charm meson cross sections are measured in the central rapidity region |y|K-pi(+), D(*+)-->D0pi(+), D+-->K-pi(+)pi(+), D(+)(s)-->phipi(+), and their charge conjugates. The measured cross sections are compared to theoretical calculations.     

Elongated conformers of charge states +11 to +15 of bovine ubiquitin studied using ESI-FAIMS-MS

Recent advancements in high-field asymmetric waveform ion mobility spectrometry (FAIMS) have led to significant improvements in the application of this technology to the study of protein conformers. Compared with previous work, the maximum value of the separation voltage (i.e., the dispersion voltage) has increased, thereby enabling multiple, elongated conformers of individual charge states of bovine ubiquitin to be separated in the gas phase (e.g., four conformers of each of the +11 and +12 charge states were separated). The use of a carrier gas mixture of 40% nitrogen and 60% helium changed the separation selectivity compared with pure nitrogen and enhanced the signal intensity, especially for the +14 and +15 charge states (the latter was not detected in a nitrogen carrier gas). Conformer cross sections were determined using the FAIMS/energy-loss method and found to be similar within a given charge state. The cross sections for conformers of charge states +13, + 14, and +15 plateau at about 2000 A2 suggesting that the structure of bovine ubiquitin is essentially unfolded after the addition of the 13th proton.