Search for: All records

Illicit fentanyl and fentanyl analogs are a growing concern in the United States as opioid related deaths rise. Given that fentanyl analogs are readily obtained by modifying the structure of fentanyl, illicit fentanyl analogs appearing on the black market often contain similar structures, making analogue differentiation and identification difficult. Thus, obtaining both precursor and product ion data during analysis is becoming increasingly valuable in fentanyl analog characterization. In this paper, we provide GC column retention time, precursor, and product ion mass spectrum data for 74 fentanyl analogs that were analyzed using atmospheric pressure chemical ionization-gas chromatography−mass spectrometry (APCI-GC-MS) utilizing a triple quadrupole mass analyzer. During analysis, precursor ions underwent collision induced dissociation (CID) by increasing the collision energy (10, 20, 30, 40, and 50 V) throughout a single run. Data reveal that APCI readily produces product ions of the piperidine and N-alkyl chain but rarely provides data on the acyl group. Furthermore, fentanyl analogs with greater substitution at the N-alkyl chain demonstrate a greater preference for dissociation at the N-αC and αC-βC bond, while greater substitution at the amide group leads to fragmentation at the N−C4 bond. 

The production of ammonia for agricultural and energy demands has accelerated research for more environmentally-friendly synthesis options, particularly the electrocatalytic reduction of molecular nitrogen (nitrogen reduction reaction, NRR). Catalyst activity for NRR, and selectivity for NRR over the competitive hydrogen evolution reaction (HER), are critical issues for which fundamental knowledge remains scarce. Herein, we present results regarding the NRR activity and selectivity of sputter-deposited titanium nitride and titanium oxynitride films for NRR and HER. Electrochemical, fluorescence and UV absorption measurements show that titanium oxynitride exhibits NRR activity under acidic conditions (pH 1.6, 3.2) but is inactive at pH 7. Ti oxynitride is HER inactive at all these pH values. In contrast, TiN – with no oxygen content upon deposition – is both NRR and HER inactive at all the above pH values. This difference in oxynitride/nitride reactivity is observed despite the fact that both films exhibit very similar surface chemical compositions – predominantly Ti IV oxide – upon exposure to ambient, as determined by ex situ X-ray photoelectron spectroscopy (XPS). XPS, with in situ transfer between electrochemical and UHV environments, however, demonstrates that this Ti IV oxide top layer is unstable under acidic conditions, but stable at pH 7, explaining the inactivity of titanium oxynitride at this pH. The inactivity of TiN at acidic and neutral pH is explained by DFT-based calculations showing that N 2 adsorption at N-ligated Ti centers is energetically significantly less favorable than at O-ligated centers. These calculations also predict that N 2 will not bind to Ti IV centers due to a lack of π-backbonding. Ex situ XPS measurements and electrochemical probe measurements at pH 3.2 demonstrate that Ti oxynitride films undergo gradual dissolution under NRR conditions. The present results demonstrate that the long-term catalyst stability and maintenance of metal cations in intermediate oxidation states for pi-backbonding are critical issues worthy of further examination. 

Experimental water-to-methyl isobutyl ketone partition coefficientshave been determined for 27 different organic solutes based on gaschromatographic measurements. Updated Abraham model correlationswere determined for describing solute transfer into methyl isobutylketone by combining the measured partition coefficient data deter-mined in the present study with published experimental values takenfrom chemical and engineering literature. One hundred nineteen com-pounds were used in determining the revised Abraham model correla-tions. After calculations, the revised mathematical correlations werefound to match the experimental data to within an overall averagestandard deviation of 0.21 log units.