Certification of bilirubin SRM 916a

Summary The process used to certify Standard Reference Material (SRM) 916a Bilirubin is described. The certification involved the use of various analytical techniques to detect or quantitate impurities, as well as to characterize the SRM itself. Bilirubin (BR) is believed to exist, in human serum, as the IX isomer. Samples prepared commercially, including this SRM, also contain the III and XIII isomers which are believed to be formed during purification. For the SRM, the three isomers were measured by HPLC and TLC. ¹H NMR was used to detect and quantitate chloroform in the BR. Biliverdine and mesobilirubin were not detected. Impurities insoluble in chloroform, the residue from the ashing of BR, and volatiles were measured, in addition to non-acidic impurities and impurities more acidic than BR. The absorptivity of BR in chloroform was measured. A pink fluorescent impurity was detected and measured by TLC. From these analyses, a best estimate of the total amount of impurities was determined, and the BR was issued as SRM 916a with a certified purity of 98.3±0.3%.     

Temperature induced effects in the coadsorption system: CO/D2/Ni(100)

The temperature dependent changes in the CO/D/Ni(100) system have been examined using thermal desorption spectroscopy, work function change measurements, ultra-violet photoelectron spectroscopy and X-ray photoelectron spectroscopy. Three forms of CO(a) have been found, one of which exists only in the intermediate temperature range of 130–215 K. This form is believed to be a CO(a) tilted with respect to the surface normal, with significant ONi interaction. In addition, a new interpretation of several UPS parameters measured for CO(a) is presented. It is proposed that for CO(a), the 5σ?1π separation is a probe of bonding geometry, the 4σ?1π separation reflects COCO repulsion, and the $\text{4σ}\text{5σ}$ intensity ratio reflects the NiCO bond strength.     

The interaction of oxygen with Bi(0001): Kinetic,electronic, and structural features

The interaction of oxygen with clean Bi(0001) was studied for adsorption between 118 and 296 K using LEED, Auger, electron energy loss, and work function measurements. Oxygen adsorption kinetics show an activated process with a dissociative sticking probability (<10^?4) which smoothly decreases over two orders of magnitude up to saturation coverage. Changes in surface electronic properties indicate that an oxide-like bond is formed from the onset of adsorption. There is no evidence for a stable chemisorbed phase. LEED shows simultaneous growth of epitaxial BiO(0001) and a $\text{3}$ overlayer. At 296 K the adsorption terminates after about three equivalent monolayers of BiO(0001). Periodic trends extended from the transition metal series suggest that local and atomic characteristic rather than long-range electronic properties determine the low reactivity of this surface toward O₂.     

Leed investigations of some models for reconstructed (100) surfaces of silicon

Evidence is presented for (100) surfaces of silicon that buckled asymmetric dimerization models, of the type emphasized by Chadi, can give at least a partial account of experimental LEED intensity data within both the QD and CMTA methods of investigation. This suggests a possible resolution of a discrepancy in the literature between other LEED studies (from which the symmetric dimerization model and a model with vacancies in the top two layers have been reported) and evidence from photoemission and ion scattering which supports the Chadi-type reconstruction.     

Polyetherimides via nitro-displacement polymerization: Monomer synthesis and 13C-NMR analysis of monomers and polymers

The synthetic route to polyetherimides by displacement of nitro-groups from disubstituted bis-imides by the dianion of bisphenols are described. The prepration of bis-imides and bisphenol dianions, their polymerization, and some of the properties of the polymers are presented in detail. The ¹³C-NMR spectra of intermediates and products were used to establish compositions and determine molecular weights.