Plant sterol and stanol esters were separated on a Luna hexyl-phenyl column using a gradient of acetonitrile (90-100%) in water. The eluted compounds were detected by atmospheric pressure chemical ionization (APCI)-mass spectroscopy (MS) in the positive mode. Sterol and stanol esters produced [M + H - HOOCR](+) ions. Application of the hyphenated technique-LC-MS-allowed differentiation between a number of esters of sitosterol, campesterol, stigmasterol, and (tentatively) avenasterol, as well as sitostanol and campestanol esters. With cholesteryl decanoate used as the internal standard, the method showed good linearity, precision, and reproducibility. The method required minimal sample pretreatment and can be applied to samples with high water content (juices) as well as samples with high oil content (margarine spreads). The method could be useful for the analysis of sterol and stanol esters in fortified food products.

Human blood was sheared between rotating polyethylene disks and plasma hemoglobin measured at intervals to produce kinetic hemolysis curves (KHC), plotted as free hemoglobin concentration vs time. The KHC produced by blood samples incubated in the presence of penicillin, streptomycin, gentamicin, and amikacin lie always below those for control samples, indicating a reduction in hemolysis; this reduction was greater as the drug concentration was increased. Explanations in terms of alterations in red cell structure were sought by several characterization tests of amikacin-loaded blood samples. Drug-localization studies demonstrated that significant fractions of the total dosage were associated with the red-cell membrane. Resistive pulse spectroscopy was used to show how amikacin affected cell size, deformability, and osmotic fragility; results were sensitive to storage age of the blood. In all cases, the effect of shearing was to reduce cell size, deformability, and osmotic fragility. Mechanisms for hemolytic protection by drugs are proposed.

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Three types of materials of special interest to the NIH Biomaterials Program were evaluated for their tendency to induce hemolysis when exposed to a laminar blood flow between rotating parallel disks. The three types were: (1) TDMAC-heparinized surfaces of polycarbonate (Lexan), silicone rubber, and polyvinylchloride; (2) polyacrylamide hydrogels (PAH) prepared by three different chemical processes; and (3) fluorinated ethylcellulose (FEC). All were compared to a polyethylene (PE) standard, to normalize data for variations in blood quality. Multiple tests, showing good reproducibility, demonstrated: FEC is a very low hemolyzer, about 60% of the PE; PAH surfaces are poorer than PE, giving 120-220% of PE hemolysis depending on fabrication and shipment history; and TDMAC-heparinized surfaces are highly hemolytic, in the range 160-440% of PE depending on substrate. Plastics used as substrates for the coating cited above were also evaluated: Delrin, Lexan, Nylon 6, propylene, and a polyether urethane. Tentative explanations are advanced for hemolytic variations, in terms of surface chemistry and material interactions with the blood.

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