Characterization of a highly stable zwitterionic hydrophilic interaction chromatography stationary phase based on hybrid organic-inorganic particles.

We have characterized a sulfobetaine stationary phase based on 1.7 µm ethylene-bridged hybrid organic-inorganic particles, which is intended for use in hydrophilic interaction chromatography. The efficiency of a column packed with this material was determined as a function of flow rate, demonstrating a minimum reduced plate height of 2.4. The batch-to-batch reproducibility was assessed using the separation of a mixture of acids, bases, and neutrals. We compared the retention and selectivity of the hybrid sulfobetaine stationary phase to that of several benchmark materials. The hybrid sulfobetaine material gave strong retention for polar neutrals and high selectivity for methyl groups, hydroxy groups, and configurational isomers. Large differences in cation and anion retention were observed among the columns. We characterized the acid and base stability of the hybrid sulfobetaine stationary phase, using accelerated tests at pH 1.3 and 11.0, both at 70°C. The results support a recommended pH range of 2-10. We also investigated the performance of columns packed with this material for metal-sensitive analytes, comparing conventional stainless steel column hardware to hardware that incorporates hybrid surface technology to mitigate interactions with metal surfaces. Compared to the conventional columns, the hybrid surface technology columns showed a greatly improved peak shape.

Retention and mass transfer properties of the series of unbonded, amide-bonded, and alkylsulfobetaine-bonded ethylene bridged hybrid hydrophilic interaction liquid chromatography columns.

This work investigates the link between the retentivity and the stationary phase to mobile phase mass transfer resistance of hydrophilic interaction liquid chromatography (HILIC) columns packed with the same base ethylene-bridged hybrid particles (BEH). The retention volumes, the plate heights, and the volume of the adsorbed water layer were measured for the ACQUITYTM UPLCTM BEHTM 130 Å HILIC Column (unbonded BEH), ACQUITY UPLC BEH 130 Å Amide Column (amide group attached), and AtlantisTM Premier BEH 95 Å Z-HILIC (zwitterionic group attached) Column. The method of Guo (toluene retention volumes in pure acetonitrile and in the HILIC eluent) was validated from the UNIFAC group-contribution method and applied to measure accurately the water layer volumes in these columns. A strong correlation was found between the retention volumes of most neutral polar analytes and the volume of the water layer adsorbed in the HILIC column. The fraction of the pore volume occupied by the water layer increases significantly from the BEH HILIC Column to the BEH Amide Column, and to the BEH Z-HILIC Column. This is explained by the water solvation of the attached ligands in the pore volume of the BEH Particles and to the smaller average mesopore size of the BEH Z-HILIC Particles. A second and strong correlation is also observed between the water content in the HILIC particle and the stationary phase to mobile phase mass transfer resistance of the HILIC columns at high mobile phase linear velocities. The measured intra-particle diffusivity normalized to the bulk diffusion coefficient decreased from 0.33 (BEH HILIC Column) to 0.10 (BEH Amide Column) and to only 0.03 (BEH Z-HILIC Column) for comparable retention of cytosine. These results are fully consistent with the higher viscosity of the internal eluent (higher water content) and higher internal obstruction for diffusion (smaller mesopores and internal porosity) in the BEH Z-HILIC Particles. Still, in gradient elution mode, the peak capacity was found to be 18% higher for the BEH Z-HILIC Column than that on the BEH Amide Column because the retention factors at elution were smaller when maintaining the same analysis time and starting eluent composition.

A randomized comparison of ferumoxytol and iron sucrose for treating iron deficiency anemia in patients with CKD.

BACKGROUND AND OBJECTIVES: Few randomized controlled trials have compared intravenous iron products head to head in CKD patients with iron deficiency anemia. This study compared the efficacy and safety of two intravenous iron products (ferumoxytol [Feraheme injection] and iron sucrose [Venofer]) in patients with CKD and iron deficiency anemia. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: In this phase II, randomized, open-label, active-controlled, multicenter clinical trial, patients were randomized 1:1 to either 1.02 g ferumoxytol (2 × 510-mg injections) or 1.0 g iron sucrose administered as either a slow injection or infusion (10 doses for dialysis patients and 5 doses for nondialysis patients). Inclusion criteria included hemoglobin<11.0 g/dl, transferrin saturation<30%, and eGFR<60 ml/min per 1.73 m(2) or a diagnosis of underlying CKD (e.g., nephropathy or nephritis). The primary end point was change in hemoglobin from baseline to week 5. RESULTS: In total, 162 patients were randomized. Demographics were balanced between the treatment groups. Adverse event profiles of the two regimens were fairly similar: overall adverse events, 48% ferumoxytol versus 65% iron sucrose; related adverse events, 10% ferumoxytol versus 16% iron sucrose; and adverse events leading to study discontinuation, 1% ferumoxytol versus 5% iron sucrose. Rates of serious adverse events and related serious adverse events were similar between the ferumoxytol and iron sucrose groups: serious adverse events, 9% versus 7%, respectively and related serious adverse events, 1% versus 1%, respectively. Overall, increases in hemoglobin were similar between treatment groups. Based on an ANOVA model adjusted for baseline hemoglobin level and dialysis status, the least squares mean change from baseline to week 5 was 0.8 ± 0.1 g/dl in the ferumoxytol-treated group and 0.7 ± 0.1 g/dl in the iron sucrose group. The difference in the mean change from baseline between the two treatment groups was 0.1 g/dl (95% confidence interval, -0.2 to 0.4). CONCLUSION: In this randomized, controlled trial, ferumoxytol and iron sucrose showed comparable efficacy and adverse events rates.