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Biomedical subjects

N G Lordi

Publications and source records attributed to N G Lordi.

25 records · Page 2Linked to original sources
PubMedDate not supplied

Quantitative and mechanistic measurements of parenteral vial container/closure integrity. Leakage quantitation.

Leakage across the parenteral vial/closure seal interface is quantitatively measured in terms of mass of gas per unit time using a differential pressure method of leakage measurement. With this test system, uncoated, Purcoat coated, and film coated closures are compared for their ability to seal nondefective and defective vial surfaces. Correlations are made between closure sealing performance and rubber viscoelasticity, closure coating material type and thickness, and crimped vial residual seal force.

Drug Packaging↗
PubMedDate not supplied

Quantitative and mechanistic measurements of container/closure integrity. Bubble, liquid, and microbial leakage tests.

The parenteral vial/closure seal interface is tested for leakage of gas, liquids, and microorganisms. Gas leakage is determined using a bubble test, liquid leakage is detected by atomic absorption of a copper ion tracer solution, and microbial leakage is verified using a liquid-borne microbial suspension challenge test. Leakage performance by these methods is compared to gaseous leakage rates quantitatively determined for the same package systems. The establishment of leakage rate specifications based on these results is discussed.

Drug Contamination↗
PubMedDate not supplied

Dielectric characterization of thermodynamic first order events in model frozen systems intended for lyophilization.

The degree and ease with which permanent dipoles in a frozen sample orient in an applied electric field is affected during thermal transitions. This motion can be monitored with dielectric analysis (DEA) at low AC frequencies (< approximately 300,000 Hz). The systems characterized with respect to their behavior in the frozen state consisted of common lyophile excipients in aqueous solutions known to exhibit typical thermodynamic first order transitions. Prior to freezing, solution samples were placed on an interdigitated electrodes and served as the dielectric component of the resulting capacitor. Plots of derivative of dielectric permittivity with respect to time (or temperature) showed the presence of frequency independent peaks (signifying a first order event) at temperatures that coincided with eutectic temperatures (ca. -22 degrees C for sodium chloride-water and ca. -5 degrees C for mannitol-water), amorphous to crystalline transition temperatures (ca. -25 degrees C for mannitol-water), and/or freezing point depression values in water. The values obtained by DEA correlated well with differential scanning calorimetry (DSC) and literature values. DEA appears to offer added insight over established techniques by not only determining the temperature at which these events occur, but also by defining the thermodynamic order of the event.

Electrochemistry↗
PubMedDate not supplied

Prediction of lyophile collapse temperature by dielectric analysis.

A new method for predicting lyophile collapse temperatures based upon dielectric analysis (DEA) of frozen two component systems is presented. The method, called the take off frequency model (TOF), relies both on the inherent ability of DEA to detect molecular motion and on the abrupt change in viscosity experienced by a frozen sample undergoing a glass-liquid transition. Collapse temperatures for binary glass forming systems (an antibiotic, sucrose, trehalose, or sorbitol, with water) were in good agreement with the values reported in the literature. DEA was easily able to detect glass transitions poorly defined by differential scanning calorimetry (DSC). Conservative lyophilization cycles for simple systems can be quickly determined on the basis of the TOF model.

Calorimetry, Differential Scanning↗