Direct injection of large volumes of plasma/serum on a new biocompatible extraction column for the determination of atenolol, propranolol and ibuprofen. Mechanisms for the improvement of chromatographic performance.
Very large volumes of serum/plasma can be directly injected to a new extraction column based on particles with a biocompatible outer surface and C18 groups within the pores. The biocompatibility has been obtained by attaching the human plasma protein alpha 1-acid glycoprotein to the outer surface of the particles. The pores are small enough to exclude the plasma protein molecules. Atenolol and propranolol were extracted on the extraction column as ion-pair with octanesulfonic acid as the counterion. The same counterion was used in the analytical mobile phase. A strong improvement of the recovery can be obtained using octanesulfonic acid as counterion in the extraction mobile phase. The recovery of atenolol increased from about 53.5% to about 93.4% using octanesulfonic acid as counterion. The chromatographic performance was also strongly affected by chromatography of the basic drugs as ion-pair with octanesulfonic acid. The improvement was due to trapping in a smaller section of the extraction column and enrichment of the drug on top of the analytical column. The enrichment was due to the transfer of the analyte to the analytical column in a zone with high concentration of counterion. Furthermore, the sample zone is compressed during the migration on the analytical column. The compression effect was caused by the counterion zone, migrating in front of the sample zone, giving the analyte higher retention on the front side than on the back side of the sample zone. Displacement of protein bound drug (ibuprofen) by addition of octanoic acid, was tested in order to study the influence on the recovery and the effect on the chromatographic performance. The recovery was improved and the chromatographic performance was greatly improved. The improvement obtained on the separation efficiency of ibuprofen was due to enrichment on top of the analytical column and compression during the migration through the analytical column. The enrichment was caused by a reduction of pH in the sample--octanoic acid zone transferred from the extraction column. The octanoic acid zone migrated in front of the sample zone giving a lower pH in front of the ibuprofen zone than behind. Thus, higher retention occurred in front of than behind the sample zone, which gave rise to compression. The methods developed for atenolol, propranolol and ibuprofen could be used for the determination of serum/plasma concentrations after single doses of the drugs with very high accuracy and precision. Linear calibration graphs were obtained and the r values were > or = 0.9999.
Hermansson
J
J
ChromTech, Hägersten, Sweden.
Grahn
A
A
Hermansson
I
I
D000319:Adrenergic beta-Antagonists / Q000097:blood*; D018712:Analgesics, Non-Narcotic / Q000097:blood*; D001262:Atenolol / Q000097:blood*; D001672:Biocompatible Materials; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D007052:Ibuprofen / Q000097:blood*; D007202:Indicators and Reagents; D011433:Propranolol / Q000097:blood*; D015203:Reproducibility of Results; D012997:Solvents; D013056:Spectrophotometry, Ultraviolet
D000319:Adrenergic beta-Antagonists; D018712:Analgesics, Non-Narcotic; D001672:Biocompatible Materials; D007202:Indicators and Reagents; D012997:Solvents; D001262:Atenolol; D011433:Propranolol; D007052:Ibuprofen