Spectrofluorimetric determination of oseltamivir phosphate through derivatization with o‐phthalaldehyde. Application to pharmaceutical preparations with a preliminary study on spiked plasma samples

Abstract

A simple and sensitive spectrofluorimetric method has been developed and validated for the determination of oseltamivir phosphate (OST) in pharmaceutical preparations. The method is based on the reaction between oseltamivir phosphate and o-phthalaldehyde in presence of 2-mercapto-ethanol in borate buffer, pH 10.8, to give a highly fluorescent product measured at 450 nm after excitation at 336 nm. The different experimental parameters affecting the development and stability of the reaction product were studied and optimized. The fluorescence intensity-concentration plot is rectilinear over the range 0.05-1.0 µg/mL, with a lower detection limit of 5 ng/mL and limit of quantitation of 16 ng/mL. The developed method was successfully applied to the analysis of the drug in its commercial capsules and suspension, mean recoveries of OST were 99.97 ± 1.67% and 100.17 ± 1.18%, respectively (n = 3). Statistical comparison of the results obtained by the proposed and comparison method revealed no significant difference in the performance of the two methods regarding accuracy and precision. The proposed method was further extended to in vitro determination of the studied drug in spiked human plasma as a preliminary investigation; the mean recovery (n = 3) was 98.68 ± 5.8%. A reaction pathway was postulated.

Simultaneous quantification of prodrug oseltamivir and its metabolite oseltamivir carboxylate in human plasma by LC–MS/MS to support a bioequivalence study

“…Based on the high S/N values it was possible lower the quantitation limit by 3 folds; however, it not required based on subject sample results. The sensitivity achieved for OST and OSTC in the present work was higher compared to all other methods developed in human plasma [9] , [10] , [12] , [15] , [16] , [17] , [18] . The LOD values found at S/N≥10 (% CV less than 15) were 0.15 and 0.62 ng/mL for OST and OSTC respectively.…”

“…Further, the entire extraction process was carried out in ice bath maintained below 10 °C. Reported procedures have employed protein precipitation (PP) [18] , liquid–liquid extraction (LLE) [15] , [17] , solid phase extraction (SPE) [7] , [8] , [9] , [12] , [13] , [14] , [16] or a combination of PP and on-line SPE [10] for sample preparation of OST and/or OSTC from different biological samples. Thus, PP was tried with trichloroacetic acid in water (5–10%) as reported earlier [18] .…”

“…Several assays have been reported for the determination of oseltamivir and/or its active metabolite oseltamivir carboxylate in different biological matrices such as rat plasma [7] , [8] , [9] , [10] , mouse plasma [9] , rat urine [9] , rat cerebrospinal fluid [10] , rat brain [10] , rat dried blood spot (DBS) [11] , human DBS [11] , human saliva [12] , human urine [9] , [10] , [12] , [13] , human blood [13] , human tissue [13] , human serum [14] and human plasma [9] , [10] , [12] , [15] , [16] , [17] , [18] . Although there are many reports dealing with simultaneous estimation of OST and OSTC in biological samples [8] , [9] , [10] , [11] , [12] , [16] , [18] , relatively few methods have been used for bioequivalence/pharmacokinetic study in patients [18] or healthy volunteers [4] , [5] , [14] .…”

“…17.0 mL –; application in spiked plasma samples; – [15] 8 LC–MS/MS; 0.92/5.22 ng/mL in human plasma SPE; 500 μL human plasma; acyclovir; 68.7/70.7% 0.39/0.38 min; 1.0 min; 5 μL; 9.3/6.2 ng App. 2.0 mL – [16] 9 b Spectrofluorimetry; 16 ng/mL/– in human plasma LLE followed by derivatization; 1000 μL human plasma; –; 98.7% – – –; –; preliminary in vitro study in spiked plasma samples; – [17] 10 LC–MS/MS; 3.0/10 ng/mL in human plasma PP; 50 μL human plasma; OST-d5 and OSTC-C13-d3; 97.4/104.3% 5.0/4.7 min; 9.0 min;10 μL; 1.5/50 ng App. 2.0 mL –;app.…”

A highly sensitive fluorimetric protocol based on isoindole formation for determination of gabapentin

“…This approach has been applied for the determination of several pharmaceutical compounds. [15][16][17] A condensation reaction occurs between the aldehydic groups of o-phthalaldehyde and primary amine group of gabapentin lead to formation of a high uorescent reaction product. Addition of 2-mercaptoethanol to the solution is essential to stabilize the formed reaction product.…”