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Determination of oseltamivir quality by colorimetric and liquid chromatographic methods.

Green MD, Nettey H, Wirtz RA - Emerging Infect. Dis. (2008)

Bottom Line: Hoffmann-La Roche Ltd., Basel, Switzerland) because of a growing concern about counterfeit oseltamivir.Both methods were evaluated for variability and selectivity and subsequently applied to batches of oseltamivir products acquired through the Internet.Colorimetric and chromatographic analysis showed all batches of oseltamivir product were within +/-15% of the stated amount of active ingredient.

View Article: PubMed Central - PubMed

Affiliation: Centers for Disease Control and Prevention, Atlanta, GA 30333, USA. mgreen@cdc.gov

ABSTRACT
We developed a colorimetric and chromatographic assay for oseltamivir to assess the authenticity of Tamiflu (F. Hoffmann-La Roche Ltd., Basel, Switzerland) because of a growing concern about counterfeit oseltamivir. The colorimetric assay is quantitative and relies on an extractable colored ion-pair complex of oseltamivir with Congo red or bromochlorophenol blue. The reverse-phase chromatographic assay uses an alkaline mobile phase with UV detection. Both methods were evaluated for variability and selectivity and subsequently applied to batches of oseltamivir products acquired through the Internet. The Congo red test showed greater assay sensitivity, linearity, and accuracy. Colorimetric and chromatographic analysis showed all batches of oseltamivir product were within +/-15% of the stated amount of active ingredient.

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Spectra of Congo red and bromochlorophenol blue complexes with oseltamivir in ethyl acetate.
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Figure 2: Spectra of Congo red and bromochlorophenol blue complexes with oseltamivir in ethyl acetate.

Mentions: Optimal formation of the complex is dependent on the ionization constants (pKa) as well as solubility characteristics for both the basic drug and acidic dye; therefore, optimum complex formation is pH dependent and is characteristic of the analyte being tested. We determined the optimum pH for complex formation between oseltamivir and Congo red to be 4; the optimum pH for bromochlorophenol blue and oseltamivir was 6–7. The absorption spectra for the oseltamivir–Congo red complex (maxima 507 nm) and oseltamivir-bromochlorophenol blue complex (maxima 589 nm) are shown in Figure 2. We evaluated selectivity of the Congo red assay with other commonly used pharmaceuticals. Under the described assay conditions, aspirin, ampicillin, chloroquine, acetaminophen, amoxicillin, ciprofloxacin, and chloramphenicol produced a clear colorless organic phase; quinine and erythromycin showed a very faint rose color. Of the drugs tested for specificity using the bromochlorophenol blue assay, quinine produced a purple color, chloroquine a light blue color, and acetaminophen a faint yellow color. The selectivity of the assay is a function of drug solubility in water as well as pH. Oseltamivir phosphate is highly soluble in water (9). Because aspirin, acetaminophen, amoxicillin, quinine, chloramphenicol, and erythromycin are insoluble or slightly soluble in water, most of the material was eliminated by filtration before the assay was conducted and may have contributed to a colorless ethyl acetate phase. Therefore, filtration is considered necessary because aqueous solubility and a pKa confer selectivity of the colorimetric tests with oseltamivir.


Determination of oseltamivir quality by colorimetric and liquid chromatographic methods.

Green MD, Nettey H, Wirtz RA - Emerging Infect. Dis. (2008)

Spectra of Congo red and bromochlorophenol blue complexes with oseltamivir in ethyl acetate.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2570928&req=5

Figure 2: Spectra of Congo red and bromochlorophenol blue complexes with oseltamivir in ethyl acetate.
Mentions: Optimal formation of the complex is dependent on the ionization constants (pKa) as well as solubility characteristics for both the basic drug and acidic dye; therefore, optimum complex formation is pH dependent and is characteristic of the analyte being tested. We determined the optimum pH for complex formation between oseltamivir and Congo red to be 4; the optimum pH for bromochlorophenol blue and oseltamivir was 6–7. The absorption spectra for the oseltamivir–Congo red complex (maxima 507 nm) and oseltamivir-bromochlorophenol blue complex (maxima 589 nm) are shown in Figure 2. We evaluated selectivity of the Congo red assay with other commonly used pharmaceuticals. Under the described assay conditions, aspirin, ampicillin, chloroquine, acetaminophen, amoxicillin, ciprofloxacin, and chloramphenicol produced a clear colorless organic phase; quinine and erythromycin showed a very faint rose color. Of the drugs tested for specificity using the bromochlorophenol blue assay, quinine produced a purple color, chloroquine a light blue color, and acetaminophen a faint yellow color. The selectivity of the assay is a function of drug solubility in water as well as pH. Oseltamivir phosphate is highly soluble in water (9). Because aspirin, acetaminophen, amoxicillin, quinine, chloramphenicol, and erythromycin are insoluble or slightly soluble in water, most of the material was eliminated by filtration before the assay was conducted and may have contributed to a colorless ethyl acetate phase. Therefore, filtration is considered necessary because aqueous solubility and a pKa confer selectivity of the colorimetric tests with oseltamivir.

Bottom Line: Hoffmann-La Roche Ltd., Basel, Switzerland) because of a growing concern about counterfeit oseltamivir.Both methods were evaluated for variability and selectivity and subsequently applied to batches of oseltamivir products acquired through the Internet.Colorimetric and chromatographic analysis showed all batches of oseltamivir product were within +/-15% of the stated amount of active ingredient.

View Article: PubMed Central - PubMed

Affiliation: Centers for Disease Control and Prevention, Atlanta, GA 30333, USA. mgreen@cdc.gov

ABSTRACT
We developed a colorimetric and chromatographic assay for oseltamivir to assess the authenticity of Tamiflu (F. Hoffmann-La Roche Ltd., Basel, Switzerland) because of a growing concern about counterfeit oseltamivir. The colorimetric assay is quantitative and relies on an extractable colored ion-pair complex of oseltamivir with Congo red or bromochlorophenol blue. The reverse-phase chromatographic assay uses an alkaline mobile phase with UV detection. Both methods were evaluated for variability and selectivity and subsequently applied to batches of oseltamivir products acquired through the Internet. The Congo red test showed greater assay sensitivity, linearity, and accuracy. Colorimetric and chromatographic analysis showed all batches of oseltamivir product were within +/-15% of the stated amount of active ingredient.

Show MeSH