Determination of EDTA in vancomycin by liquid chromatography with absorbance ratioing for peak identification

Exploitation of the size-exclusion effect of reversed-phase high performance liquid chromatography for the direct analysis of diethylene triamine pentaacetic acid in therapeutic monoclonal antibody formulations

Monoclonal antibodies (mAb) are being widely studied for the treatment of cancers and other diseases. The mAb is typically in a solution formulation and administered as an intravenous infusion. Ready-to-use solutions are favored for their clinical convenience but they can potentially suffer from a shorter shelf life due to accelerated rates of some forms of degradation such as oxidation, relative to lyophilized formulations. To improve stability, the chelating agent diethylene triamine pentaacetic acid (DTPA) is often used at very low concentrations in biologics formulations to prevent oxidation induced by metal ions. Because of its low concentration and susceptibility to changes in concentration during stability study or processing, the measurement of DTPA levels during formulation and process development is critical. In response to this need we developed a platform reversed-phase HPLC method that allows for the rapid and direct determination of DPTA concentrations which does not require the prior removal of mAbs in formulation samples. The method exploits the "size exclusion effect" of C18 columns with narrow pore sizes (90-120Å) to elute large mAb at the void volume, enabling direct injections of mAb samples for quantitation of DTPA. The method was found to be suitable for the analysis of DTPA in the range of 2-20μg/mL across multiple drug formulations containing different therapeutic mAb and antibody drug conjugates. The method was successfully validated for specificity, precision, accuracy, linearity, and robustness.

Ion-pairing HPLC methods to determine EDTA and DTPA in small molecule and biological pharmaceutical formulations

Ion-pairing high-performance liquid chromatography–ultraviolet (HPLC–UV) methods were developed to determine two commonly used chelating agents, ethylenediaminetetraacetic acid (EDTA) in Abilify® (a small molecule drug with aripiprazole as the active pharmaceutical ingredient) oral solution and diethylenetriaminepentaacetic acid (DTPA) in Yervoy® (a monoclonal antibody drug with ipilimumab as the active pharmaceutical ingredient) intravenous formulation. Since the analytes, EDTA and DTPA, do not contain chromophores, transition metal ions (Cu²⁺, Fe³⁺) which generate highly stable metallocomplexes with the chelating agents were added into the sample preparation to enhance UV detection. The use of metallocomplexes with ion-pairing chromatography provides the ability to achieve the desired sensitivity and selectivity in the development of the method. Specifically, the sample preparation involving metallocomplex formation allowed sensitive UV detection. Copper was utilized for the determination of EDTA and iron was utilized for the determination of DTPA. In the case of EDTA, a gradient mobile phase separated the components of the formulation from the analyte. In the method for DTPA, the active drug substance, ipilimumab, was eluted in the void. In addition, the optimization of the concentration of the ion-pairing reagent was discussed as a means of enhancing the retention of the aminopolycarboxylic acids (APCAs) including EDTA and DTPA and the specificity of the method. The analytical method development was designed based on the chromatographic properties of the analytes, the nature of the sample matrix and the intended purpose of the method. Validation data were presented for the two methods. Finally, both methods were successfully utilized in determining the fate of the chelates.

Simultaneous determination of DTPA, EDTA, and NTA by UV–visible spectrometry and HPLC

In this study, UV-visible spectrophotometry (UV-Vis) and high-performance liquid chromatography (HPLC) were used for simultaneous analysis of chelating agents diethylenetriamine pentaacetic acid (DTPA), ethylenediamine tetraacetic acid (EDTA), and nitrilotriacetic acid (NTA), as their metal chelates in dishwashing detergents, natural waters, and pulp mill water. The total amounts of the chelating agents in dishwashing detergents were verified by potentiometric titration with Fe(III) solution. Nickel(II) chelates were determined by UV-Vis and iron(III)chelates by HPLC and titration. Recoveries of DTPA, EDTA, and NTA from a standard mixture of analytes by UV-Vis were 107+/-7, 101+/-12 and 94+/-13%, respectively, and the recovery of the total amount of complexing agents was 99+/-4%. The limits of detection for DTPA, EDTA, and NTA were 667, 324, and 739 micromol L(-1), respectively. In HPLC measurements the optimized mobile phase contained 0.03 mol L(-1) sodium acetate, 0.002 mol L(-1) tetrabutylammonium bromide, and 5% methanol at pH 3.15 and the detection was by UV-Vis detection at 254 nm. All three complexing agents could be separated from each other in a simultaneous analysis in less than 5 min. The limits of detection were 0.34, 0.27, and 0.62 micromol L(-1) for DTPA, EDTA, and NTA, respectively. The total amounts of the analytes measured in the dishwashing detergents by the three techniques were found to be highly comparable (ANOVA: F=0.04, P=0.96). R(2) values were 0.99 for EDTA, 0.99 for NTA, and 0.99 for all the results when UV-Vis and HPLC determinations were compared using regression lines. The UV-Vis and HPLC methods were proved to be viable also for analyses of natural and pulp mill waters. The absence of matrix interferences was verified by the standard addition technique.

The control of nitrilotriacetic acid in edetic acid and its salts by liquid chromatography

Two liquid chromatographic methods have been developed and validated for the determination of nitrilotriacetic acid (NTA) in edetic acid (EDTA) and its salts. In one method NTA and EDTA are separated on a polymer column without pretreatment, and are detected amperometrically using a glassy-carbon electrode. In the other method NTA and EDTA are complexed with ferric ions and the complexes separated on a porous graphite carbon stationary phase with ultraviolet detection at 215 nm. Both methods were sufficiently selected and sensitive to allow the control of NTA (0.1% m/m) in sample of EDTA and its salts.

Determination of ethylenediamine tetraacetic acid in injection forms by ion-pair chromatography

A high performance liquid chromatographic method was developed for the determination of ethylenediamine tetraacetic acid (EDTA) in injection forms. The method consists of direct extraction of the samples with ethyl acetate; the organic layers were evaporated to dryness and further diluted to a 0.025% (w/v) copper nitrate in order to achive the formation of the EDTA-copper solution complex. The chromatographic separation was performed on a C8 Hypersil column. The mobile phase consisted of a mixture of acetonitrile-0.015 M tetrabutylammonium hydroxide (10:90, v/v), (pH* 7.0) pumped at a flow rate of 1.5 ml min(-1). The UV detector was operated at 300 nm. Correlation coefficients of the calibration graphs were better than 0.9995, relative standard deviation was less than 2.5%. Detection limit of EDTA was found to be 1.97 microg ml(-1).

Polarographic determination of EDTA in certain pharmaceutical dosage forms

A highly sensitive polarographic method was developed for the determination of EDTA added as a preservative in certain pharmaceutical preparations. The method involved chelation with Eu(III) followed by polarographic measurement of the chelate formed. A well-defined cathodic wave was developed in Britton-Robinson buffers over the pH range 2-12. The wave was characterized as being quasi-reversible and diffusion controlled. The current-concentration relationship was found to be rectilinear over the ranges 8-160 and 2-120 micrograms ml-1, using DCt and DPP modes, respectively, with limit of detection of 0.1 microgram ml-1 using the DDP technique. The mechanism of the electrode reaction was verified. The proposed method was applied for the determination of EDTA in certain pharmaceutical dosage forms, and the results obtained were in agreement with those obtained by a reference method.

A novel HPLC method for determination of EDTA in a cataract inhibiting ophthalmic drug

A novel HPLC method for determination of EDTA in a cataract inhibiting ophthalmic drug product has been developed. In this method EDTA was converted to Cu(II)EDTA complex, using Cu + 2 containing mobile phase, after injection into the chromatographic system. This allowed complexation of EDTA with Cu + 2 without interference from formulation ingredients. The Cu(II)EDTA complex was separated from drug substance, impurities, degradants and other formulation excipients by a 250 x 4.1 mm anion exchange column and detected at UV wavelength 250 nm. The mobile phase consisted of 2 mM cupric nitrate, 11 mM nitric acid, and 25% (v/v) acetonitrile at pH 3.0. This stability indicating assay has been validated and shown to be specific, linear, precise, accurate and rugged for routine EDTA analysis.