Journal of Chromatography A, 1599 (2019) 136–143
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Journal of Chromatography A, 1599 (2019) 136–143 Contents lists available at ScienceDirect Journal of Chromatography A jo urnal homepage: www.elsevier.com/locate/chroma Development of a design of experiments optimized method for quantification of polysorbate 80 based on oleic acid using UHPLC-MS a,b,c,∗ b,c a,d Julia Puschmann , Dirk-H. Evers , Christel C. Müller-Goymann , b,c Michael E. Herbig a Institut für Pharmazeutische Technologie, TU Braunschweig, Braunschweig, Germany b Almirall Hermal GmbH, Reinbek, Germany c RaDes GmbH, Hamburg, Germany d Center of Pharmaceutical Engineering (PVZ), TU Braunschweig, Braunschweig, Germany a r a t i c l e i n f o b s t r a c t Article history: The aim was to develop a straightforward UHPLC-MS quantification method for polysorbate 80 using Received 24 December 2018 oleic acid as surrogate marker, which was the commonest substance within the emulsifier. However, Received in revised form 2 April 2019 hydrolysis of polysorbate 80 and subsequent analysis of fatty acids revealed a co-elution of oleic acid Accepted 7 April 2019 and an isomer while all the other fatty acids were successfully separated by varying retention times Available online 8 April 2019 and mass-to-charge ratios. For identification and separation of the isomer a derivatization method was evaluated. Oxidation to the corresponding dihydroxystearic acids with potassium permanganate resulted Keywords: in peak separation of cis/trans and structural isomers of the 18:1 fatty acids. Hydrolyzed and derivatized Polysorbate 80 2 polysorbate 80 was quantified indirectly in the range of 0.046–5.83 g/mL (R > 0.997) with a limit of Design of experiments Quantification detection of 11.4 ng/mL. Quantification of polysorbate 80 using oleic acid as a surrogate marker showed Oleic acid good reproducibility and linearity. As all isomers of the 18:1 fatty acids were successfully separated, the UHPLC-MS previously co-eluting peak was identified as elaidic acid and was found as a component in the mixture of Peak separation the emulsifier polysorbate 80. Additionally, cis-vaccenic acid was separated as a second co-eluting isomer. Cis/trans separation Therefore, derivatization led to successful chromatographical separation of cis/trans and structural 18:1 fatty acid isomers. © 2019 Elsevier B.V. All rights reserved. 1. Introduction from different suppliers were compared [3]. The byproducts of the synthesis such as polyethylene glycol have significant impact on The emulsifier polysorbate 80 is often used in a wide range those properties. Therefore, quantification of emulsifiers in aque- of pharmaceutical formulations such as protein formulations and ous phases is an important aspect for understanding interactions emulsions. In water containing systems, polysorbate 80 is added to within formulations. increase the solubility of active pharmaceutical ingredients (API) So far, the composition of polysorbate 80 regarding the fatty in the aqueous phase [1], typically in a concentration dependent acids is mostly measured via gas chromatography of the methylated manner. As the critical micelle concentration (CMC) is 13 g/mL fatty acids [4,5], which demands the hydrolysis and derivatization [2], quantification of polysorbate 80 is required at concentrations of the emulsifier. To check the usage of state-of-the-art techniques below the CMC for calculations of the impact of micelle-free solu- for analytical methods, they should undergo continuous life-cycle tions on API partitioning. In previous studies, various properties management to ensure the application of the best method for the (CMC, cloud point, micellar molecular weight) of polysorbate 80 task [6]. Keeping this in mind, various methods for polysorbate 80 analysis have been compared. A simple quantification of polysor- bate 80 hydrolyzed to oleic acid is performed with a HPLC and a spectrometric detector [7] but needs 6 h for hydrolysis. Polysor- ∗ Corresponding author at: RaDes GmbH, Schnackenburgallee 114, 22525 Ham- bate 80 can also be quantified by the ethylene oxide chain content burg, Germany. as those chains react with cobalt thiocyanate to a blue complex, E-mail address: [email protected] (J. Puschmann). https://doi.org/10.1016/j.chroma.2019.04.015 0021-9673/© 2019 Elsevier B.V. All rights reserved. J. Puschmann et al. / J. Chromatogr. A 1599 (2019) 136–143 137 which can be detected spectrometrically in concentrations above 2. Material and methods 10 g/mL [8]. As polyethylene glycol is frequently used within pharmaceutical formulations, this method is often not applica- 2.1. Material ble without further calculations as the added polyethylene glycol would undergo the reaction as well. The combinations HPLC-CAD Polysorbate 80 Ph. Eur. quality was supplied by Croda (charged aerosol detector) or HPLC-ELSD (evaporative light scatter- GmbH (Nettetal, Germany, batches: 2607TD1683, 2503TP490, ing detector) also allow quantification of polysorbate 80 as a single 1403UP2005). Acetonitrile LC–MS grade and acetone HPLC grade peak at low concentrations above 5 g/mL [9–12]. The variation of were from Th. Geyer (Renningen, Germany). Ammonium acetate in analysis methods (fluorescence micelle assay, mixed-mode HPLC LC–MS quality was ordered from Promochem (Wesel, Germany). coupled to CAD or ELSD) shows comparable results regarding the Potassium permanganate and sodium hydroxide were ordered content of polysorbate 80 but varies in the detection of degradation from Merck KGaA (Darmstadt, Germany) in Ph. Eur. quality. products [13]. Citrate buffer 0.1 M pH 5 was prepared with citric acid mono- As the mentioned methods are not sufficiently sensitive for hydrate Ph. Eur. quality (Merck KGaA, Darmstadt, Germany), most formulations with rather low polysorbate 80 concentrations, sodium citrate dihydrate Ph. Eur. quality (Biesterfeld AG, Ham- a new method shall be evaluated with a UHPLC coupled to a single burg, Germany) and purified water Ph. Eur. (DEWA Engineering mass spectrometer (QDa) using a surrogate marker. Polysorbate und Anlagenbau GmbH, Vienenburg, Germany). Purified water in 80 consists of mixtures of mono- and diesters of fatty acids and the quality of water for chromatography R (Ph. Eur.) for UHPLC anal- polyethylene glycol chains of different lengths [14–16], resulting ysis was obtained with a Maxima-apparatus from ELGA LabWater in a difficult quantification of the whole molecule as the composi- (Celle, Germany) and purified water in LC–MS quality was ordered tion varies from batch to batch [17]. The European Pharmacopeia from Carl Roth GmbH + Co. KG (Karlsruhe, Germany). (Ph. Eur.) demands a concentration of more than 58% oleic acid [4], The following fatty acids were purchased from Sigma Aldrich therefore, oleic acid is chosen as the marker substance. Within chro- Chemie GmbH (Taufkirchen, Germany): linoleic acid >99%, palmitic matographic analysis, it is important to include a washing step with acid >99%, stearic acid >99%, myristic acid >98%, oleic acid ((Z)- high organic phase concentrations to prevent changes in retention octadec-9-enoic acid) >99%, palmitoleic acid >98.5%, linolenic acid properties of columns [18]. As the European Pharmacopeia also >99%, elaidic acid ((E)-octadec-9-enoic acid) >99%, petroselinic acid describes the presence of further fatty acids (myristic acid, palmitic ((Z)-octadec-6-enoic acid) >99%, cis-vaccenic acid ((Z)-octadec- acid, palmitoleic acid, stearic acid, linoleic acid, linolenic acid) to 11-enoic acid) >97%, trans-vaccenic acid ((E)-octadec-11-enoic a certain degree [4], the separation of those shall be obtained by acid) >99%. Petroselaidic acid ((E)-octadec-6-enoic acid) >99% was using the mass spectrometer to selectively detect them by their ordered from Larodan AB (Solna, Sweden). mass-to-charge (m/z) ratios. During the method development a co-eluting peak with the 2.2. Chromatographic conditions for UHPLC analysis with QDa same m/z as oleic acid was found. For the separation of the proposed detection isomers, silver-ion thin-layer chromatography or HPLC followed by gas chromatography was applied in earlier studies [19–23]. As not The analysis was performed with a UHPLC system (ACQUITY TM TM all isomers were fractionated with this method, the DoE (Design UPLC system, Waters GmbH, Eschborn, Germany) using a BEH of Experiments) approach with UHPLC-MS should be followed. The 1.7 m, 2.1 × 50 mm column (Waters GmbH, Eschborn, Germany). separation of various cis-, trans- and the structural 18:1 fatty acid Eluents were acetonitrile (B) and aqueous ammonium acetate isomers should be performed within one run. Therefore, the deriva- 10 mM (A) at a flowrate of 0.8 mL/min. Injection volume was 10 L tization to UV-detectable substances and separation of structural and injections were performed in triplicate. Peaks were detected isomers according to [24–26] is not considered being sufficient. with a single mass spectrometer (QDa, Waters GmbH, Eschborn, Derivatization through oxidation of oleic acid results in mono- Germany, mass range 30 to 1250 m/z). Negative scan mode with a and dihydroxystearic acids using varying oxidizing agents such as cone voltage of 15 V was used. The sampling rate was 10 points per ozone [27], selenium dioxide/tert-butylhydroperoxide [28], hydro- second. The substances were measured in single ion mode. Cap- gen peroxide [29]. For the method development in this study, a illary voltage was set to -0.5 kV. The probe temperature was held ◦ long-known method for derivatization of double bonds with potas- at 600 C. The gas flows were standardized by Waters GmbH, the sium permanganate according to Lapworth et al. [30] is chosen. As consumption rate of nitrogen was 1200 L/h. The mentioned m/z val- − freezing and heating of fatty acids result in an isomerization from ues represented the loss of a proton [M−H] . The m/z values were: the cis- into the trans-form according to [31,32], the reaction is per- m/z 227.2 (myristic acid), m/z 253.2 (palmitoleic acid), m/z 255.2 formed at room temperature to avoid further transformations.