Qinggang Wang

Bristol-Myers Squibb, New York, New York, United States

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Publications (4)6.68 Total impact

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    ABSTRACT: Drug degradation that occurs in HPLC analysis, during either sample preparation or chromatographic separation, can greatly impact method robustness and result accuracy. In this work, we report a case study of drug dimerization in HPLC analysis where proximate causes were attributed to either the LC columns or the HPLC instrument. Solution stress studies indicated that the same pseudo-dimeric degradants could also be formed rapidly when the compound was exposed to certain oxidative transition metal ions, such as Cu(II) and Fe(III). Two pseudo-dimeric degradants were isolated from transition metal stressed samples and their structures were elucidated. A degradation pathway was proposed, whereby the degradation was initiated through transition metal-induced single electron transfer oxidation. Further studies confirmed that the dimerization was induced by trace transition metals in the HPLC flow path, which could arise from either the stainless steel frits in the LC column or stainless steel tubing in the HPLC instrument. Various procedures to prevent transition metal-induced drug degradation were explored, and a general strategy to mitigate such risks is briefly discussed. Copyright © 2015 Elsevier B.V. All rights reserved.
    Journal of pharmaceutical and biomedical analysis 04/2015; 111:288-296. DOI:10.1016/j.jpba.2015.04.005 · 2.83 Impact Factor
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    ABSTRACT: Peak tailing of phosphate prodrugs in acidic mobile phases was thoroughly investigated. The results indicated that both metal-phosphate interactions and silanophilic interactions contributed to the observed peak tailing. Column pretreatment with phosphate buffers was demonstrated to be an effective and robust approach in suppressing metal-phosphate interaction. Silanophilic interactions, such as hydrogen bonding interactions between protonated isolated silanol groups and partially deprotonated phosphate groups were mobile phase pH dependent. The combination of column pretreatment and volatile low pH mobile phase buffers can be used to mitigate peak tailing issues in developing MS compatible RPLC methods for phosphate prodrugs. The use of non-endcapped columns should be avoided in RPLC analysis for phosphate prodrugs due to large amount of residual silanol groups in the stationary phases.
    Journal of Pharmaceutical and Biomedical Analysis 05/2014; 98C:247-252. DOI:10.1016/j.jpba.2014.05.027 · 2.83 Impact Factor
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    ABSTRACT: Illustration of silanophilic interactions of phosphate prodrugs with HPLC column residual silanols in different pH mobile phases. R represents a parent compound moiety. H-bonding formation in the pH range of 2–5 contributes to the phosphate prodrug peak tailing discussed in this paper.
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    ABSTRACT: The regeneration of ion-pairing reagent distribution on liquid chromatography columns after gradient elution has been well recognized as the cause for long column equilibration time, a major drawback associated with gradient elution reverse phase ion-pair chromatography. To date, the majority of studies have focused on optimizing the separation conditions to shorten the equilibration time. There is limited understanding of the ion-pairing reagent distribution process between the mobile phase and stationary phase in the course of gradient elution, and subsequent column re-equilibration. The focus of this work is to gain a better understanding of this process. An ion-pair chromatographic system, equipped with a YMC ODS C(18) column and a mobile phase containing tetrabutylammonium (TBA) hydroxide as the ion-pairing reagent, was used in the study. The TBA distribution profile was established by measuring its concentration in the eluent fractions collected during the gradient cycle using different column equilibration times with an ion chromatographic method. Furthermore, the analyte retention time was evaluated as the function of the column equilibration time and TBA concentration in the mobile phase. The column equilibration and its impact on the method robustness will also be discussed.
    Journal of chromatographic science 11/2011; 49(10):825-31. DOI:10.1093/chrsci/49.10.825 · 1.03 Impact Factor