Michael L. Trehy

ANALYSIS OF ELECTRONIC CIGARETTE CARTRIDGES, REFILL SOLUTIONS, AND SMOKE FOR NICOTINE AND NICOTINE RELATED IMPURITIES

The objective of this study was to determine nicotine and the nicotine related impurities, that is, cotinine, myosmine, anatabine, anabasine, and β-nicotyrine, in electronic cigarette cartridges, the liquid used to fill the cartridges, and from smoke generated using the electronic cigarette devices. An HPLC method was validated for the determination. Samples of nicotine containing products were purchased via the internet from NJOY, Smoking Everywhere, CIXI, and Johnson Creek. Electronic cigarette devices were purchased from NJOY, Smoking Everywhere, and CIXI. The results from the testing found that (1) the nicotine content labeling was not accurate with some manufacturers, (2) nicotine is present in the “smoke” from electronic cigarettes, and (3) nicotine related impurities contents in cartridges and refills were found to vary by electronic cigarette manufacturer.

Identification of amino-tadalafil and rimonabant in electronic cigarette products using high pressure liquid chromatography with diode array and tandem mass spectrometric detection.

A high-pressure liquid chromatography-diode array detection and multi-mode ionization tandem mass spectrometry (HPLC-DAD-MMI-MS/MS) method was used to identify amino-tadalafil and rimonabant in electronic cigarette (e-cigarette) cartridges. Amino-tadalafil is a drug analogue of the commercially approved Cialis™ (i.e. tadalafil). Rimonabant is a drug that was, at one time, approved for weight loss in Europe (although approval has been retracted), but not in the United States. In addition, poor quality control over the e-cigarette products analyzed here is shown by the presence of nicotine in products labeled as containing no nicotine or by the presence of significant amounts of rimonabant oxidative degradant in e-cigarette products containing rimonabant. Identification was accomplished by comparing the retention time of relevant peaks in the sample with those of standard compounds, in addition to comparison of the UV spectra, mass spectra and/or product ion mass spectra.

Analysis of heparin sodium by SAX/HPLC for contaminants and impurities.

A chromatographic method was developed for the detection and quantification of the contaminant oversulfated chondroitin sulfate (OSCS) and the impurity dermatan sulfate in heparin active pharmaceutical ingredient (API). The HPLC analysis of heparin is carried out using a polymer-based strong anion exchange (SAX) column with gradient elution from 0.125 M sodium chloride to 2.5M sodium chloride buffered mobile phase. The limit of detection (LOD) and limit of quantitation (LOQ) for the contaminant OSCS in heparin were determined to be 0.03% and 0.1%, respectively. The LOD and LOQ for dermatan sulfate, an impurity in heparin sulfate, were determined to be 0.1% and 0.8%, respectively. This manuscript is not a policy document and is not intended to replace either of the methods (capillary electrophoresis and NMR) currently required by the FDA.

Analysis of crude heparin by 1H NMR, capillary electrophoresis, and strong-anion-exchange-HPLC for contamination by over sulfated chondroitin sulfate

We previously published a strong-anion-exchange-high performance liquid chromatography (SAX-HPLC) method for the detection of the contaminant over sulfated chondroitin sulfate (OSCS) in heparin sodium active pharmaceutical ingredient (API). While APIs have been processed to remove impurities, crude heparins contain insoluble material, chondroitin sulfates, heparan sulfate, and proteins that may interfere with the recovery and measurement of OSCS. We examined 500MHz (1)H NMR, capillary electrophoresis (CE), and SAX-HPLC to quantify OSCS in crude heparin. Using our standard API protocol on OSCS spiked crude heparin samples; we observed a weight percent LOD and LOQ for the NMR approach of 0.1% and 0.3%, respectively, while the SAX-HPLC method gave values of 0.03% and 0.09%, respectively. CE data was not amenable to quantitative measurement of OSCS in crude heparin. We developed a modified HPLC sample preparation protocol using crude dissolved at the 100mg/mL level with a 2.5M NaCl solution. This SAX-HPLC approach gave a weight percent LOD of 0.02% and a LOQ of 0.07% and had better performance characteristics than that of the protocol used for APIs.

Determination of galactosamine impurities in heparin samples by multivariate regression analysis of their 1H NMR spectra

Heparin, a widely used anticoagulant primarily extracted from animal sources, contains varying amounts of galactosamine impurities. Currently, the United States Pharmacopeia (USP) monograph for heparin purity specifies that the weight percent of galactosamine (%Gal) may not exceed 1%. In the present study, multivariate regression (MVR) analysis of 1H NMR spectral data obtained from heparin samples was employed to build quantitative models for the prediction of %Gal. MVR analysis was conducted using four separate methods: multiple linear regression, ridge regression, partial least squares regression, and support vector regression (SVR). Genetic algorithms and stepwise selection methods were applied for variable selection. In each case, two separate prediction models were constructed: a global model based on dataset A which contained the full range (0–10%) of galactosamine in the samples and a local model based on the subset dataset B for which the galactosamine level (0–2%) spanned the 1% USP limit. All four regression methods performed equally well for dataset A with low prediction errors under optimal conditions, whereas SVR was clearly superior among the four methods for dataset B. The results from this study show that 1H NMR spectroscopy, already a USP requirement for the screening of contaminants in heparin, may offer utility as a rapid method for quantitative determination of %Gal in heparin samples when used in conjunction with MVR approaches.

Characterization of currently marketed heparin products: Key tests for LMWH quality assurance ☆

During the 2007-2008 heparin crisis it was found that the United States Pharmacopeia (USP) testing monograph for heparin sodium or low molecular weight heparins did not detect the presence of the contaminant, oversulfated chondroitin sulfate (OSCS). In response to this concern, new tests and specifications were developed by the Food and Drug Administration (FDA) and USP and put in place to detect not only the contaminant OSCS, but also to improve assurance of quality and purity of these drug products. The USP monographs for the low molecular weight heparins (LMWHs) approved for use in the United States (dalteparin, tinzaparin and enoxaparin) are also undergoing revision to include many of the same tests used for heparin sodium, including; one-dimensional (1D) 500 MHz (1)H NMR, SAX-HPLC, percent galactosamine in total hexosamine and anticoagulation time assays with purified Factor IIa or Factor Xa. These tests represent orthogonal approaches for heparin identification, measurement of bioactivity and for detection of process impurities or contaminants in these drug products. Here we describe results from a survey of multiple lots from three types of LMWHs in the US market which were collected after the 2009 heparin sodium monograph revision. In addition, innovator and generic versions of formulated enoxaparin products purchased in 2011 are compared using these tests and found to be highly similar within the discriminating power of the assays applied.

Class Modeling Analysis of Heparin 1H NMR Spectral Data Using the Soft Independent Modeling of Class Analogy and Unequal Class Modeling Techniques

To differentiate heparin samples with varying amounts of dermatan sulfate (DS) impurities and oversulfated chondroitin sulfate (OSCS) contaminants, proton NMR spectral data for heparin sodium active pharmaceutical ingredient samples from different manufacturers were analyzed using multivariate chemometric techniques. A total of 168 samples were divided into three groups: (a) Heparin, [DS] ≤ 1.0% and [OSCS] = 0%; (b) DS, [DS] > 1.0% and [OSCS] = 0%; (c) OSCS, [OSCS] > 0% with any content of DS. The chemometric models were constructed and validated using two well-established methods: soft independent modeling of class analogy (SIMCA) and unequal class modeling (UNEQ). While SIMCA modeling was conducted using the entire set of variables extracted from the NMR spectral data, UNEQ modeling was combined with variable reduction using stepwise linear discriminant analysis to comply with the requirement that the number of samples per class exceed the number of variables in the model by at least 3-fold. Comparison of the results from these two modeling approaches revealed that UNEQ had greater sensitivity (fewer false positives) while SIMCA had greater specificity (fewer false negatives). For Heparin, DS, and OSCS, respectively, the sensitivity was 78% (56/72), 74% (37/50), and 85% (39/46) from SIMCA modeling and 88% (63/72), 90% (45/50), and 91% (42/46) from UNEQ modeling. Importantly, the specificity of both the SIMCA and UNEQ models was 100% (46/46) for Heparin with respect to OSCS; no OSCS-containing sample was misclassified as Heparin. The specificity of the SIMCA model (45/50, or 90%) was superior to that of the UNEQ model (27/50, or 54%) for Heparin with respect to DS samples. However, the overall prediction ability of the UNEQ model (85%) was notably better than that of the SIMCA model (76%) for the Heparin vs DS vs OSCS classes. The models were challenged with blends of heparin spiked with nonsulfated, partially sulfated, or fully oversulfated chondroitin sulfate A, dermatan sulfate, or heparan sulfate at the 1.0, 5.0, and 10.0 wt % levels. The results from the present study indicate that the combination of (1)H NMR spectral data and class modeling techniques (viz., SIMCA and UNEQ) represents a promising strategy for assessing the quality of commercial heparin samples with respect to impurities and contaminants. The methodologies show utility for applications beyond heparin to other complex products.

Combining 1H NMR spectroscopy and chemometrics to identify heparin samples that may possess dermatan sulfate (DS) impurities or oversulfated chondroitin sulfate (OSCS) contaminants

Heparin is a naturally produced, heterogeneous compound consisting of variably sulfated and acetylated repeating disaccharide units. The structural complexity of heparin complicates efforts to assess the purity of the compound, especially when differentiating between similar glycosaminoglycans. Recently, heparin sodium contaminated with oversulfated chondroitin sulfate A (OSCS) has been associated with a rapid and acute onset of an anaphylactic reaction. In addition, naturally occurring dermatan sulfate (DS) was found to be present in these and other heparin samples as an impurity due to incomplete purification. The present study was undertaken to determine whether chemometric analysis of these NMR spectral data would be useful for discrimination between USP-grade samples of heparin sodium API and those deemed unacceptable based on their levels of DS, OSCS, or both. Several multivariate chemometric methods for clustering and classification were evaluated; specifically, principal components analysis (PCA), partial least squares discriminant analysis (PLS-DA), linear discriminant analysis (LDA), and the k-nearest-neighbor (kNN) method. Data dimension reduction and variable selection techniques, implemented to avoid over-fitting the training set data, markedly improved the performance of the classification models. Under optimal conditions, a perfect classification (100% success rate) was attained on external test sets for the Heparin vs OSCS model. The predictive rates for the Heparin vs DS, Heparin vs [DS+OSCS], and Heparin vs DS vs OSCS models were 89%, 93%, and 90%, respectively. In most cases, misclassifications can be ascribed to the similarity in NMR chemical shifts of heparin and DS. Among the chemometric methods evaluated in this study, we found that the LDA models were superior to the PLS-DA and kNN models for classification. Taken together, the present results demonstrate the utility of chemometric methods when applied in combination with (1)H NMR spectral analysis for evaluating the quality of heparin APIs.

Determination of the enantiomeric purity of epinephrine by HPLC with circular dichroism detection

ABSTRACT Several hundred drug substances approved by the U.S. Food and Drug Administration are chiral molecules. For the enantiomeric purity assessment, current practice is to develop separation techniques using chiral columns or mobile phase modifiers to separate enantiomers before detection. An alternative approach is to use currently accepted HPLC assay methods and use chiral-specific detectors to confirm whether the correct enantiomer is present. In this paper, adding a circular dichroism (CD) detector to an achiral HPLC method from the US Pharmacopeia (USP) is shown to be amenable for the determination of the enantiomeric purity of epinephrine, a substance used to treat anaphylaxis. This HPLC-UV-CD approach was able to detect the inactive D-(+) enantiomer at 1% of the total epinephrine composition. The linearity, accuracy, and precision of HPLC-UV-CD were evaluated and compared to analyses using a chiral HPLC method. Additionally, an epinephrine drug product was analyzed for assay (concentration) and enantiomeric purity. The results from achiral and chiral methods were identical within the experimental error. Overall, achiral chromatography performed using a USP method with CD detection may serve as a general means of determining chiral drug enantiomer purity and avoids the need for the development of additional chiral-specific methods for each individual drug. GRAPHICAL ABSTRACT

Enantiomeric impurity analysis using circular dichroism spectroscopy with United States Pharmacopeia liquid chromatographic methods

HighlightsOver 300 chiral drug substances lack United States Pharmacopeia methods to determine enantiomeric purity.Current approaches for the development of enantiomeric methods utilize specialized materials and equipment, and are not transferrable to other compounds.Circular dichroism detection following liquid chromatographic analysis can act as a general detection strategy for a variety of drug compounds.Adoption of this strategy avoids the need to develop and perform specialized enantiomeric methods. ABSTRACT Over 300 chiral drug substances lack official United States Pharmacopeia (USP) methods for the enantiomeric purity determination. Because enantiomeric analysis typically requires specialized methods for each drug compound, developing protocols for each of these 300+ substances would be an expensive and laborious endeavor. Alternatively, if a detector capable of determining the enantiomeric composition without chiral separation could be used with certain drug compounds, this could be implemented relatively rapidly into official testing monographs. Circular dichroism (CD) detection following HPLC (HPLC‐CD) has been proposed for this purpose but studies performed thus far have not prioritized its compatibility with validated regulatory methods. In this study, HPLC‐CD was evaluated for enantiomeric purity determinations of 13 drug substances using HPLC methods consistent with assay protocols described in United States Pharmacopeia (USP) monographs. Of these selected substances, three (sitagliptin, timolol, and levalbuterol) showed no CD activity and one other (levofloxacin) could not be analyzed due to incompatibility of the mobile phase with the CD detector. For the remaining 9 substances, method validation was performed to determine the linearity, accuracy, precision and limits of quantitation of enantiomer impurities, which was compared to limits established by USP. It was found that enantiomeric impurities for four substances (pramipexole, levocetirizine, (S)‐citalopram, and tolterodine) could be quantitatively determined at levels suitable to USP specifications. This analysis demonstrated that HPLC‐CD does provide an effective enantiomeric characterization strategy for compatible chiral compounds, and can be implemented quickly and economically compared to traditional column‐dependent chiral separation or derivatization methods.