Stable isotopic composition of the active pharmaceutical ingredient (API) naproxen

Forensic investigation of falsified antimalarials using isotope ratio mass spectrometry: a pilot investigation

We explored whether isotope ratio mass spectrometry (IRMS) is useful to investigate the origin of falsified antimalarials. Forty-four falsified and genuine antimalarial samples (artesunate, artemether-lumefantrine, dihydroartemisinin-piperaquine and sulphamethopyrazine-pyrimethamine) were analyzed in bulk for carbon (C), nitrogen (N), and oxygen (O) element concentrations and stable isotope ratios. The insoluble fraction ("starch") was extracted from 26 samples and analyzed. Samples of known geographical origin maize, a common source of excipient starch, were used to produce a comparison dataset to predict starch source. In both an initial (n = 18) and a follow-on set of samples that contained/claimed to contain artesunate/artemether (n = 26), falsified antimalarials had a range of C concentrations less than genuine comparator antimalarials and δ13C values higher than genuine comparators. The δ13C values of falsified antimalarials suggested that C4 plant-based organic material (e.g., starch derived from maize) had been included. Using the known-origin maize samples, predictions for growth water δ18O values for the extracted "starch" ranged from - 6.10 to - 1.62‰. These findings suggest that IRMS may be a useful tool for profiling falsified antimalarials. We found that C4 ingredients were exclusively used in falsified antimalarials versus genuine antimalarials, and that it may be possible to predict potential growth water δ18O values for the starch present in falsified antimalarials.

Multidimensional isotope analysis of carbon, hydrogen, and oxygen as a tool for traceability of lactose in drug products

Lactose is one of the most commonly used pharmaceutical excipients. Depending on manufactures, the properties of lactose are very different, which could impact the pharmacokinetic behavior of drug products. Therefore, it is very important to trace the origin of pharmaceutical lactose in drug products which is valuable for prescription analysis. In this study, the carbon, hydrogen and oxygen isotope ratios (δ¹³C, δ²H and δ¹⁸O) of thirty-four lactose from seven manufacturers were analyzed by elemental analysis-stable isotope ratio mass spectrometry (EA-IRMS). One-way analysis of variance (ANOVA) and Duncan's test indicated significant differences in isotope ratios of lactose from different origins. To identify the lactose manufacturer, a discrimination model was generated through linear discriminant analysis (LDA). Based on this model, the manufacturers of lactose used in three drug products were successfully identified. Our results suggested that the multidimensional analysis of δ¹³C, δ²H and δ¹⁸O of lactose provided a fast and effective method to trace the lactose manufacturer. In conclusion, this method can be used to analyze the prescription of the drug product quickly, which could speed up the development of generic drug product.

Importance of Utilizing Natural Isotopologue Transitions in Expanding the Linear Dynamic Range of LC-MS/MS Assay for Small-Molecule Pharmacokinetic Sample Analysis - A mini-review

Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is a widely used quantitative method in small-molecule pharmacokinetic sample analysis. The linear dynamic range of mass analyzers, typically spanning 3 orders of magnitude, is usually insufficient for this purpose. Utilization of multiple isotopologues has been proposed as a compelling approach to expand the linear dynamic range of LC-MS/MS assays, particularly when the detector is saturated. Isotopologues are a statistical mixture of molecules of the same compound but of different exact masses due to the presence of natural chemical isotopes. While the concept of isotopologues is widely recognized in large-molecule bioanalysis and small-molecule metabolite profiling, it has not been commonly implemented in small-molecule targeted quantification. To increase the awareness of the value of isotopologues in small-molecule LC-MS/MS analysis, this minireview provides the basis of isotopologue distribution in MS/MS and summarizes published studies as well as our own experience in utilizing multiple isotopologues to expand the linear dynamic range of small-molecule LC-MS/MS assays. Considering that utilizing natural isotopologue transitions in the LC-MS/MS assays represents an easy, straightforward, and robust way to expand the linear dynamic range, we believe this method deserves wide application in small-molecule pharmacokinetic sample analysis and can particularly benefit people working in pharmacokinetic labs as well as the GLP bioanalytical labs in pharmaceutical industry.

C & N isotope analysis of diclofenac to distinguish oxidative and reductive transformation and to track commercial products

Although diclofenac is frequently found in aquatic systems, its degradability in the environment remains imperfectly understood. On the one hand, evidence from concentration analysis alone is inconclusive if an unknown hydrology impedes a distinction between degradation and dilution. On the other hand, not all transformation products may be detectable. As a new approach, we therefore developed GC-IRMS (gas chromatography-isotope-ratio mass-spectrometry) analysis for carbon and nitrogen isotope measurements of diclofenac. The method uses a derivatization step that can be conducted either online or offline, for optimized throughput or sensitivity, respectively. In combination with on-column injection, the latter method enables determination of diclofenac isotope ratios down to the sub-μgL(-1) range in environmental samples. Degradation in an aerobic sediment-water system showed strong nitrogen isotope fractionation (εN = -7.1‰), whereas reductive diclofenac dechlorination was associated with significant carbon isotope fractionation (εC = -2.0‰). Hence dual element isotope analysis bears potential not only to detect diclofenac degradation, but even to distinguish both transformation pathways in the environment. In an explorative survey, analysis of commercial diclofenac products showed significant differences in carbon and nitrogen isotope ratios, demonstrating a further potential to track, and potentially even to authenticate, commercial production batches.

Stable isotope-labeled excipients for drug product identification and counterfeit detection

PURPOSE

Counterfeit drug products have become a major problem worldwide and a number of techniques to detect counterfeit products or reduce the potential for counterfeiting have been investigated. This study examined the use of stable isotope-labeled excipients in solid dosage forms as a method to identify drug products and to detect counterfeits.

METHODS

(2)H- and (13)C-glucose were used as model excipients and incorporated in wet granulated formulations at a variety of different isotopic ratios. The ratios of (2)H/(1)H and (13)C/(12)C in each product were then determined by isotope ratio mass spectrometry.

RESULTS

Results demonstrated the ability to detect the isotope-labeled glucose in both granules and tablets.

CONCLUSIONS

It was possible to use the isotope ratios to differentiate between specific batches of granules, demonstrating the potential of this technique for in-product, batch-specific identification.

Inter-laboratory comparison of elemental analysis and gas chromatography/combustion/isotope ratio mass spectrometry. II. Delta15N measurements of selected compounds for the development of an isotopic Grob test

An inter-laboratory exercise was carried out by a consortium of five European laboratories to establish a set of compounds, suitable for calibrating gas chromatography/combustion/isotope ratio mass spectrometry (GC-C-IRMS) devices, to be used as isotopic reference materials for hydrogen, carbon, nitrogen and oxygen stable isotope measurements. The set of compounds was chosen with the aim of developing a mixture of reference materials to be used in analytical protocols to check for food and beverage authentication. The exercise was organized in several steps to achieve the certification level: the first step consisted of the a priori selection of chemical compounds on the basis of the scientific literature and successive GC tests to set the analytical conditions for each single compound and the mixture. After elimination of the compounds that turned out to be unsuitable in a multi-compound mixture, some additional oxygen- and nitrogen-containing substances were added to complete the range of calibration isotopes. The results of delta(13)C determinations for the entire set of reference compounds have previously been published, while the deltaD and delta(18)O determinations were unsuccessful and after statistical analysis of the data the results did not reach the level required for certification. In the present paper we present the results of an inter-laboratory exercise to identify and test the set of nitrogen-containing compounds present in the mixture developed for use as reference materials for the validation of GC-C-IRMS analyses in individual laboratories.