Comparison between liquid chromatography-UV detection and liquid chromatography-mass spectrometry for the characterization of impurities and/or degradants present in trimethoprim tablets

Trapping mode two-dimensional liquid chromatography for quantitative low-level impurity enrichment in pharmaceutical development

Trapping mode two-dimensional liquid chromatography (2D-LC) has recently found applications in pharmaceutical analysis to clean, refocus, and enrich analytes. Given its enrichment capability, 2D-LC with multiple trappings is appealing for low-level impurity monitoring that cannot be solved by single dimensional LC (1D-LC) or unenriched 2D-LC analysis. However, the quantitative features of multi-trapping 2D-LC remain largely unknown at impurity levels from parts-per-million (ppm) to 0.15% (w/w). We present a simple heart-cutting trapping mode 2D-LC workflow using only common components and software found in typical off-the-shelf 1D-LC instruments. This robust, turn-key system's quantitative capabilities were evaluated using a variety of standard markers, demonstrating linear enrichment for up to 20 trapping cycles and achieving a recovery of over 97.0%. Next, the trapping system was applied to several real-world low-level impurity pharmaceutical case studies including (1) the identification of two unknown impurities at sub-ppm levels resulting in material discoloration, (2) the discovery of a new impurity at 0.05% (w/w) co-eluted with a known impurity, making the undesired summation above the target specification, and (3) the quantification of a potential mutagenic impurity at 10-ppm level in a poorly soluble substrate. The recovery in all studies was better than 97.0% with RSD lower than 3.0%, demonstrating accuracy and precision of the 2D-LC trapping workflow. As no specialized equipment or software is required, we envision that the system could be used to develop low-impurity monitoring methods suitable for validation and potential execution in quality-control laboratories.

Ultrafast laser diode thermal desorption method for analysis of representative pharmaceuticals in soil leachate samples

We developed and evaluated a novel analytical method combining ambient ionization technique - laser diode thermal desorption with chemical ionization (LDTD-APCI) and tandem mass spectrometry detection. The LDTD/APCI-MS/MS method was developed for determination of representative pharmaceuticals from different classes (carbamazepine, sulfamethoxazole, irbesartan, fexofenadine) in leachate samples from soil sorption experimentation. We then optimized laser pattern, laser energy and spiked sample volume, which are crucial parameters for this LDTD/APCI-MS/MS method. We further identified utility of a chelating agent (Na₂-EDTA) to obtain the highest achievable and reproducible signal of target analytes. Achieved method performance parameters (LODs, LOQs, trueness and precision) were comparable with those obtained from LC-MS/MS. However, application of this novel LDTD/APCI-MS/MS method reduced analysis time by two orders of magnitude (to 12 s), compared to more conventional LC-MS/MS approaches, without use of organic solvents. We expect this novel method will reduce costs and increase throughput for future analyses of pharmaceuticals in the environment while advancing a timely principle of green chemistry.

Mass spectrometry detection of basic drugs in fast chiral analyses with vancomycin stationary phases

Current trends in chiral analysis of pharmaceutical drugs are focused on faster separations and higher separation efficiencies. Core-shell or superficially porous particles (SPP) based chiral stationary phases (CSPs) provide reduced analysis times while maintaining high column efficiencies and sensitivity. In this study, mobile phase conditions suitable for chiral analyses with electrospray ionization LC-MS were systematically investigated using vancomycin as a representative CSP. The performance of a 2.7 µm SPP based vancomycin CSP (SPP-V) 10 cm × 0.21 cm column was compared to that of a corresponding 5 µm fully porous particles based analogue column. The results demonstrated that the SPP-V column provides higher efficiencies, 2-5 time greater sensitivity and shorter analysis time for a set of 22 basic pharmaceutical drugs. The SPP-V was successfully applied for the analysis of the degradation products of racemic citalopram whose enantiomers could be selectively identified by MS.

Solar photo-Fenton process on the abatement of antibiotics at a pilot scale: Degradation kinetics, ecotoxicity and phytotoxicity assessment and removal of antibiotic resistant enterococci

This work investigated the application of a solar driven advanced oxidation process (solar photo-Fenton), for the degradation of antibiotics at low concentration level (μg L(-1)) in secondary treated domestic effluents at a pilot-scale. The examined antibiotics were ofloxacin (OFX) and trimethoprim (TMP). A compound parabolic collector (CPC) pilot plant was used for the photocatalytic experiments. The process was mainly evaluated by a fast and reliable analytical method based on a UPLC-MS/MS system. Solar photo-Fenton process using low iron and hydrogen peroxide doses ([Fe(2+)](0) = 5 mg L(-1); [H(2)O(2)](0) = 75 mg L(-1)) was proved to be an efficient method for the elimination of these compounds with relatively high degradation rates. The photocatalytic degradation of OFX and TMP with the solar photo-Fenton process followed apparent first-order kinetics. A modification of the first-order kinetic expression was proposed and has been successfully used to explain the degradation kinetics of the compounds during the solar photo-Fenton treatment. The results demonstrated the capacity of the applied advanced process to reduce the initial wastewater toxicity against the examined plant species (Sorghum saccharatum, Lepidium sativum, Sinapis alba) and the water flea Daphnia magna. The phytotoxicity of the treated samples, expressed as root growth inhibition, was higher compared to that observed on the inhibition of seed germination. Enterococci, including those resistant to OFX and TMP, were completely eliminated at the end of the treatment. The total cost of the full scale unit for the treatment of 150 m(3) day(-1) of secondary wastewater effluent was found to be 0.85 € m(-3).

Mass spectrometry for small molecule pharmaceutical product development: a review

Developing a pharmaceutical product has become increasingly difficult and expensive. With an emphasis on developing project knowledge at an earlier stage in development, the use of information-rich technologies (particularly MS) has continued to expand throughout product development. Continued improvements in LC/MS technology have widened the scope of utilizing MS methods for performing both qualitative and quantitative applications within product development. This review describes a multi-tiered MS strategy designed to enhance and accelerate the identification and profiling of both process- and degradation-related impurities in either the active pharmaceutical ingredient (API) or formulated product. Such impurities can be formed either during chemical synthesis, formulation, or during storage. This review provides an overview of a variety of orthogonal-mass spectrometric methodologies, namely GC/MS, LC/MS, and ICP-MS, in support of product development. This review is not meant to be all inclusive; however, it has been written to highlight the increasing use of hyphenated MS techniques within the pharmaceutical development area.

Determination of antibiotics in Brazilian surface waters using liquid chromatography-electrospray tandem mass spectrometry

A liquid chromatography-electrospray tandem mass spectrometry (LC-MS/MS) method for the determination of antibiotics in water was developed and applied to Brazilian surface waters. Amoxicillin, ampicillin, cefalexin (CEF), ciprofloxacin (CIP), norfloxacin (NOR), sulfamethoxazole, tetracycline (TET), and trimethoprim were selected as target compounds due to their high consumption pattern in Brazil. LC and MS conditions were optimized to produce the maximum analytic response for each compound. Anion exchange and polymeric solid-phase extraction cartridges, in series, were employed during the extraction procedures. Recovery, linear range, limit of detection (LOD), and limit of quantification were calculated. LOD varied from 0.13 ng L(-1) for CIP and NOR to 0.76 ng L(-1) for TET. Surface water samples from the Atibaia watershed (São Paulo State, Brazil) were analyzed. Results showed that seasonal and anthropogenic aspects dictated the levels of antibiotics in the samples. An overall frequency of detection of 55% was observed during the rainy period, whereas a higher percentage (88%) was noticed for samples collected during the dry season. In the Atibaia River, sample concentrations ranged from 29 ng L(-1) for CEF to 0.5 ng L(-1) for NOR. In a sewage-affected stream, however, concentrations up to 2422 ng L(-1) CEF were found.

Pressurized capillary electrochromatographic assay of trimethoprim impurities using 1 microm particle-based columns

One micrometre silica particles, derivatized with C18, were electrokinetically packed into a 75-microm-i.d. capillary. The resulting column was evaluated for the separation of trimethoprim (TMP) and its impurities using pressurized capillary electrochromatography (pCEC), starting from a capillary liquid chromatographic (CLC) separation. These samples require gradient elution when separated by high performance liquid chromatography (HPLC), but with the new columns isocratic elution suffices for their separation by CLC or pCEC. Only 70,000 theoretical plates/m for impurity C were achieved using CLC mode at relative low pressure (78 bar) although very small particles were utilized. When a voltage above 2 kV (50 V/cm) was applied, unknown peaks appeared, which was assumed due to an electrophoretic effect with the unknown peaks resolving as a result of the applied voltage. In order to minimize these unfavorable contributions, only a low voltage was applied, still leading to higher separation performances and shorter separation times than in CLC. The optimal analyzing conditions in pCEC included a pressure of 78 bar, an applied voltage of 1 kV, and a mobile phase consisting of 80 mM sodium perchlorate (pH 3.1)/methanol (60/40, v/v). These conditions were used to separate and quantify four major impurities in TMP within 22 min. The obtained calibration curves were linear (r>0.9980) in concentration ranges between 0.005 and 0.1 mg/mL for impurities A and C; 0.02 and 0.10 mg/mL for impurity F; and 0.01 and 0.10 mg/mL for impurity H. The detection limits (S/N=3) for impurities A, C, F, and H were 0.52, 0.84, 3.18, and 2.41 microg/mL, respectively. The calibration curves were successfully applied to analyze spiked bulk samples, with mean recoveries ranging from 92% to 110%. The developed method can therefore be considered simple, rapid, and repeatable.

Chemometric analysis of complex hyphenated data

Component detection algorithm (CODA) is a method to quickly extract the high-quality mass chromatograms from complex liquid chromatography/electrospray ionization mass spectrometry (LC/MS) data sets, saving operators hours of analysis time. It appeared, however, that mass chromatograms with a limited baseline problem were ignored. This paper describes several methods to increase the tolerance for mass chromatograms with a baseline.

Application of Ion Trap-MS with H/D Exchange and QqTOF-MS in the Identification of Microbial Degradates of Trimethoprim in Nitrifying Activated Sludge

In this work, the identification of two microbial degradation products of the antimicrobial trimethoprim (290 Da) is described. The structural elucidation of the metabolites, which were produced by nitrifying activated sludge bacteria in a small-scale laboratory batch reactor, was accomplished by electrospray ionization-ion trap mass spectrometry conducting consecutive fragmentation steps (MS(n)) combined with H/D-exchange experiments. Although one metabolite corresponded to alpha-hydroxytrimethoprim (306 Da), oxidation of the aromatic ring within the diaminopyrimidine substructure was determined for the second degradate (324 Da). Accurate mass measurements of the two metabolites were provided by a hybrid quadrupole time-of-flight-mass spectrometer operated in MS/MS mode. With absolute mass errors of <5 mDa, it allowed us to confirm the proposed elemental composition for the protonated precursor ions as well as for a series of fragment ions that were previously identified by ion trap mass spectrometry. The study emphasized the potential of nitrifying activated sludge bacteria for breaking down an environmentally relevant pharmaceutical that is otherwise poorly degradable by a bacterial community encountered in conventional activated sludge.

Component Detection Weighted Index of Analogy: Similarity Recognition on Liquid Chromatographic Mass Spectral Data for the Characterization of Route/Process Specific Impurities in Pharmaceutical Tablets

Detection and identification of impurities in pharmaceuticals is an essential task for determining the possible infringement of a patent. This article reports a multivariate analysis method to distinguish between tablets of the same substance on the basis of their origin, by characterizing route/process specific impurities via diagnostic ion chromatograms, using liquid chromatography/mass spectrometry (LC/MS). The approach is based on the formulation of a novel index that quantifies the similarity between LC/MS samples, named the component detection weighted index of analogy. The index estimates similarity by fully exploiting the two-dimensional nature of the data, where the relative contribution of chromatograms relates to their quality and noise level. Results show that well-defined clusters are formed according to the origin of tablets; a series of ions are identified as characterizing each class and can be used to predict the origin of unknown tablet samples. The method presented is designed for analysis of larger data sets and can be suitable for exploratory analysis where any a priori knowledge on the data is scarce or absent, hence requiring the acquisition of chromatograms in a broad m/z range.

Fragmentation of trimethoprim and other compounds containing alkoxy-phenyl groups in electrospray ionisation tandem mass spectrometry

This work describes electrospray ionisation tandem mass spectrometry studies of trimethoprim and a series of structurally similar compounds containing alkoxy-phenyl groups; using accurate mass measurement to confirm the proposed fragmentations. Radical cations were observed in the spectra obtained for some of the compounds, as well as uncommon fragmentations showing losses of CH4 and C2H6, whereas other compounds showed the formation of even electron ions. Possible structures for the fragment ions have been proposed and explanations for the different types of fragmentations based on the structures of the compounds. In addition an alternate structure for a fragment ion previously reported for tandem mass spectrometry of trimethoprim has been proposed, based on accurate mass measurement.