Evaluation of reversed-phase columns for the analysis of heterocyclic aromatic amines by liquid chromatography—electrospray mass spectrometry

Quantification of hetero-cyclic amines from different categories of braised beef by optimized UPLC-TQ-XS/ESI method

This research work has developed and optimized a sensitive analytical method for separation and quantification of heterocyclic amines (HCAs) mainly including PhIP, Harman, Norharman, IQ, MeIQ, AαC, MeAαC and Trp-P-2 by optimizing UPLC-TQ-XS using electrospray ionization source (ESI+) on ACQUITY UPLC® BEH C18 column in <7 min, from braised beef sample matrix. Meanwhile, modified HCAs extraction by modifying QuEChERS (quick, easy, cheap, efficient, rugged and safe) technique and revisited with solid phase extraction (SPE) for HCAs purification, instead using traditional QuEChERS salts. Moreover, optimized pH conditions of HCA extracts before purification, for better extraction recoveries. Furthermore, this method was validated in terms of method validation parameters. Lastly, simulation of real braised beef model provided the minimum formation of HCAs by optimizing cooking parameters and precursors in a cooking system. Therefore, this method could be applied simultaneously on braised beef matrix either marketed or home cooked for HCAs analysis.

Integrated quantitative and qualitative workflow for in vivo bioanalytical support in drug discovery using hybrid Q-TOF-MS

Background: UHPLC coupled with orthogonal acceleration hybrid quadrupole-TOF (Q-TOF)-MS is an emerging technique offering new strategies for the efficient screening of new chemical entities and related molecules at the early discovery stage within the pharmaceutical industry. In the first part of this article, we examine the main instrumental parameters that are critical for the integration of UHPLC–Q-TOF technology to existing bioanalytical workflows, in order to provide simultaneous quantitative and qualitative bioanalysis of samples generated following in vivo studies. Material & Methods: Three modern Q-TOF mass spectrometers, including Bruker maXis™, Agilent 6540 and Sciex TripleTOF™ 5600, all interfaced with UHPLC systems, are evaluated in the second part of the article. The scope of this work is to demonstrate the potential of Q-TOF for the analysis of typical small molecules, therapeutic peptides (molecular weight <6000 Da), and enzymatically (i.e., trypsin, chymotrypsin and pepsin) cleaved peptides from larger proteins. Results & Discussion: This work focuses mainly on full-scan TOF data obtained under ESI conditions, the major mode of TOF operation in discovery bioanalytical research, where the compounds are selected based on their pharmacokinetic/pharmacodynamic behaviors using animal models prior to selecting a few desirable candidates for further development. Finally, important emerging TOF technologies that could potentially benefit bioanalytical research in the semi-quantification of metabolites without synthesized standards are discussed. Particularly, the utility of captive spray ionization coupled with TripleTOF 5600 was evaluated for improving sensitivity and providing normalized MS response for drugs and their metabolites. The workflow proposed compromises neither the efficiency, nor the quality of pharmacokinetic data in support of early drug discovery programs.

Analysis of heterocyclic aromatic amines

Heterocyclic aromatic amines are formed in protein and amino acid-rich foods at temperatures above 150 degrees C. Of more than twenty heterocyclic aromatic amines identified ten have been shown to have carcinogenic potential. As nutritional hazards, their reliable determination in prepared food, their uptake and elimination in living organisms, including humans, and assessment of associated risks are important food-safety issues. The concentration in foods is normally in the low ng g(-1) range, which poses a challenge to the analytical chemist. Because of the complex nature of food matrixes, clean-up and enrichment of the extracts are also complex, usually involving both cation-exchange (propylsulfonic acid silica gel, PRS) and reversed-phase purification. The application of novel solid-phase extraction cartridges with a wettable apolar phase combined with cation-exchange characteristics simplified this process--both the polar and apolar heterocyclic aromatic amines were recovered in one fraction. Copper phthalocyanine trisulfonate bonded to cotton ("blue cotton") or rayon, and molecular imprinted polymers have also been successfully used for one-step sample clean-up. For analysis of the heterocyclic aromatic amines, liquid chromatography with base-deactivated reversed-phase columns has been used, and, recently, semi-micro and capillary columns have been introduced. The photometric, fluorimetric, or electrochemical detectors used previously have been replaced by mass spectrometers. Increased specificity and sub-ppb sensitivities have been achieved by the use of the selected-reaction-monitoring mode of detection of advanced MS instrumentation, for example the triple quadrupole and Q-TOF instrument combination. Gas chromatography, also with mass-selective detection, has been used for specific applications; the extra derivatization step needed for volatilization has been balanced by the higher chromatographic resolution.

Heterocyclic amines: Chemistry and health

Heterocyclic amines (HAs) occur at the ppb range in foods. Most of them demonstrate potent mutagenicity in bacteria mutagenicity test, and some of them have been classified by the International Agency for Research on Cancer as probable/possible human carcinogens. Their capability of formation even during ordinary cooking practices implies frequent exposure by the general public. Over the past 30 years, numerous studies have been stimulated aiming to alleviate human health risk associated with HAs. These studies contribute to the understanding of their formation, characterization, and quantification in foods; their mutagenesis/carcinogenesis, mechanisms of antimutagenesis by chemical or phytogenic modulators; and strategies to inhibit their formation. The chemistry of HAs, their implications in human health, factors influencing their formation, and feasible ways of suppression will be briefly reviewed. Their occurrence in trace amounts in foods necessitates continuous development and amelioration of analytical techniques. Various inhibitory strategies, ranging from modifying cooking conditions to incorporation of different modulators, have been developed. This will remain one of the foremost areas of research in the field of food chemistry and safety.

Ultra-performance liquid chromatography–tandem mass spectrometry for the analysis of heterocyclic amines in food

A new ultra-performance liquid chromatography-electrospray tandem mass spectrometry (UPLC-ESI-MS/MS) method was developed to perform the determination of 16 mutagenic heterocyclic amines (HAs) in complex food samples in less than 2 min. The UPLC separation was carried out using an Acquity BEH C18 column (50 mm x 2.1 mm i.d., 1.7 microm particle size) that provided high efficiency and resolution in combination with high linear velocities. The UPLC system was coupled to the triple quadrupole Waters Micromass Quattro Premier. This system permits high-speed data acquisition without peak intensity degradation which is required to monitor the narrow chromatographic peaks (1-2 s) of HAs. The determination was performed in selected reaction monitoring (SRM) mode. The quality parameters of the developed method were established, obtaining instrumental LODs lower than 0.23 pg injected and a repeatability at low concentration level lower than 9.1% CV (n = 6). To evaluate the performance of the method in high throughput analysis of complex samples, the UPLC-MS/MS method was applied to the analysis of HAs in two meat extracts.

Enhanced sensitivity for the determination of ambiphilic polyaromatic amines by LC–MS/MS after acetylation

A new method for the analysis of aminonitropyrenes and diaminopyrenes was developed for urine and hemoglobin samples using LC-MS/MS. A good separation by LC was only achieved after derivatization of the amino group, which also increased sensitivity to a limit of detection (LOD) of 0.1 pg (on column) for diaminopyrene and 5 pg for aminonitropyrene using electrospray ionization (ESI). Compared to a derivatization with pentafluorobenzoyl chloride yielding only one sensitive MS/MS transition, acetylation offers the advantages of a higher selectivity with two sensitive MS/MS transitions and the possibility of a direct detection of acetylated aminonitropyrenes and diaminopyrenes formed metabolically in vivo. Acetylated diaminopyrene was detected in urine and after hydrolysis of the corresponding hemoglobin adducts followed by acetylation in blood samples of rats after administration of dinitropyrene but not in controls. A method based on GC-MS with negative chemical ionization of the electrophore labelled metabolites was non-selective since only one major ion [M - HF]- was formed and some isobaric peaks were observed preventing unequivocal analyte identification at concentrations close to the LOD.