Investigation of the separation of heterocyclic aromatic amines by reversed phase ion-pair liquid chromatography coupled with tandem mass spectrometry: The role of ion pair reagents on LC–MS/MS sensitivity

Simultaneous determination of diquat, paraquat, glufosinate, and glyphosate in plasma by liquid chromatography/tandem mass spectrometry: from method development to clinical application

Diquat (DQ), paraquat (PQ), glufosinate (GLU), and glyphosate (GLYP) are commonly used herbicides that have been confirmed to be toxic to humans. Rapid and accurate measurements of these toxicants in clinical practice are beneficial for the correct diagnosis and timely treatment of herbicide-poisoned patients. The present study aimed to establish an efficient, convenient, and reliable method to achieve the simultaneous quantification of DQ, PQ, GLU, and GLYP in human plasma using liquid chromatography-tandem mass spectrometry (LC-MS/MS) without using derivatization or ion-pairing reagents. DQ, PQ, GLU, and GLYP were extracted by the rapid protein precipitation and liquid-liquid extraction method and then separated and detected by LC-MS/MS. Subsequently, linearity, limit of detection (LOD), limit of quantification (LOQ), precision, accuracy, extraction recovery, matrix effect, dilution integrity, and stability were evaluated to validate the method based on the FDA criteria. Finally, the validated method was applied to real plasma samples collected from 166 Chinese patients with herbicide poisoning. The results showed satisfactory linearity with low LOD (1 ng/mL for DQ and PQ, 5 ng/mL for GLU, and 10 ng/mL for GLYP, respectively) and low LOQ (5 ng/mL for DQ and PQ, 25 ng/mL for GLU and GLYP, respectively). In addition, the precision, accuracy, extraction recovery, and stability of the method were acceptable. The matrix effect was not observed in the analyzed samples. Moreover, the developed method was successfully applied to determine the target compounds in real plasma samples. These data provided reliable evidence for the application of this LC-MS/MS method for clinical poisoning detection.

Formation of Carcinogens in Processed Meat and Its Measurement with the Usage of Artificial Digestion—A Review

Meat is a rich source of various nutrients. However, it needs processing before consumption, what in turn generates formation of carcinogenic compounds, i.a., polycyclic aromatic hydrocarbons (PAH), nitrosamines (NOCs), and the most mutagenic heterocyclic aromatic amines (HAAs). It was widely found that many factors affect the content of carcinogens in processed meat. However, it has recently been discovered that after digestion free HAAs are released, which are not detectable before enzymatic treatment. It was established that the highest percentage of carcinogens is released in the small intestine and that its amount can be increased up to 6.6-fold. The change in free HAAs content in analyzed samples was dependent on many factors such as meat type, doneness, particle size of meat, and the enzyme concentration used for digestion. In turn, introduction of bacteria naturally occurring in the human digestive tract into the model significantly decreases total amount of HAAs. Contrary, the addition of food ingredients rich in polyphenols, fiber, and water (pepper powder, onions, apples) increases free HAAs’ release up to 56.06%. Results suggests that in vitro digestion should be an integral step of sample preparation. Artificial digestion introduced before chromatographic analysis will allow to estimate accurately the content of carcinogens in processed meat.

Validation of an ion-pair liquid chromatography–electrospray-tandem mass spectrometry method for the determination of heterocyclic aromatic amines in meat-based infant foods

A method based on ion-pair liquid chromatography-electrospray tandem mass spectrometry (LC-MS/MS) is reported for determining heterocyclic aromatic amines (HAAs) in meat-based infant foods. The HAAs encompassed quinoline (IQ, MeIQ), quinoxaline (MeIQx), pyridine (PhIP), and carboline derivatives (AalphaC, Harman, Norharman) with d(3)-IQ, (13)C(2)-MeIQx, and d(3)-PhIP used as labelled internal standards. The method used extraction into acetone followed by a clean-up on an SCX solid-phase extraction column. LC separation was performed on a TSKgel ODS-80TS column (250 x 2.0 mm, 5 microm), the mobile phase being an ammonium formate-formic acid buffer (3.03 mM ammonium formate, pH = 2.8) aqueous solution-acetonitrile gradient at a flow rate of 0.2 ml min(-1). For unequivocal identification of each analyte, three ions were detected and chosen for selected reaction monitoring (SRM). Validation was carried out on lyophilized meat samples. Mean recoveries ranged between 78 +/- 4% and 98 +/- 2% for different analytes. Limits of quantification generally lower than 8 ng g(-1) were demonstrated in meat samples for the analytes investigated. The method exhibited a good linearity and repeatability. Robustness testing identified those factors which were statistically significant in influencing chromatographic separation and response, and indicated which parameters have to be strictly controlled for a reliable analysis of HAAs. In particular, the mobile-phase flow rate was found to be statistically significant (alpha = 0.05) for the capacity factor (k') of all analytes except for AalphaC peak, whereas the mobile-phase pH resulted to be a critical parameter for the k' values of IQ, MeIQ, and Norharman. The method was proved to be robust vs. resolution between IQ and MeIQ peaks. Among mass-spectrometric parameters, collision energy was found to significantly affect quantitative response of all analytes except that of IQ. The applicability of the method to the analysis of meat-based infant food samples was demonstrated.

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.