Use of a New LC-MS Method for The Determination of Pyrrolizidine Alkaloids in Feeds

Nanoflow liquid chromatography mass spectrometry method for quantitative analysis and target ion screening of pyrrolizidine alkaloids in honey, tea, herbal tinctures, and milk

A method for the determination of pyrrolizidine alkaloids in tea, honey, herbal tinctures, and milk samples was developed by employing nano-LC-MS with high-resolution Orbitrap mass spectrometry. Quantitation was performed using the available analytical standards, and a MS² target ion screening approach was developed using fragment ions that were specific for pyrrolizidine alkaloids under collision-induced dissociation. Proof of concept was delivered for the screening approach, proposing that the C₆H₈N⁺ fragment ion is a highly selective fragment ion for the detection of potential pyrrolizidine alkaloids. The elaborated quantitation was applied for the occurrence study of pyrrolizidine alkaloids in food products available on the Latvian market, including samples of tea (n = 15), honey (n = 40), herbal tinctures (n = 15), and milk (n = 10). The median LOQ over all analytes was 0.33 µg kg^-1 in honey, 3.6 µg kg^-1 in tea, 3.3 µg kg^-1 in herbal tinctures, and 0.32 µg kg^-1 in milk. The herbal tinctures samples and milk samples did not contain pyrrolizidine alkaloids above LOQ values. Analytes were detected in 33% of honey and 47% of tea samples. Most common were echimidine, intermedine, and enchinatine N-oxide. Pyrrolizidine alkaloids in tea samples were mainly N-oxides, with the highest total concentration being 215 µg kg^-1 among the samples, exceeding the maximum limit of 200 µg kg^-1 set by Commission Regulation (EU) 2020/2040. In honey samples, lycopsamine-type alkaloids were detected most frequently, with the highest total concentration equal to 74 µg kg^-1. Advantages of the developed nano-LC-MS methods included increased sensitivity in comparison with conventional flow LC-MS, low solvent consumption typical with nano-LC and the novel use of a selective common target ion for detection and discovery of potential pyrrolizidine alkaloids using high resolution mass spectrometry.

Scopolamine and atropine in feeds - determination with liquid chromatography mass spectrometry

Tropane alkaloids (TAs) are naturally occurring plant toxins. Due to the fact that TA-producing plants can enter the food chain, they pose a risk for animals and human health. Therefore, sensitive analytical methods need to be developed to provide an adequate safety of feed and food. The presented method is based on liquid chromatography-mass spectrometry detection and enables the determination of scopolamine and atropine in compound feeds at a low level of contamination. Limits of quantification for scopolamine and atropine were 0.92 and 0.93 µg kg^-1, respectively. Scopolamine-D₃ and atropine-D₃ were used for quantification. The method was successfully validated and applied to the analysis of 42 feed samples. Among investigated feeds, 67% contained at least one of the monitored alkaloids. Soybean meals were the feed materials contaminated most often, also with the highest determined concentrations of TAs, which reached 147.9 µg kg^-1.

Study of the occurrence of toxic alkaloids in forage grass by liquid chromatography tandem mass spectrometry

The toxic alkaloids in forage grass present a serious health hazard to humans and livestock, especially ergot alkaloids (EAs), pyrrolizidine alkaloids (PAs) and tropane alkaloids (TAs). Hence, there is a need for a simultaneous method that allows these dangerous plant toxins to be determined. A simple and effective method was developed to determine fifteen toxic alkaloids (EAs, PAs and TAs) in forage grass using the QuEChERS method and liquid chromatography tandem mass spectrometry (LC-MS/MS). The developed method was validated with average recoveries ranging from 63.10 to 102.10%, and relative standard deviations lower than or equal to 6.39% were obtained. Good linearity over the concentration range of 10-600 µg/kg dry matter (DM) was observed for the target alkaloids. The determination coefficients R² calculated for each of the matrix calibration curves were greater than 0.99. The limits of detection and quantification were 5 µg/kg DM and 10 µg/kg DM, respectively. The reproducibility of the method was verified in three laboratories: all of the mean recoveries of 15 alkaloids were higher than 60%, and the relative standard deviations in alkaloids between laboratories were all less than 14.24%. The proposed method was applied to analyse 134 forage grass samples from the meadow steppe of Inner Mongolia to monitor toxic alkaloids. A significant difference in the frequency of contamination was found between different herbage species and different regions.

Development of a new LC-MS method for accurate and sensitive determination of 33 pyrrolizidine and 21 tropane alkaloids in plant-based food matrices

Setting of maximum limits for a number of plant alkaloids is under discussion in the EU. The novel method developed and optimized in this study enables simultaneous determination of 21 tropane alkaloids (TAs) and 33 pyrrolizidine (PAs) together with their N-oxides (PANOs). For analysis of aqueous-methanolic extract, reversed phase ultra-high-performance liquid chromatography and tandem mass spectrometry (RP-U-HPLC-MS/MS) was employed. The method was validated for frequently contaminated matrices (i) sorghum, (ii) oregano, and (iii) mixed herbal tea. The recoveries at two spiking levels were in the range of 82-115%, 80-106%, and 78-117%, respectively, and repeatabilities were less than 19% for all analyte/matrix combinations. As regards the achieved limits of quantification (LOQ), their values were in the range of 0.5-10 μg kg^-1. The crucial problem encountered during method development, co-elution of multiple groups of isomeric alkaloids, was overcome by subsequent sample separation in the second chromatographic system, hydrophilic interaction liquid chromatography (HILIC), providing different separation selectivity. Lycopsamine, echinatine, and indicine (co-elution group 1) and N-oxides of indicine and intermedine (co-elution group 2), which could not be resolved on the commonly used RP column, were possible to separate fully by using the HILIC system.

Application of the sum parameter method for the determination of pyrrolizidine alkaloids in teas

Tea samples from the Polish market were analysed for the determination of pyrrolizidine alkaloids (PAs). The method applied in the study is based on the GC-MS technique and uses the sum parameter approach for quantification. The analytical protocol was subjected to validation in terms of linearity, repeatability, reproducibility, the limit of quantification and determination, matrix effect, selectivity, and uncertainty, and all evaluated parameters fulfilled the requirements of Commission Decision 2002/657. A total of 78% of the analysed samples contained 1,2-unsaturated PAs, and the concentrations were determined to fall in the range of 2-6498 µg kg^-1. The highly contaminated samples were additionally subjected to LC-MS analysis. Much higher PA concentrations were determined with the sum parameter method, proving its superior quantification capability. The high contamination found prompted an assessment of the dietary exposure from the consumption of infusions prepared from the analysed teas. Two approaches were adopted: one assuming 100% transfer of PAs to the infusions and the second assuming only partial transfer. Regardless of the adopted approach, consumption of several infusions was shown to greatly exceed the maximum acceptable daily intake of PAs.

Pyrrolizidine alkaloids quantified in soil and water using UPLC-MS/MS

Pyrrolizidine alkaloids (PAs) are produced in plants as defence compounds against insects. PAs present a serious health risk to humans and livestock; therefore it is necessary to have a validated analytical method to monitor PAs in the environment. The objective of this work is to present an UPLC-MS/MS method for quantification of PAs in environmental samples of both soil and water. A fast, reliable, and sensitive approach is developed to identify and quantify PAs in soil and water. Sample preparation was performed by clean-up and pre-concentration of the samples using MCX solid phase extraction cartridges with full optimization, and then PAs were determined by UPLC coupled with TQ-MS. In the liquid chromatography, most of the parameters were optimized and tested including gradient time, solvents, additives, and pH of the mobile phases and flow rate. In addition, the MS parameters of cone voltage, desolvation temperature, cone flows, and collision energy were optimized. The instrument limit of detection (2–7 μg L⁻¹) and limit of quantification (5–9 μg L⁻¹) were determined experimentally, and the method was linearity validated up to 1000 μg L⁻¹. The method was applied to analyse soil and surface water samples collected in April and May 2018 in Vejle, Borup, and Holte, Denmark. In total, 15 PAs were quantified and reported for the first time in environmental samples, in a range of 3–1349 μg kg⁻¹ in soil and 4–270 μg L⁻¹ in surface water.

Pyrrolizidine alkaloids quantified in soil and water.