AOAC 2022

Unlocking the Mystery of Pesticide CRM Stability in Food Testing

There is a growing global need for pesticide residue testing in a wide variety of food commodities. In response to this need, testing laboratories must develop versatile analytical methods and workflows in order to produce scientifically valid results that ensure the safety of our food. One of the many challenges faced by food chemists is acquiring suitable pesticide certified reference materials (CRMs) to calibrate analytical equipment, monitor method performance, and confirm the identity and concentration of hundreds of pesticide residues in food commodities. Questions regarding the stability of pesticide CRMs abound among users, and there is a need to educate and inform the community. CRM producers invest considerable resources to ensure the stability of their products. The authors present CRM handling and storage best practices as guidance to ensure stability based on the results of several multiresidue pesticide stability studies. These studies demonstrate what can be expected after new pesticide CRM mix ampuls are opened and stored for use, and also after CRM mixes are combined together and used for routine multiresidue pesticide analysis using both LC-MS/MS and GC-MS/MS.

Analysis of Furan and Alkyl Furans in Food Commodities Using Headspace-SPME Arrow Coupled to GC-MS

Furan and alkyl furans are formed in foods when compounds, such as carbohydrates, ascorbic acid, and derivatives, as well as some lipids, are thermally degraded during roasting, frying, or baking. The International Agency for Research of Cancer (IARC) classified furan as a possible carcinogenic compound, raising general concern about the possible health risks associated with the occurrence of furans and alkyl furans in food. Previous research on the analysis of these volatile organic compounds reported static headspace (HS) and solid-phase microextraction (SPME) in combination with GC-MS are both beneficial techniques. The use of SPME for the analysis of these highly volatile analytes has demonstrated improved method sensitivity and higher signal-to-noise for some of the alkyl furans; however, the fragility of traditional SPME fibers is a concern. In this work, we developed a HS-SPME-GC-MS method for the analysis of furans and alkyl furans in baby formula and coffee using a SPME Arrow. The SPME Arrow geometry and design offer improved mechanical durability, enhanced method sensitivity, and robustness. Different experimental conditions, such as coating chemistry, incubation temperature, and extraction time, were evaluated. Two calibration ranges are covered, both a low concentration range from 1.25 to 150 µg/kg, and a high concentration calibration range from 25 to 8000 µg/kg. For the analysis of highly concentrated samples, different conditions of split (1:100), extraction time (1 min), and sodium chloride solution (30%) (5 mL) were selected. The method was evaluated in matrices spiked at two concentration levels: 5 and 50 µg/kg for baby formula, and 1000 and 4000 µg/kg for coffee. Satisfactory results in terms of linearity, accuracy, and precision were obtained for the majority of experiments.  Accuracy values above 111% in coffee samples could be due to sample handling and requires future experimental work to understand this bias.

Simultaneous Determination of Alternaria Toxins, Ergot Alkaloid Epimers, and Other Major Mycotoxins in Various Food Matrices by LC-MS/MS

Various food commodities are vulnerable to different types of fungal pathogens and could be contaminated with differential classes of mycotoxins as a result. It is ideal to implement a generic method for simultaneous determination of multi-mycotoxins in different food matrices or agricultural products. In this study, a simplified sample preparation procedure and a reliable LC-MS/MS analytical method were developed for comprehensive measurement of 37 regulated and emerging mycotoxins, including 5 Alternaria toxins, 6 major ergot alkaloids, and their corresponding epimers. Four different food matrices (baby wheat cereal, peanut, tomato puree, and blended flour) were chosen for method validation to demonstrate the applicability of this analytical method to a wide range of food types. Sample extraction was performed using a formic acid-acidified 80:20 acetonitrile:water solution followed by extract dry down and reconstitution in a 50:50 water:methanol solution for injection analysis on a biphenyl LC column. Chromatographic analysis was performed using MS friendly acidic mobile phases and completed with a short 11-minute cycling time for proper separation of ergot alkaloid epimers. Method accuracy and precision were evaluated by fortification of food samples at 3 different levels. Accurate quantification was achieved using matrix-matched calibration standards at the range of 0.4 to 400 µg/kg. The recoveries of all mycotoxins (except citrinin) in fortified samples were from 70% to 120%, and the relative standard deviation was less than 20%. The established workflow was simple and fast for multi-mycotoxin determination with a unique benefit of simultaneous analysis of Alternaria toxins and ergot alkaloids.

Large Volume Injection of Pesticides Using Low-Pressure Gas Chromatography

Concurrent Solvent Recondensation Large Sample Volume splitless injection (CSR-LVSI, or LVI) is a gas chromatography sample injection technique that overcomes the limitation of using a smaller sample volume of 1 to 2 µL, which is typical of conventional splitless injections. Low-Pressure Gas Chromatography (LPGC) is a novel technique that has been successfully applied for multiresidue pesticide detection and quantification. The LPGC configuration with the restrictor/guard column facilitates the requirements of a CSR-LVSI and has the potential to improve the sensitivity and lower detection limits. Peak shapes of large-volume injections using both acetonitrile and acetonitrile–toluene were evaluated in the range of 1–25 µL, and the relationship between the peak area and injection volume was established. The large volume injections (>10 µL) resulted in peak splitting when acetonitrile was used. The later eluting peaks were affected more while the effect of increased volume on peak areas for larger than 10 µL injections was negligible. The calibration parameters were compared for 1 and 5 µL injection. The limits of detection and other parameters were comparable between the two injection volumes. This presentation will describe both CSR-LVSI and LPGC and demonstrate the applicability of combining these techniques using a variety of solvents.

Cannabis Potency Testing—Which Column Dimension is Right for You?

When starting method development for potency testing, it’s important to choose the right column dimension for the target analysis. In this work, different column dimensions of the Raptor ARC-18 phase were utilized to develop methods to meet various labs’ needs using HPLC-UV. To demonstrate the powerful resolving capabilities of Raptor ARC-18, a 50 x 3 mm, 2.7 µm column was used to analyze 7 cannabinoids, including CBD; CBDA; delta-9-THC; delta-8-THC; (6aR, 9S)-delta-10-THC; (6aR, 9R)-delta-10-THC; and THCA. This method utilizes gradient conditions, methanol as the organic modifier, and an overall cycle time of 8 minutes. This methodology is ideal for labs that are only interested in the required testing needed to be compliant with specific state testing regulations. Next, additional cannabinoids including CBDV, THCV, CBG, CBN, CBGA, and CBC were added to the previous analytes for a total of 13 cannabinoids. Using the same column dimension and mobile phases, a method was developed to resolve all analytes in 10 minutes. Finally, to include exo-THC and CBNA, a 150 x 3 mm, 2.7 µm column dimension was used to demonstrate the utility of a longer column dimension. The organic modifier used was 0.1% formic acid in acetonitrile, where a total of 15 cannabinoids were able to be resolved in 10 minutes. Each of these methods was applied to hemp matrix to demonstrate the applicability of these methods in real-world samples. 

The Detection of Flavonoids in Hemp Flower by LC-MS/MS

Flavonoids are a class of compounds that are endogenous in hemp and cannabis that are antioxidant rich and can affect the flavor profile. Routine testing in cannabis labs oftentimes does not include flavonoid testing, but as the market for cannabis grows, industry leaders may choose to implement new tests to aid the advancement of the science of cannabis and to differentiate their services from their competitors. In this work, a method to detect 19 flavonoids in CBD- and CBG-dominant hemp flower was developed using LC-MS/MS. Extraction of flavonoids was performed by weighing 0.5 g of ground hemp flower and adding 80/20 methanol/water (10 mL) to the hemp flower and vortexing. The samples were sonicated for 15 min, centrifuged at 4200 rpm for 5 min, and diluted 50-fold. The analytical method was developed using LC-MS/MS with electrospray ionization in positive and negative ion modes. The method uses gradient conditions on a Raptor Biphenyl 100 x 2.1, 2.7 µm column equipped with a guard cartridge. Ten flavonoids were detected in the CBG hemp flower sample, and 12 flavonoids were detected in the CBD hemp flower samples. Single point recovery experiments were also performed at 100 ppb using two deuterated internal standards. The results of the single point recovery ranged from 80 – 104%. The developed method was able to resolve isobars within a cycle time of 7 minutes, and acceptable recoveries were achieved for both hemp flower samples, indicating this is an effective procedure for the extraction of flavonoids from hemp flower.