The Analysis of Retinyl and in Foods and Supplements Using Coupled Supercritical Fluid Extraction and Chromatography with Tandem Mass Spectrometry Detection Daniel Hengst, Andres Vasquez, Tyler Gatz and Chad Scheurell Eurofins Food Integrity and Innovation, Madison, WI

Abstract Internal procedures were followed to complete a method validation exercise. Calibration curves were established in the range of 0.18-36 mcg, method precision was determined by analyzing several replicates of internal control and Retinyl Palmitate are esters of , also known as . Vitamin A is a critical samples over multiple days and accuracy was established by fortifying blank material across the assay analysis component of the mammalian dietary intake, having metabolic roles associated with vision, gene transcription and range and determining the percent recovery. All method performance criteria met AOAC guidelines, with overall immune function. Due to the nutritional importance of this compound, many foods and supplements are fortified with results comparable to AOAC and USP routine methods. these ester forms of retinol. The quick and accurate analysis of these compounds is crucial, since dietary deficiency or overabundance may lead to adverse physiological effects. Traditional methodology for the analysis of these compounds can be time-consuming and tedious, with lengthy techniques such as saponification and liquid-liquid Results partitions commonly employed. A method for the analysis of Retinyl Acetate and Retinyl Palmitate has been developed and validated utilizing coupled Supercritical Fluid Extraction and Chromatography with Tandem Mass Table 1. Precision Spectrometry detection. This technique produces equivalent results to reference methods, with only four minutes of Average Legacy % difference chemist time required per sample for the extraction procedure. Average result legacy method SFE-SFC- by SFE-SFC- RSD Legacy method result RSD MSMS vs. Analyte Matrix MSMS (mcg/g) (%) HorRat method (mcg/g) (%) legacy method Introduction USP 38- Vitamin A is fortified in foods and supplements on a wide scale. Bailey et al. estimated that 28-37% of the general NF 33, Figure 2. Calibration Standard, 18 mcg population consume supplements containing Vitamin A in a study published in The Journal of Nutrition (2011). Retinyl Vitamin Methods Sources of Vitamin A activity commonly added to supplements include Beta , Retinyl Acetate and Retinyl Acetate Tablet 883 2.7 0.940 1 and 2 845 5.7 4.5 Palmitate. Retinyl Infant AOAC Retinyl Acetate and Retinyl Palmitate are esters of retinol, containing the substituted β-ionone ring and side chain Acetate Formula 12.2 4.0 0.733 2012.09 11.3 0.9 8.0 common to the retinoids. These compounds are routinely used as the source of Vitamin A supplementation, since Retinyl Infant AOAC the esterification reduces the capacity of the compound to oxidize, without reducing the biological activity of the Palmitate formula 17.2 3.9 0.752 2012.09 17.4 1.5 -1.1 vitamin. Biological retinol activity is most commonly associated with vision, but other metabolic functions have been Fortified identified: for example, immune function and embryonic development are linked to retinol activity. Retinyl Breakfast AOAC Palmitate Cereal 14.6 5.4 1.02 2001.13 14.8 4.8 -1.4 Methods The analysis of the A vitamins can be challenging due to the rapid oxidization and isomerization of these compounds. Since the retinoids are typically unstable in the presence of acids, metals, selected enzymes, heat and non-filtered light, careful control of testing conditions is critical. Many regulatory methods have been established for the retinol esters by the USP, AOAC and other governing bodies. For detection of pure material, spectrophotometric detection at a 325 nm is commonly used. Normal and reverse phase liquid chromatography with UV wavelength Figure 3. Infant Formula Chromatogram detection is the common instrument of choice for the analysis of foods and supplements. Typical extraction procedures include saponification and direct extraction. Saponification mandates the addition of a strong base to the extraction procedure, which will cleave the ester linkage of Retinyl Palmitate and Acetate; the analyte will then be Conclusion analyzed as retinol. The saponification process is lengthy, including an initial suspension of sample in antioxidant, water, alcohol and base. After an incubation period, often lasting several hours, the sample suspension is A method for the analysis of Vitamin A Acetate and Vitamin A Palmitate using SFE-SFC-MSMS has been repeatedly partitioned into a nonpolar solvent, which is concentrated and exchanged before analysis. Direct successfully developed and validated at Eurofins Food Integrity and Innovation. This method is advantageous over extractions are simplified, without the use of the lengthy incubation. However, the process can still be labor legacy methods in several ways. Analyst labor is dramatically reduced, with manual sample preparation steps intensive with multiple solvent additions, liquid-liquid partitions, and solvent exchanges as well as careful attention to complete in a manner of minutes rather than hours. Inert conditions are maintained throughout the breadth of the preventing the isomerization and oxidization of the analyte. extraction procedure which minimizes the need for degassing and antioxidant addition steps. The use of hazardous solvents is radically reduced with the bulk of the extraction solution and mobile phase being carbon dioxide; the Coupled Supercritical Fluid Extraction and Chromatography with Tandem Mass Spectrometry detection remaining components are the relatively benign alcohols. Solvent disposal is vastly reduced, with spent carbon (SFE-SFC-MSMS) is an attractive alternative for the analysis of the retinol esters. With this technique, the analytes dioxide simply released into a laboratory hood system. Finally, the instrument throughput is relatively rapid, with a are simultaneously extracted, chromatographed and analyzed using supercritical carbon dioxide as the major cycle time of 16 minutes per sample. In future research, this instrumentation will be applied to other nonpolar component of the extraction solution and mobile phase. A method has been developed and validated for the analytes, such as other fat soluble vitamins, contaminants and lipids. analysis of Retinyl Acetate and Retinyl Palmitate in foods and supplements using SFE-SFC-MSMS in the range of 0.6-20,000 mcg/g. Manual sample preparation steps only require 4 minutes of analyst time, and the extraction-analysis cycle time is 16 minutes per sample. Figure 1. Retinyl Palmitate Calibration Method Details, SFE-SFC-MSMS Before sampling, the test sample is milled using a variety of techniques, including cryogenic milling, ball milling and wet milling. A suitable portion is weighed, and then mixed with aliquots of water, stable isotope internal standard and Fortification level Acceptable recovery alcohol. This sample slurry is combined with a water absorbent material and transferred to an extraction cell. The Analyte (mcg/g) N Average recovery (%) range (%)1 cell is loaded on the SFE-SFC (Shimadzu Nexera UC), where the sample is extracted with supercritical carbon 0.6 9 105 75-120 dioxide and alcohol, with a fraction of the extract focused on a Cosmosil Cholester column (250 x 4.6 mm, 5um). Retinyl 1000 9 102 90-108 After the extraction portion is complete, the analytes are eluted with a linear gradient of methanol in supercritical Acetate carbon dioxide. Detection and quantitation is performed with a Tandem Mass Spectrometer (Agilent 6490, APCI 25000 9 95.8 92-105 source), with Retinyl Palmitate and Retinyl Acetate quantitated with an ion transition of 269.2/92.9 da. Ionization effects and extraction efficiency are compensated for with stable isotope internal standards, 13C4 Vitamin A Acetate 0.6 9 104 75-120 Retinyl and D4 Retinyl Palmitate at ion transitions of 273.2/97.1 and 273.1/94.1 da respectively. Since the target matrices 1000 9 99.5 90-108 Palmitate may contain quite high levels of the retinol esters, a 1 -5 split is installed before the MSMS, with a makeup pump 20000 9 94.2 92-105 delivering a high flow rate of methanol to perform an in line dilution. High level samples are quantitated using ion transitions of 270.1/93.1 da with the concentration quantitated against the monoisotopic species calibration curve, 1Taken from Official Methods of Analysis of AOAC International, “Guidelines for Dietary Supplements and Botanicals,” Appendix K, p. 8. and a determined multiplication factor is applied.

Presented at the AOAC Annual Meeting and Exposition 2019