Dietary Supplement Standard Reference Materials Research Articles

Standard reference materials for dietary supplement analysis

IntroductionThe National Institute of Standards and Technology (NIST), theNational Institutes of Health Office of Dietary Supplements(NIH-ODS), and the Food and Drug Administration (FDA) areworkingincollaborationtoproducedietarysupplementStandardReference Materials (SRMs). Efforts began following the crea-tion of the NIH Office of Dietary Supplements by the DietarySupplement Health and Education Act (DSHEA) of 1994 [ 1]and the establishment of the NIH-ODS Analytical Methods andReference Materials Program (AMRM) in 2002 [ 2]. AMRM isresponsible for ensuring that quality calibration materials andmatrix-based certified reference materials (CRMs) are availableto dietary supplement laboratories along with rugged, precise,and accurate analytical methods [ 3–7]. More recently, as of June2010, the current Good Manufacturing Practices (cGMPs) pub-lished by the FDA are required for all dietary supplementsproduced in the United States [8] The cGMPs require thatproducts be evaluated for identity, purity, and strength as wellas for contaminants (toxic elements, bacteria, persistentorganic pollutants, and other toxins) and adulterants (eitherunintentional or economically motivated), placing increasedemphasis on the importance of the development of dietarysupplementSRMs.NISTstaffareoftenaskedaboutthestatusof new and existing SRMs; this manuscript is designed toprovide an update on the dietary supplement Standard Refer-ence Materials Program. The Certificates of Analysis foravailable SRMs can be found at nist.gov/SRMs [9] and canbe searched for by keyword or SRM number. The brief de-scriptions of different dietary supplements are all taken fromthe NIH-ODS factsheets [10].Material selectionThere are a number of considerations that factor into theprioritization of materials for the development of dietary sup-plement SRMs. Dietary supplement materials (matrices andtarget analytes) are ranked by an AOAC committee based onthe availability of and need for analytical methods and refer-ence standards. The order of the production of the SRMs isbasedontheneedsoftheNIHandtheFDA,informationfromtheAOACingredientrankingsubgroup(IRS)prioritylist,themarket share, and potential safety considerations associatedwith individual dietary supplements.Botanical dietary supplement SRMs have been developedatNISTassuitesofmaterialsinordertorepresenttherangeofchallenges that may be encountered during analysis.Depending on the product, the suite may consist of a rawbotanical material, an extract, and a finished product (e.g.,ground or whole tablets). Significantly different formulationswith different analytical intricacies may also be added to thesuite. For example, the suite of ephedra-containing materialsconsisted of Ephedra sinica Stapf, Ephedra sinica Stapf Na-tive Extract, Ephedra sinica Stapf Commercial Extract,Ephedra-Containing Solid Oral Dosage Form, and Ephedra-Containing Protein Powder. The plant material presented thegreatest extraction challenges. The extracts and tablets repre-sented the commercially available products with a range of

Determination of arsenic in food and dietary supplement standard reference materials by neutron activation analysis

Arsenic was measured in food and dietary supplement standard reference materials by neutron activation analysis for the purpose of assigning certified or reference As mass fractions and to assess material homogeneity. Instrumental neutron activation analysis was used to value assign As in candidate SRM 3532 Calcium Dietary Supplement and candidate SRM 3262 Hypericum perforatum (St. John’s Wort) Aerial Parts down to about 100 μg/kg. Values were also determined for two additional candidate St. John’s Wort SRMs with As mass fractions <100 μg/kg. The presence of significant amounts of 24Na and 82Br limited the reproducibility of the method below 100 μg/kg. For measurement of lower As mass fractions, a radiochemical neutron activation analysis method with extraction of As3+ into diethyl-dithiocarbamate in chloroform and detection limits down to 0.1 μg/kg. As was used to value-assign As mass fractions for SRM 3280 Multivitamin/Multielement Tablets and for candidate SRM 3233 Fortified Breakfast Cereal, and at <10 μg/kg in candidate SRM 1845a Whole Egg Powder.

Characterizing Vaccinium berry Standard Reference Materials by GC‐MS using NIST spectral libraries

A gas chromatography-mass spectrometry (GC-MS)-based method was developed for qualitative characterization of metabolites found in Vaccinium fruit (berry) dietary supplement Standard Reference Materials (SRMs). Definitive identifications are provided for 98 unique metabolites determined among six Vaccinium-related SRMs. Metabolites were enriched using an organic liquid/liquid extraction, and derivatized prior to GC-MS analysis. Electron ionization (EI) fragmentation spectra were searched against EI spectra of authentic standards compiled in the National Institute of Standards and Technology's mass spectral libraries, as well as spectra selected from the literature. Metabolite identifications were further validated using a retention index match along with prior probabilities and were compared with results obtained in a previous effort using collision-induced dissociation (CID) MS/MS datasets from liquid chromatography coupled to mass spectrometry experiments. This manuscript describes a nontargeted metabolite profile of Vaccinium materials, compares results among related materials and from orthogonal experimental platforms, and discusses the feasibility and development of using mass spectral library matching for nontargeted metabolite identification.

Liquid Chromatography-Particle Beam Electron Ionization Mass Spectrometry Method for Analysis of Botanical Extracts: Evaluation of Ephedrine Alkaloids in Standard Reference Materials

The preliminary validation of a high-performance liquid chromatography particle beam mass spectrometry method (HPLC-PB/MS) with electron impact ionization source for analysis of botanical extracts is presented. The LC-PB/MS system was evaluated for the analysis of ephedrine alkaloids using ephedra-containing National Institute of Standards and Technology dietary supplement standard reference materials (SRMs) 3241 Ephedra Sinica Stapf Native Extract and 3242 Ephedra Sinica Stapf Commercial Extract. The ephedrine alkaloids were separated by reversed-phase chromatography using a phenyl column at room temperature. A linear gradient method with a mobile phase composition varying from 5:95 [MeOH:0.1% trifluoroacetic acid (TFA) in water] to 20:80 (MeOH:0.1% TFA in water) at a flow rate of 1.0 ml/min, with an analysis time of less than 20 min, was used. The source block temperature was evaluated to determine the optimal operating conditions by monitoring the intensities and fragmentation patterns of the ephedrine alkaloids. Ephedrine and N-methylephedrine were taken as a representative of the test alkaloids. The LODs on the sub-nanogram level were achieved, with ephedrine, pseudoephedrine, and methylephedrine in the SRMs quantified by a standard addition method with recoveries of > or = 86% and RSDs of < or = 14% (n = 3).

Determination of organic acids in Vaccinium berry standard reference materials

Nine organic acids (citric acid, galacturonic acid, glycolic acid, isocitric acid, malic acid, oxalic acid, quinic acid, shikimic acid, and tartaric acid) and two anions (phosphate and sulfate) were determined in a suite of Vaccinium berry-containing dietary supplement standard reference materials (SRMs). Following solvent extraction, three independent methods were utilized in the quantification of these compounds. The first method involved reversed-phase liquid chromatography with ultraviolet absorbance detection at 210 nm and isotope dilution mass spectrometry. The second method utilized ion chromatography with conductivity detection. Finally, gas chromatography with isotope dilution mass spectrometry detection was used following derivatization with N-methyl-N-trifluoroacetamide (MSTFA). The combined data from these methods was used for the assignment of organic acid levels in the seven candidate SRMs.

Certification of standard reference materials containing bitter orange

A suite of three dietary supplement standard reference materials (SRMs) containing bitter orange has been developed, and the levels of five alkaloids and caffeine have been measured by multiple analytical methods. Synephrine, octopamine, tyramine, N-methyltyramine, hordenine, total alkaloids, and caffeine were determined by as many as six analytical methods, with measurements performed at the National Institute of Standards and Technology and at two collaborating laboratories. The methods offer substantial independence, with two types of extractions, two separation methods, and four detection methods. Excellent agreement was obtained among the measurements, with data reproducibility for most methods and analytes better than 5% relative standard deviation. The bitter-orange-containing dietary supplement SRMs are intended primarily for use as measurement controls and for use in the development and validation of analytical methods.

Analytical Challenges in the Certification of Botanical Dietary Supplement Standard Reference Materials

Analytical Challenges in the Certification of Botanical Dietary Supplement Standard Reference Materials

Characterization of a suite of ginkgo-containing standard reference materials

A suite of three ginkgo-containing dietary supplement Standard Reference Materials (SRMs) has been issued by the National Institute of Standards and Technology (NIST) with certified values for flavonoid aglycones, ginkgolides, bilobalide, and selected toxic trace elements. The materials represent a range of matrices (i.e., plant, extract, and finished product) that provide different analytical challenges. The constituents have been determined by at least two independent analytical methods with measurements performed by NIST and at least one collaborating laboratory. The methods utilized different extractions, chromatographic separations, modes of detection, and approaches to quantitation. The SRMs are primarily intended for method validation and for use as control materials to support the analysis of dietary supplements and related botanical materials.

Determination of bitter orange alkaloids in dietary supplement Standard Reference Materials by liquid chromatography with atmospheric-pressure ionization mass spectrometry

A liquid chromatographic atmospheric-pressure ionization electrospray mass spectrometry (LC-API-ES-MS) method has been developed for the determination of five bitter orange alkaloids (synephrine, octopamine, n-methyltyramine, tyramine, and hordenine) in bitter orange-containing dietary supplement standard reference materials (SRMs). The materials represent a variety of natural, extracted, and processed sample matrices. Two extraction techniques were evaluated: pressurized-fluid extraction (PFE) and sonication extraction. The influence of different solvents, extraction temperatures, and pH were investigated for a plant material and a processed sample. The LC method uses a new approach for the separation of highly polar alkaloids. A fluorinated, silica-based stationary phase separated the five alkaloids and the internal standard terbutaline in less than 20 min. This method enabled the determination of the dominant alkaloid synephrine and other minor alkaloids in a variety of dietary supplement SRMs.

A systematic approach to quantitation of ephedra alkaloids in natural health products

A method for accurate determination of ephedrine (E) alkaloids in natural health products (NHP) is described. The NIST dietary supplement standard reference materials (SRMs) were selected for these studies. These SRMs comprise ground Ma Huang herb (Ephedra sinica Stapf.), a spray dried extract of the former, and commercial formulations derived from gel caps and a protein drink. The efficiency of sonication-assisted extraction and Soxhlet extraction was studied using both ammonium formate and potassium phosphate in 3% methanol as extraction media. The efficiency of SPE clean-up of the extract deteriorated rapidly when increasing amounts of sample matrix or analyte were processed, because of limited cartridge capacity. Quantitation by the method of additions was required to ensure the highest accuracy using both LC-UV and ES-LC-MS-MS techniques. Whereas the LC-UV method is more convenient and precise, the results are more questionable than ES-LC-MS-MS, because species-specific detection is not possible.

Determination of Ephedrine Alkaloids in Dietary Supplement Standard Reference Materials

A suite of five ephedra-containing dietary supplement Standard Reference Materials (SRMs) has been issued by the National Institute of Standards and Technology (NIST) with certified values for ephedrine alkaloids, synephrine, caffeine, and selected toxic trace elements. The materials represent a variety of natural, extracted, and processed sample matrixes that provide different analytical challenges. The constituents have been determined by multiple independent methods with measurements performed by NIST and by three collaborating laboratories. The methods utilized different sample extraction and cleanup steps in addition to different instrumental analytical techniques and approaches to quantification. In addition, food-matrix proximates were determined by National Food Processor Association laboratories for one of the ephedra-containing SRMs. The SRMs are primarily intended for method validation and for use as control materials to support the analysis of dietary supplements and related botanical materials.