Certificate of Analysis

Transcription

1 Ntionl Institute of Stndrds & Technology Certificte of Anlysis Stndrd Reference Mteril 1570 Trce Elements in Spinch Leves This Stndrd Reference Mteril (SRM) is intended primrily for use in evluting the relibility of nlyticl methods for the determintion of mjor, minor, nd trce elements; proximtes; clories; nd totl dietry fiber in botnicl mterils, griculturl food products, nd mterils of similr mtrix. A unit of SRM 1570 consists of 60 g of finely powdered dried spinch leves. Certified Concentrtion Vlues: The certified concentrtion vlues of the constituent elements re given in Tble 1. These concentrtions re bsed on the greement of results from t lest two independent nlyticl methods or from method of known ccurcy. Anlyticl methods re provided in Appendix A. Reference Concentrtion Vlues: Reference concentrtion vlues of constituent elements re provided in Tble 2; nlyticl methods re provided in Appendix A. Reference concentrtion vlues for selected proximtes nd totl dietry fiber re provided in Tble 3; nlyticl methods re provided in Appendix B. Reference vlues re noncertified vlues tht re the best estimtes of the true vlues; however, the vlues do not meet NIST criteri for certifiction nd re provided with ssocited uncertinties tht my reflect only mesurement precision, my not include ll sources of uncertinty, or my reflect lck of sufficient sttisticl greement mong multiple nlyticl methods. Informtion Concentrtion Vlues: Informtion concentrtion vlues for dditionl constituent elements re provided in Tble 4. Informtion vlues for crbohydrte, cloric content, ft, nd individul ftty cids re provided in Tble 5. These re noncertified vlues with no reported uncertinties s there is insufficient informtion to ssess uncertinties. The informtion vlues re given to provide dditionl chrcteriztion of the mteril. Use of this SRM to quntittively monitor method performnce for nlytes other thn those with certified or reference concentrtion vlues in Tbles 1 through 3 is not wrrnted. Expirtion of Certifiction: The certifiction of this SRM lot is vlid until 31 August 2008, within the mesurement uncertinties specified, provided the SRM is hndled nd stored in ccordnce with the instructions given in this certificte. Vlue ssignment is nullified if the SRM is dmged, contminted, or modified. Mintennce of SRM Certifiction: NIST will monitor this SRM over the period of its certifiction. If substntive technicl chnges occur tht ffect the certified vlues before the expirtion of this certificte, NIST will notify the purchser. Return of the ttched registrtion crd will fcilitte notifiction. The originl technicl nd support spects involved in the certifiction nd issunce of this SRM were coordinted through the NIST Stndrd Reference Mterils Progrm by R.A. Alvrez nd T.E. Gills. Revision of this certificte ws coordinted through the NIST Stndrd Reference Mterils Progrm by J.C. Colbert. Willie E. My, Chief Anlyticl Chemistry Division Githersburg, MD Revised Certificte Issue Dte: 31 August 2001 See Certificte Revision History on Lst Pge John Rumble, Jr., Acting Chief Stndrd Reference Mterils Progrm SRM 1570 Pge 1 of 8

2 Coordintion of nlyticl mesurements for the chrcteriztion of this SRM ws performed by D.A. Becker nd K.E. Shrpless of the NIST Anlyticl Chemistry Division. Anlyticl mesurements t NIST were performed by E.S. Bery, D.A. Becker, C.M. Beck II, M.S. Epstein, J.D. Fssett, K.M. Grrity, R.R. Greenberg, R.M. Lindstrom, E.A. Mckey, P. Morles, K.E. Murphy, P.J. Pulsen, B.J. Porter, T.A. Rush, R. Srswti, J.M. Smeller, G.C. Turk, R.D. Vocke, R.L. Wtters, Jr., nd L.J. Wood. Additionl elementl nlyses were performed by D.L. Anderson (Center for Food Sfety nd Applied Nutrition, U.S. Food nd Drug Administrtion, Wshington, DC), A.R. Byrne (Nucler Chemistry Deprtment, Jozef Stefn Institute, Ljubljn, Sloveni), nd J. Kucer (Nucler Physics Institute, Acdemy of Sciences of the Czech Republic, Rez, Czech Republic). Severl elements were lso mesured in n Interntionl Atomic Energy Agency (IAEA) interlbortory comprison exercise. Proximtes, clories, ftty cids, nd totl dietry fiber were determined by Covnce Lbortories (Mdison, WI), Lncster Lbortories (Lncster, PA), Medllion Lbortories (Minnepolis, MN), nd Southern Testing nd Reserch Lbortories (Wilson, NC). Sttisticl nlysis of the experimentl dt ws performed by W. Guthrie, S.B. Schiller, nd L.M. Gill of the NIST Sttisticl Engineering Division. NOTICE AND WARNINGS TO USERS Stbility: This mteril ws rdition sterilized t n estimted minimum dose of 27.8 kgy for microbiologicl control; however, its stbility hs not been rigorously ssessed. Spinch leves hve tendency to rpidly blech nd to turn tn or light brown color in the presence of visible light. Bsed on 15 yers experience with the originl SRM 1570, there is no evidence documenting ny chnge in elementl concentrtions s result of tht color chnge. However, NIST will monitor this mteril nd will report ny substntive chnges in certified vlues to the purchser. Storge: The mteril should be kept tightly closed in its originl bottle nd stored in the drk t temperture between 10 C nd 30 C. It should not be exposed to intense sources of rdition. Idelly, the bottle should be kept in desicctor under the conditions indicted bove. Instructions for Use: The contents of bottle should be thoroughly mixed by rotting nd/or rolling before ech use. Allow the contents to settle for 1 minute prior to opening to minimize the loss of fine dust prticles. A minimum smple mss of 150 mg of the mteril, dried s described in the section on "Instructions for Drying", should be used to relte nlyticl determintions to the certified vlues on this certificte. In some cses, especilly for voltile elements such s mercury, it is preferble to nlyze smples from the bottle without drying, determine the moisture content on seprte smple from the sme bottle tken t the sme time, nd convert the nlyticl results to dry-mss bsis. Digestion procedures should be designed to void loss of voltile elements, such s rsenic nd mercury. Digestion of the SRM in nitric nd perchloric cids ws found to be incomplete, with smll residue of siliceous mteril remining. This residue must be considered n integrl prt of this SRM nd should be dissolved with smll mount of hydrofluoric cid to obtin totl dissolution. All certified vlues re bsed on the totl dissolution. Instructions for Drying: Smples of this SRM must be dried by one of the following two procedures in order for certified vlues to be vlid: 1. Drying in desicctor t room temperture (pproximtely 22 C) for 120 h over fresh nhydrous mgnesium perchlorte. The smple depth should not exceed 1 cm. 2. Freeze-drying for 24 h t pressure of 13.3 P or lower nd shelf temperture of 5 C or lower fter hving frozen the smple (not to exceed 1 cm in depth) t 40 C or lower for t lest 1 h. At the end of the 24 h period, smples should be plced immeditely in desicctor with fresh nhydrous mgnesium perchlorte. Smples should be weighed fter llowing minimum of 4 h to estblish temperture equilibrium. Note: Vcuum drying t room temperture nd oven drying t elevted tempertures hve resulted in excessive mss losses nd therefore re NOT recommended. SRM 1570 Pge 2 of 8

3 Source nd Preprtion of Mteril: The mteril (pproximtely 2270 kg) for this SRM ws obtined from commercil supplier Oregon Freeze-Drying Corp., Albny, OR. It consists of U.S. Grde A chopped frozen spinch. The mteril ws thwed, plced in ribbon mixer, thoroughly mixed, nd blended. After mixing, the spinch ws freezedried. The freeze-dried mteril ws then ground in stinless steel grinder nd shipped to NIST. At NIST, the freezedried mteril ws sieved through polypropylene sieve hving openings of 0.25 mm (equivlent to U.S. Series 60 stndrd sieve). The sieved mteril ws then jet milled nd ir clssified to prticle size of pproximtely 75 μm (200 mesh). After mixing in lrge blender, the spinch ws irrdited with coblt-60 rdition to minimum bsorbed dose of pproximtely 27.8 kgy for microbiologicl control nd bottled. Homogeneity Assessment: Smples from rndomly selected bottles of SRM 1570 were tested for homogeneity by instrumentl neutron ctivtion nlysis (). No evidence of sttisticlly significnt inhomogeneity ws observed. Tble 1. Certified Concentrtion Vlues of Constituent Elements,b Element Mss Frction (%) Clcium ± Phosphorus ± Potssium ± Sodium ± Mss Frction Mss Frction Element (mg/kg) Element (mg/kg) Aluminum 310 ± 11 Mercury ± Arsenic ± Nickel 2.14 ± 0.10 Boron 37.6 ± 1.0 Selenium ± Cdmium 2.89 ± 0.07 Strontium 55.6 ± 0.8 Coblt 0.39 ± 0.05 Thorium ± Copper 12.2 ± 0.6 Vndium 0.57 ± 0.03 Mngnese 75.9 ± 1.9 Zinc 82 ± 3 b The certified concentrtions re eqully weighted mens of results from two or more different nlyticl methods or the men of results from single method of known high ccurcy. In the cse of two or more methods, ech uncertinty is the sum of 95 % confidence limit nd n llownce for systemtic error between the methods used. In the cse of method of known ccurcy, ech uncertinty is the sum of 95 % confidence limit nd the known systemtic error of the method. These certified vlues re reported on dry-mss bsis. For certified vlues to be vlid, the mteril must be dried ccording to the instructions provided bove. SRM 1570 Pge 3 of 8

4 Tble 2. Reference Concentrtion Vlues of Constituent Elements,b,c Element Mss Frction (%) Nitrogen (Totl) d 6.06 ± 0.20 Nitrogen (Orgnic) d 6.20 ± 0.25 Nitrogen (Protein) d 5.68 ± 0.13 Mss Frction Mss Frction Element (mg/kg) Element (mg/kg) Europium ± Rubidium 12.7 ± 1.6 Scndium ± Urnium ± b c d NIST hs replced the previously used term non-certified with reference vlue or informtion vlue, s pproprite. Ech reference concentrtion vlue, expressed s mss frction on dry-mss bsis, is n eqully weighted men of results provided by NIST nd/or collborting lbortories. The uncertinty in the reference concentrtion vlues is clculted s U = ku c. The quntity u c is the combined stndrd uncertinty clculted ccording to the ISO Guide [1], which ccounts for the combined effect of the within-lbortory vrince for ll prticipting lbortories t one stndrd devition nd bis between methods. The coverge fctor, k, is determined from the Student s t-distribution corresponding to the pproprite ssocited degrees of freedom nd 95 % confidence for ech nlyte. These reference vlues re reported on dry-mss bsis. In order for these reference vlues to be vlid, the mteril must be dried ccording to the instructions provided bove. Dt from three methods for the determintion of nitrogen hve been treted seprtely. Totl nitrogen ws determined by prompt gmm ctivtion nlysis; orgnic nitrogen ws determined by the Dums method; nd protein nitrogen ws determined by the Kjeldhl method. Tble 3. Reference Concentrtion Vlues of Selected Proximtes nd Totl Dietry Fiber Mss Frction, Mss Frction, Anlyte s received (%) dry-mss bsis (%) b Moisture c 3.45 ± (by definition) Solids c ± (by definition) Ash ± ± 0.38 Protein d 35.8 ± ± 3.1 Totl dietry fiber 30.5 ± ± 4.4 b c d Ech reference concentrtion vlue, expressed s mss frction on n s-received or dry-mss bsis, is n eqully weighted men of results from the lbortories shown in Appendix C. (NIST nd one of these lbortories provided results used in vlue ssignment of mss frctions of moisture nd solids; see footnote c.) The uncertinty in the reference vlues is expressed s n expnded uncertinty, U, t the 95 % level of confidence, nd is clculted ccording to the method described in the ISO Guide [1]. The expnded uncertinty is clculted s U = ku c, where u c is intended to represent, t the level of one stndrd devition, the combined effect of between-lbortory nd within-lbortory components of uncertinty. The coverge fctor, k, is determined from the Student s t-distribution corresponding to the pproprite ssocited degrees of freedom nd 95 % confidence for ech nlyte. Anlyticl methodology informtion is provided in Appendix B. Results hve been converted to dry-mss bsis using the reference vlue for solids. Uncertinty in the solids determintion hs been included in the uncertinties provided for the mss frctions on dry-mss bsis. Moisture hs been determined by NIST (using freeze-drying nd desicction) nd one of the collborting lbortories (using desicction) s specified in this certificte. Drying in forced-ir or vcuum oven by three lbortories resulted in moisture vlue of 6.3 % ± 1.5 %. The protein concentrtion ws clculted from the nitrogen vlues reported by the lbortories (two lbortories using the Dums method, two lbortories using Kjeldhl) using conversion fctor of The vlue for protein is the men of the individul protein clcultions reported by the lbortories shown in Appendix C. If the men nitrogen vlues bove re used for clcultion, the men protein concentrtions re 35.8 % nd 37.1 % on n s-received nd dry-mss bsis, respectively. SRM 1570 Pge 4 of 8

5 Tble 4. Informtion Concentrtion Vlues of Constituent Elements Element Mss Frction (%) Mgnesium 0.89 Sulfur 0.46 Element Mss Frction (mg/kg) Led 0.20 NIST hs replced the previously used term non-certified with reference vlue or informtion vlue, s pproprite. Tble 5. Informtion Concentrtion Vlues of Crbohydrte, Ft, Cloric Content, nd Selected Ftty Acids (s Triglycerides) Mss Frction, Mss Frction, Anlyte s received (%) dry-mss bsis (%) Crbohydrte b Ft 2 2 Clories b,c 340 kcl/100g 350 kcl/100g Pentdecnoic Acid (C15:0) Hexdecnoic Acid (C16:0) (Plmitic Acid) Heptdecnoic Acid (C17:0) (Mrgric Acid) Octdecnoic Acid (C18:0) (Steric Acid) (Z)-9-Octdecenoic Acid (C18:1) (Oleic Acid) (Z,Z)-9,12-Octdecdienoic Acid (C18:2) (Linoleic Acid) (Z,Z,Z)-9,12,15-Octdectrienoic Acid (C18:3) (Linolenic Acid) Linolenic Acid (C18:3) Docosnoic Acid (C22:0) (Behenic Acid) Tetrcosnoic Acid (C24:0) (Lignoceric Acid) b c These informtion vlues, reported on n s-received nd dry-mss bsis, re the eqully weighted mens of results reported by the collborting lbortories shown in Appendix C. These vlues re bsed on results from determintions by two to four of the lbortories nd re included to provide dditionl chrcteriztion of the mteril; no uncertinties re provided. Anlyticl methodology informtion is provided in Appendix B. These informtion vlues re clculted from the results reported by one lbortory. If the men proximte vlues in Tbles 2 nd 4 re used for clcultion, with cloric equivlents of 9, 4, nd 4 for ft, protein, nd crbohydrte, respectively, the men cloric content is 340 kcl/100 g nd 350 kcl/100g on n s-received nd dry-mss bsis, respectively. SRM 1570 Pge 5 of 8

6 REFERENCE [1] Guide to the Expression of Uncertinty in Mesurement, ISBN , 1st Ed. ISO, Genev, Switzerlnd, (1993); see lso Tylor, B.N. nd Kuytt, C.E., Guidelines for Evluting nd Expressing the Uncertinty of NIST Mesurement Results, NIST Technicl Note 1297, U.S. Government Printing Office, Wshington, DC, (1994); vilble t Certificte Revision History: 31 August 2001 (This technicl revision reports the ddition of reference nd informtion vlues for proximtes, clories, totl dietry fiber, nd ftty cids nd chnge from non-certified to reference nd informtion vlues for severl inorgnic constituents); 15 July 1996 (editoril chnge); 20 October 1994 (originl certificte dte). Users of this SRM should ensure tht the certificte in their possession is current. This cn be ccomplished by contcting the SRM Progrm t: telephone (301) ; fx (301) ; e-mil srminfo@nist.gov; or vi the Internet SRM 1570 Pge 6 of 8

7 Appendix A. Methods Used in Elementl Determintions Method Method Element Code Element Code Aluminum ICP Nitrogen DUMAS KJEL PGAA Arsenic FI-HGAAS Phosphorus COLOR ICP Boron IDICPMS Potssium IDTIMS PGAA Cdmium IDICPMS Rubidium IAEA PGAA Scndium IAEA Clcium IDTIMS Selenium FI-HGAAS Coblt Copper ICP Sodium PGAA Europium IAEA Strontium IDTIMS Led IAEA Sulfur PGAA IDICPMS IAEA Mgnesium IDICPMS Thorium Mngnese LEAFS Urnium Mercury CVAAS Vndium IDTIMS Nickel IDICPMS Zinc ICP SRM 1570 Pge 7 of 8

8 Acronyms for nlyticl methods: CVAAS = Cold-Vpor Atomic Absorption Spectrometry FI-HGAAS = Flow Injection Hydride Genertion Atomic Absorption Spectrometry IAEA = Interntionl Atomic Energy Agency Interlbortory Comprison Exercise ICP = Inductively Coupled Plsm Opticl Emission Spectrometry IDICPMS = Isotope Dilution, Inductively Coupled Plsm Mss Spectrometry IDTIMS = Isotope Dilution, Therml Ioniztion Mss Spectrometry = Instrumentl Neutron Activtion Anlysis KJEL = Kjeldhl Nitrogen Determintion LEAFS = Lser-Excited Atomic Fluorescence Spectrometry PGAA = Prompt Gmm Activtion Anlysis = Rdiochemicl Neutron Activtion Anlysis Appendix B. Methods Used in the Determintion of Proximtes, Cloric Content, Ftty Acids, nd Totl Dietry Fiber Ash mss loss fter ignition in muffle furnce Clories clculted; [(9 ft) + (4 protein) + (4 crbohydrte)] Crbohydrte clculted; [solids (protein + ft + sh)] Ft sum of individul ftty cids Ftty cids hydrolysis followed by gs chromtogrphy Moisture mss loss fter drying t room temperture in desicctor (1 lbortory + NIST); freeze-drying (NIST) Nitrogen Dums (1 lbortory); modified Dums (1 lbortory); Kjeldhl (2 lbortories + NIST) Protein clculted from nitrogen reported by 4 lbortories using fctor of 6.25 Solids clculted; (smple mss moisture) Totl dietry fiber enzymtic digestion followed by grvimetry Appendix C. Collborting Lbortories for Proximte, Ftty Acid, Totl Dietry Fiber, nd Cloric Determintions Covnce Lbortories, Mdison, WI, USA Lncster Lbortories, Lncster, PA, USA Medllion Lbortories, Minnepolis, MN, USA Southern Testing nd Reserch Lbortories, Wilson, NC, USA SRM 1570 Pge 8 of 8