Nutrient

EuroFIR guidelines for assessment of Methods of Analysis Nutrient Sodium (Na) is a metal with an atomic mass of 23. It is found widely in nature and as a normal constituent of foods. It is added to foods, most frequently as sodium chloride (NaCl), common known as salt (1 mmol is equivalent to 23 mg sodium and approximates 58 mg sodium chloride), but also as other salts, e.g. nitrate, nitrite, phosphates, glutamate. In drinking water, the guide level of sodium is 20 mg/L (Council Directive 80/778/EEC) Golden Standard prEN 15505 Foodstuffs - Determination of trace elements - Determination of sodium, magnesium and calcium by flame atomic absorption spectrometry (AAS) after microwave digestion NKML 180, 2005 Sodium. Determination in Foodstuffs by Flame Atomic Absorption Spectrometry after Microwave Digestion AOAC 984.27 -Calcium, Copper, Iron, Magnesium, Manganese, Phosphorus, Potassium, Sodium, and Zinc in Infant Formula- Inductively Coupled Plasma Emission Spectroscopic Method Method Indicator Name Code Scope Determination of Sodium in foodstuffs in all relevant matrix successfully tested in laboratory proficiency testing. Principle Edible parts are grinder and homogenised in suitable apparatus. The organic matrix are removed by microwave digestion, or dry washing. The Sodium content is determined by flame photometry (FF),flame atomic absorption spectrometry-procedures( AAS) or by Inductively coupled plasma atomic emission spectroscopy (ICP-AES) also refered as Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). Key steps  Preparation o The edible part needs to be separate from the foodstuffs ( EN 13804:2002 provide examples of sample preparation from foodstuffs)  Homogenization o Edible parts are grinder in suitable apparatus (coffee grinder or kitchen grinder; stainless steel vegetable slice; plastic salad spinner and homogenised; _________________________________________________________________________________ Methods of analysis for C 1/6 EuroFIR guidelines for assessment of Methods of Analysis o To avoid contamination the apparatus equipped with titanium or ceramics knives, agate mortar or ball mill can be used for size reduction and homogenisation( EN 13804:2002 is the reference standard for sample preparation  Separation Organic matrix are removed or extracted : o Pressure digestion: The sample dissolved in concentrated acid are digested in a sealed vessel in a pressure container at high temperature and pressure by conventional or microwave assisted heating. (EN 14084:2003 Foodstuffs). The method is described for AAS and ICP OES. Dry ashing : Sample in a crucible made by platinum is incinerated heating gentling in a muffle furnace at controlled temperature 450 ºC  25 ºC. Final residue redissolved in nitric acid .( EN 14082:2003). The method is described for AAS and FF o  Detection o The instrumental parameters for flame AAS  Flame: Air acetylene, oxidising  Wavelength 589.6 nm The instrumental parameters for ICP-OES  Wavelength 330,235 nm; Interferences: Zn Limit of Quantification: (radial o   viewing 20 ; axial viewing 300 ) Wavelength 588,995 nm ; Ar, V interferences; Limit of Quantification: (radial viewing 20 ; axial viewing 200) Wavelength 589,592 nm ; Ba interferences; Limit of Quantification: (radial viewing 93 ; axial viewing 20)  Quantification o AAS  After instrument response is stable the linearity, sensitivity and limit of quantification verified. The content of Sodium in sample is determined from calibration curve by plotting (absorbance (A) peak area ) against concentration. The calibration curve is prepared with at least five points using concentrations of standard solutions within working range. o ICP OES  After verification of instrument performance (drift; interferences, background correction). The content of Sodium in sample is determined from linear regression method using blank, standard solutions and , internal standards _________________________________________________________________________________ Methods of analysis for C 2/6 EuroFIR guidelines for assessment of Methods of Analysis Criteria for analytical performance and Analytical Quality control  Method Performance NMKL interlaboratory study (Julshamn K, Lea P, Norli HS, 2005) Nine laboratories participated in an interlaboratory method performance (collaborative) study of a method for the determination of sodium in foods by flame atomic absorption spectrometry after wet digestion, using a microwave oven technique. The method was tested on a total of 6 foods (broccoli, carrot, bread, saithe fillet, pork, and cheese) with sodium concentrations of 1480-8260 mg/kg. The repeatability relative standard deviations (RSDr) for sodium ranged from 1.9 to 6.5%. The reproducibility relative standard deviations (RSDR) ranged from 4.2 to 6.9%. The HorRat values ranged from 0.9 to 1.6.  Certified Reference Materials/Standard Reference Material(www.comar.bam.de) LGC 7104 NIST 2384 LGC 7112 NIST 2387 GBW 08552 LGC 7000 LGC 7001 NIST 1546 NIST 8415 BCR 381 BCR 383 GBW 07605 LGC 7103 NIST 1567a NIST 1568a NIST 2383 NIST 8432 NIST 8433 NIST 8436 VMA 195 VMA 399 LGC 7105 NIST 1548a Sterilized cream Baking chocolate(reference value) Pig liver Paste Peanut Butter Freeze dried Pork Muscle Beef Pork Meat Mackerel Paste Meat Homogenate(reference value) Whole Egg Powder(reference value) Rye Flour Freeze Dried Green Beans Tea Sweet digestive Biscuit wheat Flour Rice Flour Baby Food(reference value) Corn Starch (reference value) Corn Barn(reference value) Durum Wheat Flour(reference value) Cereal Cereal Rice Pudding Freeze Dried Mixed Diet 3/6 _________________________________________________________________________________ Methods of analysis for C EuroFIR guidelines for assessment of Methods of Analysis NIST 1846 NIST 8435 LGC 7001 NIST 1549 NIST 1566b NIST 1570a NIST 2385 NIST 1946 LGC 7160 NIST 1577b NIST 3244 NIST 8418 Infant Formula(reference value) Whole Milk Powder(reference value) Pork Meat Non- Fat Milk Powder Freeze Dried Oyster Tissue Freeze Dried Spinach Leaves Slurried Spinach Fish Tissue(reference value) Crabe Paste Freeze Dried Bovine liver Protein Powder wheat gluten (reference value)  Proficiency Testing Schemes (www.eptis.bam.de) o 19 datasets are register at eptis and the following matrix  wine, water, milk powder, canned meat, fruit juice, plants, premix, cheese processed, meat products, dietary supplement Other methods available  AOAC 984.27- Calcium, Copper, Iron, Magnesium, Manganese, Phosphorus, Potassium, Sodium, and Zinc in Infant Formula- Inductively Coupled Plasma Emission Spectroscopic Method    AOAC 985.35- Minerals in Infant Formula Enteral Products and Pet Foods – Atomic Absorption Spectrometric Method AOAC 969.23 - Flame Photometric Method Sodium and Potassium in Seafood IDF-ISO-AOAC 990.23 - Flame Emission Spectrometric Method- Sodium and Potassium in Dried Milk  (CodexStan 234-1999)-Recommended methods of analysis Method Reference Component Sodium Matrix Special foods ISO 8070:1987(confirmed 1992) IDF Standard 119A:1987 AOAC 984.27 AOAC 971.27 (Codex general method) Described in the Standard AOAC 971.27 (Codex general method) Principle Flame emission spectrophotometry ICP emission spectrometry Potentiometry Type II Sodium Sodium chloride Sodium chloride Sodium chloride Special foods Bouillons and consommes Food grade salt Margarine III II Calculation Potentiometry I II _________________________________________________________________________________ Methods of analysis for C 4/6 EuroFIR guidelines for assessment of Methods of Analysis Sodium chloride Sodium chloride Sodium chloride Minarine Processed tomato concentrates Quick frozen blocks of fish fillet, minced fish flesh and mixtures of fillets and minced fish flesh Quick frozen fish sticks (fish fingers) and fish portions Breaded or in batter AOAC 971.27 (Codex general method) AOAC 971.27(Codex general method) AOAC 971.21 (Codex general method) Potentiometry Potentiometry II II Potentiometry II Sodium chloride AOAC 971.27 (Codex general method) Potentiometry II Salt Butter IDF Standard 179:1997 AOAC 971.27 (Codex general method) Potentiometry (determination of chloride, expressed as sodium chloride) Potentionmetry (determination of chloride, expressed as sodium chloride) Potentiometry III Salt Processed cheese products IDF Standard 88A:1979 ISO 5943:1988 (confirmed 1996) AOAC 983.14 II Salt Salt Salt, Salt, Salt in brine Pickled cucumbers in brine Table olives added Fruit juices added Fruit juices Butter AOAC 971.27(Codex general method) AOAC 971.27(Codex general method) AOAC 971.27 (Codex general method) IFJU Method No 37, 1968 IDF Standard 12B: 1988 ISO 1738:1997 AOAC 960.29 II Potentiometry Potentiometry Electrochemical titrimetry Titrimetry (Mohr: determination of chloride, expressed as sodium chloride) II II III II Remarks  Compatibility of old data o All the methods give comparable results _________________________________________________________________________________ Methods of analysis for C 5/6 EuroFIR guidelines for assessment of Methods of Analysis o Flame photometry can be used with very good results demonstrated in PT schemes although mutual interference from calcium can occur(Chen 2005) o Overestimation of sodium concentration is reported in foods with low level of sodium when analysis are carried out by ICP-OES References  Deharveng G., Charrondière UR, Slimani N., Southgate DAT., Riboli E. (1999) Comparison of nutrients in food composition tables available in the nine European countries participating in EPIC. European Journal of Clinical Nutrition 53, 60-79 Julshamn K, Lea P, Norli HS.(2005).Determination of sodium in foods by flame atomic absorption spectrometry after microwave digestion: NMKL interlaboratory study. J AOAC Int. 88(4):1212-6. Greenfield H, Southgate DAT (2002) Food Composition Data – Production, Management and Use. Elsevier Applied Science, London, UK Cook KK. (1997). Extension of dry ash atomic absorption and spectrophotometric methods to determination of minerals and phosphorus in soy-based, whey-based, and enteral formulae (modification of AOAC Official Methods 985.35 and 986.24): collaborative study. J AOAC Int.;80(4):834-44 Chen,M.-J. Hsieh, YT, Weng Y-M, Chiou R. Y.-Y. (2005). Flame photometric determination of salinity in processed foods Food Chemistry, 91, (4) 765-770     EuroFIR assistance to this method/guidelines _________________________________________________________________________________ Methods of analysis for C 6/6