METROLOGICAL COMPATIBILITY OF THE MEASURING RESULTS OF AQUEOUS SOLUTIONS MASS FRACTIONS BY DENSIMETRY AND REFRACTOMETRY

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1 METROLOGICAL COMPATIBILITY OF THE MEASURING RESULTS OF AQUEOUS SOLUTIONS MASS FRACTIONS BY DENSIMETRY AND REFRACTOMETRY A. FURTADO, C. OLIVEIRA, O. PELLEGRINO, C. PEREIRA, C. MATEUS, A. QUEIRÓS, R. CONCEIÇÃO, E. FILIPE Joint IMEKO International TC8, TC23 and TC24 Symposium 2013 DMET

2 VIM 3rd edition International Vocabulary of Metrology (JCGM 200:2012) I. Reviewing concepts Basic principles governing quantities and units Published by the BIPM No fundamental in the basic principles of measurement in several sciences: physics, chemistry, medicine, biology, or engineering An attempt has been made to meet conceptual needs of measurement in fields such as: biochemistry, food science, forensic science, and molecular biology

3 I. Reviewing concepts Measurand (VIM 2.3) - quantity intended to be measured (VIM 1.1) Ex: length of a steel rod at 23 C May be generically divided into: base and derived property of a phenomenon, body, or substance, that can be expressed as a number and a reference measurement unit measurement procedure reference material combination of such In chemistry - analyte sometimes used for measurand however these terms do not refer to a quantity Ex: one cannot measure glucose but can measure the glucose concentration - "glucose" is the component and "concentration" is the measurable property physical, chemical, and biological

4 I. Reviewing concepts Metrological compatibility (of measurement results) (VIM 2.47) Property of a set of measurement results for a specified measurand, such that the absolute value of the difference of any pair of measured quantity values (y i, y j ) from two different measurement results is smaller than some chosen multiple (k) of the standard measurement uncertainty of that difference (u yi-yj ) For measurements results (yi, yj) completely uncorrelated: the standard measurement uncertainty of their difference (uyi-yj) is equal to the root mean square sum of their standard measurement uncertainties (uyi, uyj) 4

5 II. Introduction n ratio of the speed of light in vacuum (c 0 ) by the speed of light in the substance (c) * SI derived unit 1 *According to ISO :2008(E) - Ligth n C 0 c Quantity of dimension one or dimensionless quantity r - mass (m) per unit volume (V)* *According to ISO :2006(E) - Mechanics r SI derived unit kg/m 3 m V Decimal multiples and submultiples of SI units: g/cm 3 and g/dm 3 Non-SI units accepted for use with the SI: g/ml and g/l

6 II. Introduction Juices, soft drinks and other sugary compounds Density Mass fraction in sugar BRIX SI cg sucrose/g sol. Grape must Refractive index Mass fraction in sugar Potencial Volume Fraction in alcohol % vol. SI cl ethanol/l sol. Seawater Mass fraction in salts Salinity ( ) SI - g salt/kg sol.

7 II. Introduction Refractive index X mglucose (n) X mnacl (n) Reference solutions Mass fraction in: Glucose NaCl??? X mnacl (r) Density X mglucose (r)

8 III. Experimental Methodologies Measuring Principle Measuring Principle Snell-Descartes Law 1. cell with the sample 2. LED = 589,3 nm 3. refraction in solution 4. measurement of critical angle with CCD 5. n determination Law of Harmonic Oscillation 1. U-tube with a sample t 2 rv m C 2. electromagnetic force 3. measurement of vibration period (t) 4. r determination

9 III. Experimental methodologies Features RE 50, Mettler Toledo DMA 5 000, Anton Paar 1. Sample Volume 2 ml 10 ml Time 20 min 20 min 2. Quantities Measuring interval Refractive index Density 1, a 1, (0,000 a 3 000,000) kg/m 3 Resolution 0, ,001 kg/m 3 3. Temperature Measuring interval (15,00 a 40,00) ºC (0,000 a 90,000) ºC Resolution 0,01 ºC 0,001 ºC

10 III. Experimental methodologies Refractometry n - NIST and LGC Standards t - Laboratory of Temperature - IPQ Densimetry r - PTB, NIST, GUM and H&D Fitzgerald t - Laboratory of Temperature - IPQ

11 III. Experimental methodologies Gravimetric preparation Glucose NaCl 8 solutions X m from 3 cg/g to 40 cg/g (ref. table) 4 solutions X m from 7 cg/g to 26 cg/g (sat.)

12 III. Experimental methodologies n = 1 j j n i=1 n i +C n Glucose Official Journal of the European Communities, L 272 de , 1 Reference data (n i, X m (n i )) X m (n) X m (n) = a 0 + a 1 Linear regression 1 j j n i=1 n i +C NaCl Wolf, A. V., Aqueous Solutions and Body Fluids, Hoeber, 1966

13 III. Experimental methodologies ρ = 1 n n ρ ρ i=1 i +C r Glucose Circular of the National Bureau of Standards, C440, 632, 1942 Reference data (r i, X m (r i )) X m (r) X m (r) = b 0 + b 1 Linear regression 1 n n ρ ρ i=1 i +C NaCl Söhnel, O., and Novotny, P., Densities of Aqueous Solutions of Inorganic Substances, Elsevier, Amsterdam, 1985

14 IV. Uncertainty budget Sources of Uncertainty of X m u interpolation u linear regression u reference data u Xm(n) u dispersion u t u resolution u cal (RE 50) u Xm(r) u t u cal (DMA 5 000) u n u r u CRMs u dispersion Uncertainties calculated according to ISO/IEC Guide 98-3:2008 Uncertainty of measurement - Part 3: Guide to the expression of uncertainty in measurement (GUM:1995)

15 V. Results X m(n) X m(ρ) 2 u 2 Xm(n) + u 2 Xm(ρ) Mass fraction (cg/g) of glucose at 20 ºC X m Solution X m ± U (k = 2) X m = X m(n) X m(ρ) 2 u 2 Xm(n) + u 2 Xm(ρ) Refractometry Densimetry 1 3,16 ± 0,10 3,23 ± 0,10 0,07 0,51 2 5,73 ± 0,10 5,79 ± 0,10 0,06 0, ,50 ± 0,10 10,43 ± 0,10 0,07 0, ,64 ± 0,10 11,66 ± 0,10 0,02 0, ,56 ± 0,10 19,56 ± 0,10 0,00 0, ,80 ± 0,10 26,78 ± 0,10 0,02 0, ,66 ± 0,10 34,65 ± 0,10 0,01 0, ,36 ± 0,10 40,28 ± 0,10 0,08 0,55 Compatible results (VIM 2.47)

16 V. Results X m(n) X m(ρ) 2 u 2 Xm(n) + u 2 Xm(ρ) Solution Mass fraction (cg/g) of NaCl at 20 ºC X m ± U (k = 2) X m = X m(n) X m(ρ) X m 2 u 2 Xm(n) + u 2 Xm(ρ) Refractometry Densimetry 1 7,0 ± 0,3 7,02 ± 0,01 0,01 0, ,9 ± 0,6 12,75 ± 0,01 0,18 0, ,6 ± 0,9 19,76 ± 0,01 0,14 0, ,1 ± 1,1 26,10 ± 0,01 2,03 1,77 1 > 1 Compatible results (VIM 2.47) Non compatible results

17 VI. Conclusions and Remarks Glucose NaCl Values of X m glucose compatible with the input quantities r e n in the range of [3; 40] cg/g Values of X m NaCl compatible with the input quantities r e n in the range of [7; 20] cg/g But not in the range of [21; 26] cg/g Alternative methodologies for X m glucose determination? Alternative methodologies for X m NaCl determination in the range of [7; 20] cg/g? Why? More tests need to be performed

18 VI. Conclusions and Remarks The metrological compatibility of the measuring results of glucose X m obtained by the two different methodologies (refractometry and densitometry) was well established... Were used the conversion tables adopted by the manufacturers of the measuring instruments Further studies use the latest tables ICUMSA for r and 2000 for n (International Commission for Uniform Methods of Sugar Analysis) Will the results remain compatibles?

19 VI. Conclusions and Remarks The metrological compatibility of measuring results of NaCl X m above 21 cg/g need to be studied Due to its interest for the food science, health science, and oceanography Speed of sound measurements of the salty solutions could be an alternative methodology?

20 VII. References [1] A.Furtado, O.Pellegrino, S.Alves, I.Spohr, E.Filipe, Determinação da fracção mássica de soluções aquosas de glucose por refratometria e densimetria de tubo vibrante, Livro de Resumos da CONFMET2010, Medições na Ciência e na Tecnologia, SPMET, SPQ e RELACRE, [2] Circular of the National Bureau of Standards, C440, 632, [3] International vocabulary of metrology-basic and general concepts and associated terms JCGM 200: rd edition (2008 version with minor corrections). [4] ISO/IEC Guide 98-3:2008 Uncertainty of measurement - Part 3: Guide to the expression of uncertainty in measurement (GUM:1995). [5] ISO :2006(E) - Quantities and units -- Part 4: Mechanics. [6] ISO :2008(E) - Quantities and units -- Part 7: Light. [7] Official Journal of the European Communities, L 272 de , 1. [8] Söhnel, O., and Novotny, P., Densities of Aqueous Solutions of Inorganic Substances, Elsevier, Amsterdam, [9] Wolf, A. V., Aqueous Solutions and Body Fluids, Hoeber, 1966.

21 Thank you! Andreia Furtado 21