Studies of Total, Organic and Inorganic Iodine Species by - - PowerPoint PPT Presentation

Studies of Total, Organic and Inorganic Iodine Species by Instrumental and Preconcentration Neutron Activation with Compton Suppression Spectrometry

• A. Chatt

Trace Analysis Research Centre Department of Chemistry Dalhousie University Halifax, Nova Scotia, B3H 4J3 Canada

Safe LOW Power Kritical Experiment (SLOWPOKE)

Univ_Milano_Fisica_Chatt_Seminar_Iodine_2012_10_11

Oceanic sediments Iodine Geochemical Cycle

• 70% of iodine in earth’s crust is found

in oceanic sediments.

Atmosphere Land Soils

• It is transformed into CH3I by marine
• rganisms, and transported into the

atmosphere.

• From the atmosphere it could

return to the ocean or to the land.

• In land, one part is released as CH3I by

plants, another remains in soils or goes back to oceans through rivers

• It returns to oceans through

brines and also by organic activity from subducting sediments

Muramatsu et al, Earth Planet. Sci. Lett, 192 (2001) 583-593

Iodine

It was accidentally discovered in 1811 by Bernard Curtois. iod (violet) and ine for its chemical resemblance to bromine and chlorine. It is an essential micronutrient for humans. Lack of it produces iodine deficiency disorders (IDD). WHO estimates that about 1.6 billion people are afflicted by IDD; 1% of whom suffers from cretinism. WHO has set the Recommended Dietary Allowance (RDA) of iodine as: 50 g d-1 from 0 to 6 month 90  g d-1 from 6 month to 6 years 120 g d-1 from 7 to 10 years 150 g d-1 > 10 years 200-300 g d-1 during pregnancy and lactation

Introduction

RDA and RNI values for some countries U.K. (140 g d-1) USA, EU, Australia (150 g d-1) Canada (160 g d-1)

The daily average intake of iodine in Canada has been estimated as 6 times the Recommended value.

Sources of iodine for humans

Seafoods

Milk

Iodized table salt (76 ppm) Q: What are the reasons for this high iodine intake in Canada since late 80’s? A: Iodine levels in milk increased significantly since 1970’s Milk is one of the major contributors of iodine (~30%)

Introduction

http://www.dairyinfo.agr.ca, Average: 7–8 L per month per person

10 20 30 40 50 60

Years Annual sales (L) divided by Canadian population

Whole, 3.25% Partially 2% Partially 1% Skimmed Chocolate Buttermilk

A glass of milk (250 mL) contains about 125 µg of iodine which is

• approx. 78% of the Canadian RNI.

Health Canada recommends that adults take 4 glasses of milk per day. This will lead to an intake of 500 µg iodine per day which is half of the Provisional Maximum Tolerable Daily Intake (PMTDI) recommended by FAO and WHO.

Introduction

Iodine Isotopes: 115I - 141I

Nuclide Half-life Production/Usage 123I

13.1 h Diagnosis in nuclear medicine

125I

60.14 d Diagnosis, RIA

127I

STABLE

128I

25 min Iodine determination by NAA

129I

1.59 x 107 a Fission product of high yield

130I

12.36 h Fission product of high yield

131I 8.041 d Diagnosis and therapy in nuclear

medicine

132I 2.285 h

Fission product of high yield

133I

20.8 h Fission product of high yield

The most used and/or important

Methods for Iodine Determination

Year Method Detection Limit, ppb 1920’s Colorimetric 50 1940’s Electrochemical 50 1970’s GC 10 1970’s INAA 30 1970’s PNAA 12 1970’s RNAA 2 1980’s LC 100 1990’s ICP-MS / ID-MS 4

0.16 g Branching ratio (147  6) b Resonance integral 443 keV g Energy (6.2  0.2) b Thermal n cross-section 25.0 min Half-life 100% Isotopic abundance Product nuclide: 128I Target nuclide: 127I

Nuclear reaction: 127I(n,g)128I

Principles of NAA

Classification of NAA Techniques

Sample is retained, minimum reagent blanks Very Low levels can be measured, no reagent blanks High precision and accuracy Interference eliminated before irradiation Sensitive measurement

• f non-

sensitive elements Simultaneous speciation

Non-destructive or Instrumental Analysis (INAA) Radiochemical Separation (RNAA) Preconcentration (PNAA) Derivative (DNAA)

Neutron Activation Analysis (NAA)

Speciation (SSNAA) Destructive Pre-irradiation Separation

Advantages:

Advantages of SSNAA

Simultaneous multielement specificity Simultaneous speciation of elements which are not chemically similar Simultaneous speciation of elements which are rather difficult to determine by other techniques Virtually free from matrix interferences Applicable to solids and liquids

Advantages of SSNAA

 Almost all the elements can be determined  Qualitative as well as quantitative analysis  Excellent sensitivity and detection limits  High precision (low overall uncertainty)  Excellent accuracy  Extensive linear range (ppb to percent)  Small sample size  Can be combined with preconcentration steps  No effect on species change

Advantages of SSNAA

Enhanced quality assurance capabilities 3-D spectroscopy alternative nuclides alternative gamma-rays various decay times multiple counting

Comparison of experimental conditions, sensitivities and detection limits for iodine in different matrices

Detection limits (mg kg-1)

Neutron shield Irradi- ation site ti:td:tc (min) Sensi- tivity (counts /g)

NIST SRM-1549 (Non-fat Milk Powder) NIST SRM-1566 (Oyster Tissue) NIST SRM-1572 (Citrus Leaves) IAEA CRM H-9 (Human Mixed Diet)

None Cd-site 20:3:20 2177 0.24 0.31 0.17 0.18 None Cd-site 10:1:10 640 0.30 0.35 0.24 0.26 Cd-bottom (1 mm thick) Cd-site 10:1:10 636 0.28 0.34 0.23 0.24 Flex/boron (3.2 mm thick) Thermal 20:6:20 1600 0.24 0.17 0.11 0.15 Flex/boron (3.2 mm thick) Cd-site 20:3:20 1372 0.12 0.16 0.10 0.13 Thick boron (5 mm thick) Thermal 20:3:20 1408 0.11 0.14 0.09 0.10

Iodine content of selected biological reference materials by EINAA (in ng g-1, dry weight basis)

Material

• No. of

measurements This work (Mean  SD) Agency Value Literature Values NIST SRM-1549 (Non-fat Milk Powder) 8 3115  170 3380  20 3710  140, 3150  75 3200  300, 3500  84, 3200 NIST SRM-1566 (Oyster tissue) 6 2735  215 2800 b 3209  134, 2500  200, 2720  200, 2800  300 NIST SRM-1572 (Citrus Leaves) 8 1760  165 1840  30 1290  50, 1870  60, 1890  45, 1460 NIST RM-8415 (Whole Egg Powder) 8 1900  180 1970  460 2040  200, 1875  94 NIST RM-8435 (Whole Milk Powder) 8 2400  260 2300  400 2377  70 NIST SRM-1570 (Spinach) 6 1180  100 c  1325  55, 1080  160, 1160  40, 1200  120 NIST RM-8431 (Mixed Diet) 6 690  40 c  813  55 IAEA CRM H-9 (Mixed Human Diet) 6 370  45 c  407  17, 372  30, 382  23 NIST RM-8418 (Wheat Gluten) 6 65  11 c 60  13 59  3, 62  4

a irradiated in Cd-site only; b information value; c irradiated with Flex/boron shields in Cd-site

Results

• The lowest detection limits for all materials were
• btained with the 5.0mm thick boron shields

followed by the Flex/boron shield and Cd-site combination, as expected.

• The 5.0-mm B4C loaded polymer container gave the

best results. However, the mechanical integrity of these containers was not that great and they started to chip off on repeated use.

• Nevertheless, these containers were useful to

determine iodine levels down to 200 ppb.

• The 3.2-mm B4C loaded Flex/boron shields in

combination with the Cd-site are the next best to analyze samples down below 500 ppb.

The background observed in a γ-ray spectrum has two components: specific background peaks and the Compton continuum. The specific background peaks are due to radioactive isotopes present in the environment (i.e. members of the natural decay series, very long-lived nuclides, products of interactions with cosmic radiation), and artificially produced nuclides. All background nuclides and, often of greater importance, all nuclides in the sample contribute to the Compton continuum which results from the partial absorption of photons

Interaction of Gamma Radiation with Matter

The purpose of anti-coincidence counting is the reduction

• f the Compton continuum (i.e. the background under

peaks of interest). Anti-coincidence γ-ray spectrometers consist in part of a "principal" detector crystal surrounded as completely as possible by a second detector (known as the "guard" detector) which is used to detect scattered radiation. Anti-coincidence refers to the electronic treatment of the signals coming from these two detectors. The signal from the principal detector, in general terms, produces the spectrum while the signal from the guard detector is used to gate the principal signal either "on" or "off" prior to its reaching the MCA.

Anti-coincidence

Performance of the DUSR Anti-coincidence System

System P/Cp P/Ce P/Ta Conventional 93.4 89.5 0.07 Anti-coincidence 582 410 0.17 Improvement Ratio 6.26 4.58 2.43 P/Cp: Peak-to-Compton plateau (Cp 358-382 keV) P/Ce: Peak-to-Compton edge (Ce 475-481 keV) P/Ta: Peak-to-total area Nuclide: 137-Cs Worst case scenario

Comparison of detection limits (ppb) for iodine in three SRMs using Conventional and Anticoincidence counting systems

___________________________________________________________________________ Detection Counting Non-Fat Milk Powder Bovine Liver Rice Flour limits mode (NIST SRM 1549) (NIST SRM 1577b) (NIST SRM 1568a) ___________________________________________________________________________ LC conv. 1.1 × 102 6.8 × 101 3.5 × 101 anti. 6.7 × 101 3.0 × 101 1.0 × 101 LD conv. 2.1 × 102 1.4 × 102 7.2 × 101 anti. 1.3 × 102 6.2 × 101 2.1 × 101 LQ conv. 6.7 × 102 4.4 × 102 2.4 × 102 anti. 4.3 × 102 1.7 × 102 8.2 × 101 ___________________________________________________________________________

Improvement of detection limit in the cummulative approach

0.01 0.02 0.03 0.04 0.05 0.06 0.07

1 2 3 4 5 6 7

Number of cycle Detection limit

s

PC-EINAA-CSS

Scheme ti-td-tc (min) Reactor position / Detection system Iodine content g.mL-1, (%RSD) Detection Limit (g.mL-1) 5-2-10 INAA-Ge 0.34  0.2 (6) 0.08 5-2-10 INAA-CSS 0.342  0.008 (2) 0.06 5-6-15 PC-INAA-CSS (n=6) 0.341  0.008 (2) 0.02 25-5-25 EINAA-CSS 0.344  0.006 (1) 0.06 10-3-10 EINAA-CSS 0.34  0.2 (6) 0.1 10-3-10 PC-EINAA-CSS (n=6) 0.340  0.004 (<1) 0.008

Precision and detection limits of INAA methods for iodine in milk

Comparison of Iodine Concentration in Select Dairy Products

100 200 300 400 500 600 700 800 900 1000 A05 A06 A08

Dairy Products HWC Code Iodine Concentration (ppb) HWC Code Food Type

A05 EVAPORATED MILK, CANNED A06 CREAM A08 YOGURT

Comparison of Iodine Concentration in Meats

20 40 60 80 100 120 B01 B05 B08 B10 B12 C03

Meat and Meat product HWC Codes Iodine Concentration (ppb) HWC Code Food Type

B01 BEEF, STEAK B05 PORK, CURED B08 COLD CUTS AND LUNCHEN MEATS B10 ORGAN MEATS, LIVER & KIDNEY B12 GOAT, ROAST C03 CORNISH HEN

Comparison of Iodine Concentrations in Seafood

50 100 150 200 250 300 D02 D04

Seafood HWC Codes Iodine Concentration (ppb) HWC Code Food Type

D02 FISH, FRESH WATER, ... D04 SHELLFISH, FRESH OR FROZEN

Comparison of Iodine Concentrations in Vegetables and their Products

0.0 20.0 40.0 60.0 80.0 100.0 120.0 G01 G02 G04 G05 G06 G07 G09 G11 G13 G15 G16

Vegetable HWC Codes Iodine Concentration (ppb) HWC Code Food Type

G01 BAKED BEANS G02 BEANS G04 BROCCOLI G05 CABBAGE G06 CARROTS G07 CAULIFLOWER

HWC Code Food Type

G09 CORN G11 LETTUCE G13 ONION G15 PEPPERS G16 POTATOES, RAW

Determination of Iodine by Preconcentration and Radiochemical Neutron Activation Analysis

Chemical Separation of Iodine

 Microwave digestion of samples  Selection of a coprecipitating agent  Bismuth sulfide coprecipitation method  Preconcentration using bismuth sulfide coprecipitation  Preconcentration by toluene extraction  Radiochemical separation using bismuth sulfide coprecipitation  Radiochemical purification using palladium iodide

Bismuth Sulfide Coprecipitation Procedure

Adjust the acidity of the digested sample solution to 0.2 M by dilution with de-ionized distilled water (DDW) Stir the solution using a magnetic stirrer Add dropwise 1 mL of Bi(NO3)3 solution (40 mg/mL Bi3+), and 1 mL of thioacetamide solution (8.5 mg/mL S2-)

Filter the dark brown Bi2S3 precipitate through a pre-cleaned Gelman Sciences membrane filter under vacuum suction Wash the precipitate with 3 x 5 mL portions

• f 0.2 M HNO3 solution containing 0.1%

hydrazine sulfate Allow the contents to settle for 20 min at room temperature

Count for 30 min and quantify iodine through the 443-keV photopeak of 128I Irradiate the vial for 30–60 min at an epi-Cadmium neutron flux of 5.2x109 cm-2s-1 Fold the filter and keep in a pre-cleaned 1.2 mL polyethylene vial and heat-seal

Effect of Diverse Ions

Ion Decontamination Factor Tolerance Limit Pb2+ 40 mg Cu2+, Fe2+ As3+, Sb3+ > 102 10 mg Fe3+, Cr3+ > 104 40 mg Al3+, Co2+, Mn2+ > 104 5 mg Ni2+, Zn2+ > 104 40 mg Na+ > 106 100 mg SO4

2-

2 g Cl-, Br- > 103 2 mg Volume of sample solution = 100 mL; Acidity of solution = 0.2 M Bismuth ion added = 40 mg; Sulfide ion added = 8.5 mg Iodide ion added = 100 ng

Concentration of Iodine in Materials and Chemicals

Material Iodine content (ng/g or ng/mL) De-ionized Distilled Water < 0.01a 0.1b Polyethylene Vial < 1a 20-100b Gelman Sciences Membrane Filter < 0.5 – 1a 10 – 25b Hydrazine sulfate < 1a

a Fresh material b Material kept in the laboratory for several weeks

This work (ng/g, dry weight)* Material Preconcentration by toluene extraction followed by Bi2S3 coprecipitation Radiochemical separation by Bi2S3 coprecipitation Preconcentration with Bi2S3 coprecipitation followed by radiochemical purification with PdI2

Bovine Liver NIST SRM-1577 198  10 208  12 203  6 Orchard Leaves NIST SRM-1571 171  6 174  8 172  4 Milk Powder IAEA A-11 94  8 92  6 90  6 Animal Muscle IAEA H-4 16  2 18  2 17  2 Potato Powder Finland RM-127 4.2  0.3 3.9  0.3 3.8  0.3 Mixed Human Diet IAEA H-9 378  30 384  20 380  20 US Diet-II 2B-017 368  24 372  22 375  22 Swedish Diet DBW-9a 324  20 322  116 320  12

Detection Limits of Iodine by Different Methods

Method ti : td : tc (min) Detection limit (ng) Preconcentration by extraction followed by Bi2S3 coprecipitation 30:1:30 60:1:60 5 3 Radiochemical separation using Bi2S3 coprecipitation 60:60:30 2 Preconcentration with Bi2S3 coprecipitation followed by radiochemical purification with PdI2 precipitation 30:20:30 60:20:60 1 0.5

Calculation of Expanded Uncertainty

A chemical measurement process consists of:

• 1. Sampling and sample preparation
• 2. Measurement of the test portion
• 3. Evaluation of the measurement
• 4. Report of the measurement results

in terms of an estimate of the analyte amount (measured) and its uncertainty. Uncertainty of measurement is defined as “a parameter associated with the results of a measurement, that characterizes the dispersion of the values that could reasonably be attributed to the measurand”.

Expanded Uncertainty

Category

• Rel. Std. Unc (%)
• 1. Pre-irradiation step

0.3077

• 2. Irradiation step

0.1143

• 3. Gamma-ray spectrometry step

3.3170

Overall Relative Std. Uncertainty (1s), % 3.3332 Relative Expanded Uncertainty (K=2), 95% 6.6664 Standard expanded uncertainty = 0.53 * 6.6664/100 = 0.04 ppm

Iodine concentration in milk: 0.53 ± 0.04 ppm

Conditions: ti=5 min, td=2 min, tc=10 min full reactor neutron flux and conventional counting

Detection limit: 0.11 ppm

Milk

H2O Carbohydrates (a-lactose) Lipids Proteins 87.9% Non-fat soluble

(28–38) mg mL-1

Minerals Anions of acids and gases

~ 0.95%

Iodine Species in Milk

38 mg mL-1 48 mg mL-1

Protein-bound Iodine

Lipid-bound Iodine Iodide Iodate Iodine T3 T4

Precipitation Solvent extraction Ion exchange chromatography

Total iodine concentration: 0.467 g mL-1

Simultaneous Analysis

Inorganic iodine: 0.405 ± 0.003 (86.7%) Organic Iodine : 0.049 ± 0.003 (10.5%) Total Protein : 0.034 ± 0.003 (7.3%) Total Lipids : 0.013 ± 0.003 (2.8%) Recovery : 96.8%

Sequential Analysis

Iodide : 0.337 ± 0.009 (72.2%) Iodate : 0.064 ± 0.003 (13.7%) Total Protein : 0.034 ± 0.003 (7.3%) Total Lipids : 0.011 ± 0.003 (2.3%) Recovery : 95.5%

Iodine Speciation in Milk

Proteins

Casein : 5.6% Whey Protein : 1.7%

Lipids

Neutral : 83.4% Glycolipids : 14.5% Phospholipids : 0.86%

Conclusions

 Ion exchange chromatography in conjunction with NAA is suitable for separating anionic iodine species.  About 87% of the total iodine in milk is present as iodide and iodate, of which 83.5% is iodide.  Simultaneous and sequential analysis methods developed here agree well. It can therefore be concluded that no chemical conversion of one iodine species to another is taking place during the separation.  Lipid-soluble iodine compounds represent 2.8% of the total iodine in milk. About 83% of this iodine is present in neutral lipids, 14% in glycolipids, 0.9% in phospholipids.  Protein-bound iodine represents 7.3% of the total iodine in milk. About 77% of which is associated with casein.

Ongoing Work

• Investigations on the presence of other

possible iodine species such as T3, T4, I2, and IO+

• Application of the expanded uncertainty

calculations to each species measured in this work

Estimation of Total and Bioaccessible Levels of Iodine in Edible Seaweeds of Japan by Epithermal Neutron Activation Analysis

Michiko Fukushima Department of Basic Sciences Ishinomaki Senshu University, Japan Amares Chatt SLOWPOKE-2 Facility Trace Analysis Research Centre Department of Chemistry Dalhousie University, Canada

Samples: red and green algae

• No. General name

Botanical name Treatment, Part analyzed Class 1 Glue plant Gloiopeltis raw, whole red 2 laver Porphyra raw, whole red 3 agar-agar Gelidium amansii extract, powder red 4 Sea lettuce Ulva raw, whole green No.1 No.4 No.2 sushi (baked) No.3

• No. General name

Botanical name Treatment, Part analyzed 5 hijiki Hizikia fusifome dried, whole 6 Japanese tangle Laminaria japonica dried after boiling,whole 7 sea mustard Undaria pinnatifida raw, leaves

Samples: brown algae (1)

sea mustard, No.7 Japanese tangle, No. 6 root hijiki, No.5 Miso soup with

Separation of bioaccesible iodine

• 1g of sample
• Incubate for 15 min at 95℃

with 0.10 mL of α-Amylase (pH 6.0)

• Filter the water soluble fiber and residue
• Add 95% ethanol
• Incubate for 30 min at 60℃ with 0.1 mL
• f 50 mg/mL Protease (pH 7.5±0.2)
• Incubate for 30 min at 60℃ with 0.1 mL
• f Amyloglucosidase (pH4.0-4.6)
• Wash with ethanol, acetone, freeze-dry, weigh
• EINAA

Total iodine and bioaccesible fraction in edible seaweeds of Japan

Edible seaweeds Processing Iodine Total conc. (mg/kg DW) Bioaccessible/ total (%) Glue plant raw 113 ± 1 1 laver raw 11 ± 6 Powder of extract from agar-agar ND Sea lettuce raw 57 ± 3 20 hijiki boiled 540 ± 10 74 Japanese tangle boiled 101 ± 2 54 Sea mustard boiled 156 ± 2 43 Sporophyl, boiled 70 ± 2 87 Fir needle raw 73 ± 2 baked 70 ± 2 100

Distribution of iodine in Japanese tangle

root

15 cm

Acknowledgments

Natural Sciences and Engineering Research Council of Canada Fisheries and Oceans Canada Health Canada Dalhousie University International Atomic Energy Agency

• Prof. Flavia GROPPI

INFN Milano, LASA

• Univ. Milano, Dipartimento di Fisica

Grazie Mille