EE Strydom Nutritional Intervention Research Unit Medical Research Council of South Africa

1. Inter-laboratory performance of analytical laboratories and process laboratories of the salt industry in determining the iodine content of iodated table salt EE Strydom Nutritional Intervention Research Unit Medical Research Council of South Africa

2. As investigators we wish to express our sincere gratitude towards the participating laboratories • Process laboratories of table salt producers (11) • Bergpan & Crystal Salt Works in Vivo • National Salt Ltd in Veldrif and Port Elizabeth • Swartskop Sea Salt in Port Elizabeth • Khoisan in Veldrif • Kalkpoort in Upington • Royal salt (Saltcor, Parow and Salpura, Upington) • Oranje Saltworks in Upington • Oranje River Salt works in Kimberley • Swan salt in Alrode • Analytical laboratories (4) • Pathcare Upington, Forensic DoH CPT • Microchem Laboratory Services CPT, Cameron CPT

3. Why is iodine an essential micronutrient Iodine is essential for the production of thyroid hormones which control cell metabolism, neuromuscular tissue growth and development, especially the fetal perinatal brain. Iodine deficiency (ID) is the world’s most prevalent cause of brain damage where serious iodine deficiency during pregnancy may result in stillbirths, abortions, stunting, goitre, mental impairment and cretinism. Constant insufficient dietary iodine results in hypothyroidism (elevated TSH and low FT4) and subsequently palpating or visible Goitre.

4. Salt Iodisation • Salt iodisation is the most effective vehicle and long-term strategy to ensure adequate iodine nutrition. • Compulsory iodation of table salt in South Africa • at 40-60 ppm iodine was introduced in 1995 • changed to 35-65 ppm in 2006 • Salt is fortified with potassium iodate in South Africa

5. Rationale National surveys shown that iodated salt at production level were not adequately iodised (40-60 ppm) • Table salt producers with poor quantitative monitoring of salt, lack of equipment, training and technical ability were largely responsible. • RSA is virtually iodine sufficient but pockets exist where inadequately iodated salt is used in households

6. Aim • A) To strengthen the capacity of salt producers to produce adequate iodated table salt by • providing a standardised titration method (manual) • Equipment • Chemicals (AR grade) • Skills necessary for reliable iodine monitoring of iodated salt on a routine basis. B) To evaluate the performance of laboratories analysing the iodine content of iodised salt through annual inter-laboratory comparisons

7. Assessment and Training • Assessed 12 salt producers for the possibility to determine iodine in salt at the production site • One laboratory was shared between two salt producers • 11 laboratories tested salt samples during assessment or training course

8. TRAINING COURSE • Two-day training courses • Consequences of inadequate iodine nutrition • National importance of accurate salt iodisation • Equipment use • Verification of instruments and balance • Reagent preparation and storage • Calculations and expression of results • Importance of controls • Accuracy, precision and % deviation • Contamination and Safety • Preventive maintenance

9. EQUIPMENT (provided to newly trained process laboratories) EQUIPMENT Self Zero Burettes Domestic hotplate and labware Schilling Bach Nalgene Acrylic Balance with SABS weights

10. Methodology Quality control exercise for inter-laboratory comparison Homogenously iodated salt pools of increasing concentrations ranging for 10-100ppm were prepared by the MRC and analysed in triplicate by the participating laboratories 5 salt pools in 2007 6 salt pools in 2008 8 salt pools in 2009 Results were compare to MRC iodine values. % deviation to determine accuracy and agreement % coefficient variation (CV) to determine repeatability

11. Analytical Methods of Choice • Manual titration method with Burette • 50g, 25g or 10g acidified salt sample titrated with 0.0125N, 0.01N or 0.005Nsodium thiosulfate in the presence of potassium iodide • WYD Iodine Checker • Colorimetric measurement of the blue iodine-starch complex at 570nm of a10g salt sample • Petentiometry • 25g or 10g salt samples titrated with 0.01N or 0.005N sodium thiosulfate, repectively • According to RSA legislation and worldwide , manual titration is the method of choice because of its accuracy, ease of operation and low cost.

12. EQUIPMENT (used by existing process and analytical laboratories WYD colorimeter Bottle Top Burettes Petentiometers (ISE)

13. Acceptable Allowance Criteria

14. Response

15. Precision of participating labs

16. Accuracy: Process Laboratories The % deviation from the target value

17. Accuracy: Analytical Laboratories (AL)The % deviation from the target value (Nov 2009)

18. Possible Interfering Substances (falsely elevated Iodine approx. 5ppm) Cold tap water 14-10-2010 Cold tap water 5-11-2010 Deionised water Chlorine 15ppm Chlorine 15ppm This 15ppm chlorine tested with the iodometric method could have elevated the iodine value approximately 15ppm Chlorine compounds in our water and disinfectants could interfere with reaction resulting in elevated results

19. Summary of Results Overall a statistical significant overestimation of accuracy was observed in 2007, 2008 and 2009 Overall 82%, 76% and 63% of iodine values deviated less than 15 % from target value, in 2007, 2008 and 2009 respectively In comparison to the process laboratories, the analytical laboratories underestimated the iodine concentration in 2009 (P=0.04) Consisting overestimation could lead to under –iodisation of salt and underestimation to over-iodisation

20. Findings • Decline in accurate measurements which could result in inadequate salt iodisation • Shortcomings of process laboratories in the salt industry • Managerial responsibilities and inadequate lab infrastructure • Lack of technical abilities and staff retention • Inferior lab instrumentation and inappropriate cleaning • Expired and contaminated chemicals and reagents • Insufficient acidifying and Interfering substances • Outcome of results and interaction with analytical laboratories • Need to standardize methods commonly used in RSA • Misunderstanding and interpretations of the AOAC methods • Lack of participation in inter-laboratory comparisons

21. Conclusion • In view of the effectiveness of the training, three of the newly trained salt producers significantly improved their laboratory infrastructure and management within one year • This project effectively standardised the titration method for iodated salt and trained analysts in the South African salt industry, but there is a need for long term compliance of process laboratories and analytical laboratories to ensure accurate iodation of salt.