Iodine Testing
Midwest Microlab is capable of testing solid or liquid samples for total percentage of Iodine with a range of 0.04% (4,000 ppm) to 100%. Accuracy for Iodine testing is +/- 0.4. Please refer below for a brief description of the Iodine analysis procedure including interferences and sample size. Air Sensitive/Glove Box handling is NOT available for Iodine analysis.
Halogen Testing
Bromine Testing
Chlorine Testing
Fluorine Testing
Iodine Testing
Finding Total Percentage of Iodine
Iodine Analysis & Techniques
Midwest Microlab performs Iodine analysis using the Schoniger Combustion Technique.
The solid sample is weighed into ashless paper and inserted into a custom made Platinum stopper. The stopper is fitted with a flask that is charged with the appropriate absorbents and oxygen. On combustion the element present is trapped in several forms…free Iodine and Iodate.
The gasses are absorbed on the liquids. The resulting liquid is treated with various reactants to convert all remaining Iodine to the form of Iodate. The resulting liquid is then titrated with a standardized solution of Sodium Thiosulfate.
A standard starch titration yields a color change of black to clear at the endpoint. Other halogens do not seem to interfere in the determination. Selenium does seem to show some interference.
The most common standard for this determination is Potassium Bi-Iodate and Para-Iodo-Benzoic Acid from the NIST. There are others that may be used on occasion.
Due to the exclusive use of the flask combustion in the Iodine determination, we are not able to determine Iodine on air-sensitive samples.
Interferences Associated with Iodine Analysis:
Known Interference’s for Iodine Analysis include: Cl, Cu, Hg, and Se.
Please note the interferences above cannot be circumvented during analysis. Irregular results can be reported due to an interference within the molecular formula of the sample. Please note irregular results due to interferences cannot be interpreted by the chemists. Midwest Microlab chemists will perform requested analysis and report results as found with the understanding that the submitter understood the interferences associated and how it may affect results. Please indicate all elements or the molecular formula on the submission form
Suggested Sample Size according to Total Percentage Theory:
Theory % Iodine Single Iodine Duplicate Iodine Triplicate
0-5 % 15 mg 30 mg 45 mg
5-20% 10 mg 20 mg 30 mg
Above 20% 5 mg 10 mg 15 mg
Turnaround Time
Iodine is a complex and labor intensive determination. Standard Turnaround time for the total percentage of Iodine results is within 5 business days. RUSH services are available for an additional fee per sample, per analysis with per single run. Rush results turnaround time for Fluorine analysis is within 3-4 business days.
Midwest Microlab does NOT handle any samples containing Osmium, Uranium, or Thallium within the molecular formula.Midwest Microlab is able to perform samples with Depleted Uranium but must be clearly indicated on the submission form. Please indicate on the comments section of the submission form if samples have a high toxicity or strong stench. We do not handle any Finished Pharmaceuticals for release or highly volatile liquid samples with boiling points of less than 40 deg C.
Iodine Analysis & Techniques: What is Iodine?
Atomic weight 126.90, Atomic Number 53, Melting Point 113.70 C, Boiling Point 184.30 C.
Iodine (from the Greek word Iodes, meaning “violet”), is a chemical element in the periodic table that has the symbol I and atomic number 53. Chemically, this element is the least reactive of the halogens, and the most electropositive halogen after astatine. It is primarily used in medicine, photography and dyes. It is required in trace amounts by most living organisms.
As with all other halogens (members of Group VII in the Periodic Table), iodine forms diatomic molecules, and hence, has the molecular formula of I2.
The halogen is a dark-gray/purple-black solid that sublimates at standard temperatures into a purple-pink gas that has an irritating odor. This halogen forms compounds with many elements, but is less active than the other members of its Group VII (halogens) and has some metallic-like properties.
The element dissolves easily in chloroform, carbon tetrachloride, or carbon disulphide to form purple solutions (It is only slightly soluble in water, giving a yellow solution). The deep blue color of starch-iodine complexes is produced only by the free element.
Many students who have seen the classroom demonstration where crystals are gently heated in a test tube come away with the impression that liquid iodine cannot exist at atmospheric pressure. This misconception arises because sublimation occurs without the intermediacy of liquid.
The truth is that if iodine crystals are heated carefully to their melting point of 113.7 °C, the crystals will fuse into a liquid, which will be present under a dense blanket of the vapor.
Relevant sites:
Chemistry and the Aquarium
These results are indicative of total iodine (iodide + iodate + organic iodine) … Dissolved organic iodine in marine waters: Determination, occurrence and…
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