Determination of Total Halogen Content in Halogen-Free Fluxes
It is important for laboratories to follow robust methods to assure commercial products meet the safety requirements established.
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Authored By:
Christopher J. Pontius, George Kraeger, Ron Lasky, Ph.D., P.E.
Indium Corporation
Clinton, NY, US
Summary
Brominated flame retardants (BFRs) are coming under heavy scrutiny due to increasing evidence of the risks they pose to the environment and human health. Therefore, it is important for industrial quality laboratories to follow robust methods to assure commercial products meet the safety requirements established by the governing bodies of the world. Currently, the most common method to determine halogen content is oxygen combustion, followed by ion chromatography. The oxygen combustion test is widely established in environmental as well as in industrial laboratories.
One current accepted test method, EN14582, may under-report bromine and chlorine content by as much as 65%. The use of inductively coupled plasma (ICP) methods of detection appears to resolve this discrepancy. Flux marketed as "zero intentionally-added halogens" was combusted in a bomb calorimeter vessel under 30atm of high-purity oxygen in the presence of 25ml of water. The resultant solution was analyzed using both ion chromatography (IC) and ICP. The flux was found to contain <10ppm of each element using both techniques.
Samples were then spiked using a common flux additive containing chlorine and bromine, combusted in the same manner, and analyzed. At a low concentration (15ppm Br, 6ppm Cl), the average %recovery of Br was 60.7% by IC and 100.8% by ICP; the %recovery of Cl was 109.5% by IC and 84.8% by ICP. At a moderate concentration (150ppm Br, 65ppm Cl), the %recovery of Br was 25.5% by IC and 86.9% by ICP; the %recovery of Cl was 81.8% by IC and 104.2% by ICP.
The effect of pH and buffering capacity of the absorbing solution was explored by ICP in an attempt to optimize the sequestration of Cl and Br in the solution as stable oxyanions; however, the results of hypothetically optimal solutions were no more accurate than those using analytical water as the absorbing solution. Additionally, thirty samples of flux containing 275ppm intentionally-added organic bromine were combusted and analyzed using the techniques described. The average %recovery of bromine by IC was 64.3% and 105.1% by ICP.
Conclusions
It appears from these results that ICP detection of bromine and chlorine may be favorable to IC detection at concentrations less than 300ppm and potentially at all concentrations. Experimental results demonstrate a reduction in error of about 75% at the concentrations tested, from 35-40% to 5-10%.
It is possible that KOH absorption solutions could be analyzed by Anion-IC following treatment with cation exchange filters; this may be evaluated during future work. The use of sodium carbonate/bicarbonate solutions for absorption was not explored but may be useable on newer IC systems which remove carbonate from the eluent post-separation pre-detection. In past experiences, high concentrations of carbonate in sample solutions interfered with bromide determination. This artifact may not be as much of an issue when quantifying bromine at higher concentrations.
Initially Published in the SMTA Proceedings
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