Detection of Perfluorooctanoic acid concentration in human plasma Andrew SzeligaPerfluorooctanoic acid (PFOA) • PFOA is a perfluorinated carboxylic acid1 • The primary use of PFOA is as a processing aid in the production of fluoropolymers • pKa: 2.5 • Melting point: 55-56°C2 • Boiling Point: 189°C • Exact mass: 413.973700 Daltons • Not fluorescently activeHypothesis • People who work or live in close proximity to places that use PFOA will have elevated and potentially harmful levels of PFOA in their bloodstream if PFOA is leaking into their water supply • The level of PFOA in the bloodstream of this at-risk population should be compared against the national average • If the level of PFOA is significantly elevated, then there is evidence of improper disposalHow PFOA Enters the Human Body • PFOA is an industrial pollutant. Improper disposal leads to elevated levels in the water supply which causes it to accumulate in the bloodstream • PFOA can also leech out of fluoropolymers present in many household goods1 • Due to this exposure, PFOA exists at a 3.4 ng/mL concentration in the blood of the average American3Methods of Separation Method Advantages Disadvantages Reverse-Phase HPLC4 •Fast (14 min trial) •High Resolution •Widespread use in medical research •High use of solvent Gas Chromatography5 •High Resolution •Prepares sample for Mass Spec. •Requires derivatization with n-butanol •Slow (26 min trial) Capillary Zone Electrophoresis6 •Fast (14 min trial) •Low resolution •Requires several organic additivesMethods of Detection Method Advantages Disadvantages Suppressed Conductivity Detection4 •Can measure directly •Requires no derivatization •Simple •Low equipment cost •Must be modified to exclude teflon and other fluoropolymers from its construction •High limit of detection Mass Spectrometry5 •Extremely selective •Extremely sensitive •Requires GC • Expensive equipment required Fluorescence Detection 6 •Extremely selective •PFOA must be measured indirectly •High limit of detectionReverse-phase HPLC • HPLC System: Dionex ICS-3000, replacing the sample loop with a concentrator and ASI-100 autosampler4. • Column: Acdaim PA2 (3 mm 2.1 x 150 mm) • Concentrator: Acclaim PA2 (5 mm 4.3 x 10 mm guard cartridge and holder • Selected for lack of fluoropolymers in internal construction http://pioneer.netserv.chula.ac.th/~skitipat/hplc/hplcman.html Mobile Phase A • 17% 100 mM H3BO3 and 9 mM KOH, pH 8 • 83% DI water Mobile Phase B • 30% 70:30 (v:v) acetonitrile:water • 30% 100 mM H3BO3 and 9 mM KOH, pH 8 • 40% DI waterSuppressed Conductivity Detection • Conductivity Detector: ED50A Electrochemical Detector with conductivity cell and DS3 Detector Stabilizer4 • Suppressor: Dionex ASRS ULTRA II 2 mm, with external regenerant • Regenerant: 25 meq/L H2SO4 at approx 0.5 mL/min • Limit of Detection: 0.5 μg/mL http://www.chromatography-online.org/HPLC/Electrical-Conductivity/rs29.htmlProcedure • The PFOA in the original plasma sample is purified by precipitating the proteins in acetonitrile. The solvent extracts are then saved for analysis • The solvent extracts are spiked with a standard solution of PFOA • The solvent extracts are concentrated on a column before being injected into the separation column • The fractions move through a suppression filter before entering the conductivity detectorThe future of PFOA detection • While no robust procedure has been developed, better electrochemical methods for the detection of PFOA are possible • Ion selective electrodes have been used to quantify the concentration of perfluorooctanoate in solution7 • In a basic environment, PFOA may be quantifiable with an ion-selective electrode with minimal sample preparationConclusion • HPLC/Suppressed Conductivity Detection is the most cost effective method for large scale analysis of PFOA concentration in blood samples • The results can be compared to the national average to look for evidence of localized PFOA contamination • Future methods may be more portable or more cost effectiveReferences 1. Substance flow analysis for Switzerland: Perfluorinated surfactants perfluorooctanesulfonate (PFOS) and perfluorooctanoic acid (PFOA); Federal Office for the Environment (FOEN) : Bern 2009 2. Sigma-Aldrich Catalog, Perfluorooctanoic Acid. http://www.sigmaaldrich.com/catalog/ProductDetail.do?lang=en&N4=171468|ALDRICH&N5=SEARCH_CONCAT_PNO|BRAND_KEY&F=SPEC 3. Olsen, G. Decline in Perfluorooctanesulfonate and Other Polyfluoroalkyl Chemicals in American Red Cross Adult Blood Donors, 2000−2006. Environ. Sci. Technol., 2008, 42 (13), pp 4989-4995 4. de Borba B., Rohrer J. "Analysis of PFOA and PFOS in Water Using Reversed-Phase HPLC with Suppressed Conductivity Detection." LC-GC Europe. March 2007;20:10 5. Liu, Wen-Lin, and W. Liu. "Headspace solid phase microextraction in-situ supercritical fluid extraction coupled to gas chromatography-tandem mass spectrometry for simultaneous determination of perfluorocarboxylic acids in sediments." Journal of chromatography 1218.43 (2011):7857. 6. Wójcik, L., Szostek, B., "Separation of perfluorocarboxylic acids using capillary electrophoresis with UV detection" Electrophoresis 2005, 26, 1080-1088 7. The Influence of Sodium Perfluorooctanoate on the Conformational Transitions of Human Immunoglobulin Paula V. Messina,†,#Gerardo Prieto,†Francisco Salgado,§, Carla Varela,§, Montserrat Nogueira,§, Verónica Dodero,‡Juan M. Ruso,† and, and Félix Sarmiento*,† The Journal of Physical Chemistry B 2007 111 (28),
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