{"id":43338,"date":"2020-10-26T00:00:00","date_gmt":"2020-10-26T00:00:00","guid":{"rendered":"https:\/\/discover.restek.com\/uncategorized\/a-rapid-and-sensitive-lc-msms-method-for-the-analysis-of-three-forms-of-thyroid-hormones-using-raptor-biphenyl-lc-columns\/"},"modified":"2025-12-10T19:33:01","modified_gmt":"2025-12-10T19:33:01","slug":"a-rapid-and-sensitive-lc-msms-method-for-the-analysis-of-three-forms-of-thyroid-hormones-using-raptor-biphenyl-lc-columns","status":"publish","type":"post","link":"https:\/\/discover.restek.com\/zh-hans\/application-notes\/baan2112\/a-rapid-and-sensitive-lc-msms-method-for-the-analysis-of-three-forms-of-thyroid-hormones-using-raptor-biphenyl-lc-columns","title":{"rendered":"A Rapid and Sensitive LC-MS\/MS Method for the Analysis of Three Forms of Thyroid Hormones Using Raptor Biphenyl LC Columns"},"content":{"rendered":"\n<p>Thyroid hormones are essential for the regulation of development and growth in humans and animals. The thyroid gland produces thyroxin (T4) and tri-iodothyronine (T3) and quickly releases these compounds into the circulatory system. The concentration of circulating T4 is 50-60 times higher than T3 and the majority of these molecules are bound to blood proteins. The unbound or \u201cfree\u201d T3 and T4 are the active forms of the hormone which only represent a small portion (less than 1%) of total thyroid hormones. Accurate and sensitive measurement of low pg\/mL levels of free hormones is necessary to assess thyroid function for both veterinary and human diagnostics. Reverse tri-iodothyronine (rT3) is an inactive form that results from T4 biotransformation. Since rT3 functions as the feedback inhibitor of thyroid hormone production, the measurement of rT3 can be an important diagnostic marker with clinical implications.<\/p>\n\n\n\n<p>The intent of this application was to develop an LC-MS\/MS method for the analysis of thyroid hormones at the free form levels using the highly efficient and selective Raptor Biphenyl LC column. The clinical applicability of this method was demonstrated by analyzing fortified thyroid hormone in phosphate buffered saline (PBS) containing 4% human albumin.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Experimental<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">Instrument and Analytical Conditions<\/h3>\n\n\n\n<p>The instrument and analytical conditions are listed in Table I. The analyte MRMs are shown in Table II.<\/p>\n\n\n\n<p><strong>Table I:<\/strong>&nbsp;&nbsp;Analytical Conditions for Waters Xevo TQ-S with Acquity UPLC<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td><strong>Analytical Column<\/strong><\/td><td colspan=\"2\">Raptor Biphenyl 2.7 \u00b5m, 100 mm x 2.1 mm (cat.# 9309A12)<\/td><\/tr><tr><td><strong>Guard Column<\/strong><\/td><td colspan=\"2\">Raptor Biphenyl EXP guard column cartridge 2.7 \u00b5m, 5 mm x 2.1 mm (cat.# 9309A0252)<\/td><\/tr><tr><td><strong>Mobile Phase A<\/strong><\/td><td colspan=\"2\">0.1% Formic acid in water<\/td><\/tr><tr><td><strong>Mobile phase B<\/strong><\/td><td colspan=\"2\">0.1% Formic acid in methanol<\/td><\/tr><tr><td rowspan=\"5\"><strong>Gradient<\/strong><\/td><td><strong>Time (min)<\/strong><\/td><td><strong>%B<\/strong><\/td><\/tr><tr><td>0.0<\/td><td>70<\/td><\/tr><tr><td>2.0<\/td><td>80<\/td><\/tr><tr><td>2.01<\/td><td>70<\/td><\/tr><tr><td>3.5<\/td><td>70<\/td><\/tr><tr><td><strong>Flow Rate<\/strong><\/td><td colspan=\"2\">0.4 mL\/min<\/td><\/tr><tr><td><strong>Column Temp.<\/strong><\/td><td colspan=\"2\">40 \u00b0C<\/td><\/tr><tr><td><strong>Ion Mode<\/strong><\/td><td colspan=\"2\">Positive ESI<\/td><\/tr><tr><td><strong>Capillary Voltage<\/strong><\/td><td colspan=\"2\">2.0 kV<\/td><\/tr><tr><td rowspan=\"3\"><strong>Gas Flow<\/strong><\/td><td colspan=\"2\">800 (L\/Hr) desolvation<\/td><\/tr><tr><td colspan=\"2\">200 (L\/Hr) cone<\/td><\/tr><tr><td colspan=\"2\">7.0 (bar) nebulizer<\/td><\/tr><tr><td><strong>Desolvation Temp.<\/strong><\/td><td colspan=\"2\">600 \u00b0C<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p><strong>Table II:<\/strong>&nbsp;&nbsp;Analyte MS\/MS Transitions<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th><strong>Analyte<\/strong><\/th><th><strong>Precursor Ion<\/strong><\/th><th><strong>Product Ion Quantifier<\/strong><\/th><th><strong>Product Ion Qualifier<\/strong><\/th><\/tr><\/thead><tbody><tr><td>T3<\/td><td>652.07<\/td><td>606.10<\/td><td>508.10<\/td><\/tr><tr><td>rT3<\/td><td>652.07<\/td><td>606.10<\/td><td>508.10<\/td><\/tr><tr><td>T4<\/td><td>778.03<\/td><td>731.97<\/td><td>323.87<\/td><\/tr><tr><td>T4-<sup>13<\/sup>C<sub>6<\/sub><\/td><td>784.09<\/td><td>738.04<\/td><td>&#8211;<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h3 class=\"wp-block-heading\">Sample\/Calibration Standard Preparation<\/h3>\n\n\n\n<p>Human albumin was dissolved in PBS solution to a final concentration of 4%. This solution was used to prepare calibration standards ranging from 2 to 400 pg\/mL. Standard solutions (0.5 mL) were fortified with 5 \u00b5L of internal standard (T4-<sup>13<\/sup>C<sub>6<\/sub>&nbsp;[1 ng\/mL]) and mixed with 1 mL of acetonitrile in a 4 mL glass vial. A 2 mL aliquot of ethyl acetate was added, stirred for 2 min, and then centrifuged for 10 min at 4,300 rpm. The organic phase was removed and placed into a 4 mL glass vial, then evaporated to dryness at 55 \u00b0C under a gentle stream of nitrogen. The dried extract was reconstituted with 80 \u00b5L of a 30:70 water:methanol solution and injected (10 \u00b5L) into the LC-MS\/MS for analysis.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Results<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">Chromatographic Separation of Thyroid Hormones<\/h3>\n\n\n\n<p>Since the most sensitive mass transitions for T3 and rT3 are identical, it is necessary to chromatographically separate these two compounds for accurate quantitation. With independent injections of T3 and rT3, it was shown that T3 and rT3 were completely resolved with the Raptor Biphenyl column (Figure 1). An example chromatogram (Figure 2) shows the baseline resolution of 3 forms of thyroid hormone from extracted sample (20 pg\/mL) within 2 minutes.<\/p>\n\n\n<div class=\"wp-block-custom-chromatogram-article-top\"><div class=\"chromatogram-article-placeholder\"><div class=\"figure-heading\"><strong>Figure 1:<\/strong>\u00a0Chromatographic separation of T3 and rT3 on the Raptor Biphenyl column. Note: peak separation is critical for accurate analysis because these compounds have identical transitions and cannot be distinguished by MS\/MS alone.<\/div><div class='chromatogram-article-inner-full'><div class=\"chromatogram-article-inner\">\n<div class=\"wp-block-custom-chromatogram-article\"><div class=\"wp-block-custom-chromatogram-article\"><div class=\"chromatogram-image regular-image\"><img decoding=\"async\" src=\"https:\/\/ez.restek.com\/images\/cgram\/lc_cf0603.png\" alt=\"T3 and rT3 Analysis on Raptor\u2122 Biphenyl by LC-MS\/MS\" title=\"-\"><\/div><p class=\"article-id\" style=\"text-align:center\"> LC_CF0603<\/p><div class=\"chromatogram-peaks\"><h4>Peaks<\/h4><table class=\"peaks col-lg-6 col-12\">\n<thead><tr><th><\/th><th style=\"text-align: left;width: 75px\">Peaks<\/th><th style=\"text-align: center;width: 75px\">t<sub>R<\/sub> (min)<\/th><th style=\"text-align: center;width: 75px\">Precursor Ion<\/th><th style=\"text-align: center;width: 75px\">Quantifier Ion<\/th><th style=\"text-align: center;width: 75px\">Qualifier Ion<\/th><\/tr><\/thead>\n<tbody><tr><td class=\"num\">1.<\/td><td class=\"cmpd\">Tri-iodothyronine (T3)<\/td><td class=\"oth\">1.03<\/td><td class=\"oth\">652.07<\/td><td class=\"oth\">606.10<\/td><td class=\"oth\">508.10<\/td><\/tr>\n<tr><td class=\"num\">2.<\/td><td class=\"cmpd\">Reverse tri-iodothyronine (rT3)<\/td><td class=\"oth\">1.24<\/td><td class=\"oth\">652.07<\/td><td class=\"oth\">606.10<\/td><td class=\"oth\">508.10<\/td><\/tr>\n<\/tbody><\/table><\/div><div class=\"chromatogram-pdf-link\"><a href=\"https:\/\/ez.restek.com\/images\/cgram\/lc_cf0603.pdf\" target=\"_blank\" rel=\"noopener noreferrer\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewBox=\"0 0 18 18\"><g data-name=\"Group 2996\"><path data-name=\"Rectangle 1246\" d=\"M0 0h18v18H0z\" style=\"fill: none;\"><\/path><\/g><g data-name=\"Group 2997\"><path data-name=\"Path 729\" d=\"M13.412 11.4v2.017H5.345V11.4H4v2.017a1.349 1.349 0 0 0 1.345 1.345h8.068a1.349 1.349 0 0 0 1.345-1.345V11.4zm-.672-2.694-.948-.948-1.741 1.735V4H8.706v5.493L6.965 7.758l-.948.948 3.361 3.361z\" transform=\"translate(-.437 -.414)\" style=\"fill: rgb(13, 123, 196);\"><\/path><\/g><\/svg>Download PDF<\/a><\/div><\/div><\/div>\n<\/div><\/div><\/div>\n\n<div class=\"wp-block-custom-chromatogram-article-top\"><div class=\"chromatogram-article-placeholder\"><div class=\"figure-heading\"><strong>Figure 2:<\/strong>\u00a0Complete chromatographic separations of all three extracted thyroid hormones (20 pg\/mL) are obtained in less than 2 minutes.<\/div><div class='chromatogram-article-inner-full'><div class=\"chromatogram-article-inner\">\n<div class=\"wp-block-custom-chromatogram-article\"><div class=\"wp-block-custom-chromatogram-article\"><div class=\"chromatogram-image regular-image\"><img decoding=\"async\" src=\"https:\/\/ez.restek.com\/images\/cgram\/lc_cf0605.png\" alt=\"Thyroid Hormone Analysis in 4% Human Albumin in PBS on Raptor Biphenyl by LC-MS\/MS\" title=\"-\"><\/div><p class=\"article-id\" style=\"text-align:center\"> LC_CF0605<\/p><div class=\"chromatogram-peaks\"><h4>Peaks<\/h4><table class=\"peaks col-lg-6 col-12\">\n<thead><tr><th><\/th><th style=\"text-align: left;width: 75px\">Peaks<\/th><th style=\"text-align: center;width: 75px\">t<sub>R<\/sub> (min)<\/th><th style=\"text-align: center;width: 75px\">Precursor Ion<\/th><th style=\"text-align: center;width: 75px\">Product Ion<\/th><\/tr><\/thead>\n<tbody><tr><td class=\"num\">1.<\/td><td class=\"cmpd\">Tri-iodothyronine (T3)<\/td><td class=\"oth\">1.04<\/td><td class=\"oth\">652.07<\/td><td class=\"oth\">606.10<\/td><\/tr>\n<tr><td class=\"num\">2.<\/td><td class=\"cmpd\">Reverse tri-iodothyronine (rT3)<\/td><td class=\"oth\">1.25<\/td><td class=\"oth\">652.07<\/td><td class=\"oth\">606.10<\/td><\/tr>\n<tr><td class=\"num\">3.<\/td><td class=\"cmpd\">Thyroxin (T4)<\/td><td class=\"oth\">1.43<\/td><td class=\"oth\">778.03<\/td><td class=\"oth\">731.97<\/td><\/tr>\n<tr><td class=\"num\">4.<\/td><td class=\"cmpd\">Thyroxin-13C6<\/td><td class=\"oth\">1.43<\/td><td class=\"oth\">784.09<\/td><td class=\"oth\">738.04<\/td><\/tr>\n<\/tbody><\/table><\/div><div class=\"chromatogram-conditions\"><h4>Conditions<\/h4><div class=\"conditions-container container-fluid\"><div class=\"row\"><table class=\"conditions col-lg-6 col-12\"><tr><th class=\"conditions_header\" scope=\"row\">Column<\/th><td>Raptor Biphenyl  (<a target=\"_blank\" href=\"https:\/\/www.restek.com\/p\/9309A12?utm_source=chromatograms&amp;utm_medium=link&amp;utm_campaign=LC_CF0605\" rel=\"noopener\">cat.# 9309A12<\/a>)<\/td><\/tr><tr><th class=\"sub conditions_header\" scope=\"row\">Dimensions:<\/th><td>100 mm x 2.1 mm ID<\/td><\/tr><tr><th class=\"sub conditions_header\" scope=\"row\">Particle Size:<\/th><td>2.7 \u00b5m<\/td><\/tr><tr><th class=\"sub conditions_header\" scope=\"row\">Pore Size:<\/th><td>90 \u00c5<\/td><\/tr><tr><td><\/td><tr><th class=\"sub conditions_header\" scope=\"row\">Guard Column:<\/th><td>Raptor Biphenyl EXP guard column cartridge 5 mm, 2.1 mm ID, 2.7 \u00b5m (<a target=\"_blank\" href=\"https:\/\/www.restek.com\/p\/9309A0252?utm_source=chromatograms&amp;utm_medium=link&amp;utm_campaign=LC_CF0605\" rel=\"noopener\">cat.# 9309A0252<\/a>)<\/td><\/tr><tr><th class=\"sub conditions_header\" scope=\"row\">Temp.:<\/th><td>40 \u00b0C<\/td><\/tr><tr class=\"cgram_header_row\"><th class=\"conditions_header\" scope=\"row\">Standard\/Sample<\/th><td><\/td><\/tr><tr><th class=\"sub conditions_header\" scope=\"row\">Diluent:<\/th><td>30:70 Water:methanol<\/td><\/tr><tr><th class=\"sub conditions_header\" scope=\"row\">Conc.:<\/th><td>20  pg\/mL<\/td><\/tr><td><\/td><\/tr><tr><th class=\"sub conditions_header\" scope=\"row\">Inj. Vol.:<\/th><td>10 \u00b5L <\/td><\/tr><tr class=\"cgram_header_row\"><th class=\"conditions_header\" scope=\"row\">Mobile Phase<\/th><td><\/td><\/tr><tr><th class=\"sub conditions_header\" scope=\"row\">A:<\/th><td>0.1% Formic acid in water <\/td><\/tr><tr><th class=\"sub conditions_header\" scope=\"row\">B:<\/th><td>0.1% Formic acid in methanol <\/td><\/tr><tr><td><\/td><td><table class=\"cgram_ramp\"><thead><tr><th>Time (min)<\/th><th>Flow (mL\/min)<\/th><th>%A<\/th><th>%B<\/th><\/tr><\/thead><tbody><tr><td>0.00<\/td><td>0.4<\/td><td>30<\/td><td>70<\/td><\/tr><tr><td>2.00<\/td><td>0.4<\/td><td>20<\/td><td>80<\/td><\/tr><tr><td>2.01<\/td><td>0.4<\/td><td>30<\/td><td>70<\/td><\/tr><tr><td>3.50<\/td><td>0.4<\/td><td>30<\/td><td>70<\/td><\/tr><\/tbody><\/table><\/td><\/tr><\/table><table class=\"conditions col-lg-6 col-12\"><tr><th class=\"conditions_header\" scope=\"row\">Detector<\/th><td>MS\/MS<\/td><\/tr><tr><th class=\"sub conditions_header\" scope=\"row\">Ion Mode:<\/th><td>ESI+ <\/td><\/tr><tr><th class=\"sub conditions_header\" scope=\"row\">Mode:<\/th><td>MRM <\/td><\/tr><tr class=\"cgram_header_row\"><th class=\"conditions_header\" scope=\"row\">Instrument<\/th><td>HPLC<\/td><\/tr><\/table><\/div><\/div><\/div><div class=\"chromatogram-pdf-link\"><a href=\"https:\/\/ez.restek.com\/images\/cgram\/lc_cf0605.pdf\" target=\"_blank\" rel=\"noopener noreferrer\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewBox=\"0 0 18 18\"><g data-name=\"Group 2996\"><path data-name=\"Rectangle 1246\" d=\"M0 0h18v18H0z\" style=\"fill: none;\"><\/path><\/g><g data-name=\"Group 2997\"><path data-name=\"Path 729\" d=\"M13.412 11.4v2.017H5.345V11.4H4v2.017a1.349 1.349 0 0 0 1.345 1.345h8.068a1.349 1.349 0 0 0 1.345-1.345V11.4zm-.672-2.694-.948-.948-1.741 1.735V4H8.706v5.493L6.965 7.758l-.948.948 3.361 3.361z\" transform=\"translate(-.437 -.414)\" style=\"fill: rgb(13, 123, 196);\"><\/path><\/g><\/svg>Download PDF<\/a><\/div><\/div><\/div>\n<\/div><\/div><\/div>\n\n\n<div style=\"height:50px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<h3 class=\"wp-block-heading\">Linearity<\/h3>\n\n\n\n<p>Good linearities (1\/x weighted) were obtained for all 3 forms of thyroid hormones with coefficient of determination (R<sup>2<\/sup>) values &gt; 0.990 from 2 to 400 pg\/mL (for T3) or 5 to 400 pg\/mL (for T4 and rT3). The %deviation was &lt; 15%. Linearity plots are shown in Figure 3.<\/p>\n\n\n<div class=\"wp-block-custom-chromatogram-article-top\"><div class=\"chromatogram-article-placeholder\"><div class=\"figure-heading\"><strong>Figure 3:<\/strong>\u00a0Good linear responses were obtained for thyroid hormones T4, T3, and rT3 at low pg\/mL levels.<\/div><div class='chromatogram-article-inner-full'><div class=\"chromatogram-article-inner\">\n\n<p><strong>A) T4 Calibration Curve, R<sup>2<\/sup>&nbsp;= 0.999<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"469\" src=\"https:\/\/discover.restek.com\/wp-content\/uploads\/figure-article-BAAN2112-01-1024x469.jpg\" alt=\"\" class=\"wp-image-18814\" style=\"object-fit:cover\" title=\"-\" srcset=\"https:\/\/discover.restek.com\/wp-content\/uploads\/figure-article-BAAN2112-01-1024x469.jpg 1024w, https:\/\/discover.restek.com\/wp-content\/uploads\/figure-article-BAAN2112-01-300x137.jpg 300w, https:\/\/discover.restek.com\/wp-content\/uploads\/figure-article-BAAN2112-01-768x352.jpg 768w, https:\/\/discover.restek.com\/wp-content\/uploads\/figure-article-BAAN2112-01-1536x703.jpg 1536w, https:\/\/discover.restek.com\/wp-content\/uploads\/figure-article-BAAN2112-01.jpg 1800w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n\n\n<p><strong><strong>B) T3 Calibration Curve, R<sup>2<\/sup>&nbsp;= 0.998<\/strong><\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"471\" src=\"https:\/\/discover.restek.com\/wp-content\/uploads\/figure-article-BAAN2112-02-1024x471.jpg\" alt=\"\" class=\"wp-image-18820\" style=\"object-fit:cover\" title=\"-\" srcset=\"https:\/\/discover.restek.com\/wp-content\/uploads\/figure-article-BAAN2112-02-1024x471.jpg 1024w, https:\/\/discover.restek.com\/wp-content\/uploads\/figure-article-BAAN2112-02-300x138.jpg 300w, https:\/\/discover.restek.com\/wp-content\/uploads\/figure-article-BAAN2112-02-768x353.jpg 768w, https:\/\/discover.restek.com\/wp-content\/uploads\/figure-article-BAAN2112-02-1536x707.jpg 1536w, https:\/\/discover.restek.com\/wp-content\/uploads\/figure-article-BAAN2112-02.jpg 1800w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n\n\n<p><strong><strong><strong>C) rT3 Calibration Curve, R<sup>2<\/sup>&nbsp;= 0.991<\/strong><\/strong><\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"473\" src=\"https:\/\/discover.restek.com\/wp-content\/uploads\/figure-article-BAAN2112-03-1024x473.jpg\" alt=\"\" class=\"wp-image-18826\" style=\"object-fit:cover\" title=\"-\" srcset=\"https:\/\/discover.restek.com\/wp-content\/uploads\/figure-article-BAAN2112-03-1024x473.jpg 1024w, https:\/\/discover.restek.com\/wp-content\/uploads\/figure-article-BAAN2112-03-300x139.jpg 300w, https:\/\/discover.restek.com\/wp-content\/uploads\/figure-article-BAAN2112-03-768x355.jpg 768w, https:\/\/discover.restek.com\/wp-content\/uploads\/figure-article-BAAN2112-03-1536x710.jpg 1536w, https:\/\/discover.restek.com\/wp-content\/uploads\/figure-article-BAAN2112-03.jpg 1800w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n<\/div><\/div><\/div>\n\n\n<div style=\"height:50px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<h2 class=\"wp-block-heading\">Conclusions<\/h2>\n\n\n\n<p>The Raptor Biphenyl column is excellent for rapid and sensitive analysis of thyroid hormones. With the method described here, concentrations of thyroid hormones as low as 2 pg\/mL (T3) or 5 pg\/mL (T4 and rT3) can be determined with less than 3.5 minutes of total analysis time. The analytical method is thus applicable to the clinical analysis of free thyroid hormone at low pg\/mL levels.<\/p>\n\n\n\n<div style=\"height:30px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n        <div class=\"cpb\">\n            <h3 class=\"cpb-heading\">Products Mentioned<\/h3>\n            <hr class=\"cpb-heading-underline\" \/>\n            <div class=\"cpb-list\">\n                                    <div class=\"cpb-item\">\n                        <div class=\"cpb-col cpb-col--left\">\n                            <a class=\"cpb-catalog\" target=\"_blank\" rel=\"noopener noreferrer\" href=\"https:\/\/www.restek.com\/p\/9309A12\">                                Catalog No. 9309A12                            <\/a>                        <\/div>\n                        <div class=\"cpb-col cpb-col--middle\">\n                            <div class=\"cpb-title\">Raptor Biphenyl, 2.7 \u00b5m, 100 x 2.1 mm HPLC Column<\/div>\n                        <\/div>\n                        <div class=\"cpb-col cpb-col--right\">\n                                                            <a class=\"cpb-view-btn\" target=\"_blank\" rel=\"noopener noreferrer\" href=\"https:\/\/www.restek.com\/p\/9309A12\">\u67e5\u770b\u4ea7\u54c1<\/a>\n                                                    <\/div>\n                    <\/div>\n                                    <div class=\"cpb-item\">\n                        <div class=\"cpb-col cpb-col--left\">\n                            <a class=\"cpb-catalog\" target=\"_blank\" rel=\"noopener noreferrer\" href=\"https:\/\/www.restek.com\/p\/9309A0252\">                                Catalog No. 9309A0252                            <\/a>                        <\/div>\n                        <div class=\"cpb-col cpb-col--middle\">\n                            <div class=\"cpb-title\">Raptor Biphenyl EXP Guard Column Cartridge, 2.7 \u00b5m, 5 x 2.1 mm, 3-pk.<\/div>\n                        <\/div>\n                        <div class=\"cpb-col cpb-col--right\">\n                                                            <a class=\"cpb-view-btn\" target=\"_blank\" rel=\"noopener noreferrer\" href=\"https:\/\/www.restek.com\/p\/9309A0252\">\u67e5\u770b\u4ea7\u54c1<\/a>\n                                                    <\/div>\n                    <\/div>\n                            <\/div>\n        <\/div>\n        \n\n\n<div style=\"height:100px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n","protected":false},"excerpt":{"rendered":"<p>The Raptor Biphenyl column is excellent for rapid and sensitive analysis of thyroid hormones. With the method described here, concentrations of thyroid hormones as low as 2 pg\/mL (T3) or 5 pg\/mL (T4 and rT3) can be determined with less than 3.5 minutes of total analysis time. The analytical method is thus applicable to the clinical analysis of free thyroid hormone at low pg\/mL 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