• high performance

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  detection limit 6.5 nmol/L (5 ng/mL)

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  within-assay CV less than 15% between 10-380 nmol/L (8 - 300 ng/mL)

• low cost

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  all reagents are provided - only test tubes and water are required

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  uses inexpensive, robust equipment

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  each kit is sufficient for 100 assay tubes

• convenient

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  direct serum assay

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  magnetic separation

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  shelf life of 9 months at 4-8°C

For information and prices please contact us.

The assay is a direct competitive EIA for the quantitative measurement of Total Thyroxine (Total T4) in human serum or plasma. A specific agent displaces T4 from binding proteins, making it available for antibody binding. T4 then equilibrates with fluorescein labelled T4 (T4 Derivative) in binding to a limited amount of alkaline phosphatase labelled anti-T4 antibody. An anti-fluorescein antibody bound to magnetic particles then separates the T4/fluorescein T4-antibody complex from unbound components. A further incubation with substrate produces colour in inverse proportion to the amount of T4 present. The assay has four main stages:

• Displacing agent, alkaline phosphatase labelled anti-T4 antibody, and fluorescein-T4 derivative are incubated with sample (50 µL) for 15 minutes at 37°C.
• Anti-fluorescein antibody coupled to magnetic particles is added and incubated for 10 minutes at 37°C. Anti-T4 antibody is then isolated by means of a magnetic wash step.
• A coloured enzyme substrate is incubated with the particles for 15 minutes at 37°C. The presence of alkaline phosphatase causes a colour change from yellow to pink. The reaction is terminated by addition of Stop Solution.
• The tubes are then placed in the spectrophotometer or colorimeter. The optical density (at 550nm) of each tube can be measured and the results calculated using a data processing program.

Incubation times	15 mins + 10 mins + 15 mins
Standard Range	0-386 nmol/L 0-300 ng/mL
Normal Ranges	Adults 67-163 |nmol/L Pregnant: 2nd Trimester 98-218 |nmol/L Pregnant: 3rd Trimester 90-197 |nmol/L
Detection Limit	6.45   nmol/L
Assay Reproducibility	Within-batch ±1SD nmol/L %CV 69±3 4.3 148±3 2.0 208±5 2.5
Assay Reproducibility	Between-batch ±1SD nmol/L %CV 69±3.5 5.1 146±5.2 3.5 210±8.0 3.8

T4 EIA Standards T4 EIA Antiserum T4 EIA Separation Reagent T4 EIA Derivative T4 EIA Wash Concentrate

EIA Substrate Reagent EIA Substrate Buffer EIA Stop Buffer T4 EIA Internal QC Sample Instruction booklet

Test tubes, pipettes, multivortex mixer, magnetic separator, 37°C water- bath and a colorimeter or spectrophometer.