Table1Example: Arrangement of blanks, standards, and
samples in the microwell strips
1 2 3 4
AStandard 1
16.00pg/mL
Standard 1
16.00pg/mL Sample 1 Sample 1
BStandard 2
8.00pg/mL
Standard 2
8.00pg/mL Sample 2 Sample 2
CStandard 3
4.00pg/mL
Standard 3
4.00pg/mL Sample 3 Sample 3
DStandard 4
2.00pg/mL
Standard 4
2.00pg/mL Sample 4 Sample 4
EStandard 5
1.00pg/mL
Standard 5
1.00pg/mL Sample 5 Sample 5
FStandard 6
0.50pg/mL
Standard 6
0.50pg/mL Sample 6 Sample 6
GStandard 7
0.25pg/mL
Standard 7
0.25pg/mL Sample 7 Sample 7
H Blank Blank Sample 8 Sample 8
4. Add 100 µL of Sample Diluent, in duplicate, to the blank wells.
5. Add 50 µL of Sample Diluent to the sample wells.
6. Add 50 µL of each sample, in duplicate, to the sample wells.
7. Prepare Biotin-Conjugate (see “Prepare Biotin‑Conjugate” on
page3).
8. Add 50 µL of Biotin-Conjugate to all wells.
9. Cover with an adhesive film, then incubate for 2 hours at room
temperature (18–25°C) on a microplate shaker (if available).
10. Prepare the Streptavidin-HRP (see “Prepare Streptavidin-HRP”
on page3).
11. Remove the adhesive film, then empty the wells. Wash the
microwell strips 6 times as previously described (see step2),
then proceed immediately to the next step.
12. Add 100 µL of prepared Streptavidin-HRP to all wells, including
the blank wells.
13. Cover with an adhesive film, then incubate for exactly 1hour at
room temperature (18–25°C) on a microplate shaker (if available).
14. Prepare Amplification Reagent I immediately before use (see
“Prepare Amplification Reagent I” on page4).
15. Remove the adhesive film, then empty the wells. Wash the
microwell strips 6 times as previously described (see step2),
then immediately proceed to the next step.
16. Add 100 µL of prepared Amplification Reagent I to all wells,
including the blank wells.
17. Cover with an adhesive film, then incubate for exactly 15 minutes
at room temperature (18–25°C) on a microplate shaker (if
available).
18. Prepare Amplification Reagent II immediately before use (see
“Prepare Amplification Reagent II” on page4).
19. Remove the adhesive film, then empty the wells. Wash the
microwell strips 6 times as previously described (see step2),
then immediately proceed to the next step.
20. Add 100 µL of prepared Amplification Reagent II to all wells,
including the blank wells.
21. Cover with an adhesive film, then incubate for exactly 30 minutes
at room temperature (18–25°C) on a microplate shaker (if
available).
22. Remove the adhesive film, then empty the wells. Wash the
microwell strips 6 times as previously described (see step2),
then proceed immediately to the next step.
23. Add 100 µL of Substrate Solution to all wells.
24. Incubate the microwell strips for about 20 minutes at room
temperature (18–25°C). Avoid direct exposure to intense light.
25. Quickly add 100 µL of Stop Solution to each well to stop the
enzyme reaction, then read the results immediately or within
one hour if the microwell strips are stored at 2°C to 8°C in
the dark. It is important to add the Stop Solution quickly and
uniformly throughout the microwell plate to completely inactivate
the enzyme.
26. Read the absorbance of each microwell on a spectrophotometer
using 450 nm as the primary wavelength (optionally, 620nm
as the reference wavelength; 610 nm to 650nm is acceptable).
Blank the plate reader according to the manufacturer's
instructions, using the blank wells. Determine the absorbance of
both the samples and the standards.
If the instructions in this protocol have been followed and
samples have been diluted 1:2 (50µL of sample + 50µL of
Sample Diluent), multiply each concentration by 2.
Note: If incubations are performed without shaking, OD values
can be lower than indicated (see “Calculation of results” on
page5), however, results are still valid.
Calculation of results
• Calculate the average absorbance values for each set of
duplicate standards and samples. Duplicates should be within
20 percent of the mean value.
• Create a standard curve by plotting the mean absorbance for
each standard concentration on the ordinate against the human
IL-4 concentration on the abscissa. Draw a best fit curve through
the points of the graph (a 5‑parameter curve fit is recommended).
• To determine the concentration of circulating human IL-4 for each
sample, first find the mean absorbance value on the ordinate,
then extend a horizontal line to the standard curve. At the point
of intersection, extend a vertical line to the abscissa, then read
the corresponding human IL-4 concentration.
• Multiply each concentration read from the standard curve by the
sample dilution factor. If the instructions in this protocol have
been followed and samples have been diluted 1:2 (50µL of
sample + 50 µL of Sample Diluent), multiply each concentration
by 2.
• Calculation of samples with a concentration exceeding standard
1 may result in incorrect, low human IL-4 levels. Such samples
require further external predilution with Sample Diluent according
to expected human IL-4 values to precisely quantitate the actual
human IL-4 level.
• It is suggested that each testing facility establishes a control
sample of known human IL-4 concentration and runs this
additional control with each assay. If the values obtained are not
within the expected range of the control, the assay results may
be invalid.
A representative standard curve is shown in Figure10.
Note: Do not use this standard curve to derive test results. Each
laboratory must prepare a standard curve for each group of
microwell strips assayed.
Note: The OD values of the standard curve may vary according
to the conditions or assay performance (e.g., operator, pipetting
technique, washing technique, or temperature eects). In
Human IL‑4 High Sensitivity ELISA Kit User Guide 5