This procedure describes how to prepare dilutions of less than 25x or greater than 100x using the appropriate RaPID AssaysÒ Sample Diluent and components of the RaPID PrepÔ Universal Range Extension Kit. Preparing dilutions of 25x to 100x are already described in the package insert of the Universal Range Extension Kit. Serial dilutions using components of the Universal Range Extension Kit are required for preparing dilutions greater than 100x. In order to select the appropriate dilution factor for a particular project, certain factors must first be assessed. These include the project action level, the reactivity of the contaminant, the extraction efficiency of the contaminant, the analytical confidence of the screening test and its calibrator working range.
Reagents: RaPID Assay Sample Diluent* for the appropriate assay.
1) RaPID Prep Universal Range Extension Kit*
2) Precision pipettes* and tips capable of delivering 100 and 250 mL
3) Eppendorf Adjustable Pipette* (500 to 2500mL) Model 4810 or equivalent
4) Protective gloves
5) Permanent marking pen
*Available from SDI
Determine the appropriate dilution factor for your project. Consult SDI FACTOR Technical Services if assistance is needed. For dilutions of 3 to 24x: Refer to Dilution Chart (over). For dilutions greater than 100x: Refer to Dilution Chart (over). Select two smaller dilution factors whose product equals the desired larger dilution factor. For example: a dilution factor of 200x could be prepared by first diluting the sample or extract by 20x, followed by an additional serial dilution of 10x. Consult SDI Technical Services if assistance is needed in making this determination. For dilutions of 25 to 100x: Refer to package insert of the Universal Range Extension Kit.
Write sample information on the labels provided. Apply labels to vials. From Column A in Dilution Chart find the Dilution Factor that you have determined is appropriate for your project. Determine the volume of Sample Diluent to pipette from Column B. Set the volume of Sample Diluent on the adjustable pipette. Attach a clean tip to the adjustable pipette. Transfer the appropriate volume of RaPID Sample Diluent into clean dilution vials. Refer to pipette instructions on setting volumes. Using a clean tip and precision pipette, transfer the appropriate volume of sample or extract from Column C into each vial. Cap each vial and mix by inverting several times. This mixture can now be measured as “sample” according to the package insert of the appropriate RaPID Assay.
CALCULATION OF RESULTS: Apply the dilution factor used in your dilution protocol to the factors already introduced by previous extraction and dilution steps.
PROCEDURAL NOTES: The accuracy of the final result will depend in part on the care taken in pipeting the sample into the diluent.