How can a color test detect peroxide-based explosives?
Security personnel at airports, stadiums, and mail facilities screen surfaces for trace explosive residues using rapid point-of-contact tests — no laboratory, no instruments, just a swab, a reagent, and a five-second window. The question a screener must answer is practical: is there evidence of a threat that warrants further investigation?
In this activity you take the analyst's seat. First you validate the method: determine the lowest peroxide concentration your color test reliably detects (its detection limit). Then you apply it: screen four unknown swabs taken from luggage and make the call a screener makes every day.
Part 1 — Validate the method
You prepared solutions A–F by serial dilution: transfer 5 mL of the previous solution, add 15 mL of DI water — a 1:4 dilution at each step. Add reagent to each well, start the timer, and record the result.
| Solution | Transferred (mL) | Water added (mL) | Concentration (‰) | Result |
|---|
Well plate — live view
The detection limit is the lowest concentration that produced a positive result within five seconds. Based on your results above, record it here.
| Quantity | Value |
|---|---|
| detection limit |
Part 2 — Screen the unknown samples
Four fabric swabs were collected from luggage surfaces. Swab each with reagent, time five seconds, record the result — then make the screening decision.
| Sample | Result | Screening decision |
|---|
Screening report — export
Review the summary, then download the PDF report and submit it in Canvas with your answers. The report follows the format of a real rapid-screening record: method, detection limit, results, dispositions, and the analyst of record.