Calculator Inputs
Example Data Table
| Sample | Measured (µg/L) | Dilution | Corrected (µg/L) | Limit (µg/L) | Status |
|---|---|---|---|---|---|
| A | 4.2 | 1 | 4.2 | 10 | Within |
| B | 1.8 | 5 | 9.0 | 10 | Within |
| C | 3.1 | 10 | 31.0 | 10 | Exceeds |
| D | 0.2 | 1 | 0.2 | 10 | Within |
Formula Used
- Unit conversion: C(µg/L) = C(input) × multiplier.
- Dilution correction: C(corrected) = C(µg/L) × DF.
- Calibration mode: C(input) = (Signal − Intercept) / Slope.
- Percent of limit: % = 100 × C(corrected) / Limit.
- Mass in sample: m(µg) = C(corrected) × Volume(L).
How to Use This Calculator
- Select your sample type and unit.
- Choose direct concentration or instrument signal mode.
- Enter measured value, plus slope/intercept if needed.
- Enter the dilution factor applied during preparation.
- Set detection limit and your applicable safety limit.
- Submit to see corrected concentration and compliance status.
Professional Notes
Why arsenic reporting is typically in µg/L
Arsenic in water and extracts is often reported in micrograms per liter because health guidance values are usually in the single‑digit to tens range. Converting everything to µg/L standardizes comparisons across laboratories and methods. For example, 0.010 mg/L equals 10 µg/L, and 15 ppb equals 15 µg/L. Using one reporting unit also reduces transcription errors when dilution factors are applied during sample preparation.
How dilution and recovery change the reported concentration
When a sample is diluted before measurement, the instrument sees a lower concentration than the original sample. The corrected result is the converted concentration multiplied by the dilution factor. If a 1:10 dilution is used, a measured 0.9 µg/L becomes 9.0 µg/L. In routine workflows, documenting dilution is as important as documenting the raw reading, because a small instrument value can correspond to a meaningful real‑world concentration.
Interpreting calibration slope and intercept in daily work
Signal‑based instruments rely on a calibration curve where slope represents sensitivity and intercept represents baseline response. The calculator converts signal to concentration using (Signal − Intercept) ÷ Slope. A higher slope means more signal change per unit concentration, improving precision near low levels. Tracking slope drift over time can flag lamp aging, contamination, or matrix effects that may bias arsenic estimates.
Detection limits, qualifiers, and communicating uncertainty
Results below the method detection limit are commonly reported with a “less than” qualifier rather than a numeric value. This calculator labels such outcomes as below detection to support consistent reporting. If your MDL is 0.5 µg/L and the corrected result is 0.3 µg/L, the appropriate report is <0.5 µg/L. Clear qualifiers help decision makers avoid over‑interpreting noise as a true arsenic signal.
Compliance screening and prioritizing follow‑up actions
To triage samples, many teams compare corrected concentration to a chosen safety limit and compute percent of limit. A value at 80% may trigger resampling, while 120% can trigger confirmatory analysis and operational controls. Because guidance values vary by jurisdiction and sample type, the calculator lets you set the limit used. Saving the results table to CSV or PDF supports audits, trend reviews, and stakeholder communication. Consistency supports faster regulatory decisions.
FAQs
1) What limit should I use for drinking water?
Use the limit required by your regulator or client specification. Many programs use 10 µg/L for arsenic in drinking water, but local rules can differ. Enter the value you must report against.
2) How do I use calibration mode correctly?
Enter signal, slope, and intercept from the same calibration run and unit. The calculator computes concentration as (Signal − Intercept) ÷ Slope, then applies unit conversion and dilution.
3) What does “below detection” mean here?
If the corrected concentration is lower than the MDL you entered, the tool flags it as below detection. Report it as “< MDL” to avoid implying a precise value.
4) Why is my corrected value much higher?
A large dilution factor multiplies the converted concentration. Check that you entered the true preparation dilution, not the fraction. For a 1:10 dilution, use 10.
5) Can I estimate total arsenic mass in the sample?
Yes. Provide sample volume in milliliters and the tool estimates mass as concentration (µg/L) multiplied by volume (L). This is useful for mass‑balance checks.
6) Is this a substitute for laboratory QA/QC?
No. It supports calculations and reporting, but you still need blanks, spikes, calibration verification, and method controls. Always review instrument notes and quality flags.