LabCalc

Standard Addition Calculator

c(sample) = |b / m| × V(final) / V(sample)

Determine a sample concentration from spiked aliquots using the x-intercept, with volumes handled explicitly.

Additions

mL

Added concentration in the final solution → response

1
2
3
4

Result

3.16234 mg/L

Dilution factor 5 applied to the x-intercept.

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Calculation

  1. Regression of response against added concentration

    y = m·x + b

    y = 0.1774·x + 0.1122 (R² = 0.999992)

  2. x-intercept

    c(sample in final solution) = |b / m|

    |0.1122 / 0.1774|

    0.632469 mg/L

  3. Correct for the sample dilution

    c(original sample) = c(in final) × V(final) / V(sample)

    0.632469 × 50 mL / 10 mL

    3.16234 mg/L

Inputs

Mode
Constant final volume
Sample aliquot
10 mL
Final volume
50 mL
Addition 1
0 mg/L → 0.112
Addition 2
0.5 mg/L → 0.201
Addition 3
1 mg/L → 0.29
Addition 4
1.5 mg/L → 0.378

Added concentrations must be expressed as the concentration contributed to the FINAL solution, not the spike stock concentration.

Volumes are never assumed to be unchanged: in variable-volume mode every final volume must be entered and responses are volume-corrected before regression.

Standard addition assumes the response is linear over the range used and that the added standard behaves identically to the analyte in the sample.

About this calculator

Standard addition corrects for matrix effects by spiking the sample itself. The responses are regressed against the concentration added, and the magnitude of the x-intercept gives the analyte concentration contributed by the sample in the final solution. Multiplying by the dilution factor returns the concentration in the original sample.

Added concentrations must be expressed as the concentration contributed to the final solution, not the spike stock concentration. In variable-volume mode every final volume must be entered and the responses are volume-corrected before regression — LabCalc never assumes the volume is unchanged.

LabCalc is provided as a calculation aid. Users remain responsible for verifying calculations, units, chemical compatibility, experimental procedures and applicable safety requirements before laboratory use.

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Solve C1 × V1 = C2 × V2 for any missing variable.

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