Cascade Impactor Calculation From HPLC

Calculator Form

Stage Names

Stage Cut-off Diameters, µm

HPLC Peak Areas

Blank Area

Calibration Slope

Calibration Intercept

Extract Volume, mL

Dilution Factor

Stage Recovery, %

Assay Purity, %

Label Claim, µg Per Actuation

Number of Actuations

Fine Particle Cut-off, µm

Example Data Table

Field	Example Value	Meaning
Peak Areas	52000, 41000, 20000, 70000, 110000, 120000, 100000, 50000, 22000, 9000	Chromatogram response for each collected fraction.
Cut-off Diameters	0, 0, 8.06, 4.46, 2.82, 1.66, 0.94, 0.55, 0.34, 0	Positive values are used for aerodynamic sizing.
Slope	18000	Calibration response per µg/mL.
Extract Volume	10 mL	Volume used to recover drug from each stage.
Fine Cut-off	5 µm	Limit used for fine particle dose estimation.

Formula Used

Corrected Area = Peak Area − Blank Area − Intercept.

Concentration = Corrected Area ÷ Calibration Slope.

Stage Mass = Concentration × Extract Volume × Dilution Factor × Recovery Correction × Purity Correction.

Recovery Correction = 100 ÷ Recovery Percent.

Purity Correction = Purity Percent ÷ 100.

Cumulative Undersize Percent = Downstream Stage Mass ÷ Aerodynamic Sizing Dose × 100.

MMAD is interpolated at 50% cumulative undersize on a log diameter scale.

GSD = square root of D84.13 ÷ D15.87.

How To Use This Calculator

Enter stage names in the same order used by the impactor method.
Enter cut-off diameters in descending sizing order.
Use zero for induction port, preseparator, or filter entries.
Paste HPLC peak areas for the same stage order.
Enter calibration, extraction, dilution, recovery, and purity data.
Set the fine particle cut-off required by your method.
Press calculate and review the result above the form.
Use CSV or PDF export for a compact record.

Understanding Cascade Impactor Calculations

Cascade impactor studies convert collected drug into particle size results. HPLC supplies assay response for each stage. The calculator links both steps. It converts peak area into concentration. It then converts concentration into mass.

Why The Method Matters

Inhaled products need controlled particle size. Large droplets may stop in the throat. Very small particles may be exhaled. The fine particle dose often shows the respirable fraction. MMAD describes the median aerodynamic size. GSD shows spread across stages. Together, these values support development, release testing, and comparison work.

Using HPLC Stage Assay Data

Each stage extract normally has a chromatogram. The response is corrected with a calibration slope and intercept. A blank response can also be removed. The corrected concentration is multiplied by extract volume and dilution. Recovery and purity corrections can be applied. The result is the drug mass collected on each stage.

Particle Size Interpretation

Stage cut-off diameters must be entered in descending order. Early entries may represent the induction port or preseparator. These can use zero cut-off values. The calculator treats valid positive cut-offs as sizing stages. For every cut-off, it calculates the mass found downstream. This estimates the percentage of particles smaller than that diameter.

Quality Checks

A useful study has balanced recovery. The recovered dose should match the expected drug amount. Poor recovery may indicate extraction loss, transfer loss, or method error. Large throat deposition may show formulation or device issues. High fine particle fraction often means more respirable material. Yet results must be judged with the product method.

Best Use

Enter data from validated HPLC tables. Keep units consistent. Use micrograms per milliliter for concentration. Use milliliters for extraction volume. Check stage order before interpreting MMAD. Review the generated table before exporting. The CSV and PDF buttons help retain a compact record. Always compare results with approved laboratory procedures and acceptance limits.

Common Inputs

Common inputs include peak areas, calibration slope, intercept, blank area, dilution factor, extract volume, recovery, and purity. The expected dose field helps judge recovery. The fine particle cut-off can match the method. Many reports use five micrometers. Some compendial methods use another limit. Document the choice clearly for review. Record instrument settings with each tested sample set.

FAQs

What does this calculator do?

It converts HPLC peak areas into stage masses. It then estimates recovered dose, fine particle dose, fine particle fraction, MMAD, and GSD from cascade impactor data.

Can I use any cascade impactor layout?

Yes. Enter your own stage names and cut-off diameters. Keep the order consistent with your laboratory method and use zero for non-sizing locations.

Why are some cut-off values zero?

Zero values identify entries not used for size interpolation. Typical examples include induction port, preseparator, device deposits, or final filter records.

How is HPLC concentration calculated?

The calculator subtracts blank and intercept values from peak area. It divides the corrected area by the calibration slope to estimate concentration.

What is fine particle dose?

Fine particle dose is the estimated drug mass below the selected aerodynamic cut-off. Many methods use five micrometers, but your method may differ.

Why is MMAD sometimes not bracketed?

MMAD needs cumulative undersize values around 50 percent. If the entered stages do not bracket that point, the calculator cannot interpolate it reliably.

What does GSD mean?

GSD describes the spread of the aerodynamic particle size distribution. It uses interpolated D84.13 and D15.87 values from the cumulative undersize curve.

Can this replace a validated worksheet?

No. Use it for checking, teaching, and draft calculations. Final regulated work should follow approved methods, validated spreadsheets, and laboratory procedures.