Source: https://guthlabs.ai/docs/instruments/protein-concentration-bca-bradford-standard-curve/implementation/

instrument implementation / implementation-contract

# Protein Concentration (BCA/Bradford standard curve) implementation

A source-bound implementation contract for Protein Concentration (BCA/Bradford standard curve); deployment and executable qualification remain separate.

Status: **VERIFIED_WITH_ERRATA**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-with-binding-errata

**Evidence ID**: t6-097

**Effect**: Computation or source lookup only

## Input and validation requirements

The regression is undefined when all standard concentrations are identical, and the specification does not state validation behavior for negative inferred concentrations or ambiguous signed absorbance values. The specification also has no actual multi-regime formula branch despite a potential slope-sign boundary.

## Required corrections

````
[
  {
    "vector": 2,
    "field": "R_squared",
    "wrong": 0.9964474245,
    "correct": 0.9991119005,
    "cause": "slope/intercept exact, R2 slipped (SSE=1e-4, SST=0.1126 -> 0.999112)"
  }
]
````

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "standard_concentrations_mg_per_mL": [
      0,
      1,
      2,
      3
    ],
    "standard_absorbances_AU": [
      0.05,
      0.25,
      0.45,
      0.65
    ],
    "sample_absorbances_AU": [
      0.35,
      0.05
    ]
  },
  "expected_outputs": {
    "slope_m_AU_per_mg_per_mL": 0.2,
    "intercept_b_AU": 0.05,
    "R_squared": 1,
    "sample_concentrations_mg_per_mL": [
      1.5,
      0
    ]
  },
  "working": "The points lie exactly on A=0.20c+0.05: for c=0,1,2,3, predicted A values are 0.05, 0.25, 0.45, 0.65. Therefore m=0.20 AU/(mg/mL), b=0.05 AU, and every residual is 0, so SSE=0 and R²=1−SSE/SST=1. For sample A=0.35: c=(0.35−0.05)/0.20=0.30/0.20=1.5 mg/mL. For sample A=0.05: c=(0.05−0.05)/0.20=0/0.20=0 mg/mL. The second sample is the zero-concentration/intercept edge case."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/protein-concentration-bca-bradford-standard-curve/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/protein-concentration-bca-bradford-standard-curve/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/protein-concentration-bca-bradford-standard-curve/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche6/tranche6-results.json`

- `tranche errata record`