---
title: "Solution prep — mass to weigh"
method: POST
path: "/solution_prep"
tags: ["Analysis"]
---

# Solution prep — mass to weigh

`POST /solution_prep`

## Request

- Base URL: `https://seqbench.com/api/v1`
- URL: `https://seqbench.com/api/v1/solution_prep`
- Auth: none required

How much to weigh out for a target molarity and volume: mass = C × V × MW. The molar mass comes from a named reagent's molecular FORMULA (computed, not transcribed) or from a value you supply. A bare name matching two hydration states is refused with both named rather than resolved to a guess — EDTA disodium dihydrate against the free acid is a 27% error that leaves a solution looking exactly like a solution.

## Request body

- object
  - `concentration` number, required: Target concentration.
  - `concentrationUnit` 'M' | 'mM' | 'uM' | 'nM': Unit for concentration.
  - `volume` number, required: Volume to make.
  - `volumeUnit` 'L' | 'mL' | 'uL': Unit for volume.
  - `reagent` string: Reagent name as printed on the bottle, hydration state included (27 known). Ignored when molarMass is given.
  - `molarMass` number: Formula weight in g/mol. Overrides reagent.

## Response `200`

Tool ran successfully.

- SuccessResponse: Standard success envelope returned by every single-tool call.
  - `ok` unknown, required
  - `tool` string, required: The tool slug that ran.
  - `result` object, required: Tool-specific output object. Its shape depends on the tool — call `GET /{tool}` or see the docs for each tool's fields.
  - `gate` GateResult
    - `pass` boolean, required: True if and only if every hard check passed.
    - `checks` GateCheck[], required
      - `id` string, required
      - `label` string, required
      - `severity` 'hard' | 'soft', required
      - `pass` boolean, required
      - `message` string, required
      - `value` number
      - `threshold` string
    - `notChecked` string[], required: Honest list of what this gate does NOT verify.
  - `provenance` Provenance, required
    - `apiVersion` string, required
    - `tool` union, required: Tool slug, or an array of slugs (one per step) for a workflow.
      - string
      - string[]
    - `generatedAt` string, date-time, required: ISO 8601 timestamp of when the result was generated.

## Other responses

- `400`: Invalid argument or the tool could not run.
- `404`: Unknown tool.
- `429`: Rate limited (metered tools only). Body carries code `rate_limited` and retryable `true`; honor the Retry-After header.
- `503`: A metered tool is momentarily at capacity. The identical request should succeed after Retry-After; body carries code `upstream_unavailable`.

---

[API](https://skmtc.dev/seqbench/apis/seqbench-api.md) · [All operations](https://skmtc.dev/seqbench/apis/seqbench-api/llms.txt) · [OpenAPI document](https://skmtc.dev/seqbench/apis/seqbench-api/revisions/132575216865?raw)