> For the complete documentation index, see [llms.txt](https://doc.duaer.com/zh/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://doc.duaer.com/zh/getting-started/mass-candidates.md).

# 在 Duaer 里列出质量候选物

在 Duaer 里按观测 m/z 与加合离子列出 PubChem 候选化合物。一次成功查询用 1 额度。
## 能拿到什么

Duaer 数据市场里的「Mass candidates」一次成功查询 1 额度，查不到结果也算一次。

每个候选带 ppm 误差和 InChIKey；只凭质量不能定结构。

逐步处理未知特征见 [用 Duaer 注释未知特征](/zh/getting-started/metabolic-dark-matter.md)。

## 在画布里检索

1. 打开节点创建器，选 Duaer 数据 → Mass candidates。
2. 填 m/z。
3. 选 Adduct（默认 [M+H]+），可选 Tolerance (ppm)，默认 5。
4. Limit 默认 10，最大 20。执行。

成功扣 1 额度；输入为空或来源失败不扣。

## 用 API 调用

- GET https://api.duaer.com/v1/data/mass-candidates?...
- Authorization: Bearer <Duaer key>

下方是与「复制技能」相同的英文技能。

## 调用技能（英文）

与数据市场「复制技能」一致。

```
---
name: duaer-mass-candidates
description: >-
  List PubChem compounds that fit an observed m/z and adduct through Duaer.
  One successful search uses 1 Duaer credit.
---

# Duaer mass candidates

Turn an observed m/z into candidate compounds from PubChem through Duaer with a Duaer key.

## Call

`GET https://api.duaer.com/v1/data/mass-candidates?mz=181.0707&adduct=%5BM%2BH%5D%2B&ppm=5&limit=10`

Header: `Authorization: Bearer <Duaer key>`

Use an account key or a model API key.

Get a Duaer key: https://skills.duaer.com/keys.md

`mz` is required.

- `mz` — observed m/z of the feature.
- `adduct` — optional. `neutral`, `[M+H]+`, `[M+Na]+`, `[M+NH4]+`, `[M+K]+`, `[M+H-H2O]+`, `[M-H]-`, `[M+Cl]-`, or `[M+FA-H]-`. Default `[M+H]+`.
- `ppm` — optional. Mass tolerance in ppm, up to 100. Default 5.
- `limit` — optional. From 1 to 20. Default 10.

## Result

Each item has `source`, `title`, `url`, `summary`, `cid`, `formula`, `monoisotopicMass`, `neutralMass`, `ppmError`, `inchikey`, and `iupacName`.
Candidates come in PubChem relevance order. Check a candidate's reference spectra with https://skills.duaer.com/mona.md or https://skills.duaer.com/massbank.md (`inchikey`).
To work an unannotated feature step by step, follow https://skills.duaer.com/metabolic-dark-matter.md.

## Credits

One successful search uses 1 credit, including a search that finds no match.
Empty input, a failed source, or no remaining credits uses 0.
No remaining credits returns 402 and does not search.
A missing key returns 401.

```
## Questions

### Duaer 的 Mass candidates 检索扣多少额度？

一次成功扣 1 额度，查不到结果也算一次；输入为空或来源失败不扣。

## 相关

- [用 Duaer 注释未知特征（代谢暗物质）](https://doc.duaer.com/zh/getting-started/metabolic-dark-matter.md)
- [在 Duaer 里查 MoNA 参考谱图](https://doc.duaer.com/zh/getting-started/mona.md)
- [在 Duaer 里检索化合物和药物](https://doc.duaer.com/zh/getting-started/compounds.md)