# Standard Operating Procedure: [Procedure title]

> Laboratory standard operating procedure (SOP) with document control in
> the style expected under Good Laboratory Practice (GLP) and ISO/IEC
> 17025-type quality systems: purpose, scope, responsibilities, safety,
> materials, procedure with critical control points, quality control,
> calculations, records, troubleshooting, training and revision history.
> This is a document format, not safety or regulatory advice; your local
> risk assessment and quality system take precedence. Replace every
> `[bracketed]` value and every row marked *Example*.

<!--
Guidance: How to use this template
- Write for a trained person who has never done this procedure before.
  Each step is one action, in the imperative, with quantities and limits.
- Mark critical control points (CCP) clearly. A CCP is a step where a
  mistake invalidates the result or creates a hazard, so it has an
  acceptance limit and a recorded check.
- Do not issue the SOP until the risk assessment is approved and at least
  one person other than the author has performed it from the text alone.
- Only the controlled copy is valid. Printed copies must show "Uncontrolled
  when printed" and the version number.
-->

## Document control

<!-- Guidance: SOPs are controlled documents. The effective date is when staff must follow this version, after training is recorded. -->

| Field | Value |
|---|---|
| SOP number | [SOP-LAB-0042] |
| Title | [Procedure title] |
| Version | [1.0] |
| Status | [Draft / In review / Approved / Effective / Retired] |
| Effective date | YYYY-MM-DD |
| Review due | YYYY-MM-DD [typically 2 years after effective date] |
| Owner (author) | [@name, role] |
| Department | [Laboratory or unit] |
| Supersedes | [SOP-LAB-0042 v0.9 or "none"] |
| Classification | [Internal] |
| Copy status | Controlled copy; uncontrolled when printed |

### Approvals

| Role | Name | Signature | Date |
|---|---|---|---|
| Author | [@name] | [Signature] | YYYY-MM-DD |
| Technical reviewer | [@name] | [Signature] | YYYY-MM-DD |
| Laboratory manager | [@name] | [Signature] | YYYY-MM-DD |
| Quality assurance | [@name] | [Signature] | YYYY-MM-DD |
| Health and safety officer | [@name] | [Signature] | YYYY-MM-DD |

## Revision history

<!-- Guidance: Every change, however small, gets a new version and a summary. Major changes need retraining before the new version is effective. -->

| Version | Date | Author | Change summary | Retraining required |
|---|---|---|---|---|
| 0.9 | YYYY-MM-DD | [@name] | Draft for validation runs | Not applicable |
| 1.0 | YYYY-MM-DD | [@name] | First approved version | Yes |
| 1.1 | YYYY-MM-DD | [@name] | *Example:* Incubation tolerance changed from +/- 2 min to +/- 5 min after validation data review | No (read and acknowledge) |

## Contents

<!-- Guidance: Keep in sync with the headings below. -->

1. [Purpose](#1-purpose)
2. [Scope](#2-scope)
3. [Definitions and abbreviations](#3-definitions-and-abbreviations)
4. [Responsibilities](#4-responsibilities)
5. [Safety and hazards](#5-safety-and-hazards)
6. [Equipment and materials](#6-equipment-and-materials)
7. [Reagent preparation](#7-reagent-preparation)
8. [Procedure](#8-procedure)
9. [Quality control](#9-quality-control)
10. [Calculations](#10-calculations)
11. [Data recording and records](#11-data-recording-and-records)
12. [Troubleshooting](#12-troubleshooting)
13. [References](#13-references)
14. [Training record](#14-training-record)

## 1. Purpose

<!-- Guidance: One short paragraph: what the procedure achieves and why it must be done consistently. -->

This SOP describes how to [perform the procedure] so that results are
accurate, reproducible and traceable. *Example:* This SOP describes how
to determine total protein concentration in cell lysates using a
bicinchoninic acid (BCA) microplate assay, so that downstream assays load
equal amounts of protein.

## 2. Scope

<!-- Guidance: State what is in and out of scope: sample types, concentration range, instruments, sites. Out-of-scope cases prevent misuse. -->

This SOP applies to all staff performing [the procedure] in [laboratory
or unit]. Use outside the validated range below requires a documented
justification approved by the laboratory manager.

| In scope | Out of scope |
|---|---|
| *Example:* Cell lysates in RIPA buffer, 20-2,000 µg/ml | Samples containing more than 5 mM reducing agent |
| [Instrument model / location] | [Other instruments unless validated] |
| [Study types, GLP and non-GLP] | [Clinical diagnostic samples] |

## 3. Definitions and abbreviations

<!-- Guidance: Define terms a new staff member might misread. Keep it short. -->

| Term | Meaning in this SOP |
|---|---|
| CCP | Critical control point: a step with an acceptance limit that must be checked and recorded |
| QC | Quality control sample of known value run with each batch |
| Batch | All samples processed on one plate in one run |
| LLOQ / ULOQ | Lower and upper limits of quantitation of the validated range |
| [Term] | [Meaning] |

## 4. Responsibilities

<!-- Guidance: Name roles, not people. Everyone listed must be trained on this SOP. -->

| Role | Responsibility |
|---|---|
| Analyst | Performs the procedure as written, records data contemporaneously, reports deviations |
| Reviewer | Checks raw data, calculations and QC acceptance before results are released |
| Laboratory manager | Ensures staff are trained, equipment is maintained and the SOP is current |
| Quality assurance | Audits compliance, approves the SOP and its revisions |
| Health and safety officer | Approves the risk assessment and safety controls |

## 5. Safety and hazards

<!-- Guidance: Summarise the hazards and controls and point to the full risk assessment and safety data sheets. Never rely on this section alone for safety. -->

All staff must read the risk assessment [RA-ID] and the safety data
sheets before first use. Key hazards and controls:

| Hazard | Source | Control | PPE |
|---|---|---|---|
| *Example:* Skin and eye irritant | BCA working reagent (alkaline) | Handle in tray; avoid splashes | Nitrile gloves, lab coat, safety glasses |
| [Biological hazard] | [Cell lysates from BSL-2 lines] | [Work in biosafety cabinet] | [Gloves, coat] |
| [Physical hazard] | [Plate reader moving parts] | [Keep lid closed during run] | Not applicable |

**Waste disposal:**

| Waste | Disposal route |
|---|---|
| Liquid chemical waste | [Labelled alkaline waste container] |
| Biological waste | [Autoclave or chemical inactivation, then clinical waste] |
| Plastic consumables | [Biohazard bag if contaminated, otherwise general waste] |

**Spills and exposure:** [Follow spill procedure SOP-HS-0003; eye
exposure: rinse at eyewash for 15 minutes and report the incident.]

## 6. Equipment and materials

<!-- Guidance: List everything needed, with catalogue numbers where they matter. Equipment must be within calibration on the day of use. -->

### 6.1 Equipment

| Equipment | Asset ID | Requirement |
|---|---|---|
| Microplate reader | [ID] | *Example:* Absorbance at 562 nm, calibration within date |
| Incubator | [ID] | 37 °C +/- 1 °C, verified with calibrated thermometer |
| Single and multichannel pipettes | [IDs] | Calibrated within 12 months |
| [Equipment] | [ID] | [Requirement] |

### 6.2 Materials and reagents

| Material | Supplier / catalogue no. | Storage | Notes |
|---|---|---|---|
| [BCA reagent A and B] | [Supplier, cat. no.] | Room temperature | Record lot numbers |
| [Albumin standard, 2 mg/ml] | [Supplier, cat. no.] | 4 °C | Do not freeze |
| [96-well flat-bottom plates] | [Supplier, cat. no.] | Room temperature | Clear polystyrene |
| [Material] | [Supplier] | [Storage] | [Notes] |

## 7. Reagent preparation

<!-- Guidance: Give exact quantities, order of addition, labelling and stability. Every prepared reagent gets a label with name, concentration, preparation date, expiry and initials. -->

| Reagent | Preparation | Stability | Label |
|---|---|---|---|
| *Example:* BCA working reagent | Mix reagent A and B at 50:1 (for one plate, 10 ml A + 200 µl B). Mix until uniformly green. | 24 h at room temperature | Name, date, time, initials |
| Standard series | Dilute albumin standard in the sample buffer to 2,000, 1,500, 1,000, 750, 500, 250, 125, 25 and 0 µg/ml | Prepare fresh each run | Name, date, initials |
| [Reagent] | [Preparation] | [Stability] | [Label] |

## 8. Procedure

<!-- Guidance: Number every step. One action per step. Put acceptance limits next to the step, and mark critical control points with CCP. -->

The procedure is shown as a flow, then as numbered steps.

```mermaid
flowchart TD
    A[Check equipment and reagents] --> B["Prepare standards and QC (CCP-1)"]
    B --> C[Load plate]
    C --> D["Incubate 30 min at 37 °C (CCP-2)"]
    D --> E[Read absorbance]
    E --> F{"QC and curve accepted? (CCP-3)"}
    F -->|Yes| G[Calculate and report]
    F -->|No| H[Reject batch and investigate]
```

### 8.1 Before starting

1. Confirm the SOP version at the point of use is the current effective version.
2. Check calibration labels on the plate reader, incubator and pipettes; do not proceed if any is out of date.
3. Record reagent lot numbers and expiry dates on the run sheet [Form F-0042-1].
4. Allow reagents and samples to reach room temperature for 30 minutes.

### 8.2 Procedure steps

| Step | Action | Acceptance limit | CCP |
|---|---|---|---|
| 1 | Prepare the standard series as in section 7 | Visible, bubble-free volumes | CCP-1 |
| 2 | Dilute samples 1:5 in sample buffer if expected above 2,000 µg/ml | Diluted value within the standard range | |
| 3 | Pipette 25 µl of each standard, QC and sample into duplicate wells following the plate map | Plate map recorded before pipetting | |
| 4 | Add 200 µl of working reagent to each well with a multichannel pipette | Within 5 minutes across the plate | |
| 5 | Cover the plate and shake for 30 s | | |
| 6 | Incubate at 37 °C for 30 min | *Example:* 30 min +/- 2 min, 37 °C +/- 1 °C, start and end times recorded | CCP-2 |
| 7 | Cool to room temperature for 5 min | | |
| 8 | Read absorbance at 562 nm | Reader self-check passed | |
| 9 | Export the raw data file to [validated location] | File name per section 11 | |
| 10 | Evaluate standard curve and QC against section 9 | All criteria met | CCP-3 |

### 8.3 After completion

1. Dispose of waste as in section 5.
2. Clean the work area with [disinfectant] and record cleaning on [log].
3. Submit the run sheet and raw data for review.

## 9. Quality control

<!-- Guidance: Define what is run with each batch and the acceptance criteria. Say exactly what happens when a criterion fails. -->

Each batch includes a blank, a full standard curve and QC samples at two
levels. The batch is accepted only if all criteria are met.

| QC element | Frequency | Acceptance criterion | Action on failure |
|---|---|---|---|
| Blank | Every batch | *Example:* Absorbance below 0.15 | Reject batch; check reagent |
| Standard curve | Every batch | $R^2 \ge 0.99$; back-calculated standards within 15% of nominal | Reject batch; repeat |
| QC low and high | Every batch, duplicate | Within 20% of assigned value | Reject batch; investigate per deviation SOP |
| Duplicate agreement | Every sample | CV at most 10% | Repeat the sample |

## 10. Calculations

<!-- Guidance: Give every formula with units and a worked example. If software does the calculation, name the validated template and version. -->

Fit the blank-corrected standards with a [linear or four-parameter
logistic] model. For a linear fit:

$$
A_{\text{corr}} = A_{562} - A_{\text{blank}}, \qquad C = \frac{A_{\text{corr}} - b}{m} \times D
$$

where $m$ is the slope, $b$ the intercept and $D$ the dilution factor.

Precision between duplicates is checked as the coefficient of variation:

$$
\text{CV}\,(\%) = \frac{s}{\bar{x}} \times 100
$$

*Example:* With $m = 0.00112$ per µg/ml, $b = 0.031$,
$A_{\text{corr}} = 0.871$ and $D = 5$:
$C = (0.871 - 0.031) / 0.00112 \times 5 = 3{,}750$ µg/ml.

Validated calculation template: [Spreadsheet name, version, validation
reference].

## 11. Data recording and records

<!-- Guidance: Say where raw data, run sheets and results are stored, how files are named and how long they are kept. Records must be attributable and contemporaneous. -->

| Record | Format | Location | Retention |
|---|---|---|---|
| Run sheet [F-0042-1] | Paper or ELN | [ELN project / archive] | [Per retention policy, for example 10 years for GLP studies] |
| Raw data file | [.csv / instrument format] | [Validated server path] | [Period] |
| Calculation file | [Template] | [Location] | [Period] |
| Results report | [PDF] | [LIMS] | [Period] |

File naming: *Example:* `SOP0042_YYYY-MM-DD_[analyst initials]_[plate number].csv`.
Corrections are made by a single line through the original, with the
correct value, initials, date and reason. Never use correction fluid or
overwrite electronic raw data.

## 12. Troubleshooting

<!-- Guidance: List the problems people actually meet. Each row gives the likely cause and the fix. Deviations still need recording even if fixed. -->

| Problem | Likely cause | Action |
|---|---|---|
| High blank absorbance | *Example:* Contaminated or old working reagent | Prepare fresh working reagent; check buffer compatibility |
| Poor standard curve fit | Pipetting error, wrong dilution | Repeat standards; check pipette calibration |
| Duplicates disagree | Bubbles in wells, edge effects | Pop bubbles with a clean tip; avoid outer wells |
| Sample above top standard | Concentration too high | Dilute further and repeat |
| [Problem] | [Cause] | [Action] |

Any failure of a CCP or QC criterion is a deviation and is recorded on
[deviation form] with the impact assessment and corrective action.

Deviation handling follows these steps:

1. Stop and make the situation safe. Do not continue a run that has failed a CCP.
2. Record what happened, when, and which samples are affected, on the run sheet and the deviation form, the same day.
3. Inform the reviewer and, for GLP studies, the study director, who decides on the impact on the study.
4. Investigate the root cause and record corrective and preventive actions with owners and dates.
5. Quality assurance reviews the deviation log at least [quarterly] and trends recurring causes.

*Example:* Incubator temperature found at 39 °C at the end of step 6.
Batch rejected, samples re-assayed the next day from retained aliquots,
incubator taken out of service and recalibrated; root cause was a faulty
door seal, replaced under work order [WO-ID].

## 13. References

<!-- Guidance: Cite manufacturer instructions, validation reports and related SOPs with version numbers. -->

Documents referenced by this SOP:

| ID | Document |
|---|---|
| REF-01 | [Manufacturer instructions for kit, version] |
| REF-02 | [Method validation report VAL-0042] |
| REF-03 | [Risk assessment RA-ID] |
| REF-04 | [Related SOPs: pipette calibration, deviation handling, waste disposal] |
| REF-05 | OECD Principles of Good Laboratory Practice, as applicable to the study |

## 14. Training record

<!-- Guidance: Staff may perform the procedure unsupervised only after training is signed off. Keep this table or reference the training system. -->

| Trainee | Trainer | Training method | Competence assessed by | Date signed off |
|---|---|---|---|---|
| [@name] | [@name] | *Example:* Read SOP, observed 1 run, performed 2 supervised runs with QC passing | [@name] | YYYY-MM-DD |
| [@name] | [@name] | [Method] | [@name] | YYYY-MM-DD |

## Standard and licence note

Based on common laboratory quality practice for standard operating
procedures, with document control in the style expected under the OECD
Principles of Good Laboratory Practice and ISO/IEC 17025-type quality
systems. This template is original text written for this collection and
reproduces no text from those documents; consult them and your quality
system for normative requirements. This is a document format, not safety
or regulatory advice. Template licence: MIT.