Below is a **Standard Operating Procedure (SOP)** for **Oil and Grease Analysis in Water and Wastewater** based specifically on **APHA 5520B** (Standard Methods for the Examination of Water and Wastewater, 23rd Edition). This SOP follows the U.S. EPA's recommended format for SOPs (EPA QA/G-6) to ensure clarity, consistency, and compliance with environmental standards. APHA 5520B uses liquid-liquid extraction (LLE) with n-hexane followed by gravimetric analysis to determine oil and grease concentrations.
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### **Standard Operating Procedure for Oil and Grease Analysis in Water and Wastewater (APHA 5520B)**
**SOP Number**: LAB-OG-002
**Version**: 1.0
**Effective Date**: May 12, 2025
**Prepared by**: [Your Name/Title]
**Approved by**: [Supervisor/QA Officer Name/Title]
**Organization**: [Your Laboratory/Organization Name]
---
### **Table of Contents**
1. Purpose
2. Scope and Applicability
3. Definitions
4. Responsibilities
5. Health and Safety Warnings
6. Equipment and Supplies
7. Procedure
8. Quality Control and Quality Assurance
9. Data Management
10. References
11. Appendices
12. Revision History
---
### **1. Purpose**
This SOP describes the procedures for analyzing oil and grease in water and wastewater samples using liquid-liquid extraction with n-hexane and gravimetric determination, as outlined in APHA 5520B. The method quantifies total oil and grease (n-hexane extractable material) in aqueous samples.
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### **2. Scope and Applicability**
- **Scope**: This SOP applies to the gravimetric determination of oil and grease in water and wastewater samples (e.g., surface water, industrial effluents, municipal wastewater) using APHA 5520B.
- **Applicability**: Suitable for samples with oil and grease concentrations from 5 mg/L to 1000 mg/L. Used for environmental monitoring, research, and compliance with water quality standards.
- **Limitations**:
- Not suitable for volatile hydrocarbons (use APHA 5520F for volatile compounds).
- Does not distinguish between polar and non-polar fractions unless silica gel treatment is added (not covered in this SOP).
- High particulate matter may interfere; filtration may be required for some samples.
---
### **3. Definitions**
- **Oil and Grease**: Organic compounds (e.g., hydrocarbons, fatty acids, waxes, oils) extractable by n-hexane under acidic conditions (pH < 2).
- **LLE**: Liquid-Liquid Extraction.
- **MDL**: Method Detection Limit (approximately 5 mg/L for APHA 5520B).
- **QA**: Quality Assurance.
- **QC**: Quality Control.
- **Constant Weight**: Weight stable within ±0.1 mg after repeated drying and cooling cycles.
---
### **4. Responsibilities**
- **Laboratory Analyst**: Performs sample extraction, analysis, and data recording. Maintains and calibrates equipment.
- **Quality Assurance Officer**: Verifies QC compliance, reviews data, and approves SOP revisions.
- **Laboratory Supervisor**: Ensures staff training, oversees safety compliance, and approves analytical results.
---
### **5. Health and Safety Warnings**
- **Hazards**:
- n-Hexane is flammable and a neurotoxin; avoid inhalation and skin contact.
- Acidified samples (pH < 2) are corrosive.
- Hot glassware and ovens pose burn risks.
- **Precautions**:
- Perform extractions in a certified fume hood with adequate ventilation.
- Wear personal protective equipment (PPE): nitrile gloves, safety goggles, lab coat.
- Store n-hexane in a flammable cabinet away from ignition sources.
- Handle acids with care, using acid-resistant gloves and eye protection.
- Comply with OSHA regulations (29 CFR 1910.120).
- **Emergency Procedures**:
- For n-hexane spills, evacuate the area, ventilate, and follow the laboratory’s spill response plan.
- For skin or eye contact with n-hexane or acid, rinse with water for 15 minutes and seek medical attention.
---
### **6. Equipment and Supplies**
- **Equipment**:
- Separatory funnel (1 L or 2 L, glass, with PTFE stopcock).
- Analytical balance (0.1 mg precision, calibrated daily).
- Drying oven (103–105°C).
- Desiccator (with silica gel or equivalent).
- Fume hood (Class A, certified annually).
- Water bath or hot plate (for solvent evaporation, 60–70°C).
- **Supplies**:
- n-Hexane (pesticide-grade, ≥99% purity).
- Sodium sulfate (anhydrous, ACS grade).
- Hydrochloric acid (HCl, 6N) or sulfuric acid (1:1) for pH adjustment.
- Glass bottles (1 L, amber, with PTFE-lined caps).
- Aluminum weighing dishes or glass beakers (pre-cleaned, 100–250 mL).
- Glass wool (optional, for filtering high-particulate samples).
- Calibration standards (e.g., hexadecane/stearic acid mixture).
- **Storage**:
- Store n-hexane in a flammable cabinet.
- Store acids in an acid-resistant cabinet.
- Keep standards refrigerated at 4°C.
---
### **7. Procedure**
#### **7.1 Sample Collection and Preservation**
1. Collect 1 L of sample in a clean amber glass bottle with a PTFE-lined cap.
2. Adjust pH to <2 using HCl or H₂SO₄ at the time of collection to inhibit biodegradation.
3. Store samples at 4°C and analyze within 28 days.
4. Record sample ID, collection date, time, and preservation details in the chain-of-custody form.
#### **7.2 Equipment Preparation**
1. Clean all glassware with hot water, detergent, and rinse with n-hexane. Dry at 105°C for 1 hour.
2. Calibrate the analytical balance to ±0.1 mg using certified weights.
3. Pre-weigh aluminum dishes or beakers and store in a desiccator.
4. Verify fume hood functionality and oven temperature (103–105°C).
#### **7.3 Liquid-Liquid Extraction**
1. Allow samples to reach room temperature.
2. Transfer 1 L of sample to a 2 L separatory funnel. If particulates are present, filter through glass wool and note in the log.
3. Add 30 mL of n-hexane to the funnel.
4. Shake vigorously for 2 minutes, venting periodically to release pressure.
5. Allow phases to separate (5–10 minutes).
6. Drain the aqueous layer back into the sample bottle and collect the hexane layer in a clean beaker containing 10 g anhydrous sodium sulfate.
7. Repeat extraction twice more with 30 mL n-hexane each time, combining all hexane extracts in the beaker.
8. Let the extract sit for 15 minutes to remove residual water with sodium sulfate.
9. Decant the hexane extract into a clean, pre-weighed aluminum dish or beaker.
#### **7.4 Solvent Evaporation and Gravimetric Analysis**
1. Evaporate the hexane in a fume hood using a water bath or hot plate at 60–70°C until no solvent remains.
2. Dry the residue in an oven at 103–105°C for 1 hour.
3. Cool the dish in a desiccator to room temperature (approximately 30 minutes).
4. Weigh the dish on an analytical balance to the nearest 0.1 mg.
5. Repeat drying, cooling, and weighing until constant weight (±0.1 mg) is achieved.
6. Calculate oil and grease concentration:
\[
\text{Oil and Grease (mg/L)} = \frac{\text{(Final weight – Tare weight)} \times 1000}{\text{Sample volume (L)}}
\]
#### **7.5 Cleanup and Waste Disposal**
1. Dispose of n-hexane and acidified aqueous waste in labeled hazardous waste containers.
2. Clean glassware as described in Section 7.2.
3. Follow local, state, and federal regulations (e.g., RCRA) for waste disposal.
---
### **8. Quality Control and Quality Assurance**
- **Calibration**: Verify balance calibration daily with certified weights.
- **Blanks**:
- Analyze one laboratory reagent blank (1 L deionized water) per batch (≤20 samples). Blank must be <5 mg/L.
- **Duplicates**: Analyze one duplicate sample per batch. Relative percent difference (RPD) must be ≤20%.
- \[
\text{RPD} = \frac{|\text{Sample} - \text{Duplicate}|}{\text{(Sample + Duplicate)/2}} \times 100
\]
- **Spikes**: Analyze one matrix spike per batch with a known amount of hexadecane/stearic acid (e.g., 40 mg/L). Recovery must be 80–120%.
- **Control Standards**: Analyze a laboratory control sample (LCS) per batch. Results must be within ±10% of the known value.
- **Corrective Actions**:
- If QC criteria fail, stop analysis, investigate (e.g., check for contaminated solvent or glassware), and reanalyze affected samples.
- Document corrective actions in the laboratory logbook.
- **QA Audits**: Conduct annual internal audits to ensure SOP compliance.
---
### **9. Data Management**
- Record all data (sample ID, weights, volumes, QC results) in a laboratory logbook or electronic database.
- Use standardized forms (see Appendix A) for data entry.
- Validate data by the QA Officer before reporting.
- Report results in mg/L to one decimal place, including QC summary, to the client or regulatory authority.
- Retain records for at least 5 years in a secure, retrievable format.
---
### **10. References**
- American Public Health Association (APHA). 2017. *Standard Methods for the Examination of Water and Wastewater*, 23rd Edition, Method 5520B – Oil and Grease.
- U.S. Environmental Protection Agency. 2005. *Guidance for Preparing Standard Operating Procedures (SOPs)*, EPA QA/G-6.
- OSHA Standard 29 CFR 1910.120 – Hazardous Waste Operations and Emergency Response.
---
### **11. Appendices**
- **Appendix A**: Sample Data Recording Form
```
Sample ID: _______________
Date Analyzed: ___________
Sample Volume (L): _______
Tare Weight (mg): ________
Final Weight (mg): _______
Oil and Grease (mg/L): ___
Analyst: _________________
```
- **Appendix B**: QC Checklist
```
[ ] Blank < 5 mg/L
[ ] Duplicate RPD ≤ 20%
[ ] Spike Recovery 80–120%
[ ] LCS ±10% of known value
```
- **Appendix C**: Example Calculation
```
Sample Volume = 1.0 L
Tare Weight = 50.0000 g
Final Weight = 50.0250 g
Oil and Grease = [(50.0250 – 50.0000) × 1000] / 1.0 = 25.0 mg/L
```
---
### **12. Revision History**
| Version | Date | Changes |
|---------|------------|-----------------------------|
| 1.0 | 05/12/2025 | Initial release |
---
### **Notes**
- **APHA 5520B Specifics**:
- Focuses on total oil and grease without silica gel treatment (unlike EPA 1664, which includes SGT-HEM).
- Allows flexibility in solvent volume and extraction repetitions but recommends three 30 mL extractions for consistency.
- Suitable for general environmental testing but may not meet specific regulatory requirements (e.g., Clean Water Act) that mandate EPA 1664.
- **Training**: Analysts must be trained on this SOP and demonstrate proficiency through QC analyses (e.g., duplicates, spikes).
- **Customization**: Adapt the SOP to reflect laboratory-specific equipment or local regulations, with QA Officer approval.
If you need additional details, such as a specific data form, QC checklist, or modifications for a particular laboratory setup, let me know, and I can provide tailored content or generate example documents!
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