Chain of Custody for Environmental Samples: Complete Guide

What is Chain of Custody?

A Chain of Custody (CoC) is a legal document that tracks the possession, handling and transfer of environmental samples from the point of collection through laboratory analysis and final disposal. It establishes an unbroken trail of accountability that proves samples were not tampered with or compromised.

Legal Importance

Establishes admissibility of analytical results in regulatory proceedings and litigation
Provides documented proof that samples were collected, transported and analyzed following standard protocols
Required by environmental regulations (CCME, EPA, provincial ministries) for compliance monitoring
Protects the laboratory, consultant and client from disputes about sample integrity

When Required

All Phase II Environmental Site Assessments (ASTM E1903, CSA Z769)
Regulatory compliance monitoring (discharge permits, remediation programs)
Contaminated site investigations and delineation
Confirmation sampling during and after remediation
Drinking water quality testing
Any sampling where results may be used in legal or regulatory proceedings

CoC Form Fields Explained

Every field on a CoC form serves a specific purpose. Incomplete or incorrect forms are the leading cause of sample rejection and data qualification by laboratories.

Project Information

Project name / number: Client reference identifier for billing and reporting
Client / company: Organization responsible for the project
Site address: Physical location where samples were collected
Lab work order #: Lab-assigned tracking number (may be pre-printed or assigned at receipt)
Purchase order #: Authorization for laboratory billing

Sampler Information

Sampler name: Person who physically collected the samples
Company: Consulting firm or organization
Phone / email: Contact for lab questions about samples
Sampling date and time: Exact date and time each sample was collected (24-hour format preferred)

Sample Details

Sample ID: Unique identifier matching the label on the container. Must be consistent with field notes and site plan.
Matrix: Sample type - soil, groundwater, surface water, sediment, soil vapor, air, waste
Container type: Glass, plastic, VOA vial, brass sleeve, etc.
Number of containers: How many bottles/jars per sample
Preservative: Chemical or temperature preservation applied (HNO3, HCl, H2SO4, NaOH, ice)

Analysis & Logistics

Analysis requested: Specific parameters or analytical methods (metals by ICP-MS, VOCs by EPA 8260, etc.)
Turnaround time: Standard (10-15 business days), rush (5 days), emergency (24-48 hours)
Reporting limits: Specify if non-standard detection limits are required
Special instructions: Filtered vs. unfiltered, specific methods, regulatory program requirements

Custody Transfer

Relinquished by: Printed name, signature and date/time of person handing over samples
Received by: Printed name, signature and date/time of person accepting samples
Each transfer: Every handoff (field to courier, courier to lab) requires a new signature pair
Custody seal: Tamper-evident seal on cooler - note if intact or broken at each transfer

Condition on Receipt

Temperature: Lab records cooler temperature at receipt (target: 4 +/- 2 degrees C)
Custody seal status: Intact or broken
Sample condition: Labels legible, containers intact, correct preservative present
Discrepancies: Any differences between CoC and actual samples received

Sample Preservation Requirements

Proper preservation prevents chemical and biological changes that would alter analytical results. Preservation must be applied at the time of collection or using pre-preserved containers supplied by the laboratory.

Parameter Group	Preservative	Container	Max Holding Time	Notes
Metals & Inorganics
Total Metals	HNO3 to pH < 2	Plastic (HDPE) or glass, 250 mL	180 days	Acid preservative prevents adsorption to container walls
Dissolved Metals	Field filter (0.45 um) + HNO3 to pH < 2	Plastic (HDPE), 250 mL	180 days	Must filter in field before preserving
Mercury	HNO3 to pH < 2	Glass, 250 mL	28 days	Shorter hold time than other metals
Volatile Organics
VOCs (water)	HCl to pH < 2, cool to 4 degrees C	3 x 40 mL glass VOA vials, zero headspace	14 days	Zero headspace is critical - no air bubbles
VOCs (soil)	Methanol or sodium bisulfate, cool to 4 degrees C	EnCore sampler or glass jar	14 days (48 hrs to extract if unpreserved)	Minimize headspace. Some programs require EnCore or equivalent.
BTEX	HCl to pH < 2, cool to 4 degrees C	3 x 40 mL glass VOA vials	14 days	Subset of VOC analysis
Petroleum Hydrocarbons
PHC / TPH (water)	HCl to pH < 2, cool to 4 degrees C	Amber glass, 1 L	14 days (7 days for some fractions)	CCME Tier 1 fractions: F1 (C6-C10), F2 (C10-C16), F3 (C16-C34), F4 (C34-C50)
PHC / TPH (soil)	Cool to 4 degrees C	Glass jar, 250 g minimum	14 days	Minimize headspace, fill jar as full as practical
Semi-Volatile Organics
PAHs	Cool to 4 degrees C	Amber glass, 1 L (water) / glass jar (soil)	14 days (extract); 40 days (analyze)	Light-sensitive - use amber glass
PCBs	Cool to 4 degrees C	Amber glass, 1 L (water) / glass jar (soil)	14 days (extract); 40 days (analyze)	Avoid plastic containers
Pesticides / Herbicides	Cool to 4 degrees C	Amber glass, 1 L	14 days (extract); 40 days (analyze)	Method-specific; confirm with lab
General Chemistry
pH	Cool to 4 degrees C	Plastic or glass, 100 mL	Analyze immediately (15 min field; 24 hrs lab)	Best measured in field with calibrated meter
Conductivity / TDS	Cool to 4 degrees C	Plastic or glass, 250 mL	28 days	Conductivity best measured in field
Nutrients (NO3, NH3, PO4)	H2SO4 to pH < 2, cool to 4 degrees C	Plastic (HDPE), 250 mL	28 days	Parameter-specific; confirm with lab
BOD / COD	Cool to 4 degrees C (BOD); H2SO4 to pH < 2 (COD)	Plastic or glass, 1 L	48 hrs (BOD); 28 days (COD)	BOD is very time-sensitive
Microbiological
Coliforms / E. coli	Sodium thiosulfate (dechlorination), cool to 4 degrees C	Sterile bottle (lab-supplied), 250 mL	24 hours (6 hrs recommended)	Must use sterile container with thiosulfate if chlorinated water

Maximum Holding Times

Holding time is the maximum interval between sample collection and analysis. Exceeding holding times results in qualified data (flagged with "HT" qualifier) that may not be accepted by regulators. Holding time starts at the moment of collection, not at lab receipt.

Parameter	Water Holding Time	Soil Holding Time	Consequence of Exceedance
VOCs / BTEX	14 days	14 days (48 hrs if unpreserved)	Volatile loss - results biased low. Data usually rejected.
PHC F1 (C6-C10)	14 days	14 days	Volatile fraction loss. May underestimate contamination.
PHC F2-F4	14 days	14 days	Less volatile but biodegradation may reduce results.
PAHs	14 days to extract, 40 days to analyze	14 days to extract, 40 days to analyze	Photodegradation and biodegradation. Results biased low.
PCBs	14 days to extract, 40 days to analyze	14 days to extract, 40 days to analyze	Biodegradation possible. Data qualified.
Total Metals	180 days	180 days	Precipitation, adsorption. Usually accepted with qualification.
Mercury	28 days	28 days	Volatilization and adsorption. Significant bias risk.
Nutrients	28 days (preserved)	28 days	Biological transformation. Results may not reflect field conditions.
pH	15 min (field) / 24 hrs (lab)	N/A (field measurement)	CO2 exchange, biological activity. Data rejected if exceeded significantly.
BOD	48 hours	N/A	Biological degradation makes results meaningless.
Coliforms / E. coli	24 hours (6 hrs recommended)	N/A	Die-off or regrowth. Results not representative.

Container Types & Requirements

Container material, color and closure type prevent contamination, adsorption and photodegradation. Always use laboratory-supplied containers that are certified clean to the required detection limits.

Container Type	Material	Common Uses	Advantages	Limitations
40 mL VOA Vial	Borosilicate glass with PTFE-lined septum cap	VOCs, BTEX, THMs in water	Zero headspace seal prevents volatile loss. Pre-preserved options available.	Small volume. Fragile. Cannot be used for soil.
Amber Glass Bottle	Amber borosilicate glass with PTFE-lined cap	PAHs, PCBs, pesticides, PHC in water	Blocks UV light. Inert to organics. No leaching.	Fragile. Heavier than plastic. More expensive.
Clear Glass Bottle	Borosilicate glass with PTFE-lined cap	General organics, oil and grease	Inert. Visual inspection of sample possible.	No UV protection. Fragile.
HDPE Bottle	High-density polyethylene	Metals, inorganics, nutrients, general chemistry	Lightweight. Durable. No breakage risk. Inexpensive.	Adsorbs some organics. Not suitable for VOC/SVOC samples.
Glass Jar (wide-mouth)	Clear or amber glass	Soil samples for organics, PHC, PAHs, metals	Easy to fill from auger or split spoon. Inert.	Fragile. Heavier. Harder to seal airtight.
Sterile Bottle	HDPE or polypropylene with sodium thiosulfate tablet	Microbiological samples (coliforms, E. coli)	Pre-sterilized. Thiosulfate neutralizes residual chlorine.	Single use. Do not rinse or pre-condition.
EnCore / Terra Core Sampler	Plastic barrel with plunger	Soil VOCs (low-level)	Seals sample immediately. Minimizes volatile loss from handling.	Requires specific extruder at lab. Small sample size (~5 g).
Brass Sleeve / Liner	Brass or stainless steel	Soil gas, VOC soil samples in some programs	No headspace. Collects undisturbed sample.	Requires specific sampling equipment. Program-specific.

Glass vs. Plastic - Quick Rule

Organics (VOCs, SVOCs, PHC, PAHs, PCBs): Always glass. Plastic adsorbs organic compounds.
Metals and inorganics: Plastic (HDPE) preferred. Glass can leach metals like boron and silica.
Microbiology: Lab-supplied sterile containers only.

Volume Requirements

Water: Typically 250 mL - 1 L per parameter group. Labs provide kit lists per project.
Soil: Minimum 250 g for most analyses. 500 g preferred for multiple parameters.
VOA vials: 3 vials per sample (2 for analysis, 1 archive).
Always order 10-15% extra containers to account for breakage and additional QA/QC samples.

Common CoC Errors That Invalidate Samples

These errors can result in data qualification, sample rejection or invalidation of entire sampling events. Each one can cost thousands in re-mobilization and delays. Prevention is always cheaper than correction.

Missing Signatures

Every custody transfer requires both a "relinquished by" and "received by" signature with date and time. A single missing signature breaks the chain and can make results inadmissible in regulatory proceedings.

Incorrect Preservation

Wrong acid, wrong pH, no preservative when required. Lab cannot retroactively preserve samples. Results from incorrectly preserved samples are typically qualified or rejected outright.

Exceeded Holding Times

Samples sitting in a cooler over a weekend, holidays or courier delays. Clock starts at collection, not lab receipt. Plan sampling to ensure samples arrive at the lab well within holding times.

Broken Chain of Custody

Unattended samples without custody seals, unlocked vehicles, samples left at a reception desk. Anyone with access to unsecured samples breaks the chain. Use tamper-evident seals on all coolers.

Mislabeled Containers

Sample ID on container does not match CoC, duplicate IDs used, illegible labels (rain-smeared), wrong sample ID written on form. Always use waterproof labels and permanent markers.

Temperature Exceedance

Cooler arrives at lab above 6 degrees C (target is 4 +/- 2 degrees C). Use sufficient ice, pre-chill containers and insulate coolers. Lab records temperature at receipt - exceedances are flagged.

Headspace in VOA Vials

Air bubbles in VOC vials cause volatilization losses. Vials must be filled completely with a meniscus and capped with zero headspace. Invert and tap to check - any visible bubble means re-collect.

CoC / Sample Mismatch

Number of containers received does not match CoC, parameters listed do not match bottles provided, or samples listed on CoC are not in the cooler. Always reconcile the CoC against actual containers before shipping.

QA/QC Sample Requirements

Quality assurance and quality control (QA/QC) samples verify that field and laboratory procedures are not introducing errors. Most regulatory programs require a minimum frequency of QA/QC samples. These are recorded on the CoC alongside regular samples using blind identifiers so the lab does not know which are QA/QC.

Field Duplicates

Frequency: 1 per 10 samples (10%) or 1 per sampling event, whichever is greater.

Purpose: Assess sampling precision and natural variability. Collected from the same location at the same time using the same method.

Acceptance: Relative percent difference (RPD) typically < 30% for water, < 50% for soil (higher due to natural heterogeneity).

Labeling: Assign a blind sample ID (e.g., "QC-01") so the lab analyzes it without knowing it is a duplicate.

Trip Blanks

Frequency: 1 per cooler containing VOC samples.

Purpose: Detect contamination introduced during transport and handling. Pre-prepared by the lab with analyte-free water in sealed VOA vials.

Handling: Travels with samples from lab to field and back. Never opened in the field. Analyzed for VOCs only.

Acceptance: All analytes should be non-detect. Detections indicate contamination during transport.

Equipment Blanks

Frequency: 1 per day or 1 per decontamination of non-dedicated equipment.

Purpose: Verify decontamination procedures are effective. Rinse deionized or distilled water through cleaned sampling equipment and collect in sample containers.

When required: Whenever non-dedicated (shared) equipment is used between sample locations. Not needed for dedicated or single-use equipment.

Acceptance: All analytes should be non-detect. Detections indicate cross-contamination between samples.

QA/QC Type	Minimum Frequency	Parameters Analyzed	Prepared By	Key Rule
Field Duplicate	1 per 10 samples	Same as parent sample	Field sampler	Blind ID - lab must not know it is a duplicate
Trip Blank	1 per VOC cooler	VOCs only	Laboratory	Never open in the field
Equipment Blank	1 per decontamination event	Same as project samples	Field sampler	Only for shared/non-dedicated equipment
Field Blank	1 per sampling event (if applicable)	Same as project samples	Field sampler	Assesses ambient contamination at sampling site
MS/MSD (Matrix Spike)	1 per 20 samples	As specified by lab method	Laboratory	Extra volume required - confirm with lab

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Chain of Custody for Environmental Samples