MSDS authoring challenges: a comprehensive guide to completing physical and chemical properties for mixtures
Table of Contents
Introduction
Completing Section 9 of a Safety Data Sheet (SDS) for mixtures presents a unique challenge. While laboratory testing provides the most accurate data, it's often impractical or cost-prohibitive to test every property. This guide provides compliant alternatives and practical solutions.
Legal Requirements
According to REACH Annex II, Section 9 must include:
✓ Empirical data when available
✓ Physical and chemical properties with units
✓ Reference conditions
✓ Test methods or calculation approaches used
MSDS authoring : ECHA Compliance Hierarchy:
Laboratory test data
Literature data for identical mixtures
Validated calculation methods
Component-based estimates
MSDS authoring : ECHA Requirements vs. Calculation Methods for Section 9
According to Annex II of REACH (Version 4.0 December 2020), specifically point 0.2.3:
"Where reliable and relevant experimental data are available, that data shall be provided and take precedence over information obtained from models."
However, ECHA also acknowledges:
"Where experimental data are not available, the supplier shall consider whether reliable and relevant information obtained from models can be provided."
For mixtures: "If it is technically not possible to determine the property, this shall be indicated, and where available the lowest value for components shall be indicated."
Legal Compliance Analysis
Acceptable Approaches According to ECHA:
✓ Explicitly Allowed:
Use of calculated values when experimental data unavailable
Conservative estimates based on components
Ranges instead of exact values
Indication of estimation methods used
✓ Required Documentation:
Clear indication that values are calculated/estimated
Method used for determination
Reference conditions (temperature, pressure)
Measurement units
Example of Compliant Documentation:
Instead of just: "Flash point: 12°C" Write: "Flash point: ≤12°C (estimated, based on lowest component flash point)"
MSDS authoring : Best Practices for Compliance
1. Priority Order
Laboratory test data (when available)
Literature data for identical mixtures
Calculated values using validated methods
Conservative estimates based on components
2. Required Statements
For each property:
- Method of determination
- If calculated/estimated
- Uncertainty ranges where applicable
- Reference conditions
3. Documentation Example
Section 9.1: "The following data has been derived using calculation methods as specified in Article 9 of CLP Regulation (EC) No 1272/2008, where experimental data was not available:" [List properties with methods]
ECHA-Compliant Reporting Format
For Calculated Properties:
✓ Acceptable: "Boiling range: 78-85°C (estimated based on component boiling points)"
❌ Not Acceptable: "Boiling point: ~80°C" (Insufficient information)
Key ECHA Requirements for Specific Properties
Physical State
Must be determined at standard conditions
Visual observation acceptable
Flash Point
Testing required if classified as flammable
Conservative estimates acceptable for initial assessment
pH
Must indicate concentration if diluted
Estimation acceptable with proper documentation
MSDS authoring: Important Considerations
When Using Calculations:
Transparency
Clearly state calculation method
Document assumptions
Indicate limitations
Safety Margins
Use conservative values for safety-critical properties
Document worst-case scenarios
Updates
Update when new data becomes available
Review periodically
Documentation in MSDS:
Example format: "Note: Where experimental data is not available, values have been estimated based on: - Component data - Validated calculation methods - Conservative safety approaches All estimation methods comply with Article 9 of CLP Regulation"
Conclusion
The calculation methods discussed are compliant with ECHA requirements when:
Experimental data is not available
Methods are clearly documented
Conservative approaches are used for safety-critical properties
Limitations are acknowledged
Updates are made when new data becomes available
Property Analysis Framework
MSDS authoring - required Properties Checklist:
Physical Properties
Physical state
Color
Odor
Melting point/freezing point
Boiling point/range
Relative density
Bulk density (if applicable)
Particle characteristics (if applicable)
Chemical Properties
pH
Vapor pressure
Solubility
Partition coefficient
Flash point
Flammability
Explosive properties
Oxidizing properties
Additional Properties (when relevant)
Auto-ignition temperature
Decomposition temperature
Viscosity
Surface tension
Standard Reference Conditions
Unless specified otherwise:
Temperature: 20°C
Pressure: 101.3 kPa
Property Determination Methods
1. Physical State
Method: Visual observation Documentation required:
- State at 20°C and 101.3 kPa
- Any temperature-dependent changes
- Phase transition temperatures (if applicable)
2. pH
Methods available:
a) Direct measurement (aqueous solutions)
b) Calculation for acid/base mixtures
c) Estimation from similar formulations
Required documentation: - Concentration if diluted - Temperature of determination - Method used
3. Density
Methods:
a) Weighted average calculation
b) Direct measurement
c) Correlation methods
Formula for weighted average: ρmixture = Σ(ρi × wi) where: ρi = density of component i wi = weight fraction
4. Flash Point
Priority methods:
1. Laboratory testing (if classified as flammable)
2. Lowest component value
3. Calculation methods for similar chemicals Documentation:
- Method used
- Safety margins applied
- Limitations of approach
Calculation methods by property
A. Density Calculations
1. Weighted Average Method
Formula: ρmixture = Σ(ρi × wi)
Example: Three-component mixture:
- Ethanol (60%): 0.789 g/cm³
- Water (30%): 1.000 g/cm³
- Glycerol (10%): 1.261 g/cm³
Calculation: (0.789 × 0.60) + (1.000 × 0.30) + (1.261 × 0.10) = 0.473 + 0.300 + 0.126 = 0.899 g/cm³
Documentation: Density: 0.899 g/cm³ at 20°C (calculated) Method: Weighted average of components Uncertainty estimate: ±0.02 g/cm³
2. Limitations and Corrections
Volume contraction effects
Temperature dependence
Non-ideal mixing behavior
B. Vapor Pressure Calculations
1. Modified Raoult's Law Method
Formula:
Ptotal = Σ(Xi × Pi × γi)
Example:
Binary mixture:
- Component A (70 mol%): VP = 50 kPa
- Component B (30 mol%): VP = 30 kPa
Calculation: (0.70 × 50) + (0.30 × 30) = 35 + 9 = 44 kPa
Documentation: Vapor pressure: 44 kPa at 20°C (calculated)
Method: Modified Raoult's Law Assumptions: Ideal behavior
C. Boiling Point Estimation
1. Weighted Average Method
For ideal mixtures:
Tboiling = Σ(wi × Tbi)
Example:
Two-component mixture:
- Component A (80%): BP = 80°C
- Component B (20%): BP = 100°C
Calculation: (0.80 × 80) + (0.20 × 100) = 64 + 20 = 84°C
Documentation:
Boiling range: 80-100°C
Initial boiling point: Approximately 80°C
Method: Component analysis
D. Flash Point Determination
1. Conservative Approach
Method: Use lowest component flash point
Example:
Mixture components:
- Ethanol: 13°C
- Isopropanol: 12°C
- Propylene glycol: 99°C
Documented value: ≤12°C
Rationale: Most conservative value for safety
E. Viscosity Calculations
1. Refutas Method
Step 1:
Calculate VBI for each component VBI = 14.534 × ln[ln(ν + 0.8)] + 10.975
Step 2: Calculate mixture VBI VBImix = Σ(VBIi × Xi)
Step 3: Convert back to viscosity νmix = exp(exp((VBImix - 10.975)/14.534)) - 0.8
MSDS authoring -Practical examples : Implementation
Example: Solvent-Based Mixture
Composition:
Ethanol (70%)
Isopropanol (20%)
Water (10%)
Properties Calculation:
Physical State:
Direct observation: Liquid at 20°C
Density:
Component densities at 20°C:
- Ethanol: 0.789 g/cm³
- Isopropanol: 0.786 g/cm³
- Water: 0.998 g/cm³
Calculation: (0.789 × 0.70) + (0.786 × 0.20) + (0.998 × 0.10) = 0.552 + 0.157 + 0.100 = 0.809 g/cm³
Flash Point:
Component flash points:
- Ethanol: 13°C
- Isopropanol: 12°C
- Water: N/A Documented value: ≤12°C
MSDS authoring: Documentation Template
Section 9.1:
Physical and Chemical Properties Physical state: Liquid at 20°C (observed)
Color: Colorless (observed)
Odor: Characteristic alcohol odor (observed)
Boiling point: 78-82°C (calculated range)
Flash point: ≤12°C (based on components)
Density: 0.809 g/cm³ at 20°C (calculated)
pH: Not applicable (organic mixture)
Solubility: Fully miscible with water (based on components)
Methods and Notes:
- All calculations performed at 20°C and 101.3 kPa
- Conservative values used for safety-critical properties
- Calculations based on weighted averages where applicable
MSDS AUTHORING, CHAPTER 9.0 : DOCUMENTATION REQUIREMENTS AND CASE STUDIES
Documentation Requirements
Essential Documentation Elements
Value with Units
Reference Conditions
Method of Determination
Uncertainty Ranges
Limitations
Standard Documentation Format
[Property]: [Value] [Units] ([Method])
Temperature: [X]°C
Pressure: [Y] kPa
Limitations: [List any limitations]
MSDS authoring : Case Studies
Case Study 1: Water-Based Cleaning Solution
Composition:
Water (80%)
Ethanol (15%)
Propylene glycol (3%)
Surfactant (2%)
Complete Documentation Example:
SECTION 9: Physical and chemical properties
9.1 Information on basic physical and chemical properties
a) Physical state: Liquid (observed at 20°C)
b) Color: Clear, colorless (observed)
c) Odor: Slight alcohol odor (sensory evaluation)
d) Melting point/freezing point:
Value: Approximately 0°C
Method: Estimated from water content
Notes: May show supercooling
e) Boiling point:
Value: 90-100°C
Method: Calculated from components
Reference pressure: 101.3 kPa f) Flammability:
Classification: Not classified as flammable
Rationale: Flash point above 60°C
g) Flash point: Value: >65°C
Method: Calculated based on composition
Notes: Conservative estimate
h) pH:
Value: 7.2 ± 0.3
Temperature: 20°C
Method: Direct measurement
Concentration: As supplied
i) Density:
Value: 0.982 g/cm³ ± 0.005
Temperature: 20°C
Method: Weighted average calculation
Calculation shown below:
- Water (80%): 0.998 × 0.80 = 0.7984
- Ethanol (15%): 0.789 × 0.15 = 0.1184
- Propylene glycol (3%): 1.036 × 0.03 = 0.0311
- Surfactant (2%): 1.050 × 0.02 = 0.0210
Total = 0.982 g/cm³
Case Study 2: Solvent-Based Coating
Composition:
Xylene (45%)
Butyl acetate (30%)
Ethyl acetate (15%)
Resin solids (10%)
Property Calculations Example:
Flash Point Determination:
Component flash points:
- Xylene: 27°C -
Butyl acetate: 22°C
- Ethyl acetate: -4°C
- Resin: >100°C
Documented value: ≤-4°C
Rationale: Based on lowest component
Safety factor: Added margin of 2°C
MSDS authoring : Validation and Quality Control
Data Validation Checklist
□ All required properties addressed
□ Units consistent
□ Reference conditions specified
□ Methods documented
□ Uncertainties stated
□ Limitations noted
□ Safety margins applied where appropriate
Quality Control Steps
Cross-check calculations
Verify against similar mixtures
Review safety-critical properties
Document verification process
MSDS authoring : Special Cases
1. Temperature-Sensitive Properties
Document:
- Temperature dependence
- Valid range
- Critical temperatures
- Phase changes
2. Non-Ideal Mixtures
Additional considerations:
- Interaction effects
- Deviations from calculated values
- Special testing requirements
- Enhanced safety margins
MSDS authoring : Documentation Templates
Basic Template
[Property Name]
Value: [Numerical value with units]
Method: [Calculation/Measurement/Estimation]
Reference conditions: [Temperature and pressure]
Limitations: [Any limitations or assumptions]
Safety considerations: [If applicable]
Extended Template for Critical Properties
[Property Name]
Value: [Numerical value with units]
Method: [Detailed description]
Calculation: [Show working if applicable]
Validation: [Comparison with known data]
Safety margins: [Description and justification]
Limitations: [Detailed list]
Update requirements: [Conditions requiring reassessment]
MSDS AUTHORING: BEST PRACTICES, COMMON MISTAKES, AND TROUBLESHOOTING
Best Practices
1. General Principles
Documentation Excellence
✓ Clear method descriptions
✓ Traceable data sources
✓ Regular updates
✓ Version control
✓ Complete audit trail
Safety-First Approach
✓ Conservative estimates for critical properties
✓ Documented safety margins
✓ Clear limitation statements
✓ Worst-case scenario considerations
2. Property-Specific Best Practices
Flash Point
Always:
- Use lowest component value if untested
- Add safety margin
- Document calculation basis
- Consider mixture effects
Density
Best practice: - Calculate using multiple methods
- Verify against similar mixtures
- Document temperature effects
- Consider volume contraction
pH
Recommendations:
- Specify concentration
- Note temperature
- Consider buffer effects
- Document limitations
Common Mistakes and Solutions
1. Documentation Errors
Common Mistakes:
❌ Copying data without verification ❌ Missing reference conditions ❌ Inconsistent units ❌ Excessive precision
Solutions:
✓ Implement verification protocol ✓ Use standardized templates ✓ Include uncertainty ranges ✓ Apply appropriate rounding
2. Calculation Errors
Common Issues:
❌ Incorrect unit conversions ❌ Missing component data ❌ Wrong calculation methods ❌ Ignoring interactions
Solutions:
✓ Use conversion checklists ✓ Verify component data ✓ Document method selection ✓ Consider interaction effects
MSDS authoring: Troubleshooting Guide
1. Property Determination Issues
Problem: Inconsistent Results
Steps to resolve:
1. Check calculation methods
2. Verify input data
3. Consider interaction effects
4. Compare multiple approaches
Problem: Missing Component Data
Solutions:
1. Use structure-activity relationships
2. Apply read-across approaches
3. Use conservative estimates
4. Document limitations
2. Documentation Challenges
Challenge: Complex Mixtures
Approach:
1. Focus on key components
2. Use grouping strategies
3. Document assumptions
4. Apply conservative estimates
Challenge: Changing Compositions
Strategy:
1. Define composition ranges
2. Calculate property ranges
3. Document worst-case scenarios
4. Implement update triggers
MSDS authoring : Quality Assurance Framework
1. Review Process
Regular checks for:
- Data accuracy
- Calculation validity
- Documentation completeness
- Regulatory compliance
2. Update Triggers
Review and update when:
- Composition changes
- New data available
- Regulations change
- Errors identified
MSDS authoring: Practical Tools and Templates
1. Calculation Spreadsheet
Including:
- Property calculations
- Unit conversions
- Uncertainty estimates
- Validation checks
2. Documentation Checklist
□ All properties addressed
□ Methods documented
□ Units consistent
□ References cited
□ Limitations noted
□ Safety margins applied
□ Quality checks completed
MSDS authoring: Emergency Response Considerations
Critical Properties for Emergency Response
Priority properties:
1. Flash point 2. Boiling point 3. Vapor pressure 4. pH 5. Reactivity data
Regulatory Compliance Tips
Documentation Requirements
Ensure: 1. Compliance with REACH Annex II 2. GHS alignment 3. Local regulatory requirements 4. Industry standards
Final Implementation Strategy
Step-by-Step Approach
Gather component data
Select calculation methods
Perform calculations
Document results
Validate findings
Implement quality control
Maintain records
Schedule reviews
Example Final Documentation
SECTION 9: Physical and Chemical Properties
[Property]: [Value] [Units]
Method: [Calculation/measurement approach]
References: [Data sources]
Limitations: [Known limitations]
Safety considerations: [Critical information]
Update requirements: [Conditions for review]
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