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SIA API Introduction

What is Sequential Injection Analysis?

Sequential Injection Analysis (SIA) is an automated liquid handling technique that enables:

  • Precise volume control - Aspirate and dispense exact volumes
  • Automated sample preparation - Dilution, mixing, reagent addition
  • Reduced reagent consumption - Microliter-scale operations
  • High reproducibility - Computer-controlled operations

SIA System Components

1. Syringe Pump

  • Provides precise fluid movement
  • Typical sizes: 100-5000 µL
  • Bidirectional flow control
  • Variable speed operation

2. Multi-Position Valve

  • Selects between different fluid lines
  • Common configurations: 6, 8, 10 positions
  • Low dead volume
  • Fast switching

3. Holding Coil

  • Temporary storage for fluids
  • Enables complex fluid manipulations
  • Typical volume: 1-5 mL

4. Flow Lines

  • Connect valve ports to:
  • Sample containers
  • Reagent reservoirs
  • Waste
  • Analytical instruments

How SIA Works

graph LR
    A[Syringe Pump] --> B[Selection Valve]
    B --> C[Port 1: Waste]
    B --> D[Port 2: Air]
    B --> E[Port 3: DI Water]
    B --> F[Port 4: Sample]
    B --> G[Port 5: Reagent]
    B --> H[Port 6: To CE]

Basic operation sequence: 1. Valve selects source port 2. Syringe aspirates fluid 3. Valve switches to destination 4. Syringe dispenses fluid

SIA API Architecture

The SIA API provides three levels of control:

1. Low Level - Direct Device Control

# Direct syringe commands
syringe.aspirate(500)
syringe.dispense(250)

# Direct valve commands
valve.position(3)

2. Mid Level - Coordinated Operations

# Combined syringe and valve operations
valve.position(water_port)
syringe.aspirate(1000)
valve.position(output_port)
syringe.dispense(1000)

3. High Level - Complete Workflows

# Pre-built analytical workflows
workflow.continuous_fill(vial=15, volume=1500, solvent_port=5)
workflow.homogenize_sample(vial=15, speed=1000, time=30)

Key Features

Volume Tracking

The API automatically tracks fluid volumes to prevent overflow:

syringe = SyringeController(port="COM3", syringe_size=1000)
syringe.aspirate(600)  # Volume counter: 600 µL
syringe.dispense(200)  # Volume counter: 400 µL
syringe.aspirate(700)  # Error! Would exceed 1000 µL capacity

Safety Features

  • Automatic volume validation
  • Position limits checking
  • Serial communication error handling
  • Graceful error recovery

Flexible Configuration

  • Customizable port assignments
  • Variable flow rates
  • Configurable delays and timing
  • Modular workflow components

Supported Hardware

Syringe Pumps

  • Hamilton MVP series
  • Cavro XLP/XP pumps
  • Other pumps with compatible command set

Valve Selectors

  • VICI Valco selectors
  • Rheodyne selectors
  • Compatible multi-position valves

Communication

  • RS-232 serial interface
  • USB-to-serial adapters
  • Standard baud rates (9600, 19200)

When to Use SIA

SIA is ideal for:

✅ Automated sample preparation - Dilution series - Standard additions - Matrix matching - Sample cleanup

✅ Reagent addition - Derivatization - pH adjustment - Internal standard addition - Chemical reactions

✅ Sample introduction - Controlled injection volumes - Sample stacking - Zone focusing - Multi-segment injection

✅ System maintenance - Automated cleaning - Conditioning procedures - Waste management - System priming

Integration with CE

SIA enhances CE analysis by:

  1. Sample Preparation
  2. Automated dilution to analytical range
  3. Buffer matching
  4. Protein precipitation

  5. Filtration

  6. Standardization

  7. Internal standard addition
  8. Automated calibration curves

  9. Quality control samples

  10. Productivity

  11. Unattended operation
  12. Overnight sample preparation

  13. Reduced manual handling

  14. Precision

  15. Exact volume delivery
  16. Reproducible mixing
  17. Controlled timing

Basic Concepts

Flow Profiles

Different operations require different flow characteristics:

  • Fast transfer: 3000-5000 µL/min
  • Precise dispensing: 500-2000 µL/min
  • Gentle mixing: 100-1000 µL/min
  • Critical operations: 50-500 µL/min

Bubble Segmentation

Air segments prevent mixing between zones:

# Aspirate sequence with air segments
valve.position(air_port)
syringe.aspirate(20)    # Air bubble
valve.position(sample_port)
syringe.aspirate(100)   # Sample zone
valve.position(air_port)
syringe.aspirate(20)    # Air bubble

Continuous vs Batch Flow

Continuous Flow - Transfer line filled with liquid - Fast sequential dispensing - Same solvent for multiple vials

Batch Flow - Transfer line filled with air - Each dispensing is independent - Easy solvent changeover

Getting Started

  1. Initialize Devices 

    syringe = SyringeController(port="COM3", syringe_size=1000)
valve = ValveSelector(port="COM4", num_positions=8)

  2. Test Communication 

    syringe.initialize()
valve.position(1)

  3. Create Workflow 

    workflow = PreparedSIAMethods(ce_api, syringe, valve)

  4. Run Operations 

    workflow.system_initialization_and_cleaning()

Next Steps

Learn about Basic SIA Operations to start controlling your system.