Flow Analysis with Spectrophotometric and Luminometric Detection

With the ever increasing number of samples to be assayed in agronomical laboratories and servicing stations, fertilizer and food industries, sugar factories, water treatment plants, biomedical laboratories, drug quality control, and environmental research, the interest for automated chemical analysis has been increasing.

In this context, flow analysis is very attractive, as they the flow-based procedures are characterized by enhanced analytical figures of merit. Moreover, the flow analysers do not usually require sophisticated and expensive instrumentation, are amenable to full automation and to miniaturization, and are well suited for in situ analyses.

The tendency to carry out traditional methods of analysis in the flow analyser has becoming more pronounced, especially in relation to large-scale routine analyses. The technology of solution handling has become more and more improved, leading to enhanced strategies for chemical assays. Consequently, different modalities of flow analysis (e.g. SFA, FIA, SIA) have been conceived, developed and applied to solve real problems. Most of the flow-based analytical procedures presently in use, however, do not exploit the full potential of flow analysis.

The main object of the book is then to provide a scientific basis and to familiarise a wide community of researchers, students, technicians, etc with the uses of flow analysis. Emphasis is given to spectrophotometric and luminometric detection, in relation to agronomical, geological, industrial, pharmaceutical and environmental applications.

The book includes historical and theoretical aspects, recent achievements in instrumentation, guidelines for methodology implementation, and applications. It serves also as an applications-oriented text book.

• Detailed historical and theoretical background
• Various modes of operation
• Spectrophotometric and luminometric detection
• Strategies for solution handling
• Large number of applications

Researchers, students, consultants and practitioners in flow analysis, spectrophotometry, luminescence, flow injection analysis, sequential injection analysis and segmented flow analysis.

1. Introduction

1.1. General

1.2. The advent of Flow Analysis

1.3. The development of Flow Analysis

1.4. Main features of Flow Analysis

1.4.1. Sample insertion

1.4.2. Sample dispersion

1.4.3. Reproducible timing

1.4.4. Other attractive features

Transient analytical signal

Low susceptibility to biased results

Improved system design

1. Aims and scope of the monograph

Appendix 1.1. Important monographs related to Flow Analysis

Appendix 1.2. Journal Special Issues dedicated to Conferences on Flow Analysis

2. Historical view

2.1. Early developments

2.2. Segmented flow analysis

2.3. Flow injection analysis

2.4. Sequential injection analysis

2.4.1. Bead injection analysis

2.4.2. Lab-on-valve

2.5. Multi-commuted flow analysis

2.5.1. Multi-syringe flow injection analysis

2.5.2. Multi-pumping flow analysis

2.6. Other flow systems

2.7. Commutation in flow analysis

2.8. Flow pattern

2.9. Instrument characteristics

2.10. Trends

3. Fundamentals

3.1. The flowing sample

3.1.1. Flow pattern

3.1.1.1. Flow regime

3.1.1.2. Composition of the flowing stream

Tandem stream

Mono-segmented stream

3.1.1.3. Temporal variations in flow rates

Constant flow

Pulsating flow

Sinusoidal flow

Reversed flow

Linearly-variable flow

Intermittent flow

Pulsed flow

3.1.1.4. Alterations to the flow pattern

3.1.2. Sample dispersion

3.1.2.1. Dispersion inside a tubular reactor

3.1.2.2. Dispersion inside a mixing chamber

Improved mixing conditions

High sample dispersion

Exponential dilution

Establishment of fluidized beads

Manifold components behaving as mixing chambers

3.1.2.3. Dispersion by confluent streams

3.1.2.4. Practical indices for expressing sample dispersion

The volumetric fraction.

Experimental determination

Practical situations

Worked examples

3.1.3. Visualisation of the dispersing sample zone

3.2. System configurations

3.2.1. Single-line flow systems

3.2.2. Confluence flow systems

3.3. The detector response

3.3.1. Flat peaks

3.3.2. Bell shaped peaks

3.3.2.1. Peak height

3.3.2.2. Peak area

3.3.2.3. Peak width

3.3.3. Gathering the calibration model

4. Interaction of radiation with the flowing sample

4.1. Fundamentals

4.1.1. UV-Visible spectrophotometry

4.1.1.1. Losses of radiation

Radiation losses at interfaces

Radiation losses at the cuvette walls

Radiation losses inside the sample

Compensation of radiation losses

4.1.1.2 The Lambert-Beer law

4.1.1.3. Practical aspects of the Lambert-Beer law

Concentration of the radiation absorbing species

Monochromaticity of the radiation

Sample homogeneity

Chemical deviations

Temperature

Stray radiation

4.1.1.4. Special strategies

Dual-wavelength spectrophotometry

Solid phase spectrophotometry

4.1.2. Turbidimetry

4.1.2.1. Losses of radiation

4.1.2.2. Relationship between turbidance and analyte concentration

4.1.2.3. Practical aspects

Characteristics of the particles

Monochromaticity of radiation

Sample uniformity

Chemical deviations (including co-precipitation)

Rate of turbidity formation

Stray radiation

4.1.2.4. Special strategies

4.1.2.5. Final remarks

4.1.3. Nephelometry

4.1.4. Fluorimetry and phosphorimetry

4.1.5. Chemiluminescence and bioluminescence

4.2. The Schlieren effect

4.2.1. Physical principles

4.2.2. Occurrence

4.2.3. The Schlieren effect in flow analysis

4.2.3.1. Historical testimonies

4.2.3.2. The two components of the Schlieren effect

Poor mixing conditions

Good mixing conditions

4.2.3.3. Applications

4.2.3.4. Emergence

Differences between sample and carrier solutions

Pulsed sample inlet into the flow cell

Pulsed addition of merging streams

Exploitation of intermittent streams

Addition / removal of manifold components

4.2.3.5. Minimizing the Schlieren effect

Improvement of system design

Subtraction of monitored signals

4.3. Presence of immiscible phases

5. Flow Analysers

5.1. The segmented flow analyser

5.1.1. Characteristics

5.1.2. Sample dispersion

5.1.3. Controlling sample dispersion

5.2. The flow injection analyser

5.2.1. Characteristics

5.2.2. Sample dispersion

5.2.3. Controlling sample dispersion

5.2.3.1. Dispersion parameters

Temperature

Sample viscosity

Diffusion coefficient

Composition of the sample and reagent solution

Others

5.2.3.2. Dispersion parameters – system geometry

Sample volume

Injection mode

Dimensions of the analytical path

Tubing inner diameter

Flow rate

Confluent stream additions

Site of confluence stream addition

Artefacts in the analytical path

5.3. The sequential injection analyser

5.3.1. Characteristics

5.3.2. Sample dispersion

5.3.3. Controlling sample dispersion

5.3.3.1. Large sample volume

5.3.3.2. Limited sample dispersion

5.4. The multi-commuted flow analyser

5.4.1. Characteristics

5.4.2. sample dispersion

5.4.3. Discretely actuated devices

5.4.3.1. Automated devices

5.4.3.2. Devices with feedback mechanisms

5.4.3.3.Trends

5.5. Other flow analysers

5.5.1. The mono-segmented flow analyser

5.5.2. The discontinuous flow analyser

5.3.3. The Lab-on-Valve and Lab-on-Chip flow analysers

5.6. Describing the flow analyser

5.6.1. Establishment of the flowing stream

5.6.2. Sample introduction

5.6.3. Manifold characteristics

5.6.4. Sample processing

5.6.5. Detection

5.6.6. Performance of the flow system

5.6.6.1. General figures of merit

Accuracy

Precision

Selectivity

Sensitivity

Detection limit

Dynamic range

5.6.6.2. Figure of merit specific to flow based procedures

Carryover

Sampling rate

Ruggedness

Portability

6. Instrumentation

6.1. Fluid propulsion

6.1.1. Peristaltic pumps

6.1.2. Syringe (piston) pumps

6.1.2.1. Use of large volume pistons (syringes)

6.1.2.2. Use of small volume pistons

6.1.3. Diaphragm pumps

6.1.3.1. Solenoid pumps

6.1.3.2. Piezoelectric pumps

6.1.4. Gas pressurized reservoirs

6.1.5. Osmotic pumps

6.1.6. Gravity

6.2. sample handling

6.2.1. Tubes

6.2.2. Sample introduction

6.2.2.1. Sampler

6.2.2.2. Time-based introduction

6.2.2.3. Loop-based introduction

6.2.2.4. Hydrodynamic injection

6.2.2.5. Nested injection

6.2.3. Reactors

6.2.3.1. Coiled reactors / mixing coils

6.2.3.2. Packed bed reactors

6.2.3.3. Single bead string reactor

6.2.3.4. Knitted (or knotted) reactors

6.2.3.5. Reactor-like artefacts

6.2.4. Accessories

6.2.4.1. Connectors

Connectors for linking tubes together

Connectors for linking manifold tubes with other components

6.2.4.2. Solution containers

6.3. Detection and data processing

6.3.1. Flow-cells

6.3.1.1. Classical and Z-shaped flow-cells

6.3.1.2. Spiral flow-cells

6.3.1.3. Long optical path length flow-cells

6.3.2. Detectors

6.3.3. System control, data acquisition and data treatment

6.4. Miniaturisation of the flow system

7. Special strategies for flow manipulation

7.1. Merging zones

7.1.1. Implementation

7.1.1.1. Merging zones relying on different convergent carrier streams

7.1.1.2. Merging zones relying on a single carrier stream

7.1.1.3. Merging zones relying on an intermittent stream

7.1.2. Applications

7.1.2.1. Reduction of reagent consumption

7.1.2.2. Matching the analytical signal with the dynamic concentration range

7.1.2.3. Single point determinations incorporating blank determinations

7.1.2.4. Speciation

7.1.2.5. Reducing undesirable adsorption processes

7.1.2.6. Sequential determinations

7.1.2.7. Standard addition method

7.2. Zone sampling

7.2.1. Implementation

7.2.2. Applications

7.2.2.1. High sample dispersion

7.2.2.2. Simultaneous determinations

7.2.2.3. Variable dispersion

7.2.2.4. Detailed study of dispersion

7.3. Stream splitting

7.3.1. Segmented flow analysis

7.3.2.Unsegmented flow analysis

7.3.2.1. Stream splitting / stream merging

Expansion of the dynamic concentration range

Differential kinetic analysis

Simultaneous determinations

7.3.2.2. Stream splitting without stream merging

7.3.3. Sample removal from the analytical path

7.4. Zone splitting

7.4.1. Implementation

7.4.2. Applications

7.5. Sample incubation: zone trapping (general) and sample stopping

7.6.Prior assay

7.7. Multi-detection (with a single detector)

8. Sample handling