Table 1.

Methods for iron monitoring in seawater.

Method	Measurement	Benefits	Drawbacks	Detection Limit
Atomic Absorption Spectrometry (AAS)	Laboratory	High sensitivity Short detection time	Pre-concentration of samples High sample volume Cumbersome equipment Expensive costs	50 pmol L−1 [80]
Inductively Coupled Plasma Mass Spectrometry (ICP-MS)	Laboratory	High sensitivity Short detection time Small sample volume	Pre-concentration of samples Cumbersome equipment Expensive costs	14 pmol L−1 [54]
Spectrophotometry	Laboratory	Iron speciation selectivity Simple procedure and data analysis Short detection time Inexpensive	Limited sensitivity Interference by coloured contaminants Requirement of stable iron complexes Pre-treatment of samples	1.9 nmol L−1 [81]
Voltammetry	Laboratory	High sensitivity Fast and simple procedure Iron speciation selectivity	Interference by other heavy metals Pre-treatment of samples Expensive maintenance costs	5 pmol L−1 [51]
Chemiluminescence	Laboratory	High sensitivity Iron speciation selectivity Short detection time Wide dynamic range Inexpensive	Interference by other chemical species Pre-treatment of samples Matrix removal requirement	40 pmol L−1 [60]
Flow Injection Analysis (FIA)	Onboard ship	High sensitivity Easy automatic operation Short detection time High sample throughput Low reagent consumption Minimizes the redox change and contamination	Expensive instrumentation Pre-treatment of samples Matrix removal requirement	25 pmol L−1 [82]
Long Path Length Liquid Waveguide Capillary Cell (LWCC)	Onboard ship	High sensitivity Easy automatic operation High sample throughput Iron speciation selectivity Small sample volume Background signal reduction	Expensive costs Sensitivity to impurities Pre-treatment of samples	0.1 nmol L−1 [63]
Reverse Flow Injection Analysis (rFIA)	Onboard ship	High sensitivity Easy automatic operation High sample throughput Fast and precise measurements Low reagents consumption Suitable for long-term shipboard use	Expensive instrumentation and maintenance costs Pre-treatment of samples Matrix removal requirement	0.4 nmol L−1 [64]
Voltammetric In Situ Profiling System (VIP)	In situ	Iron speciation selectivity Immersible in seawater Minimizes sample volume High spatial and temporal resolution	Expensive costs Long-term instability Low data accuracy for long-term operation	0.27 nmol L−1 [67]
Multi Physical Chemical Profiler (MPCP)	In situ	Iron speciation selectivity Immersible in seawater High spatial and temporal resolution Multiparameter measurements Easy automatic operation Minimize sample volume	Expensive costs Long-term instability Low data accuracy for long-term operation	0.2 nmol L−1 [67]
Whole-Cell Biosensor (WCB)	In situ	Bioavailable iron measurement High sensitivity Simple manipulation Inexpensive Potentially suitable for real-time measurements	Long-term maintenance Environmental containment Environmental interference Limited resolution Limited response time	40 pmol L−1 [34]
Multiple Light—Addressable Potentiometric Sensors (MLAPS)	In situ real-time	High sensitivity when coupled with voltammetry High specificity Fast detection speed Easy automatic operation Minimal sample requirement Multianalyte measurements	Expensive costs Limited measurement accuracy in complex environments Interference by multiple heavy metals Long-term stability	50 nmol L−1 [71]
Long Pathlength Absorbance Spectroscopy (LPAS)	In situ real-time	High sensitivity when coupled with LWCC Precision and Accuracy Minimal sample requirement Minimal interferences Easy automatic operation Suitable for deep sea monitoring	Expensive costs Long-term stability Frequent system maintenance	27.25 nmol L−1 [73]