Water quality monitoring is an important part of ensuring water resources security and environmental protection. Different monitoring methods are suitable for different assays. Water quality monitoring is an important means to ensure water resources security and environmental protection, involving a variety of detection methods and technologies. In this paper, the gravimetric method, the volumetric method, the spectrophotometry, the fluorescence photometry, the atomic absorption method, the oxide and cold atomic absorption method, the atomic fluorescence method, the flame photometry, the electrode method, the ion chromatography, the gas chromatography, the liquid chromatography and the inductively coupled plasma emission spectrometry (ICP-AES) are introduced, and the applicable measurement items of each method are described in detail. These methods have their own capabilities in different application scenarios, which effectively improve the accuracy and reliability of water quality testing.
Gravimetric method
Gravimetric method is mainly used to determine suspended solids, filterable residues, salinity, oils, sulfur dioxide (SO4²⁻), chloride ions (Cl⁻), calcium ions (Ca²⁺), etc. in water.
Capacity method
The volumetric method is suitable for the determination of acidity, alkalinity, carbon dioxide (CO2), dissolved oxygen, total hardness, calcium ion (Ca²⁺), magnesium ion (Mg²⁺), ammonia nitrogen, chloride ion (Cl⁻), fluoride ion (F⁻), cyanide ion (CN⁻), sulfur dioxide (SO4²⁻), sulfur ion (S²⁻), chlorine (Cl2), chemical oxygen demand (COD), biochemical oxygen demand (BOD5), volatile phenols, etc.
Spectrophotometry
Spectrophotometry is widely used for the determination of a variety of metallic and non-metallic elements and compounds, including: silver (Ag), aluminum (Al), arsenic (As), beryllium (Be), bismuth (Bi), barium (Ba), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), mercury (Hg), manganese (Mn), nickel (Ni), lead (Pb), antimony (Sb), selenium (Se), thorium (Th), uranium (U), zinc (Zn), etc. It also includes ammonia nitrogen, nitrite nitrogen (NO2⁻-N), nitrate nitrogen (NO3⁻-N), Kjeldahl nitrogen, phosphate (PO4³⁻), fluoride ion (F⁻), chloride ion (Cl⁻), sulfide (S²⁻), sulfur dioxide (SO2), borate (BO3³⁻), silicate (SiO3²⁻), chlorine (Cl2), volatile phenol, formaldehyde, trichloroacetaldehyde, aniline, nitrobenzene and anionic detergents.
Fluorescence photometry
Fluorescence photometry is mainly used for the determination of selenium (Se), beryllium (Be), uranium (U), oils, and benzo[a]pyrene (BaP).
Atomic absorption method
Atomic absorption is commonly used for the determination of a variety of metallic elements, including: silver (Ag), aluminum (Al), barium (Ba), beryllium (Be), bismuth (Bi), calcium (Ca), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), mercury (Hg), potassium (K), sodium (Na), magnesium (Mg), manganese (Mn), nickel (Ni), lead (Pb), antimony (Sb), selenium (Se), tin (Sn), tellurium (Te), thallium (Tl), and zinc (Zn).
Oxide and cold atomic absorption methods
Oxide and cold atomic absorption methods are used for the determination of arsenic (As), antimony (Sb), bismuth (Bi), germanium (Ge), tin (Sn), lead (Pb), selenium (Se), tellurium (Te) and mercury (Hg).
Atomic fluorescence
The atomic fluorescence method is suitable for the determination of arsenic (As), antimony (Sb), bismuth (Bi), selenium (Se) and mercury (Hg).
flame photometry
Flame photometry is mainly used for the determination of lithium (Li), sodium (Na), potassium (K), strontium (Sr) and barium (Ba).
Electrode method
The electrode method is commonly used to determine redox potential (Eh), pH, dissolved oxygen, fluoride (F⁻), chloride (Cl⁻), cyanide (CN⁻), sulfide (S²⁻), nitrate (NO3⁻), potassium (K⁺), sodium (Na⁺) and ammonia (NH4⁺).
Ion chromatography
Ion chromatography is suitable for the determination of fluoride ion (F⁻), chloride ion (Cl⁻), bromine ion (Br⁻), nitrite (NO2⁻), nitrate (NO3⁻), sulfate (SO4²⁻), thiosulfate (S2O3²⁻), hydrogen phosphate (H2PO4⁻), potassium ion (K⁺), sodium ion (Na⁺) and ammonium ion (NH4⁺).
Gas chromatography
Gas chromatography is used for the determination of bromine (Br), selenium (Se), benzene, volatile halogenated hydrocarbons, chlorobenzene, hexahexah, DDT, organophosphorus pesticides, trichloroacetaldehyde, nitrobenzene and polychlorinated biphenyls.
Liquid chromatography
Liquid chromatography is mainly used for the determination of polycyclic aromatic hydrocarbons.
Inductively Coupled Plasma Optical Emission Spectrometry (ICP-AES)
ICP-AES is used for the simultaneous determination of matrix metal elements, polluting heavy metals, and multiple elements in substrates in water.
Through the introduction of this paper, it can be seen that the commonly used water quality monitoring methods have their own advantages in terms of diversity and accuracy. Gravimetric and volumetric methods are suitable for the determination of conventional physical and chemical indicators, while spectrophotometry and atomic absorption methods can effectively analyze a variety of metal elements. Emerging fluorescence photometry and ion chromatography have shown superior performance in the detection of trace substances. Gas chromatography and liquid chromatography are prominent in the analysis of organics. Inductively coupled plasma optical emission spectrometry (ICP-AES) is a powerful tool for monitoring heavy metal contamination due to its ability to determine multiple elements simultaneously. The comprehensive application of these methods provides a scientific basis for water quality monitoring and contributes to the sustainable development of environmental protection and resource management.
