Laboratory water analysis: which parameters should be monitored to assess water quality?

Water analysis is a cornerstone of public health protection, regulatory compliance and process optimisation. From drinking water to effluents, laboratories must quantify critical parameters (pH, chlorine, ammonium, nitrate/nitrite, phosphate, iron/manganese, COD…). Modern kits — photometric cuvette tests and visual test kits — deliver fast, reproducible and traceable measurements, both at the bench and in the field. Pre-dosed and aligned with standard methods, they reduce handling errors, analysis time and chemical waste.

What are the different types of water analysis tests and how do you choose the right one?

Two complementary families of tests. Cuvette photometric tests (LCK vials) use pre-dosed reagents in sealed cuvettes. After reaction — sometimes with hot digestion for COD, total phosphorus or total nitrogen — the reading is taken on the photometer, often via barcodes to avoid programming errors. Sensitive and traceable, they suit regulatory validation and complex matrices.

The visual kits (e.g., the Mcolorquant) rely on a comparator reading or on drop-by-drop titrations. Robust and simple, they are ideal for field routine, training or quick checks. Test strips round things out for instant screening (chlorine, hardness, nitrate, Mquant…), with more limited accuracy but a minimal cost per test.

On the chemistry side, reference reactions include: DPD for free/total chlorine, Griess for nitrite (and nitrate after reduction), molybdenum blue for phosphate, complexometry with EDTA for hardness, or dichromate oxidation for COD. The choice depends on the measuring range, potential interferences (e.g., chlorides for COD), the matrix (colour, turbidity), the limit of detection, ISO/EN requirements, cost, and safety and waste constraints.

Here is a comparative snapshot:

Type	Principle	Applications
Photometric cuvette tests	Pre-dosed reagents, photometer readout, with digestion options	Regulatory controls, difficult matrices, low uncertainty
Visual kits	Colour comparator / drop-by-drop titration	Field work, training, fast routine with good repeatability
Test strips	Instant colour reaction on a carrier	Screening, pre-tests before detailed analysis

Plan according to the parameters: compatible photometer, thermoreactor (COD, total P/N), pipettes, consumables and a waste collection stream. “Eco” versions reduce reagent volumes and simplify risk management without sacrificing precision.

In which sectors is water analysis used?

• Drinking water : free/total chlorine, ammonium, nitrite, aluminium, manganese to safeguard the distribution network.
• Wastewater : COD, BOD5, ammoniacal nitrogen, phosphates and nutrients for the control of treatment plants.
• Environment : rivers, aquifers, lakes - monitoring of quality (metals, nitrates, orthophosphate, silica).
• Food & beverage : process water, rinsing, disinfection (chlorine/ozone), CIP monitoring.
• Pharma/cosmetics : purified water, WFI, routine monitoring and batch release (conductivity, TOC where required, endotoxins via other methods).
• Industry : boilers, cooling towers (hardness, nitrite inhibitor, phosphonate), corrosion and scaling.
• Aquaculture/pools : chlorine, pH, ammonium, nitrite to support organism health and bather comfort.

The different types of water analysis tests available

Frequently asked questions about water analysis

How to choose between photometric and visual tests?
Go photometric if you need strong traceability and low LOQ values; visual tests are ideal for field work and rapid screening at lower cost.

Is a thermoreactor essential?
Yes for certain parameters (e.g. COD, total phosphorus/total nitrogen). For pH, chlorine, nitrite, hardness, etc., no digestion is required.

Which methods are recognised by the standards?
DPD for chlorine, Griess for nitrite/nitrate, molybdenum blue for phosphate, dichromate for COD. Check the kit’s ISO/EN compliance.

How to handle sample turbidity or colour?
Use a sample blank, dilute if needed, and filter to remove particulates. Sealed cuvettes limit absorbance bias.

And interferences, especially chlorides in COD?
Choose kits with suitable anti-interference reagents, follow the instructions for use, and dilute the sample if necessary to stay within range.

How to ensure result quality?
Calibrate/verify with standards, run internal quality controls, and record batch and expiry. Barcoded cuvettes reduce errors.

What’s the environmental impact of the tests?
Reagent volumes are low; segregate hazardous vials (e.g. COD) via a dedicated waste stream and prefer reduced-waste ranges where possible.