Laboratory test strips: which parameters can be checked quickly in the field or laboratory?

Versatile and ready to use, test strips deliver rapid results both in the field and in the lab. Whether for water testing (pH, chlorine, nitrates), oils (free fatty acids, peroxides), foods and allergens (lateral-flow immunoassays), milk (antibiotic residues) or biological analyses (urine test strips, rapid tests), they combine colourimetric chemistry with lateral flow to provide results in minutes. Readouts can be visual or via a reader for traceability and semi-quantitative results, with minimal sample preparation.

What are the different types of test strips?

Test strips fall into two main families: the colourimetric tests using reactive pads and the immunochromatographic (lateral flow) tests in strip or cassette format.

• Water analysis: pads impregnated with indicators measuring pH, alkalinity, hardness, free/total chlorine, nitrite, nitrate, etc. Visual readout against a colour scale or via a reflectometer for higher accuracy. Strengths: speed (10–60 s), low cost, no glassware required. Limits: subjective reading, semi-quantitative, possible interferences (colour/suspended matter).

• Oil analysis (food): strips for free fatty acids, peroxides or TPM (total polar materials), useful for monitoring frying oils. Measurement in a few minutes after cooling and homogenising the sample.

• Food analysis (excl. milk): rapid checks of chemical parameters (e.g. peroxides in fats, nitrites in brines) or screening for residues in aqueous extracts. Select a strip validated for the matrix (meat, plant, process water).

• Allergens: lateral flow tests targeting proteins (gluten, peanut, milk, egg, soya…). Extraction, application of the extract, migration and visual reading of a test/control line in 5–10 min. Choose according to LoD (limit of detection, ppm), extraction protocol and intended use (cleaning verification, ingredients, finished product).

• Milk analysis: screening for antibiotics (?-lactams, tetracyclines, sulfonamides…) by immunochromatography. Qualitative/threshold result in 5–8 min, suitable for intake checks.

• Biological and medical testing: urine test strips (pH, glucose, proteins, ketones, leukocytes, nitrites, blood…) and rapid tests. Check the regulatory status (CE-IVD) for the intended use.

• Cassettes for strips: housings that protect the strip and make sample application easier. Reduce contamination, improve readability and ergonomics.

Selection criteria: target parameter and matrix, limit of detection, qualitative vs semi-quantitative, time-to-result, need for a reader, presence of internal controls, storage conditions and fitness for use.

The comparative table below summarises the main types:

Type	Principle	Applications
Colourimetric strip	Chemical reaction with colour change	Water (pH, chlorine, nitrates), oils (FFA, peroxides)
Lateral flow (strip/cassette)	Immunochromatography with antibodies	Allergens, antibiotic residues, biological tests
Strip + reader	Standardised optical reading	Semi-quantification, traceability and inter-site comparability

In which fields are test strips used?

Test strips meet the needs of quality control laboratories and field teams when responsiveness is paramount.

• Life sciences: rapid urine and pH checks, buffer solution control, verification of rinses.
• Food industry: monitoring of frying oils, screening for allergens, checking brines and process waters.
• Dairy: rapid tests for antibiotics at milk intake.
• Environment/water: pH, chlorine, nitrates, nitrites, hardness in distribution networks, wastewater treatment plants, swimming pools.
• Pharma/cosmetics: CIP checks, purified water, pH of pilot batches.
• R&D/education: screening, demonstrations and training without heavy instrumentation.

They serve as screening prior to confirmatory analyses (HPLC, spectrometry), reducing turnaround times and costs.

The different types of test strips available

Frequently asked questions about test strips

What accuracy should you expect versus a benchtop instrument?
Readouts are qualitative or semi-quantitative. With a reader, the typical deviation is 5–20%. For critical decisions, confirm using a reference method.

How should the strips be stored?
Keep dry, bottle tightly closed with desiccant, at 2–30 °C. Avoid light/moisture. Record the opening date and observe the post-opening expiry.

Are they compatible with coloured or lipid-rich matrices?
Yes, but plan for dilution, filtration or dedicated extraction. Heavily loaded matrices can interfere; follow the supplied protocol for the target matrix.

Do I need a reader to use the results?
Visual reading is often sufficient. A reader is recommended for traceability, low concentrations and inter-operator harmonisation.

What waste and precautions after testing?
Single-use waste must be disposed of according to the matrix. In IVD, treat as potentially biological. Do not pour to drain; re-cap the vials.

What is the correct read time?
Respect the indicated window (e.g. 30–120 s in colorimetry, 5–10 min in lateral flow). Reading too early or too late skews interpretation.

What about the regulatory status of medical tests?
Check the CE-IVD marking and intended use. Some kits are RUO. Document internal controls and records for audit.