Neutralex Aldehyde Test Kit

How to Use the Neutralex Aldehyde Test Kit for Aldehyde

The Tissue-Tek Formaldehyde Safety System (now called Neutralex) is a colorimetric aldehyde quantification assay kit that eliminates the upfront pH measurement1 based on 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole (Purpald or variant). It has been designed specifically to treat and dispose of formalin/aldehyde waste. It is stamped with the California Environmental Protection Agency’s seal to indicate non-hazardous drain-safe waste.

How to Use the Neutralex Aldehyde Test Kit

The kit is designed to test the pH and aldehyde content of spent waste in 20 seconds. Indicating that the product has been sufficiently neutralized to considered non-hazardous drain safe. The kit includes a test strip with the indicator dye impregnated thereon and a liquid solution of the indicator.

The test strips are impregnated with 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole (4-mercapto-4,6-dichlorophenol-indophenol) (DCIP or thionin) indicator dye. The indicator dye is a calorimetric color indicator that reacts with formaldehyde to produce a light blue color. The results are interpreted by the user after an elapsed time after the test strip is removed from the test solution.

The color result is compared to a standard reference color block to determine whether the formaldehyde concentration has been satisfactorily neutralized. This test method is simple. Easy to use and requires no additional instrumentation, other than the ability to read a color change. It is a good alternative to other calorimetric methods that require a separate preparation and analysis of the reagent solutions.

Preparation of the Test Solution

The test kit contains a sodium sulfite/sodium bisulfite neutralizer (NEUTRALEX(tm)) in the form of a white powder. This is diluted with water to prepare a solution having the desired concentration of free formaldehyde. To detected by the indicator dye. The indicator dye must impregnated on a test strip before it is dipped into the test solution. The strip is then inspected for color change within an elapsed time after it is removed from the solution and before any further action is taken.

The calorimetric tests that require an upfront pH measurement are difficult to use when dealing with alkaline solutions. Such as those containing formaldehyde. In such situations, the sulfite ion present in the solution will reduce indicator dyes with lower reduction potentials. Such as DCIP and thionin, more completely than those with higher reduction potentials, such as indigo carmine.

The NEUTRALEX aldehyde test kit uses a convenient test strip format that allows users to inspect their work for the presence of excess formaldehyde without having to measure the pH of the spent formalin waste. The test results can easily logged for reporting purposes.

Reading the Results

Aldehydes and ketones have similar chemical properties but differ in that the carbonyl group of an aldehyde is attached to the end carbon atom whereas a ketone has a carbonyl group on a central carbon atom. To distinguish between these groups there are a number of tests. Benedict’s reagent, for example, turns turquoise to yellow or orange when it reacts with reducing sugars that contain unbound aldehyde or ketone groups.

Another confirmatory test is the Silver Mirror test. This is a simple test that combines Tollens reagent with the Fehling solution and results in a silver-mirrored appearance on the sides of the glass tube when an aldehyde is present.

Finally, a pH test can used to detect the presence of aldehydes in a sample and also to verify that the waste being collected has been correctly treated and is non-hazardous drain safe. The pH strips are incorporated into the Neutralex Aldehyde Test Kit for quick and accurate testing.


The Neutralex aldehyde test kit provides consistent results and leverages a long 2-year shelf life for improved inventory management. It eliminates the upfront pH measurement1 and is easy to automate without a separation step. It is also more sensitive than many of the existing quantitative calorimetric tests for formaldehyde. More easily meets OSHA’s requirements for STEL/Ceiling monitoring than a diffusion monitor with DNPH chemistry.

The kit is designed for use with Neutralex franchise products. Which provide a safe and effective way to treat and dispose of aldehyde-contaminated waste. It is important to ensure that the waste has been completely neutralized before disposal and that results are logged for reporting purposes. This will help ensure that the waste is treated correctly and that it is non-hazardous drain safe.

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