As a substance that is harmful to the human body, people have always been very cautious about the detection of formaldehyde. Especially for nappy in the hygiene products industry, a little carelessness will have an irreversible impact on the baby. However, due to the limitation of complex and diverse steps, traditional inspection methods cannot be used for batch inspection, which will hinder the output speed of products. Here are a few quick detection methods. The rapid detection method took only about 1/5 the time of the commonly used method; in addition, most nappy and sanitary napkin samples contained almost no formaldehyde. Therefore, it is necessary to promote rapid detection methods.
Condensation of formaldehyde with phloroglucinol under alkaline conditions produces an orange compound. The color of the reactant has a certain correlation with the formaldehyde content, so the formaldehyde content can be preliminarily judged by the color, or it can be tested with an ultraviolet spectrophotometer with a wavelength of 470 nm. The higher the concentration of NaOH contained in the solution, the faster the reaction of color development and fading, resulting in a higher absorbance value.
The chromatographic filter paper was soaked, and the soaking liquid was ethanol: aqueous solution of phloroglucinol and sodium hydroxide (ethanol: water = 1: 1) for 1 min, then taken out, and placed in a thermostat at 40° C. to dry for 1 hour. Formaldehyde test paper is usually stored in a closed dry container. In the quantitative test, take 10ml of soaking solution, add 0.5cm × 1cm paper, shake it to white, let it stand for 1min, and measure the absorbance value at a wavelength of 470nm with an ultraviolet spectrophotometer. The working curve ranged from 0.1 to 2.0 mg/l, the standard deviation was 0.15, and the correlation coefficient was ±0.56%. The method has high selectivity and no interference from metal ions and other aldehydes; the prepared paper can be stored in a closed container for 6 months, overcoming the short shelf life of liquid reagents.
The magenta-sulfurous acid solution is colorless, the formaldehyde reaction is rose red, and the acid condition is light blue, which can be used for quantitative colorimetric test. Although aldehydes can react with magenta-sulfurous acid, only the formaldehyde reaction product turns blue in a strong acid environment, which is its unique reaction and thus is not disturbed by other aldehydes during the measurement. The test wavelength is 570nm, the magenta-sulfurous acid content is 0.2~0.4ml, the light absorption value is stable, the operation is convenient, the sensitivity is high, the response is fast, and the disadvantage is that the color fades quickly and is easily affected by the ambient temperature.
Relevant literature shows that the detection limit of rapid detection method can meet the detection limit requirements of liquid chromatography.However, according to the specific analysis of specific problems, the application of rapid detection method is that the formaldehyde content in most diaper samples is very low, while for other special cases, it often requires conventional detection methods.