Detection of Sodium Formaldehyde Sulfoxylate

Introduction

Sodium formaldehyde sulfoxylate (also kown as sodium hydroxymethanesulphinate; a powerful carcinogen;Figure.1), used as a fluorescent whitening agent and industrial whitening agent, has been illegally used to whiten wheat foods. In 2001, the Chinese Ministry of Health issued two civil orders prohibiting the use of SFS in food. Both the International Agency for Research on Cancer and the U.S. Environmental Protection Agency have concluded that formaldehyde is probably carcinogenic to humans, but sodium formaldehyde sulfoxylate will not harm human health when ingested in small doses. However, when too much sodium formaldehyde sulfoxylate is ingested, it may cause health problems such as headaches, and even death.[1]

HPLC combined with online derivatization

The method for determining sodium formaldehyde sulfoxylate in food by HPLC combined with online derivatization was established. Formaldehyde released from the oxidation of sodium formaldehyde sulfoxylate with KIO₃ solution was extracted by water, which was extracted by acetonitrile and reacted efficiently with 2,4-dinitrophenylhydrazine in acetonitrile–acetic acid solution for 2 min. The formaldehyde derivative was separated on an Agilent C₁₈ chromatographic column with acetonitrile–water (65:35) as the mobile phase for elution, and then detected by DAD at the wavelength of 350 nm. Tests results showed that the mass concentration of formaldehyde had a good linear relationship with the chromatograph peak area in the range of 0.1–5.0 mg/L with the correlation coefficient (r²) of 0.999, and the detection limit was 0.4mg/kg. The recovery rates obtained by standard addition method were 89.84%–97.46%, and the relative standard deviations were 0.25%–0.43% (n=6). The method is simple with fast operation,good separation effect, it is suitable for daily analysis and testing of sodium formaldehyde sulfoxylate in foods.[2]

Indirectly calculated based on the formulae

The formaldehyde content of the 11 kinds of commercial wheaten food samples was determined by acetylacetone spectrophotometry in Zhaoyang district of Zhaotong city. These sodium formaldehyde  sulfoxylate content was indirectly calculated based on the formulae. The wheaten food samples examination shows that the lowest formaldehyde content was 0.0120 μ g/g, and the highest was 0.1628 μg/g, and the sodium formaldehyde sulfoxylate of the samples in content range 1.6465mg/kg to 8.3564mg/kg, they were lower than defined value by the state(10 mg/kg). The sodium formaldehyde sulfoxylate in these food were not detectable.The relative standard deviation of the formaldehyde determination results were 0.14%~0.81 % and recoveries were 91.54%~97.26%. It was accurate and reliable to get the experimental results by the experimental method and steel with high accuracy and precision.[3]

Redox reaction-based fluorescent detection

A fluorescent probe for the detection of sodium formaldehyde sulfoxylate has been developed in food samples. Because of the strong reducibility of sodium formaldehyde sulfoxylate, a redox reaction between sodium formaldehyde sulfoxylate and the oxidizing naphthalene-1,4-dione could smoothly happen. And the fluorescent 1,4-dihydroxynaphthalene can be formed via the redox reaction between naphthalene-1,4-dione and sodium formaldehyde sulfoxylate, realizing the fluorescence detection of sodium formaldehyde sulfoxylate. Naphthalene-1,4-dione, as a sodium formaldehyde sulfoxylate probe, exhibit more than 40 times of fluorescence enhancement upon the addition of sodium formaldehyde sulfoxylate with good selectivity. Therefore, a new quantitative detection method for sodium formaldehyde sulfoxylate has been established, and its application for the detection of sodium formaldehyde sulfoxylate in food samples has been successfully demonstrated.[4]

Ultrasonic extraction method

To study the rapid extraction method of sodium formaldehyde sulfoxylate from non fried flour products. The content of sodium formaldehyde sulfoxylate was determined by para-rosaniline hydrochloride colorimetric method. The results were compared with those of GB/T 21126-2007. The conditions for rapid ultrasonic extraction of sodium formaldehyde sulfoxylate from non fried flour products were as follows: ultrasonic power was 200 W, extraction temperature was 60°C, extraction time was 10 min. The average recovery rate of sodium formaldehyde sulfoxylate under optimal ultrasonic extraction conditions (91.5%) was similar to that of national standard extraction method (91.2%). Ultrasonic extraction method is simple,rapid, accurate and high recovery, and can be used as a rapid extraction method for the determination of sodium formaldehyde sulfoxylate in non fried flour products.[5]

References

1. Wang YU, Lv H, Lan J, et al. Detection of Sodium Formaldehyde Sulfoxylate, Aluminum, and Borate Compounds in Bread and Pasta Products Consumed by Residents in Jilin Province, China. J Food Prot. 2022;85(8):1142-1147. doi:10.4315/JFP-22-011

2. Chang HP,etal. Determination of sodium formaldehyde sulfoxylate in food by HPLC combined with online derivatization[J].Chemical analysis and meterage,2018,27(06):77-80. 

3. Gong JK,etal.Determination of Sodium Formaldehyde Sulfoxylate in Commercial Wheaten Food[J].Guangdong Chemical Industry,2019,46(04):153-155.

4. Ye QX,etal. Redox reaction-based fluorescent detection of sodium formaldehyde sulfoxylate (Rongalite)[J].Journal of Jiangxi University of Science and Technology,2020,41(03):39-43.DOI:10.13265/j.cnki.jxlgdxxb.2020.03.006.

5. Li LJ,etal.Study on Rapid Extraction Method of Sodium Formaldehyde Sulfoxylate from Non Fried Flour Products[J].China Food Safety Magazine,2023,(29):96-98+102.DOI:10.16043/j.cnki.cfs.2023.29.020.

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