Development of a Liquid Chromatography–Tandem Mass Spectrometry Method for the Determination of Sulfite in Food

Abstract

Sulfites are widely used food preservatives that can cause severe reactions in sensitive individuals. As a result, the U.S. FDA requires that sulfites be listed on the label of any food product containing >10 mg/kg (ppm) sulfite (measured as sulfur dioxide). Currently, the optimized Monier-Williams (MW) method (AOAC Official Method 990.28) is the most common approach for determining sulfite concentrations in food samples. However, this method is time-consuming and lacks specificity in certain matrices. An improved rapid, sensitive, and selective method has been developed using electrospray ionization (ESI) high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the determination of sulfite in various food matrices. A total of 12 different types of foods were evaluated. These included dried fruits and vegetables, frozen seafood, sweeteners, and juices. The matrix is extracted with a buffered formaldehyde solution, converting free and reversibly bound sulfite to the stable formaldehyde adduct, hydroxymethylsulfonate (HMS). Extracts are prepared for injection using a C18 SPE cartridge to remove any lipophilic compounds. HMS is then separated from other matrix components using hydrophilic interaction chromatography (HILIC) and detected using multiple reaction monitoring (MRM). The method was validated at 5 concentrations in 12 food matrices. Accuracy data showed spiked recoveries ranging from 84 to 115% in representative foods. Six commercially available sulfited products were analyzed using the LC-MS/MS method, as well as the MW method, to determine if differences exist.

Comparison of multiple methods for the determination of sulphite in Allium and Brassica vegetables

“…The LC-MS/MS method had recoveries of 116% ± 1% and 107% ± 1% for roasted garlic and hummus, respectively. The recoveries of the LC-MS/MS samples were consistent with those observed previously in other non-problematic matrices such as apricot and white grape juice (Robbins et al 2015). The experimental conditions and solvents of the LC-MS/MS method are quite different from those of the Monier–Williams methods.…”

“…Sulphite concentrations were determined by LC-MS/MS using the method of Robbins et al (2015). Briefly, all free and bound sulphites were converted to a formaldehyde adduct, hydroxymethylsulphonate, by extraction of the food product with a buffered 0.2% formaldehyde solution.…”

“… g The white grape juice and dried apricot recovery was previously published (Robbins et al 2015) and is included for comparison between the problematic and the previously validated matrices. …”

“…Recently, an LC-MS/MS method for the detection of sulphites was published, but it was only validated in non-problematic matrices such as apricots and shrimp. The LOQs for this method in non-problematic matrices ranged from 0.12 to 0.75 ppm SO 2 depending on the matrix investigated (Robbins et al 2015). This method has not been tested with Allium and Brassica samples.…”

Scientific Opinion on the re‐evaluation of sulfur dioxide (E 220), sodium sulfite (E 221), sodium bisulfite (E 222), sodium metabisulfite (E 223), potassium metabisulfite (E 224), calcium sulfite (E 226), calcium bisulfite (E 227) and potassium bisulfite (E 228) as food additives

“…Liao et al (2013) presented a method for the determination of free sulfites in dried fruits by using anion exchange column and conductivity detection after an extraction with a 0.2 N sodium hydroxide aqueous solution. Robbins et al (2015) presented a selective method using electrospray ionisation and HPLC-tandem mass spectrometry (HPLC-MS/MS). A total of 12 different types of foods were evaluated.…”