An estimated 500,000 individuals in the US, mostly
steroid-dependent asthmatics, suffer severe adverse reactions to
sulfites in foods, beverages, and
pharmaceutical products. In an attempt to understand the pathogenesis of
sulfite hypersensitivity, we have developed an assay for the determination of total serum
sulfite by utilizing: (a) reductive release of
serum protein-bound
sulfite; (b) derivatization of free
sulfite with
monobromobimane; (c) separation of
sulfite-bimane from
thiol-
bimanes by reversed-phase HPLC; and (d) quantitation of
sulfite-bimane by fluorescence detection. The detection limit of this assay was 0.44 mumol/L serum
sulfite. The intra- and interassay CVs for total serum
sulfite at 5.4 mumol/L were 8.1% and 22.0%, respectively. The standard addition method was used to determine total serum
sulfite in normal subjects. More than 70 samples were prepared in 2-3 h, followed by automated overnight analysis. The mean concentrations (+/- SD) of total serum
sulfite in female (n = 41) and male (n = 35) donors were 4.63 +/- 2.33 and 5.16 +/- 2.68 mumol/L, respectively (not statistically significant: P = 0.368). The combined mean concentration of total
sulfite in both sexes was 4.87 +/- 2.49 mumol/L. There was no correlation between total serum
sulfite and total serum
cysteine,
cysteinylglycine,
homocysteine, subject age, serum
cobalamin, or serum
folic acid. The reference range (mean +/- 2 SD) for total serum
sulfite in normal subjects is 0-9.85 mumol/L.