Abstract
Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is the most commonly used method for sulfonamide determination. Its accuracy, however, can be affected by many factors. In this study, sulfadiazine (SDZ), sulfadimidine (SMZ), and sulfadimethoxine (SDM) in milk were selected to investigate an accurate determination method and the potential influencing factors in the use of ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Milk samples were extracted by 25 mL perchloric acid solution (pH = 2) and cleaned up using HLB solid-phase extraction (SPE) cartridges. Four kinds of filters, including PTFE, GHP, nylon, and glass fiber, were compared, and PTFE was selected since it had the best recoveries of target sulfonamides (SAs). Three quantitative methods, including external standard (ES), matrix matching (MM), and isotope dilution mass spectrometry (IDMS), were compared, among which IDMS exhibited the best accuracy. The matrix effect under different mobile phase compositions and of different sample matrices were evaluated and discussed. Ion suppression effects were observed during the determination of all SAs, which got stronger with the increase of the methanol composition percent in the mobile phase. After correction by IDMS, the matrix effect could be neglected. Matrix spiked recoveries at three spiked levels (1 μg/kg, 10 μg/kg, and 20 μg/kg) ranged from 96.8% to 103.8% by IDMS. The expanded relative uncertainties were in the range of 2.02% to 5.75%. The method exhibited wide application range, high accuracy, good stability, and high sensitivity.
Highlights
Sulfonamides (SAs) are a kind of generic, highly effective, low-toxicity, and low-cost antibacterial agents [1]. e use of SAs as antibacterial synergist can expand the scope and enhance the activity of antibacterial. erefore, SAs are widely used in milk production for the prevention and treatment of bacterial diseases
According to the European Union (EU) regulation, single SAs concentration in milk and meat should not exceed 25 μg/kg, and the total amount should not exceed 100 μg/kg [6]; China’s Ministry of Agriculture and Rural Affairs stipulates that the total concentration of SAs in milk should be lower than 100 ng/mL, and the maximum residue limits (MRL) of sulfamethazine is 25 μg/L [7]
TM UPLC CSH C18 column (100 × 3.0 mm, 1.7 μm) and XTerra MS C18 (100 × 2.1 mm, 3.5 μm) column were compared under the same experimental condition. e results showed that all compounds can be separated on both columns, and the target compounds had shorter retention time on XTerra MS C18 column
Summary
Sulfonamides (SAs) are a kind of generic, highly effective, low-toxicity, and low-cost antibacterial agents [1]. e use of SAs as antibacterial synergist can expand the scope and enhance the activity of antibacterial. erefore, SAs are widely used in milk production for the prevention and treatment of bacterial diseases. Erefore, SAs are widely used in milk production for the prevention and treatment of bacterial diseases. Due to the potential toxicity, excessive intake of SAs may lead to human diseases, such as urinary system damage, digestive disorders, vomiting diarrhea, hemolytic anemia, drug-resistant strains, human immunity reduction, and tumor tendency [2, 3]. Erefore, many countries and regions have issued regulations on maximum residue limits (MRL) for SAs in food and feed. It is stipulated in the International Codex Alimentarius. Commission (CAC) that the total amount of SAs in food and feed shall not exceed 100 μg/kg [4]. E United Nations Food and Agriculture Organization (FAO) stipulates a residue limit for SAs in animal food at 100 ng/mL [5].
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