Food Safety Department, Teagasc Food Research Centre, Ashtown, D15KN3K Dublin, Ireland.
Teagasc, Johnstown Castle, Co., Y35 Y521 Wexford, Ireland.
Molecules. 2021 May 13;26(10):2890. doi: 10.3390/molecules26102890.
N-(n-butyl) thiophosphoric triamide (NBPT) is a urease inhibitor utilised in urea-based fertilizers. In Ireland, fertilizer treated with NBPT is applied to pasture to mitigate both ammonia and nitrous oxide emissions, but concerns arise as to the potential for residues in milk products. A quick ultrafiltration extraction and ultra-high performance liquid chromatography coupled with mass spectrometry triple quadrupole (UHPLC-MS/MS) quantitation method was developed and validated in this study. The method was applied in the analysis of samples collected from a field study investigating potential transfer of NBPT residues into milk. NBPT and NBPTo residues, were extracted from fortified milk samples and analysed on a UHPLC-MS/MS with recoveries ranging from 74 to 114%. Validation of the UHPLC-MS/MS method at low (0.0020 mg kg) and high (0.0250 mg kg) concentration levels in line with SANTE/12682/2019 showed overall trueness in the range of 99 to 104% and precision between 1 and 10%, RSD for both compounds. The limit of quantitation (LOQ) was 0.0020 mg kg and other tested parameters (linearity, sensitivity, specificity, matrix effect, robustness, etc.) satisfied acceptance criteria. Stability assessment using spiked samples revealed the compounds were stable in raw and pasteurised milk for 4 weeks at -80 °C storage temperature. Maintaining samples at pH 8.5-9.0 further improved stability. Analysis of 516 milk samples from the field study found that NBPT and NBPTo concentrations were below the LOQ of 0.0020 mg kg, thus suggesting very low risk of residues occurring in the milk. The method developed is quick, robust, and sensitive. The method is deemed fit-for-purpose for the simultaneous determination of NBPT and NBPTo in milk.
N-(正丁基)硫代磷酰三酰胺 (NBPT) 是一种用于尿素基肥料的尿素酶抑制剂。在爱尔兰，用 NBPT 处理的肥料被施用于牧场，以减少氨和氧化亚氮的排放，但人们担心其在奶制品中的残留问题。本研究开发并验证了一种快速超滤提取和超高效液相色谱-串联质谱三重四极杆（UHPLC-MS/MS）定量分析方法。该方法应用于一项田间研究中采集的样品分析，该研究旨在调查 NBPT 残留进入牛奶的可能性。从添加 NBPT 的牛奶样品中提取 NBPT 和 NBPTo 残留，并在 UHPLC-MS/MS 上进行分析，回收率在 74%至 114%之间。根据 SANTE/12682/2019 的要求，在低（0.0020 mg kg）和高（0.0250 mg kg）浓度水平下对 UHPLC-MS/MS 方法进行验证，结果表明总体准确度在 99%至 104%范围内，精密度在 1%至 10%之间，两种化合物的 RSD 均为 1%。定量限（LOQ）为 0.0020 mg kg，其他测试参数（线性、灵敏度、特异性、基质效应、稳健性等）均符合验收标准。使用添加样品进行的稳定性评估表明，在 -80°C 的储存温度下，在原始和巴氏消毒牛奶中 4 周内，化合物是稳定的。将样品的 pH 值保持在 8.5-9.0 进一步提高了稳定性。对田间研究中采集的 516 份牛奶样品进行分析，发现 NBPT 和 NBPTo 浓度均低于 0.0020 mg kg 的 LOQ，因此表明牛奶中残留的风险非常低。所开发的方法快速、稳健且灵敏。该方法被认为适用于牛奶中 NBPT 和 NBPTo 的同时测定。
