提出了化妆品测定1,3-二羟甲基-5,5-二甲基乙内酰脲(DMDMH)的间接方法。样品用纳什试剂处理后于沸水浴加热20 min使甲醛衍生化,离心分离,移取上清液经C18固相萃取小柱纯化,所得洗脱液用反相高效液相色谱分析。用DAD检测器分别在波长210,410 nm处测定5,5-二甲基乙内酰脲(DMH)及甲醛。根据所得DMH量及甲醛总量可分别换算出DMDMH的量。用Kromasil C18色谱柱进行分离,以不同比例混合的乙腈及水混合溶液作为流动相进行梯度淋洗。DMH及甲醛的线性范围依次为2.8~280,0.11~22 mg·L-1,检出限(3S/N)为0.81,0.033 μg·g-1。以3种化妆品实样为基体做加标回收试验,测得回收率依次在93.4%~107.8%和97.9%~109.9%之间,相对标准偏差(n=5)依次在1.7%~7.3%和0.8%~2.3%之间。

An indirect method for determination of DMDMH in cosmetics was proposed. The sample was treated with Nash′s reagent and heated for 20 min in a boiling water bath to derivatize formaldehyde. The supernatant were taken after centrifugation and purified by passing through C18 SPE column. The eluate was used for determination of 5,5-dimethylhydantoin (DMH) and formaldehyde by RP-HPLC with DAD at 210 nm and 410 nm respectively. From the total amount of DMH and HCHO found, amount of DMDMH was calculated. The sample solution was separated by using Kromasil C18 column and acetonitrile-water mixtures with different proportions were used as mobile phase in gradient elution. Ranges of linearity found were between 2.8-280 mg·L-1 (for DMH) and between 0.11-22 mg·L-1 (for HCHO), with detection limits (3S/N) of 0.81 μg·g-1 and 0.033 μg·g-1 respectively. Recovery was tested by addition of standards to 3 substantial cosmetic samples, giving values of recovery in the ranges of 93.4%-107.8% (for DMH) and 97.9%-109.9% (for HCHO) with values of RSD′s (n=5) ranged from 1.7% to 7.3% and 0.8% to 2.3% respectively.