水性涂料中游离甲醛含量的油基顶空-气相色谱-串联质谱测定法

Determination of free formaldehyde in water-based coatings by oil based headspace-gas chromatography-tandem mass spectrometry

目的开发油基顶空-气相色谱-串联质谱联用技术,测定水性涂料中游离甲醛的含量。方法N,N-二甲基甲酰胺经处理去除甲醛本底后作为样本分散提取剂,氘代甲醇作为内标,顶空-气相色谱-串联质谱法测定水性涂料中甲醛,内标法定量。结果甲醛在1~400 mg/L范围内,其峰面积与内标峰面积的比值与甲醛浓度线性关系良好,回归方程相关系数r=0.9994;甲醛在不同剂型涂料中低、中、高3个浓度水平的加标回收率在97.5%~101.8%之间,相对标准偏差在1.8%~2.6%之间;方法检出限为5 mg/kg,定量限为10 mg/kg。对市售6种不同类型水性涂料样本进行测定,其中4份样本检出甲醛,含量在21.5~41.8 mg/kg之间。结论本法采用N,N-二甲基甲酰胺作为分散剂,利用其对脂溶、水溶性化合物均有较强的溶解能力,达到对各种基质水性涂料样本较好的分散效果,利用其沸点高,饱和蒸气压低,有利于甲醛逸出,提高了方法的灵敏度。通过顶空净化和串联质谱测定有效降低了基质干扰,采用分子结构与甲醛接近的氘代甲醇作为内标,校正了样本基质对测定的影响,提高了定量的准确性,方法操作简单、抗干扰能力强、灵敏高、准确可靠。

Objective To develop an oil based headspace-gas chromatography-mass spectrometry technique for the determination of free formaldehyde in water-based coatings.Methods N,N-dimethylformamide was treated to remove formaldehyde background and used as a sample dispersant extraction agent,the deuterated methanol was used as an internal standard,and formaldehyde in water-based coatings was detected by headspace-gas chromatography-mass spectrometry.The internal standard method was used for the quantitative analysis.Results In the range of 1-400 mg/L,the ratio of peak area to internal standard peak area of formaldehyde had a good linear relationship with formaldehyde concentration,and the correlation coefficient(r)was 0.9994.The recoveries of formaldehyde at low,medium,and high concentration levels in different dosage forms of water-based coatings ranged from 97.5%to 101.8%,with a relative standard deviation between 1.8%and 2.6%.The detection limit was 5 mg/kg,and the quantitative limit was 10 mg/kg.Six different type of water-based coatings in the market were tested,among which formaldehyde was detected in four samples,with the content ranging from 21.5 to 41.8 mg/kg.Conclusions In this method,N,Ndimethylformamide is used as extractant and achieved good dispersion effect for various matrix water-based coating samples,because it has strong dissolving ability for both fat-soluble and water-soluble compounds.Furthermore,it has strong high boiling point and low saturated vapor pressure,which is beneficial to formaldehyde escaping from solution and improved the sensitivity of the method.The matrix interference is effectively reduced by headspace purification and tandem mass spectrometry.The deuterated methanol with molecular structure close to formaldehyde is used as internal standard,which corrects the influence of sample matrix and improved the quantitative accuracy.The method has advantages of simple operation,strong anti-interference ability,high sensitivity,accuracy and reliability.