Abstract:
Mainstream cigarette smoke (MSS) contains many harmful and carcinogenic substances, which poses a great threat to human health. However, MSS is a very complex sample matrix, some of the compounds are low in content and difficult to be detected. Additionally, the strong signal response of nicotine in MSS can suppress the detection of other substances. As a new type of ambient ionization mass spectrometry (AIMS), direct analysis in real time mass spectrometry (DART-MS) can quickly analyze solid, liquid and gaseous samples under atmospheric pressure without or with little sample preparation. In this work, an efficient method for the analysis of complex cigarette MSS particulate matter was developed, where sample enrichment method of solid phase microextraction (SPME) was directly coupled to DART-MS detection. SPME has shown unique advantages in the pretreatment of complex matrix samples in many fields due to its advantages of low sample consumption, high extraction efficiency and simple operation. After sample extraction, the SPME probes were directly coupled to DART ion source without sample elution and other intermediate steps. The adsorbed compounds on SPME was thermally desorped and ionized under the heated streams of helium metastable plasma from DART ion source. With optimization, the SPME extraction time was selected as 20 min, the moving speed of the DART ion source rail was 0.2 mm/s, and the helium temperature was 350 ℃. Four different types of cigarette species were investigated by the developed SPME-DART-MS method, and the results were compared with traditional Dip-it sampling method using DART-MS. It was found that SPME enrichment can not only greatly improve the detection signal of multiple substances in complex samples, but also reduce the matrix effect of nicotine. SPME with different coatings have different extraction performance, where C18 coating exhibited better extraction capability than PDMS coating for MSS particulate matter. Moreover, DART ion source showed good desorption efficiency for compounds on SPME probe, which can achieve effective mass transfer from SPME probes to ion source. Overall, the direct combination of SPME and ambient ionization mass spectrometry, namely SPME-DART-MS analysis, has the advantages of simple operation, rapid analysis speed and high throughput without sample elution and tedious intermediate steps for complex sample system.