Pseudomonas aeruginosa is a gram-negative bacterium widely distributed in nature. As a common opportunistic pathogen [1,2], it can cause human and animal infections under certain circumstances. People with weak immune systems are more likely to have diseases, such as acute enteritis, meningitis, sepsis and skin inflammation [3,4]. At present, Pseudomonas aeruginosa has been a research hotspot at home and abroad [5,6], which is mainly concentrated in the fields of clinical medicine, basic medicine, biology and pharmacy [[7], [8], [9]]. In recent years, there have been many problems related to the pollution of Pseudomonas aeruginosa, especially the problem of packaging drinking water [[10], [11], [12]]. Moreover, the positive detection of Pseudomonas aeruginosa in cosmetics has been reported repeatedly [13,14]. At present, microbial culture is the main test method for Pseudomonas aeruginosa. It includes several steps, such as bacterial growth, isolation, purification and biochemical identification, which take a long time and may lead to missed detection. This has always been a difficult and painful point in the field of pathogen detection.

Like all other bacteria and fungi, Pseudomonas aeruginosa can absorb various external nutrients for metabolism, which can produce secondary metabolites [15] . These metabolites can be divided into antibiotics, hormones, alkaloids, toxins and vitamins according to different functions. These metabolites not only are biologically active, but also play important roles in maintaining the ecological adaptability of Pseudomonas aeruginosa [16]. They are important for Pseudomonas aeruginosa to survive and reproduce in complex environments. Given the important and complex relationship between microorganisms and metabolites, the study of Pseudomonas aeruginosa metabolites is particularly important.

At present, there are relatively few studies on the detection methods of metabolites for Pseudomonas aeruginosa. Jia Fei used a surface-enhanced Raman spectroscopy (SERS) biosensor of gold nanoparticles to detect pyocyanin in water [17] . Fatima AlZahra used cyclic voltammetry to selectively detect pyocyanin [18]. Olga Zukovskaja used a SERS-active silicon nanowire matrix to rapidly detect pyocyanin, a bacterial biomarker, in saliva [19]. Tanaka Yuki used a portable SERS sensor to simulate the detection of pyocyanin in wound fluid [20]. Schneider Sylvia used electrochemical sensing technology to detect pyocyanin (PYO), pseudomonas quinolone signal (PQS), 2-heptyl-4-hydroxyquinoline (HHQ) and 2-heptyl-4-hydroxyquinoline n-oxide (HQNO) [21]. However, these studies primarily focus on electrochemical or biosensing techniques, with a detection range of 0.5–100 μM. These methods suffer from low sensitivity, poor specificity and limited applicability. The target substances for research are few and the research objects are not fully covered. Moreover, the chemical structure of secondary metabolites is complex and variable with low content. Therefore, it is necessary to develop a sensitive, accurate, reliable and convenient method for the detection of Pseudomonas aeruginosa metabolites.

This study innovatively established a method for determining Pseudomonas aeruginosa metabolites via high performance liquid chromatography tandem triple quadrupole mass spectrometry (HPLC-MS/MS). 17 possible metabolites were selected for screening. Compared with the existing studies, this method has the advantages of high sensitivity, strong specificity, excellent selectivity, good accuracy and high detection efficiency. And it is easier to promote and apply in practice. Furthermore, the verified method was innovatively applied to the metabolic analysis of Pseudomonas aeruginosa to screen for possible characteristic biomarkers. It was also applied to assess the residual risk of Pseudomonas aeruginosa metabolites in cosmetics and explore their metabolic associations. It can be used as a new analytical technique for microbial metabolomics analysis and biological identification, which provides technical support for applied research on Pseudomonas aeruginosa in clinical and industrial fields.