Heteroatom cobalt-based metal-organic framework and reduced graphene oxide nanocomposite for dispersive solid phase extraction of caffeine from exhaled breath condensate samples of premature infants prior to HPLC-PDA

•A heteroatom cobalt-based MOF and reduced GO nanocomposite was utilized in the DSPE procedure.•An extraction procedure was used to extract caffeine.•The method was applied to determine the analytes in EBC samples.•Premature infants EBC were analyzed by the developed method. A cobalt-based metal–organic framework and graphene oxide were combined to prepare a new nanocomposite for extracting of caffeine from exhaled breath condensate (EBC) samples. Dispersive micro solid phase extraction of caffeine was conducted using the nanocomposite as a sorbent by adding 10 mg of it to the sample solution and vortexing for 3 min. After extracting of the analyte, it was eluted using the mobile phase. The analyte was then analyzed using high performance liquid chromatography-photodiode array detector. Under optimal conditions, the limit of detection, limit of quantification, and linear range of the calibration curve were found to be 1.7, 5.9, and 10–500 µg/L, respectively. To assess the precision of the method, five replicates of standard solutions containing caffeine at two different concentration levels (50 and 100 µg/L) were tested. The relative standard deviations for intra- and inter-day precisions ranged from 4.3 to 6.8 %. The applicability of the method was demonstrated by analyzing the samples obtained from premature infants undergoing caffeine treatment and caffeine concentrations were 4.9 ± 0.6, 2.7 ± 0.2 µg/L in the EBC samples of who were under treatment by a 5-mg dose. Also, caffeine concentrations were 5.9 ± 0.3 and 18 ± 0.6 µg/L in the the infants who obtained the 10-mg and 25-mg doses, respectively. The results indicated a satisfactory, extraction recovery of 86 % showcasing the method’s reliability and effectiveness in analyzing real samples.