The column oven temperature programs were 40 °C (4 min), 5 °C min−1 to 80 °C, 20 °C min−1 to 180 °C, and splitless mode was used. The analytical column was an Rtx-5MS. Carrier gas was helium at 1 mL min−1. The mass acquisition range was 35–400 m/z. The peaks were identified on the basis of their fragmentation patterns using the NIST Mass Spectral Search Program 05 (NIST, Washington, DC). The soft drinks were collected from supermarkets in Florianópolis (SC, Brazil). In this study several brands of soft drinks, flavours and types of packaging (PET and glass bottles, and cans) were taken into consideration. All samples were stored at 0 °C. SPME extraction was performed with carboxen–polidimetilsiloxano

(CAR–PDMS) Selleck GSK1349572 fibre. The fibre was conditioned at 300 °C for 1 h prior to use. Blank desorptions were periodically carried out. Samples (20 mL) were transferred into vials (40 mL, Supelco) which contained 20% (w/v) sodium chloride salt, 150 μL sodium hydroxide 6 mol L−1. Internal standard at 50 and 25 μg L−1 of, respectively,

INCB024360 cell line dichloromethane and diiodomethane were used. The incubation and extraction temperature was 30 °C. The samples were equilibrated for 8 min before the extraction step. The speed of the magnetic stirring was 1000 rpm. The fibre was immersed in the headspace of the sample for 15 min, immediately drawn back into the needle and transferred without delay (less than 5 s) into the injection port of the GC. A desorption time of 3 min at 280 °C was used in this study. All analysis was performed in triplicate. When a soft drink bottle is opened, the pressure is reduced to the atmospheric pressure, causing decomposition of the carbonic acid releasing CO2. To avoid this

problem, the addition of NaOH to the sample can significantly reduce the carbonic acid concentration Isotretinoin due to the formation of Na2CO3 and NaHCO3. The effect of CO2 on the extraction of THMs from soft drink was studied comparing the extraction efficiency of adding or not adding 150 μL of NaOH 6 mol L−1 to a 20 mL soft drink sample. CAR–PDMS fibre, extraction time of 10 min, extraction temperature at 20 °C and stirring magnetic speed of 500 rpm were used in this study. As can be seen from Fig. 1, the best extraction efficiency occurs with addition of NaOH 6 mol L−1, except for chloroform which is the more volatile of the target analytes. The improvement of the extraction efficiency for the other THMs was up to 35%. The analytes are released from the aqueous phase to the gas phase when the pressure in the headspace is closed to atmospheric pressure. In the case of the soft drink samples, the transfer of the analytes between the two phases occurs easily when the CO2 is not present at high levels in the small headspace volume. The appropriate choice of fibre is essential to the establishment of a sensitive method in SPME, and it is dependent on the chemical nature of compounds of interest (Cancho, Ventura, & Galceran, 2001).