Abstract:
2 g of the sheared cigarette tipping paper sample was extracted ultrasonically with 20 mL of water for 30 min. An aliquot of 8 mL of the solution was taken, and 100
μL of 200 mmol·L
-1 sodium diethyldithiocarbamate (chelating agent) solution was added for reaction at 45℃ for 10 min under the system acidity of pH 6.0. After reaction, 60
μL of n-dodecyl alcohol (extractant) and 100
μL of methanol (dispersant) were added. After vortex and centrifugation, the upper organic phase was taken and made its volume up to 0.5 mL with methanol, then filtered into chromatographic bottle for testing. ZORBAX SB-C
18 column was used as stationary phase, and a mixture of methanol and water with different volume ratios was used as mobile phase for gradient elution. The separated target compounds were detected by diode-array detector at 258 nm. The results showed that the linear ranges of standard curves of Cr
3+ and Cr
6+ were 2.00-100.00
μg·L
-1, with detection limits (3S/N) of 3, 6
μg·kg
-1, respectively. Test for recovery was made on the actual sample by standard addition method, giving results in the ranges of 90.7%-105% for Cr
3+ and 84.1%-106% for Cr
6+, and RSDs (
n=7) of the determined values were in the ranges of 4.2%-7.3% for Cr
3+ and 4.5%-7.6% for Cr
6+. The enrichment factors of Cr
3+ and C
6+ were 25.6 and 9.5, respectively. This method was applied to analysis of the 5 actual samples, and Cr
3+ and Cr
6+ were both detected in 4 samples, with the detection amounts of Cr
6+ higher than those of Cr
3+.