Analysis of forchlorfenuron and thidiazuron in fruits and vegetables by surface-enhanced Raman spectroscopy after selective solid-phase extraction with modified ß-cyclodextrin.

ß-Cyclodextrin and its derivatives can selectively bind to various organic molecules in its cavity and provide good applications in sample preparation. Surface-enhanced Raman spectroscopy is a sensitive technique and has received increasing attention in the last decade. Herein, 3,5-dimethyl phenyl carbamoylated ß-cyclodextrin bonded silica gel was used as a ssorbent in solid-phase extraction to selectively enrich forchlorfenuron and thidiazuron followed by determination with surface-enhanced Raman spectroscopy. It showed excellent selectivity for forchlorfenuron and thidiazuron and the adsorption capacities were 40.0 and 30.0 µg/g, respectively. A rapid and sensitive method based on the modified ß-cyclodextrin solid-phase extraction coupled with surface-enhanced Raman spectroscopy was developed. The linear ranges were 30.0-300.0 µg/L for forchlorfenuron and thidiazuron at 1005 and 640 cm(-1) , respectively. Both of the limits of detection were 15.0 µg/L, which were significantly lower than the maximum permitted by the National Standard. The recoveries of forchlorfenuron and thidiazuron were 78.9-87.9% for the spiked grape, kiwi, cucumber and tomato, with relative standard deviations of 8.1-13.2%. The results show that this method is sensitive, selective, and relatively time saving, and has great potential in the analysis of trace amounts of plant growth regulators in fruits and vegetables.

Rapid analysis of ractopamine in pig tissues by dummy-template imprinted solid-phase extraction coupling with surface-enhanced Raman spectroscopy.

Ritodrine has similar skeleton structure to ractopamine and it was selected as the dummy-template molecule to synthesize the molecular imprinted polymers (MIPs). The MIPs exhibited better selectivity to ractopamine than to the dummy-template molecule: the imprint factor for ractopamine was 8.9, while 7.6 for ritodrine. The MIPs were used as sorbents in solid-phase extraction for selective enrichment of ractopamine, and some key parameters were optimized. After that, a rapid surface-enhanced Raman spectroscopy method was developed for analysis of ractopamine and isoxuprine in pig tissue samples. Under the optimal conditions, good linearity was achieved in the range of 20.0-200.0 µg/L for ractopamine and isoxsuprine at 842 cm(-1) and 993 cm(-1), respectively. The limits of detection were 3.1-4.3 µg/L, which were lower than the maximum allowed by U. S. Food and Drug Administration. The recoveries of ractopamine and isoxsuprine were 72.4-79.7% and 71.0-78.2% for the spiked pork and pig liver, respectively, while the relative standard deviations ranging from 7.4% to 13.0%. The results suggest that the proposed method is sensitive and selective, and it has good potential on the quantitative analysis of trace amounts of ß-agonists in complex samples.

[Progress of sample preparation techniques in gas chromatographic analysis].

Gas chromatography (GC) is a widely used analytical technique in many fields. Sample preparation is very important in GC analysis due to its time consumed and deviations produced. In the present paper, the progress of some typical sample preparation techniques in gas chromatography, including purge and trap, solid phase extraction, solid phase microextraction, liquid phase microextraction, microwave assisted extraction, ultrasonic-assisted extraction, etc., are reviewed.