On-line solid–phase extraction using a C18 minicolumn coupled to a flow injection system for determination of caffeine in green and roasted coffee beans

Synthesized of a novel xanthate functionalized polypropylene as adsorbent for dispersive solid phase microextraction of caffeine using orbital shaker in mixed beverage matrices

A newly synthesized xanthate functionalized chlorinated polypropylene (PP-Xa) was used as adsorbent for the orbital shaker based on dispersive solid phase microextraction (OS-DSPME) of caffein from several tea, coffee, energy drink, coca-cola and chocolate samples using UV-vis. spectrophotometer. Synthesized PP-Xa was characterized using Fourier Transform Infrared spectroscopy (FTIR-ATR) and nuclear magnetic resonance spectroscopy (¹H NMR). Various parameters like pH, PP-Xa amount, extraction time, type of eluent and its volume were optimized. Linear range, detection limit (LOD), limit of quantification (LOQ), relative standard deviation (RSD), recovery values, and enrichment factor (EF) were found 90-1000 μgL^-1, 27.3 µg L^-1, 90 µg L^-1, 1.9-2.6%, 98 ± 2%, and 167, respectively. Adsorption capacity of PP-Xa was found 271.9 mg g^-1. Standard addition and reference method were used for confirm the accuracy of present method.

Simultaneous determination of flavonoids and anthraquinones in honey by using SPE-CE-LIF

Based on advantages of capillary electrophoresis (CE), a new solid-phase extraction (SPE) coupled with CE has been developed for preconcentration, enrichment and determination of anthraquinones and flavonoids (rutin, emodin, quercetin, 1,8-dihydroxyanthraquinone) in honey. The environmental-friendly chitin activated after an easy processing is selected as the adsorbent to enrich analytes. Then, chitin was filled into the filter as the solid phase. To improve the extraction effect, some key parameters of extraction were optimized. Under the optional extraction conditions, the chitin showed excellent adsorption capacity and selectivity over rutin, emodin, quercetin, and 1,8-dihydroxyanthraquinone, with enrichment factors reaching 5 folds. The CE coupled with fluorescence detection was used for the detection. Results prove the method is simple, fast, and highly sensitive, with the limit of detection (LOD) is 3.00-200.0 ng/mL; the recovery is 90.0-107.0%, and relative standard deviation of (RSD) is 1.8-8.3%.

Modified graphene-silica as a sorbent for in-tube solid-phase microextraction coupled to liquid chromatography-tandem mass spectrometry. Determination of xanthines in coffee beverages

Given the increasing need for analyzing natural or contaminating compounds in complex food matrices in a simple and automated way, coupling miniaturized sample preparation techniques with chromatographic systems have become a growing field of research. In this regard, given the low extraction efficiency of conventional sorbent phases, the development of materials with enhanced extraction capabilities is of particular interest. Here we present several synthesized graphene-based materials supported on aminopropyl silica as sorbents for the extraction of xanthines. The synthesized materials were characterized by infrared spectroscopy and scanning electron microscopy. Aminopropyl silica coated with graphene oxide and functionalized with octadecylsilane/end-capped (SiGOC18ecap) showed the best performance for xanthines extraction. Hence, this material was employed as an in-tube solid phase microextraction (in-tube SPME) device coupled online with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) and applied for the analysis of xanthines in roasted coffee samples. Extraction parameters and detection conditions were optimized. The method showed low limits of quantification (0.3-1.0 µg L^-1), precision as relative standard deviation (RSD) values lower than 10%, recoveries between 73 and 109%, and pre-concentration factors from 5.6 to 7.2. Caffeine was determined in all ground roasted and instant coffee samples, in a wide range (0.9 to 36.8 mg g^-1), and small amounts of theobromine and theophylline were also detected in some samples. This work demonstrated that functionalized graphene-based materials represent a promising new sorbent class for in-tube SPME, showing improved extraction capacity. The method was efficient, simple, and fast for the analysis of xanthines, demonstrating an excellent potential to be applied in other matrices.