On-line in-tube solid phase microextraction coupled to capillary liquid chromatography-diode array detection for the analysis of caffeine and its metabolites in small amounts of biological samples

Solid‐phase microextraction for the human biomonitoring of environmental chemicals: Current applications and future perspectives

“…Caffeine is one of the most consumed stimulants on an everyday basis via consumption of several beverages (coffee, tea, soft, and energy drinks). Further, caffeine has been used to treat apnea in preterm neonates [69]. Caffeine has three major metabolites, namely, paraxanthine, theobromine, and theophylline, although they were naturally present in cocoa products [69].…”

Bioanalytical HPLC Applications of In-Tube Solid Phase Microextraction: A Two-Decade Overview

“…Alternatively pure methanol [121,140,141], 1% acetic acid in acetonitrile [79], or mixtures of acetonitrile/methanol 90/10 v/v have been also utilized for this purpose [139]. Moreover, some approaches followed the direct dilution of plasma samples in 0.1 % v/v aqueous formic acid solution [37,46], 1 % v/v aqueous acetic acid solution [40,78,93,144], phosphate buffer [60,66,88,143], or a mixture of phosphate buffer/acetonitrile 90/10 v/v [62] and phosphate buffer/methanol 95/5 v/v [85]. An interesting exception against to "protein precipitation" approach is the utilization of RAM materials, which permits the direct injection of biological fluids [85,86].…”

“…Recently, a commercial capillary column has been utilized for in-tube SPME of caffeine and its metabolites in human serum, saliva, and urine [37]. A ZB-FFAP (100% nitroterephthalic-modified polyethylene glycol) commercial capillary column was utilized for the isolation of the analytes.…”

“…The selectivity and the sensitivity of the extraction process depend strongly on the coating of the capillary; therefore, it is critical to select the most appropriate extractive phase [ 27 ]. Typical examples of WCOT polar columns are 14% cyanopropylphenyl methyl polysiloxane [ 33 , 34 , 35 ], polyethylene glycol column [ 34 , 36 , 37 , 38 , 39 , 40 , 41 ], and 100% nitroterephthalic-modified polyethylene glycol [ 37 ]. Typical examples of nonpolar WCOT columns are polydimethyl siloxane [ 38 , 39 , 40 , 42 ], 95% polydimethyl siloxane, 5% polyphenyl siloxane [ 36 , 38 , 39 , 40 , 43 , 44 , 45 ], 35% diphenyl-65% polydimethylsiloxane [ 45 ], 20% diphenyl-80% polydimethylsiloxane [ 45 ], and (50%-phenyl)-methylpolysiloxane [ 46 ].…”

Extração líquido-líquido assistida por salting out da cafeína em amostras urina por cromatografia a gás

“…Diversas metodologias instrumentais já foram reportadas na literatura para a cafeína, e incluem principalmente as técnicas cromatográficas [10][11][12][13][14][15] , acopladas a diversos detectores, como o Massas (MS) e arranjo por diodos (DAD). Outras técnicas incluem espectroscopia de infravermelho, ultravioleta, eletroforese capilar e técnicas eletroanalíticas.…”