Separation of Polar Compounds using Poly(Ethylene Oxide) Bonded Stationary Capillary Liquid Chromatography

Poly(ethylene oxide) (PEO) bonded stationary phase has been synthesized by a single and simple step reaction. Poly(ethylene glycol monomethyl ether p-toluene sulfonate) (tosylated-PEO, molecular weight 900, n ≈ 18) was chemically bonded to 3-aminopropyl silica (TSKgel NH2-60, 5 µm particle size, and 60 Å mean pore diameter). The prepared stationary phase was able to separate polar compounds such as phenolics and nucleobases in capillary liquid chromatography. The retention and separation of phenolics and nucleobases could be achieved under isocratic elution condition. Nucleobases such as thymine, adenine, uracil, uridine, cytidine and toluene and phenolics (phenol, pyrocatechol, pyrogallol) were baseline separated in less than 6 min using 98% acetonitrile and less than 7 minutes using 80% acetonitrile, respectively. We demonstrated that the retention of nucleobases as analyte decreased with decreasing eluent concentration. The retention of these polar compounds was believed to be based on dipole-dipole and/or hydrogen-bonding interactions.

Capillary Liquid Chromatography for the Determination of Terpenes in Botanical Dietary Supplements

Dietary supplements of botanical origin are increasingly consumed due to their content of plant constituents with potential benefits on health and wellness. Among those constituents, terpenes are gaining attention because of their diverse biological activities (anti-inflammatory, antibacterial, geroprotective, and others). While most of the existing analytical methods have focused on establishing the terpenic fingerprint of some plants, typically by gas chromatography, methods capable of quantifying representative terpenes in herbal preparations and dietary supplements with combined high sensitivity and precision, simplicity, and high throughput are still necessary. In this study, we have explored the utility of capillary liquid chromatography (CapLC) with diode array detection (DAD) for the determination of different terpenes, namely limonene, linalool, farnesene, α-pinene, and myrcene. An innovative method is proposed that can be applied to quantify the targets at concentration levels as low as 0.006 mg per gram of sample with satisfactory precision, and a total analysis time <30 min per sample. The reliability of the proposed method has been tested by analyzing different dietary supplements of botanical origin, namely three green coffee extract-based products, two fat burnings containing Citrus aurantium (bitter orange), and an herbal preparation containing lime and leaves of orange trees.

The Usefulness of Saliva in Therapeutic Drug Monitoring of Caffeine in Preterm Infants.

Aim To verify if the concentrations of caffeine in saliva are comparable to the serum concentrations in preterm infants treated with caffeine for apnoea of prematurity. Methods Prospective observational study. Eligible patients were newborn infants < 37 weeks of gestational age treated with oral or intravenous caffeine for apnoea of prematurity. Two paired samples of saliva-blood were collected per patient. Tube solid phase microextraction coupled on-line to capillary liquid chromatography with diode array detection were used for analysis. Results A total of 47 newborns with a median gestational age 28 [26–30] weeks and mean of 1.11 ± 0.4 kg of birth weight. Median postmenstrual age, when samples were collected, was 31 [29–33] weeks. Serum caffeine median levels of 19.30 µg/mL [1.9–53.90]and salivary caffeine median levels of 16.36 µg/mL [2.20–56.90] were obtained. There was a strong positive Pearson’s correlation between the two variables r = 0.83 (p < 0.001). Conclusion The measurement of caffeine salivary concentrations after intravenous or oral administration offers an alternative to serum caffeine monitoring in apnoea of prematurity.