Rapid quantitative determination of fat-soluble vitamins and coenzyme Q-10 in human serum by reversed phase ultra-high pressure liquid chromatography with UV detection.

We are presenting the first ultra-high pressure LC (UHPLC) method for rapid quantitative measurement of vitamin A, E (alpha- and gamma-tocopherol), beta-carotene and CoQ(10) from human serum. The chromatography was performed on Shield RP(18) UHPLC column with UV detection. The method was validated based on linearity, accuracy, matrix effects study, precision and stability.

Analysis of urinary aromatic acids by liquid chromatography tandem mass spectrometry.

The separation and detection of 11 urinary aromatic acids was developed using HPLC-MS/MS. The method features a simple sample preparation involving a single-step dilution with internal standard and a rapid 8 min chromatographic separation. The accuracy was evaluated by the recovery of known spikes between 87 and 110%.

A simple and cost effective method for the quantification of 8-hydroxy-2'-deoxyguanosine from urine using liquid chromatography tandem mass spectrometry.

A rapid and high-throughput method for the determination of urinary levels of the oxidative stress biomarker, 8-hydroxy-2'-deoxyguanosine (8-OH-dG), has been developed and validated using liquid chromatography combined with electrospray ionization tandem mass spectrometry (LC-MS/MS). The assay features a cheap and readily available non-isotopic internal standard, a single-step filtration sample preparation, and a total analysis time of 6 min including column re-equilibration. The method was validated based on linearity, accuracy (100-106%), precision (CV < 7%), sample preparation stability (< or =5%, 72 h).

Direct analysis of un-derivatized asymmetric dimethylarginine (ADMA) and L-arginine from plasma using mixed-mode ion-exchange liquid chromatography-tandem mass spectrometry.

A high-throughput analytical method was developed for the measurement of asymmetric dimethylarginine (ADMA) and L-arginine (ARG) from plasma using LC/MS/MS. The sample preparation was simple and only required microfiltration prior to analysis. ADMA and ARG were assayed using mixed-mode ion-exchange chromatography which allowed for the retention of the un-derivatized compounds.

A simple and selective method for the measurement of leucine and isoleucine from plasma using electrospray ionization tandem mass spectrometry.

An analytical method was developed for the rapid and accurate quantification of leucine (LEU) and isoleucine (ILE) from plasma using electrospray ionization tandem mass spectrometry (ESI-MS/MS). The two isomeric amino acids were selectively detected using fragment ions unique to each compound. As a result, the need for chromatographic separation was avoided allowing for faster analysis (3 min).

High performance liquid chromatography-tandem mass spectrometry (HPLC/MS/MS) assay for chiral separation of lactic acid enantiomers in urine using a teicoplanin based stationary phase.

A novel method for the separation and simultaneous determination of urinary D- and L-lactic acid enantiomers by high performance liquid chromatography-tandem mass spectrometry (HPLC/MS/MS) is presented. The chiral separation was optimized on a Chirobiotic teicoplanin aglyocone (TAG) column. Most interestingly, the addition of water in small volume fraction to the polar organic mobile phase was found to significantly improve the chromatography.

Quantification of urinary zwitterionic organic acids using weak-anion exchange chromatography with tandem MS detection.

A rapid and accurate quantitative method was developed and validated for the analysis of four urinary organic acids with nitrogen containing functional groups, formiminoglutamic acid (FIGLU), pyroglutamic acid (PYRGLU), 5-hydroxyindoleacetic acid (5-HIAA), and 2-methylhippuric acid (2-METHIP) by liquid chromatography tandem mass spectrometry (LC/MS/MS). The chromatography was developed using a weak anion-exchange amino column that provided mixed-mode retention of the analytes. The elution gradient relied on changes in mobile phase pH over a concave gradient, without the use of counter-ions or concentrated salt buffers.

Estrogen metabolism and the diet-cancer connection: rationale for assessing the ratio of urinary hydroxylated estrogen metabolites.

Estrogens are known for their proliferative effects on estrogen-sensitive tissues resulting in tumorigenesis. Results of experiments in multiple laboratories over the last 20 years have shown that a large part of the cancer-inducing effect of estrogen involves the formation of agonistic metabolites of estrogen, especially 16-alpha-hydroxyestrone. Other metabolites, such as 2-hydroxyestrone and 2-hydroxyestradiol, offer protection against the estrogen-agonist effects of 16-alpha-hydroxyestrone.