Author: Mandel Scientific

How “Clean” Does My GC Tubing Need to Be?

cg_tubing_aluminumUsing clean, high-quality tubing is essential when setting up a new GC or when replumbing an existing gas delivery system, especially for carrier and detector gases.
“Clean” tubing often only means that it has been processed according to ASTM B280 or CGA G-4.1. However, in our experience, tubing prepared by these methods alone is not clean enough for chromatography applications. Residual drawing oils and other manufacturing artifacts may still be present and can easily contaminate an instrument after installation.

Check out Mandel’s line of GC tubing from Restek


LC-MS/MS Analysis of Urinary Free Cortisol and Cortisone without Matrix Interferences

Cortisol is a steroid hormone synthesized from cholesterol by a multienzyme cascade in the adrenal glands. It is the main glucocorticoid in humans and plays a critical role in glucose metabolism and immune response regulation. Cortisone, a downstream metabolite of cortisol, is measured in conjunction with cortisol to help diagnose various adrenocortical disorders, particularly hypercortisolism (Cushing syndrome). Urinary free cortisol and cortisone levels correlate well with bioactive plasma concentrations and, thus, are important biomarkers. LC-MS/MS is the preferred screening technique for these compounds because it is highly selective and helps eliminate analytical interferences that can affect immunoassay-based methods.


Try This Fast, Accurate LC-MS/MS Method for Folate Deficiency Biomarkers in Plasma

Folate deficiency is considered a risk factor for a wide range of human health problems, including neural tube defects in newborns, cardiovascular diseases, Alzheimer’s disease, and certain forms of cancer. Plasma levels of folic acid and its metabolites (5-formyl tetrahydrofolate and 5-methyltetrahydrofolic acid) are used as biomarkers to diagnose folate deficiency. However, LC-MS/MS methods for folate deficiency biomarkers in plasma can be very challenging because these small, polar compounds are not retained well on traditional reversed-phase LC columns. Retention can be improved using a HILIC method, but in this case, the column must provide strong enough retention to prevent coelution with the phospholipid components in the plasma sample matrix. Although a good sample preparation protocol will help, 100% removal of phospholipids is very difficult, and even low levels of phospholipids can interfere with target analytes, compromise quantitation, and contaminate the MS source.


Definitive EtG/EtS LC-MS/MS Analysis: A Rugged 4-Min Method for High-Throughput Labs

Methods for monitoring alcohol consumption biomarkers EtG and EtS are generally limited by poor retention and coelution with matrix interferences, as well as by long analysis times and short column lifetimes. The dilute-and-shoot EtG/EtS LC-MS/MS analysis developed here using the novel Raptor EtG/EtS column easily resolves EtG and EtS from matrix interferences, providing consistent, accurate results for high-throughput labs testing human urine samples for alcohol consumption.