Matrix Effects of Urine Marker Substances in LC-MS/MS Analysis of Drug of Abuse.

Polyethylene glycol (PEG) molecules with 6 to 12 repeating units, used in the Ruma urine marker system, can suppress the signal of certain drugs during LC-MS/MS analysis, depending on their retention times. At a PEG concentration of 20 mcg/mL, the matrix effect fell below 60% for all drugs except nortilidine, and all drugs remained detectable. Quantification error was under 15% for drugs with deuterated internal standards and under 32% for those without. Sample preparation methods did not clearly reduce the effect, likely due to similar solubilities of PEGs and analytes.

Study at a glance

Abstract

Analysis of drug abuse is frequently performed using high-performance liquid chromatography with an MS/MS detector and electrospray ionization. In this context, matrix effects, like signal reduction by ion suppression of individual analytes, play an important role. In this study, the authors evaluated the matrix effect caused by polyethylene glycol (PEG) with chain lengths ranging from 6 to 12 repeating units in drug analysis by LC-MS/MS. Selected chain lengths were used in the Ruma urine marker system. Amphetamines, opiates, opioids, antidepressants, psychotics, benzodiazepines, z-substances, and individual drugs, including THCCOOH, cocaine, LSD, and some of their metabolites were investigated. The matrix effect was investigated at PEG concentrations of 500 mcg/mL and 20 mcg/mL. The effect of each PEG molecule was determined. Furthermore, the effects of different common sample preparations on the PEG matrix effects were evaluated. There was a strong correlation between the retention time of PEG and the drug that was ion-suppressed by PEG. The matrix effect decreased to the point where it was within an acceptable range at the lower PEG concentrations investigated in this study. Matrix effects were observed for drugs with approximately the same retention times as the individual PEGs. The influence of the different workup methods was not as clear, which may be because of the similar solubilities of the PEGs and some analytes. At low PEG concentrations, the matrix effect was always below 60%, except for nortilidine. All the drugs were detectable. The effect on quantification was less than 15% for substances with deuterated analytes as internal standards and less than 32% for analytes without their own internal standards.