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.
Over fourteen years, urine tests from 380 people on probation (87% male, average age 30) showed that 2.7% of 13,500 individual analyses detected at least one of eight narcotic substances. Cannabis had the highest relapse prevalence at 3.7%, followed by opiates at 2.4%. Barbiturates, LSD, buprenorphine, and PCP were almost never found. Relapses were most common among 18- to 35-year-olds, and women violated court abstinence orders with amphetamines more often than men did. Relapse rates for cannabis, opiates, and cocaine fluctuated most over time. The authors suggest that narcotic use during probation is not rare and has received too little professional attention.