Common Tips for Analyzing Low Concentrations

Send us Fan MailThis week on Bench Boost Mike shares practical tips for analyzing pharmaceutical samples at low concentrations for USP 232 elemental impurities, emphasizing that high dilution makes small contamination or carryover issues critical. He advises minimizing contamination through careful container selection (avoiding glass and using acid-leached LDPE or leached polypropylene), and outlines a typical leaching process using dilute nitric acid for seven days. He also stresses using high-purity acids (ppb/ppt grade) and method blanks to monitor impurities. For trace measurements, he recommends tightening calibration ranges with more points near the LOD/LOQ, managing washout by running blanks before/after calibration and throughout batches, using appropriate internal standards to correct drift or suppression, recalibrating about every 20 samples, and understanding signal-to-noise requirements for LOD and LOQ.