pH and USP 791

Send us Fan MailIn part two of our PURE Laboratories collab Mike continues his conversation with Erik Miller and Dave Neville from Pure Laboratories, exploring what it takes to produce five-nine and six-nine purity materials. Learn about contamination control, sample preparation, ICP quality control, laboratory design, and the small details that make a big difference in ultra-trace elemental analysis.

Send us Fan MailIn this special episode of Bench Boost, the Inorganic Ventures podcast, host Mike Booth sits down with Erik Miller and Will Marble from Pure Laboratories to discuss the growing demand for ultra-high purity materials. They explore challenges surrounding raw material quality, rare earth supply, custom synthesis, and how material purity impacts advanced industries including semiconductors, energy storage, and aerospace.

Send us Fan MailThis week on Bench Boost Mike explains why sample container choice can significantly impact elemental analysis results through contamination, adsorption, precipitation, chemical attack, or evaporation. The differences in glass vs common plastics are reviewed in detail, and the episode concludes with a brief discussion on proper cleaning/leaching, and the practice using dedicated containers for ultra-trace work.

Send us Fan MailThis week on Bench Boost Mike explains two key ICP-OES/ICP-MS quality control samples: the Initial Calibration Verification (ICV) and Continuing Calibration Verification (CCV). The ICV is run after calibration and before samples to confirm the calibration worked. The CCV is run periodically during the batch to confirm the calibration remains valid as drift, clogging, cone buildup, washout, or other issues occur. This episode concludes with reviewing how to troubleshoot ICV or CCV failures. 

Send us Fan MailThis week Mike discusses elevated backgrounds in ICP-OES when analyzing high total dissolved solids (TDS) samples such as brines, digests, excipients, salts, and starting materials. TDS increases free electron density in the plasma, producing Bremsstrahlung (braking) radiation and recombination radiation, which raise a broad continuum background across the spectrum. The elevated background degrades signal-to-noise, increases blank standard deviation, and worsens detection limits, especially for elements with poor ICP-OES sensitivity. Mitigation approaches include dilution, matrix-matched calibration or standard additions when dilution isn’t feasible.

Send us Fan MailJoin Mike this week on Bench Boost as he explores the basics of conductivity measurements. We review the theory of how conductivity is dependent on ion concentration, charge, and mobility. He describes how contact probes work, emphasizing the cell constant and how proper probe selection to avoid poor sensitivity or signal saturation. Temperature is highlighted as a major variable, often ~2–3% per °C. Lastly we cover calibration using NIST-traceable KCl standards, and how calibrating near the sample range and controlling errors can lead to accurate and reliable data.

Send us Fan MailThis week on Bench Boost we discuss titration techniques based on USP 541 and the Inorganic Venture's Titration Tips and Tricks guide. Mike explains the difference between equivalence point and observed endpoint and how key performance factors can include using the correct glassware, appropriate techniques, and thorough cleaning of burettes. We also cover the correct way to read a meniscus, and how optimizing sample size can prevent poor replicate agreement and high result variability.

Send us Fan MailThis week on Bench Boost Mike explains why accurate pH measurement is more complex than it appears, highlighting the effects from temperature, ionic strength, calibration technique, probe condition, and sample chemistry. He reviews pH theory of hydrogen ion activity (not just concentration) and the logarithmic meaning of pH changes, then describes how a pH probe functions as an electrochemical cell. He details temperature impacts on solution pH and electrode response (Nernst slope), notes automatic temperature compensation limits, summarizes USP <791> calibration buffers and allowable uncertainty.

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.

Send us Fan MailThis week Mike and Ashley explain the J value used in pharmaceutical elemental impurity testing to relate typical ICP concentration units to permitted daily exposure (PDE) limits reported in micrograms per day under USP <232> and ICH Q3D. They describe how J value accounts for both sample dilution factor and maximum daily dose, making results comparable to PDE requirements. They recommend preparing method standards at PDE limits for the relevant administration route and diluting to match the J calculation for method validation.