Bench Boost by Inorganic Ventures

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This 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.

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Join 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.

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This 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.

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This 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.

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This 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.