LC-MS Urine Toxicology Solvent Transition Evaluation
Prepared by: Quasar Instruments Date: February 2026 Purpose This document summarizes the evaluation performed to support transitioning the methanol, water, and isopropanol used in a laboratory-developed LC–MS/MS urine toxicology analysis (71 analytes) to Birch Biotech solvents for routine testing. Performance before and after the solvent change was assessed using predefined QC acceptance criteria and multiple complementary approaches. These include quantitative accuracy and precision metrics (percent bias to QC targets and percent CV), longitudinal QC trending (Levey–Jennings review with application of Westgard rules), and distribution-based review (histogram analysis), along with system suitability monitoring (peak area and signal-to-noise) to confirm appropriate system performance and preserved analytical sensitivity. Proficiency testing and external laboratory comparison results were also reviewed to ensure continued acceptable performance, with the overall objective of confirming analytical equivalency and documenting that the solvent transition did not adversely impact QC stability, data integrity, or instrument performance. Executive Summary Across all analytes and QC levels, analytical accuracy (percent bias relative to QC targets) and precision (percent CV) remained within predefined acceptance criteria throughout the evaluation period. No meaningful differences in central tendency, variability, or distributional behavior were observed following the solvent transition. Levey–Jennings and histogram analyses demonstrated stable QC performance with no solvent-related trends, shifts, or increases in outlier behavior. System suitability assessments further confirmed instrument performance following the solvent switch. Peak area evaluations showed no evidence of increased background interference, contamination, or carryover. Signal-to-noise assessments demonstrated preserved analytical sensitivity with responses remaining well above established limits of detection and quantitation. Proficiency testing and alternate external performance evaluations supported these findings. All College of American Pathologists (CAP) proficiency testing events conducted before and after implementation of Birch Biotech solvents resulted in passing performance with no failures observed. For analytes not included in proficiency testing, alternate external laboratory comparisons and internal blind spike testing demonstrated acceptable agreement with expected values, indicating no adverse impact of the solvent transition on analytical performance. Overall, Birch Biotech solvents demonstrated analytical equivalency to the previously used solvent system, with no impact to accuracy, precision, quality control stability, or instrument performance. These results support the successful implementation and continued use of Birch Biotech solvents in routine LC–MS/MS urine toxicology testing. Solvent Significance Across the LC–MS Workflow Solvents are critical to LC–MS performance and data quality across all workflow stages. Their purity, composition, and consistency directly influence key analytical performance points, including: Sensitivity of Instrument (LOD and LOQ): High-purity solvents minimize instrument background noise and prevent trace contaminants from suppressing low-abundance analytes. Any contamination — whether from solvent impurities, system carryover, or storage conditions — can influence both the signal-to-noise ratio (S/N) and the achievable limits of detection (LOD) and quantitation (LOQ) of the analysis. Stability of the Instrument (Ion Suppression, Baseline Noise, and Carryover): Solvent consistency is critical for maintaining a stable chromatographic baseline and reproducible ionization performance. Trace metals, leachables, or particulate matter introduced through solvents or their storage containers can compromise instrument stability, resulting in ion suppression, signal drift, elevated baseline noise, or increased carryover. Reproducibility of Results (Precision Across QC Levels and Batches): Consistent solvent composition is essential for maintaining retention times, peak areas, and ion ratios across multiple analytical runs. Variability in solvent quality or the introduction of contamination can lead to shifts in chromatographic performance or response factors, affecting intra- and inter-batch precision. Reliable solvent performance ensures that quality control (QC) materials and patient samples produce consistent results over time. Because solvents play a direct and multifactorial role in LC–MS/MS performance, changes in solvent source or manufacturer can significantly affect analytical sensitivity, stability, and reproducibility. Solvent Use in Standards, Sample Preparation, and Instrument Operation and Maintenance In this urine testing workflow, methanol, water, and isopropanol are used throughout multiple stages of sample preparation and LC–MS/MS analysis. The following table summarizes where each solvent is used and how frequently it appears across standard preparation, sample processing, instrument operation, and maintenance. Materials Traceability and Analytes Evaluated To ensure material traceability and transparency, the solvent part numbers and lot numbers used during the post-transition period, along with the analytes evaluated as part of this study, are documented below. Birch Biotech Part Numbers Isopropanol: 1934-5 Methanol: 1935-5 Water: 1939-5 Birch Biotech Lot Numbers Isopropanol: O3L109, O3L109, O3L109, O3L109, O3L109, O3L109, O3L109, O3L109, NG7910, NG7910, NG7910, O3L109, O3L109, O3L109, O3L109, O3L109, NG7916, O3L109 Methanol: O1M207, O1M207, O1M207, O1M207, O1M207, O1M207, O1M207, O1M207, O1M207, O1M207, O1M207, O1M207, O1M207, O1M207 Water: NCF106, NCF106, NCF106, NCF106, NCF106, NCF106, NCF106, NCF106, NCF106, NA7306, NA7306, NA7306, NA7306, NA7306, NA7306, NA7306, NA7306, NA7306, NA7306, O41112, O41112, O41112, O41112, O41112, O41112, O41112, O41112, O41112, O19110, O19110, O19110, O41112, O41112, O41112, O41112, O41112, O41112, O41112, O41112, O41112, O41112, O5R105, O5R105, O19110, O19110 Methodology The methodology described below outlines the analytical approaches used to assess the solvent transition and to support the conclusions of this evaluation. Quantitative Performance Metrics Standardized performance metrics were calculated for each analyte and QC level relative to established target concentrations to evaluate analytical accuracy and precision. Metrics were calculated for both pre- and post-switch datasets, with pre-switch QC data provided for contextual overview. Pre-switch QC data is included to provide representative context for expected LC–MS analysis averages and variability. Accuracy assessments are based on deviation from established target concentrations, not direct comparison between pre- and post-switch datasets. Quantitative Performance Metrics: Accuracy Analytical accuracy was assessed using percent bias relative to the established QC target concentration for each analyte and QC level, calculated as follows: % Bias (Accuracy) = ((Observed Mean − Target Value) / Target Value) × 100 This metric provides a normalized measure of how closely observed QC results align with expected target concentrations and enables direct comparison across analytes and QC levels. Accuracy was considered acceptable when percent bias remained within ±15 percent of the target concentration across all QC levels. Quantitative Performance Metrics: Precision (%CV) Analytical precision was assessed using percent coefficient of variation (%CV), calculated for each analyte and QC level as follows: %CV = (Standard Deviation / Mean) × 100 This metric provides a normalized measure of measurement reproducibility and allows direct comparison of precision across analytes and concentration levels. Precision was considered acceptable when absolute %CV values remained ≤15% across QC levels. Levey–Jennings Analysis A Levey–Jennings chart is a standard quality control tool used in analytical laboratories to monitor analytical performance over time. For this panel, which includes 71 analytes, daily QC results are plotted against the established target values and control limits (typically ±1, ±2, and ±3 standard deviations). This lab's laboratory information system (LIS) defines ±3 SD at ±20%. This visualization supports application of Westgard multirule criteria to detect both random and systematic analytical error. This visualization allows clear identification of key performance patterns, including: Trends (gradual drift upward or downward) Shifts (sudden change in mean) Random error or increased variability Out-of-control events, where results fall outside ±2 Long-term stability of the analytical method The Levey–Jennings chart compares Pre-Birch Biotech QC results with Birch Biotech results over the same QC target concentration for low, medium, and high QCs. Key Components of the Levey–Jennings Chart Pre-Birch (Maroon Data Points): Daily QC points six months prior to switching solvents (November 2023–April 2024) plotted in order of occurrence. BirchBio (Green Data Points): Daily QC points six months post switching solvents (June 2024–November 2024) plotted in order of occurrence. Target Value: The expected QC concentration, shown as the red central horizontal line. Control Limits: Dashed horizontal lines at ±2 SD from the target as assigned by the LIS. Histogram Analysis The QC data was also evaluated using histogram to assess the distribution of results and to verify whether QC performance follows a normal (Gaussian) distribution around the target mean. The histogram provides additional insight into: Central tendency (how closely the results cluster around the expected value) Spread/variability of QC data Skewness or asymmetry, which may indicate bias or non-normal behavior Presence of outlier populations that may not be visible in a time-series plot The histogram helps confirm whether the analysis's QC distribution is consistent with expected analytical behavior and whether variability differs significantly between pre- and post-Birch operational periods. Key Components of the Histogram Chart Pre-Birch (Maroon Bars): Represents the distribution of QC results collected during the six months prior to switching solvents (November 2023–April 2024). Birch Biotech (Green Bars): Represents the distribution of QC results collected during the six months after switching solvents (June 2024–November 2024). Bin Ranges: X-axis intervals that group results by concentration. Frequency: Y-axis values showing how many QC results fall into each concentration bin. Central Tendency: Shows how closely the results cluster around the target. Distribution Spread: Indicates measurement variability — narrow, centered bars reflect higher precision; wider or shifted bars indicate greater variability or bias. System Suitability As part of the laboratory's in-house quality system, System Suitability functions as an early detection mechanism for suboptimal instrument performance and supports application-specific preventive maintenance through routine and longitudinal performance monitoring. System Suitability is a pre-analytical performance check used to confirm that the LC–MS/MS system is operating at a level consistent with its validated state prior to patient sample analysis. In this methodology, System Suitability is applied to monitor signal-to-noise (S/N) and peak area performance using low-level calibrator injections, providing assurance of adequate analytical sensitivity and background cleanliness before batch submission. System Suitability: Peak Area Assessment System suitability data collected in November 2024 were evaluated to demonstrate that the solvent transition did not introduce contamination or background interference impacting LC–MS performance. Peak area in warmup (Double Blank) injections was compared to the average LLOQ (50% calibrator) response for each batch, with acceptance defined as <25% of the LLOQ average area for all analytes. System Suitability: Signal-to-Noise Assessment System suitability was evaluated using data from the first and last run day of each month from June 2024 through November 2024 to confirm that the solvent transition did not adversely impact analytical sensitivity or increase background noise affecting LC–MS performance. Signal-to-noise ratios were assessed using LLOQ (50% calibrator) system suitability injections, with acceptance defined as an average S/N ratio greater than 10 for all analytes. Proficiency Testing and Alternate Proficiency Testing Proficiency testing (PT) and external laboratory comparison data were reviewed for periods before and after implementation of Birch Biotech solvents. PT events included the following program types: DMPM-B, ETB-B, UT-B, and UT-C. PT data were evaluated from events conducted in August, September, and November 2023 (pre-transition) and August, September, and November 2024 (post-transition). DMPM Drug Monitoring for Pain Management ETB Ethanol Biomarkers UT Urine Toxicology For analytes not included in College of American Pathologists (CAP) proficiency testing, alternate external comparisons were conducted using two independent laboratories, as documented in this report. For three analytes not covered by PT or external comparison, internal verification was performed using independently prepared blind spiked samples analyzed under routine workflows, with theoretical targets provided post-analysis for comparison. QC Acceptance and Data Exclusion Criteria Data inclusion and exclusion followed predefined daily QC batch acceptance criteria established during a multi-month validation study approved by the Laboratory Director and Technical Supervisor. Batch acceptance required ≥66% of QC results to meet specification. Individual QC failures within an otherwise acceptable batch were documented in the daily QC log. No post hoc statistical rules were applied. Across 258 operational days, QC failures occurred on 14 days (5.4%), involving 10 of 71 analytes. Results associated with failed QC events were excluded prior to analysis; no additional data points were removed. QC failures were intermittent, analyte-specific, showed no trend, and occurred both before and after the solvent transition. No full batch failures occurred during the post-transition period beginning June 2024. QC failures are expected in LC–MS workflows due to instrument sensitivity and method complexity. Exclusion of isolated, non-systemic QC events from Levey–Jennings analysis ensures performance trends are evaluated using data generated under acceptable QC conditions. Timeline of Monthly QC Performance: Pass (Black) vs. Fail (Red) Months shown in red reflect isolated QC failure events occurring on one or more run days. These failures were event-based and do not represent sustained or month-long QC nonconformance. Monthly QC Performance Summary and Failure Frequency Results The results presented below summarize the findings of the solvent transition assessment using the methodologies described above. Quantitative Performance Metrics The following results present analytical accuracy and precision metrics for each analyte relative to established target concentrations. Percent coefficient of variation (%CV) and percent bias (accuracy) were ≤15% for all analytes, indicating no adverse impact to the monitored QCs associated with the solvent switch. Low QC — Pre Switch Low QC — Post Switch Medium QC — Pre Switch Medium QC — Post Switch High QC — Pre Switch High QC — Post Switch Levey–Jennings Analysis Levey–Jennings charts were reviewed for all 71 analytes across Low, Medium, and High QC levels to assess analysis performance before and after the solvent transition. Pre-Birch QC results (November 2023–April 2024) and Birch QC results (June 2024–November 2024) were plotted against the same established QC target means and control limits. Across all QC levels and analytes, the Levey–Jennings charts demonstrated comparable performance between the pre- and post-transition periods. QC data points remained centered around the established mean, with no consistent upward or downward trends observed following the solvent switch for the majority of analytes. Variability patterns, as reflected by the dispersion of daily QC points relative to the control limits, were similar in both datasets. See Appendix I for Levey–Jennings charts. Histogram Analysis Histogram analysis demonstrated similar overall distribution between pre- and post-switch datasets. While minor shifts in central tendency were observed for select analytes, QC results remained appropriately distributed relative to established target concentrations. Distribution width, shape, and dispersion were comparable across periods, indicating consistent analytical variability and precision. No meaningful changes in spread, multimodality, skewness, or tail behavior were observed in the post-switch data, and outlier frequencies remained consistent with expected LC–MS analytical variation. See Appendix I for Histograms. Evaluation of Analytical Variability in Levey–Jennings and Histogram Data Variability observed in select analytes on Levey–Jennings and Histogram charts is consistent with expected analytical performance and does not represent a systematic shift. For certain technically challenging analytes, particularly those with target concentrations near the limit of detection (LOD), increased day-to-day dispersion is anticipated due to inherent method-related variability rather than the solvent transition. System Suitability: Peak Area Assessment System suitability data collected from daily batch runs in November 2024 were reviewed for all 71 analytes to assess potential contamination or background interference following the solvent transition. Across all evaluated batches, Double Blank peak areas for all analytes remained below 25% of the corresponding LLOQ (50% calibrator) average peak area. No analyte exceeded the established acceptance criterion. Double Blank responses at expected retention times were consistent with routine analytical background, indicating no evidence of solvent-related contamination, carryover, or elevated baseline contribution. System Suitability: Signal-to-Noise (S/N) Assessment Data from the first and last run day of each month from June 2024 through November 2024 were reviewed for all 71 analytes using LLOQ (50% calibrator) system suitability injections. Across the evaluation period, average S/N ratios for all analytes exceeded the predefined acceptance criterion of >10. S/N performance remained consistent across months, with no analytes demonstrating sustained decreases or increased variability following the solvent transition. These results indicate maintained instrument sensitivity and confirm that analyte responses remained well above established limits of detection and quantitation throughout the post-transition period. Proficiency Testing (PT) and Alternate Proficiency Testing All PT events conducted before and after implementation of Birch Biotech solvents resulted in passing performance. PT events from August, September, and November 2023 and 2024, including DMPM-B, ETB-B, UT-B, and UT-C modules, showed no failures, unacceptable results, or corrective actions. For analytes not included in College of American Pathologists (CAP) proficiency testing, results from alternate external laboratory comparisons demonstrated acceptable agreement. Internal blind spike testing for analytes not covered by PT or external laboratory comparison showed acceptable agreement between measured and expected values. Conclusion The evaluation of Birch Biotech solvents (IPA, MeOH, and Water) was conducted using longitudinal and distribution-based quality control analyses across a comprehensive LC–MS/MS urine toxicology panel comprising 71 analytes. Analytical performance before and after the solvent transition was assessed using Levey–Jennings trending, histogram distribution analysis, and quantitative comparisons of accuracy and precision metrics. 1. Analytical Comparability No systematic bias shift, increased imprecision, recurring analyte-specific performance issue, or increase in QC rule violations was observed following implementation. Levey–Jennings and histogram analyses confirmed consistent central tendency, spread, and symmetry of QC distributions between pre- and post-transition periods, with no meaningful distributional changes attributable to the solvent change. 2. Long-Term Stability and Lot Consistency Across all QC levels and analytes, the data demonstrate that the solvent transition did not result in measurable changes in analytical performance. QC means remained aligned with established targets, and variability metrics, including standard deviation and percent coefficient of variation (%CV), remained within historical and predefined acceptance limits. Evaluation across multiple operational months and solvent lots did not demonstrate evidence of manufacturing inconsistency. Month-to-month performance trends remained stable, QC failure rates did not increase after the transition, and no persistent solvent lot-associated shifts were identified. QC failures observed during the broader study period were intermittent, analyte-specific, and non-systemic, occurring both before and after the solvent transition. 3. Sensitivity and Background Integrity System suitability assessments confirmed maintained instrument performance following the solvent switch. Peak area evaluations showed no evidence of increased background interference, contamination, or carryover. Signal-to-noise assessments demonstrated preserved analytical sensitivity, with analyte responses remaining well above established limits of detection and quantitation. These findings indicate stable baseline performance, preserved signal integrity, and maintained low-level analytical sensitivity throughout the post-transition period. 4. External Performance Verification Proficiency testing and alternate external performance evaluations further supported analytical equivalency. All CAP proficiency testing events conducted before and after implementation of Birch Biotech solvents resulted in passing performance, with no failures or required corrective actions. For analytes not included in CAP proficiency testing, alternate external laboratory comparisons and internal blind spike verification demonstrated acceptable agreement with expected values, providing additional confirmation that analytical performance was unaffected by the solvent transition. 5. Operational and Procurement Considerations Birch Biotech solvents provide substantial cost reduction relative to the incumbent manufacturer (approximately fourfold lower pricing) and improved supply availability. These operational advantages were achieved without compromise to validated assay performance and operational stability. Summary of Findings QC performance remained stable across all analytes and QC levels. No statistically or operationally meaningful differences were observed between pre- and post-transition datasets. Precision (%CV) and accuracy (bias) metrics met predefined acceptance criteria throughout the evaluation period. No systematic bias shift, increased imprecision, or recurring analyte-specific performance concerns were identified. System suitability assessments confirmed maintained instrument sensitivity and background cleanliness. Levey–Jennings and histogram analyses showed no systematic trends, shifts, or meaningful distributional changes attributable to the solvent transition. Proficiency testing and alternate external evaluations demonstrated continued acceptable performance. Instrument operational reliability and analytical sensitivity were maintained. Material cost reduction and supply stability were achieved without analytical compromise. Based on the data reviewed, Birch Biotech solvents are analytically equivalent to the previously used solvent system for this LC–MS/MS urine toxicology method. The solvent transition was successfully implemented without impact to analytical reliability, data integrity, or quality control performance. Continued routine use is supported under standard QC monitoring and the laboratory's established quality management practices. Appendix I available upon request
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