Accelerating drug screening in forensic hair analysis by applying high-speed polarity switching in HR LC-MS/MS

Significance of the topic

Hair analysis for drugs of abuse is a critical tool in forensic toxicology, workplace testing, clinical monitoring and legal supervision because hair preserves a longitudinal record of exposure. Recent increases in novel psychoactive substances (NPS) and non-medical prescription drug use create demand for analytical workflows that can screen very large target lists and also discover unexpected compounds. High-resolution LC–MS/MS methods coupled with automated non-targeted data processing can therefore improve throughput, broaden detection scope and support legally defensible interpretation of longitudinal (segmental) hair data.

Objectives and study overview

This study evaluated a combined analytical and data-processing approach to accelerate and expand forensic hair screening. The core aims were to: (1) implement a high-resolution LC–QTOF method using rapid polarity switching and data-dependent acquisition (DDA) MS/MS to capture both positive and negative ions; (2) apply a single-method, automated non-targeted processing workflow (Insight Profiler) to detect, align and identify features across segmented hair samples; and (3) demonstrate the approach on real donor hair to support monitoring abstinence and detect both expected drugs and previously unmonitored compounds (pharmaceuticals, personal-care ingredients, pesticides and environmental contaminants).

Methodology

Sample collection and preparation:

• Single 6 cm scalp hair samples per donor, segmented into six 1-cm segments (0–1 cm proximal to 5–6 cm distal).
• Segments washed with dichloromethane, dried overnight and milled to powder.
• Approximately 10 mg powdered hair (±0.5 mg) spiked with internal standard and extracted with 1% HCl in methanol.
• Extracts dried under OFN at 40 °C and reconstituted in 200 µL of 80:20 water:methanol.

Chromatography and mass spectrometry:

• UHPLC: Nexera X2 system with Shim-pack Velox Biphenyl column (100 × 2.1 mm, 2.7 µm). Column temperature 40 °C, flow 0.3 mL/min, total run 17 min; methanol–water gradient with 2 mM ammonium formate and 0.002% formic acid.
• High-resolution mass spectrometry: LCMS-9050 QTOF operated with full-scan MS (m/z 100–1000, 100 ms) and data-dependent MS/MS (DDA) alternating polarity. Polarity switching transition time approximately 800 ms; DDA scheme configured for four MS/MS scans in positive mode and two in negative mode (positive m/z 40–1000, negative m/z 40–1050, collision energy 5–55 V), total DDA cycle ~1.998 s.

Data processing and identification:

• Insight Profiler application used for automated non-targeted processing: feature detection (low threshold), retention-time alignment across segments, statistical filtering and compound identification against multiple libraries and screening lists (NIST, Wiley/HighResNPS, Shimadzu Forensic Toxicology database).
• Processing configured as a single method capturing the entire workflow for batch analysis, enabling alignment of features from the same donor and automated reporting of direction-of-change across hair segments.

Used instrumentation

• UHPLC: Shimadzu Nexera X2
• Column: Shim-pack Velox Biphenyl (100 × 2.1 mm, 2.7 µm)
• High-resolution MS: Shimadzu LCMS-9050 (QTOF)
• Data processing: Insight Profiler (Shimadzu)

Main results and discussion

Detection scope and non-targeted identifications:

• Non-targeted processing detected a wide range of substances beyond classic drugs of abuse, including prescribed and over-the-counter medications (e.g., aripiprazole, risperidone, trazodone and their metabolites), psychoactive metabolites (m-CPP), personal-care ingredients and environmental contaminants such as pesticides (azoxystrobin, carbendazim) and salicylic acid likely derived from anti-dandruff shampoo.
• The workflow returned both expected restricted compounds and numerous previously unmonitored features, showing the benefit of DDA-HRMS over narrow-target triple-quadrupole approaches for broadened screening.

Segmental interpretation and monitoring abstinence:

• Segmental data aligned by Insight Profiler provided temporal profiles for individual donors. A key example showed a donor’s distal segment (5–6 cm) cocaine concentration of 1.24 ng/mg compared with <0.01 ng/mg in the proximal segment (0–1 cm), consistent with historical exposure and abstinence during the monitoring interval. The proximal concentration fell well below the 0.5 ng/mg reporting cutoff, supporting compliance to court-ordered abstinence.
• Aligned chromatograms and isotope pattern checks improved confidence in identifications and allowed automated visualization of concentration trends across hair growth segments.

Method performance and practical configuration:

• Rapid polarity switching with configured DDA cycles enabled collection of informative MS/MS spectra in both polarities within a ~2 s cycle, which is compatible with a 17-minute chromatographic run and high-throughput sample processing.
• Insight Profiler’s single-method approach automated feature detection, alignment and library matching, speeding time from data acquisition to review and enabling batch processing for multiple donors or cohort studies.

Benefits and practical applications

• Broader screening: HRMS DDA with polarity switching detects a wider chemical space (both positive and negative ionizing compounds) and supports retrospective interrogation of data for newly emerging NPS or unexpected contaminants.
• Time efficiency: A single automated processing workflow reduces manual review time and standardizes identification procedures suitable for forensic casework and monitoring programs.
• Segmental insight: The combination of segmental hair sampling and automated alignment supports temporal exposure assessment (e.g., demonstrating abstinence across months) useful in judicial and safeguarding contexts.
• Flexibility: The DDA method can be readily expanded to include additional DoA targets and larger MS/MS libraries to meet evolving forensic requirements.

Future trends and opportunities

• Integration of larger, curated HRMS spectral libraries and community-shared NPS resources will increase identification confidence and allow faster adaptation to novel substances.
• Machine learning and improved scoring algorithms for spectral matching and false-positive reduction will enhance automated non-targeted workflows and support probabilistic reporting in forensic contexts.
• Standardization across laboratories (alignment with SoHT consensus guidelines) and validation efforts will be needed to translate RUO workflows into routine, legally defensible assays for casework and accreditation.
• Routine use of retrospective data mining enabled by full-scan HRMS will allow forensic labs to re-interrogate archived datasets as new compounds of interest emerge.
• Developments in faster polarity switching, acquisition strategies (e.g., mixed DDA/DIA schemes) and increased scan speeds will further improve spectral coverage without compromising chromatographic peak sampling.

Conclusions

Combining high-resolution LC–QTOF with rapid polarity switching DDA and an automated non-targeted data-processing platform provides a practical, scalable workflow for expanded forensic hair screening. The approach identified both expected drugs and numerous pharmaceuticals, personal-care ingredients and environmental contaminants, and it supported segmental interpretation to demonstrate temporal declines consistent with abstinence. While the method shows clear advantages over narrow-target approaches for broad screening and retrospective analysis, formal validation and adherence to forensic guidelines are necessary before routine casework deployment. The workflow is currently offered as Research Use Only (RUO).

References

• Society of Hair Testing (SoHT) consensus guidelines for forensic analysis of drugs of abuse in hair, 2023 (guidance referenced in study).
• Shimadzu LCMS-9050 and Nexera X2 instrument documentation and Insight Profiler application (methods and settings summarized in study).