The liquid micro junction-surface sampling probe (LMJ-SSP); a versatile ambient mass spectrometry interface

Ambient ionization methods have become important tools in mass spectrometry. The LMJ-SSP can significantly simplify/reduce lengthy sample preparation requirements associated with mass spectrometry analysis. Samples may be introduced through direct contact, insertion and droplet injection, enabling applications from drug discovery and surface analysis to tissue profiling and metabolic mapping. This review examines the underlying principles associated with the LMJ-SSP interface and highlights modifications of the original design that have extended its capability. We summarize different application areas that have exploited the method and describe potential future directions for the adaptable ambient ionization source.

A validated HPTLC method for quantification of cordifolioside A, 20-β-hydroxyecdysone and columbin with HPTLC–ESI–MS/MS characterization in stems of Tinospora cordifolia

The objective of the present work was to develop a simple, specific, and fast high-performance thin-layer chromatographic (HPTLC) method to identify and quantify cordifolioside A, 20-β-hydroxyecdysone and columbin with HPTLC‒electrospray ionization‒tandem mass spectrometry (ESI‒MS/MS) for characterization in Tinospora cordifolia stem extracts. Chromatographic development was performed using a HPTLC aluminum plate, pre-coated with silica gel 60 F₂₅₄ with hexane‒chloroform‒methanol‒formic acid as the mobile phase. Densitometric quantification for 20-β-hydroxyecdysone and cordifolioside A was performed at 254 nm and for columbin at 600 nm after derivatization with anisaldehyde‒sulfuric acid. The optimized mobile phase resulted in chromatographic separation of peaks for cordifolioside A, 20-β-hydroxyecdysone, and columbin at R_F of 0.12, 0.47, and 0.86, respectively. The linear concentration range was found to be 750‒2250 ng/band for 20-β-hydroxyecdysone and cordifolioside A and 675‒1875 ng/band for columbin with (r² > 0.99). The methodology showed good recoveries as 98.96‒101.43% for cordifolioside A, 98.15‒101.56% for 20-β-hydroxyecdysone, and 98.06‒98.80% for columbin. The limit of detection was found for columbin, 20-β-hydroxyecdysone, and cordifolioside A as 53.86 ng/band, 40.90 ng/band, and 107.05 ng/band, while the limit of quantification was found to be 163.21 ng/band, 123.94 ng/band, and 324.38 ng/band, respectively. The relative standard deviation for precision and robustness study for all the markers was found to be within 2%. Three markers were identified and confirmed in T. cordifolia stem extracts by ESI‒MS/MS. Compounds were assigned as norditerpene furan glycosides, ecdysteroids, and diterpenoid furanolactone: cordifolioside A (m/z = 527 [M + Na]⁺; UV λ_max 221 nm), 20-β-hydroxyecdysone (m/z = 481.30 [M + H]⁺; UV λ_max 247 nm), and columbin (m/z = 359 [M + H]⁺; UV λ_max 210 nm). The optimized method was found accurate, reproducible, robust, and specific and can be applied for the quantification of cordifolioside A, 20-β-hydroxyecdysone, and columbin for quality control of extracts of T. cordifolia.

Extraction efficiency and implications for absolute quantitation of propranolol in mouse brain, liver and kidney tissue sections using droplet-based liquid microjunction surface sampling high-performance liquid chromatography/electrospray ionization tandem mass spectrometry

RATIONALE

Currently, the absolute quantitation aspects of droplet-based surface sampling for tissue analysis using a fully automated autosampler/high-performance liquid chromatography/electrospray ionization tandem mass spectrometry (HPLC/ESI-MS/MS) system have not been fully evaluated. Knowledge of extraction efficiency and its reproducibility is required to judge the potential of the method for absolute quantitation of analytes from tissue sections.

METHODS

Adjacent tissue sections of propranolol-dosed mouse brain (10-μm-thick), kidney (10-μm-thick) and liver (8-, 10-, 16- and 24-μm-thick) were obtained. The absolute concentration of propranolol was determined in tissue punches from serial sections using standard bulk tissue extraction protocols and subsequent HPLC separations and MS/MS analysis. These values were used to determine propranolol extraction efficiency from the tissues with the droplet-based surface sampling approach.

RESULTS

Extraction efficiency of propranolol using 10-μm-thick brain, kidney and liver tissues using droplet-based surface sampling varied between ~45 and 63%. The extraction efficiency decreased from ~65% to ~36% with liver thickness increasing from 8 μm to 24 μm. Selecting half of the samples as standards, the precision and accuracy of propranolol concentrations were determined for the other half of the samples that were employed as a quality control data set. The resulting precision (±15%) and accuracy (±3%) were within acceptable limits.

CONCLUSIONS

Quantitation of adjacent mouse tissue sections of different organs and of various thicknesses by droplet-based surface sampling in comparison with bulk extraction of tissue punches showed that extraction efficiency was incomplete using the former method, and that it depended on the organ and tissue thickness. However, once extraction efficiency was determined and applied, the droplet-based approach provided satisfactory quantitation accuracy and precision for assay validations. Thus, once the extraction efficiency was calibrated for a given tissue type, tissue thickness and drug, the droplet-based approach provides a non-labour-intensive and high-throughput means to acquire spatially resolved quantitative analysis of multiple samples of the same type. Published in 2016. This article is a U.S. Government work and is in the public domain in the USA.

The use of mass spectrometry to analyze dried blood spots

Dried blood spots (DBS) typically consist in the deposition of small volumes of capillary blood onto dedicated paper cards. Comparatively to whole blood or plasma samples, their benefits rely in the fact that sample collection is easier and that logistic aspects related to sample storage and shipment can be relatively limited, respectively, without the need of a refrigerator or dry ice. Originally, this approach has been developed in the sixties to support the analysis of phenylalanine for the detection of phenylketonuria in newborns using bacterial inhibition test. In the nineties tandem mass spectrometry was established as the detection technique for phenylalanine and tyrosine. DBS became rapidly recognized for their clinical value: they were widely implemented in pediatric settings with mass spectrometric detection, and were closely associated to the debut of newborn screening (NBS) programs, as a part of public health policies. Since then, sample collection on paper cards has been explored with various analytical techniques in other areas more or less successfully regarding large-scale applications. Moreover, in the last 5 years a regain of interest for DBS was observed and originated from the bioanalytical community to support drug development (e.g., PK studies) or therapeutic drug monitoring mainly. Those recent applications were essentially driven by improved sensitivity of triple quadrupole mass spectrometers. This review presents an overall view of all instrumental and methodological developments for DBS analysis with mass spectrometric detection, with and without separation techniques. A general introduction to DBS will describe their advantages and historical aspects of their emergence. A second section will focus on blood collection, with a strong emphasis on specific parameters that can impact quantitative analysis, including chromatographic effects, hematocrit effects, blood effects, and analyte stability. A third part of the review is dedicated to sample preparation and will consider off-line and on-line extractions; in particular, instrumental designs that have been developed so far for DBS extraction will be detailed. Flow injection analysis and applications will be discussed in section IV. The application of surface analysis mass spectrometry (DESI, paper spray, DART, APTDCI, MALDI, LDTD-APCI, and ICP) to DBS is described in section V, while applications based on separation techniques (e.g., liquid or gas chromatography) are presented in section VI. To conclude this review, the current status of DBS analysis is summarized, and future perspectives are provided.

Quantitation of repaglinide and metabolites in mouse whole-body thin tissue sections using droplet-based liquid microjunction surface sampling-high-performance liquid chromatography-electrospray ionization tandem mass spectrometry

Herein, quantitation aspects of a fully automated autosampler/HPLC-MS/MS system applied for unattended droplet-based surface sampling of repaglinide dosed thin tissue sections with subsequent HPLC separation and mass spectrometric analysis of parent drug and various drug metabolites were studied. Major organs (brain, lung, liver, kidney and muscle) from whole-body thin tissue sections and corresponding organ homogenates prepared from repaglinide dosed mice were sampled by surface sampling and by bulk extraction, respectively, and analyzed by HPLC-MS/MS. A semi-quantitative agreement between data obtained by surface sampling and that by employing organ homogenate extraction was observed. Drug concentrations obtained by the two methods followed the same patterns for post-dose time points (0.25, 0.5, 1 and 2 h). Drug amounts determined in the specific tissues was typically higher when analyzing extracts from the organ homogenates. In addition, relative comparison of the levels of individual metabolites between the two analytical methods also revealed good semi-quantitative agreement.

DBS direct elution: optimizing performance in high-throughput quantitative LC–MS/MS analysis

Background: Automated DBS direct elution techniques eliminate the manual extraction burden of DBS bioanalysis, offer good quantitative performance, the ability to eliminate hematocrit-based assay bias, and, previous reports have demonstrated that significant increases in assay sensitivity compared with manual DBS extraction are possible. Results: An investigation into elucidating parameters for optimized generic DBS direct elution for high sample throughput quantitative bioanalytical applications is presented for the first time. Generic direct elution conditions were identified that enabled LC–MS/MS assay sensitivity to be maximized while retaining acceptable chromatographic performance. Conclusion: Compared with generic conventional DBS manual extraction, assay sensitivity was demonstrated to be increased up to 33-fold across four representative small molecule compounds, using the recommended direct elution conditions.

Profiling of adrenocorticotropic hormone and arginine vasopressin in human pituitary gland and tumor thin tissue sections using droplet-based liquid-microjunction surface-sampling-HPLC-ESI-MS-MS

Described here are the results from the profiling of the proteins arginine vasopressin (AVP) and adrenocorticotropic hormone (ACTH) from normal human pituitary gland and pituitary adenoma tissue sections, using a fully automated droplet-based liquid-microjunction surface-sampling-HPLC-ESI-MS-MS system for spatially resolved sampling, HPLC separation, and mass spectrometric detection. Excellent correlation was found between the protein distribution data obtained with this method and data obtained with matrix-assisted laser desorption/ionization (MALDI) chemical imaging analyses of serial sections of the same tissue. The protein distributions correlated with the visible anatomic pattern of the pituitary gland. AVP was most abundant in the posterior pituitary gland region (neurohypophysis), and ATCH was dominant in the anterior pituitary gland region (adenohypophysis). The relative amounts of AVP and ACTH sampled from a series of ACTH-secreting and non-secreting pituitary adenomas correlated with histopathological evaluation. ACTH was readily detected at significantly higher levels in regions of ACTH-secreting adenomas and in normal anterior adenohypophysis compared with non-secreting adenoma and neurohypophysis. AVP was mostly detected in normal neurohypophysis, as expected. This work reveals that a fully automated droplet-based liquid-microjunction surface-sampling system coupled to HPLC-ESI-MS-MS can be readily used for spatially resolved sampling, separation, detection, and semi-quantitation of physiologically-relevant peptide and protein hormones, including AVP and ACTH, directly from human tissue. In addition, the relative simplicity, rapidity, and specificity of this method support the potential of this basic technology, with further advancement, for assisting surgical decision-making. Graphical Abstract Mass spectrometry based profiling of hormones in human pituitary gland and tumor thin tissue sections.

Liquid microjunction surface sampling of acetaminophen, terfenadine and their metabolites in thin tissue sections

Background: The aim of this work was to evaluate the analytical performance of a fully automated droplet-based surface-sampling system for determining the distribution of the drugs acetaminophen and terfenadine, and their metabolites, in rat thin tissue sections. Results: The rank order of acetaminophen concentration observed in tissues was stomach > small intestine > liver, while the concentrations of its glucuronide and sulfate metabolites were greatest in the liver and small intestine. Terfenadine was most concentrated in the liver and kidney, while its major metabolite, fexofenadine, was found in the liver and small intestine. Conclusion: The spatial distributions of both drugs and their respective metabolites observed in this work were consistent with previous studies using radiolabeled drugs.

Sampling reliability, spatial resolution, spatial precision, and extraction efficiency in droplet-based liquid microjunction surface sampling

RATIONALE

Droplet-based liquid extraction approaches for spatially resolved surface sampling coupled with high-performance liquid chromatography/mass spectrometry (HPLC/MS) provide the ability to deal with complex sample matrices and to identify isomeric compounds not distinguishable by MS methods alone. Improvements in sampling reliability, spatial resolution, spatial precision and extraction efficiency are required to further the analytical utility of such sampling systems.

METHODS

An autosampler capable of droplet-based liquid extraction was coupled with an HPLC/MS system. Visual inspection of the junction formation between the probe and a glass surface allowed evaluation of the liquid junction formation reliability, spatial location and size as a function of variable parameters such as solvent composition, probe-to-surface distance and droplet volume during solvent dispense and aspiration. Quantitative analysis of a component from a model surface using a weak extraction solvent was used to evaluate the effect of extraction time and number of extraction cycles on analyte extraction efficiency.

RESULTS

Reliable junction formation, independent of other variable parameters, was realized simply by maintaining a maximum distance of 0.4 mm between the probe and the sample surface. The smallest liquid junction diameter (1.6 mm) was observed when using a 1 μL dispensed volume and 90% aqueous extraction solvent with either methanol or acetonitrile. Good sampling precision was always achieved using an extraction solvent with at least 50% methanol or acetonitrile by volume. Quantitative sampling of rhodamine B from a magenta Sharpie ink surface using a weak extraction solvent showed that extraction efficiency could be improved by increasing the extraction time or the number of extraction cycles.

CONCLUSIONS

A platform employing a commercially available autosampler coupled to HPLC/MS was developed and successfully applied to investigate the effect of different sampling parameters on the reliability, spatial resolution, spatial precision and extraction efficiency of the liquid junction surface sampling process. This article is a U.S. Government work and is in the public domain in the USA.

Blood microsampling using capillaries for drug-exposure determination in early preclinical studies: a beneficial strategy to reduce blood sample volumes

Background: Capillary microsampling (CMS) of blood with subsequent blood analysis offers a potential strategy to deal with increased demand to reduce blood sample volumes in animal discovery and preclinical studies. Results: A generic approach is presented allowing PK analysis in 15 µl blood samples. CMS blood exposure data were compared with the traditional plasma exposure results in rats and dogs. Blood PK profiles obtained for two different compounds were in agreement with profiles obtained in plasma. From these studies ex vivo blood to plasma ratios were also obtained. In a mouse study, blood PK profiles that were obtained following automatic sampling overlay with the blood PK profiles obtained with CMS. Conclusion: CMS in 15 µl glass capillaries allows collection and handling of small and exact volumes of blood. Although CMS can also be applied for plasma collection, the full benefit is only achieved with blood collection and analysis.

Automated liquid microjunction surface sampling-HPLC-MS/MS analysis of drugs and metabolites in whole-body thin tissue sections

BACKGROUND

The aim of this work was to develop a fully automated liquid extraction-based surface sampling system utilizing a commercially available autosampler coupled with HPLC-MS/MS detection.

RESULTS

Discrete spots selected for droplet-based sampling and automated sample queue generation, for both the autosampler and MS, were enabled by using in-house developed software. In addition, co-registration of spatially resolved sampling positions and HPLC-MS information to generate heat maps of compounds monitored for subsequent data analysis was also available in the software. The system was evaluated with whole-body thin tissue sections from propranolol-dosed rats.

CONCLUSION

The spatial distributions of both the drug and its hydroxypropranolol glucuronide metabolites were consistent with previous studies employing other liquid extraction-based surface sampling methodologies.

Continuous-flow liquid microjunction surface sampling probe connected on-line with high-performance liquid chromatography/mass spectrometry for spatially resolved analysis of small molecules and proteins

RATIONALE

A continuous-flow liquid microjunction surface sampling probe extracts soluble material from surfaces for direct ionization and detection by mass spectrometry. Demonstrated here is the on-line coupling of such a probe with high-performance liquid chromatography/mass spectrometry (HPLC/MS) enabling extraction, separation and detection of small molecules and proteins from surfaces in a spatially resolved (~0.5 mm diameter spots) manner.

METHODS

A continuous-flow liquid microjunction surface sampling probe was connected to a six-port, two-position valve for extract collection and injection to an HPLC column. A QTRAP® 5500 hybrid triple quadrupole linear ion trap equipped with a Turbo V™ ion source operated in positive electrospray ionization (ESI) mode was used for all experiments. The system operation was tested with the extraction, separation and detection of propranolol and associated metabolites from drug dosed tissues, caffeine from a coffee bean, cocaine from paper currency, and proteins from dried sheep blood spots on paper.

RESULTS

Confirmed in the tissue were the parent drug and two different hydroxypropranolol glucuronides. The mass spectrometric response for these compounds from different locations in the liver showed an increase with increasing extraction time (5, 20 and 40 s). For on-line separation and detection/identification of extracted proteins from dried sheep blood spots, two major protein peaks dominated the chromatogram and could be correlated with the expected masses for the hemoglobin α and β chains.

CONCLUSIONS

Spatially resolved sampling, separation, and detection of small molecules and proteins from surfaces can be accomplished using a continuous-flow liquid microjunction surface sampling probe coupled on-line with HPLC/MS detection.

Internal standard application to dried blood spots by spraying: investigation of the internal standard distribution

Background: The scientifically and logistically best way of application of the internal standard (IS) in the analysis of dried blood spots (DBS) analysis is still a matter of debate and investigation. Most commonly the IS is added in the solvent used for extraction of the discs punched from DBS. In this case, the recovery of the non-extracted IS is complete while the recovery of the analyte extracted from DBS is different from the IS. Results: An alternative way for addition of the IS was investigated. A homogeneous distribution and absorption of the test compound across the spots was demonstrated by spraying a solution of a radiolabeled test compound (mimicking an IS solution) onto DBS. Conclusion: This spray-on technique is convenient and easily automatable. Spraying of the solution was rapid, precise and reproducible, and therefore seems to be suitable for routine analysis of DBS by offline and online extraction.

Rapid evaluation for heterogeneities in monoclonal antibodies by liquid chromatography/mass spectrometry with a column-switching system

The development of therapeutic antibodies has grown over the last several years. Most of the recombinant monoclonal antibodies (mAbs) produced by mammalian cells are glycoproteins. Glycosylation of the mAbs can be associated with effector functions, such as antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity, as well as immunogenicity and clearance. Thus, mAb glycan heterogeneity is a significant characteristic associated with the safety and efficacy of the products. Therefore, glycan heterogeneity should be evaluated during research and development (R&D) and during development of mAbs manufacturing processes to identify the process parameters that affect glycan heterogeneity and to enhance understanding of the manufacturing process. There is an increasing need for a rapid, easy, and automated evaluation method for glycan heterogeneity. Liquid chromatography/mass spectrometry (LC/MS) is a method that can be used to analyze glycoforms. LC/MS is marked by the ability to measure the oligosaccharide composition of each glycoform, whereas other general methods, such as capillary electrophoresis, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and ion-exchange chromatography, cannot. However, a laborious off-line purification of mAbs is required to evaluate glycan heterogeneities. In this study, we demonstrate the use of a rapid, easy, and automated evaluation system for mAb glycoforms by LC/MS. This LC/MS system uses a column-switching system equipped with 2 columns, a protein A affinity column and a reversed-phase column (desalting column). We devised 2 column-switching systems: one that targeted intact mAbs (system 1) and one that targeted the light and heavy chains of the mAbs (system 2). Our results show that the proposed systems are applicable as a tool to evaluate the glycoforms in several situations, including the research, development, and production processes of mAbs. Additionally, we hope that our systems are useful as process analytical technology (PAT) for molecular heterogeneities containing glycoforms of mAbs in implementation of quality by design (QbD).

Recent advances in column switching sample preparation in bioanalysis

Column switching techniques, using two or more stationary phase columns, are useful for trace enrichment and online automated sample preparation. Target fractions from the first column are transferred online to a second column with different properties for further separation. Column switching techniques can be used to determine the analytes in a complex matrix by direct sample injection or by simple sample treatment. Online column switching sample preparation is usually performed in combination with HPLC or capillary electrophoresis. SPE or turbulent flow chromatography using a cartridge column and in-tube solid-phase microextraction using a capillary column have been developed for convenient column switching sample preparation. Furthermore, various micro-/nano-sample preparation devices using new polymer-coating materials have been developed to improve extraction efficiency. This review describes current developments and future trends in novel column switching sample preparation in bioanalysis, focusing on innovative column switching techniques using new extraction devices and materials.

Dried blood spots as a sampling technique for the quantitative determination of guanfacine in clinical studies

Background: Dried blood spot (DBS) technology was evaluated for the quantitative determination of guanfacine in human blood in clinical studies. A very sensitive DBS assay has been developed using HPLC coupled with an AB Sciex 5500 QTRAP® (Applied Biosystems/MDS Sciex, ON, Canada) MS system (LC–MS/MS) with a linear calibration range of 0.05 to 25 ng/ml. High-resolution MS using an Exactive Orbitrap® (ThermoFisher, LLC., CA, USA) was compared with the QTRAP using extracted exact mass ion current profiles for guanfacine and its stable-isotope-incorporated internal standard. The sample preparation employed liquid–liquid extraction with methyl t-butyl ether of 5 mm punched DBS card disks, followed by reversed-phase HPLC separation coupled with either MS/MS or high-resolution MS. Routine experiments were performed to establish the robustness of the DBS assay, including precision, accuracy, linearity, selectivity, sensitivity and long-term stability of up to 76 days. In addition, several factors that potentially affect quantitation were investigated, including blood volume for DBS spotting, punch size and punch location. Results: A sensitive research assay with a LLOQ of 0.05 ng/ml was developed and subjected to several components of a method validation common to a regulated bioanalysis procedure employing DBS. This method development and partial validation study determined that spot volume, punch size or punch location do not affect assay accuracy and precision. The DBS approach was successfully applied to a clinical study (a Phase I, randomized, double-blind, placebo-controlled, crossover study to assess the effect of varying multiple oral doses of guanfacine on the pharmacokinetic, pharmacodynamic, safety, and tolerability profiles in healthy adult subjects). The pharmacokinetic profiles for 12 volunteers generated from the DBS assay and from a previously validated plasma assay were compared and were found to be comparable. DBS incurred samples collected from finger prick blood and directly applied to the DBS cards were also analyzed for comparison. Conclusion: From a bioanalytical perspective, DBS sample collection and analysis is a potentially viable alternative for guanfacine determination in clinical studies, utilizing approximately 100 µl of blood per subject profile compared with a few millilitres of blood drawn for conventional plasma bioanalysis.

Exploration of a new concept for automated dried blood spot analysis using flow-through desorption and online SPE–MS/MS

Background: A new concept for simple and generic automation of dried blood spot (DBS) analysis is evaluated. Flow-through desorption of the blood spot is coupled online to SPE and MS/MS without using a LC column. Blood, spiked with a mixture of test compounds is spotted on paper, dried and then desorbed by means of a prototype clamping device. Results: Conditions for extraction and chromatography on a single SPE cartridge were optimized with respect to clean-up, separation and ionization suppression. Addition of internal standard using loop-injection upstream of the clamped blood spot was examined and proved to be simple and reliable. Validation results for the 1–1000 ng/ml range are well within acceptance criteria for bioanalysis. Conclusion: Results demonstrate feasibility of the DBS SPE–MS/MS concept for efficient automation of the entire DBS analysis workflow.

Impact of internal standard addition on dried blood spot analysis in bioanalytical method development

Background: Addition of internal standards to dried blood spot (DBS) specimens can be complicated. Therefore, we studied the feasibility of different internal standard addition procedures. Nevirapine and its stable-isotope analogue were used as model compounds and concentrations in DBS specimen were determined by matrix-assisted laser desorption/ionization-triple quadrupole tandem mass spectrometry using selected reaction monitoring. Results: The addition procedure of the stable isotope-labeled internal standard had significant impact on observed nevirapine concentrations. Relative recovery rates depending on the internal standard addition procedure ranged between 11.4 and 107.9%. Experiments with different punch sizes (5 and 7 mm diameter) showed no significant influence on observed nevirapine concentrations. Conclusion: Application of internal standard prior to blood spotting provided good nevirapine recoveries and this procedure is well suited for applying DBS in infectious diseases, especially in HIV-infection treatment.

Determination of oseltamivir (Tamiflu®) and oseltamivir carboxylate in dried blood spots using offline or online extraction

Background: Using dried blood spots (DBS) for quantitation of the antiviral drug oseltamivir (Tamiflu®), an ester prodrug, and its active metabolite oseltamivir carboxylate could provide ethical and logistic benefits. Hence, its feasibility was investigated using a previously developed column-switching LC–MS/MS method. Results: Sensitivity, precision and accuracy in DBS were comparable to standard plasma assays. Chemically treated cards provided enhanced ex vivo stability of the ester prodrug in rodent blood. Online extraction was realized using the manual TLC–MS interface or the fully automated Sample Card and Prep system. Rat pharmacokinetic study data showed good correlation between plasma, liquid blood and DBS. Conclusion: From a bioanalytical perspective, DBS is potentially suited for Tamiflu analysis in animals and humans. Automation of the process by online DBS extraction promises workload reduction and throughput increase.