Development of a column switching for direct online enrichment and separation of polar and nonpolar analytes from aqueous matrices.

Trace substances in surface waters may threaten health and pose a risk for the aquatic environment. Moreover, separation and detection by instrumental analysis is challenging due to the low concentration and the wide range of polarities. Separation of polar and nonpolar analytes can be achieved by using stationary phases with different selectivity. Lower limits of detection of trace substances can be obtained by offline enrichment on solid phase materials. However, these practices require substantial effort and are time consuming and costly. Therefore, in this study, a column switching was developed to enrich and separate both polar and nonpolar analytes by an on-column large volume injection of aqueous samples. The column switching can significantly reduce the effort and time for analyzing trace substances without compromising on separation and detection. A reversed phase (RP) column is used to trap the nonpolar analytes. The polar analytes are enriched on a porous graphitized carbon column (PGC) coupled serially behind the RP column. A novel valve switching system is implemented to enable elution of the nonpolar analytes from the RP column and, subsequently, elution of polar analytes from the PGC column and separation on a hydrophilic interaction liquid chromatography (HILIC) column. To enable separation of polar analytes dissolved in an aqueous matrix by HILIC, the water plug that is flushed from the PGC column is diluted by dosing organic solvent directly upstream of the HILIC column. The developed method was tested by applying target analysis and non-target screening, highlighting the advantage to effectively separate and detect both polar and nonpolar compounds in a single chromatographic run. In the target analysis, the analytes, with a logD at pH 3 ranging from -2.8 to + 4.5, could be enriched and separated. Besides the 965 features in the RP phase, 572 features from real wastewater were observed in the HILIC phase which would otherwise elute in the void time in conventional one-dimensional RP methods.

Online Coupling of Size Exclusion Chromatography to Capillary Enhanced Raman Spectroscopy for the Analysis of Proteins and Biopharmaceutical Drug Products.

The online coupling of size exclusion chromatography (SEC) to capillary enhanced Raman spectroscopy (CERS) based on a liquid core waveguide (LCW) flow cell was applied for the first time to assess the higher-order structure of different proteins. This setup allows recording of Raman spectra of the monomeric protein within complex mixtures, since SEC enables the separation of the monomeric protein from matrix components such as excipients of a biopharmaceutical product and higher molecular weight species (e.g., aggregates). The acquired Raman spectra were used for structural elucidation of well characterized proteins such as bovine serum albumin, hen egg white lysozyme, and ß-lactoglobulin and of the monoclonal antibody rituximab in a medicinal product. Additionally, the CERS detection of the disaccharide sucrose, which is used as a stabilizing excipient, was quantified to achieve a limit of detection (LOD) of 120 µg and a limit of quantification (LOQ) of 363 µg injected on the column.

Quality Control of Personalized Drug Products - Identity and Quantity of Monoclonal Antibodies as Active Pharmaceutical Ingredient.

Deliberate underdosing occurred in personalized preparations of drugs such as monoclonal antibodies as the active pharmaceutical ingredient in the past. To ensure the required quality standard and to prevent future fraud attempts at an early stage, a HPLC-DAD-HRMS method was established. Thereby, identity and quantity of the active ingredients bevacizumab, rituximab and trastuzumab were determined. The analysis of ten samples from seven pharmacies fulfilled the quality criteria and were therefore not objectionable.

Enrichment and quantification of 18 polycyclic aromatic hydrocarbons from intermediates for plastics production by a generic liquid chromatography column switching.

The polycyclic aromatic hydrocarbon concentration in plastic products is regulated in (European Union) No. 1272/2013. However, this only covers the end products and not intermediate substances. Therefore, a generic method was developed to analyze the polycyclic aromatic hydrocarbons listed by the Environmental Protection Agency and the European Union. This method is based on direct large volume injection from solutions of plastic additives followed by liquid chromatography coupled to fluorescence detection. The additives Irganox 1010, ureido methacrylate, and cetyl methacrylate 1618F were used as examples for method development. Two serially coupled columns allowed the matrix to be removed on the first column and the analytes to be separated on the second column. The columns were connected by an intermediate valve. The valve allowed the matrix to be diverted after the first column and water to be dosed upstream of the second column via an additional pump. This allowed samples in aqueous or organic media to be focused at the column head. An injection volume of 100 µl and online aqueous dilution of 1:3 led to a limit of detection below 1 ng/ml for 15 polycyclic aromatic hydrocarbons. Moreover, concentrations between 1.6 and 10.3 ng/ml were found in the three plastic additives.

Development and validation of a method for airborne monoclonal antibodies to quantify workplace exposure.

Modern therapy strategies are based on patient-specific treatment where the drug and dose are optimally adapted to the patient's needs. In recent drugs, monoclonal antibodies (mAbs) are increasingly used as active ingredients. Their patient-specific formulations are not part of the pharmaceutical industry's manufacturing process but are prepared from concentrates by pharmaceutical personnel. During the manufacturing process, however, active pharmaceutical ingredients are released in trace amounts or, in the case of accidents and spills, also in high concentrations. Regardless of the source of entry, mAbs can become airborne, be inhaled, and cause undesirable side-effects such as sensitization. To assess the risk for pharmaceutical personnel, a personal air sampling method was developed and validated for bevacizumab, cetuximab, daratumumab, omalizumab, rituximab and trastuzumab. The method is based on the combination of high-performance liquid chromatography with tandem mass spectrometry (HPLC-MS/MS). The analytical method achieves a limit of detection of 0.30-8.8 ng mL-1, recoveries of 83-96 % (intra-day assay) and 75-89 % (inter-day assay), with no detectable carry-over. A polycarbonate filter proved suitable for sampling airborne monoclonal antibodies, as it achieved 80-104 % recovery across all mAbs. It also showed concentration-independent desorption efficiency. The sampling duration can be up to 480 min without negatively affecting the recovery. MAbs are stable on the polycarbonate filter at 5 °C for 3 days (recovery: 94 % ± 5 %) and at - 20 °C for 14 days (recovery: 97 % ± 4 %). Our method demonstrated that there is a potential for release when handling monoclonal antibodies. However, this can be reduced below the limit of detection by using pressure equalization systems (spikes).

Comparison of originator and biosimilar monoclonal antibodies using HRMS, Fc affinity chromatography, and 2D-HPLC.

Due to the complex manufacturing process of therapeutic monoclonal antibodies, it is hardly possible to produce an identical copy of the original product (originator). Consequently, follow-on products (biosimilars) must demonstrate their efficacy being similar to the originator in terms of structure and function. During this process, a variety of analytical methods are required for this purpose. This study focuses on three particularly relevant analytical techniques: high-resolution mass spectrometry, fragment crystallisable (Fc) affinity chromatography, and two-dimensional peptide mapping. Each analytical method proved able to identify specific differences between originator and biosimilar. High-resolution mass spectrometry was used to characterize the glycan pattern. It was shown that a trastuzumab biosimilar did not have the G0:G0F sugar modification identified in the originator. The application of affinity chromatography to rituximab showed that originator and biosimilar interacted differently with the immobilized Fc receptor. Furthermore, 2D-HPLC peptide mapping demonstrated the influence of orthogonality of separation dimensions, leading to differentiation of a rituximab originator and biosimilar.

Peak broadening caused by using different micro-liquid chromatography detectors.

Advancements in column technology resulted in smaller particles and more efficient phases. In parallel, the use of columns with reduced dimensions is becoming more common. This means the effective column volume is also decreased, thereby making the systems more susceptible to effects of band broadening due to extra-column volume. Despite these trends and the fact that a growing number of miniaturized liquid chromatography systems are being offered commercially, manufacturers often stick to the modular concept with dedicated units for pumps, column oven, and detectors. This modular design results in long connection capillaries, which leads to extra-column band broadening and consequently prevents the exploitation of the intrinsic efficiency of state-of-the-art columns. In particular, band broadening post column has a considerable negative effect on efficiency. In this study, mass flow and concentration-dependent detectors were examined for their influence on band broadening using a micro-LC system. A mass spectrometric detector, an evaporative light scattering detector, two UV detectors, and a previously undescribed fluorescence detector were compared. The influence on efficiency is compared using plate height vs linear velocity data and peak variance. It is shown that an increase in the inner diameter after the post-column transfer capillary leads to significant loss in plate height. Comparing the UV detectors, it could be shown that the dispersion was reduced by 38% by the reduction of the post-column volume. The largest variance was found for the evaporative light scattering detector, which was 368% higher compared to the variance of the detector with the least effect on band broadening.

Flexible Digitization of Highly Individualized Workflows Demonstrated Through the Quality Control of Patient-Specific Cytostatic Application Bags: Digitization from the Perspective of Small and Medium-Sized Laboratories.

In order to ensure a high level of product quality and safety, regular quality controls are mandatory, especially in the pharmaceutical industry. These quality controls are strictly regulated and require a high level of documentation. With the goal of complete traceability, these regulations are constantly being tightened, while a majority of laboratories are working still completely paper-based. This leads to an ever-increasing workload that keeps laboratory staff away from value-adding analytical work. In order to realize complete traceability, a reduction in documentation errors and at the same time a reduction of the individual workload, the digitization of complete workflows seems to be a promising solution.Due to the ongoing shortage of IT specialists and the resulting high implementation costs, many laboratories are understandably hesitant. In this chapter an alternative is presented on how to approach the digitization of complete workflows without the need for IT specialists. The example of quality control analysis of cytotoxic drug solutions was chosen to demonstrate the challenges of such a digitization project. In this way, we contribute to a comprehensive understanding of the tools already available, which can also help other laboratories in their digitization efforts. At the end compliance with GMP and EN ISO/IEC 17025 (2017) regulations was reached.

Development of a multidimensional online method for the characterization and quantification of monoclonal antibodies using immobilized flow-through enzyme reactors.

Complete characterization and quantification of monoclonal antibodies often rely on enzymatic digestion with trypsin. In order to accelerate and automate this frequently performed sample preparation step, immobilized enzyme reactors (IMER) compatible with standard HPLC systems were used. This allows an automated online approach in all analytical laboratories. We were able to demonstrate that the required digestion time for the model monoclonal antibody rituximab could be reduced to 20 min. Nevertheless, a previous denaturation of the protein is required, which also needs 20 min. Recoveries were determined at various concentrations and were 100% ± 1% at 100 ng on column, 96% ± 7% at 250 ng on column and 98% ± 2% at 450 ng on column. Despite these good recoveries, complete digestion was not achieved, resulting in a poorer limit of quantification. This is 50 ng on column under optimized IMER conditions, whereas an offline digest on the same system achieved 0.3 ng on column. Furthermore, our work revealed that TRIS buffers, when used with an IMER system, led to alteration of the peptides and induced modifications in the peptides. Therefore, the addition of TRIS should be avoided when working at elevated temperatures of about 60 °C. Nevertheless, our results have shown that the recovery is not significantly influenced whether TRIS is used or not (recovery: 96 ± 7% with TRIS vs. 100 ± 9% without TRIS).

Integration of segmented microflow chemistry and online HPLC/MS analysis on a microfluidic chip system enabling enantioselective analyses at the nanoliter scale.

In this work, we introduce an approach to merge droplet microfluidics with an HPLC/MS functionality on a single chip to analyze the contents of individual droplets. This is achieved by a mechanical rotor-stator interface that precisely positions a microstructured PEEK rotor on a microfluidic chip in a pressure-tight manner. The developed full-body fused silica chip, manufactured by selective laser-induced etching, contained a segmented microflow compartment followed by a packed HPLC channel, which were interconnected by the microfluidic PEEK rotor on the fused silica lid with hair-thin through-holes. This enabled the targeted and leakage-free transfer of 10 nL fractions of droplets as small as 25 nL from the segmented microflow channel into the HPLC compartment that operated at pressures of up to 60 bar. In a proof of concept study, this approach was successfully applied to monitor reactions at the nanoliter scale and to distinguish the formed enantiomers.

Quality control of cytostatic drug preparations-comparison of workflow and performance of Raman/UV and high-performance liquid chromatography coupled with diode array detection (HPLC-DAD).

The drugs used for treatment during chemotherapy are manufactured individually for each patient in specialised pharmacies. Thorough quality control to confirm the identity of the delivered active pharmaceutical ingredient and the final concentration of the prepared application solution is not standardized yet except for optical or gravimetric testing. However, solution stability problems, counterfeit drugs, and erroneous or deliberate underdosage may occur and negatively influence the quality of the product and could cause severe health risks for the patient. To take a step towards analytical quality control, an on-site analytical instrument using Raman and UV absorption spectroscopy was employed and the results were compared to high-performance liquid chromatography coupled to diode array detection. Within the scope of the technology evaluation, the uncertainty of measurement was determined for the analysis of the five frequently used cytostatic drugs 5-fluorouracil, cyclophosphamide, gemcitabine, irinotecan and paclitaxel. The Raman/UV technique (2.0-3.2% uncertainty of measurement; level of confidence: 95%) achieves a combined uncertainty of measurement comparable to HPLC-DAD (1.7-3.2% uncertainty of measurement; level of confidence: 95%) for the substances 5-fluorouracil, cyclophosphamide and gemcitabine. However, the uncertainty of measurement for the substances irinotecan and paclitaxel is three times higher when the Raman/UV technique is used. This is due to the fact that the Raman/UV technique analyses the undiluted sample; therefore, the sample has a higher viscosity and tendency to foam. Out of 136 patient-specific preparations analysed within this study, 96% had a deviation of less than 10% from the target content.

The influence of injection volume on efficiency of microbore liquid chromatography columns for gradient and isocratic elution.

The injection volume and the associated column volume overload is one of the most common issues in miniaturized chromatography. The injection volume should not exceed 10% of the effective column volume. A further reduction of the injection volume leads to an increase in chromatographic efficiency. However, the signal intensity must be above a certain threshold to generate a chromatographic peak that can be detected. Therefore, the injection volume has to be optimized to reach the ideal balance between chromatographic efficiency and sensitivity. This study examined the general influence of the injection volume for both isocratic and gradient elution, depending on the retention factor and peak standard deviation. For this purpose, substances of different polarity were selected to represent a broad elution spectrum. Besides the model analyte naphthalene, these were mainly pharmaceuticals. For all measurements a microbore column with an ID of 300 µm and packed with 1.9 µm fully porous particles was used. For isocratic elution, the injection volume was varied between 4 and 16% of the effective column volume. The retention factors were adjusted between 2 and 10. For gradient elution, the injection volume was varied between 4 and 160% of the effective column volume. The observed effects were further investigated using the gradient kinetic plot theory. In isocratic elution, a loss in plate height up to 50% was observed for components that elute near the void time. A significant reduction of the chromatographic efficiency was noticed up to a retention factor of 4. In gradient elution, a reduction in peak capacity could only be observed if the injection volume exceeded 40% of the effective column volume. For some substances, only a slight loss in peak capacity was noticed even with a volume overload of 160%.

Determination of liquid chromatography/flame ionization detection response factors for N-heterocycles, carboxylic acids, halogenated compounds, and others.

Many gas chromatography-flame ionization detection (GC/FID) studies are dealing with response behavior of analytes such as alcohols and alkanes. Studies in the field of liquid chromatography (LC)/FID mainly focused on volatile analytes. In contrast, studies on LC/FID by conveyor type interface covered high molecular weight non-volatile biopolymers, whereby no response factors were calculated. With this study, we fill the gap and present response factors of volatile and non-volatile analytes by LC/FID in terms of flow injection (FIA) measurements of the single compounds without an analytical separation by an LC column. In the present study, 56 different compounds such as carboxylic acids, N-heterocycles, halogenated acids, pharmaceuticals, and other compounds were investigated. In some cases, the obtained response factor data confirmed aspects known from GC/FID studies. But this study also disproves several assumptions done in previous response studies as well as the prediction models based upon the experimental data and literature. Especially the response factors and effective carbon number (ECN) values of structural isomers such as pyrazine, pyridazine, and pyrimidine are assumed to be equal in current response prediction models. Contradictory to these assumptions, the experimental response factors and ECN values of, e.g., the structural isomers pyrazine (RFExp = 0.59; ECNExp = 3.66), pyridazine (RFExp = 0.66; ECNExp = 4.1), and pyrimidine (RFExp = 0.63; ECNExp = 3.93) reveal different experimental response factors and ECN than proposed by response factor prediction models (RFExp = 0.64; ECNExp = 4). Graphical abstract Graphical abstract.

A nebulizer interface for liquid chromatography - Flame ionization detection: Development and validation.

Within this study, a novel liquid chromatography (LC)/flame ionization detector (FID) interface was improved. In contrast to previously published interface concepts, the main nebulizer body and the transfer capillary was made of stainless steel. Previously reported problems such as blocking of the transfer capillary were investigated. The simple design of the here presented nebulizer interface allows a convenient handling and the exchangeability of all nebulizer parts targets fast maintenance during routine analysis. A significant advantage is the capability to implement the novel interface into most common gas chromatography (GC)/FID systems. The effects of the instrumental parameters such as backpressure, gas flow, distance between nebulizer nozzle and FID collector or FID temperature on the signal were analyzed and optimized. The influence of the nebulizer material on flame stability and capillary blockage, a well-known problem of former coupling systems, was investigated, too. Finally, the novel interface was validated for the analysis of selected compounds known from literature. Obtained results for chromatographic separation of the alcohols propanol, butanol, pentanol and hexanol, used within previous studies in the field of LC/FID coupling are shown. Limits of detection (LODs), sensitivity and linearity found within this work are compared with LC/FID interfaces developed in the past.

Development of an analytical method to assess the occupational health risk of therapeutic monoclonal antibodies using LC-HRMS.

Monoclonal antibodies are a group of commonly used therapeutics, whose occupational health risk is still discussed controversially. The long-term low-dose exposure side effects are insufficiently evaluated; hence, discussions are often based on a theoretical level or extrapolating side effects from therapeutic dosages. While some research groups recommend applying the precautionary principle for monoclonal antibodies, others consider the exposure risk too low for measures taken towards occupational health and safety. However, both groups agree that airborne monoclonal antibodies have the biggest risk potential. Therefore, we developed a peptide-based analytical method for occupational exposure monitoring of airborne monoclonal antibodies. The method will allow collecting data about the occupational exposure to monoclonal antibodies. Thus, the mean daily intake for personnel in pharmacies and the pharmaceutical industry can be determined for the first time and will help to substantiate the risk assessment by relevant data. The introduced monitoring method includes air sampling, sample preparation and detection by liquid chromatography coupled with high-resolution mass spectrometry of individual monoclonal antibodies as well as sum parameter. For method development and validation, a chimeric (rituximab), humanised (trastuzumab) and a fully humanised (daratumumab) monoclonal antibody are used. A limit of detection between 1 µg per sample for daratumumab and 25 µg per sample for the collective peptide is achieved. Graphical abstract Demonstration of the analytical workflow, from the release of monoclonal antibodies to the detection as single substances as well as sum parameter.

Characterization of peak capacity of microbore liquid chromatography columns using gradient kinetic plots.

The performance of micro-liquid chromatography columns with an inner diameter of 0.3mm was investigated on a dedicated micro-LC system for gradient elution. Core-shell as well as fully porous particle packed columns were compared on the basis of peak capacity and gradient kinetic plot limits. The results for peak capacity showed the superior performance of columns packed with sub-2µm fully porous particles compared to 3.0µm fully porous and 2.7µm core-shell particles within a range of different gradient time to column void time ratios. For ultra-fast chromatography a maximum peak capacity of 16 can be obtained using a 30s gradient for the sub-2µm fully porous particle packed column. A maximum peak capacity of 121 can be achieved using a 5min gradient. In addition, the influence of an alternative detector cell on the basis of optical waveguide technology and contributing less to system variance was investigated showing an increased peak capacity for all applied gradient time/column void time ratios. Finally, the influence of pressure was evaluated indicating increased peak capacity for maximum performance whereas a limited benefit for ultra-fast chromatography with gradient times below 30s was observed.

Micro-liquid chromatography mass spectrometry for the analysis of antineoplastic drugs from wipe samples.

A fast quantification method for the determination of 11 antineoplastic drugs from wipe samples was developed using micro-scale liquid chromatography in combination with tandem mass spectrometry. The extraction efficiency from the wipes has been investigated using different extraction solvents. The results indicate that a mixture of 70/30 water/isopropanol (v/v) acidified with 0.1 % formic acid is suitable to desorb the antineoplastic drugs with sufficient recovery between 80 and 120 %. Compared to conventional liquid chromatography, the total analysis time can be reduced to 2.25 min using a 50 × 0.3 mm column at a flow rate of 25 µL min-1. Ion source parameters as well as the injection volume were optimized to ensure the highest sensitivity. The results of method validation showed an instrumental limit of quantification between 0.0068 and 0.0488 ng mL-1 using an injection volume of 4.25 µL estimated by the signal to noise ratio. Moreover, the retention time repeatability was determined with a maximum relative standard deviation of 0.4 %. Graphical abstract Micro-LC-MS/MS separation of 11 antineoplastic drugs from wipe samples.

A new method for the determination of peak distribution across a two-dimensional separation space for the identification of optimal column combinations.

For the identification of the optimal column combinations, a comparative orthogonality study of single columns and columns coupled in series for the first dimension of a microscale two-dimensional liquid chromatographic approach was performed. In total, eight columns or column combinations were chosen. For the assessment of the optimal column combination, the orthogonality value as well as the peak distributions across the first and second dimension was used. In total, three different methods of orthogonality calculation, namely the Convex Hull, Bin Counting, and Asterisk methods, were compared. Unfortunately, the first two methods do not provide any information of peak distribution. The third method provides this important information, but is not optimal when only a limited number of components are used for method development. Therefore, a new concept for peak distribution assessment across the separation space of two-dimensional chromatographic systems and clustering detection was developed. It could be shown that the Bin Counting method in combination with additionally calculated histograms for the respective dimensions is well suited for the evaluation of orthogonality and peak clustering. The newly developed method could be used generally in the assessment of 2D separations. Graphical Abstract ᅟ.

Characterization of the efficiency of microbore liquid chromatography columns by van Deemter and kinetic plot analysis.

The efficiency of miniaturized liquid chromatography columns with inner diameters between 200 and 300 µm has been investigated using a dedicated micro-liquid chromatography system. Fully porous, core-shell and monolithic commercially available stationary phases were compared applying van Deemter and kinetic plot analysis. The sub-2 µm fully porous as well as the 2.7 µm core-shell particle packed columns showed superior efficiency and similar values for the minimum reduced plate heights (2.56-2.69) before correction for extra-column contribution compared to normal-bore columns. Moreover, the influence of extra-column contribution was investigated to demonstrate the difference between apparent and intrinsic efficiency by replacing the column by a zero dead volume union to determine the band spreading caused by the system. It was demonstrated that 72% of the intrinsic efficiency could be reached. The results of the kinetic plot analysis indicate the superior performance of the sub-2 µm fully porous particle packed column for ultra-fast liquid chromatography.

Selectivity screening and subsequent data evaluation strategies in liquid chromatography: the example of 12 antineoplastic drugs.

Optimization of the chromatographic selectivity is the most important parameter if a separation is needed for the hyphenation of liquid chromatography with mass spectrometry. In mass spectrometry, this is necessary if the investigated analytes have identical mass transitions, like isomers or epimers. For the separation of the 12 most important antineoplastic drugs, a selectivity screening was performed using 20 columns and two organic modifiers and temperatures to find a suitable phase system in order to separate critical peak pairs. Therefore, an evaluation strategy was applied in form of a principal component analysis (PCA), selectivity factor, and overall selectivity comparison to find a suitable phase system. Some boundary conditions were defined to consider the specific requirements of tandem mass spectrometry. The results clearly indicated that the selectivity factor of the critical peak pairs increased using methanol at higher temperature.