Comparison of near-infrared and laser-induced breakdown spectroscopy for determination of magnesium stearate in pharmaceutical powders and solid dosage forms

Towards Point-of-Care Manufacturing and Analysis of Immediate-Release 3D Printed Hydrocortisone Tablets for The Treatment of Congenital Adrenal Hyperplasia

Hydrocortisone (HC) is the preferred drug in children with congenital adrenal hyperplasia due to its lower potency as well as fewer reports of side effects. Fused deposition modelling (FDM) 3D printing holds the potential to produce low-cost personalised doses for children at the point of care. However, the compatibility of the thermal process to produce immediate-release bespoke tablets for this thermally labile active is yet to be established. This work aims to develop immediate-release HC tablets using FDM 3D printing and assess drug contents as a critical quality attribute (CQA) using a compact, low-cost near-infrared (NIR) spectroscopy as a process analytical technology (PAT). The FDM 3D printing temperature (140 °C) and drug concentration in the filament (10%-15% w/w) were critical parameters to meet the compendial criteria for drug contents and impurities. Using a compact low-cost NIR spectral device over a wavelength of 900-1700 nm, the drug contents of 3D printed tablets were assessed. Partial least squares (PLS) regression was used to develop individual calibration models to detect HC content in 3D printed tablets of lower drug contents, small caplet design, and relatively complex formula. The models demonstrated the ability to predict HC concentrations over a wide concentration range (0-15% w/w), which was confirmed by HPLC as a reference method. Ultimately, the capability of the NIR model had preceding dose verification performance on HC tablets, with linearity (R² = 0.981) and accuracy (RMSECV = 0.46%). In the future, the integration of 3DP technology with non-destructive PAT techniques will accelerate the adoption of on-demand, individualised dosing in a clinical setting.

In situ analytical characterization and chemical imaging of tablet coatings using laser induced breakdown spectroscopy (LIBS)

The first report that describes direct visualization and quantitative evaluation of the coating uniformity using the LIBS-based 3D chemical imaging technique.

ATR/FT-IR and NIR Auto-correlation Spectroscopic Analysis of Powder Blending Uniformity of Low-content Magnesium Stearate and Potato Starch

Here, we report on near-infrared and ATR/FT-IR spectroscopic measurements of magnesium stearate and potato starch powder blends. In the pharmaceutical and food industries, magnesium stearate is commonly used as a supplement in powder blends or granules for the purpose of lubrication and to minimize aggregation and adherence. However, excessive blending of magnesium stearate (MgSt) may lead to unwanted effects, and more particularly during the manufacturing of products. Upon blending, the IR bands due to both CH symmetric and anti-symmetric stretching modes decreased and displayed a frequency shift to higher wavenumber as the blending duration increased. The NIR and the auto-correlation spectra were collected during the duration of blending in real-time. The auto-correlation spectra indicated the disaggregation of starch particles and a following effect of excessive blending. We suggest that the disaggregation of starch and the following process can be monitored by NIR and the auto-correlation spectra.

Challenges in detecting magnesium stearate distribution in tablets

Magnesium stearate (MS) is the most commonly used lubricant in pharmaceutical industry. During blending, MS particles form a thin layer on the surfaces of the excipient and drug particles prohibiting the bonding from forming between the particles. This hydrophobic layer decreases the tensile strength of tablets and prevents water from penetrating into the tablet restraining the disintegration and dissolution of the tablets. Although overlubrication of the powder mass during MS blending is a well-known problem, the lubricant distribution in tablets has traditionally been challenging to measure. There is currently no adequate analytical method to investigate this phenomenon. In this study, the distribution of MS in microcrystalline cellulose (MCC) tablets was investigated using three different blending scales. The crushing strength of the tablets was used as a secondary response, as its decrease is known to result from the overlubrication. In addition, coating of the MCC particles by MS in intact tablets was detected using Raman microscopic mapping. MS blending was more efficient in larger scales. Raman imaging was successfully applied to characterize MS distribution in MCC tablets despite low concentration of MS. The Raman method can provide highly valuable visual information about the proceeding of the MS blending process. However, the measuring set-up has to be carefully planned to establish reliable and reproducible results.

Laser-induced breakdown spectroscopy (LIBS), part II: review of instrumental and methodological approaches to material analysis and applications to different fields

The first part of this two-part review focused on the fundamental and diagnostics aspects of laser-induced plasmas, only touching briefly upon concepts such as sensitivity and detection limits and largely omitting any discussion of the vast panorama of the practical applications of the technique. Clearly a true LIBS community has emerged, which promises to quicken the pace of LIBS developments, applications, and implementations. With this second part, a more applied flavor is taken, and its intended goal is summarizing the current state-of-the-art of analytical LIBS, providing a contemporary snapshot of LIBS applications, and highlighting new directions in laser-induced breakdown spectroscopy, such as novel approaches, instrumental developments, and advanced use of chemometric tools. More specifically, we discuss instrumental and analytical approaches (e.g., double- and multi-pulse LIBS to improve the sensitivity), calibration-free approaches, hyphenated approaches in which techniques such as Raman and fluorescence are coupled with LIBS to increase sensitivity and information power, resonantly enhanced LIBS approaches, signal processing and optimization (e.g., signal-to-noise analysis), and finally applications. An attempt is made to provide an updated view of the role played by LIBS in the various fields, with emphasis on applications considered to be unique. We finally try to assess where LIBS is going as an analytical field, where in our opinion it should go, and what should still be done for consolidating the technique as a mature method of chemical analysis.

Improvement of tablet coating uniformity using a quality by design approach

A combination of analytical and statistical methods is used to improve a tablet coating process guided by quality by design (QbD) principles. A solid dosage form product was found to intermittently exhibit bad taste. A suspected cause was the variability in coating thickness which could lead to the subject tasting the active ingredient in some tablets. A number of samples were analyzed using a laser-induced breakdown spectroscopy (LIBS)-based analytical method, and it was found that the main variability component was the tablet-to-tablet variability within a lot. Hence, it was inferred that the coating process (performed in a perforated rotating pan) required optimization. A set of designed experiments along with response surface modeling and kriging method were used to arrive at an optimal set of operating conditions. Effects of the amount of coating imparted, spray rate, pan rotation speed, and spray temperature were characterized. The results were quantified in terms of the relative standard deviation of tablet-averaged LIBS score and a coating variability index which was the ratio of the standard deviation of the tablet-averaged LIBS score and the weight gain of the tablets. The data-driven models developed based on the designed experiments predicted that the minimum value of this index would be obtained for a 6% weight gain for a pan operating at the highest speed at the maximum fill level while using the lowest spraying rate and temperature from the chosen parametric space. This systematic application of the QbD-based method resulted in an enhanced process understanding and reducing the coating variability by more than half.

Vibrational imaging of tablets by epi-detected stimulated Raman scattering microscopy

Proper chemical imaging tools are critical to the pharmaceutical industry due to growing regulatory demand for intermediate and end-product content uniformity testing. Herein we demonstrate stimulated Raman scattering (SRS) imaging of active pharmaceutical ingredient (API) and four excipients within tablets. Tablets from six manufactures were imaged with a speed of 53 s per frame of 512 × 512 pixels (i.e., 200 μs per pixel) and a lateral spatial resolution as high as 0.62 μm. The SRS chemical imaging was compared to confocal Raman mapping and coherent anti-Stokes Raman scattering (CARS) chemical imaging in terms of speed and chemical selectivity. The acquisition speed of SRS imaging is ca. 10(4) times faster than confocal Raman mapping and SRS technique showed superior to CARS chemical selectivity for studied samples. Our data demonstrate the potential of SRS microscopy in high-speed screening of pharmaceutical solid dosage forms.

Characterization of carbon-containing aerosolized drugs using laser-induced breakdown spectroscopy

Aerosolized drug delivery methods have increasingly become popular for pharmaceutical applications. This is mainly due to their ease of application and the more recent advancements incorporating nano-sized generation of particles that find deeper penetration routes and more efficient administration of the drug to specific target organs. Their effectiveness heavily relies on the uniformity of the chemical composition of these aerosolized drugs. Thus, it calls for a real-time on-line analytical tool that can accurately characterize the chemical constituents of the drug powder particles generated to ensure a stringent quality control. We present laser-induced breakdown spectroscopy (LIBS) for the first time as an efficient analytical tool to carry out on-line quantitative chemical characterization of aerosolized drugs. We used three different carbon based aerosolized drugs, namely L-ascorbic acid 2-phosphate sesquimagnesium salt hydrate (C(6)H(9)Mg(1.5)O(9)P.xH(2)O), Iron(II) L-ascorbate (C(12)H(14)FeO(12)), and DL-pantothenic acid hemicalcium salt (C(9)H(16)NO(5)0.5Ca) for our quantitative LIBS studies here. Our results show that LIBS can effectively estimate the quantitative ratios of carbon to various trace elements for each of these drugs, thereby enabling on-line unique characterization of individual aerosolized drugs. The quantitative LIBS technique predicted the [C]/[Mg], [C]/[Fe], and [C]/[Ca] ratios as 4.02+/-0.76, 12.42+/-2.36, and 18.47+/-4.39 for each of the above aerosolized drugs, respectively. Within error limits, we find these ratios in good agreement with the respective stoichiometric values of 4, 12, and 18 corresponding to the drugs above. Thus, the work demonstrated the utility and validity of LIBS in accurate on-line identification of drug powders during real-time manufacturing processes.

Process characterization of powder blending by near-infrared spectroscopy: blend end-points and beyond

The purpose of this paper is to utilize near-infrared (NIR) spectroscopy to characterize powder blending in-line. A multivariate model-based approach was used to determine end-point and variability at the end-point of blending processes. Two monitoring positions for NIR spectrometers were evaluated; one was located on the top of the Bin-blender and the other was on the rotation axis. A ternary powder mixture including acetaminophen (APAP, fine and coarse powder), lactose (LAC) and microcrystalline cellulose (MCC, Avicel 101 and 200) was used as a test system. A Plackett-Burman design of experiments (DOE) for different blending parameters and compositions was utilized to compare the robustness of end-point determination between the multivariate model-based algorithm and reference algorithms. The end-point determination algorithm, including root mean square from nominal value (RMSNV) and two-tailed Student's t-test, was developed based on PLS predicted concentrations of all three constituents. Mean and standard deviation of RMSNV after end-point were used to characterize blending variability at the end-point. The blending end-point and variability of two sensors were also compared. The multivariate model-based algorithm proved to be more robust on end-point determination compared to the reference algorithms. Blending behavior at the two sensor locations demonstrated a significant difference in terms of end-point and blending variability, indicating the advantage to employ process monitoring via NIR spectroscopy on more than one location on the Bin-blender.

Characterization of tablet film coatings using a laser-induced breakdown spectroscopic technique

Laser-induced breakdown spectroscopy (LIBS) was evaluated as an early phase process analytical technology (PAT) tool for the rapid characterization of pharmaceutical tablet coatings. Measurement of coating thickness, uniformity, and photodegradation-predictive potential of the technique were evaluated. Model formulation tablets were coated with varying amounts (2%-4% wt/wt) of red and yellow Opadry II, and a pulsed laser was used to sample at multiple sites across the tablet face. LIBS was able to successfully detect the emissions of Fe and Ti in the coated samples, and a proportional increase in signal with coating thickness was observed. Batch-to-batch variability in the coating procedure was also easily monitored by LIBS. The coating thickness was non-uniform across the tablet surface with higher thickness at the edges, likely due to the concave shape of the tablet. Film coating levels and color of the film had been subjected to photostability studies according to the International Conference on Harmonisation (ICH) guideline to determine effectiveness of the film coats. LIBS measurements of coating thickness provided a good correlation (R (2) > 0.99) to photodegradation as measured by high-performance liquid chromatography (HPLC). Last, the concentration of Fe in the coating was varied and monitored by LIBS. Increasing photostability was observed with increasing levels of ferric oxide, providing a new understanding of the photoprotection mechanism in the coated formulation. Determination of levels of ferric oxide and coating thickness by LIBS demonstrated its utility as a good PAT tool for the determination of photoprotection of the drug, thereby enabling facile optimization of the coating process.

Plasma spectroscopy analysis technique based on optimization algorithms and spectral synthesis for arc-welding quality assurance

A new plasma spectroscopy analysis technique based on the generation of synthetic spectra by means of optimization processes is presented in this paper. The technique has been developed for its application in arc-welding quality assurance. The new approach has been checked through several experimental tests, yielding results in reasonably good agreement with the ones offered by the traditional spectroscopic analysis technique.

Laser-Induced Breakdown Spectroscopy of Composite Samples: Comparison of Advanced Chemometrics Methods

Laser-induced breakdown spectroscopy is used to measure chromium concentration in soil samples. A comparison is carried out between the calibration curve method and two chemometrics techniques: partial least-squares regression and neural networks. The three quantitative techniques are evaluated in terms of prediction accuracy, prediction precision, and limit of detection. The influence of several parameters specific to each method is studied in detail, as well as the effect of different pretreatments of the spectra. Neural networks are shown to correctly model nonlinear effects due to self-absorption in the plasma and to provide the best results. Subsequently, principal components analysis is used for classifying spectra from two different soils. Then simultaneous prediction of chromium concentration in the two matrixes is successfully performed through partial least-squares regression and neural networks.