Direct Analysis Of Solid Samples Research Articles

Development and initial evaluation of a combustion-based sample introduction system for direct isotopic analysis of mercury in solid samples via multi-collector ICP-mass spectrometry

High-precision isotopic analysis of mercury (Hg) using multi-collector ICP-mass spectrometry (MC-ICP-MS) is a powerful method for obtaining insight into the sources, pathways and sinks of this toxic metal. Modification of a commercially available mercury analyzer (Teledyne Leeman Labs, Hydra IIc – originally designed for quantification of Hg through sample combustion, collection of the Hg vapor on a gold amalgamator, subsequent controlled release of Hg and detection using cold vapor atomic absorption spectrometry CVAAS) enabled the system to be used for the direct high-precision Hg isotopic analysis of solid samples using MC-ICP-MS – i.e., without previous sample digestion and subsequent dilution. The changes made to the mercury analyzer did not compromise its (simultaneous) use for Hg quantification via CVAAS. The Hg vapor was mixed with a Tl-containing aerosol produced via pneumatic nebulization, creating wet plasma conditions, and enabling the use of Tl as an internal standard for correction of instrumental mass discrimination. Accurate and precise (0.10 ‰ 2SD, δ202Hg, n = 5) results were obtained for an in-house standard solution of Hg (20 ng Hg sample intake). Initial validation relied on the successful analysis of two solid certified reference materials of biological origin (BCR CRM 464 Tuna fish and NRC-CNRC TORT-3 Lobster hepatopancreas). It was shown that instrumental mass discrimination can be adequately corrected for by relying on the use of an aqueous Hg standard solution (NIST SRM 3133), without the need of matrix-matching. The novel setup developed thus allows for direct high-precision isotopic analysis of Hg in solid samples, thus enhancing the sample throughput. It is also suited for samples for which low amounts are available only and/or that are characterized by low Hg concentrations.

Diverse thermal desorption combined with self-aspirating corona discharge ionization for direct mass spectrometry analysis of complex samples.

The thermal desorption (TD) technique is widely employed in modern mass spectrometry to facilitate the detection of non-volatile analytes. In this study, we developed a compact TD device based on a small resistance wire and coupled it with a self-aspirating corona discharge ionization (CDI) source to conduct direct MS analysis of various liquid and solid samples. Due to its small size and low heat capacity, the temperature of the TD module can be flexibly and rapidly modulated by controlling the power sequence. Multiple heating modes, including pulse heating (PH), isothermal heating, and step heating (SH), are realized and characterized, and then applied for the detection of different real samples. In particular, the PH mode is suitable for the simultaneous detection of multiple components in samples with relatively simple matrices, while the SH mode is capable of component separation. In addition, the sensitivity and quantitative capability of the TD-CDI system for DEP solutions were tested, showing acceptable stability with a relative standard deviation of about 6.7% and a detection limit of 0.088 ng. Overall, the developed TD-CDI system provides a simple, convenient, and versatile tool for direct mass spectrometry analysis of real samples.

Direct solid sample analysis of low-cost jewelry using spectroanalytical techniques: exploratory chemical data evaluation and metal migration with synthetic sweat.

Humans have used jewelry for a long time. Initially, this habit had religious purposes for individual protection, then it became a compliment accessory to noble appearance until its popularization with production using cheaper and potentially toxic chemical elements. Therefore, the health of people of low social status has been compromised in such a way that a big part of the metals present in these accessories are potentially toxic. In this regard, with the proposition of legislation limiting these elements' concentrations, several analytical techniques have been used to study their determinations; laser-induced breakdown spectroscopy (LIBS) direct analysis of solids has been highlighted in the past years due to many advantages in several areas. In this study, LIBS and energy dispersive X-ray fluorescence (ED-XRF) were implemented in low-cost jewelry analyses. Then, an exploratory data analysis was carried out using chemometric tools. Finally, the migration of these elements to synthetic sweat was studied to verify its contact with human organisms, and inductively coupled plasma optical emission spectrometry (ICP OES) was employed for the determination of Al, Cd, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Sb, Sn, and Zn.

OpenASAP: An affordable 3D printed atmospheric solids analysis probe (ASAP) mass spectrometry system for direct analysis of solid and liquid samples

Atmospheric Solids Analysis Probe (ASAP) mass spectrometry is a versatile technique allowing direct sampling of solid and liquid samples, but its adoption is limited due to the high cost of commercial ASAP systems. To address this, we present OpenASAP, an open-source ASAP system for mass spectrometers that can be fabricated for $20 or less using 3D-printing. Our design is readily adaptable to instruments from different manufacturers and can be produced with a variety of additive manufacturing techniques on consumer-grade 3D-printers. The probe allows for rapid sampling of solid and liquid samples without sample preparation, making it useful for high throughput screening, investigating spatial localization and function of analytes in biological samples, and incorporating mass spectrometry in instructional settings. We demonstrate its effectiveness by obtaining mass spectra of three natural product standards at levels as low as 10 ng/ml in liquid samples, and detecting these metabolites in microbial cultures that are difficult to analyze due to complex sample matrices or analyte properties. Furthermore, we demonstrate direct sampling of thin layer chromatography (TLC) spots of these cultures.

Multi-element analysis of solid food materials via mixed standards pellet laser ablation inductively coupled plasma mass spectrometry

Accurate monitoring of minor and trace elements in food is of great significance for maintaining human health. Although laser ablation inductively coupled plasma mass spectrometry technique (LA-ICP-MS) is well-established for the direct analysis of solid sample, the lack of an appropriate external standard for quantitative calibration remains the main challenge. Herein, we developed a novel calibration strategy based on the mixed fine-particulate food reference material pellets as the external standard to accurately measure the multi-elements in various solid food samples. Three in-house prepared pellet standards exhibited good homogeneity (RSD < 9%) and the limits of quantitation (LOQs) ranged from 0.0003 (Sr) to 0.86 μg g−1 (Ca). Analytical results of the food NIST reference materials and typical food samples were in good agreement with the certified or reference values, respectively. The proposed method is a promising alternative for routine elemental bulk and/or imaging analysis in food safety laboratories.

Porous Chitosan Composite Membrane Tandem Laser-Induced Breakdown Spectroscopy for Detection of Metal Elements in Liquid Samples

Laser-induced breakdown spectroscopy (LIBS) is currently one of the most popular techniques for direct element analysis of solid samples. However, when directly used for liquid sample analysis, there are disadvantages, including sample splashing, plasma quenching, and poor signal stability. These problems can be overcome through liquid-solid matrix conversion; at the same time, LIBS signal enhancement can be realized, and the sensitivity of detection of liquid samples can be improved. For this research, the authors used chitosan (CS) as a raw material, and introduced poly(vinyl alcohol) (PVA) and polyethyleneimine (PEI) to finally synthesize a new type of porous membrane material with better stability and more functional group content. The membrane was used as a liquid-solid conversion matrix material combined with LIBS technology to successfully achieve rapid separation and detection of Cu, Ag, Pb, and Cr, and the corresponding detection limits can reach 0.038, 0.069, 0.012, and 0.009 mg/L, respectively. This method further improves the sensitivity of the LIBS method. Combining it with membrane materials will replace inactive membranes and open up a new way for the rapid analysis of solution samples using LIBS technology.

Real-Time Sniffing Mass Spectrometry Aided by Venturi Self-Pumping Applicable to Gaseous and Solid Surface Analysis.

Based on the Venturi self-pumping effect, real-time sniffing with mass spectrometry (R-sniffing MS) is developed as a tool for direct and real-time mass spectrometric analysis of both gaseous and solid samples. It is capable of dual-mode operation in either gaseous or solid phase, with the corresponding techniques termed as Rg-sniffing MS and Rs-sniffing MS, respectively. In its gaseous mode, Rg-sniffing MS is capable of analyzing a gaseous mixture with response time (0.8-2.1 s rise time and 7.3-9.6 s fall time), spatial resolution (<80 μm), three-dimensional diffusion imaging, and aroma distribution imaging of red pepper. In its solid mode, an appropriate solvent droplet desorbs the sample from a solid surface, followed by the aspiration of the mixture using the Venturi self-pumping effect into the mass spectrometer, wherein it is ionized by a standard ion source. Compared with the desorption electrospray ionization (DESI) technique, Rs-sniffing MS demonstrated considerably improved limit of detection (LOD) values for arginine (0.07 μg/cm2 Rs-sniffing vs 1.47 μg/cm2 DESI), thymopentin (0.10 μg/cm2 vs 2.67 μg/cm2), and bacitracin (0.16 μg/cm2 vs 2.28 μg/cm2). Rs-sniffing is applicable for the detection of C60(OCH3)6Cl-, an intermediate in the methoxylation reaction involving C60Cl6 (solid) and methanol (liquid). The convenient and highly sensitive R-sniffing MS has a characteristic separation of desorption from the ionization process, in which the matrix atmosphere of desorption can be interfaced by a pipe channel and self-pumped by the Venturi effect with consequent integration using a standard ion source. The R-sniffing MS operates in a voltage-, heat-, and vibration-free environment, wherein the analyte is ionized by a standard ion source. Consequently, a wide range of samples can be analyzed simultaneously by the R-sniffing MS technique, regardless of their physical state.

About this Issue

This BrJAC issue starts with an interview with Edenir R. Pereira Filho, an Associate Professor at the Federal University of São Carlos (UFSCar). His research spans multiple sectors, including spectroanalytical methods for direct solid sample analysis, especially electronic waste. He is also an expert in designing experiments using chemometric tools and has a YouTube channel to share his research group´s contributions. He finished his pleasant interview with an important comment: “Treat your students with special care.”. The point of view shows an interesting and relevant discussion on the limit of detection (LOD) and the use of significant digits. The author’s conclusion is clearly stated: “The LOD must be reported with a single digit, which is significant but uncertain”. I completely agree with such a claim and reinforce that as scientists that handle numbers, we have to be aware that all measurements contain some kind of uncertainty, and significant figures show us what that uncertainty is. Nanomaterials have been increasingly studied for medical applications, and one crucial aspect that has drawn attention is the safety concerns of handling and using nanoparticles. Do the benefits outweigh the risks? Accordingly, the letter presents a thorough discussion on nanostructured materials and provides an update on the challenges associated with nanomaterials production with a focus on nanomedicine. Analytical chemistry has always been associated with the needs of society, and two reviews address issues involving environmental analysis. One of them gives an overview of arsenic speciation methods and the challenges represented by contamination in soil, water, and food supplements. The other reports the analysis of compounds using minimal or no sample preparation. Such an approach includes the development of less invasive and more continuous testing, resulting in devices that cover the trend of point-of-care (POC) analysis. Two exciting articles have been included in this BrJAC issue. The first reports on the synthesis, characterization, and application of zeolitic imidazolate frameworks for adsorption processes. The authors have demonstrated that their material presents excellent adsorption capacity and can be successfully employed to remove arsenic species from aquatic environments. The other article describes a thorough study on a cost-effective sorbent (a lignin-based bio-alkyd resin) prepared from the reaction between oxidized lignin with a mixture of palmitic acid and glycerol. Molybdenum (in the form of a Mo/thiocyanate complex) can be selectively extracted from complex samples (mice liver, pharmaceuticals, water, and fertilizer samples) for further spectrophotometric detection with enhanced sensitivity. As for technical notes, the issue presents two attractive studies. The first shows how the combination of threshold QTOF-MS measurements and quantum-chemical calculations allows for the understanding of the increased stability of sodiated sucralose compared to the protonated one. Neodymium and praseodymium can be found in permanent magnets at very low levels, and a method to determine both metals with high accuracy and precision is presented in the other work. It is exciting to see the growing interest of researchers worldwide for BrJAC, as shown in this issue. The articles reveal that analytical chemistry is a long-standing example of an interdisciplinary approach to scientific research, pushing the field into emerging topics of societal importance.

Using of electrothermal vaporization for direct analysis of zinc solid samples by two-jet arc plasma optical emission spectrometry

The technique of the direct analysis of zinc solid samples by two-jet arc plasma optical emission spectrometry (TJP-OES) with electrothermal vaporization (ETV) of samples is developed. Vaporization of sample matrix (zinc) and analytes from graphite tube during different temperature programs is investigated. The matrix influences from zinc on the signals of analytes are studied in detail. It has been shown that the simultaneous vaporization of analytes and sample matrix makes it possible to determine the content of the largest number of analytes elements with insignificant matrix effects. The results of optimization of instrumental parameters of TJP-OES analysis are presented. The technique of direct ETV-TJP-OES analysis of zinc provides limits of detection (LODs) of Ag, Al, Au, B, Ba, Be, Ca, Co, Cr, Fe, Ga, Mg, Mn, Ni, Re, Sn and Sr from 0.05 to 100 ng g−1. Due to the high efficiency of ETV for the sample introduction the LODs of most analytes were improved from 2 to 20 times comparing to the TJP-OES with standard sample introduction system.

Multielement determination of metals in edible seeds by HR-CS GF AAS and direct analysis

This work reports, for the first time, the multielement determination of Cd, Ni and Fe concentrations in edible seeds via high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS), using direct solid sample analysis. First, Cd (228.802 nm) concentration was determined using 400 and 1600 °C as pyrolysis and atomisation temperatures, respectively. In sequence, from the same sample aliquot, Ni (232.003 nm) and Fe (232.036 nm) concentrations were determined using 2500 °C as the atomisation temperature. A combination of Pd/Mg and H2O2 was used as a chemical modifier to improve the precision and overcome smoke interferences. Multielement aqueous standard solutions were used for calibration, and the detection limits were 3.1 µg kg−1 for Cd, 0.062 mg kg−1 for Ni and 3.4 mg kg−1 for Fe. The trueness was proven by analysing a standard reference material of Tomato Leaves (NIST SRM 1573a). The following concentration ranges were found in the samples: 39–254 µg kg−1 for Cd; 1.1–8.0 mg kg−1 for Ni; and 38–147 mg kg−1 for Fe. The Cd contents in with-shell pumpkin and in roasted and raw sunflower seed samples were above the maximum acceptable Cd level in cereals, as established by the Codex Alimentarius Commission of 100 µg kg−1.

Comparison of the analytical capabilities of a facility with the arc double-jet argon plasmatron and a Grand-Potok complex in determination of the content of rare-earth elements in geological samples by atomic emission spectrometry

The method of atomic emission spectrometry with arc spectrum excitation provides determination of rare earth elements (REE) in geological samples by direct analysis of solid samples without a long-term preliminary sample preparation. Using the analysis of a rare-earth ore sample from the Tomtor niobium-rare-earth deposit as an example, we compared the analytical capabilities of a Grand Potok installation and a two-jet arc plasmatron (TJP) in combination with a DFS-458S spectrograph equipped with a multichannel emission spectrum analyzer (MAES). It is shown that a higher temperature of the TJP plasma (~7500 K) compared to that of the arc discharge (~5500 K) and the shift in the recording range of a DFS-458S spectrum to longer wavelengths (280 – 245 nm) provided a more reliable determination of REE using a larger number of analytical lines with lower detection limits. The correctness of the results of REE determination was confirmed by comparison with the data obtained by the ICP-MS method.

Determination of Total Mercury and Carbon in a National Baseline Study of Urban House Dust

Mercury (Hg) is one of the top ten chemicals of concern for public health, according to the World Health Organization. This study investigates Hg concentrations in house dust collected from urban single family homes, to better understand typical indoor residential exposures. Using direct solid sample analysis, total Hg and carbon (TC) were determined in the &lt;80 µm fraction of settled dust samples collected under the Canadian House Dust Study. Hg concentrations displayed a log-normal distribution with median/geomean of 0.68/0.70 mg/kg (n = 995). A small subset (&lt;1%) of homes exhibited anomalously high dust Hg concentrations (&gt;9.0 mg/kg). A comparison of Hg concentrations in fresh dust and household vacuum dust collected from the same homes indicated no significant difference in the two sampling methods. Total carbon concentrations displayed a median/geomean of 29.3/28.5% (n = 1011). A significant correlation between total Hg and TC in house dust (p &lt; 0.00001) reflects the association between Hg and organic carbon previously observed in soil and sediments. The results of this study indicate a 10-fold enrichment in house dust compared with the average background concentrations reported for soil and sediments (0.07 mg/kg). The observed enrichment is attributable to Hg emissions from indoor sources and/or Hg carried home from occupational sources.

A simple cost-effective paper-based electrochemical device for detection of adulterated sibutramine in slimming products.

This work presents the first paper-based electrochemical device, or ePAD, for direct detection of adulterated sibutramine in slimming products. The ePAD was fabricated using a screen-printing technique for defining the hydrophilic area for sample loading and for the working, reference and counter electrodes. The ePAD gave reproducible responses comparable to both conventional rod electrodes and commercial screen-printed electrodes (SPEs). Use of paper to fabricate the ePAD device provides advantages over the conventional SPE platforms (e.g. glass, ceramics and polymers) in terms of biocompatibility, strong capillary action and environmental friendliness. To detect sibutramine, square wave voltammetry was employed after sample loading on the circular hydrophilic area. The linear range is 2.51 to 83.7 mg L-1 sibutramine, with a precision of 6 %RSD (n = 3) and an instrumental limit of detection (3SD of intercept/slope) of 2.46 mg L-1 sibutramine. Recovery of spiked samples ranged from 83 to 116%. The samples were capsules, slimming coffee powders and nutraceutical beverages. The samples were appropriately diluted to give concentrations within the linear calibration range. Filtration of undissolved solids found with the capsules and coffee powder samples was not required, demonstrating that the method is not susceptible to solid particles. The ePAD is cost-effective (<US$1 per device) and suitable for on-site analysis.

Novel nickel trap coupled with electrothermal vaporization for the direct solid-sampling analysis of cadmium in soil

In this study, a foamed nickel trap (NT) was first utilized as a gas-phase enrichment (GPE) material to preconcentrate Cd under ambient temperature and then release it by heating.

Phosphorous Determination in Biochar-Based Fertilizers by Spark Discharge-Laser-Induced Breakdown Spectroscopy

Biochar-based fertilizers are a new attractive alternative to P supplementation for crops, as they can gradually release the nutrient, avoiding losses and improving soil quality. In this regard, the evaluation of the P amount in biochar-based fertilizers is extremely important for their quality control. Analytical techniques that require sample solubilization are not very efficient for this task, as biochar is difficult to solubilize. Laser-induced breakdown spectroscopy (LIBS) is a promising technique to respond to this demand, as it enables a direct analysis of solid samples, avoiding the complicated process of sample solubilization. In this work, a novel method based on spark discharge (SD) coupled to LIBS was evaluated for P determination in biochar-based fertilizers prepared from three different biomasses. To overcome calibration problems in LIBS analysis, a matrix-matching procedure accomplished by the addition of eucalyptus biochar to calibration standards was used in experiments. This procedure minimized matrix effects and allowed us to achieve a satisfactory accuracy even when applied to similar but different matrices. Furthermore, the developed method is simple, fast, direct, does not generate post-analysis residues and appears appropriate for the quality control of sustainable biochar-based fertilizers and other biochar products.

Evaluation of dried matrix spot sampling for total sulphur determination in automotive gasoline by high-resolution continuum source molecular absorption spectrometry and direct solid sample analysis

In this work, a method for total sulphur determination in automotive gasoline using dried matrix spot sampling is proposed. The method is based on the deposition of the sample on a cellulose-based filter paper and subsequent sulphur quantification via CS diatomic molecule using high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS GF MAS). The sample deposition was carried out, along with the chemical modifier, on a 20-mm filter paper disc previously adapted into a polytetrafluoroethylene (PTFE) mould. The liquid phase was removed by heating the PTFE mould, and then the gasoline sample-embedded filter paper was punched in smaller discs (procedure A) or pulverised (procedure B) before the analyses. The mixture of Pd and Mg was used as chemical modifier to stabilise the sulphur compounds on the filter paper and on the graphite furnace. All the calibration curves constructed using seven different sulphur-containing compounds had a coefficient of determination higher than 0.995 and a linear range from 2 to 150 mg kg−1 S. By using the optimised conditions, the best characteristic mass, limits of detection and quantitation were 6 ng, 0.6 and 1.8 mg kg−1, respectively. The two sampling procedures (A and B) were evaluated for real samples, and procedure B was chosen since it markedly improved the precision. Using this procedure, satisfactory recovery values from 95 to 106% were obtained in the spike-recovery tests. In addition, the S concentrations for the certified reference materials were not statistically different from the certified values at 95% confidence level. Sulphur concentrations from 20 to 46 mg kg−1 were found in the six analysed gasoline samples, and these values were statistically assessed using a reference method (ASTM 5453). Spectral interference caused by MgF and MgCl diatomic molecules was observed and investigated.

Simultaneous Or Sequential Multi-Element Graphite Furnace Atomic Absorption Spectrometry Techniques: Advances Within The Last 20 Years

Electrothermal or graphite furnace atomic absorption spectrometry (ETAAS or GFAAS) is one of the most widely used techniques for determining elements in different matrices (e.g., foodstuffs, pharmaceuticals, biological specimens, nanomaterials, polymers, fuels and environmental media). Numerous elements can be simply and quickly determined with high precision and accuracy, low detection limits, and at moderate cost. The technique is also suitable for direct solid and slurry sample analysis. A crucial feature of this technique is that it can perform simultaneous or sequential multi-element analysis. Over the years, many instruments have come on the market for multi-elemental analysis using mostly line source (LS) GFAAS and high-resolution continuum source (HR-CS) GFAAS. This review covers publications from 2000 to 2020related to the simultaneous or sequential multi-elemental analysis by LS-GFAAS and HR-CS-GFAAS. Mainly the applications, the limits of detection, the use of internal standardization and other aspects regarding the matrix, pyrolysis and atomization temperatures and modifiers are discussed. Finally, a critical comparison is made between the LS-GFAAS and HR-CS-GFAAS techniques.

Direct solid sample analysis using synchronous fluorescence spectroscopy coupled with chemometric tools for the geographical discrimination of coffee samples

This work aims the study chemometric methods for the classification of the origin of coffee samples. Samples of finely pulverized coffee grains were analyzed by synchronous molecular fluorescence spectroscopy to carry out the classification. The spectral data of the samples were obtained in triplicate in two offsets: 10 nm (with emission wavelengths from 240 nm to 600 nm) and 40 nm (from 240 nm to 560 nm), all with 1 nm resolution. Different strategies were performed using the spectra obtained with the offsets of 10 nm and 40 nm and fused data at mid-level (10 nm + 40 nm). The performances of linear and nonlinear methods were compared, the best results were obtained from the raw data from the fusion at low-level of the 10 nm and 40 nm offset spectra with the Pareto optimization criterion.

Comparison of Minimally Invasive Inductively Coupled Plasma-Mass Spectrometry Approaches for Strontium Isotopic Analysis of Medieval Stained Glass with Elevated Rubidium and Rare-Earth Element Concentrations.

Different approaches for the determination of the 87Sr/86Sr isotope ratio of high-Rb glass are compared in this work to assess the suitability of minimally invasive approaches for applications on medieval stained glass (from the ancient Abbey of Stavelot in Belgium). It was found that pneumatic nebulization multicollector inductively coupled plasma–mass spectrometry (PN-MC-ICP-MS) after acid digestion and chromatographic isolation of the target analyte out of the sample matrix can still be seen as the preferred method for the high-precision isotopic analysis of Sr in glass with high Rb and rare-earth element (REE) concentrations. Alternatively, the use of laser ablation (LA) for sample introduction is a powerful technique for the direct analysis of solid samples. However, both the high Rb/Sr ratios in the samples of interest and the presence of REEs at sufficiently high concentrations lead to a large bias in LA-MC-ICP-MS, which cannot be corrected for, even by operating the MC-ICP-MS instrument at higher mass resolution and/or using mathematical corrections. It was demonstrated that LA tandem-ICP-MS (LA-ICP-MS/MS) using CH3F/He as the reaction gas to overcome spectral overlap in a mass-shift approach (chemical resolution) provides a viable alternative when (quasi) nondestructive analysis is required. This approach relies on the monitoring of Sr+ (m/z = 86, 87, and 88) ions as the corresponding SrF+ reaction product ions (m/z = 105, 106, and 107), thus avoiding the occurrence of spectral interference. Self-evidently, the isotope ratio precision attainable using sequential quadrupole-based ICP-MS instrumentation (0.3% RSD) was found to be significantly worse than that of high-precision MC-ICP-MS (0.03% RSD) with simultaneous detection, although it was still fit for the purpose of current applications. In addition to Sr isotopic analysis, the REE patterns and their potential influence on the Sr isotopic composition were evaluated by LA-ICP-MS.

Confocal laser scanning microscopy as a novel tool of hyperspectral imaging for the localization and quantification of fluorescent active principles in pharmaceutical solid dosage forms

Confocal laser scanning microscopy (CLSM) supported with multivariate analysis is proposed as hyperspectral imaging technique to identify, locate, and quantify, in a direct way, active pharmaceutical ingredients (APIs) in synthetic tablets, with the aim of establishing a new analysis methodology that collects qualitative and quantitative information from the surface and inner layers of solid dosage forms. This method is proposed as a novel, non-destructive, rapid, and highly sensitive hyperspectral imaging technique, with an excellent spatial resolution at the microscopic level. Two chemical systems comprising pharmaceutical mixtures of acetaminophen–caffeine–excipients and digoxin–excipients were analyzed by multivariate curve resolution-alternating least squares (MCR-ALS) using emission spectra obtained from microscopic images with the pixel sizes of 512 μm × 512 μm to localize the APIs in the tablets. In addition, partial least squares (PLS) regression models were developed and used for calibration to obtain the concentration of the fluorescent active ingredients. The analysis by MCR-ALS delivered excellent results in localizing the fluorescent compounds; meanwhile, PLS achieved good error parameters for prediction of the external validation set for the quantification of caffeine and less successful quantification of digoxin. The performance of CLSM was evaluated by estimation of the analytical figures of merit of the technique to assess the quantification of APIs, including calculations of the uncertainty in the signal, sensitivity, analytical sensitivity, and ranges of detection and quantification limits. Use of CLSM as hyperspectral imaging attempts to increase the application of this technique in direct analysis of solid samples, showing that autofluorescent compounds can be analyzed for qualitative and quantitative purposes in presence of interferents by application of chemometrics.