Lack Of Sample Preparation Research Articles

Rapid and Non-Invasive Determination of Iodine Value by Magnetic Resonance Relaxometry in Commercial Edible Oils

This study presents a fast, non-invasive method to determine the iodine value (IV) of edible oils using Time Domain Nuclear Magnetic Resonance (TD-NMR) and Magnetic Resonance Imaging (MRI) techniques. The IV, which quantifies the degree of unsaturation in fats and oils, is a key parameter in assessing oil quality and detecting potential adulteration. Different edible oils were used in this study (sunflower, soy, olive, sesame, and linseed). Statistically significant regression models (R2 > 0.92) were established between the IV derived from NMR spectra and the longitudinal (T1) and transverse (T2) relaxation times of the oils, which were obtained from MRI and TD-NMR analyses. The regression models obtained allow for the prediction of the IV from the T1 and T2 relaxation times across a range that includes predominantly mono- and polyunsaturated edible vegetable oils. The TD-NMR approach stands out for its speed (<2 min), lack of sample preparation (including direct analysis within the commercial packaging), and reproducibility, with a variability of only 0.62%. Meanwhile, the MRI technique allows for the simultaneous evaluation of multiple samples in a single acquisition. Together, these features make TD-NMR and MRI effective tools for the rapid and reliable analysis of the IV in edible oils.

Rapid analysis of eucalyptus oil adulteration in Moroccan rosemary essential oil via GC-FID and mid-infrared spectroscopy

Essential Oil (EO) extracted from Rosemary is known for its therapeutic, antifungal, stimulant and antibacterial effects. This study aimed to detect and quantify the adulteration of Rosemary essential oil with different percentages of eucalyptus essential oil, using two analytical techniques: gas chromatography with Flame Ionization Detection (GC-FID) and Fourier Transform Mid-infrared spectroscopy (FT-MIR), combined with chemometric tools such as Principal Component Analysis (PCA), Partial Least Squares regression (PLS-R) and support vector regression (SVR). The use of PCA on the results obtained from GC-FID and FT-MIR indicates the possibility of categorizing the data into two distinct groups: adulterated essential oil and non-adulterated essential oil. However, it is noted that GC-FID can only detect adulteration starting from 40%, while spectroscopy is capable of detecting lower percentages of adulteration. The use of PLS-R and SVR calibration models for adulteration quantification demonstrates high performance capabilities for both techniques (GC-FID and FT-MIR), as indicated by high R2 correlation coefficients indicating good fit, with lower root mean square error (RMSE) values demonstrating predictive accuracy. The results suggest that FT-MIR spectroscopy is preferable to GC-FID for the quantification and discrimination of adulterated essential oils. FT-MIR spectroscopy is considered superior to GC-FID due to its non-destructiveness, speed and lack of sample preparation.

Novel optical photothermal infrared (O-PTIR) spectroscopy for the noninvasive characterization of heritage glass-metal objects.

Optical photothermal infrared (O-PTIR) is a recently developed molecular spectroscopy technique that allows to noninvasively obtain chemical information on organic and inorganic samples at a submicrometric scale. The high spatial resolution (≈450 nm), lack of sample preparation, and comparability of the spectral results to traditional Fourier transform infrared spectroscopy make it a promising candidate for the analysis of cultural heritage. In this work, the potential of O-PTIR for the noninvasive characterization of small heritage objects (few cubic centimeters) is demonstrated on a series of degraded 16th century brass and glass decorative elements. These small and challenging samples, typically encountering limitations with existing noninvasive methods such as macroscopic x-ray powder diffraction and μRaman, were successfully characterized by O-PTIR, ultimately identifying the markers of glass-induced metal corrosion processes. The results clearly demonstrate how O-PTIR can be easily implemented in a noninvasive multianalytical strategy for the study of heritage materials, making it a fundamental tool for cultural heritage analyses.

Rapid, low-cost, and in-situ analysis of per- and polyfluoroalkyl substances in soils and sediments by ambient 3D-printed cone spray ionization mass spectrometry

A rapid method to empirically determine the presence of trace per- and polyfluoroalkyl substances (PFAS) in solid media, such as soils, sands, and sediments, without any sample preparation, through ambient ionization mass spectrometry (MS), is described. 3D-printed cone spray ionization (3D-PCSI) is an ambient ionization technique that employs a 3D-printed conductive plastic cone to perform both sampling and ionization. The 3D-PCSI sources are fabricated in the shape of a hollowed square pyramid to hold bulk matrices, and consist of rigid walls to aid in the uniformity and consistency of sampling and ionization. Solid samples are placed within the hollowed pyramid and a solvent is added to perform an in-situ extraction, followed by spray-based ionization when a voltage is applied. The low cost of 3D-printing, its reproducibility at scale, and lack of sample preparation, enables 3D-PCSI-MS to rapidly and efficiently screen for trace PFAS, in-situ, in bulk samples. Demonstrated here is the detection of trace PFAS that were doped into six different soil and sediment matrices, by 3D-PCSI-MS, to validate the universality of the method, irrespective of matrix composition. All PFAS were identified by their indicative MS3 spectra and ranged in detection limits from 100 ppt to 10 ppb depending on the compound and soil classification. Legacy aqueous film forming foams (AFFF) were analyzed in soil by 3D-PCSI-MS, as were soil samples collected around an AFFF testing facility. The sampling rate for 3D-PCSI-MS was less than 2 min per sample, demonstrating the applicability to high-throughput mapping of a contaminated area.

Particle Induced X-ray Emission spectrometry (PIXE) of Hawaiian volcanics: An analogue study to evaluate the APXS field analysis of geologic materials on Mars

The Alpha Particle X-ray Spectrometer (APXS), a field instrument onboard four martian rovers, measures largely unprepared, in situ samples on Mars. The APXS has high precision that enables the determination of elemental concentrations in a wide range of geologic materials. However, lack of sample preparation can lead to heterogeneous matrix effects, and understanding the associated uncertainty is essential for interpreting APXS data. Here we use Particle Induced X-ray Emission spectrometry (PIXE) to analyze a suite of geologic samples from Hawai'i as an analogue study to better understand APXS analyses of martian samples. Wavelength-Dispersive X-ray Fluorescence (WDXRF) analyses of fused glass beads establish higher-accuracy standards for the Hawaiian samples. Sulfate-silicate mixtures were made to evaluate sulfur analysis by PIXE. Results show that the PIXE concentrations for most major elements have 2–6% accuracy, which is comparable to the APXS. However, the PIXE concentrations are systematically high in Al and low in Mg, resulting in lower accuracy (13% and 20%, respectively). Olivine-phyric lavas and most of their altered products have the largest discrepancies with Al concentrations up to 25% high and Mg up to 35% low. Sulfur is systematically high (up to 30% in a basalt matrix) compared to gravimetric S concentrations in the sulfate-silicate mixtures. These systematic deviations in Mg, Al, and S are linked to heterogeneous matrix effects, because PIXE and APXS analyses assume all atoms in a sample to be homogeneously mixed on the sub-micrometer scale, which is not the case. Two key implications for APXS results are: (1) Olivine-bearing samples likely have reported concentrations of Mg that is too low and Al that is too high. Thus, olivine-phyric basalts in Gusev crater and the basaltic sand and soil at three landing sites may have Mg and Al concentrations closer to those of the olivine-phyric shergottites and modelled martian crust than previously thought. (2) Sulfate-silicate mixtures may have overestimated S concentrations reported, resulting in greater uncertainty in the stoichiometry of Ca-sulfates, which is used to deduce the geochemical associations of sulfur in samples.

Laser-Induced Breakdown Spectroscopy (LIBS) on Geological Samples: Compositional Differentiation

AbstractLIBS is a developing analytical technique, which is used to perform qualitative and semi-quantitative elemental analysis of materials (solid, liquid and gas). Recently LIBS became an attractive technique to be used for geological samples, due to its advantages such as fast data collection and the lack of sample preparation. This study is done to improve analytical methods for geochemical analysis of samples during different exploration phases (Mining, filed analysis, etc.), to be used in the future as a real-time analysis method to save money and time spent in labs. In this work, LIBS has been used to differentiate between some geological samples gathered from different areas: South Africa and Namibia. Using principal component analysis (PCA), it was found that LIBS was able to differentiate between the samples even those of the same area. The results from the LIBS technique were correlated with subsequent analysis of the same samples by Particle-Induced X-ray emission (PIXE).

Calibration Approaches for Measurement of Aerosol Multielemental Concentration using Spark Emission Spectroscopy.

A multivariate calibration approach, using partial least squares regression, has been developed for measurement of aerosol elemental concentration. A training set consisting of 25 orthogonal aerosol samples with 9 factors (elements: Cr, Mn, Fe, Ni, Cu, Zn, Cd, Pb, Ti) and 5 levels (elemental concentrations) was designed. Spectral information was obtained for each aerosol sample using aerosol spark emission spectroscopy (ASES) at a time resolution of 1 minute. Simultaneous filter samples were collected for determination of elemental concentration using an inductively coupled plasma mass spectrometry (ICP-MS) analysis. Two regression models, PLS1 and PLS2, were developed to predict mass concentration from spectral measurements. Prediction ability of the models improved substantially when only signature wavelengths were included instead of the entire spectrum. The PLS1 model with 45 selected spectral variables (PLS1-45 model) presented the lowest relative root mean square error of cross validation (RMSECV; 16 - 35%). The detection limits using the PLS1-45 model, for the nine elements were in the range of 0.16 - 0.50 μg/m3. The performance of both multivariate and univariate regression models were tested for an unknown sample of welding fume aerosol. The multivariate model did not provide significantly better prediction compared to the univariate model. In spite of the difference in matrices of calibration aerosol and the unknown test aerosol, the results from PLS model show good agreement with those from filter measurements. The relative root mean square error of prediction (RMSEP) obtained from PLS1-45 model was 13% for Cr, 23% for Fe, 22% for Mn and 12% for Ni. The study shows that in spite of lower spectral resolution and lack of sample preparation, reliable and robust measurements can be obtained using the proposed calibration method based on PLS regression.

Microfluidic detection with acoustic spectroscopy (MIDAS) for analysis of insulin formulation stability

Ultrasonic spectroscopy is a viable complement to current techniques used to analyze insulin stability due to its simplicity, lack of sample preparation, and non-destructive properties.

Screening Tablets for DOB Using Surface‐Enhanced Raman Spectroscopy*

2,5,-Dimethoxy-4-bromoamphetamine (DOB) is of particular interest among the various "ecstasy" variants because there is an unusually long delay between consumption and effect, which dramatically increases the danger of accidental overdose in users. Screening for DOB in tablets is problematic because it is pharmacologically active at 0.2-3 mg, which is c. 50 times less than 3,4-methylenedioxy-N-methylamphetamine (MDMA) and makes it more difficult to detect in seized tablets using conventional spot tests. The normal Raman spectra of seized DOB tablets are dominated by the bands of the excipient with no evidence of the drug component. Here we report the first use of on-tablet surface-enhanced Raman spectroscopy (SERS) to enhance the signal from a low concentration drug. Raman studies (785-nm excitation) were carried on series of model DOB/lactose tablets (total mass c. 400 mg) containing between 1 mg and 15 microg of DOB and on seized DOB tablets. To generate surface-enhanced spectra, 5 microL of centrifuged silver colloid was dispensed onto the upper surface of the tablets, followed by 5 microL of 1.0 mol/dm(3) NaCl. The probe laser was directed onto the treated area and spectra accumulated for c. 20 sec (10 sec x 2). It was found that the enhancement of the DOB component in the model tablets containing 1 mg DOB/tablet and in the seized tablets tested was so large that their spectra were completely dominated by the vibrational bands of DOB with little or no contribution from the unenhanced lactose excipient. Indeed, the most intense DOB band was visible even in tablets containing just 15 microg of the drug. On-tablet surface-enhanced Raman spectroscopy is a simple method to distinguish between low dose DOB tablets and those with no active constituent. The fact that unique spectra are obtained allows identification of the drug while the lack of sample preparation and short signal accumulation times mean that the entire test can be carried out in <1 min.

Surface analysis for Si-wafers using total reflection X-ray fluorescence analysis

Total Reflection X-Ray Fluorescence Analysis is presented as a novel analytical tool for the determination of metal impurities on Si-Wafer surfaces [1]. This method allows accurate quantification of surface coverages down to 1011 atoms/cm2 in a non-destructive way. The technique uses a molybdenum tube, a Si(Li) detector, and instrumentation for the exact control of the angle of incidence which must be set to a particular value below the cricitical angle for total reflection with an accuracy better than 0.1 mrad. Advantages are the lack of sample preparation and vacuum. Standards for quantification can be easily produced. Repeatability tests on three different wafers show good variability even for low concentrations.