Spectrophotometric Measurements Research Articles

Investigation of Dyeing Properties of Mohair Fiber Dyed with Natural Dyes Obtained from Candelariella reflexa

ABSTRACT The current study reports on using ascorbic acid as a possible substitute for improving fastness properties of natural dyes. In the mordanting process, microwave energy, which is a part of the sustainable and ecological production approach, was used. Renewable natural dye source Candelariella reflexa, which is a genus of lichen, was obtained from the trunk of Pinus nigra. Mohair fiber was dyed with natural dye extracted from Candelariella reflexa by using a conventional method. Before dyeing, mohair fiber was subjected to the premordanted process with iron (III) chloride (FeCl3) using microwave energy. In order to determine the effect of mordanting process parameters on dyeing properties, the mordanting process was performed with different concentrations and durations. In the dyeing process, ascorbic acid was added at different concentrations in the dyeing bath to improve the light fastness of samples. After the dyeing process, spectrophotometric features, light, and rubbing and washing fastness of samples were investigated. The color strength, washing, light, and rubbing fastness of dyed mohair fiber improve slightly with the premordanting process and by adding ascorbic acid. The spectrophotometric measurement results show that color coordinates vary from the mordanting time and amount of ascorbic acid. Furthermore, the use of microwave energy in the mordanting process leads to saving of energy and time. Besides, in this study, a machine learning-based model exploiting the artificial neural network (ANN) was developed for prediction of dyeing properties of mohair fiber dyed with natural dyes obtained from Candelariella reflexa. Experimental data obtained through various tests were first used to feed the proposed ANN, and then the trained ANN was validated and tested for the aim of prediction. The study results show that the proposed model can successfully predict most of the dyeing properties of mohair fiber. Therefore, this model can be used as an effective tool to estimate dyeing characteristics of mohair fiber.

Evaluation of color changes during stability studies using spectrophotometric chromaticity measurements versus visual examination

Stability studies are essential to be able to assign an expiration date to medications. Color variation is one of the organoleptic characteristics of actives substances or medications which can indicate the presence of contaminations, impurities or degradations products. However there is no data available comparing the often used visual examination with spectrophotometric measurements during stability studies. The aim of this study was therefore to evaluate precisely how different the two methods are, by comparing the change of color of two drug formulations chosen as models, assessed by visual examination versus a spectrophotometric colorimetric analysis. Paracetamol and parenteral nutrition solutions were stored in stress conditions for up to 46 days, and were subjected to a visual examination using color reference solutions and to lightness and chromaticity measurement to determine their specific color by UV–Vis spectrophotometry. The color of paracetamol solutions changed faster when exposed to stress condition (light), as did the PNS when exposed to heat. In both cases, color variations were detected earlier and more precisely by UV–Vis spectrophotometry than by visual examination. Color measurement using an UV–Vis spectrophotometry should advantageously replace visual examination when assessing colors changes during drug stability studies.

Preparation of TlInSe2 thin films using substrate temperature: Characterization, optical and electrical properties

Chalcogenide materials are very applicable materials that have been utilized in different fields of industry such as photovoltaic, fuel cell, battery, and sensor. Here, we report the fabrication, structure, optical, and DC electrical properties of TlInSe2 thin films with different thicknesses (195, 229, and 365 nm). The structural properties have been studied using XRD and AFM. The results showed that the prepared films are polycrystalline in the Tetragonal system and that the crystalline size increases with the increase of the film's thickness. The lattice indices of TlInSe2 and the inter-planar spacing for each diffraction peak have been calculated. The linear and nonlinear optical parameters have been determined using spectrophotometric measurements in the wavelength range of 200–2500 nm. It is found that the direct energy gap (Egd), the indirect energy gap (Egind), and the phonon energy (Eph) are 1.89, 1.61, and 0.025 eV, respectively. The electrical conductivity measurements were also made for TlInSe2 films of different thicknesses and at temperatures in the range of 30–140 °C. The finding results for our fabricated thin films qualify them for employment in optoelectronic applications.

Exploring microstructural, optical, electrical, and DFT/TD-DFT studies of boron subphthalocyanine chloride for renewable energy applications

Microstructural, optical and electrical properties of boron subphthalocyanine chloride (B- SubPc-Cl) were investigated in order to use it in energy applications. Field emission scanning microscopy (FE-SEM) was used to investigat the surface morphology and the structural nature of B- SubPc-Cl evaporated thin films. The diffuse reflectance spectra of the as-deposited and annealed B-subPc-Cl thin films were investigated based on Kubelka-Munk (K-M) function. The optical characteristics (specular transmission and reflection) were determined from the analysis the spectrophotometric measurements. Organic/inorganic B- SubPc-Cl / n-Si heterojunction diode was successfully fabricated by means of the conventional thermal evaporation technique of B- SubPc-Cl thin film onto n-Si substrates of (110) preferred orientation. The current density–voltage (J–V) of Au/ B- SubPc-Cl / n-Si/Al heterojunction device was measured at selected temperatures. The essential electrical parameters of the device such as the series resistance, ideality factor, and barrier height were estimated from the analysis of current-voltage characteristics of heterojunction diode according to the Cheung-Cheung and Norde methods. The Complex dielectric functions such as the real and imaginary dielectric parts, dielectric modulus, and electrical conductivity of Au/ B- SubPc-Cl / n-Si/Al heterojunction device were carried out with the applied frequency in the range 20 Hz to 1 MHz and selected temperatures from 298 K to 473 K. DFT/TD-DFT calculations with B3LYP/6–31 G level of theory were used to study the optimized geometry and some important parameters of B-SubPc-Cl.

Assessment of the Predictive Value of Spectrophotometric Skin Color Parameters and Environmental and Behavioral Factors in Estimating the Risk of Skin Cancer: A Case-Control Study.

Keratinocyte carcinomas are the most common cancers with different etiological risk factors. The aim of this study was to assess the predictive value of spectrophotometric parameters of skin color in correlation with environmental/behavioral factors to estimate the risk of skin cancer. The case–control study involved 389 patients. The analysis was performed on the training group to build a predictive model and on the testing group to check the quality of the designed model. Area under the curve based on the spectrophotometric skin parameters varied from 0.536 to 0.674. A statistically significant improvement of the area under curve was achieved by adding the number of sunburns for some models. The best single spectrophotometric measurement for estimating skin cancer is the skin melanin index measured on the arm or buttock. Spectrophotometric skin parameters are not very strong but are essential elements of models for estimating the risk of skin cancer. The most important environmental/behavioral factor seems to be the number of sunburns, but not the total exposure to ultraviolet radiation or usage of photoprotectors. Some other pigmentation predictors should be taken into account when creating new models, especially those that can be easily measured in objective and repeatable way. Spectrophotometric measurements can be employed as quick screening skin examination method.

A New Benzoxazole-Based Fluorescent Macrocyclic Chemosensor for Optical Detection of Zn2+ and Cd2+

Background: Benzoxazole-containing ligands find many applications both in medicinal chemistry, catalysis and fluorescence chemosensing. Benzoxazole-containing macrocycles could be therefore a good strategy to achieve stable and selective fluorescent complexes with suitable metal ions. In this work, the synthesis, binding, and photochemical properties of a new fluorescent ligand (L) are reported. L is a cyclophane macrocycle containing the 1,3-bis(benzo[d]oxazol-2-yl)phenyl (BBzB) fluorophore and an aliphatic tetra-amine chain to form the macrocyclic skeleton. Methods: Spectrophotometric and spectrofluorimetric measurements, 1H NMR analysis, and DFT calculations were performed. Results: L behaves as a PET-mediated chemosensor, being emissive at 390 nm at acidic pH and non-emissive at basic pH. The chemosensor is able to detect Zn2+ and Cd2+ in an aqueous medium (acetonitrile–water, 4:1 v/v) at neutral pH through a CHEF effect upon metal ion coordination. Paramagnetic metal ions (Cu2+) and heavy atoms (Pb2+, Hg2+) resulted in a quenching of fluorescence or very low emission. Conclusions: The new cyclophane macrocycle L was revealed to be a selective PET-regulated chemosensor for Zn2+ and Cd2+ in an aqueous medium, being able to bind up to two and one metal cations, respectively. The molecule showed a shifted emission towards the visible region compared to similar systems, suggesting a co-planar conformation of the aromatic fragment upon metal coordination. All these data are supported by both experimental measurements and theoretical calculations.

Comparison of two optical devices used for artificial tooth color selection.

Correct color assessment and the selection of the color of the prosthetic restoration are important aspects of prosthetic treatment, which significantly affect the success of the treatment. The aim of this study was to compare 2 commercial devices used for tooth color selection. The color of maxillary right central incisors and right canines was assessed in a group 100 patients aged 22-40 years (25.11 ±3.24 years), using the Easyshade® spectrophotometer and the ShadeStar® colorimeter. Two visual shade guides were used as references for the tests - VITA VITAPAN® Classical and VITA 3D‑Master. The 2 instruments and the 2 visual shade guides were assessed in terms of agreement in tooth color selection. There were statistically significant differences between the 2 instruments in terms of agreement in tooth color selection as well as between the 2 shade guides. The VITA VITAPAN Classical shade guide was shown to be more accurate in tooth color selection than VITA 3D‑Master. There was agreement between the Easyshade spectrophotometer and ShadeStar colorimeter measurements for incisors in 49% of cases with the VITA VITAPAN Classical shade guide and in 22% of cases with VITA 3D‑Master. In the comparative analysis of the Easyshade and ShadeStar devices with regard to the measurements performed on canines there was 52% agreement for the VITA VITAPAN Classical shade guide and 32% agreement for VITA 3D‑Master. The VITA VITAPAN Classical system demonstrated superior agreement in shade selection as compared to the VITA 3D‑Master system. A low degree of agreement between the optical devices used in the selection of the color of artificial teeth may indicate optical differences between devices from different manufacturers.

Role of rubrene additive for reinforcing the structural, optical, and dispersion properties of polyvinyl alcohol films towards optoelectronic applications

A conventional casting method was used to produce promoted polyvinyl alcohol (PVA) films via rubrene additive. The 1.2 g of PVA dissolved in 120 ml of distilled water and doped with various concentrations (0, 0.1, 0.3 and 0.4 wt%) of rubrene dye. The influence of rubrene dopants on the structural properties of PVA was studied using FTIR and XRD techniques. The semicrystalline nature of the PVA polymer was established by the XRD pattern. FT-IR analysis shows changes in peaks intensities of PVA and their widths are expanded in the presence of rubrene dopants which indicates the interactions between the functional groups of PVA and the rubrene dopants. XRD patterns exhibit the existence of rubrene inside the PVA structure leads to form cross-linking which enhances the amorphous nature within the doped PVA samples. The optical characteristics were investigated using spectrophotometric measurements of transmittance T(λ), reflectance R(λ), and absorbance A(λ) in the spectral range of 200–2500 nm. The indirect and direct optical band-gap values of PVA films decreased from 5.15 eV and 5.69 eV to 3.63 eV and 4.50 eV as rubrene doping ratio was increased from 0 to 0.4 wt%, respectively. The refractive index dispersion region was explained using the single oscillator (Wemple–DiDomenico) model. The extracted values of dispersion energy (Ed), dielectric constant at infinite frequency (ε∞) and lattice dielectric constant (εL) of PVA/rubrene composite films increased from 0.74 eV, 1.31 and 1.35 to 5.35 eV, 3.47 and 4.35; respectively, whereas oscillator energy (Eo) decreased from 2.41eV to 2.17 eV as rubrene contents increased from 0 to 0.4 wt%, respectively. Indeed, these changes in values of dispersion parameters is evidence to the cross-linking bonds between the host polymer and the rubrene dopants. The improvement of optical properties of PVA/rubrene films demonstrates their applicability as eco-friendly packaging materials, particularly in flexible optoelectronic and microelectronic devices.

Degradation of Hybrid Drug Delivery Carriers with a Mineral Core and a Protein-Tannin Shell under Proteolytic Hydrolases.

Hybrid carriers with the mineral CaCO3/Fe3O4 core and the protein–tannin shell are attractive for drug delivery applications due to reliable coupling of anticancer drugs with protein–tannin complex and the possibility of remote control over drug localization and delivery by the external magnetic field. This study aims to elucidate the mechanisms of drug release via enzymatic degradation of a protein–tannin carrier shell triggered by proteolytic hydrolases trypsin and pepsin under physiological conditions. To do this, the carriers were incubated with the enzyme solutions in special buffers to maintain the enzyme activity. The time-lapse spectrophotometric and electron microscopy measurements were carried out to evaluate the degradation of the carriers. It was established that the protein–tannin complex demonstrates the different degradation behavior depending on the enzyme type and buffer medium. The incubation in trypsin solution mostly resulted in the protein shell degradation. The incubation in pepsin solution did not affect the protein component; however, the citric buffer stimulates the degradation of the mineral core. The presented results allow for predicting the degradation pathways of the carriers including the release profile of the loaded cargo under physiological conditions. The viability of 4T1 breast cancer cells with mineral magnetic carriers with protein–tannin shells was investigated, and their movement in the fields of action of the permanent magnet was shown.

Proposed Physicochemical Standards for the Identity and Quality Characteristics of Philippine Virgin Coconut Oil

The growth of the virgin coconut oil (VCO) industry over the past few years has highlighted the need to improve VCO standards to promote better quality and detect adulteration. The Philippine National Standard for VCO (PNS/BAFPS 22:2007) has three groups of parameters – identity characteristics, quality characteristics, and contaminant limits. It has only one identity characteristic – the % fatty acid composition, which is based mainly on Codex Stan 210-1999. However, because the fatty acid composition does not distinguish VCO from refined, bleached, and deodorized coconut oil (RBDCO), additional methods are needed to differentiate VCO and RBDCO and to detect adulteration. This study proposes a new spectrophotometric measurement at 278 nm, which can accomplish both objectives. Regarding VCO quality characteristics, PNS/ BAFPS 22:2007 states that VCO should be colorless and sediment-free. However, some VCO products may have light yellow color due to the method of production, and sedimentation naturally occurs below the freezing point of VCO, which is 25 °C. New methods are proposed to address the concerns of color and sediment. Because the Codex methods are optimized for vegetable oils with long-chain unsaturated fatty acids, some methods need to be adjusted for the analysis of VCO, which is composed mainly of saturated medium-chain fatty acids. These standards and methods can be adopted by regulatory agencies and guide the industry to ensure quality VCO.

A hybrid sensing system combining simultaneous optical and electrochemical measurements: Application to beer discrimination.

A hybrid sensing system, which combines simultaneous cyclic voltammetric (CV) and UV-vis absorbance measurements using a commercial carbon screen-printed electrode and a set of optical fibres in disposable cuvettes, is proposed. The hybrid system approach was applied to 27 samples of recognized beer brands, improving the classification power as compared to only voltammetric or only spectrophotometric measurements. The developed partial least squares discriminant analysis (PLS-DA) model was able to discriminate between five types of beer (lager, marzen, black/stout, alcohol-free and white/ale). The model was also successfully applied to 28 beer samples of white-label brands sold in local supermarkets, demonstrating their similarity to recognized brand beers.

Evaluation on the determination of available phosphorus using blue molybdate in Organosols

Bray and Olsen methods have widely been used for measuring available phosphorous (P) in soil. Those methods have been known resulting good correlation between available P in soil and crops, especially for corn. Correlation between P uptake by plant and P concentration in Bray extractant ranges from 0.74 to 0.94; the method is, therefore, recommended for neutral and acid soils (pH ≤ 7.0). Meanwhile for Olsen method, correlation could span from 0.73 to 0.96 for alkaline soils. Both, however, have been observed to potentially result in false-high available P in Organosols. This might be due to dark color of Bray and Olsen extracts that reacting with blue molybdate and resulting in high values of absorbance during spectrophotometric measurement. In the case for Organosols, dissolved organic substance originates dark color of the extract. Therefore, organic substance should be eliminated prior to the measurement. This research explored an improvement for available P measurement in Organosols by treating the extract with H2O2 and an activated charcoal. This treatment the Olsen extracts has resulted in a notable available P gap, i.e. 102.7 ppm of treated extracts compared to 1207.7 ppm of untreated one.

Preliminary study for the evaluation of a pulsed coaxial plasma gun for removal of iron rust stain from bone artifacts

• Iron stain is one of the most crucial aspects of archaeological bone deterioration. • Chemical reaction between bones and the iron stain was explained. • The coaxial plasma cleaning was used for the first time for removal of iron stain. • The efficiency of plasma cleaning depended on power, numbers of pulses, and etc. • Analytical methods were utilized for the evaluation of the coaxial plasma cleaning. The pulsed coaxial plasma gun is an effective and fast way to remove stains found on the surface of cultural heritage materials. Invisible oil films, dust deposition, corrosion products, or other contaminants can be cleaned by plasma. Iron stain can be found on bone when it is in direct contact with the corroded iron object or in proximity to the corrosion products in the soil. This study aims to evaluate the removal of iron stain from the surface of bone by using Pulsed coaxial plasma. Different parameters of pulsed plasma have been evaluated to reach the best condition of the treatment. Pulsed coaxial plasma was applied to modern bone samples artificially stained with ferric hydroxides. Analytical techniques used to evaluate the iron stain removal were digital microscope, SEM-EDX, FTIR, color measurement by UV spectrophotometer, AFM, pH value, and contact angle measurement. The results indicated that the coaxial plasma is highly effective for iron stain removal and does not affect treated bones. The best cleaning was performed by pulsed argon plasma at 50 pulses, pressure of 0.2 mbar, 0.5 cm distance, and 3kV plasma power.

Norfloxacin in biological samples using dispersive solid-phase extraction method with 2-aminopyridine/graphene oxide nano-plates

In recent years, drug use is on the rise, causing environmental pollution. Therefore, drug control is a common practice in many laboratories. This project focuses on increasing the method for determining small amounts of norfloxacin in aqueous and biological samples. Solid-phase extraction of small amounts of norfloxacin in aqueous samples using 2-aminopyridine/graphene oxide nano-plates and visible and ultraviolet spectrophotometric measurements are used in biological samples. These systems include two phases, the aqueous donor phase and the acceptor phase of conjugated carbon nanomaterial. Aqueous phase extraction and norfloxacin adsorption were performed in two experimental steps. First, methanol acidic solvent was used and the adsorbed samples were submitted to Vis-UV spectrophotometry for further analysis. Extraction parameters in this method This cheap and simple method is compatible with most tool analysis methods. These parameters include extraction time, adsorption of organic solvent effect, adsorption time, shaking time, the volume of donor phases, and optimized surfactant effect, and analysis and measurement were performed under optimal conditions.

Quantification and Improvement of the Dynamics of Human Serum Albumin and Glycated Human Serum Albumin with Astaxanthin/Astaxanthin-Metal Ion Complexes: Physico-Chemical and Computational Approaches.

Glycated human serum albumin (gHSA) undergoes conformational changes and unfolding events caused by free radicals. The glycation process results in a reduced ability of albumin to act as an endogenous scavenger and transporter protein in diabetes mellitus type 2 (T2DM) patients. Astaxanthin (ASX) in native form and complexed with metal ions (Cu2+ and Zn2+) has been shown to prevent gHSA from experiencing unfolding events. Furthermore, it improves protein stability of gHSA and human serum albumin (HSA) as it is shown through molecular dynamics studies. In this study, the ASX/ASX-metal ion complexes were reacted with both HSA/gHSA and analyzed with electronic paramagnetic resonance (EPR) spectroscopy, rheology and zeta sizer (particle size and zeta potential) analysis, circular dichroism (CD) spectroscopy and UV-Vis spectrophotometer measurements, as well as molecular electrostatic potential (MEP) and molecular docking calculations. The addition of metal ions to ASX improves its ability to act as an antioxidant and both ASX or ASX-metal ion complexes maintain HSA and gHSA stability while performing their functions.

Simultaneous Determination of Paracetamol, Ibuprofen, and Caffeine in Tablets by Molecular Absorption Spectroscopy Combined with Classical Least Square Method.

In this paper, the classical least-squares (CLS) method with molecular absorption spectrophotometric measurement was used to determine simultaneously paracetamol (PAR), ibuprofen (IBU), and caffeine (CAF) in tablets. The absorbance spectra of the standard solutions and samples were measured over a wavelength from 220 to 300 nm with a 0.5 nm step. The concentration of PAR, IBU, and CAF in the sample solutions was calculated by using Visual Basic for Applications (VBA) and a program called CLS-Excel written in Microsoft Excel 2016. The method and the CLS-Excel program were tested on mixed standard laboratory samples with different PAR, IBU, and CAF concentration ratios, and they showed only small errors and a satisfying repeatability. An analytical procedure for tablets containing PAR, IBU, and CAF was developed. The reliability of the procedure was proved via the recovery and repeatability of the analysis results with an actual tablet sample and by comparing the mean contents of active substances in the tablets obtained from the analytical procedure with the HPLC method. The procedure is simple with a reduced cost compared with the HPLC standard method.

Comparison of two Genomic DNA Extraction Protocols from Single Dray Seed of Barley Crop

Modern plant breeding studies are largely based on plant genetic engineering programs. Extraction of DNA with high quality plays as a key factor in most of plant genetic Studies, therefore two different DNA extraction protocols based on CTAB buffer and SDS buffer were tested for the purpose of selecting the best DNA extraction protocol from dry seeds of nine variety of barely plant . Barley seeds were taken from Libyan seeds gene bank .After Barely samples were prepared DNA was extracted directly using CTAB and SDS solutions .The quality of extracted DNA was assessed by spectrophotometric measurements and gel electrophoresis system. The results of this study showed that purity of extracted DNA by CTAB method was clearly batter compared with SDS method. CTAB method seemed to be more effective for extracting DNA from barely dry seeds. High quality DNA obtained through use of CTAB method, while CTAB had overall better A260/A280 ratio (1.736-1.932). SDS method seemed to be not suitable for DNA extraction from dry seeds of barely crop.

Optical Characterization of Boron-doped ZnO nanostructures

Zinc oxide and Boron-doped zinc oxide (B-ZnO) thin films have been dip coated on glass substrates using Sol-Gel technique. The ZnO solution was prepared by using zinc acetate dihydrate (ZAD) as starting material. Ethanol and citric acid are used in the Sol-Gel process as solvent and solution stabilizer, respectively. Doping of boron is achieved by adding a proper molar ratio of Boric acid (H3BO3) solution to the final ZnO solvent. The optical properties of thin films were investigated using UV-vis spectrophotometer measurements. Transmittance of undoped ZnO films exhibits high values that are decreasing upon increasing the Boron concentration. We found that the index of refraction of undoped ZnO films demonstrates values ranging between 1.6 and 2.2 and increase as B concentration is increased and approximately match those of bulk ZnO. In addition, structural properties were investigated using XRD, SEM and EDAX techniques. Upon annealing, we found that the films exhibit a hexagonal structure and as B concentration increases the grain size increases and the strain decreases. Our results indicate that (B-ZnO) films could be used as seeded platforms for growing nanostructures using hydrothermal method.

Sol-silicate versus organic paints: Durability after outdoor and ultraviolet radiation exposures

Sol-silicate paints and polyvinyl acetate paints with similar red and green colour tones were applied to concrete and brick specimens and underwent either natural outdoor exposure in a marine setting for 12 months or accelerated ultraviolet radiation exposure (total exposure 4620 h). Chromatic changes were regularly monitored via spectrophotometer measurements. After exposure, physical, chemical, and mineralogical changes were evaluated using a multianalytical protocol based on stereomicroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and contact angle and peeling test measurements.After both tests, all the samples underwent colour changes whose intensity was independent of the type of substrate and type of exposure, being more related to the nature of the chromophore than to the nature of the base paint (organic or sol-silicate). After the outdoor test, the detachment of the pictorial layer was occurred in all the samples, more intensely in the sol-silicate painted brick mockups; this detachment process was related to salt precipitation-dissolution phenomena, mainly gypsum from marine aerosol, which causes effects that are more adverse when the adhesion between the paint and the substrate is weak.Compared to conventional organic paints, the use of sol-silicate paints in works of art in public spaces could meet the durability expectations of artists, always performing a prior evaluation focused to the selection of substrates that provide good adhesion and located in environments free from sources of salts.

Multicentric Standardization of Protocols for the Diagnosis of Human Mitochondrial Respiratory Chain Defects.

The quantification of mitochondrial respiratory chain (MRC) enzymatic activities is essential for diagnosis of a wide range of mitochondrial diseases, ranging from inherited defects to secondary dysfunctions. MRC lesion is frequently linked to extended cell damage through the generation of proton leak or oxidative stress, threatening organ viability and patient health. However, the intrinsic challenge of a methodological setup and the high variability in measuring MRC enzymatic activities represents a major obstacle for comparative analysis amongst institutions. To improve experimental and statistical robustness, seven Spanish centers with extensive experience in mitochondrial research and diagnosis joined to standardize common protocols for spectrophotometric MRC enzymatic measurements using minimum amounts of sample. Herein, we present the detailed protocols, reference ranges, tips and troubleshooting methods for experimental and analytical setups in different sample preparations and tissues that will allow an international standardization of common protocols for the diagnosis of MRC defects. Methodological standardization is a crucial step to obtain comparable reference ranges and international standards for laboratory assays to set the path for further diagnosis and research in the field of mitochondrial diseases.