Correlation Coefficients Of Calibration Curves Research Articles

Self-absorption correction method based on intensity self-calibration of doublet lines.

The self-absorption effect in an optically thick plasma seriously affects the spectral line intensity and the measurement accuracy of laser-induced breakdown spectroscopy (LIBS). In this work, a self-absorption correction method based on intensity self-calibration of doublet lines belonging to the same multiplet is proposed. The K/Δλ0 parameter and self-absorption coefficient (SA) of the doublet lines of the analytical element can be calculated based on the measured actual lines intensity ratio and the K parameters ratio. Compared with the generally applied self-absorption correction methods, this method can effectively reduce the influence of laser energy and plasma plume fluctuations and the non-uniformity distribution of the element in the plasma, and is independent of the availability of Stark broadening coefficients. So it has obvious advantages of high computation efficiency, high analysis accuracy and good applicability. Univariate quantitative analysis results of aluminum (Al) show that the correlation coefficient of calibration curves and the measurement accuracy of elemental content have been significantly improved with the self-absorption correction.

Modification of the Method for the Determination of Zinc Content in Insulins by Atomic Absorption Spectrometry

Scientific relevance. Zinc quantification in insulin active substances and preparations by atomic absorption spectrometry requires a sample preparation procedure using hydrochloric acid, a narcotic and psychotropic precursor. The exclusion of precursors from laboratory practice significantly reduces labour costs during analysis.Aim. This study aimed to modify the pharmacopoeial method for quantifying zinc in insulins with a view to eliminating drug precursors and to evaluate the applicability of the modified method across different insulin preparations.Materials and methods. The study considered insulin active substances and preparations of various types, dosage forms, and strengths. Zinc content determination involved using an Agilent 240FS atomic absorption spectrometer at a characteristic wavelength of 213.86 nm.Results. The authors selected the conditions for elemental analysis (nitric acid concentration, monochromator slit width, and flame stabilisation time) corresponding to the pharmacopoeial requirements for quantifying zinc in insulins (RSD ≤1.4%, standard zinc solution with a concentration of 0.8 mg/dm3, and calibration curve correlation coefficient ≥0.99). The study compared zinc content measurements in the studied insulin samples with hydrochloric acid or nitric acid as a solvent; it did not reveal any significant differences between the results obtained by the pharmacopoeial method and the modified method.Conclusions. The modified method enables analysts to quantify zinc in insulin preparations in various dosage forms without drug precursors.

Analysis of Phenolic Compounds in Nicotiana tabacum Based on Aqueous Two-Phase Extraction Coupled with Liquid Chromatography

Background: Phenolic compounds in Nicotiana tabacum L. have anti-tumor, antibacterial, anti-inflammatory, and other pharmacological effects. Therefore, either to optimize the utilization of plant resources or to reduce the physiological harm caused by cigarette, it is necessary to separate and analyze the phenolic compounds in Nicotiana tabacum. 
 Aim: To develop a protocol for extraction and analysis of phenolic compounds in Nicotiana tabacum. The method based on aqueous two-phase extraction (ATP) should provide a solid experimental basis for future large-scale medical industrial extraction.
 Results: Five of phenolic compounds in Nicotiana tabacum including catechol, caffeic acid, coumarin, rutin, and quercetin were extracted with the developed ATP method and analyzed by the optimized liquid chromatography method simultaneously. In the concentration range of 10-200 µg/mL, the linear correlation coefficients of calibration curve for five compounds were all greater than 0.999. The developed ATP extraction method employed 70% acetonitrile water solution as the extractant. The ammonium sulphate was selected as the preferred phase separation salt. The extraction efficiencies of five phenolic compounds were all more than 90%. In concrete sample, the concentrations of five compounds were determined based on acetonitrile/salt ATPE system,
 Conclusion: Analysis of phenolic compounds in Nicotiana tabacum was achieved based on acetonitrile/ammonium sulphate ATP extraction coupled with liquid chromatography. The developed ATP extraction protocol employed 70% acetonitrile water solution as the extractant. The ammonium sulphate was selected as the preferred phase separation salt. The accuracy and precision were satisfied. The protocol developed in this study is expected to be applied in medical industry.

Improvement of analytical method for three azo dyes in processed milk and cheese using HPLC-PDA.

This study aims to develop and validate a method for simultaneously measuring three azo dyes (azorubine, brilliant black BN, lithol rubine BK) not designated in Korea. The HPLC-PDA analysis method was validated based on the ICH guidelines, and the color stability was evaluated. The milk and cheese samples were spiked with azo dyes, the correlation coefficient of calibration curve ranged from 0.999 to 1.000 and the recovery rates of azo dyes were 98.81∼115.94%, with RSD of 0.08∼3.71%. The LOD and the LOQ in milk and cheese ranged from 1.14 to 1.73μg/mL and 3.46 to 5.25μg/mL, respectively. In addition, the expanded uncertainties of the measurements ranged from 3.3421 to 3.8146%. The azo dyes appeared to be color stable for more than 14days. The results indicate that this analytical method is suitable for extracting and analyzing azo dyes in milk and cheese samples, which are not permitted in Korea.

An LC-MS/MS method for the simultaneous determination of 18 antibacterial drugs in human plasma and its application in therapeutic drug monitoring.

Antimicrobial resistance (AMR) is a major threat to global health due to the wide use of antibacterial drugs. Multiple studies show that the pharmacokinetic/pharmacodynamic (PK/PD) studies of antibiotics are an approach to prevent/delay AMR. The pharmacokinetic parameters of antibiotics are the basis of PK/PD studies, and therapeutic drug monitoring (TDM) is the key method to obtain pharmacokinetic information. We developed an ultra-performance liquid chromatography-tandem mass spectrometry to determine 18 antibacterial drugs (piperacillin, cefazolin, cefuroxime, cefoperazone, ceftriaxone, cefepime, aztreonam, meropenem, imipenem, levofloxacin, moxifloxacin, azithromycin, clindamycin, tigecycline, linezolid, vancomycin, voriconazole and caspofungin) in human plasma for practical clinical usage. Samples were prepared using protein precipitation with methanol. Chromatographic separation was accomplished in 6min on a BEH C18 column (2.1 × 100mm, 1.7µm) using a gradient elution of acetonitrile and 0.1% formic acid in water at a flow rate of 0.3ml/min. The electrospray ionization source interface was operated in the positive and negative ionization modes. Inter- and intra-day precision, accuracy, recovery, matrix effect, and stability were validated according to the Food and Drug Administration guidance. The correlation coefficients of calibration curves were all greater than 0.99. The accuracies of the 18 antibacterial drugs ranged from 89.1% to 112.4%. The intra-day precision of the analytes ranged from 1.4% to 9.3% and the inter-day precision from 2.1% to 7.2%. The matrix effects ranged from 93.1% to 105.8% and the extraction recoveries ranged between 90.1% and 109.2%. The stabilities of the 18 antibacterial drugs in plasma were evaluated by analyzing three different concentrations following storage at three storage conditions. All samples displayed variations less than 15.0%. The validated method was successfully applied to routine clinical TDM for 231 samples.

Determination of polycyclic aromatic hydrocarbons in water using dispersive liquid-liquid microextraction-gas chromatography-mass spectrometric

For the extraction of polycyclic aromatic hydrocarbons (PAHs) from water samples, a new sample preparation approach based on dispersive liquid-liquid microextraction (DLLME) was developed. In this procedure, a water sample was injected with a mixture of carbon tetrachloride, CCl4 (extraction solvent), and acetone (disperser solvent) to generate an emulsion in which the PAHs were extracted into fine droplets of extraction solvent. The impacts of several extraction parameters were explored, including extraction solvent type, disperser solvent type, extraction solvent volume, and disperser solvent volume. For phenanthrene and fluoranthene, the calibration curve correlation coefficient (r2) was 0.9993 and 0.9973, respectively. For phenanthrene and fluoranthene, the limits of detection (LODs) were 0.0008 g/mL and 0.0006 g/mL, respectively. For phenanthrene and fluoranthene, the relative standard deviations (RSDs) were 10.69 percent and 9.72 percent, respectively. The analyte recovery rates ranged from 100.5 to 107.8%. Phenanthrene and fluoranthene were discovered in the samples.

Coated Blade Spray with a Barrier: Improving Negative Electrospray Ionization and Sample Preparation.

Substrate-based electrospray ionization (ESI) techniques like paper, wooden tip, plastic tip, and metal-needle-based spray suffer from corona discharge, high background noise, and unstable spray in negative ionization mode, especially for the analysis of complex biological matrices, such as blood and urine. Coated blade spray coupled with mass spectrometry (CBS-MS) combines solid-phase microextraction's (SPME) efficient sample clean-up and enrichment and ambient MS's fast analysis and has proven to be an appealing alternative tool for the fast screening of target analytes in complex matrices. This paper documents the development of a new CBS blade design that features a barrier at the far end of the ESI tip. The findings of this work show that the addition of this simple barrier enabled the total RSD% to be reduced to less than 10% for sample preparation, ionization, and the MS detection of several drugs of abuse in negative mode, without compensation using internal standards. The improved stability of ESI in negative mode was investigated by observing the ESI process with a microscope camera and testing via CBS-MS. The new design was applied for the analysis of three drugs of abuse in urine, with the calibration curve correlation coefficient (R2 ≥ 0.9997) being calculated without the use of internal standards. The overall RSD% of the peak area for one compound in 42 samples was 6.9%, which highlights the method's incredible reproducibility compared to other ambient MS techniques for analyzing real samples. The CBS device with a barrier was also applied for the on-blade sampling of 14 drugs of abuse in 20 μL of plasma spot in positive ionization mode. The results of these tests yielded a calibration curve correlation coefficient of R2 ≥ 0.9883 and limits of quantification (LOQs) between 0.25 and 25 ng/mL. The obtained results provide guidance on CBS device design optimization and the effective automation of the protocol.

Development and validation of a single HPLC method for the determination of thirteen pharmaceuticals in bulk and tablet dosage form

The aim of this study was to develop and validate a high performance liquid chromatography (HPLC) method for the determination of thirteen selected pharmaceutical compounds (metformin, amoxicillin, chloroquine, theophylline, trimethoprim, caffeine, norfloxacin, ciprofloxacin, acetylsalicylic acid, doxycycline hyclate, metronidazole, albendazole and cloxacillin) in bulk and tablet dosage form. Chromatographic separation using a Kromasil C18 column, gradient elution with aqueous formic acid (0.1%), methanol and acetonitrile, a UV absorption wavelength of 250 nm and a mobile phase flow rate of 1 mL/min over a 22 min run time was optimized for complete separation of the selected target compounds. The method was validated and results for: linearity, precision, sensitivity, accuracy, specificity, suitability and method robustness were obtained and met the ICH guidelines. Calibration curve correlation coefficients ranged from 0.9985-0.9998 and the percentage relative standard deviations for repeated analysis was below 5%, indicating acceptable method precision. The limits of detection (LODs) and quantification (LOQs) ranged from 0.020-0.27 µg/L and 0.080-0.91 µg/L, respectively. The accuracy study yielded recoveries in the ranges 86.0-102% for pure compounds and 90.9-106% for compounds in tablet dosage form. The method is robust for small or deliberate changes to the chromatographic parameters and found to be appropriate for analysis of tablets for the determination of the thirteen pharmaceuticals.
 
 KEY WORDS: Pharmaceuticals, Bulk determination, Tablet dosage, High performance liquid chromatography, Method development, ICH guidelines
 
 Bull. Chem. Soc. Ethiop. 2021, 35(1), 17-31.
 DOI: https://dx.doi.org/10.4314/bcse.v35i1.2

Headspace-Gas Chromatography Method for Determination of Formaldehyde Content in Wastewater

Through the use of headspace-gas chromatography, the sensitivity and detection limit of formaldehyde content in wastewater obtained by the standard curve method and the standard addition method are compared in order to obtain the best detection method. The results show that the calibration curve correlation of the standard insertion method for testing the formaldehyde content in wastewater is 0.9991, the detection limit of the method is 0.18 mg/L, and the lower limit of determination is 0.69 mg/L. Excellent standard curve method; this method is used for samples with low, medium and high concentrations. The range of standard recovery rate calculated is 85.1%~112.9%, the relative standard deviation in the laboratory is 2.7%~ 6.3%, which is also better than the standard curve method and meets the test requirements. This method is easy to operate, high sensitivity, and low detection limit for the determination of formaldehyde in wastewater, which meets the requirements of analysis and testing.

Determination of Aerosol Metals Pollutants in Falling Dust in Benghazi City, Libya

The aim of this study is to determine the levels of concentrations of selected heavy metals of aerosol metals contamination in falling dust at different roadsides in Benghazi city. In order to do that, measuring the concentrations of the selected aerosol metals by using vacuum pump and measured using atomic absorption spectroscopy (AAS) technique. Six composite samples were collected along roadsides and each sample was represented average of five samples which collected from that particular area. The concentrations of aerosol metals of each site were based on density of traffic road and type of industrial activities, also to the number of population. Each measured sample was replicated three times to obtain representative and accurate values. Also, a statistical analysis including mean and standard deviation were carried out. Correlation coefficient of calibration curves of measured aerosol metals was shown a good response, where the R2 value was ranged between 0.994 to 0.999. The range of concentrations of the studied aerosol metals were varied as following: Cobalt (90-344 mg/kg), iron (120-383 mg/kg), lead (153-740 mg/kg), zinc (78-468.7 mg/kg), copper (80-180 mg/kg), selenium (40-133 mg/kg), cadmium (90344 mg/kg), potassium (318-2932 mg/kg), sodium (587.5-3006 mg/kg), calcium (286.6-1185.7 mg/kg) and magnesium (65-325.8 mg/kg). A significant positive correlation was shown between each pairs of measured elements Pb/Zn, Pb/Co, Pb/Cu, Pb/Se, Zn/Co and Zn/Cu.

Simple liquid chromatography-electrospray ionization ion trap mass spectrometry method for the quantification of galacto-oxylipin arabidopsides in plant samples

A simple and sensitive method to quantify five different arabidopsides by HPLC—ion trap mass spectrometry in complex plant samples was developed and validated. Arabidopsides are oxidized galactolipids first described in Arabidopsis thaliana but also produced by other plant species under stress conditions. External calibration was performed using arabidopsides purified from freeze-thawed Arabidopsis leaves. Lipids were extracted and pre-purified on an SPE silica column before HPLC–MS analysis. Arabidopsides were separated on a C18 column using a gradient of mQ water and acetonitrile:mQ water (85:15) supplemented with formic acid (0.2%) and ammonium formate (12 mM). The method was validated according to European commission decision 2002/657/CE. LOD, LOQ, linearity, intra-day and inter-day precision and accuracy, selectivity, matrix effects and recoveries were determined for the five metabolites. The established method is highly selective in a complex plant matrix. LOD and LOQ were, respectively, in the range 0.098–0.78 and 0.64–1.56 µM, allowing the arabidopside quantification from 25.6–62.4 nmol/g fresh weight. Calibration curve correlation coefficients were higher than 0.997. Matrix effects ranged from -2.09% to 6.10% and recoveries between 70.7% and 109%. The method was successfully applied to complex plant matrixes: Arabidopsis thaliana and Nasturtium officinale.

Determination of melatonin in rat plasma by high performance liquid chromatography with electrochemical detection

Melatonin ( 5-methoxy-N-acetyltryptamine ) plays a role in a number of distinct physiological functions. We have developed a convenient high performance liquid chromatography assay with electrochemical detection ( HPLC / ECD ) for the accurate determination of melatonin in biological samples. This assay involves direct addition of rat plasma to acetonitrile for simultaneous protein precipitation and melatonin extraction. The assay was validated by addition of melatonin to rat plasma with a recovery rate between 92 and 99 %. The correlation coefficient of calibration curve was 1.000. The relative standard deviations for intraday and interday analyses were 1.5-2.2 % and 3.5-5.0 %, respectively. Melatonin clearance rate of biological samples were determined by this method. Melatonin ( 0.67 mg / kg ) were given to Sprague Dawley rats by femoral vein injection. The melatonin concentrations were determined by HPLC / ECD at 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 hrs. The concentrations were reached the peak levels at 0.5-1.0 hrs and cleared after 3.0 hrs. The concentrations of melatonin were 102.8 ± 24.3, 51.5 ± 13.0, 30.2 ± 7.1, 22.2 ± 7.2, 20.4 ± 9.8 and 17.9 ± 8.1 nM ( mean ± S.E.M., n = 8 ) at 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 hrs, respectively. This HPLC / ECD method can be useful in its application to biomedical studies of melatonin.

A simple and rapid LC-MS/MS method for the simultaneous determination of eight antipsychotics in human serum, and its application to therapeutic drug monitoring

A simple and rapid liquid chromatography/tandem mass spectrometry (LC-MS/MS) method was developed and used to determine eight antipsychotics (aripiprazole, clozapine, haloperidol, olanzapine, paliperidone, quetiapine, risperidone, and ziprasidone) in human serum for practical clinical usage. Stable isotope-labeled internal standards were used for all drugs to compensate for method variability, including matrix effects, ion extraction and ionization variations. Samples were prepared by simple protein precipitation with methanol. Chromatographic separation was accomplished in less than 3.3 min on a KINTEX C18 column (50 mm × 3.0 mm, 5 μm) using a gradient elution of 2 mM aqueous ammonium formate and methanol at a flow rate of 0.5 mL/min. Quantification was performed by multiple reaction monitoring (MRM) in the positive mode. The method was fully validated according to the latest recommendations of international guidelines. The correlation coefficients of calibration curves were all greater than 0.9945. Internal standard-normalized matrix effects ranged from 96.3% to 115%, and extraction recoveries were between 88.1% and 107%. Coefficients of variation ranged from 1.82 − 13.5% for intra-day precision, 5.69–14.7% for inter-day precision, and the relative error for accuracy did not exceed ± 13.5% for any analyte. The method was successfully applied to routine clinical therapeutic drug monitoring for 2,173 samples.

Gas Chromatography Detection Protocol of Short-chain Fatty Acids in Mice Feces.

Short-chain fatty acids (SCFAs), which are formed mainly by bacteria fermenting undigested carbohydrates in the colon, they are based on the number of carbon atoms in the carbon chain. Organic fatty acids with less than 6 carbon atoms are called short-chain fatty acids. SCFAs are closely related to various aspects of the human body, so more and more researchers concentrate on SCFAs. This protocol describes, a direct injection gas chromatography detection method with a pretreatment method for extracting SCFA from mice feces by combining acidification. The corresponding sample limit of quantization (LOQ) and limit of detection (LOD) are 0.8-1.0 mg/L and 0.5-0.8 mg/L, respectively. The correlation coefficient of calibration curve is greater than 0.999. The recovery rate of the spiked standard is 80%-102%. This method can be used to analyze and determine SCFAs in mice feces. Therefore, this is an economical, effective and reproducible method for SCFAs measurement in mice samples.

Determination of Aerosol Metals Pollutants in Falling Dust in Benghazi City, Libya

The aim of this study is to determine the concentrations of selected aerosol metals in falling dust at different roadsides in Benghazi city. In order to do that, Flame atomic absorption spectroscopy (FAAS) technique has used to quantitative the areoles metals. Six composite samples were collected along roadsides in Benghazi city and each composite sample was represented average of five samples. The concentrations of aerosol metals of each site were based on density of traffic road, type of industrial activities and the number of population. Each measured sample was replicated three times to obtain representative and accurate values. Also, a statistical analysis including mean and standard deviation was carried out. Correlation coefficient of calibration curves of slandered selected metals was shown a good response, where the R2 value was ranged between 0.994 to 0.999. The range of concentrations of the aerosol metals were varied as following: Cobalt (90 - 344 mg/kg), iron (120 - 383 mg/kg), lead (153 - 740 mg/kg), zinc (78 - 468.7 mg/kg), copper (80 - 180 mg/kg), selenium (40 - 133 mg/kg), cadmium (90,344 mg/kg), potassium (318 - 2932 mg/kg), sodium (587.5 - 3006 mg/kg), calcium (286.6 - 1185.7 mg/kg) and magnesium (65 - 325.8 mg/kg). A significant positive correlation was shown between each pair of measured elements Pb/Zn, Pb/Co, Pb/Cu, Pb/Se, Zn/Co and Zn/Cu.

Spectrofluorometric determination of L-tryptophan in canary (Canarium indicum L.) seed protein hydrolysate

Canary (Canarium indicum L.) is an indigenous plant of Indonesia, which mainly grows in the eastern part of Indonesia, especially in the Maluku, North Sulawesi, and Seram islands. We believe that no scientific reports have been conducted about L-tryptophan content in Canarium indicum. Therefore, this study was conducted to determine the presence and quantitate the aromatic amino acid (L-tryptophan) in the canary protein hydrolysate by the spectrofluorometric method. The protein hydrolysate was prepared by two hydrolysis methods, enzymatic and alkaline hydrolysis. L-tryptophan can be differentiated from tyrosine directly without using any reagent by excitation of the sample at 295 nm in order to avoid tyrosine emission. The equation of calibration curve correlation using standard in the range 0.5-5 ppm was y = 6632.3x - 845.42 and correlation coefficient of 0.9997, while the coefficient of variance in linear regression was 1.29%. The detection limit and quantification limit obtained were 0.116 ppm and 0.35 ppm respectively. The recoveries of the accuracy test were obtained in the range of 95-96%. The relative standard deviation of intra-assay precision tests were obtained in the range of 0.5-1.8%, while the intermediate precision in the range of 2.18-3.74%. L-tryptophan was detected in all samples (papain, pepsin, and alkaline hydrolysate), with concentrations 5.6, 5 and 1.53 mg/100mg of protein respectively. The used fluorometric method complied with the validation requirements and can be used to analyze L-tryptophan in samples containing tyrosine without overlapping of spectra and without the use of any specific reagent.

Application of high-surface-area graphitized carbon black with primary secondary amine as an alternative quick, easy, cheap, effective, rugged, and safe cleanup material for pesticide multi-residue analysis in spinach.

A multi-residue method has been developed and validated to determine 46 pesticides in spinach using liquid chromatography tandem mass spectrometry. The method is based on modified quick, easy, cheap, effective, rugged, and safe sample preparation, where high-surface-area graphitized carbon black was used first as sorbent material in the dispersive solid-phase extraction. The method was compared with the quick, easy, cheap, effective, rugged, and safe method. The morphology, surface area, pore size, and pore volume of the sorbent was determined. The results obtained show that the sorbent consists of high surface area (233m2 /g) and large pore volume (1.5cm3 /g). The calibration curve correlation coefficient (R2 ) of the method was at least 0.99. The average recoveries ranged from 74 to 116%, and limits of detection and quantification from 0.0001 to 0.002mg/kg and from 0.0002 to 0.005mg/kg, respectively. Using the method, the pesticides exhibited low matrix effect (<20%), except for nicosulfuron (29.86%), methomyl (26.77%), and flufenoxuron (24.65%). The method showed better potential to remove pigments than the quick, easy, cheap, effective, rugged, and safe method. It is demonstrated that the proposed method could be useful alternative for sample preparation of spinach and other matrices in future.

Evaluation of Sequential-SBSE and TF-SPME Extraction Techniques Prior to GC-TOFMS for the Analysis of Flavor Volatiles in Beer

Sequential-Stir Bar Sorptive Extraction (Seq-SBSE) was investigated as a technique for the extraction and concentration of volatiles in beer prior to gas chromatography–time-of-flight mass spectrometry (GC–TOFMS) analysis for standard solutions prepared in an imitation beer solvent. Twenty-seven beer analytes across a range of polarities (Ko/w’s) were investigated. The technique provided acceptable quantitation for most of the 27 analytes investigated, but calibration curves for five of the most polar analytes were nonlinear. Thin Film SPME (TF-SPME) sample preparation, which has recently been shown to provide quantitative extraction of polar analytes, was compared to Seq-SBSE results for the standard solutions. TF-SPME provided linear calibration curves for all 27 analytes. To compare test precision, a commercial sample of beer was analyzed in triplicate by both techniques. Eighty-five analytes were detected by Seq-SBSE with an average percentage of relative standard deviation (%RSD) of 9.7% and 95 analytes were detected by TF-SPME with an average %RSD of 8.9%. Triplicate samples from three brands of commercial beers at the end of shelf life were analyzed. Ten potential off-flavor chemicals analyzed by TF-SPME were subjected to principal component analysis. Examination of principal component analysis (PCA) loadings results showed the most significant concentration differences in off-flavor chemicals in the different brands occurred with E-2-nonenal, 3-methyl-2-butene-1-thiol, and vinyl guaiacol. Studies showed that some analytes showed better detection sensitivity by Seq-SBSE, while other analytes were detected with higher sensitivity by TF-SPME. Linear least squares correlation coefficients for calibration curves were higher for Seq-SBSE except for highly polar volatiles, while TF-SPME was able to quantitatively detect more chemicals including highly polar ones. TF-SPME appears to be an excellent supplemental technique for the analysis of beer volatiles.

A Novel Stress Indicating RP-HPLC Method Development and Validation for the Simultaneous Estimation of Velpatasvir and Sofosbuvir in Bulk and Its Tablet Dosage Form

Aim: The objective of the study was simplest, accurate, precise and robust reversed phase high performance liquid chromatographic (RP-HPLC) method was developed for the estimation of Velpatasvir (VEL) and Sofosbuvir (SOF) in the bulk and its tablet dosage form.&#x0D; Study Design: The Quantitative and Qualitative estimation and designed forced degradation study of Velpatasvir &amp; Sofosbuvir by RP-HPLC.&#x0D; Place and Duration of Study: The study was carried at Santhiram College of Pharmacy and time taken 4 months.&#x0D; Method: The method was attained by used Waters( 5µm, C18 250 x 4.6 mm) column with mobile phase consists of 0.5 mM disodium hydrogen phosphate buffer pH adjusted to 6.5, with Orthophosphoric acid and Methanol in the ratio of 78:22 v/v, a flow rate of 1.0 mL/min and ultraviolet detection at 285 nm.&#x0D; Results: The method was validated as per ICH guidelines with different parameters, the mean retention times of VEL and SOF were found to be 2.8 &amp; 4.7 min respectively. The resolution between VEL and SOF was found to be 10.66. The Correlation coefficients for calibration curves within the detection range of 32.5 - 97.5 and 125 - 375 µg/mL were 0.999 for VEL and SOF respectively. The LOD and LOQ for VEL and SOF were found to be 0.0068-0.029 µg/mL and 0.104-0.342 µg/mL respectively.&#x0D; Conclusion: The results were indicated that the developed method was used for the routine analysis of VEL &amp; SOF combined form in bulk and its commercial formulation. To the best of our knowledge, there was no method of RP-HPLC for the determination of VEL alone or in combination with SOF molecule.

Resonance/non-resonance doublet-based self-absorption-free LIBS for quantitative analysis with a wide measurement range.

A resonance/non-resonance, doublet-based, self-absorption-free, laser-induced breakdown spectroscopy (SAF-LIBS) technique is proposed for greatly expanding the measurement range of quantitative elemental analysis by using a quasi-optically thin line. The quasi-optically thin spectral line is obtained by matching the measured doublet atomic lines' intensity ratios with the theoretical one, and the applicable measurement range is expanded by utilizing the resonance and non-resonance lines. The specific calibration process consists of two parts: the nonlinear LIBS calibration and the linear SAF-LIBS calibration. For quantitative measurements, the approximate content of the unknown sample is determined first by using the LIBS calibration curve, and then the SAF-LIBS spectra and the resonance or non-resonance calibration curve that corresponds to the predetermined content are used for further implementing the quantitative analysis. Univariate quantitative analysis results of Cu show that this resonance/non-resonance doublet-based SAF-LIBS technique not only captures the quasi-optically thin spectral line in a wide range of elemental content, but also possesses high correlation coefficients of calibration curves, small relative errors of measurement and low limits of detection. The applicability and limitations of this technique are also discussed, and the evolution as well as the related major determinants of self-absorption are analyzed by taking advantage of the spatial-temporal evolution images of plasma emissivity.