Determination of D[C6F5CH2—Br] by the toluene carrier method

1980 ◽  
Vol 58 (18) ◽  
pp. 1906-1908 ◽  
Author(s):  
R. John Kominar ◽  
Michael J. Krech ◽  
Stanley James W. Price
Keyword(s):  
Arrhenius Equation ◽  
Parent Compound ◽  
Material Balance ◽  
Internal Standard ◽  
Standard Technique ◽  
The Other ◽  
Reasonable Estimate ◽  
First Order ◽  
A Value

The pyrolysis of C6F5CH2Br has been studied by the toluene carrier technique over the temperature range 727–800 °C. Rate constants are based on analysis for residual parent compound by gas chromatography using an internal standard technique. In selected runs a material balance of 100 ± 2% was obtained for bromine based on C6F5CH2Br plus HBr. Within the limits of the experimental technique the process appears to be first order and homogeneous. In addition to HBr the other major products of the thermal decomposition are C6F5CH3, (C6F5CH2)2, C6F5CH2CH2C6H5, and (C6H5CH2)2. The Arrhenius equation obtained is[Formula: see text]The log A value is very close to the value of 14.6 recommended by Benson and O'Neal for the decomposition of C6H5CH2Br. The activation energy, 225 ± 6 kJ mol−1, should be a reasonable estimate of D[C6F5CH2—Br].

Determination of total proteinogenic amino acids and taurine by pre-column derivatisation and UHPLC: Single Laboratory Validation, First Action 2019.09

2020 ◽  
Author(s):  
George Joseph ◽  
Asha Varughese ◽  
Ann Daniel
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Infant Formula ◽  
Retention Time ◽  
Sulfonic Acid ◽  
Internal Standard ◽  
The Other ◽  
Method Performance ◽  
Single Laboratory

Abstract Background A method has been developed and validated for selective, accurate and precise determination of total proteinogenic amino acids and taurine from Infant Formula and Adult/Pediatric Nutritional Formulas (powders, ready-to-feed liquids, and liquid concentrates). The method was reviewed by the AOAC INTERNATIONAL SPIFAN Expert Review Panel (ERP) during the 133rd AOAC Annual Meeting & Expo on September 7, 2019 in Denver, CO, USA and was recommended to First Action Official MethodsSM status. Objective The method involves protein hydrolysis to amino acids, a simple pre-column derivatisation of amino acids and separation of derivatised amino acids by UHPLC. The quantification of amino acids is performed by multi-point calibration using norvaline as the internal standard. The analytical method is capable of quantitative determination for 22 proteinogenic amino acids, but cannot be used to quantitate tryptophan, which is destroyed during the acid hydrolysis step. Asparagine is determined as aspartic acid and glutamine as glutamic acid. The cystine and cysteine are converted to S-2-carboxyethylthiocysteine (CYSx) and the derivative is separated from the other amino acids. Citrulline which is present in some matrices and it is separated from other amino acids is not included in the method performance evaluation in the single laboratory validation (SLV). Method The proposed method met all the performance requirement limits set in standard method performance requirements (SMPR) 2014.013 for total proteinogenic amino acids and taurine. The correlation coefficient of multi-point calibration was not less than 0.999 for any amino acids at any point in the SLV study confirming the validity of linear dynanic range (LDR) and linearity of the method. The individual amino acids in the chromatogram were identified by absolute retention time and relative retention time (RRT) with respect to the internal standard norvaline. There were no significant (S/N Ratio <10) interferences from the reagents or by-products of derivatisation and targeted matrices. The method demonstrated high selectivity. Result Accuracy of the method was validated using standard reference materials (NIST SRM 1869 and 1849a) and spike recovery studies. The amino acid results in the SRMs were within the ranges of Reference Mass Fraction Values. The accuracy of the method was corroboratively validated by spike recovery studies. The average spike recovery range between 93 to 107% ensure the accuracy of the method for amino acids and compliance to the AOAC SMPR 2014.013. Conclusions Precision data of the method demonstrate that it meets the stakeholder requirements as per the SMPR. The mean RSDr for all the amino acids for 17 matrices selected for the SLV were not more than 4%. The method is very sensitive and the LOQ can go down to approximately ten times lower than the SMPR requirements. The sensitivity of method is a direct reflection of its signal to noise ratio which ensures guaranteed method performance at the lower levels of amino acids in these matrices. Highlights Taurine (aminoethane sulfonic acid) unlike the other amino acids is a beta-sulfonic amino acid that is not used in protein synthesis but is found as a free amino acid in tissues. The acidic functional group (-COOH) in common amino acid is replaced with a sulfonic acid (-SO3H) group in Taurine. The method offers baseline separation of citrulline which is an alpha amino acid generally present in Infant Formula and Adult/Pediatric Nutritional products. The separation of citrulline eliminates the risk of interference of this compound with other amino acids. The method can also separate and quantitate hydroxyproline, an important component of collagen that is often used to quantitate collagen. The method is simple and does not include any proprietary chemicals or instruments and can be performed on any basic reverse phase UHPLC system with UV detection.

Gas-Liquid Chromatographic Determination of Pyridazinones in Technical Products and Formulations

1978 ◽  
Vol 61 (1) ◽  
pp. 161-163
Author(s):  
Giuseppe Cellerino ◽  
Mariarosa Re
Keyword(s):  
Internal Standard ◽  
Standard Technique ◽  
Chromatographic Determination ◽  
Gas Liquid Chromatography ◽  
Flame Ionization ◽  
Selective Detector ◽  
Liquid Chromatographic Determination ◽  
Liquid Chromatographic ◽  
Technical Products

Abstract Simultaneous determination of the active ingredient and of by-products in technical and formulated pyridazinones was rapidly performed by gas-liquid chromatography with complete resolution of all compounds. Quantitative determination by the internal standard technique is accurate and precise. The lower limit of detectability is 8 × 10–12 g/sec with a flame ionization detector and 1 × 10–12 g/sec with a nitrogen-phosphorus selective detector operating in the nitrogen mode.

Liquid Chromatographic Determination of Carbamazepine in Tablets

1988 ◽  
Vol 71 (3) ◽  
pp. 523-525 ◽  
Author(s):  
Ella S Walker
Keyword(s):  
Internal Standard ◽  
Standard Technique ◽  
Chromatographic Determination ◽  
Individual Values ◽  
Qualitative And Quantitative ◽  
Average Value ◽  
Liquid Chromatographic Method ◽  
Liquid Chromatographic Determination ◽  
Liquid Chromatographic

Abstract A simple and rapid liquid chromatographic method is described for the qualitative and quantitative determination of carbamazepine in tablet composites and individual tablets, using the internal standard technique. Analyses were performed on a C-18 reverse-phase column with tetrahydrofuran-methanol-water (8 + 37 + 55) as the mobile phase. A linear relationship was obtained between detector responses at 254 nm and amounts of carbamazepine injected ranging from 0.2 to 1.7 ng. The coefficient of variation for 10 consecutive injections of a standard preparation was 0.4%. Recoveries of carbamazepine from 100 and 200 mg tablets averaged 101.4 and 99.7%, respectively. Assay results for commercial tablets analyzed by the proposed method agreed favorably with those obtained by the method of USP XXI. The assay results for individual tablets indicated that deviations from the average value and the range of individual values are much wider with the compendial method than with the proposed method

Gas Chromatographic Methods for Determination of γ-BHC in Technical Emulsifiable Concentrates and Water-Dispersible Powder Formulations and in Lindane Shampoo and Lotion: Collaborative Study

1984 ◽  
Vol 67 (4) ◽  
pp. 834-837
Author(s):  
James W Miles ◽  
Dwight L Mount ◽  
◽  
T J Beckmann ◽  
S K Carrigan ◽  
...  
Keyword(s):  
Coefficient Of Variation ◽  
Collaborative Study ◽  
Internal Standard ◽  
The Other ◽  
Water Dispersible ◽  
Coefficients Of Variation ◽  
Aoac Method ◽  
Liquid Chromatographic ◽  
Gas Chromatographic Separation

Abstract Although the gas chromatographic separation of the isomers of BHC was demonstrated two decades ago, the present AOAC method of analysis of BHC for gamma-isomer (lindane) content is based on a separation carried out on a liquid chromatographic partition column. A method of analysis has been developed that uses an OV-210 column for separation of the gamma-isomer from the other isomers and impurities in technical BHC. Di-n-propyl phthalate was chosen as an internal standard. The same system allows quantitation of lindane in lotion and shampoo after these products are extracted with ethyl acetate-isooctane (1 + 4). The analytical methods were subjected to a collaborative trial with 10 laboratories. The coefficient of variation for technical BHC was 2.83%. For the water-dispersible powder and emulsifiable concentrate, the coefficients of variation were 2.89% and 4.62%, respectively. Coefficients of variation for 1% lindane lotion and shampoo were 4.36% and 11.92%, respectively. The method has been adopted official first action.

Separation of Vitamins D2 and D3 as Isotachysterols D2 and D3 by Gas-Liquid Chromatography

1968 ◽  
Vol 51 (4) ◽  
pp. 834-838
Author(s):  
A J Sheppard ◽  
Denis E Lacroix ◽  
A R Prosser
Keyword(s):  
Liquid Chromatography ◽  
Quantitative Determination ◽  
Infrared Absorption ◽  
Quantitative Measurement ◽  
Acetyl Chloride ◽  
Internal Standard ◽  
The Other ◽  
Gas Liquid Chromatography ◽  
Absorption Data

Abstract A method for the quantitative determination of 0.5—20 μg vitamins D2 and D3 by gas-liquid chromatography is described. Vitamins D2 and D3 are completely isomerized to their respective isotachysterol isomers by acetyl chloride as demonstrated by ultraviolet and infrared absorption data. Dihydrotachysterol D2, isotachysterol D2, and isotachysterol D3 are completely resolved with a 3% JXR on 100-120 mesh Gas Chrom Q column packing. Calibration studies show that each compound exhibited a characteristic dose-response plot. Therefore, one isomer cannot be used as a direct internal standard for the quantitative measurement of the other isomer.

scholarly journals A Liquid Chromatographic Method for Routine Analysis of 5-Mononucleotides in Pediatric Formulas

2010 ◽  
Vol 93 (3) ◽  
pp. 966-973 ◽  
Author(s):  
Brendon D Gill ◽  
Harvey E Indyk ◽  
Maureen C Kumar ◽  
Nathan K Sievwright ◽  
Merilyn Manley-Harris
Keyword(s):  
Bovine Milk ◽  
Internal Standard ◽  
Standard Technique ◽  
Gradient Elution ◽  
Hplc Method ◽  
Routine Analysis ◽  
Liquid Chromatographic Method ◽  
Sample Dissolution ◽  
Liquid Chromatographic

Abstract An RP-HPLC method for the routine determination of supplemented 5-mononucleotides (uridine 5-monophosphate, inosine 5-monophosphate, adenosine 5-monophosphate, guanosine 5-monophosphate, and cytidine 5-monophosphate) in pediatric formulas and milk products is described. Following sample dissolution, potential interferences were removed by anion-exchange SPE. Chromatographic analyses were performed using a C18 stationary phase with gradient elution, UV detection, and quantitation by an internal standard technique. A single-laboratory validation was performed, with recoveries of 92101 and repeatability RSDs of 1.02.3. The method was optimized for the rapid, routine analysis of nucleotide-supplemented bovine milk-based infant and follow-on formulas.

Simultaneous determination of trace elements in serum by energy-dispersive x-ray fluorescence spectrometry.

1984 ◽  
Vol 30 (8) ◽  
pp. 1300-1303 ◽  
Author(s):  
F Rastegar ◽  
E A Maier ◽  
R Heimburger ◽  
C Christophe ◽  
C Ruch ◽  
...  
Keyword(s):  
Analytical Procedure ◽  
Internal Standard ◽  
Detection Limits ◽  
The Other ◽  
Energy Dispersive ◽  
Statistical Distributions ◽  
Polypropylene Film ◽  
X Ray ◽  
Large Numbers

Abstract Energy-dispersive x-ray fluorescence is applied in the analysis of human serum to determine the concentrations of several elements simultaneously with minimal manipulation of the sample. The analytical procedure has been developed with standard sera, and standardization, detection limits, and reproducibility have been established. A 50-microL sample of diluted serum, to which an internal standard has been added, is deposited on a thin (4-microns thick) polypropylene film and analyzed by x-ray fluorescence. We report the statistical distributions of the concentrations of Fe, Cu, Zn, and Br obtained in the population (103 samples) studied, and report detection limits for the other 22 elements studied. The simplicity of the method, the high throughput, and the possibility of automating the measurements make this procedure suitable for screening large numbers of sera.

Determination of ΔHf2980(C6F5Br, g) from studies of the combustion of bromopentafluorobenzene in oxygen and calculation of D[C6F5 — Br]

1977 ◽  
Vol 55 (24) ◽  
pp. 4222-4226 ◽  
Author(s):  
Michael J. Krech ◽  
Stanley James W. Price ◽  
Henry J. Sapiano
Keyword(s):  
Material Balance ◽  
Combustion Method ◽  
Heat Of Formation ◽  
Molar Ratio ◽  
Direct Combustion ◽  
A Value ◽  
Fold Excess

The heat of formation of bromopentafluorobenzene has been determined through the use of the direct combustion method which has been applied to hexafluorobenzene, octafluorotoluene, and iodopentafluorobenzene. While a platinum lined bomb is normally used for these types of compounds a steel bomb had to be adopted in this work. The combustion of bromopentafluorobenzene in the steel bomb yields CO2, CF4, F2, Br2, and BrF3. With a ten-fold excess of oxygen, the average CO2 to CF4 molar ratio is 7.29 ± 0.07. A material balance was obtained for carbon, fluorine, and bromine. The value of ΔHf2980(C6F5Br, g) = −711.6 ± 16.7 kJ mol−1 (−170.1 ± 4.0 kcal mol−1) has been combined with ΔHf2980(C6F5, g) = −387.4 kJ mol−1 (−92.6 kcal mol−1) and ΔHf2980(Br, g) = 111.7 kJ mol−1 (26.7 kcal mol−1) to obtain a value for D[C6F5—Br] of 435.9 kJ mol−1 (104.2 kcal mol−1).

Multiple Internal Standard Technique for the Gas-Liquid Chromatographic Determination of Indole in Shrimp

1978 ◽  
Vol 61 (1) ◽  
pp. 136-138
Author(s):  
Walter F Staruszkiewicz ◽  
John F Bond
Keyword(s):  
Silica Gel ◽  
Room Temperature ◽  
Internal Standard ◽  
Standard Technique ◽  
Chromatographic Determination ◽  
Experimental Conditions ◽  
Liquid Chromatographic Determination ◽  
Standard Solution ◽  
Liquid Chromatographic

Abstract A multiple internal standard technique has been developed for the official first action gas-liquid chromatographic (GLC) method for determining indole in shrimp. The modification was developed because interfering GLC peaks are occasionally observed when 2-methylindole is used as the internal standard. An internal standard solution containing 1-methylindole, 2- methylindole, and diphenylamine was added to extracts of shrimp before silica gel cleanup and separation by GLC. All of the compounds were quantitatively recovered and were separated on the GLC column under identical experimental conditions. Extracts of acceptable shrimp to which indole was added at levels of 3–10 μg/ 100 g and extracts of decomposed shrimp were stored at room temperature for 2 weeks. Average and maximum changes (μg indole/100 g) during storage were, respectively, for each internal standard: average 0.6, 0.4, and 1.1; maximum 1.7, 0.9, and 2.9.

A Rapid Method for the Determination of Vitamin D3 in Milk and Infant Formula by Liquid Chromatography/Tandem Mass Spectrometry

2015 ◽  
Vol 98 (2) ◽  
pp. 431-435 ◽  
Author(s):  
Brendon D Gill ◽  
Xiangjun Zhu ◽  
Harvey E Indyk
Keyword(s):  
Infant Formula ◽  
Rapid Method ◽  
Vitamin D3 ◽  
Internal Standard ◽  
Standard Technique ◽  
Compliance Testing ◽  
High Throughput Method ◽  
Liquid Chromatography Tandem Mass ◽  
Sensitivity And Selectivity

Abstract A rapid method for the determination of vitamin D3 applicable to milk and infant formula products is described. Samples are saponified at hightemperature, and lipophilic components are extractedinto isooctane in a single tube. Vitamin D3 is derivatized with 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) to form a Diels–Alder adduct, which is re-extracted into a small volume of acetonitrile and analyzed by UHPLC-MS/MS with quantification accomplished by an internal standard technique utilizing deuterium-labeled vitamin D3. The analysis of vitamin D3 as the PTAD adduct offers a significant increase in sensitivity and selectivity, allowing for rapid sample preparation and short chromatographic run times. The method was shown to be accurate, with spike recoveries of 94.7–104.7% and no statistical bias against both a certified reference material (P = 0.37, α = 0.05) and a reference LC-UV analytical method (P = 0.09, α = 0.05). Acceptableprecision was confirmed with a repeatability RSD of 1.4–4.5% and corresponding HorRat values of 0.1–0.2. This high-throughput method is ideal for routine compliance testing, with more than 50 samples/day achievable by a single analyst.

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