A liquid chromatographic method for analysis of all-rac-alpha-tocopheryl acetate and retinyl palmitate in medical food using matrix solid-phase dispersion in conjunction with a zero reference material as a method development tool

A liquid chromatographic method is described for analysis of all-rac-alpha-tocopheryl acetate and retinyl palmitate in medical food. The vitamins are extracted from medical food without saponification by matrix solid-phase dispersion and chromatographed by normal-phase chromatography with fluorescence detection. Retinyl palmitate and all-rac-alpha-tocopheryl acetate are quantitated isocratically with a mobile phase of 0.125% (v/v) and 0.5% (v/v) isopropyl alcohol in hexane, respectively. Results compared favorably with label declarations on retail medical foods. Recoveries determined on an analyte-fortified zero reference material for a milk-based medical food averaged 98.3% (n = 25) for retinyl palmitate spikes and 95.7% (n = 25) for all-rac-alpha-tocopheryl acetate spikes. Five concentrations were examined for each analyte, and results were linear (r2 = 0.995 for retinyl palmitate and 0.9998 for all-rac-alpha-tocopheryl acetate) over the concentration range examined, with coefficients of variation in the range 0.81-4.22%. The method provides a rapid, specific, and easily controlled assay for analysis of retinyl palmitate and all-rac-alpha-tocopheryl acetate in fortified medical foods.     

Determination of retinyl palmitate and total vitamin A content in liver and liver-based ready-to-eat foods.

The determination of retinyl palmitate and total vitamin A in liver and liver-based ready-to-eat foods is described. The method is very simple as sample preparation is minimal, and the isocratic elution of the C18 column with pure methanol does not necessitate a sophisticated instrumental set-up. The method is accurate with high recoveries (100.6 +/- 9.3%, mean +/- S.D., n = 23), and precise with within-day and between-day coefficients of variation of less than 5.5% (n = 13) and less than 16% (n = 6), respectively.     

Measurement compatibility in size-exclusion chromatography. An intercomparison with a candidate BCR poly(vinyl acetate) reference material

A carefully controlled interlaboratory comparison of analyses by size exclusion chromatography of a poly(vinyl acetate) whole polymer showed that compatible measurements could be made of the molar mass distribution. The characterized sample is available as a Community Bureau of Reference (BCR) test material.     

The possibility of using beef tallow biodiesel as a viscosity reference material

This study analyses the possibility of using beef tallow biodiesel transesterified with ethanol, provided by Universidade Federal Fluminense, as a viscosity reference material for biodiesels. The quantity viscosity was measured with capillary viscometers, according to Brazilian standards, in a temperature range between 20 °C and 40 °C for characterisation, and at 40 °C for homogeneity, in short-term stability (90 days) and long-term stability (450 days). Thirty-nine samples were stored, 9 at 45 °C, 6 at 4 °C and 24 at 20 °C. The behaviour of viscosity is analysed considering the estimated uncertainty of measurements for characterisation, homogeneity and stability. The reason to study a transesterified biofuel with ethanol lies in the fact that it is easy to produce this fluid from sugarcane in Brazil.     

Determination of retinyl palmitate (vitamin A) in fortified fluid milk by liquid chromatography: collaborative study

A liquid chromatographic (LC) method was developed for fast and simple measurement of retinyl palmitate (vitamin A) in fortified milk. Retinyl acetate internal standard was added to a test portion of milk followed by extraction into hexane. The hexane extract was analyzed by LC using a normal-phase silica gel column equilibrated with mobile phase (conditioned hexane-isopropanol, 99.85 + 0.15, v/v) about 1 h before injections. The retinyl palmitate concentration was calculated by using a relative response factor determined with calibration standards. In the collaborative study, 11 laboratories analyzed 13 pairs of fluid milk materials in blind duplicate. Twelve of the materials were composed of skim milk (< 0.5% fat), 1% fat milk, 2% fat milk, and 1% fat chocolate milk. Each material was fortified at 3 concentrations of retinyl palmitate of approximately 581 microg/L (1000 IU/qt), 1163 microg/L (2000 IU/qt), and 2236 microg/L (4000 IU/qt). The 13th material, unfortified skim milk, served as a matrix blank. Repeatability standard deviations (RSDr) without outliers ranged from 1.5 to 5.7% and reproducibility standard deviations (RSDR) without outliers ranged from 5.0 to 22.7%. cis-Isomers co-eluted with the predominant trans-retinyl palmitate isomer and were included in the results reported by all the collaborative laboratories. Endogenous long-chain esters from milk fat were also measured with the retinyl palmitate additive. The Study Director recommends that this method for determination of retinyl palmitate in fluid milk by LC be adopted First Action.     

Selenium in electrolytic manganese as a reference material for the quality control of aluminium melts

Electrolytic manganese is an important alloying element for aluminium and steel melts. It is mainly added to melts of aluminium in the holding furnace as tablets or minitablets (compressed compacts of manganese and aluminium powders). Selenium derivates are usually added during the production of electrolytic manganese, so some selenium is present in the alloys produced when electrolytic manganese is added to the aluminium furnace. Since the selenium contents of many alloys are of concern from health and environmental perspectives, their values should be provided. In this work, a laboratory reference material (LRM) based on electrolytic manganese was produced to assure our routine quality control method, where selenium is analysed by hydride generation followed by optical emission spectrometry with inductively coupled plasma (HG–ICP–OES). Therefore, the present paper describes in detail the preparation procedure for and the results from homogeneity and stability studies performed on electrolytic manganese LRM. For this purpose, a commercial electrolytic manganese lot was selected and the main factors involved in the preparation of the material (pretreatment step, homogenization, bottling and storage) were carefully studied and established in order to guarantee the long-term stability of the LRM. The results obtained showed that the LRM developed was a fit-for-purpose material for the quality control of the routine analysis of selenium.     

Investigation of chromium(III) acetylacetonate as a calibration reference material for atomic absorption spectroscopy

It is shown that chromium(III) acetylacetonate meets the requirements of calibration reference materials: it is homogeneous, soluble in water and organic solvents, and its solutions are stable. Chromium(III) acetylacetonate has been successfully used as a calibration reference material in the analysis of chromium in iron-base alloys. The procedure involves chromium acetylacetonate extraction using methyl isobutyl ketone followed by direct atomic absorption analysis of the organic extract. The detection limit of the procedure is 10 ng g⁻¹. Correspondence: Konstantin Belikov, State Scientific Institution “Institute for Single Crystals” of the National Academy of Sciences of Ukraine, Kharkov, Ukraine     

Problems in choosing the organs of roe deer (Capreolus capreolus) as reference material

Analytical and Bioanalytical Chemistry - Within a research programme of the specimen bank the standard operation procedures have to be elaborated for roe deer. The liver seems to be one of the...     

Cycloisomerization of 1,6-enynes using acetate as a nucleophile under palladium(II) catalysis

[reaction: see text] An efficient method for the synthesis of five-membered carbo- and heterocyclic compounds, including fused rings, was reported using acetate as a nucleophile in the cyclization of 1,6-enynes under palladium(II) catalysis. The reaction is initiated by trans-acetoxypalladation of the alkynes and quenched by either trans- or cis-deacetoxypalladation in the presence of 2,2'-bipyridine as the ligand. An example of the catalytic asymmetric cyclization is presented with moderate enantioselectivity using chiral bisoxazoline ligand.     

Value assignment of retinol, retinyl palmitate, tocopherol, and carotenoid concentrations in Standard Reference Material 2383 (Baby Food Composite)

In 1997, the National Institute of Standards and Technology (NIST) released Standard Reference Material (SRM) 2383 Baby Food Composite. This SRM can be used as a control material when assigning values to in-house control materials and when validating analytical methods for the measurement of proximates, vitamins, minerals, and trace elements in baby foods and similar matrixes. The Certificate of Analysis for SRM 2383 provides certified and reference values for concentrations of lutein, zeaxanthin, beta-cryptoxanthin, lycopene, alpha-carotene, beta-carotene, delta-tocopherol, gamma-tocopherol, alpha-tocopherol, retinol, and retinyl palmitate for 2 types of sample preparation--extraction and saponification. The assigned values were based on the agreement of measurements made by NIST and collaborating laboratories. The Certificate of Analysis also provides reference and information values for concentrations of proximates, minerals, and additional vitamins; assignment of these values is discussed in a companion paper (this issue, page 276).     

Certified reference material (CRM 414) for the quality control of trace element analysis in plankton

Summary Analyses of plankton are performed by a number of organisations to investigate the transfer and uptake of toxic elements along the trophic chain and to monitor the levels of contamination of different aquatic environments. In order to obtain reliable transfer functions in environmental models or to use plankton as an indicator organism for the assessment of environmental pollution, these analyses should give accurate results. As accuracy requires quality control and the application of certified reference materials (CRMs), a certification campaign has been conducted by the Community Bureau of Reference (BCR). A plankton material was collected in a freshwater pond, lyophilised, homogenised and bottled and its homogeneity and long-term stability were verified. The material (CRM 414) was analysed by a group of 15 selected laboratories having given proof of their adequate QC and using different analytical methods. The contents of As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, Se, V and Zn are certified. This paper presents the certification work performed.     

Problems in choosing the organs of roe deer (Capreolus capreolus) as reference material

Summary Within a research programme of the specimen bank the standard operation procedures have to be elaborated for roe deer. The liver seems to be one of the important organs to be collected for this task. Most of the chlorinated hydrocarbons and elements accumulate preferably in this organ. The distribution of the contaminants is very homogeneous in this tissue. The mean weights of liver from roe deer vary from ca. 280–500 g. At least 100–180 animals have to be collected from certain groups with distinct parameters such as age, sex, living space and time of the year in order to get 50 kg reference material. There seem to exist certain levels of contamination for the different groups. On the completion of further data for proving these levels the livers could be pooled.

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Probleme bei der Organauswahl von Rehen (Capreolus capreolus) als Referenzmaterial

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This paper is granted by the Umweltbundesamt in a research programme     

An interlaboratory test for certification of potassium chloride as a certified reference material (CRM) for solution calorimetry

The enthalpy of solution of KCl in H₂O (12000 mol·mol^–1) at 298.15 K was measured in an interlaboratory test in the G.D.R. The test material was prepared in the ASMW laboratories. The purity found on the high-precision coulometric titration of chloride was 0.9999±0.0001 g·g^–1. The consensus value of the enthalpy of solution in the test was H _s ^298.15 =17.47±0.07 kJ·mol^–1. This result is in good agreement with experimental values from recognized international scientific laboratories. The test material is applicable as a CRM.

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Zusammenfassung Die Lösungsenthalpie von KCl in Wasser (Molverhältnis 12000) bei 298.15 K wurde in einem Vergleichstest in mehreren Laboratorien der DDR gemessen. Das Testmaterial wurde in den Laboratorien des ASMW hergestellt. Eine coulometrische Präzisionstitration des Chlorids ergab seine Reinheit zu (0.9999±0.0001 g/g. Der übereinstimmende Wert für die Lösungsenthalpie wurde in dem Test zu H _s ^298.15 =(17.47±0.07) kJ mol^–1 gefunden, in guter Übereinstimmung mit experimentellen Angabe aus internationalen Laboratorien. Nach Abschluss des Testes ist das Material als bestätigter Bezugsstandard verwendbar.

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2000 / ₂ 298.75 . . ASMW. , - , 0.9999±0.0001 ·^–1. , , H _S298.15=17.47±0.01 ·^–1, , . , CRM.

     

Facile synthesis of indolizines using layered double hydroxides@poly(p-phenylenediamine) as a catalyst with a green tool (neat technology)

The three-component reaction of phenacyl bromide, dimethyl acetylenedicarboxylate and pyridine is catalyzed by layered double hydroxides@poly(p-phenylenediamine) (LDHs@PpPDA), in a one-pot reaction, in order to give the corresponding indolizines in excellent yields.     

Certification of standard reference material (SRM) 1941a, organics in marine sediment

SRM 1941a, Organics in Marine Sediment, has been recently issued with certified concentrations for 23 polycyclic aromatic hydrocarbons, 21 polychlorinated biphenyl congeners, 6 chlorinated pesticides, and sulfur. Noncertified concentrations have been also reported for additional PAHs, PCB congeners, and chlorinated pesticides and for percent total organic carbon (TOC), aliphatic hydrocarbons, and trace elements. SRM 1941a is the most extensively characterized natural matrix SRM issued by the National Institute of Standards and Technology (NIST).