Determining a one-tailed upper limit for future sample relative reproducibility standard deviations

A formula was developed to determine a one-tailed 100p% upper limit for future sample percent relative reproducibility standard deviations (RSD(R),%= 100s(R)/y), where S(R) is the sample reproducibility standard deviation, which is the square root of a linear combination of the sample repeatability variance (s(r)2) plus the sample laboratory-to-laboratory variance (s(L)2), i.e., S(R) = s(L)2, and y is the sample mean. The future RSD(R),% is expected to arise from a population of potential RSD(R),% values whose true mean is zeta(R),% = 100sigmaR, where sigmaR and mu are the population reproducibility standard deviation and mean, respectively.     

Determination of vitamin B12 in infant formula and adult nutritionals by surface plasmon resonance: First Action 2011.16 (test kit method)

At the "Standards Development and International Harmonization: AOAC INTERNATIONAL Mid-Year Meeting" on June 29, 2011, an Expert Review Panel (ERP) agreed to further examine AOAC Official Method 2011.01, "Determination of Vitamin B12 by Surface Plasmon Resonance," for use with infant formula and adult nutritionals. The original collaborative study was conducted using the Biacore Q biosensor instrument and the Biacore Q Qflex Kit Vitamin B12 PI. Samples included in the study were infant formula, cereals, premixes, vitamin tablets, dietary supplements, and baby food. Eleven laboratories participated in the collaborative study. The results demonstrated a repeatability RSD (RSDr) of 1.59-27.8 and HorRat values for reproducibility of 0.34-1.89 in samples with levels ranging from ppm to ppb. The assay studied is a label-free protein binding-based assay that uses the principle of surface plasmon resonance to measure the interaction between vitamin B12 and a specific binding protein by passing a portion of the prepared sample extract combined with binding protein solution across a functionalized sensor chip. The response from the functionalized sensor chip is given as free-binding protein, as the mixture binds to the prepared surface of the chip. The ready-to-use Qflex Kit Vitamin B12 PI provides the reagents and accessories necessary to perform this assay. AOAC Method 2011.01 was approved by the AOAC Method Committee on Food Nutrition for Official First Action status, applicable to a wide range of food products, dietary supplements, and multivitamin premixes. After evaluation of the validation data available, an ERP agreed in June 2011 that the method meets standard method performance requirements, as articulated by the Stakeholder Panel on Infant Formula and Adult Nutritionals. The ERP granted the method First Action status, applicable to infant formula and adult/pediatric nutritional formula.     

Uncertainties of method performance statistics based on a balanced completely randomized model interlaboratory study

Using exact and asymptotic distributions, formulas were developed to derive population variances and uncertainties, and their corresponding unbiased estimates, for the method performance statistics, i.e., the sample mean (y..), the repeatability variance and standard deviation and (s2r and sr), and the reproducibility variance and standard deviation (s2R and sR) and obtained from collaborative study of an analytical method.     

On using an approximate noncentral t-distribution in determining a one-side upper limit for future sample relative reproducibility standard deviations

For future sample relative reproducibility standard deviations (RSD(R)), collaboratively obtained under a completely randomized model (CRM), a new formula for determining a one-tailed 100p% upper limit (kappap) for such RSD(R) values was developed based on an approximate noncentral t-distribution with degrees of freedom obtained using Satterthwaite's adjustment. The accuracy of kappap was assessed by comparing kappap and its probability levels with similar values associated with a Monte Carlo simulation and with those obtained using another formula (gammap) that was developed for the same purpose but based on a normal approximation.     

Synthesis of the Bycroft-Gowland structure of micrococcin P1

[formula: see text] We describe the chemical synthesis of the accepted structure of micrococcin P1, a member of the thiostrepton group of antibiotics, and we show that this architecture does not correspond to that of the natural product. Methods developed during the present study should greatly facilitate ongoing efforts centering on the determination of the actual structure of microccin P1, in addition to being applicable to the synthesis of more complex thiostrepton congeners.     

Determination of vitamin B12 in fortified bovine milk-based infant formula powder, fortified soya-based infant formula powder, vitamin premix, and dietary supplements by surface plasmon resonance: collaborative study

A collaborative study was conducted on an inhibition-based protein-binding assay using the Biacore Q biosensor instrument and the Biacore Qflex Kit Vitamin B12 PI. The samples studied included infant formula, cereals, premixes, vitamin tablets, dietary supplements, and baby food. The collaborative study, which involved 11 laboratories, demonstrated that the assay showed an RSDr of 1.59-27.8 and HorRat values for reproducibility of 0.34-1.89 in samples with levels ranging from ppm to ppb. The assay studied is a label-free protein binding-based assay that uses the principle of surface plasmon resonance (SPR) to measure the interaction between vitamin B12 and a specific binding protein. A Biacore Q biosensor uses this principle to detect binding directly at the surface of a sensor chip with a hydrophilic gold-dextran surface. The instrument passes a mixture of prepared sample extract and binding protein solution across a covalently immobilized vitamin B12 chip surface, and the response is given as free-binding protein as the mixture binds to the immobilized surface. This technique uses the specificity and robustness of the protein-ligand interaction to allow minimal sample preparation and a wide range of matrixes to be analyzed rapidly. The reagents and accessories needed to perform this assay are provided as the ready-to-use format "Qflex Kit Vitamin B12 PI." The method is intended for routine use in the quantitative determination of vitamin B12 (as cyanocobalamin) in a wide range of food products, dietary vitamin supplements, and multivitamin premixes.     

Improved chemical synthesis of UDP-galactofuranose

[reaction: see text] A reliable and efficient synthetic route to UDP-alpha-D-galactofuranose (UDP-Galf) has been developed. Reaction of UMP-N-methylimidazolide with Galf 1-phosphate proceeds rapidly to provide UDP-Galf with excellent reproducibility and in a yield approximately twice as high as those reported previously.     

Oxidative dehydrogenation of dihydropyrimidinones and dihydropyrimidines

[reaction: see text] A mild, practical procedure for oxidative dehydrogenation with catalytic amounts of a Cu salt, K2CO3, and tert-butylhydroperoxide (TBHP) as a terminal oxidant has been developed. This oxidation procedure is generally applicable to dihydropyrimidinones and most dihydropyrimidines.     

Design and development of a common synthetic strategy for a variety of 1-N-iminosugars

[formula: see text] A new synthetic strategy has been developed for a general approach toward the synthesis of a variety of 1-N-iminosugar-type glycosidase inhibitors utilizing precursors developed by the PET-mediated cyclization of alpha-trimethylsilylmethylamine radical cation to a tethered pi-functionality.     

Determination of sodium in foods by flame atomic absorption spectrometry after microwave digestion: NMKL interlaboratory study

Nine laboratories participated in an interlaboratory method performance (collaborative) study of a method for the determination of sodium in foods by flame atomic absorption spectrometry after wet digestion, using a microwave oven technique. Before the study, the laboratories were able to practice on samples with defined sodium levels (pretrial test). The method was tested on a total of 6 foods (broccoli, carrot, bread, saithe fillet, pork, and cheese) with sodium concentrations of 1480-8260 mg/kg. The materials were presented to the participants in the study as blind duplicates, and the participants were asked to perform single determinations for each sample. The repeatability relative standard deviations (RSDr) for sodium ranged from 1.9 to 6.5%. The reproducibility relative standard deviations (RSDR) ranged from 4.2 to 6.9%. The HorRat values ranged from 0.9 to 1.6.     

An efficient Pd-catalyzed route to silyl esters

[formula: see text] A one-step, highly selective catalytic route to silyl esters is reported. Commercially available silanes with Si-H functionality were converted to silyl or siloxy esters in the presence of Pd(OAc)2 under mild reaction conditions. This protocol was found to be equally applicable for the modification of multiple silicon centers in one framework and lead to the corresponding polysilyl esters in high yields. A comparison of catalytic efficiency of Pd(OAc)2 versus Pd on carbon was also undertaken.     

Many density functional theory approaches fail to give reliable large hydrocarbon isomer energy differences

[structure: see text] Several DFT methods were found to be unreliable for computing hydrocarbon isomer energy differences. The errors grow with system size up to 20 kcal mol(-1) for the relative energies of the (CH)12 isomers; octahedrane is the most stable (CH)12 hydrocarbon. While DFT geometries generally are good, problems arise for structures with single bonds only, especially for small rings. We recommend the use of higher level, non-DFT energy single points computed at DFT-optimized structures.     

Regioselective synthesis of substituted pyrroles: efficient palladium-catalyzed cyclization of internal alkynes and 2-amino-3-iodoacrylate derivatives

The first efficient and regioselective palladium-catalyzed cyclization of internal alkynes and 2-amino-3-iodoacrylates to give moderate to excellent yields of highly functionalized pyrroles has been developed. This approach is applicable to a range of alkynes and affords the deacylated pyrrole under reaction conditions for most substrates. [reaction: see text]     

Efficient and stereoselective synthesis of allylic ethers and alcohols

[Structure: see text] A short and efficient synthesis of allylic TBS ethers and allylic alcohols has been developed, based upon a unique Kocienski-Julia olefination reaction. Allylic alcohols and allylic ethers are obtained in good to excellent yields and with high (E)-selectivity. The conditions are mild and the procedure is broadly applicable.     

A new route to benzo[4,5]cyclohepta[1,2-b]naphthalenes: synthesis of radermachol

[formula: see text] Condensation of 3-phenylsulfonyl-1,3-isobenzofuranone (3) with benzocyclohept-6,7-en-5-ones such as 4 and 15 provides a straightforward, general method for synthesis of functionalized benzo[4,5]cyclohepta[1,2-b]naphthalenes (e.g., 5 and 16). This finding was used to achieve a brief and efficient preparation of 6,7-benzo-3,4-(1,4-dimethoxy-2,3-naphtho)-1,5-dioxosuberane (2), an established intermediate to the naturally occurring red pigment radermachol (1).     

Headspace gas chromatographic method for determining volatile compounds in infant formulas

Powder infant milk formula quality deterioration and consequently the termination of shelf life results in the appearance of off-flavors mainly determined by a composite effect of spoilage volatiles. A headspace gas chromatographic method to determine propanal, pentanal and hexanal as the main volatiles present in the headspace of powder infant formula oxidation is described as a rapid indication of oxidative status. Under optimum conditions the limits of detection for propanal, pentanal and hexanal were 17.19, 16.87 and 19.60 ng and the limits of quantification were 37.37, 31.96 and 35.97, respectively. The calibration graphs of the method were linear from 25 to 1500, 20 to 3500 and 30 to 8500 ng for propanal, pentanal and hexanal, respectively, with determination coefficients exceeding 0.99. The precision results showed that the relative standard deviations of the repeatability and reproducibility were between 2.2 and 5.5%. The analytical method was simple, rapid, and reliable and permitted the analysis of a large number of formulas using small sample volumes.     

Samarium diiodide-induced asymmetric synthesis of optically pure unsymmetrical vicinal diamines by reductive cross-coupling of nitrones with N-tert-butanesulfinyl imines

[reaction: see text] An efficient method for the preparation of optically pure unsymmetrical vicinal diamines by the SmI(2)-induced reductive cross-coupling of nitrones with chiral N-tert-butanesulfinyl imines was developed. This is the first successful example of the highly diastereoselective and enantioselective cross-coupling between two different imine species. It provides a straightforward access to enantiopure unsymmetrical vicinal diamines that are widely applicable in asymmetric synthesis.     

Synthesis of enamides related to the salicylate antitumor macrolides using copper-mediated vinylic substitution

[formula: see text] A new approach to the assembly of enamides is described using copper(I) carboxylate-catalyzed substitution of vinyl iodides and amides. Modified reaction conditions have been developed to synthesize the O-methyloxime enamide side chains related to the natural products lobatamides A-F, oximidine I and II, and CJ-12,950.     

Lower rim functionalized resorcinarenes: useful modules for supramolecular chemistry

[formula: see text] A synthetic scheme for the selective functionalization of all-cis (rccc) resorcinarene platform at the "lower rim" was developed. Self-folding and self-complementary cavitands were prepared for molecular recognition and self-assembly, bearing functionality at remote sites. These molecules promise applications on solid support and as polymeric capsules.