The NIH analytical methods and reference materials program for dietary supplements

Quality of botanical products is a great uncertainty that consumers, clinicians, regulators, and researchers face. Definitions of quality abound, and include specifications for sanitation, adventitious agents (pesticides, metals, weeds), and content of natural chemicals. Because dietary supplements (DS) are often complex mixtures, they pose analytical challenges and method validation may be difficult. In response to product quality concerns and the need for validated and publicly available methods for DS analysis, the US Congress directed the Office of Dietary Supplements (ODS) at the National Institutes of Health (NIH) to accelerate an ongoing methods validation process, and the Dietary Supplements Methods and Reference Materials Program was created. The program was constructed from stakeholder input and incorporates several federal procurement and granting mechanisms in a coordinated and interlocking framework. The framework facilitates validation of analytical methods, analytical standards, and reference materials.     

The caffeine contents of dietary supplements commonly purchased in the US: analysis of 53 products with caffeine-containing ingredients

As part of a study initiating the development of an analytically validated Dietary Supplement Ingredient Database (DSID) in the United States (US), a selection of dietary supplement products were analyzed for their caffeine content. Products sold as tablets, caplets, or capsules and listing at least one caffeine-containing ingredient (including botanicals such as guarana, yerba mate, kola nut, and green tea extract) on the label were selected for analysis based on market share information. Two or three lots of each product were purchased and analyzed using high-pressure liquid chromatography (HPLC). Each analytical run included one or two National Institute of Standards and Technology (NIST) Standard Reference Materials (SRMs) and two products in duplicate. Caffeine intake per serving and per day was calculated using the maximum recommendations on each product label. Laboratory analysis for 53 products showed product means ranging from 1 to 829 mg caffeine/day. For products with a label amount for comparison (n = 28), 89% (n = 25) of the products had analytically based caffeine levels/day of between −16% and +16% of the claimed levels. Lot-to-lot variability (n = 2 or 3) for caffeine in most products (72%) was less than 10%.     

Measuring vitamins and minerals in dietary supplements for nutrition studies in the USA

This article illustrates the importance of having analytical data on the vitamin and mineral contents of dietary supplements in nutrition studies, and describes efforts to develop an analytically validated dietary supplement ingredient database (DSID) by a consortium of federal agencies in the USA. Preliminary studies of multivitamin mineral supplements marketed in the USA that were analyzed as candidates for the DSID are summarized. Challenges are summarized, possible future directions are outlined, and some related programs at the Office of Dietary Supplements, National Institutes of Health are described. The DSID should be helpful to researchers in assessing relationships between intakes of vitamins and minerals and health outcomes.     

Inhibition of the oxygen evolution reaction during titanium passivation in aqueous phosphoric acid solution

Journal of Solid State Electrochemistry - The anodic oxide on titanium can be thickened by anodization, with the consequent corrosion properties of this oxide depending on many variables, including...     

A fourth-order finite difference scheme for two-dimensional nonlinear elliptic partial differential equations

A finite difference scheme for the two-dimensional, second-order, nonlinear elliptic equation is developed. The difference scheme is derived using the local solution of the differential equation. A 13-point stencil on a uniform mesh of size h is used to derive the finite difference scheme, which has a truncation error of order h⁴. Well-known iterative methods can be employed to solve the resulting system of equations. Numerical results are presented to demonstrate the fourth-order convergence of the scheme. © 1995 John Wiley & Sons, Inc.     

A microfabricated electrical SPLITT system

A growing need for methods to analyze and prepare monodisperse nanoparticles on an industrial scale exists and may be solved by the application of split flow thin fractionation (SPLITT) at the microscale. Microfluidic systems of this type have the ability to separate nanoparticles with high precision in a continuous manner. A miniaturized SPLITT system can be fabricated using standard microfabrication technologies, works in a continuous mode, and can be used as a sample preparation instrument in a micro-total-analysis-system (micro-TAS). In this paper, a miniaturized electrical SPLITT system, which separates particles continuously based on electrophoretic mobility, has been characterized. The advantages of miniaturization have been elucidated. The various aspects of the micro SPLITT system discussed in this paper can be broadly classified into: micro SPLITT system design, fluidics modeling to refine the splitter arrangements, and experimental characterization of the SPLITT system. The design of the micro SPLITT system has been elucidated focusing on the two designs that were implemented. Fluid modeling, used to arrive at a new SPLITT design, was done using a commercially available CFD package to investigate behavior of the fluid in the microchannel with various splitter arrangements. Testing was done with nanoparticles of varying diameter and electrophoretic mobilities to verify the modeling results and demonstrate functionality of the SPLITT system. Particles eluted from both outlets of the SPLITT system were characterized using AFM and SEM to verify the function of the system.     

trans‐Bis­[1‐methyl‐3‐(p‐nitro­phenyl)­triazenido 1‐oxide‐κ2N3,O]­di­pyridine­nickel(II)

In the centrosymmetric title complex, [Ni(C₇H₇N₄O₃)₂(C₅H₅N)₂], the coordination geometry about the Ni²⁺ ion is octahedral, with two deprotonated 1‐methyl‐3‐(p‐nitro­phenyl)­triazenide 1‐oxide ions, viz. [O₂N­C₆H₄­NNN(O)­CH₃]^?, acting as bidentate ligands (four‐electron donors). Two neutral pyridine (py) mol­ecules complete the coordination sphere in positions trans to each other. The triazenide 1‐oxide ligand is almost planar, the largest interplanar angle of 8.80 (12)° being between the phenyl ring of the p‐nitro­phenyl group and the plane defined by the N₃O moiety. The Ni—N_triazenide, Ni—O and Ni—N_py distances are 2.0794 (16), 2.0427 (13) and 2.1652 (18) Å, respectively.