Mixed two- and four-level experimental designs for interchangeable parts with different degrees of assembly difficulty

Purpose

The purpose of this paper is to show how to properly use the method of replacement to construct mixed two- and four-level minimum setup split-plot type designs to accommodate the presence of hard-to-assemble parts.

Design/methodology/approach

Split-plot type designs are economical approaches in industrial experimentation. These types of designs are particularly useful for situations involving interchangeable parts with different degrees of assembly difficulties. Methodologies for designing and analyzing such experiments have advanced lately, especially for two-level designs. Practical needs may require the inclusion of factors with more than two levels. Here, the authors consider an experiment to improve the performance of a Baja car including two- and four-level factors.

Findings

The authors find that the direct use of the existing minimum setup maximum aberration (MSMA) catalogs for two-level split-plot type designs may lead to inappropriate designs (e.g. low resolution). The existing method of replacement for searching exclusive sets of the form (α, β, αβ) available in the literature is suitable for completely randomized designs, but it may not provide efficient plans for designs with restricted randomization.

Originality/value

The authors provide a general framework for the practitioners and have extended the algorithm to find out the number of generators and the number of base factor at each stratum, which guide the selection of mixed two-level and four-level MSMA split-plot type designs.

Recovery of Au(III) ions by Au(III)-imprinted hydrogel

A new Au(III)-imprinted hydrogel (Au(III)-Imp) was prepared by the photopolymerisation of 4- acryloylmorpholine (AcM), 2-hydroxyethyl acrylate (HEA), and poly(ethylene glycol) diacrylate (cross-linking monomer, PEG-DA) in the presence of gold ions. In addition, non-imprinted hydrogel (N-Imp) was similarly prepared without Au(III) ions The Au(III)-Imp hydrogel was characterised by several techniques. To achieve the optimal conditions, effect of pH, time, and initial metal ion concentrations were investigated using a batch system. The pre-concentration factor for Au(III) ions was found to be at least 100. The analytical parameters of the method were determined and the method was also successfully applied to computer circuit board scrap samples. The reusability of the Au(III)-Imp hydrogel was also determined.

Solid phase extraction of Cd, Pb, Ni, Cu, and Zn in environmental samples on multiwalled carbon nanotubes

A simple and sensitive solid phase extraction (SPE) method on multiwalled carbon nanotubes (MWCNTs) is presented for the determination of cadmium, lead, nickel, copper, and zinc at trace levels combined with flame atomic absorption spectrometry. The effects of parameters like pH, sample volume, sample and eluent flow rates, eluent concentration, and volume and type of eluent on the recovery of trace elements was examined. The metals retained on the nanotube at pH 6.5 as α-benzoin oxime complexes were eluted by 10 mL 2 M HNO3 in acetone. The influence of matrix ions on the developed method was also evaluated. The preconcentration factor of the method was found to be 50. The detection limits for Cd(II), Pb(II), Ni(II), Cu(II), and Zn(II) were found as 1.7, 5.5, 6.0, 2.3, and 2.4 μg L(-1), respectively. To test the accuracy of the method, the method was applied to TMDA-70 fortified lake water and Spinach 1570A standard reference materials. Addition recovery studies were applied to tap water and cracked wheat samples, and determination of the analyte elements was carried out in some food samples with good results.

Synthesis, Characterization, Evaluation of Potassium Tertatitanium Whisker Surface Ni(II) Ion-Imprinted Polymers and Selective Adsorption of Nickel

Ni(II) ion-imprinted polymers(Ni(II)-IIPs) was synthesis by the method of surface ion-imprinting in combination with sol-gel process, and prepared by the Ni(II) as template ion, Chitosan(CTS) as functional monomer, γ-Glycidoxypropyl trimethoxysilane (KH560) as linking agent, potassium tertatitanium whisker as carrier. After removing Ni(II) ion from the polymer, Ni(II)-IIPs capable of selectively rebinding Ni(II) ion were obtained. The prepared material was characterized by using the infrared spectra (IR) and scanning electron microscopy (SEM). A batch of adsorption experiments were performed to evaluate its adsorption behavior of Ni(II) using inductively coupled plasma atomic emission spectrometry (ICP-AES). The effect of solution pH, sorbent amount on the extraction of Ni(II) from aqueous solutions were studied. The maximum adsorption capacity of Ni(II) on polymer beads was about 33.1 mg•g−1. The Ni(II)-IIPs have a greater affinity for Ni(II) with respect to Cd(II), Co(II), Cu(II), Hg(II), Mg(II), Mn(II), Zn(II) and Pb(II) ions. Ni(II)-IIPs enabled the selective extraction of Ni(II) from a complex matrix. The prepared functional polymer was shown to be promising for selective pre-separation and enrichment of trace Ni(II) in environmental samples.

Simultaneous Preconcentration of Copper, Nickel, Cobalt and Lead Ions Prior to Their Flame Atomic Absorption Spectrometric Determination

A sensitive and simple method for the simultaneous preconcentration of nutritionally important minerals in real samples has been reported. The method is based on the adsorption of Cu2+, Ni2+, Co2+ and Pb2+ on 4-propyl-2-thiouracil (PUT) loaded on activated carbon. The metals on the complexes are eluted using 5 mL 3 M HNO3 in acetone. The influences of the analytical parameters including pH and sample volume were investigated. The effects of matrix ions on the retentions of the analytes were also examined. The recoveries of analytes were generally higher than 95%. The detection limits for Cu2+, Ni2+, Co2+ and Pb2+ were 1.6, 1.3, 1.2, 2.3 ng ml(-1), respectively. The method has been successfully applied for these metals content evaluation in some real samples including natural water samples.

Inductively Coupled Plasma-Optical Emission Spectrometry for On-Line Determination of Multi Trace Elements in Environmental Samples after Preconcentration by UsingBorassus flabellifer Inflorescence Loaded with 2-Propylpiperidine-1-carbodithioate

A procedure was developed for the determination of Cu, Mn, Pb, Cd, Co, Cr, and Zn in water samples by Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) after preconcentration on synthesized 2-propylpiperidine-1-carbodithioate supported by Borassus flabellifer Inflorescence (BFI). The sorbed element was subsequently eluted with 0.4 M HNO3, and the acid eluates were analyzed by ICP-OES. The influence of various parameters such as pH, flow rate of sample, eluent concentration, volume of the sample, and volume of eluent were investigated. Under the optimal conditions, Cu, Mn, Pb, Cd, Co, Cr, and Zn in aqueous samples were concentrated ca. 100-fold. Recoveries were obtained by the proposed method in the range of 97.8-99.9%. This method was also applied for the analysis of spiked, natural waters and soil samples. The results provide strong evidence to support the hypothesis of an adsorption mechanism.