From Colour Catcher® to colorimetric sensors: disposable and cheap devices for inorganic ions determination

We describe disposable and cheap colorimetric devices obtained by fixing classical dyes on the commercial paper sheet known as "Colour Catcher®" (here named under the acronym CC), the product used to prevent color runs in washing machines cycles. These devices can be used as colorimetric sensors for different analytes of environmental and biological interest since the indicator dye, fixed on the solid material, changes its spectral properties (color and hence UV-vis spectrum) upon contact with the analyte. The relationship between the analyte content and the UV-vis spectrum (or RGB values) change of each sensor is provided using a chemometric tool: the Partial Least Squares regression (PLS). Promising results were obtained when applying these sensors to actual samples, so because of their simple preparation with low-cost reagents, they can be effective for application in environmental and food analysis.

Material intrinsic heterogeneity: statistical derivation

The value of a fully statistical sampling theory is that it is possible to quantify a measure of material intrinsic heterogeneity and, on this basis, provide the entire distribution of the analyte content of potential samples to be extracted from the lot. The analyte content of a sample of a given mass is a random quantity as samples of nominally equal masses taken from a lot in a given state of comminution will not have exactly the sample analyte content. The analyte content of a sample is correctly described as a random variable and to characterise a random variable completely it is necessary to know either the probability density function or distribution function for the random variable, or all of the moments of the random variable (mean, variance and all the higher moments). The following discussion derives the fundamental sampling variance from a purely mathematical statistics basis, relying on the assumption that the number of particles of any one type (size and analyte content) that fall into a sample taken in a mechanically correct manner (following the principle of equiprobable sampling) follows a Poisson distribution. In addition, the Poisson distributions of particle numbers are statistically independent. A more fully argued substantiation of this fundamental assumption, partial experimental evidence and standard statistical introduction to the definition and properties of the Poisson distribution, and reasons for its use, can be found at the end of this article. © Materials Sampling & Consulting 2020

Quantification of retinyl palmitate, thiamine, niacin, pyridoxine, folic acid, cyanocobalamin, zinc, and iron by chromatographic methods in fortified kernels and fortified rice

This study presents the optimization and validation of methods for the analysis of retinol, thiamine, niacin, pyridoxine, folic acid, cyanocobalamin, zinc, and iron in fortified kernels (coated and extruded) and in fortified rice. The analyses were performed by HPLC-UV/FLD/MS and ICP-OES. The optimized methods showed good resolution of the analyte peaks, excellent recovery (87–108%), reproducibility with relative standard deviation (SD) of analyte content between 1.8 and 11% and high correlation coefficient of the calibration curves (R2 > 0.997). Limit of detection was from 2.8 E-4 mg/kg for pyridoxine to 1.26 mg/kg for zinc and limit of quantification was from 9.2 E-4 mg/kg for pyridoxine to 4.21 mg/kg for zinc. Thereby the optimized methods demonstrated reliability and sensitivity in the detection and quantification of these micronutrients and that they are suitable for routine analysis of fortified kernels (coated and extruded) and fortified rice.

Primary and secondary amine material based on crosslinked polystyrene: synthesis and initial application for multiresidue pesticides analysis

Weak anion exchange sorbent based on cross-linked polystyrene with primary secondary amine group was prepared by substitution nucleophilic reaction (SN2) between methylene chloride group and 1,2-ethylene diamine. The effect of factors, namely the weight ratio of amine over methylene chloride, reaction time and temperature on nitrogen percentage were studied using experimental design approach. The amination yield rose as all of factors increased but was reduced while both temperature and time increased simultaneously. Nitrogen percentage of the products were varied from 4.0% to 6.3%. Sorbents with predicted capacity of 4.5%, 5.0%, 6.3%, and 6.5% were synthesized. The results showed that the actual capacities of the products were close to the predictions, especially for those in the experimental domain, indicating a good model that can be used to prepare sorbents of any desired capacity. The sorbent application ability of multiresidue pesticides analysis in food were initially investigated through both aspects: interference elimination and analyte content conservation.

Magnetic Graphene Oxide as an Efficient Adsorbent for the Separation and Preconcentration of Cu(II), Pb(II), and Cd(II) from Environmental Samples

The separation and preconcentration of copper(II), lead(II), and cadmium(II) ions on magnetic graphene oxide (MGO) by solid-phase extraction was carried out. Quantitative recovery was obtained by adsorption of analytes on MGO at pH 6 and elution of 3 M HNO3 in 10% acetone. To optimize the presented method, the effects of various parameters—including pH, eluent conditions, and vortex time—were examined. Matrix effects were also investigated. Mean recoveries of the analytes were between 95and 105%. The proposed method was validated by applying it to certified reference materials. Addition and recovery tests were also performed. The method wasapplied to verify the analyte content of several water and food samples.

Determination and Evaluation of Dead Time for X-Ray Fluorescence Spectrometer

When an X-ray photon which is generated by the sample enters into the detector, pulses can be produced and recorded. The detector is unable to respond to another photon that enters at the same time when a photon is being detected. The time that the detector takes to respond to a photon is regarded as dead time. For the x-ray fluorescence detector, the recorded count is less than the real count impulse due to dead time. Hence, to correct x-ray intensity of samples whose element content is vastly different, determination of dead time is necessary. In this paper, a new and complete way to determine dead time is proposed, which can be summarized as “intensity pair method”. Three “intensity pairs” were used for determining dead time, which were “intensity pair” of collimators (S2 and S4), “intensity pair” of spectral lines (Kα and Kβ) and “intensity pair” of beads with different flux-sample ratio (higher SH and lower SL analyte content in the beads). It comes to a conclusion that dead time obtained from “intensity pair” of beads is the most practical method for correcting X-ray fluorescence intensity. As for routine analysis, the dead time of proportional counter can be accurate to 1×10-9s, which can make intensity correction error less than 0.1%.

Inorganic analysis of herbal drugs, Part I: Metal determination in herbal drugs originating from medicinal plants of the family Lamiacae

Elemental profiles of the total analyte content of major, minor and trace elements (Cu, Zn, Mn, Fe, K, Ca, Mg, Al, Ba and B) in 8 herbal drugs, originating from medicinal plants of the family Lamiacae, were determined. Flame atomic absorption/ emission spectroscopy (FAAS/FAES), inductively coupled plasma atomic emission spectroscopy (ICP-AES) and energy dispersive X-ray fluorescence (EDXRF) were applied, and the advantages and limitations of these techniques are also discussed. The whole procedure, from sample preparation via dissolution to the actual measurements, was validated by using CRM (NIST 1573a - Tomato leaves). The recovery values obtained were in the range 90.64 - 101.58 %. A high degree of similarity in their elemental profiles was noticed from the results of qualitative analysis, while quantitative analysis shows significant diversity due to the variety of the influencing sources. The medicinal plants investigated in this work contained Cu (5.92- 14.79 mg kg-1), Zn (15.0 - 43.0 mg kg-1), Mn (25 - 111 mg kg-1), Fe (74 - 546 mg kg-1), K (1.80 - 6.24 %), Ca (0.90 - 1.43 %), Mg (0.17 - 0.67 %), Al (49 - 378 mg kg-1), Ba (15.53 - 69.84 mg kg-1) and B (34.7 - 56.5 mg kg-1).

Identification of Allantoin, Uric Acid, and Indoxyl Sulfate as Biochemical Indicators of Filth in Food Packaging by LC

A liquid chromatographic (LC) method was developed for the determination of allantoin, uric acid, and indoxyl sulfate in mammalian urine contaminated packaging material including paper bagging, corrugated cardboard, grayboard, and burlap bagging. The procedure involves solvent extraction and isolation of the 3 analytes by reversed-phase LC with ultraviolet detection at 225 nm for allantoin and 286 nm for uric acid and indoxyl sulfate. The composition of authentic mammalian urine such as mouse, rat, cat, dog, and human were also determined with regard to the 3 compounds of interest. A linear concentration range of 0.11–20.4, 0.02–10.0, and 0.04–30.0 μg/mL was obtained for allantoin, uric acid, and indoxyl sulfate, respectively. Limits of detection (LOD) and quantitation (LOQ) were 0.0104 and 0.0345 μg/mL for allantoin; 0.0018 and 0.0060 μg/mL for uric acid; and 0.0049 and 0.0165 μg/mL for indoxyl sulfate, respectively. Interday relative standard deviation values for a mixture of standard allantoin, uric acid, and indoxyl sulfate (n = 5) were 0.97, 0.80, and 0.94%, respectively. Analyte composition for 5 types of authentic mammalian urine varied from 0.19–6.88 mg/mL allantoin; 0.08–0.57 mg/mL uric acid; and 0.03–0.78 mg/mL indoxyl sulfate. Analyte content for 8 samples including 2 samples each for paper, cardboard, grayboard, and burlap bagging each contaminated with mouse or rat urine ranged from <LOD to 4598 μg/gm allantoin; <LOD to 202 μg/gm uric acid; and 17.5 to 616 μg/gm indoxyl sulfate. Recoveries of allantoin, uric acid, and indoxyl sulfate from 11 fortified samples (4 types) for both mouse and rat urine ranged from 28.2 to 114.1% for allantoin; 32.6 to 123.4% for uric acid; and 52.6 to 118.2% for indoxyl sulfate.