Pretreatment methods in ion chromatography: A review

As an advanced analytical technology, Ion Chromatography (IC) has been widely used in various fields. At present, it is faced with the challenges of sample complexity and instrument precision. It is necessary to select appropriate pretreatment methods to achieve sample preparation and protect the instruments. Therefore, this paper reviews several commonly used sample pretreatment technologies in IC, focusing on sample digestion and purification techniques. Additionally, we introduce some advanced IC technologies and automatic sample processing devices. We provide a comprehensive summary of the basic principles, primary applications and the advantages and disadvantages of each method. Pretreatment methods should be carefully selected and optimized on the specific characteristics of the sample and the ions to be measured, in order to achieve better analysis results.

Development of microwave assisted-UV digestion using diluted reagents for the determination of total nitrogen in cereals by ion chromatography

The objective of this work is to develop a microwave assisted-ultraviolet (MW-UV) digestion in the presence of dilute HCl and H₂O₂ followed by ion chromatography (IC) measurements for the determination of total nitrogen in cereals. This approach (MW-UV-IC) requires lesser time and does not need environmentally hazardous materials as used in Kjeldhal method. Further, the developed method requires only microliter quantities of dilute HCl and few milliliters of H₂O₂ for the matrix digestion and simultaneous conversion of nitrogen to its ionic species for the subsequent analysis by IC. At the optimized acid concentrations (200 ​μL of 0.1 ​mol ​L^-1 HCl) and microwave power, the nitrogen in the cereals flours is converted to nitrate (NO₃ ^-), nitrite (NO₂ ^-) and ammonium (NH₄ ⁺) ions. The nitrogen species were separated using IonPac AS-20 and IonPac CS-17 columns and then quantified using suppressed conductivity detection. The method was applied to estimate the total nitrogen in flours of various cereals like; wheat (Triticum aestivum), rice (Oryza sativa), finger millet (Eleusine coracana), jowar (Sorghum) and pearl millet (Pennisetum glaucum). The results obtained using proposed method, were in good agreement with that of Kjeldhal method. Further, the precision of the values obtained by developed method was on par with the Kjeldhal method for all the tested flours as verified by F-test (n ​= ​5 and 95% confidence limit). Additionally, greenness assessment tools like analytical Eco-scale and green analytical procedure index (GAPI) suggested the proposed MW-UV-IC method, for the determination of total nitrogen in cereal flours, to be excellently green and safe.

Traceable quantitation of cyanocobalamin (vitamin B12) via measurement of cobalt and phosphorus: a comparative assessment using inductively coupled plasma atomic emission spectrometry (ICP-AES) and ion chromatography (IC)

Traceable quantitation of cyanocobalaminviameasurement of cobalt and phosphorous by ICP-AES and IC after MW-UV digestion. Measurement of (Cobalt_total− Cobalt_free) by IC provides an accurate quantitation of the analyte.

Time-resolved ICP-MS analysis of mineral element contents and distribution patterns in single cells

Novel single cell techniques are attracting growing interest for clinical applications, because they can elucidate the cellular diversity and heterogeneity instead of the average masked by bulk measurements. Herein, time-resolved ICP-MS for the determination of essential mineral elements in single cells has been developed and is used to analyze the contents and distribution patterns of Fe, Cu, Zn, Mn, P and S in two types of cancer cells (HeLa and A549) and one type of normal cells (16HBE). The results show that there are obvious differences in contents and distribution patterns of the elements among the three types of cells. The mass of Fe, Zn, Cu, Mn, P, and S in individual HeLa cells is significantly higher and span a broader range of values than in the single 16HBE and A549 cells. The contents of Fe, Zn, and Cu follow log-normal distributions, and Mn, P, and S follow Poisson distributions with high λ values in single HeLa cells, indicating a large cell-to-cell variance. Comparatively, the contents of Cu, Zn, P, and S in 16HBE cells show the narrowest distribution range among the three tested cells, demonstrating the homogenous distribution of the elements in the cells. The method of single cell ICP-MS (SC-ICP-MS) provides potential applications for the monitoring of the variation of mineral elements at a single cell level.

Accurate quantitation standards of glutathione via traceable sulfur measurement by inductively coupled plasma optical emission spectrometry and ion chromatography

The quantitative analysis of glutathione (GSH) is important in different fields like medicine, biology, and biotechnology. Accurate quantitative measurements of this analyte have been hampered by the lack of well characterized reference standards. The proposed procedure is intended to provide an accurate and definitive method for the quantitation of GSH for reference measurements. Measurement of the stoichiometrically existing sulfur content in purified GSH offers an approach for its quantitation and calibration through an appropriate characterized reference material (CRM) for sulfur would provide a methodology for the certification of GSH quantity, that is traceable to SI (International system of units). The inductively coupled plasma optical emission spectrometry (ICP-OES) approach negates the need for any sample digestion. The sulfur content of the purified GSH is quantitatively converted into sulfate ions by microwave-assisted UV digestion in the presence of hydrogen peroxide prior to ion chromatography (IC) measurements. The measurement of sulfur by ICP-OES and IC (as sulfate) using the "high performance" methodology could be useful for characterizing primary calibration standards and certified reference materials with low uncertainties. The relative expanded uncertainties (% U) expressed at 95% confidence interval for ICP-OES analyses varied from 0.1% to 0.3%, while in the case of IC, they were between 0.2% and 1.2%. The described methods are more suitable for characterizing primary calibration standards and certifying reference materials of GSH, than for routine measurements.