Analytical Methods Blog

Olive oil/nanoparticle degradation by lipase activity

Researchers in Mexico present a new rapid and cost effective spectrophotometric method to determine lipase activity in olive oil.

Lipases are a group of enzymes which catalyse reaction of hydrolysis of triacylglycerols to give free fatty acids, monoacylglycerol and glycerol. Measuring their activity is important in medicine and diagnostics as well as in pharmaceutical, cosmetic and paper industry. Unfortunately, the conventional assays currently available still rely on time-consuming procedures and employ radioactive materials and expensive reagents. In this work, the researchers used a layer of triglyceride coated with  Fe₂O₃  nanoparticles which are released when the substrate is degraded. A consequent change in light absorbance is observed following substrate degradation.
The new spectrophotometric method introduced by Margarita Stoytcheva and her group represents a promising analytical approach to reduce cost and increase effciency.

To read the full article, please access the link below. The paper will be free to read until March 18th.

A spectrophotometric lipase assay based on substrate–nanoparticle assembly degradation
Margarita Stoytcheva ,  Roumen Zlatev ,  Samuel Behar and Jean-Jacques Bois
Anal. Methods, 2013, Advance Article
DOI: 10.1039/C3AY00044C

Trace lead analysis performed using ID-CP-MS

A toxin or heavy metal in a mother’s body can transfer to her baby, and even though lead is primarily stored in bones, trace amounts have the potential to enter breast milk and create a dangerous health risk.

Although multiple testing procedures are available, they have demonstrated a wide range of sensitivities arising from sample contamination and preparation issues. Adrienne Ettinger and researchers at Harvard School of Public Health, USA,  evaluated three digestion procedures for lead analysis using isotope dilution inductively coupled mass spectrometry (ID-ICP-MS).  The primary goal was to see if they could achieve 100% efficiency in any of the digestion processes in the complex media of breast milk, which contains high levels of contaminants such as fat and calcium, and trace levels of lead. Of these, the high pressure asher demonstrated complete sample digestion and had the most consistent lead concentration measurement. By removing analyte contaminants and maximizing the preparation efficiency, they detected trace levels of lead down to 0.2 ng mL^-1.

To read more about this research, please access the link below. This paper will be free to read until March 8th.

Comparison of digestion procedures and methods for quantification of trace lead in breast milk by isotope dilution inductively coupled plasma mass spectrometry
Chitra J. Amarasiriwardena ,  Innocent Jayawardene ,  Nicola Lupoli ,  Ramon M. Barnes ,  Mauricio Hernandez-Avila ,  Howard Hu and Adrienne S. Ettinger
Anal. Methods, 2013, Advance Article
DOI: 10.1039/C3AY26321E

Analysis of gas and liquid phase photoreduction products

Carbon dioxide produced by combustion of fossil fuels can potentially be removed from the atmosphere using an abundant carbon-neutral form of energy: sunlight. Photocatalytic reduction is a promising strategy for CO₂ conversion, but controlling the reaction pathways can be difficult. Identification and isolation of the range of reduction products provides a way of evaluating the efficiency of different photocatalysts.

In this minireview, Rong Xu and researchers at the Nanyang Technological University examine different analytical methods for these conversion products.  They compare a range of GC, HPLC and other chromatographic systems for separation of compounds including alcohols, aldehydes, carboxylic acids and small hydrocarbons. Moreover, they apply their findings to a new set of techniques for accurate detection of CO₂ reduction products with low detection limits, employing a combination of GC and HPLC.

In a useful addition to the study, the authors also investigated the effects of organic additives such as solvents and photosensitisers on these analytical methods.

Photocatalytic reduction of CO₂: a brief review on product analysis and systematic methods
Jindui Hong, Wei Zhang, Jia Ren and Rong Xu
Anal. Methods, 2013,5, 1086-1097
DOI: 10.1039/C2AY26270C

Picture of 5 interconnecting microfluidic components

A new and fast microchip-inspired analytical device based on standard Plexiglas tubes has been developed by researchers in Brazil.
The team, led by Carlos Garcia from the University of Sao Paulo, propose a device based on 5 plastic microfluidic components that serve as both the injector and the reservoir. The plastic components are connected with standard capillary tubes that easily enable the in-channel detection of analytes by a variety of techniques including electrophoresis. To demonstrate the applicability of this design, the researchers performed efficient analysis of inorganic cations by capillary electrophoresis on soil samples.
The microchip-capillary electrophoresis devices commercially available at the moment are still expensive and do not always offer the best analytical performances. This new microfluidic device developed using cheap and simple fabrication materials is an attractive approach for portable and rapid analytical instrumentation.

To read the full article, free to read until March 6th, please access the link below:

Microfab-less microfluidic capillary electrophoresis devices
Thiago P. Segato ,  Samir A. Bhakta ,  Matthew T. Gordon ,  Emanuel Carrilho ,  Peter A. Willis ,  Hong Jiao and Carlos D. Garcia
Anal. Methods, 2013, Advance Article
DOI: 10.1039/C3AY26392D

Antibiotics provide vital treatment in fighting bacterial infection, but over time some have become phased out or even toxic to humans.

Miniaturized device for detection of chloramphenicol in water

One of these is chloramphenicol. Although banned in the European Union, chloramphenicol continues to be used as a cheap remedy in veterinary medicine and can lead to contaminated water and food for our consumption. One technique to test for this contaminant, solid phase extraction (SPE), purifies samples effectively, but requires a pump and a laboratory setting.

Alternatively, Sheng Liu, from the Chinese Academy of Sciences, and colleagues developed a simple yet portable miniaturized SPE (MSPE) device capable of detecting chloramphenicol in water, which has been difficult to test using other methods. A macroporous resin captures and concentrates the chloramphenicol before it passes through an HPLC, all within a 1.5 kg mass instrument. This new technique directly detects low concentrations of chloramphenicol in water, and demonstrates the capacity to function at contaminated locations.

To know more about the study, please click on the link below. This paper will be free to read for the next two weeks.

On-site solid phase extraction and HPLC determination of chloramphenicol in surface water and sewage
Sheng Liu ,  Xian-Zheng Wu ,  Zi-Hui Gao and Fang Jiao
Anal. Methods, 2013, Advance Article
DOI: 10.1039/C2AY26162F