Milestone Inc.

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Learn how to select the most appropriate microwave digestion technology for determining trace and heavy metals via ICP-OES and ICP-MS.

Selecting Microwave Digestion Technology for Trace Metals v3

Single reaction chamber (SRC) microwave digestion offers multiple benefits over traditional dry ashing for the sample preparation of heavy crude oils for trace metals analysis. These include increased sample throughput, reduced risk of contamination, more complete digestion and retention of volatile analytes. 

The digestion of heavy crude oil samples prior to trace metal analysis by ICP-OES has traditionally been performed by dry ashing in a muffle furnace. The oil is burned off over a burner prior to ashing in a muffle furnace. The process takes several hours and requires continual operator attention. Loss of sample and cross contamination can occur due to foaming and splashing. Volatile analytes are lost and can not be measured. While closed vessel microwave digestion offers several advantages over dry ashing, a max. sample weight of ~0.2 g is considered too small for representative analysis. Single reaction chamber (SRC) microwave digestion however, can digest higher sample weights, enabling microwave digestion to be applied to the sample preparation of heavy oils.  

Milestone's new UltraWAVE SRC benchtop digestion system can digest up to five heavy oil samples at a time, at up to 300 °C and 199 bar pressure. Its high temperature and pressure capability enables the complete digestion of heavy oils, which makes sample introduction to the ICP-OES easier and more routine. The UltraWAVE can digest 0.75 g of heavy oil (up to five samples simultaneously) — more than 3x higher sample weight than closed vessel digestion. Samples are simply digested in disposable glass vials: unlike dry ashing, there are no crucibles to clean. The system is fully automated: the sample is weighed into a vial, 10 mL HNO

 added and loaded into the UltraWAVE. Its walk away operation means labor costs are significantly reduced over dry ashing. The reaction chamber is pre-pressurized with N

, which eliminates cross contamination of loss of volatiles.  

Figure 1: UltraWAVE digestion program with 5 x 0.75 g heavy oil: ramp to 250 Â°C over 30 min and hold for 10 min. The line T1 shows the actual digestion temperature achieved. The applied microwave power is automatically controlled by the system so the actual digestion temperature precisely follows the programmed temperature profile. The outer temperature of the reaction chamber also monitored (T2). Note that pressure (P) reached almost 100 bar during the run. This is due to the high weight and high organic content of the samples, which generates NOx and CO2. Pressure was released automatically at 55 min.			

The Milestone UltraWAVE is able to digest heavy oils in amounts sufficient for the application with increased sample throughput and reduced labor costs compared to dry ashing. Risk of contamination and loss of volatile elements is eliminated and the superior digestion quality allows for easier analysis by ICP-OES.  

Figure 2: Sample rack being loaded and samples after digestion.			

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Sample Preparation of Heavy Crude Oil

Selecting Microwave Digestion Technology for Trace Metals v2

Selecting Microwave Digestion Technology for Trace Metals

Single Reaction Chamber (SRC) technology to simplify and optimize food and mixed-food microwave sample preparation for trace metal analysis using ICP-MS is described. 

Digesting Food Samples for Trace Element Analysis

This app note describes the Hg analysis of fish and animal tissue without any sample preparation and using a single, matrix-independent calibration.

Direct Mercury Analysis in Fish

Realize up to 90% cost savings by purifying low-cost reagent grade acids to produce the high-purity acids needed for the lowest ICP-MS detection limits.

Sub-Boiling Acid Purification

https://www.spectroscopyonline.com/spec_w/innovations

To comply with government regulations concerning nutrition and safety, food producers commonly use atomic spectroscopy techniques such as inductively coupled plasma–optical emission spectroscopy (ICP-OES) and ICP-mass spectrometry (ICP-MS). Over the last few years, new test methods have emerged in food QA/QC laboratories to better understand food authenticity, nano-particle presence, and distinguishing different elemental species. In this webcast we will review current analytical methods as well as necessary microwave sample preparation techniques to enhance efficiency and accuracy for the modern food lab.

Discover new methods around atomic spectroscopy for food authenticity, nano particle analysis, and elemental species analysis

Understand which atomic spectroscopy technique is best suited for food nutrition and food safety analysis

Review the full process for analyzing various food samples, from initial sample preparation to ICP-MS or ICP-OES analysis

See how both rotor-based and single reaction chamber (SRC) digestion technologies can accommodate the needs of food testing laboratories

Eric Farrell, Product Specialist, Milestone Inc.

Ross Ashdown, Marketing Manager for AAS, MP‐AES, and ICP‐OES, Agilent Technologies

Tuesday, October 13, 2020 at 2pm EDT | 1pm CDT | 11am PDT

On demand available after airing until Oct. 13, 2021

Webcasts

In this webcast we will review current analytical methods as well as necessary microwave sample preparation techniques to enhance efficiency and accuracy for the modern food lab.

Innovations in Trace Metals Analysis for the Modern Food Testing Lab

Achieve high performance and high throughput within a single rotor-based platform.

High Quality Sample Preparation for Trace Metals Analysis

Milestone's UltraWAVE microwave digestion system with its groundbreaking single reaction chamber (SRC) technology enables the simultaneous digestion of up of to 22 different food sample types with different chemistries at temperatures and pressures as high as 300 °C and 200 bar, greatly increasing efficiency and simplifying product development.

	Elemental impurities are monitored in foods to ensure safe levels and compliance with regulation. One particular class of these elemental impurities, the "Big 4" (arsenic, mercury, lead and cadmium), are of special concern because ingestion of quantity relatively low in food product can cause serious health issues, including - but not limited to - reproductive troubles, developmental disorder, brain damage, kidney and liver damage, and cancer. Given the serious health risks, a more stringent regulation is calling for the use of closed vessels digestion for sample preparation and inductively coupled plasma (ICP) for elemental impurities analysis as a replacement of obsolete and subjective methods of analysis based on colorimetric tests.

	In this application note, two frosting samples are digested simultaneously on a 15-position rack with a single temperature profile. In addition, setting the instrument is straightforward: a ramp time to target temperature and a hold time at target temperature.

	Frosting or icing products are delicate matrices to digest because they are made of significant amounts of carbohydrate and lipids, and thus are very exothermic during degradation. Digestion of the two varieties of frosting using a traditional microwave system would require two different runs and could possibly require two different rotors. Because of the exothermic nature of the sample, on a traditional microwave there is a limitation of the size of the sample that could be digested, since a relatively large sample size (>0.500 g) will generate a level of pressure that will cause the system to vent with loss of volatile elements.

	Samples were placed in a 15-position rack and lowered into the single reaction chamber. The chamber was pre-pressurized with nitrogen at 40 bar to raise the acids boiling point and thus prevent any cross-contamination and loss of volatiles due to boiling and spitting as the temperature increases inside the chamber.

	The two samples were fully digested as evidenced by the clear solutions obtained. The digestion lasted for less than 1 h including cooling time. The higher performance and greater ease of use make the UltraWAVE a good fit for a food company where samples of different types are common. Additionally, by using five position vials, samples as large as 2 g can be digested. Such capability not only addresses the common sample homogeneity concern of the food industry, but also gives the possibility to dilute samples with as much flexibility for ICP-OES as for ICP-MS.


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