News from LabRulezICPMS Library - Week 50, 2025

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This week we bring you application notes by Agilent Technologies, LECO, and Shimadzu!

1. Agilent Technologies: Measurement of Opaque Liquids with UV-Vis and ATR

Combining the Agilent Cary 60 UV-Vis spectrophotometer with an ATR fiber-optic probe

• Application note
• Full PDF for download

Today, ATR is considered synonymous with FTIR spectroscopy, being the most widely used sampling technique. However, ATR can also be applied to UV-Vis spectroscopy, offering particular benefits for measuring opaque liquids with a fiber-optic probe. 

Samples such as paints, inks, food colorings, sunscreens, and liquid medications are often highly pigmented, rendering them optically opaque. In some cases, measurement of these types of samples using a standard 10 mm path length cuvette may be possible, but only after several hundred‑fold dilution, requiring significant solvent consumption and introducing the possibility of large dilution errors. In the case of emulsion samples such as paints and sunscreens, dilution is often not possible without the sample "splitting" and separating into its component parts. 

ATR spectroscopy is an innovative sampling technique that overcomes these challenges. In ATR, incident light from the spectrometer is directed into a measurement crystal at an angle. Internal reflections within the crystal generate an evanescent wave at the crystal surface, allowing samples in direct contact with the crystal to interact with the standing wave and absorb some of the light energy. 

In a UV-Vis fiber-optic ATR probe, a commonly used crystal is sapphire, with the incident light directed into the crystal to form an angle of 60° at the crystal surface. The crystal is designed to create three bounces at the surfaces (Figure 1). The "effective height" of the wave above the surface is a function of the relative refractive indices of the crystal and the sample medium, the angle of incidence, and the wavelength. The multiple bounces extend the effective path length. For this probe, the effective pathlength at 250 nm is approximately 3 μm and increases to approximately 13 μm at 1,000 nm.

Experimental 

Example data were collected using a Cary 60 UV-Vis spectrophotometer equipped with a fiber-optic interface and Hellma Katana XP 6, 3-bounce ATR probe (Hellma part number PK1KSSZUEASM210N). Spectra were collected by first measuring a baseline using the clean crystal, followed by sample measurement with the crystal immersed in the sample. The Agilent Cary WinUV software was used to collect the spectra as well as to process the measured spectra. All spectra were collected using the measurement conditions shown in Table 1.

Conclusion 

This application note demonstrates how an Agilent Cary 60 UV-Vis spectrophotometer, when combined with a Hellma Katana XP 6 ATR probe, provides a practical and easy-to-use solution for measuring optically opaque liquids that would otherwise require extensive dilution, and for monitoring reactions with absorbance changes too large for conventional methods. The Cary 60 UV-Vis with the ATR probe combination is a powerful tool for a wide range of applications, including routine quality control, R&D studies, and research and teaching laboratories.

2. LECO: Determination of Nitrogen/Protein in Meat and Plant-Based Meat Alternatives

• Application note
• Full PDF for download

Protein is one of the most significant nutrient components in food products. The accurate and precise determination of protein not only plays a role in the characterization of nutritional or dietary value in food materials but is also the key to the economic value of these materials. Protein in meat products is most commonly calculated using the measured nitrogen content in the sample and a multiplier or conversion factor (commonly 6.25). Nitrogen determination is performed using either the classical wet chemical method (Kjeldahl) or a combustion method (Dumas). The Kjeldahl method involves sample digestion, distillation, and ammonia determination typically by titration. This method involves time-consuming sample preparation and the use of hazardous materials. The LECO FP828 is a nitrogen determinator that utilizes an automated combustion (Dumas) method and provides accurate and precise results in approximately three minutes. This eliminates involved sample preparation and the use of hazardous materials resulting in a rapid, cost-effective method for the quality control of the production of meat and plant-based protein products.

Instrument Model and Configuration 

The LECO FP828 is a combustion Nitrogen/Protein determinator that utilizes a pure Oxygen environment in a vertical quartz furnace, ensuring complete combustion and superior analyte recovery. A thermoelectric cooler removes moisture from the combustion gases before they are collected in a ballast. The combustion gases equilibrate and mix in the ballast before a representative aliquot (3 cm³ or 10 cm³ volume) of the gas is extracted and introduced into a flowing stream of inert gas (Helium or Argon) for analysis. The aliquot gas is carried to a thermal conductivity cell (TC) for the detection of Nitrogen (N₂).

Thermal conductivity detectors work by detecting changes in the thermal conductivity of the analyte gas compared to a reference/carrier gas. The greater the difference between the thermal conductivity of the carrier gas and the analyte gas, the greater sensitivity of the detector. 

The FP828 supports either the use of Helium or Argon as the instrument's carrier gas. When used as a carrier gas, Helium provides the highest sensitivity, and the best performance at the lower limit of the Nitrogen range. 

The thermal conductivity difference between Argon and Nitrogen is not as great as the thermal conductivity difference between Helium and Nitrogen, therefore the detector is inherently less sensitive when using Argon as a carrier gas.

TYPICAL RESULTS 

Data was generated utilizing a linear, force through origin calibration using ~0.25 g of LECO 502-896 (Lot 1007) LCRM EDTA (9.59% N). The calibration † was verified using ~0.1 g of LECO 502-642 (Lot 1020) LCRM Phenylalanine (8.46% N). A protein factor of 6.25 was used for all samples to calculate the protein content.

3. Shimadzu: Analysis of Combustion Ash from Biomass Power Generation by EDXRF

• Application note
• Full PDF for download

User Benefits

• EDXRF enables analysis of Na and K, which cause fluidization problems (agglomeration) in circulating fluidized bed boilers in biomass power generation.
• Simple qualitative/quantitative analysis of elements is possible with minimal sample preparation.
• Comparative analysis of heterogeneous samples in the as-received condition and in the homogenized condition after crushing is possible.

In biomass power generation, electricity is generated by using bioresources (biomass) derived from animal and plant sources as a carbon neutral fuel. Biomass power is expected to contribute to reducing total CO2 emissions, and in recent years, the number of woody biomass power plants using wood chips, pellets, and palm kernelshells(PKS) hasincreased.
Circulating fluidized bed (CFB) boilers used in woody biomass power generation generate power by circulating and burning biomass fuel together with silica sand, which is as a fluidized bed medium. However, alkali metal elements (Na, K) contained in the fuel adhere to the surface of the silica sand and combustion ash, causing the particles to stick together and form agglomerates (lumps, coarse particles), which are considered to cause boiler damage and fluidization problems (agglomeration) in the fluidized bed 1) . 

In this article, a Qual-Quant analysis of PKS combustion ash and its coarse particles was conducted using an EDX-8100 energy dispersive X-ray fluorescence spectrometer (EDXRF). Since adhesion of alkali metal elements was detected on the surface of agglomerated lumps, which are considered to cause the problem of agglomeration, analysis of combustion ash by EDXRF can contribute to operational management of combustion furnaces by monitoring the conditionsin the combustion furnace.

Conclusion 

Based on the results of a qualitative analysis of lumps (coarse particles of bottom ash), which are thought to cause agglomeration (defluidization) of the fluidized bed, in the combustion ash of PKS, it was found that alkali metal elements (Na and K) had adhered to the surface of the particles. Since EDXRF enables Qual-Quant analysis of elements with only simple sample preparation, it is considered a useful technique for monitoring the progress of agglomeration and deterioration of the silica sand in the power generation using PKS or woody biomass. Periodic measurements by EDXRF can also be expected to prevent damage and deterioration in combustion furnaces and equipmentstops due to defluidization.