Shimadzu US launch for UV-VIS Spectrophotometer
The instrument, launched in November last year, can be used for photometric, spectral, and kinetics measurements to DNA/protein and high-level multi-component quantitation.
It offers wavelength scanning from 190 to 1,100nm and the monitored system for the D2/WI lamps ensures that users can perform stable measurements.
Use in food quality settings
Mark Talbott, molecular spectroscopy product manager at Shimadzu Scientific Instruments, said it can be used for applications in environmental and food quality.
“One application is the analysis of food coloring, for instance sulphur dioxide analysis in white wine (SO2 absorbs in the same region as red wine so the analysis is nut for red wines),” he told FoodQualityNews.
“You could also do quality analysis/quality control (QA/QC) of food products such as sugar water concentrations, syrup concentrations, etc.”
Talbott said mechanically, the 190 to 1100 range allows the use of a silicon diode detector of a photomultipliers (PMT).
“PMT require choppers and high power supplies – more parts to wear out or introduce noise. The silicon diode systems, although less sensitive, are simpler and ultimately more robust for the QA/QC type environments.”
When asked how the method compares to others such as fluorescence, infrared (IR) and Raman spectroscopy, Talbott said it depends on the chemistry.
“UV-Vis analyzes compounds with chromaphores – that is, double bonds or highly colored complexometric titrametric reactions – usually with a complexing agent such as ethylenediaminetetraacetic acid,” he said.
“IR and Raman are looking at compounds that do not so much have chromaphores, but rather specific functionalities such as alcohols, carbonyls, amines, acids, ketones etc.
“Fluorescence is best for samples that, once excited, can pass electrons into a triplet state and propagate fluorescence.
“The advantage of fluorescence is that the detection limit can be significantly reduced over UV-Vis, allowing for detection of very small amounts of a particular analyte.”
Measurement modes
Equipped with seven measurement modes, it can be used for measurements, including photometric, spectral, kinetics, DNA/protein, and high-level multi-component quantitation.
Photometric mode allows users to measure the absorbance or transmittance at single or multiple wavelengths. It is also capable of quantitation using the k-factor method.
Spectrum mode records a sample spectrum using wavelength scanning and users can repeat scans to follow sample changes over time.
Quantitation mode generates a calibration curve from the measurement of standards and then calculates the concentrations of unknowns. Multi-component quantitation mode quantitates up to eight components mixed in a single sample.
Kinetics mode measures absorbance changes as a function of time and gets the enzymatic activity values.
Time scan mode measures the change in absorbance, transmittance or energy as a function of time.
Biomethod mode is used to determine DNA and protein concentrations using several quantitation methods, including the Lowry, BCA, Biuret, CBB and UV absorption methods.
Since the melamine scare a few years back, there has been a heightened concern for better food inspection, said Talbott.
“FERN (The Food Emergency Response Network) is a conglomeration of public and private laboratories that maintain preparedness for testing food quality in large quantities,” he said.
“This testing would overwhelm the current laboratory systems. So the CDC, FBI, and DHS setup laboratory networks to address these types of events.
“These are basically screening labs that need to know if an agent is present in concentration higher that what is deemed safe.
“They need to run lots of samples very quickly. So applications that use simpler analytical tools such as the UV-Vis are highly favoured.”
