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In the current era of forensic science, where crime scene materials are accessible in trace amounts, forensic spectroscopy has functioned as a non-destructive alternative to traditional destructive procedures in crime evidence examination.

Through forensic spectrophotometry, analysts can intensely study crime scene evidence using the power of electromagnetic imaging. Spectrophotometry is the process of scientifically and objectively measuring color and radio wavelengths. It is more dependable than using human eyes and provides reproducible results on an easy-to-understand scale. With spectrophotometry, forensic examiners can distinguish between the chemical composition, material, and even brand of a piece of evidence by examining how the sample reflects wavelengths.

Spectrophotometry is a preferred method of forensic analysis due to its non-destructive analytical abilities. This process is versatile enough to analyze fibers, hairs, and forensic materials such as bodily fluids, drugs, and fingerprints. Spectrophotometers also have the advantage of not requiring sample preparation before analysis.

What Is Spectrophotometry?

Spectrophotometry refers to the process of analyzing samples using electromagnetic waves. Spectrophotometers test how the light refracts and reflects off a particular material and investigate its color, infrared and ultraviolet properties, and more. Using spectrophotometry, you can tell the difference between similar samples of hairs, fibers, drugs, bodily fluids, and fingerprints.

Spectrophotometry works by taking a sample and measuring the intensity of light when a beam passes through it. Since each compound transmits and absorbs light differently, it is possible to identify the true nature of a substance by analyzing this wavelength. Depending on the nature of the sample, it can be studied using a UV-visible or infrared range spectrophotometer.

How Is Spectrophotometry Used to Solve Crimes?

Spectrophotometry is a gold forensic analysis standard used by the FBI and the American Hazardous Material Response Unit. The spectrophotometric process is essential for telling apart two nearly indistinguishable samples. Most forensic analysts use UV/vis spectroscopy in forensic science to examine inks and fibers, and thin-layer chromatography is a complementary method.

With spectroscopy in forensics, trace evidence analysis, including hairs, fibers, and glass, is highly accurate. Even samples as small as 10-30 mm fiber can undergo examination to determine their chemical composition and whether they're natural or synthetic. Forensic ink examinations are a perfect candidate for spectroscopic analysis. Wavelength examination can identify the unique hues in inks found at the scene and whether they're similar to specific brands of storebought pens. Spectrophotometry is a non-destructive and safer alternative for identifying inks compared to chromatography.

Spectroscopy has various applications in forensic science, including:

Consumers interpret color consistency as a hallmark of your company's quality and goods' desirability. As a result, color measurement is a critical process in manufacturing across many industries, from food production to plastics and textiles. Spectrophotometers outperform manual comparisons by delivering objective and scientific data that eliminates guesswork and supports consistency. Learning how to choose the right spectrophotometer for your needs helps ensure the most accurate data capture and best value for your investment.

1. Use Your Sample Characteristics as Your Primary Guidance

Modern spectrophotometry is entirely substrate-driven, with specialized solutions available to measure color precisely in samples like tomato products and coffees. As a result, the traits of what you're quantifying color and spectral data in are the bedrock for choosing the right spectrophotometer. Factors to consider include:

Sample Opacity

Spectrophotometers use different measurement geometries and construction designs based on a sample's opacity. 

For example, manufacturers generally measure translucent and transparent samples by capturing transmission data. In this design, light passes through the sample to the detectors on the other side, which collect and analyze the data based on the chosen color scale or index.

Conversely, reflectance measurements are ideal for translucent to opaque samples with nonuniform characteristics, like snack foods. These options can feature either directional or diffuse geometries. 

Directional 45°/0° and 0°/45° spectrophotometers replicate the way human eyes perceive color with either bidirectional or circumferential light source configurations. This approach is best for ensuring color consistency in samples where surface finishes may vary and impact color perception. Diffuse 8° spectrophotometers equally illuminate from all directions with a spherical light source design, making them perfect for applications whose goal is true color match. These solutions are also compatible with transmittance measurement for translucent and transparent samples, boosting their application versatility.

Sample Cost and Size Requirements

When evaluating which spectrophotometer will most effectively meet your needs, the minimum and maximum sample sizes it can handle are a key consideration.

In industries like chemical processing and pharmaceutical manufacturing, samples can be extremely expensive. The ideal solution will offer the smallest possible sample size minimum to help contain costs. In contrast, some applications call for larger samples for increased measurement accuracy, so you'll want to choose a device with the flexibility to accommodate bigger substrate sizes.

Samples Requiring Simultaneous Data Capture

Quantifying data for other sample aspects like haze is critical to some products. For example, brewers must measure for color and turbidity to ensure consistent quality. Technologically advanced systems can simultaneously capture both measurements for improved efficiency. Similarly, more sophisticated equipment can also provide color and gloss data in a single operation.

The color of crackers can indicate issues that influence flavor and impact consumer perception of products. Measurement offers a standardized method for determining and comparing color and spectral data to improve quality and minimize waste.

Understanding Color Measurement

Color measurement is an objective process that translates color into numerical data. Quantifying color data enables cracker producers to maintain product consistency and quality. 

Cracker manufacturers have a unique need for objective data because numerous factors influence customer perception, including:

• Irregular shapes
• Ingredients
• Baking processes
• Textured surfaces
• Multicolored flavorings or seasonings

Before someone tastes candy, they see its color and make assumptions about its flavor, freshness, and quality. Color matters in sweets because they come in vibrant hues, and consumers tend to reach for the product that most matches their ideal of a desirable color. Color can also indicate issues in product development or processing steps, making it an effective indicator of quality control. Additionally, measuring color enables consistency across batches. All underscore the importance of knowing how to quantify it accurately.

1. Size and Shape

Size, shape, and texture vary among candies and can create a measurement challenge. Advanced color and spectral data measurement tools account for these variances. Calibration allows for more accurate color measurement across differences while reducing errors. 

2. Color Variations

One piece of candy may contain multiple colors, and some sweets have a different surface color than the interior. A color measurement device must be able to quantify these spectral variations across the color of every layer and swirl.

This chart illustrates how metameric colors appear the same under certain illuminants and drastically different under others. Image Source: Flickr user Johannes Ahlmann

Color matching is a basic but critical component of product manufacturing across industries, and manufacturers go to great lengths to ensure color consistency throughout their production process. Sometimes, this is fairly straightforward, particularly if a product is being manufactured using a single material and pigmentation source. However, when the color of multiple, different product types must be visually identical or a product is being assembled using a variety of materials undergoing unique manufacturing processes, color matching becomes more challenging. One of the primary obstructions to accurate color matching in these situations is illuminant metamerism, which must be identified through the sophisticated analytical capabilities of spectrophotometers.

Biomedical optics offer non-invasive alternatives to many healthcare procedures through the use of spectrophotometric technology. Image Source: Flickr user frankieleon

Biomedical optics very well may be the future of our health care industry. Whether you are an athlete, patient, or parent of an infant, biomedical optics will most likely play a significant role in your health care or that of someone you love in the near future. Biomedical optics utilize NIR (near-infrared) spectroscopy in a number of ways and provides a safe, non-invasive, and non-destructive method of analysis for a variety of medical needs.

Nearly every industry around the world uses measurement in one form or another. From quantity to quality, measurements must be consistent and accurate to promote productivity and profit. However, when dealing with a limited supply of materials, the use of micro measurement is where the real challenges begin. Whether you are trying to eliminate wasted product, are dealing with rare or valuable materials, or simply do not have excess materials on hand, accurate micro measurement is essential when needing to quantify data using only minimal sample amounts.

Spectrophotometry is the most advanced form of measurement for small-to-micro samples. Image Source: Flickr user Surian Soosay