Written by Mandi Hellested, Chief Technology Officer

Imagine a poolside scene: sparkling water, laughter, and the distinctive scent of chlorine in the air. It’s not just a refreshing dip; it’s also a rendezvous of science. Chlorine, a powerful chemical, has a peculiar relationship with human hair. As it mingles with the sebum – a natural oil coating your hair – a chemical dance begins, altering the very essence of your locks. This interaction goes unnoticed, but it holds secrets that forensic analysts know well.

Chlorine’s Dance with Hair

Chlorine, in its hypochlorous acid form (HClO-), is a chameleon in water, bonding readily with other elements and compounds. It becomes irresistibly drawn to its oily companion when it encounters human hair laden with sebum. Sebum, our body’s natural moisturizer, is rich in antioxidants, especially vitamin E, which bestows vitality upon our hair and skin.

But when chlorine steps onto the stage, it’s a different story. It bonds with sebum through chemical wizardry, snatching away its nourishing properties. Gradually, your hair loses its shine, strength, and moisture, turning dry and brittle. The consequences can be dire – split ends and deteriorating hair health.

The Elemental Secrets

Beyond chlorine, your hair harbors a trove of elemental clues. It contains water and traces of minerals like calcium, chromium, zinc, and iron. While present in minute quantities, these elements whisper stories of your environment and diet.

Chromium, for instance, is a normal nutritional element found in hair. Sulfur, another essential element, plays a crucial role in curly hair’s structure as it’s woven into the keratin strands. And then there’s barium, whose presence might point to water or air pollution exposure.

Figure 1: MicroXRF mapping of human hair evidence, revealing detailed elemental distributions for sulfur, chlorine, calcium, chromium, iron, nickel, zinc, arsenic, and barium.  Maps were collected using a 5 μm spot and pixel size.

Follicles and Curls

Your hair’s story doesn’t stop with chemicals; it also reveals secrets about your biology. The shape of your hair follicle determines its curl – oval follicles result in curly hair, while round ones lead to straight strands. Understanding the intricate connection between biology and appearance is a powerful tool in forensics. If a hair is too short to see curls, we interrogate the follicle shape to answer the question of straight or curly.

Arsenic’s Dark Secret

Lastly, the tale of arsenic – a deadly element with an affinity for keratin, a protein found in hair. Arsenic doesn’t just pass through; it gets trapped, binding itself to the hair. This is a critical discovery for forensic purposes. Hair analysis for arsenic serves not only as evidence of exposure but also as a timeline. It can reveal when an exposure occurred, a piece of information invaluable in many criminal investigations.

Figure 2: The maps above are from the same sample used in Figure 1, except they are set to a fire color scale to help visualize the intensity difference to match the intensity legend.

Intriguingly, arsenic’s presence in hair can persist for a considerable time, making it a helpful tool for forensic analysts. While urine tests can’t detect past exposure, hair analysis offers a window into events spanning the past 6 to 12 months.

Though XRF is not the preferred technique for Hair Segmental Analysis, it does offer an interesting visual.


Your hair is not just a part of your appearance but a silent witness to your life’s journey. Every strand tells a story, from the chemicals it encounters to the minerals it carries and the curls it forms. For forensic scientists, decoding these tales is a pathway to uncovering the truth, even when the answers may be hidden in the most unexpected places.

For those keen to explore the intricacies of microXRF in forensic analysis or aiming to delve deeper into the science behind it, we are here to guide you.

Reach out to us for more details on forensic analysis using microXRF. Uncover the hidden stories in every sample.

Learn More About Forensic Analysis by MXRF

IXRF Systems is a leading provider of X-ray fluorescence instrumentation. With our advanced analytical solutions, we are committed to supporting research, quality control, and educational endeavors across various industries. 

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