Using Handheld LIBS Analyzer for Material Verification of Ionically Bonded Salt Compounds

Introduction

Handheld analyzers based on near-infrared (NIR) or Raman spectroscopy are often used by the food and pharmaceutical industries for chemical corroboration of raw materials.

However, NIR and Raman technologies are not capable of visualizing ionically bonded compounds and materials, including common salts like KCl, NaCl, acetates, chlorides, and so on. Therefore, until recently, no effective handheld analyzer technology has been developed to validate these materials.

The Z-300, a handheld analyzer from SciAps, is based on laser-induced breakdown spectroscopy (LIBS) technology (Figure 1). This handheld technology provides a quick and highly precise method for verifying ionic salts.

Z-300 handheld analyzer

Figure 1. Z-300 handheld analyzer

The instrument fires a sequence of laser pulses onto a sample and produces a plasma. When the plasma cools down, atomic emissions from the target material are captured in a wide range spectrometer, thereby providing the material’s elemental composition.

The time taken for this analysis is just 2 to 3 seconds. This method is similar to spark optical emission spectroscopy (OES), but instead of an electric spark, a pulsed laser is used to create the plasma.

Because of this difference, LIBS is not limited to conducting samples like spark OES, but can examine all materials.

Analyzer details

Elements from all periodic table groups, ranging from H to U, can be measured by the Z-300 handheld analyzer. The device includes the following components:

  • A user-replaceable, on-board argon purge (for 10 times more enhancement in precision as opposed to air-based analysis)
  • A wide range spectrometer (190 – 950nm)
  • A rastered laser for acquiring averaged results over a standard sample area

The Z-300 is based on an Android operating system that provides broad connectivity to other instruments as well as an easily scalable platform. The device can measure elements like C, H, Li, Cl, Na, Mg, K, Ca, etc. and enables rapid verification of ionically bound materials.

Unlike NIR and Raman, the analyzer is extremely sensitive to ionically bonded compounds as well as to low atomic number elements like C, H, O, Na, Li, Mg, K, Ca, and S.

For this type of application, the LIBS technology is better than the handheld X-ray fluorescence (XRF) technology. HHXRF is not sensitive to Na and lower atomic number elements, and just weakly sensitive to major cations like Al, Mg, K, and Ca.

Test results

The Z-300 spectra from store-purchased potassium chloride (KCl) and sodium chloride (NaCl) materials are shown in Figure 2. A spectral region for an NaCl sample is depicted in Figure 3.

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Figure 2. Z-300 spectra from sodium chloride and potassium chloride materials

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Figure 3. A region of the spectra for an NaCl sample

Both K and Na are extremely strong emitters, as shown in Figure 2. The key lines are marked as Na1, Na2, and so on.

Generally, the K line (K1) at approximately 405nm is not employed for material verification, because if the material contains iron, it will experience significant interference that would be difficult to correct. As an alternative, the line at K2 or K3 is employed. K2 is helpful for studying primarily potassium-based materials.

In Figure 2, the shape of K3 is unusual because it is saturating, due to the high concentration of potassium in the sample analyzed. This indicates high sensitivity of the K3 line, making it more useful when measuring trace levels or reduced concentrations of K.

The different sodium emission lines are used in a similar way. When measuring high concentrations, the Na2 line is employed because of saturation of the Na1 line in a relatively pure NaCl material.

Contamination was also found in these commercially available materials. There is K quantified in the NaCl sample and Na quantified in the KCl sample.

The extended spectral region between 830 and 900nm is shown in Figure 3, illustrating the significance of the wide range spectrometer. Shown here are five exceptional chlorine (Cl) lines that were concurrently determined with elements like Ca, Na, K, etc. The lines from the argon purge gas are also shown.

A confident verification of NaCl first requires measurement of both Cl and Na. A NaOH compound or sample contamination may deceive a method that solely depends on Na. Secondly, when multiple lines (five in the case of Cl) are measured, it provides a higher statistical confidence in the verification as opposed to measuring a single line – so a spectrometer spanning into the 900nm range is very important, particularly for Cl.

Finally, sulfur should be determined for most material verifications. The Z-300 handheld analyzer is the only HH LIBS instrument that reaches 950nm, allowing it to determine the S emissions in the 920nm region.

It must be noted which elements have not been measured. The Z-300 device is moderately sensitive to N and O (emissions in the 700’s nm range); extremely sensitive to hydrogen (H); and also to emission at 656.5nm.

Air containing water vapor is removed from the analysis area by the argon purge, so these emissions either do not emerge or yield extremely small signals in the KCl and NaCl spectra.

This is critical, for instance because the O and H measurements provide an important means of differentiating NaCl from NaOH. Equally important are the wide range, high resolution spectrometer and the argon purge, as they offer the required elemental sensitivity and range for ultimate detection of ionically bonded salt compounds.

Download the PDF brochure for more information about the SciAps Z-300 analyzer

Conclusion

SciAps’ Z-300 high-performance handheld analyzer can potentially meet the critical material verification requirements of the food and pharmaceutical sectors.

In particular, it can provide verification of ionically bound salt compounds that are not sensitive to NIR, Raman, and other conventional molecular methods.

The Z-300 device integrates a wide range spectrometer, a proprietary laser, and an on-board argon purge into an advanced handheld LIBS analyzer. Unique to the SciAps LIBS products, these features can measure any class of elements in the periodic table.

Integrated with the new sample detection system, the device can be used under Class 1 conditions, therefore removing the regulatory stipulations of class 3b LIBS and X-ray devices.

About SciAps, Inc.

SciAps, Inc., is a Boston-based instrumentation company specializing in portable analytical instruments. Our mission is to provide durable, field-tested, portable instruments to identify any compound, any mineral, any element — anyplace on the planet. Manufacturing, service and customer support is operated out of our fully ISO-certified facility located in Laramie, WY.

Last updated: Aug 2, 2016 at 11:18 AM