Advion provides analytical instrumentation for characterization, screening, purity determination, and measurement and quantitation of pesticides, toxic metals, and other contaminants. Advion’s custom solutions include the expression Compact Mass Spectrometer (CMS), modular AVANT (U)HPLC systems, and the SOLATION ICP-MS. Streamline your workflow with the industry’s broadest range of innovative sampling techniques, including the Plate Express TLC Plate Reader, Atmospheric Solids Analysis Probe (ASAP), and volatile APCI (vAPCI), without additional sample preparation.
Application: UHPLC/CMS Analysis of Polycyclic Aromatic Hydrocarbons (PAHs) in Water
Figure 1. Advion CMS and AVANT (U)HPLC systems.
The AVANT series has a stackable and modular design, with several options, thereby offering tailored solutions for HPLC as well as UHPLC requirements.
The United States Environmental Protection Agency (EPA) has categorized seven PAHs (benzo[a]pyrene, benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, dibenz[a, h]anthracene, and indeno[1, 2, 3 - cd]pyrene) as Group B2 probable human carcinogens[1, 2].
Figure 2. Chemical structures of the 16 PAHs in the EPA 610 Mix.
The formation of PAHs is increased when meats or other foods are cooked at high temperatures over an open flame. Additionally, the presence of PAHs has been found in several drinking water supplies. When it comes to the environment, EPA’s Great Water Program has listed PAHs as pollutants of concern due to the fact that they persist in the environment, have the potential to bioaccumulate, and are toxic to human beings and the ecosystem. Sixteen PAHs on the EPA priority target list were analyzed by LC/CMS in an EPA 610 Mix.
Figure 3. The mass spectra for three of the PAHs are shown: Naphthalene at m/z 128; Benzo[b]fluoranthene at m/z 252; and Dibenz[a,h]anthracene at m/z 278 are easily detected.
Usually, the nonpolar PAH compounds are not ionized in an electrospray ion source. In conditions of APCI source with heated nitrogen nebulization gas, all 16 PAHs (MW from 128 to 278) were detected as radical cations, M+• via initiation by the corona discharge. Those LC/CMS experiments did not show the presence of the ions of the protonated molecule [M+H]+, which suggests that the protonation process in APCI is not dominant under these conditions.
Figure 4. LC/SIM Analysis of 16 PAHs spiked into tap water.
A factor of 1000 was used to dilute the EPA 610 mix from Sigma Aldrich in tap water. This was then used as a fortified sample for the analysis. Figure 4 shows the LC/SIM chromatograms of the fortified PAH sample with the concentration listed for each compound - from low ppb to high ppt level.
Figure 4. Example of PAH detection limits at pg/μL levels.
A well-separation between the two isobaric PAHs - phenanthrene and anthracene with m/z 178.1, showed that they have different retention times, 2.8 min and 2.94 min, respectively. At 100 ppb, phenanthrene had a signal-to-noise (S/N) of 139, and anthracene an S/N of 185. Therefore, the detection limits of these compounds can be demonstrated to be in the low pg/μL level in the water matrix.
Note: Phenanthrene and anthracene were used in the figure below as they do not respond as well as the other PAHs under those ionization conditions. Consequently, the following conclusion can be drawn - the detection limits of most PAHs in water using the CMS would be in the low ppb regime.
Application: Push-Button TLC/CMS and UHPLC/CMS Analysis of Nutmeg
Figure 5. Advion CMS and Plate Express.
The Plate Express™ TLC Plate Reader provides valuable information at the push of a button, combined with on-line polarity switching and in-source CID capability of the CMS.
We present an example of a TLC/CMS analysis of an alcoholic extract of nutmeg. Four nuts of organic nutmeg spice that were ground to a coarse powder, mixed, and then the 500 mg were added to the 10 mL of methanol for a 15-minute sonication. The slurry was filtered and further centrifuged at 20,000 g for 5 min, and the supernatant was stored in an amber glass vial at 5 °C until used for further analysis.
Derivatization with Fast Blue RR: Fast Blue RR was prepared fresh daily at a concentration of 200 mg/100 mL methanol and mixed with 0.1 N sodium hydroxide solution 2:1 shortly before application by gas sprayer and drying for 20 min at room temperature.
Figure 6. TLC and TLC/CMS analysis of an alcoholic nutmeg extract.
Figure 6 shows the comparison of the nutmeg extract to three cannabis standards (CBN, CBD, and THC). Nutmeg is known to have psychoactive effects and it is one of the few compounds that interfere with multiple color quick tests for cannabinoids. The nutmeg extract shows only a slight response in the Rf 0.4 region of the cannabinoid standards under UV light (B). However, it does not show the signature color reaction when derivatized with Fast Blue RR (A). Derivation suggests that an unknown compound at Rf 0.21 is the interference to the color reaction. MS analysis of the respective location (red oval in B) shows a prominent signal a m/z 402.2 in the negative ion mode scan (C) and an information rich in-source CID MS (D).
A further TLC/FIA/MS analysis of the same analyte shows that it has an isotopic mass of m/z 402.2 in negative ion mode, which makes it impossible for the compound to be a trimyristin. Nevertheless, the CID indicates a triglyceride with at least partial myristic acid content.
Figure 7. UHPLC/CMS analysis of nutmeg extract using both UV and CMS detection. (A) UV trace of nutmeg extract, (B) MS TIC trace in negative ion mode, (C) TIC trace in positive ion mode, (D) negative ion mode MS of the t=0.92 min, and (E) respective positive ion mode MS (in source CID MS data not shown, but identical to Figure 6).
Figure 7 shows a further UHPLC/CMS analysis, which confirms the same analyte with a UHPLC retention time of 9.02 min and MS data that covers both positive and negative ion mode data, as well as in-source CID data in both polarities.
Advion would like to acknowledge Sigma-Aldrich Supelco for the generous gift of the Titan HPLC column used in this study.
Application: Purity Determination and Adulterant Detection of Olive Oils with ASAP
The Atmospheric Solids Analysis Probe (ASAP) offers a one-touch APCI technique for rapid analysis within seconds. ASAP/CMS can be used to screen a variety of samples for purity and adulterants, making it ideal for the food, beverage, and ingredients industry.
A series of vanilla extracts, including an artificial vanilla extract substitute, were tested back-to-back for authenticity and purity determination. Three vanilla extracts were purchased from a local grocery store. Then, they were all diluted 10 times with water (LC/MS-grade). The negative ion mode using the CMS was used to perform the ASAP/CMS experiment.
Figure 8. ASAP/CMS negative ion mass spectra of three different vanilla extracts.
Figure 9 shows the negative ion mass spectrum of each sample. Figure 3A presents Sample 1 clearly contains vanillin (deprotonated vanillin at m/z 151, fragments at m/z 136 and 108, and deprotonated ethyl vanillin m/z 165) – indicators of artificial vanilla flavor.
Figures 1B and 1C show sample 2 and sample 3, these samples respectively contain 4-hydroxybenzaldehyde (m/z 121, deprotonated 4-hydroxybenzaldehyde), vanillin (m/z 151, deprotonated vanillin and fragments at m/z 136 and 108), and vanillin acid (m/z 167, deprotonated vanillin acid). The artificial vanilla flavor (deprotonated ethyl vanillin, m/z 165) is not detected.
vAPCI Analysis of VOCs in the Headspace of Meat to Determine Contamination and Spoilage
Figure 9. vAPCI/CMS setup.
The expression CMS with the volatile APCI (vAPCI) sampling technique allows for fast and direct analysis of volatile organic compounds (VOCs) in the headspace of the sample.
The following article provides a demonstration on how the Advion expression Compact Mass Spectrometer (CMS) coupled to a volatile APCI (vAPCI) ion source can be used to detect directly various crucial chemicals in spoiled meat when spoilage occurs at room temperature. As meat spoiled over the period of a few days, the evolution of putrescine, cadaverine, and indole were measured.
Figure 10. Mass spectra of the daily analysis of the headspace above the meat sample at ambient temperature.
Figure 11 shows the daily analysis of the headspace of a sample of meat at ambient temperature. Putrescene (m/z 89 [M+H]+) and cadaverine (m/z 103 [M+H]+) begin to form and evolve after Day 1, then drop off after Day 4.
After Day 4, no significant amount of amines was detected, so it can be concluded that the formation of amines dropped. During the following several days no putrescine or cadaverine were observed to be generated from the meat. This indicates that the bacteria have consumed the arginine lysine in the sample.
Figure 11. Spectra of the headspace above the meat over four additional days showing indole (m/z 118 [M+H]+) forming on Day 5.
During the later spoilage process, the development of indole began. Figure 12 presents spectra of the head space around the spoiling meat between Days 4 and 7. An increased amount of indole production is evident during Day 5. Indole is formed by bacterial breakdown of the amino acid tryptophan and is another indicator of spoilage by bacterial growth.
- U.S. Environmental Protection Agency. Integrated Risk Information System (IRIS) on Polycyclic Organic Matter. National Center for Environmental Assessment, Office of Research and Development, Washington, DC. 1999.
- U.S. Environmental Protection Agency. Integrated Risk Information System (IRIS) on Benzo(a)pyrene. National Center for Environmental Assessment, Office of Research and Development, Washington, DC. 1999.
- Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological Profile for Polycyclic Aromatic Hydrocarbons (PAHs). Public Health Service, U.S. Department of Health and Human Services, Altanta, GA. 1995.
- U.S. Environmental Protection Agency. Deposition of Air Pollutants to the Great Waters. First Report to Congress. EPA-453/R-93-055. Office of Air Quality Planning and Standards, Research Triangle Park, NC. 1994.
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- Appl Environ Microbiol. 2010 Jul; 76(13): 4260–4268. Found at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2897440/
Link to brochure: https://advion.com/rsc-brochure/food-and-ingredient-analysis/
This information has been sourced, reviewed and adapted from materials provided by Advion.
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