In response to the growing global need for pesticide residue testing, laboratories must develop versatile analytical methods and workflows to produce scientifically sound results. One of the many challenges faced by food chemists is acquiring suitable pesticide certified reference materials (CRMs) to calibrate analytical equipment, monitor method performance, and confirm the identity and concentration of hundreds of pesticide residues in food samples. CRM producers invest considerable resources to ensure the stability of their products. To present proper CRM handling and storage practices as guidance to ensure stability based on the results of several multiresidue pesticide stability studies. The open ampoule and combined multiresidue mix studies were conducted under controlled conditions. New ampoules containing multiresidue pesticide CRM mixtures were opened and compared to previously opened ampoules at multiple intervals while stored under freezing and refrigerated temperatures. Both LC- and GC-amenable pesticides (>200 residues) were combined and stored under typical laboratory conditions. Studies were performed with and without celery matrix. The open ampoule study showed high levels of stability for all mixtures. All GC residues remained stable over the duration of the experiment. A week after opening LC multiresidue pesticide mixtures showed minor degradation. After combination of the multiresidue pesticide mixtures, degradation occurred rapidly for both the GC and LC mixtures. Multiresidue pesticide mixtures are stable as ampullated until they are opened. Once the contents of a kit were opened and combined, decreasing stability was observed over time. This was true for both the LC and GC kits. Working mixtures of CRMs for instrument calibration should be made daily. This article shows a novel approach for measuring stability of CRM mixes. In-depth analysis of multiresidue pesticide mixtures and the stability that can be expected before and after mixing under typical storage conditions is described.

Understanding processing-structure-property (PSP) linkages of solid-phase microextraction (SPME) coating materials is crucial for the rational design and advancement of these new materials. As SPME is a diffusion-based extraction technique, analyzing the morphology of its coating materials is important for optimizing its performance. In this study, we assess the morphological evolution of micro/mesoporous amorphous silicon (a-Si) thin films sputtered at an oblique angle onto silicon, which serve as models for support materials in SPME devices. The contrast of scanning transmission electron microscopy (STEM) images is enhanced via ZnO infiltration by atomic layer deposition (ALD). Various metrics, including physical descriptors and two-point statistics methods, are employed to follow the films' evolution. Analysis of the two-point correlation function reveals a simple ellipse/spherical local pore geometry in contrast to the long-range irregular arrangement of pores identified by a range of traditional and novel metrics. Additionally, analyzing the internal structure of the pores through homology metrics aligns well with the theoretical understanding of morphological evolution in oblique sputtered films. These analyses show that the “average ratio of principal moment of inertia”, “Betti numbers”, and “two-point statistics” based metrics can capture valuable information during film growth.The morphological analysis approach proposed in this study can be applied to analyze any nanoporous medium as a first step towards developing structure-property relationships that tie back to a given preparation method. Ultimately, a more extensive experimental and/or simulation-based study should confirm the correlations between these metrics and actual diffusion properties as the basis for process-structure-properties relations for improved design and optimization of this film.

Vacuum-assisted headspace high capacity solid-phase microextraction (Vac-HS-HC-SPME) coupled with gas chromatography–mass spectrometry (GC–MS) was used to compare the volatile compounds that make up the volatile and semi-volatile components of five psilocybin mushrooms (Psilocybe cubensis), as well as three non-psilocybin mushroom species. Using an untargeted analysis, common volatiles detected consisted of acids, alcohols, aldehydes, ketones, and hydrocarbons. The initial comparison of Vac-HS-HC-SPME and HS-HC-SPME conditions showed 2 times increase in compound response as well as the detection of 8 additional compounds undetected by HS-HC-SPME. Compounds unique to psilocybin mushrooms were 2-methylbutanal, valeraldehyde, benzaldehyde, 3-octen-2-one, 2-methyl-dodecane, and 2‑butyl‑2-octenal. Compounds unique to non-psilocybin mushrooms were 2-methyl-pyrazine, 2,3-butanediol, butyric acid, butyrolactone, benzyl alcohol, 2-pyrrolidinone, and estragole. The commonly shared compound, 1-octen-3-ol, was shown to have a higher compound response among the psilocybin mushroom species.

Chromatography is an essential analytical tool used in many industries, including pharmaceuticals, foodstuffs, and chemistry. It is the most employed technique for separating, identifying, and quantifying components of a mixture. While there are different types of chromatography, the success of all chromatography systems largely depends on the accuracy and precision of their instruments. For the length of my career, nearly every year ushers in giant steps in the systemic improvement of commercial systems’ accuracy, precision, and overall efficiencies. These “leaps” have frequently been attributable to the physical changes in our systems, such as materials, miniaturization, and chemistries. Today, we turn our attention to software, an essential component of chromatography instruments. This article discusses software’s dynamic and growing role in chromatography, its benefits, and the belief that it will profoundly change our jobs and industry.

The 51st International Symposium on High Performance Liquid Phase Separations and Related Techniques (HPLC 2023), chaired by Michael Lämmerhofer and Oliver Schmitz, was held from June 18 to 22 in Duesseldorf, Germany. This installment of “Column Watch” presents many of the highlighted topics and trends observed at this exceptionally well-run symposium.

In theory, comprehensive two-dimensional liquid chromatography (2D-LC) allows for significant enhanced peak capacity compared to one-dimensional high performance LC (1D-HPLC). However, reaching such a separation performance while also obtaining robust, easily implementable, and sensitive methods proves challenging. Because it can hinder the broader use of 2D-LC, there is a need for developing easier, more trouble-free approaches that feature the benefits of LC×LC while not compromising with what can be done with 1D-HPLC. Commercial 2D-LC interfaces are based on two-position multiport valves composed of two loops, which are alternatingly used either to collect the effluent from the first dimension (1D), or to inject their content to the second dimension (2D). This design implies that if large sampling volumes transferred to the second column need to be avoided, a comparatively (much) higher flow rate and broader column i.d. is required for the second column. However, doing so can lead to a loss in sensitivity because of dilution and impractical analytical chromatography as a result of the high flow rates involved. In most LC×LC column combinations, this problem is exacerbated thanks to the high eluotropic strength of transferred loop volumes. However, when the elution strength of the transferred solvent is very small, refocusing the analytes can be obtained, which allows the user to overcome such issues. For example, this is the case when a purely aqueous separation mode is combined with reversed-phase LC (RPLC) in the 1D and 2D, respectively. Temperature responsive LC (TRLC), which is an emerging LC mode requiring only water as the mobile phase and whereby retention is controlled via temperature only, is promising in this context. In this second installment about TRLC, we illustrate the unique benefits of the combination of this separation mode with RPLC in comprehensive 2D-LC. The potential of the approach is shown through the analysis of representative standard mixtures, active pharmaceutical ingredients, synthetic impurities and phenolics in natural products.