Electrophoretic analysis of polyamines in exhaled breath condensate based on gold-nanoparticles microextraction coupled with field-amplified sample stacking

Colorimetric-photothermal-magnetic three-in-one lateral flow immunoassay for two formats of biogenic amines sensitive and reliable quantification

Rapid, simple, sensitive and reliable approaches for biogenic amines quantification in various food samples are essential to food safety. Lateral flow immunoassay (LFIA) has been wildly utilized in point-of-care testing (POCT) owing to its advantage of flexibility and feasibility. Here, we reported a Fe₃O₄@Au nanoparticles (NPs) (Fe₃O₄@AuNPs) based multimodal readout LFIA for rapid putrescine (Put) and histamine (His) quantification with a LOD down to 10 and 10 ng/mL in naked eye mode, 2.31 and 4.39 ng/mL in photothermal mode, 0.17 and 0.31 ng/mL in magnetic mode, respectively. Such multi-mode assay has been successfully used to detect Biogenic amines (BAs) in raw aquatic foods, including fish, prawns, beef, and pork, with overall recoveries ranging from 93.68 to 109.34%. Meanwhile, it is easily expanded to detect other typical BAs with high sensitivity by simply replacing antibodies. In view of the multi-signal reading, two quantitative formats, and high sensitivity, it may greatly widen the application of lateral flow detection in food safety.

In-line sample concentration in capillary electrophoresis by cyclodextrin to admicelle microextraction

Cyclodextrins (CDs) as a pseudophase in pseudophase-to-pseudophase microextraction (P2ME) in capillary zone electrophoresis (CZE) are proposed. In this P2ME mode called CD to admicelle ME, a long plug of dilute analyte solution prepared in cetyltrimethylammonium bromide (CTAB) at the critical micellar concentration was injected into the capillary. This formed CTAB admicelles at the interface between the solution and the negatively charged capillary surface, where the analytes were trapped. The injection of CD solution released the admicelles and the analytes from the capillary surface due to the formation of stable CD/CTAB inclusion complexes. The analytes are concentrated at the CD front during injection and voltage separation. Various neutral CDs were found to be effective for CD to admicelle ME. To implement this in-line sample concentration technique in CZE, CD concentration, sample injection time, and sample:CD solution injection ratio were optimized. The optimized conditions for five model anionic analytes, namely, 4-bromophenol, sulindac, sulfamethizole, 4-vinylbenzoic acid, and succinylsulfathiazole, were 20 mM α-CD in 20 mM sodium tetraborate (pH 9.2) solution, sample injection time of 370 s, and CD:sample injection ratio of 1:2. The sensitivity enhancement factors (SEFs) were between 112 and 168. The SEFs of sulindac and sulfamethizole in particular were similar to previously published off-line microextraction techniques, which are typically time-consuming. The calculated values of LOQ, intra-/inter-day (n = 6/n = 10, 3 days) repeatability, and linearity (R2) of CD to admicelle ME were 0.0125-0.05 µg/mL, 1.5-4.6%, 1.8-4.8%, and ≥0.999, respectively. Finally, the potential of CD to admicelle ME to the analysis of artificial urine samples was demonstrated.

Tween 20-capped gold nanoparticles for selective extraction of free low-molecular-weight thiols in saliva followed by capillary electrophoresis with contactless conductivity detection

Low-molecular-weight thiols are widely present in human fluids, and are regarded as a kind of potential broad-spectrum evaluation indicators for some clinical diseases. In this work, gold nanoparticles capped with Tween 20 were used for purification and microextraction of the main free thiols (cysteine, homocysteine, glutathione and methionine) in saliva based on Au-S bond formation. Ultrasound further sped up the releasing of the target analytes, and the releasing time needed was only 10 min, and the required sample volume was only 40 µL. The desorption solution could be directly injected for electrophoretic analysis without derivatization, and field-amplified sample stacking of electrophoretic online enrichment technology further improved the detection sensitivity. The synergistic enrichment effect made the enrichment factors of four analytes reach 1119-2067 times. This developed method was applied for the analyses of saliva samples of healthy volunteers. Acceptable sensitivity (LODs: 0.15-1.5 ng mL^-1) and recoveries (97.6-116%) were obtained in the saliva sample matrix. This proposed method provides an alternative for the sensitive detection of low-molecular-weight thiols in noninvasive body fluids, which has potential application prospect in the preliminary noninvasive diagnosis of diabetes, cardiovascular diseases, etc.

Capacitively coupled contactless conductivity detection for analytical techniques - Developments from 2018 to 2020

The developments of analytical contactless conductivity measurements based on capacitive coupling over the two years from mid-2018 to mid-2020 are covered. This mostly concerns applications of the technique in zone electrophoresis employing conventional capillaries and to a lesser extent lab-on-chip devices. However, its use for the detection in several other flow-based analytical methods has also been reported. Detection of bubbles and measurements of flow rates in two-phase flows are also recurring themes. A few new applications in stagnant aqueous samples, e.g. endpoint detection in titrations and measurement on paper-based devices, have been reported. Some variations of the design of the measuring cells and their read-out electronics have also been described.

Determination of urinary prostaglandin E2 as a potential biomarker of ureteral stent associated inflammation

Ureteral stents are the most widely used surgical implant in urology. However, they may cause adverse effects to patients, including pain, discomfort, and inflammation. In this work, the inflammatory effect of stent placement and the associated elevation of cyclooxygenase-2 (COX-2) expression were observed. Furthermore, a capillary electrophoresis mass spectrometry (CE-MS) based approach was subsequently developed to quantify urinary prostaglandin E₂ (PGE₂), a COX-2 metabolite known to contribute to inflammatory renal diseases, to further interrogate the role of this pathway. Urine samples were cleaned and preconcentrated by solid-phase extraction (SPE), and an on-line sample stacking method was used for the enrichment of analytes. The accuracy, precision, and specificity of this method were validated. Standard addition methods were performed to assess the reliability of using deuterated internal standards (IS) in compensating the remaining matrix effect after SPE as well as the detector fluctuation. Through the analysis of 32 pig urine samples, a statistically significant increase of PGE₂ was observed in the stented group compared to the unstented (P = 0.01) and the recovered (P = 0.004) groups. This work determined that stent placement may contribute to COX-2-dependent inflammation and developed a reliable CE-MS based methodology to quantify PGE₂ in stented individuals that may further understand the biology of stent-associated inflammation and inform urologic patient management.

Double surfactants-assisted electromembrane extraction of cyromazine and melamine in surface water, soil and cucumber samples followed by capillary electrophoresis with contactless conductivity detection

BACKGROUND

Cyromazine (CYR) and its main degradation product melamine (MEL) are attracting wide attention due to their potential hazards to the environment and humans. In this work, double surfactants-assisted electromembrane extraction (DS-EME) by Tween 20 and alkylated phosphate was firstly used for purification and extraction of CYR and MEL, and the extract was directly analyzed by capillary electrophoresis with capacitively coupled contactless conductivity detection.

RESULTS

Under the optimum conditions, two targets could be well separated from the main interferences, including common biogenic amines and inorganic cations within 14 min. This developed method was successfully applied to the analyses of surface water, soil and cucumber samples, and the average recoveries were in the range 93.3-112%. DS-EME provided a synergistic purification and enrichment effect for CYR and MEL by adding Tween 20 and alkylated phosphate into donor phase and supporting liquid membrane, respectively. Satisfactory limits of detection [0.2-1.5 ng mL^-1 , signal-to-noise ratio (S/N) = 3] could be obtained in the tested sample matrices, and the corresponding enrichment factors were up to 115∼123 times.

CONCLUSION

This developed method provides an alternative for the simultaneous analysis of CYR and MEL in complex real-world samples. © 2019 Society of Chemical Industry.