An up-converting phosphor technology-based lateral flow assay for point-of-collection detection of morphine and methamphetamine in saliva

Morphine (Mop) and methamphetamine (Met) are highly addictive drugs worldwide. Point-of-collection testing (POCT) for drug-of-abuse screening is important in abuse/rehabilitation clinics and law-enforcement agencies. We established an up-converting phosphor technology-based lateral flow assay (UPT-LFA) as a point-of-collection testing (POCT) method, namely Mop-UPT-LFA and Met-UPT-LFA, for the detection of morphine and methamphetamine without complicated sample pre-treatment, respectively, in saliva. The sensitivities of the Mop-UPT-LFA and the Met-UPT-LFA were 5 and 10 ng mL-1 with accurate quantitation of 5-100 ng mL-1 and 10-250 ng mL-1 for morphine and methamphetamine, respectively, for a detection time of 15 min. In reference to the detection limits of 20 and 25 ng mL-1 for morphine and methamphetamine, respectively, in the Driving Under the Influence of Drugs, Alcohol and Medicines (DRUID) program of the European Union, the percentage test/control (T/C) ratio of the UPT-LFA between 2 and 15 min reached 101% and 86%, and the UPT-LFA produced accurate qualitative results in 2 min for 100 simulated-saliva samples with the exception of a few weakly positive samples. The sample and sample treating buffer were mixed and added to the test strip, and the test was conducted 15 min later. Although we found no significant difference between the UPT-LFA quantitative test and the liquid chromatography tandem mass spectrometry (LC-MS) test, compared with the latter, the UPT-LFA was substantially faster and had higher detection efficiency. The UPT-LFA showed more accurate qualitative results than the LC-MS for 50 simulated-saliva samples. The ease of operation, high sensitivity, and accuracy of the UPT-LFA make it a valid candidate POCT method for drug-of-abuse screening.

Recent advances in enrichment techniques for trace analysis in capillary electrophoresis

CE is gaining great popularity as a well-established separation technique for many fields such as pharmaceutical research, clinical application, environmental monitoring, and food analysis, owing to its high resolving power, rapidity, and small amount of samples and reagents required. However, the sensitivity in CE analysis is still considered as being inferior to that in HPLC analysis. Diverse enrichment methods and techniques have been increasingly developed for overcoming this issue. In this review, we summarize the recent advances in enrichment techniques containing off-line preconcentration (sample preparation) and on-line concentration (sample stacking) to enhancing sensitivity in CE for trace analysis over the last 5 years. Some relatively new cleanup and preconcentration methods involving the use of dispersive liquid-liquid microextraction, supercritical fluid extraction, matrix solid-phase dispersion, etc., and the continued use and improvement of conventional SPE, have been comprehensively reviewed and proved effective preconcentration alternatives for liquid, semisolid, and solid samples. As for CE on-line stacking, we give an overview of field amplication, sweeping, pH regulation, and transient isotachophoresis, and the coupling of multiple modes. Moreover, some limitations and comparisons related to such methods/techniques are also discussed. Finally, the combined use of various enrichment techniques and some significant attempts are proposed to further promote analytical merits in CE.

Preparation and full characterization of a micro-immunoaffinity monolithic column and its in-line coupling with capillary zone electrophoresis with Ochratoxin A as model solute

A micro-immunoaffinity monolithic column (μIAC) was developed and in-line coupled with capillary zone electrophoresis in a fully automated way with Ochratoxin A as test solute. The in-line micro-immunoaffinity columns based on monolithic methacrylate polymers (EDMA-GMA) were prepared in situ at the inlet end of a PTFE coated fused silica capillary by UV initiated polymerization and subsequently grafted with antibodies. These μIACs were thoroughly characterized. The synthesis of the polymeric support was first demonstrated to be reproducible in terms of permeability, surface properties and efficiency. The antibodies immobilization was then studied by a new original hydrodynamic method (ADECA) allowing the in situ quantitative determination (at a miniaturized scale) of the total amount of immobilized antibodies. The combination of this measurement with the binding capacity of the μIAC allowed, for the first time, the in situ determination of immobilized antibody activity. A total of 260 ± 15 ng (1.6 ± 0.1 pmol) of IgG antibodies/cm in 75 μm i.d. monolithic column (i.e. 18 μgmg(-1)) was obtained with (anti-Ochratoxin A/Ochratoxin A) as antibody/antigen model. 40% of the immobilized antibodies remain active corresponding to a binding capacity of 1.2 ± 0.2 pmol antigen/cm (i.e. 600 pg/cm of our test solute OTA), a very high capacity when dealing with trace analysis and with regard to the detection limits (30 pg and 0.5 pg with UV and LIF detection, respectively). The recovery yields were quantitative with negligible non-specific adsorption and allow analysis of diluted samples (1 ngmL(-1)) for a percolated volume of 10 μL. It was also demonstrated that despite the progressive denaturation of antibodies consecutive to the elution step, the binding capacity of the μIAC remained high enough to implement at least 15 consecutive analyses with the same column and in a fully automated way.

In-line coupling SPE and CE for DNA preconcentration and separation

An in-line SPE method coupled to CE was developed for the analysis of DNA. The amino silica monolith was prepared in situ by polymerization of tetraethoxysilane and N-(β-aminoethyl)-γ-aminopropyltriethoxysilane in ethanol aqueous solution at the inlet end of a 100 μm id fused-silica capillary, and the remaining part of the capillary was used as separation channel. The procedure for this in-line SPE-CE method was constructed on the basis of investigation on operational conditions such as the introduction mode of sieving matrix, the composition of elution solvent and the elution time. Twenty millimolar ammonium hydroxide was demonstrated to be effective for DNA desorption from the monolith, and linear poly(N-isopropylacrylamide) was used as the separation matrix. The proposed method could achieve limits of detection of 0.065-0.123 ng/mL for six DNA fragments ranging 100-2000 bp. Compared with conventional CE, preconcentration factors of over 100 times were obtained. The applicability of the in-line SPE-CE method was further demonstrated by analyzing plasmid DNA from Escherichia coli crude lysate.

Recent advances in enhancing the sensitivity of electrophoresis and electrochromatography in capillaries and microchips (2008-2010)

Capillary electrophoresis has been alive for over two decades now; yet, its sensitivity is still regarded as being inferior to that of more traditional methods of separation such as HPLC. As such, it is unsurprising that overcoming this issue still generates much scientific interest. This review continues to update this series of reviews, first published in Electrophoresis in 2007, with an update published in 2009 and covers material published through to June 2010. It includes developments in the fields of stacking, covering all methods from field-amplified sample stacking and large volume sample stacking, through to ITP, dynamic pH junction and sweeping. Attention is also given to on-line or in-line extraction methods that have been used for electrophoresis.