Conventional electrical-field-assisted
sample preparation (EFASP)
methods rely on analyte transfer between immiscible phases and require
at least one aqueous phase in contact with the electrode. In this
paper, we report a novel nonaqueous miscible liquid–liquid
electroextraction (NMLEE) technique that enables fast exhaustive enrichment
of ultratrace analytes from a milliliter-level donor in a vial to
a microliter-level acceptor in a tube. Miscible nonaqueous solvents
are used for the donor and acceptor to overcome common EFASP problems
such as high charge or mass transfer resistance, loss of analytes
in the membrane phase, water electrolysis, back-extraction, bubble
generation, and difficulties in the application of high voltage for
fast migration. According to theoretical derivation and experimental
verification results, the concentrations of analytes in the donor
and their migration velocity in the acceptor both decrease exponentially
with time, and the extraction recovery correlates linearly with the
current variation. These mechanisms result in efficient enrichment
by forming an analyte-enriched zone and allow the extraction progress
and recovery to be monitored and estimated based on the current variation.
NMLEE was coupled with liquid chromatography–mass spectrometry
to analyze 10 amphetamine-type drugs, atropine, nortriptyline, and
methadone in blood and urine samples. This method provided low limits
of detection (0.003–0.1 ng·mL–1), satisfactory
extraction recoveries (89.6–104.1%), and RSDs (<12.3% for
intraday and <8.8% for interday), which met the requirements of
the ICH guidelines. This study may contribute to the further development
of EFASP methods for effective ultratrace analyses in forensic science.
In recent years, cosmetic industry profits soared due to the widespread use of cosmetics, which resulted in illicit manufacturers and products of poor quality. Therefore, the rapid and accurate detection of the composition of cosmetics has become crucial. At present, numerous methods, such as gas chromatography and liquid chromatography-mass spectrometry, were available for the analysis of cosmetic ingredients. However, these methods present several limitations, such as failure to perform comprehensive and rapid analysis of the samples. Compared with other techniques, matrix-assisted laser desorption ionization time-of-flight mass spectrometry offered the advantages of wide detection range, fast speed and high accuracy. In this article, we briefly summarized how to select a suitable matrix and adjust the appropriate laser energy. We also discussed the rapid identification of undesired ingredients, focusing on antibiotics and hormones in cosmetics.
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