Zack C.F. Wong

The establishment of a sensitive method in determining different neurotransmitters simultaneously in rat brains by using liquid chromatography-electrospray tandem mass spectrometry

An effective way to determine the amount of different neurotransmitters is vital to the study of brain function. Here, a highly sensitive HPLC-MS/MS method was developed to simultaneously measure γ-aminobutyric acid, dopamine, epinephrine, norepinepherine, glutamate and serotonin in one sample. The quantification of the neurotransmitters was achieved by a tandem mass spectrometer using the selected reaction monitoring scan mode. The method validation included selectivity, linearity, accuracy, precision, stability, recovery and matrix effect. For the six neurotransmitters, the linear regression analysis was calibrated by deuterated internal standards with a R(2) of over 0.991, and the limit of detection (LOD) and the limit of quantification (LOQ) were from 2.5 to 500 pg/mg and 7.5 to 1000 pg/mg, respectively. This method was employed here to reveal different types and amounts of neurotransmitters simultaneously in adult and embryonic rat brains. Here, the change of dopamine concentration in embryonic and adult brain was from 0.071 to 0.760 ng/mg of brain tissue, GABA was from 207.643 to 445.148 ng/mg, glutamate was from 679.535 to 1408.920 ng/mg, serotonin was from 0.058 to 0.485 ng/mg and norepinepherine was from 0.054 to 0.290 ng/mg. For epinephrine, it was only detected in embryonic stage but not in adult, with the concentration at 0.241 ng/mg.

The establishment of a highly sensitive method in detecting ketamine and norketamine simultaneously in human hairs by HPLC-Chip-MS/MS

An effective way to reveal the history of drug abuse is to determine the parental drug and its metabolites in hair. Here, a quantitative HPLC-Chip-MS/MS method was developed for simultaneous measurement of ketamine and its metabolite norketamine in human hair. Ketamine and norketamine were extracted from hair by acid hydrolysis, and then enriched by organic solvent extraction. The chromatographic separation was achieved in 15 min, with the drug identification and quantification by a tandem mass spectrometer. The linear regression analysis was calibrated by deuterated internal standards with a R(2) of over 0.996. The limit of detection (LOD) and the limit of quantification (LOQ) for ketamine and norketamine were 0.5 and 1 pg/mg of hair, respectively. The standard curves were linear from the value of LOQ up to 100 pg/mg of hair. The validation parameters including selectivity, accuracy, precision, stability and matrix effect were also determined. In conclusion, this method was able to reveal the present of ketamine and norketamine with less hair from the drug abusers, and which had the sensitivity of ∼1000-fold higher than the conventional method. In addition, the amount of ketamine and norketamine being detected in different hair segments would be useful in revealing the historical record of ketamine uptake in the drug abusers.

Determination of hair ketamine cut-off value from Hong Kong ketamine users by LC–MS/MS analysis

Ketamine is one of the most frequent abused drugs in Hong Kong and South-East Asia, and the cases of ketamine abused have been reported worldwide. Hair has been commonly used as a specimen for the proof of chronic drug abused because of its non-invasiveness and long detection windows. The determinations of ketamine in hair with varieties of state-of-the-art instruments and detection methods have been developed in the past decade; however, the cut-off value for ketamine abuser has not been developed according to the international guidelines. The aim of this study is to propose a cut-off value for ketamine in hair by analyzing ketamine and its metabolite norketamine by LC-MS/MS method in a population of ketamine users in Hong Kong. The limit of detection (LOD) and limit of quantification (LOQ) for ketamine and norketamine were 20pg/mg and 100pg/mg, respectively. From 977 ketamine abusers, the cut-off value for ketamine in hair was proposed to be 400pg/mg of hair. This proposed cut-off value is the concentration of hair ketamine when over 90% of samples are being detected with the presence of norketamine, which is a proof of ketamine abuse. This value could be applied as a screening or occupational cut-off for reference.

Origin of Red Color in Edible Bird’s Nests Directed by the Binding of Fe Ions to Acidic Mammalian Chitinase-like Protein

The red color of edible birds nests (EBNs) has remained a mystery for hundreds of years. Here, different analytical methods were employed to identify the color origin of EBNs. The treatment of white EBNs with NaNO2/HCl turned them red. In a simulated-gastric-fluid (SGF)-digested EBN, the HPLC chromatogram, NMR spectrum, circular-dichroism spectrum, and Raman spectrum of a NaNO2-treated white EBN closely resembled those of an authentic red EBN. From the HPLC chromatogram of the SGF-digested EBN, the peptides associated with red color were identified in a red EBN and NaNO2-treated white EBN. Several lines of evidence indicated that the color-containing peptide could be derived from the acidic mammalian chitinase-like (AMCase-like) protein of EBNs. Additionally, there was a noticeable increase in Fe-O-bonding intensity after the color change. On the basis of the findings, we proposed that the oxidation of Fe ions in AMCase-like proteins contributed significantly to the color change of EBNs.

Surveillance of drug abuse in Hong Kong by hair analysis using LC-MS/MS

The aim of this study is to reveal the habits of drug abusers in hair samples from drug rehabilitation units in Hong Kong. With the application of liquid chromatography-tandem mass spectrometry (LC-MS/MS) technology, a total of 1771 hair samples were analyzed during the period of hair testing service (January 2012 to March 2016) provided to 14 drug rehabilitation units including non-governmental organizations (NGOs), rehabilitation centers, and medical clinics. Hair samples were analyzed for abused drugs and their metabolites simultaneously, including ketamine, norketamine, cocaine, benzoylecgonine, cocaethylene, norcocaine, codeine, MDMA, MDA, MDEA, amphetamine, methamphetamine, morphine, 6-acetylmorphine, phencyclidine, and methadone. The results showed that ketamine (77.2%), cocaine (21.3%), and methamphetamine (16.5%) were the frequently detected drugs among those drug abusers, which is consistent with the reported data. In addition, the usage of multiple drugs was also observed in the hair samples. About 29% of drug-positive samples were detected with multiple drug use. Our studies prove that our locally developed hair drug-testing method and service can be a valid tool to monitor the use of abused drugs, and which could facilitate rehabilitation program management.