Cheng Huang Lin

Analysis of riboflavin in beer by capillary electrophoresis/blue light emitting diode (LED)-induced fluorescence detection combined with a dynamic pH junction technique

A simple, inexpensive and reliable method for the routine analysis of riboflavin in beer by capillary electrophoresis-light emitting diode (CE-LED) induced fluorescence detection is described. A simple and straightforward sample preparation is involved and the method is based on an inexpensive blue LED as the light source combined with an on-line sample concentration technique. For this detection system, using a normal micellar electrokinetic chromatography (MEKC), stacking-MEKC and dynamic pH junction techniques, the detection limits were found to be 480, 20 and 1ngmL(-1), respectively. In addition, the number of theoretical plates for riboflavin was determined to be 3.8x10(4) by means of a dynamic pH junction and this was improved to 3.2x10(6) when the dynamic pH junction-sweeping mode was applied. The concentrations of riboflavin in 12 samples of different types of commercial beer were found to be in the range of 130-280ngmL(-1).

Determination of riboflavin in urine by capillary electrophoresis–blue light emitting diode-induced fluorescence detection combined with a stacking technique

A simple, inexpensive and reliable method for the simultaneous, routine analysis of riboflavin in urine by capillary electrophoresis-light emitting diode (LED)-induced fluorescence detection is described. Using a blue LED as the light source, the detection limit of riboflavin was determined to be 0.48 microg/ml and was improved to 20 ng/ml when a stacking technique was applied. In the analysis of an actual sample, various concentrations of riboflavin were distributed in the urine samples over a period of 9 h after the ingestion of a vitamin B(2) tablet.

Optimization of the separation of malachite green in water by capillary electrophoresis Raman spectroscopy (CE-RS) based on the stacking and sweeping modes

A capillary electrophoresis Raman spectroscopy (CE-RS) method based on the stacking and sweeping modes are described. A non-fluorescent compound (malachite green, MG; crystal violet, CV) and a doubled Nd:YAG laser (532 nm, 300 mW) were selected as the model compound and light source, respectively. In order to carry out a quantitative and analysis of MG, a monochromator was used to collect the specific Raman line at 1616 cm(-1) (the N-phi and C-C stretching, corresponding to 582 nm when the wavelength of the exciting source is 532 nm). The limit of detection (LOD) for MG was 1.6 x 10(-5) and 1.1 x 10(-5)M, respectively, based on the CZE and MEKC modes. This could be improved to 3.4 x 10(-7) and 5.3 x 10(-9)M, respectively, when the stacking and sweeping modes were applied. The method was also extended to the determination of MG in an actual sample.

Optimization of a simple method for the chiral separation of methamphetamine and related compounds in clandestine tablets and urine samples by β-cyclodextrine modified capillary electrophoresis: a complementary method to GC–MS

The chiral separation of (+/-)-methamphetamine, (+/-)-methcathinone, (+/-)-ephedrine and (+/-)-pseudoephedrine by means of beta-cyclodextrine modified capillary electrophoresis is described. The distribution of enantiomers in clandestine tablets and urine samples were identified. Several electrophoretic parameters such as the concentration of beta-cyclodextrin, temperature, the applied voltage and the amount of organic solvent required for successful separation were optimized. The method, as described herein, represents a good complementary method to GC-MS for use in forensic and clinical analysis.

Paper spray-MS for bioanalysis.

This Review provides a general understanding of paper spray-MS, including the methodology and theory associated with a number of different related applications. This method has become a direct sampling/ionization method for mass spectrometric analysis at ambient conditions and, as a result, it has greatly simplified and increased the speed of mass-spectrum analysis. It has now become an increasingly popular and important method for MS. The first part of this review discusses the fundamentals of paper spray. Some modifications are also reviewed, including nib-assisted paper spray, droplet monitoring, high-throughput paper spray, leaf spray, tissue spray and wooden tip spray. The second part focuses on recent applications, including the analysis of DBS, foodstuffs, drugs and oil. These studies show that paper spray-MS has great potential for use as a fast sampling ionization method, and for the direct analysis of biological and chemical samples at ambient conditions.

On‐line identification of trans‐ and cis‐resveratrol by nonaqueous capillary electrophoresis/ fluorescence spectroscopy at 77 K

This work presents a novel method for the accurate determining trans‐ and cis‐resveratrol (3,5,4′‐trihydroxystilbene) by nonaqueous capillary electrophoresis/fluorescence spectroscopy at 77 K. The proposed method permits not only the separation of resveratrol isomers, but also ensures that on‐line spectra are readily distinguishable and unambiguously assigned. The experimental results also indicate that the effect of nonaqueous capillary electrophoresis buffer and low‐temperature technique increase the detection limit by more than 150‐fold.

Applications of Hadamard transform-gas chromatography/mass spectrometry to the detection of acetone in healthy human and diabetes mellitus patient breath

The Hadamard transform-gas chromatography/mass spectrometry (HT-GC/MS) technique was successfully employed to detect acetone, a biomarker for diabetes mellitus (DM) prediction, in human breath. Samples of exhaled breath were collected from four DM patients (one type-I and three type-II) and eight volunteers (nondiabetic healthy subjects), respectively. The gas samples, without any pretreatment, were simultaneously injected into a GC column through a Hadamard-injector based on Hadamard codes. Under optimized conditions, when cyclic S-matrix orders of 255, 1023 and 2047 were used, the S/N ratios of the acetone signals were substantially improved by 8.0-, 16.0- and 22.6-fold, respectively; these improvements are in good agreement with theoretically calculated values. We found that the breath acetone concentration levels in the four DM patients and the eight volunteers ranged from 1 to 10 ppmv and 0.1 to 1 ppmv, respectively.

Rapid drug-screening of clandestine tablets by MALDI-TOF mass spectrometry

A novel method for the rapid screening of clandestine tablets for drugs by MALDI-TOF mass spectrometry is described. In this method, cetrimonium bromide (CTAB), a surfactant, is added to the conventional alpha-cyano-4-hydroxycinnamic acid (CHCA) matrix solution used in preparing the MALDI samples. This procedure allows very clean mass spectra to be collected for amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxymethamphetamine (MDMA), caffeine, ketamine and tramadol. The method was used successfully in the rapid drug-screening of some actual clandestine tablets, which had been seized from the illicit market, and can serve as a good complementary method to GC/MS for use in forensic analysis.

Rapid analysis of 3,4-methylenedioxymethamphetamine: a comparison of nonaqueous capillary electrophoresis/fluorescence detection with GC/MS

Because of the increasing use of 3,4-methylenedioxymethamphetamine (3,4-MDMA), a rapid and sensitive analytical technique is required for its detection and determination. Using nonaqueous capillary electrophoresis/fluorescence spectroscopy (NACE/FS) detection, it is possible to determine this drug at the level 0.5 ppm without any pre-treatment in less than 5 min. After liquid-liquid extraction, the sample can be condensed and a detection limit of 3,4-MDMA in urine of 50 ppb (S/N = 3) can be achieved. The precision of the method was evaluated by measuring the repeatability and intermediate precision of migration time and the corrected peak height by comparison with a 3,4-MDMA-D5 internal standard. With the conventional GC/MS method, it is necessary to derivatize the 3,4-MDMA before injection and the GC migration time also is in excess of 20 min. Therefore, NACE/FS represents a good complementary method to GC/MS for use in forensic analysis.

A general approach to the screening and confirmation of tryptamines and phenethylamines by mass spectral fragmentation

Certain characteristic fragmentations of tryptamines (indoleethylamine) and phenethylamines are described. Based on the GC-EI/MS, LC-ESI/MS and MALDI/TOFMS, the mass fragmentations of 13 standard compounds, including alpha-methyltryptamine (AMT), N,N-dimethyltryptamine (DMT), 5-methoxy-alpha-methyltryptamine (5-MeO-AMT), N,N-diethyltryptamine (DET), N,N-dipropyltryptamine (DPT), N,N-dibutyltryptamine (DBT), N,N-diisopropyltryptamine (DIPT), 5-methoxy-N,N-dimethyltryptamine (5-MeO-DMT), 5-methoxy-N,N-diisopropyltryptamine (5-MeO-DIPT), methamphetamine (MAMP), 3,4-methylenedioxyamphetamine (3,4-MDA), 3,4-methylenedioxymethamphetamine (3,4-MDMA) and 2-methylamino-1-(3,4-methylenedioxyphenyl)butane (MBDB), were compared. As a result, the parent ions of these analytes were hard to be obtained by GC/MS whereas the protonated molecular ions can be observed clearly by means of ESI/MS and MALDI/TOFMS. Furthermore, two major characteristic fragmentations, namely and alpha-cleavage ([M+H](+)-->[3-vinylindole](+)) and beta-cleavage ([M+H](+)-->[CH(2)N(+)R(N1)R(N2)]), are produced when the ESI and MALDI modes are used, respectively. In the case of ESI/MS, the fragment obtained from alpha-cleavage is the major process. In contrast to this, in the case of MALDI/TOFMS, the major fragment is produced via beta-cleavage. The ionization efficiency and fragments formed from either alpha- or beta-cleavages are closely related to the degree of alkylation of the side chain nitrogen in both cases.