Purge Trap Research Articles

Portable purge and trap-microplasma optical emission spectrometric device for field detection of iodine in water

Iodine is essential for human growth and can enter the body through food, water, and air. Analyzing its presence in the environment is crucial for ensuring healthy human development. However, current large-scale instruments have limitations in the field analysis of iodine. Herein, a miniaturized purge and trap point discharge microplasma optical emission spectrometric (P&T-μPD-OES) device was developed for the field analysis of iodine in water. Volatile iodine molecules were produced from total inorganic iodine (TII) through a basic redox reaction under acidic conditions, then the purge and trap module effectively separated and preconcentrated iodine molecules. The iodine molecules were subsequently atomized and excited by the integrated point discharge microplasma and an iodine atomic emission line at 206.24 nm was monitored by the spectrometer. Under optimal conditions, this proposed method had a detection limit of 16.2 μg L−1 for iodine and a precision better than 4.8%. Besides, the accuracy of the portable device was validated by successful analysis of surface and groundwater samples and a comparison of the mass spectrometry method. This proposed portable, low-power device is expected to support rapid access to iodine levels and distribution in water.

Advances in microbial analysis: Based on volatile organic compounds of microorganisms in food

In recent years, microbial volatile organic compounds (mVOCs) produced by microbial metabolism have attracted more and more attention because they can be used to detect food early contamination and flaws. So far, many analytical methods have been reported for the determination of mVOCs in food, but few integrated review articles discussing these methods are published. Consequently, mVOCs as indicators of food microbiological contamination and their generation mechanism including carbohydrate, amino acid, and fatty acid metabolism are introduced. Meanwhile, a detailed summary of the mVOCs sampling methods such as headspace, purge trap, solid phase microextraction, and needle trap is presented, and a systematic and critical review of the analytical methods (ion mobility spectrometry, electronic nose, biosensor, and so on) of mVOCs and their application in the detection of food microbial contamination is highlighted. Finally, the future concepts that can help improve the detection of food mVOCs are prospected.

Rapid detection of trace formaldehyde in food based on surface-enhanced Raman scattering coupled with assembled purge trap

It has been remained a challenge to detect trace formaldehyde in complex samples, such as rice flour and duck blood products. In this study, a purge-trap device was designed and used for volatile target detection, which avoided interference adsorptions on enhanced particle surfaces during subsequent surface-enhanced Raman spectroscopy (SERS) analysis. The device produced a low detection limit for formaldehyde of 1 × 10−4 μg/mL in the concentration ranges of 4 × 10−3–4 μg/mL and 1 × 10−4–3 × 10−3 μg/mL. In the process of the detection of duck blood and rice flour, partial least squares regression (PLSR) was adopted for sample analysis. The formaldehyde concentration was calculated and compared to the actual value from the above model with R2 of 0.97, which indicated high accuracy and stability. These results suggested that the proposed method was reliable and suitable for rapid analysis of trace formaldehyde in real products.

Determination of butyltins in environmental samples using sodium tetraethylborate derivatisation: characterisation and minimisation of interferences

Interferences affecting the determination of butyltin species by sodium tetraethylborate (STEB) derivatisation followed by purge–trap preconcentration were systematically studied using synthetic solutions, natural water samples and sediment extracts. Substances that did not cause interferences included most common cations (apart from those metal ions listed below), anions, metalloids and polar organic compounds. Natural organic matter (NOM) specifically interfered with tributyltin (TBT) due to a mechanism involving partitioning of the butyltin to the hydrophobic portions of the NOM. The metal ions Ag(I) (≥2 μM), Cd(II) (≥2 μM), Cu(II) (≥0.5 μM) interfered predominantly with the determination of monobutyltin (MBT) due to catalytic degradation of the STEB reagent. Pb(II) (≥14 μM) interfered with butyltin determination by an unknown mechanism. Other interferences to the purge–trap method were shown to occur in the presence of chelating agents (e.g. EDTA) or hydrophobic liquids such as diesel fuel. A mixture comprising methanol (MeOH), EDTA and Mn(II) was used to partially mask the effect of interfering NOM and metals. Spike recoveries (mean±S.D. of n=7 different samples) of MBT, dibutyltin (DBT) and TBT in contaminated natural water samples were improved from 70±36,90±11 and 91±24 to 102±10,98±3 and 98±4%, respectively. Spike recoveries (mean±S.D. of n=5 different samples) of MBT, DBT and TBT in aliquots of sediment extracts were improved from 86±17,79±18 and 59±32 to 97±6.2,103±3.6 and 103±5.0%, respectively. The ability to analyse larger aliquots of sediment extracts in the presence of the masking mixture improved the detection limit four-fold if MBT and DBT determination was required and 10-fold if only TBT determination was required.

Volatile components of Grana Parmigiano-Reggiano type hard cheese

GC–MS analysis of volatile components of Grana Parmigiano-Reggiano type Italian hard cheese was performed by solid phase micro extraction (SPME) and Purge & Trap (PT) methods. Half of the 24 samples analysed were produced in flat land (<90 m over sea level), the other half in mountain (90–600 m) regions, by small to medium cheese factories. The composition of the volatile components reveals more dependence on the individual factories than on the geographic location. Ripening increases the difference among samples.

Determination of chlorine dioxide using 4-aminoantipyrine and phenol by flow injection analysis

The determination of chlorine dioxide (ClO 2) using 4-aminoantipyrine (4-AA) and phenol by flow injection analysis, was investigated in the presence of various chlorinated species that can occur under normal water-treatment conditions. The colorimetric method with 4-AA and phenol relies on the use of a Tris-HCl buffer. Adjusting the reagent to pH 9.0 with the Tris-HCl buffer gives high sensitivity and is effective in eliminating hypochlorite interference. Furthermore, using purge trap system for pretreatment makes it possible for this method to eliminate interferences from metal ions, as well as other oxychlorinated compounds, such as chlorite and chlorate.

Optimal Conditions of Purge Trap/On-Column Cryofocusing Method with Capillary Gas Chromatography for Determination of Volatile Halogenated Hydrocarbons in Aqueous Samples.

The dynamic purge trap and simple on-column cryofocusing method with capillary gas chromatography was used to study the basic optimal conditions for determination of the trace levels of volatile halogenated hydrocarbons (VHHs) in an aqueous sample. The pre-concentration method consists of the following 4 main analytical steps ; 1. purging the aqueous sample, 2. trapping at adsorbent, 3. thermal desorption, and 4. retrapping on a trap column (cryofocusing). Using the optimal conditions of the step allowed us sufficient quantitative transfer of VHHs to a capillary column with narrow band width and such good chromatographic resolution with high reproducibility that we were able to successfully apply it to rainwater containing sub ppb levels of mixed VHHs which had very similar boiling points.