Capillary Electrophoresis Analysis of Organic Amines and Amino Acids in Saline and Acidic Samples Using the Mars Organic Analyzer

Abstract

The Mars Organic Analyzer (MOA) has enabled the sensitive detection of amino acid and amine biomarkers in laboratory standards and in a variety of field sample tests. However, the MOA is challenged when samples are extremely acidic and saline or contain polyvalent cations. Here, we have optimized the MOA analysis, sample labeling, and sample dilution buffers to handle such challenging samples more robustly. Higher ionic strength buffer systems with pK a values near pH 9 were developed to provide better buffering capacity and salt tolerance. The addition of ethylaminediaminetetraacetic acid (EDTA) ameliorates the negative effects of multivalent cations. The optimized protocol utilizes a 75 mM borate buffer (pH 9.5) for Pacific Blue labeling of amines and amino acids. After labeling, 50 mM (final concentration) EDTA is added to samples containing divalent cations to ameliorate their effects. This optimized protocol was used to successfully analyze amino acids in a saturated brine sample from Saline Valley, California, and a subcritical water extract of a highly acidic sample from the Río Tinto, Spain. This work expands the analytical capabilities of the MOA and increases its sensitivity and robustness for samples from extraterrestrial environments that may exhibit pH and salt extremes as well as metal ions.

Analysis of Carbonaceous Biomarkers with the Mars Organic Analyzer Microchip Capillary Electrophoresis System: Carboxylic Acids

“…The microdevices were prepared as previously described (Skelley and Mathies, 2003;Skelley et al, 2005Skelley et al, , 2006Skelley et al, , 2007Chiesl et al, 2009;Stockton et al, 2009aStockton et al, , 2009bStockton et al, , 2010 and will be briefly discussed here. A sacrificial layer of polysilicon was deposited on a 10 cm borofloat glass wafer.…”

“…A 3 mm deep PDMS gasket with 4 mm diameter wells placed over the reservoir holes alleviates evaporative and hydrodynamic imbalance issues by allowing for loading of sample and buffer volumes up to 50 lL. A schematic of the microdevice can be found in previous publications (Chiesl et al, 2009;Stockton et al, 2009aStockton et al, , 2009b.…”

“…The Mars Organic Analyzer (Skelley et al, 2005) was used with the previously published minor modifications to the optical subsystem that allow for more sensitive analysis of amino acids and polycyclic aromatic hydrocarbons (Chiesl et al, 2009;Stockton et al, 2009aStockton et al, , 2009b. The 404 nm laser was passed through a dichroic and focused to a 10-20 7lm spot in the channel approximately 0.6 cm from the cathode reservoir.…”

Implementation of microchip electrophoresis instrumentation for future spaceflight missions

“…One approach to remove unwanted ions would be to combine SCWE with a subsequent sublimation technique, where the extract is freeze-dried and the organics are sublimated [53]. Alternatively, the effect of ions on the analysis could be mitigated by dilution of the samples and the use of chelating agents in the separation media [54], or the inclusion of hardware in the extraction apparatus specifically for desalting of samples after extraction [52,53].…”

“…In this regard, the Mathies laboratory demonstrated that amino acids could be successfully analyzed by ME-LIF without desalting by the incorporation of ethylenediaminetetraacetic acid in the separation buffer to counteract the effects of multivalent cations [54]. However, the addition of ethylenediaminetetraacetic acid in the separation buffer for analysis of chiral compounds has not yet been investigated.…”