Use of an inline dilution method to eliminate species interconversion for LC-ICP-MS based applications: focus on arsenic in urine

Abstract

Measuring arsenic in urine provides important information for clinical and epidemiological studies. While many researchers have studied ways to improve sample storage and understand why arsenic species undergo species interconversion, none have investigated inline dilution as a solution for arsenic speciation sample stability. A fast inline dilution method for AsB, DMA, MMA, As III, and As V was demonstrated in this work. Inline dilution calibrations from a single stock standard were shown to have good linearity and resulted in LODs in the single digit ppt range. Inline dilutions of 30X, 50X, and 100X resulted in 0.1 s to 1.1 s variation in retention time. Manual sample preparation resulted in poor recovery (61%) for As III over a 24 h time period, which was a direct result of As III converting to As V. Inline dilution of urine spiked with As III resulted in good recovery (101%) and reduced the species interconversion of As III to As V to $1%. Accuracy to NIST SRM 2669 (arsenic in frozen urine) was found to be within reported values for the five arsenic species tested for in this method.

Rapid automated total arsenic and arsenic speciation by inductively coupled plasma mass spectrometry

“…The LODs were determined by analyzing urine blanks ( n = 10) and applying a 3 σ criteria. 28 The LODs for these two methods are slightly higher than the previously reported method (0.3–1.7 ng L −1 ), 27 however the values are comparable or lower than the published values using similar methods which range from 3–100 ng L −1 . 25,29,30 The LODs for the one- and two-column methods are comparable, with the average LOD for the one-column method (4 ng L −1 ) slightly lower than the two-column method (7 ng L −1 ).…”

“…We previously reported the separation of AsB, DMA, MMA, As( iii ), and As( v ) utilizing ammonium phosphate buffer as the eluents. 27 This method did not provide an adequate separation when AsC was present in the sample. Additionally, ammonium phosphate buffers could compromise the analysis of phosphorous for future measurements.…”

Thioarsenite Detection and Implications for Arsenic Transport in Groundwater

“…Use of an eluent that closely matches sample pH avoids ligand-exchange reactions during column elution, facilitating more conclusive identification of chemical mechanisms that alter arsenic speciation in the native sample. Likewise, analysis at circumneutral pH helps avoid the potential for accelerated oxidation that has been observed for arsenite analysis at more alkaline pH − and that could likely influence the stability of thioarsenite species.…”

Evaluation and Specifications for In-Line Uranium Separations Using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) Detection for Trace Elemental Analysis

“…Examples of these studies have included sample preconcentration 25,26 or chemical speciation anlalysis. 27,28 While common for ICP-MS, separations directly into an ICP-OES are scarce. Chromatography is commonly integrated with ICP-MS due to its ability to continuously monitor ion counts, while ICP-OES presents slightly more challenging efforts.…”