ABSTRACT
This article provides a review of the use of modern mass spectrometry (MS) for quantitative and qualitative measurements of organic phosphorus compounds in nature. Included is a brief discussion of recent developments in large molecule mass spectrometry, focusing on time-of-flight (TOF) and ion cyclotron resonance (ICR) mass analysis techniques, as well as electrospray (ESI) and inductively coupled plasma (ICP) ionization. The use of ICP with high-resolution mass spectrometry for quantitative measurements of total phosphorus and as a detector coupled to HPLC and CE for defining organic phosphorus speciation is demonstrated using results from a study of phosphorus cycling in a treatment wetland. Qualitative identifications of individual phosphorus compounds by ultrahigh resolution Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) is demonstrated using dissolved organic phosphorus isolated from this same wetland.
ABSTRACT
In the development of test methods for solid dosage forms, manual test procedures for assay and content uniformity often precede the development of automated test procedures. Since the mode of extraction for automated test methods is often slightly different from that of the manual test method, additional validation of an automated test method is usually required. In addition to compliance with validation guidelines, developers of automated test methods are often asked to demonstrate equivalence between the manual and automated test methods. There are problems associated with using the traditional zero-difference hypothesis tests (such as the Student's t-test) for demonstrating equivalence. The use of the Westlake Interval and Schuirmann's Two One-sided test as more rigorous methods of demonstrating equivalence is discussed.
ABSTRACT
A method for the selective concentration of dissolved organic phosphorus (DOP) from complex surface water samples for the first time allows mass spectral characterization of individual DOP compounds in phosphorus-limited ecosystems. The entire dissolved organic matter (DOM) pool is first separated according to molecular weight by tangential cross-flow ultrafiltration (CFF). DOP is selectively isolated and concentrated from CFF fractions by a barium precipitation procedure. The DOP precipitate is then reconstituted in distilled water and excess barium, and other cations are removed with an ion-exchange resin. The DOP isolation/concentration step can provide up to 15-fold concentration and 300-fold concentration of high molecular weight DOP when combined with the inherent concentration provided by CFF. The procedure also removes cations and most of the background DOM, leaving DOP in a matrix suitable for electrospray ionization and mass spectral characterization. Model organic phosphate standards representative of DOP species expected in aquatic environments were used to evaluate the technique. It was then applied to a series of high molecular weight (>1000) CFF retentates isolated from sites within the Everglades Nutrient Removal (ENR) treatment wetland. The elemental compositions of several individual DOP compounds observed at different sites within the ENR were determined by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry.
