would provide a specific assay for Cryptotime a highly sensitive assay for infecsporidium, ,ad ESI would dffer the eaditious Cryptosporidium. tional benefits of enhanced sensitivity and To their disappointment, repeated Although the mention of microorganisms reduced sample preparation. Burkhalter applications of this methodology recan conjure up images of biological weap- set out to find the endogenous phosphovealed that the unique fatty acid was, in lipid, which was previously thought to be ons or terrorist attacks, microorganisms actuality, an artifact added occasionally acylated at the sn-2 position of phosphatiare more likely to affect the average perfrom amber rubber bulbs in the extracson in food or water. The protozoan Cryp- dylethanolamine. However, parent ion tion/purification procedures. This ffndtosporidium has been particularly difficult scans revealed the presence of no signifiing was unfortunate because the identicant precursors. Neutral mass loss scan to detect with the sensitivity needed to fication oo fa nxtremely unusual fatty revealed that no phosphatidylethanolamine acid unique to species of Cryptosporidprotect human health. One of the challenges is in differentiating infectious from was present in the fraction containing ium would have allowed for the detecnon-infectious Cryptosporidium, espe- 10-OH 18:0. tion of this opporrunistic pathogen, cially when 20-30 oocysts has been such as a water distribution system's Burkhalter and co-workers eventually identified as an infectious dose. D. C. biofilms, without the prerequisite of determined mat 10-OH 18:0 did exist in White Rob Burkhalter, and co-workCryptosporidium samples, but as a sree fatty oocyst purification and identification. acid, which is extremely rare in nature. the University of Tennessee are Despite the artifactual nature of Low-energy collisionally induced dissociaworking on a mass spectrometric 10-OH 18:0, the research showed that it tion conditions for the selected reaction method for distinguishing infectious is possible to differentiate infectious and monitoring (SRM) of daughter ions of and non-infectious species. Their non-infectious Cryptosporidium parvum, 10-OH 18:0 were optimized for the produc- as well as differentiate C. parvum from search for a uniaue biomarker has tion of ions diagnostic of the site of hybeen interesting but so far unfruitful other species of Cryptosporidium and Eidroxyl substitution. It was found that under meria through hierarchical cluster analyHowever they have been able to use cluster analysis to differentiate species these low energy conditions, highly spesis of lipid patternsfrompurified oocysts. cificfragmentationprocesses were occurof Crvttos-boridium The current problem is the difficult purifiring, which provided in a much more sen- cation procedures required to isolate Earlier studies had seemed to link a Cryptosporidiumfromother waterborne novel fatty acid, 10-OH 18:0, to Crypto- sitive SRM assay because of the lesser microeukaryotes whose lipid patterns sporidium parvum. Burkhalter and dis extent of nonspecific fragmentation typical of high-energy CID studies. This reobscure those of infectious Cryptosporidco-workers had hoped to transfer the sulted in a highly sensitive and specific ium parvum. For these eeasons, efforts methodology for detection of the susfor the presence of 10-OH 18:0 in continue toward identifying unique biopected biomarker to HPLC/electrospray complex biological matrices and thus it marker patterns for Cryptosporidium and MS. Identification of the endogenous was thought to have provided for,the first other non-culturable pathogens phopholipids containing 10-OH 18:0
Going after Cryptosporidium
array detector for the simultaneous measurement of different mass ions. He has developed a miniature mass spectrometer of Mattauch-Herzog geometry, which is just 10 x 5 x 4 cm. .I measures ions up to 240 m/z, possesses a resolution of >300, and consumes only 1-2 W. Two kinds of array detectors have been developed. The first is based on an ion-electron-photon conversion process. The ion images are measured with a photodiode or a CCD array. The second approach employs 3. multianode system, which is fabricated along wiih pulsecounting electronics on a silicon chip. In addition, efforts are being made at other institutions to design mass spectrometers for cometary research. The International Rosetta Mission, sponsored by the European Space Agency and slated for launch in January 2003, is expected to deploy a spacecraft that will rendezvous with comet 46 P/Wirtanen and escort it for two more years. Hans Balsiger, Stefan Scherer, and co-workers at the University of Bern
(Switzerland), the Southwest Research Institute (Austin, TX), the Max-Planck Institut fur Aeronomie (Germany), and the University of Giessen (Germany) described a prototype reflectiontime-of-flight(RTOF) mass spectrometer that will be part of the ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) package. The package wiil also include a double-focusing mass spectrometer and a "neutral dynamics monitor". The RTOF is ~ 1 ml with a flight tath oo 2 m when ions are reflected only once. The design also incorporates a "hard mirror" that can effectively double the flight path. The hard mirror consists of three cylindrical elements and a shaped backplane which be used to remove selected mass lines by applying a positive pulse to the backplane electrode Mass resolution of up to 5700 (132Xe) has been achieved and the mass accuracy is —10 oom The RTOF is compact only 1134 x 309 x 252 mm and 10 4 kg It consumes 13 4 W in the low nower mode and 23.0 W in the full operation mode.
GOVERNMENT AND SOCIETY
Eggsacting standards A review by U.K. government scientists of techniques used to estimate veterinary drug residues, such as ionophores for preventing coccidiosis in poultry, has shown there to be no reliable way of correlating residue levels with duration or amount of medication or whether there has been any cross contamination or misuse of the drugs. Christopher Elliott and colleagues at the Veterinary Sciences Division in Belfast, a European Union drug-residues monitoring unit, say that with the current analytical methods there is no satisfactory way to determine residue levels of all of the widely used ionophore drugs in the poultry industry. "MRLs [maximum residue limits] do not exist for these drugs [the ionophores]
Analytical Chemistry News & Features, August 1, 1998 5 0 5 A
