NIR and Raman quickly reveal heparin contamination

Near infrared (NIR) reflectance and laser Raman spectra can be used to quickly screen drug samples non-destructively and to spot contamination. The techniques may not displace the nuclear magnetic resonance spectroscopy and electrophoresis analyses required by drug regulators, but could be used as a quick first test for screening potentially contaminated drug products.

A team working at the US Food and Drug Administration, Center for Drug Evaluation and Research, in its Division of Pharmaceutical Analysis, in St. Louis, Missouri has developed a new approach to quickly screen samples of pharmaceutical products for contaminants. The team comprises John Spencer, John Kauffman, John Reepmeyer, Connie Gryniewicz, Wei Ye, Duckhee Toler, Lucinda Buhse, and Benjamin Westenberger.

Recently, there have been reports of patients receiving heparin who have suffered adverse effects to product solutions containing raw materials  originating in China, the team explains. Heparin is a highly-sulfated glycosaminoglycan, which is an injectable anticoagulant and also used for giving various research and medical devices an anticoagulant character. Pharmaceutical grade heparin is derived from mucosal tissues of pig intestine or cow lung.

Severe allergy and even deaths with certain products have been reported. Removing contaminated or suspect products from the market becomes a matter of urgency when such problems arise.

Conventionally, capillary electrophoresis and nuclear magnetic resonance (NMR) spectroscopy can be used to reveal tainted products and initial studies on samples of heparin suggested that oversulfated chondroitin sulfate (OSCS) as a contaminant was the putative cause of adverse patient reactions. The team explains that dermatan sulfate, a glycosaminoglycan (GAG) impurity, was also found in some batches of heparin. The team suggests that a rapid screen procedure is needed that can be used in the field to non-invasively test suspect samples.

Spencer and colleagues have now developed such a screening test. They used NIR and Raman to screen 69 powder samples of the anticoagulant heparin obtained from several suppliers in the US and elsewhere. The team explains that they could correlate both the NIR and Raman spectra of individual heparin API powder samples with sample compositions determined using response corrected relative peak areas of the samples' capillary electropherograms using a partial least squares regression model.

The team explains that the test NIR spectra of heparin have absorption bands at 5200 and 6900 cm^-1 and these agree with earlier studies in solution. Heparin, they add, has an irregular peak at 4730 cm^-1 and a shoulder at 6500 cm^-1 which distinguish it from dermatan sulfate (a GAG, also known as chondroitin B), while OSCS has two small peaks in the 4730 cm^-1 region and 5800 cm^-1 and a third peak at 7000 cm^-1.

With the initial data in hand, they then used 28 sample spectra to develop PLS models for the three major sample components; heparin, oversulfated chondroitin sulfate (OSCS) and glycosaminoglycans (GAGs). With these PLS models in hand, they then successfully predicted the compositions of 41 additional heparin samples.

The team points out that the success with the PLS spectroscopic approach offers a rapid and importantly non-destructive testing technology for spotting contamination of heparin samples without too involved an analytical setup. The team adds that the NIR  spectra are so heavily overlapped that no distinguishing features   between   the   ''good''   and   ''suspect'' samples are apparent from the spectra without the additional Raman correlation and their chemometrics work.

This, they say, "demonstrates the potential of spectroscopy and chemometrics for screening of processed raw materials," the team says, "These technologies are meant for screening purposes and not meant to replace either of the methods (capillary electrophoresis and NMR) currently required by USP and FDA."

"[Our] multivariate models can be used to rapidly screen new lots of bulk heparin active pharmaceutical  ingredient for the presence of OSCS and GAG contaminants," the team says.